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Sun04052020

Last updateFri, 03 Apr 2020 5pm

Robert Victor

In the western sky at dusk, Venus in April attains its greatest brilliance of this year. Before dawn, the three bright outer planets—Mars, Jupiter and Saturn—are visible in the southeast before dawn.

In the evening: Going eastward against the background stars of Taurus at a decreasing pace, Venus loses altitude late in the month. This occurs as Venus comes around to the near side of its orbit, slowing its progress among the zodiac constellations to less than the sun’s rate of one degree per day. Venus attains peak brilliance in its crescent phase in late April.

Winter’s bright stars have moved into the western sky, most of them poised to depart in May. These include Orion’s red supergiant star Betelgeuse, now recovering from its record fade of January and February. Regulus, heart of Leo, climbs high in the south, and golden Arcturus ascends in the east to east-northeast. To Arcturus’ lower right at dusk, blue-white Spica stands at opposition to the sun on April 13 and is visible almost all night.

Binoculars give stunning nightly views! On April 1, two days before the very close pairing of Venus with third-magnitude Alcyone, or Eta Tauri, the brightest star of the Pleiades, they’re within 1.8 degrees. They’ll be less than 0.3 degrees apart on April 3. Binoculars will certainly come in handy for observing the close conjunction!

Venus will be moving east against background stars by about 0.9 degrees per day, pulling away from the Pleiades. On April 5, Venus and Alcyone are 1.9 degrees apart.

Mornings: The gap between Jupiter and Saturn is 6 degrees on April 6, closing to 5 degrees by April 28. Mars moves rapidly east against background stars, increasing its distance east of Saturn from 1 degree on April 1, to 20 degrees on May 1. Stars on April mornings are in locations similar to where we’ll find them in late August and early September at dusk: The Summer Triangle of Vega, Altair and Deneb is approaching overhead, with Arcturus in the west, Antares in the southwest, and Spica setting in the west-southwest. From April 14-16, the moon visits the three bright outer planets, while the moon goes from 6 degrees west of Jupiter to nearly 5 degrees east of Mars.

Venus-moon conjunction in the evening: At sunset on April 26, find Venus about 7 degrees to the right of the 15-percent crescent moon and a little lower. Venus is itself a crescent, 28 percent full and 37 arcseconds across—large enough to detect its shape with a steadily held pair of binoculars. The most fascinating views of Venus, both in daytime and at dusk, are yet to come, in May.

The star parties and lectures hosted by the Astronomical Society of the Desert have been canceled through at least the end of May, as an action to help prevent the spread of COVID-19. For updates on the resumption of activities, check the club’s website at www.astrorx.org. The Rancho Mirage Library’s Observatory is currently closed as well; watch www.ranchomiragelibrary.org/observatory.html for updates.

In the meantime, schedule your own sky-watching routines! Every spring, in nightly outings during the first hour after sunset—perhaps while walking your dog—you can enjoy following the seasonal departure of bright stars into the western twilight glow. In order of date, they are Rigel, Aldebaran, the Dog Star Sirius, Betelgeuse and, in 2020 before the end of May, Venus. A close conjunction of departing Venus with emerging Mercury will take place on May 21. By the start of June, of winter’s luminaries, only an arch of four bright stars remains: from left to right, Procyon, the “Twins” Pollux and Castor, and Capella.

Using binoculars or a telescope during bright twilight, follow the changing crescent phases of Venus, just after sunset in April and May, and just before sunrise in June and July.

You can also follow the moon nightly at dusk, as it waxes from a thin crescent in the west to full in the east. Then, you can switch to predawn viewing to follow the moon waning from full in the west to a thin crescent in the east.

Early risers in spring 2020 can follow the three bright outer planets in the southeast to southern sky: Bright Jupiter pauses within 5 degrees west of Saturn from late April through early June, while red, brightening Mars pulls away to their east.

Beautiful gatherings of the moon, planets and stars are illustrated In the Abrams Planetarium Sky Calendar. For subscription information and a sample copy, visit www.abramsplanetarium.org/SkyCalendar. The sample is the April 2020 issue, with its evening sky map. Please enjoy and share it with others.

Stay safe! Here’s wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. Now retired, he often collaborates with John S. French on the Sky Calendar, and enjoys providing sky-watching opportunities for a variety of groups, mostly in the California desert and in Michigan.

In the western sky after sunset, Venus in late March attains its highest position at dusk and its longest duration of visibility in a dark sky for 2020.

All three bright outer planets—Mars, Jupiter and Saturn—cluster in the southeast before dawn. Don’t miss their rare, once-in-20-years compact gathering from March 18-31. In mid-March, Mercury reaches its highest position during a poor morning twilight appearance, very low in the east-southeast. Binoculars will help you find the innermost planet well to lower left of the outer-planet threesome.

In the March evening sky, the huge Winter Hexagon of bright stars is in fine view, with Sirius, the brightest star, crossing through the south, and Capella, its second-brightest member, passing north of overhead. In clockwise order, locate Sirius, Procyon, Pollux-Castor, Capella, Aldebaran, Rigel and back to Sirius. Orion’s shoulder—red supergiant and future supernova Betelgeuse, inside the hexagon—is still uncharacteristically faint at this writing (matching the other shoulder star), but is expected to recover some of its brilliance before the Winter Hexagon departs from our view in the west in mid-May. Venus far outshines all these stars, and climbs to its highest point around the date of greatest elongation (maximum angular distance from the sun), on March 24. Telescopes show Venus’ phase, then half full. The crescent moon skips past Venus on March 27 and 28, passing widely south of the planet. Catch the Pleiades star cluster (the Seven Sisters) within 5 degrees of Venus for 11 evenings, March 29-April 8. Binoculars give stunning nightly views!

On April 1, two days before the very close pairing of Venus with third-magnitude Alcyone, or Eta Tauri, the brightest member of the Pleiades, they’re within 1.8 degrees. They’ll be less than 0.3 degrees apart on April 3, when binoculars will certainly be handy for observing the very close conjunction! Venus will be moving east against background stars by about 0.9 degrees per day, pulling away from the Pleiades. On April 5, Venus and Alcyone are 1.9 degrees apart.

In the morning sky, bright Jupiter attracts our attention to the southeast, where the three bright outer planets span 18.5 degrees on March 1, closing to 6.3 degrees at month’s end. Can you spot Mercury in the twilight glow to their lower left? Binoculars help.

Early risers will be well rewarded by the rare morning scenes depicted on the illustration from the March 2020 Sky Calendar below. Be sure to catch the compact gathering of the moon and three planets within a span of 8.3 degrees on March 18, and the same three planets spanning just 7.1 to 6.3 degrees during March 20-31, as Mars, in the foreground, passes from Jupiter toward Saturn. Watch Mars pass within 0.7 degrees of Jupiter on March 20, and 0.9 degrees of Saturn on March 31. Several morning scenes of the threesome, as well as scenes of the moon’s return to evening sky, appear in this excerpt from the March Sky Calendar.

Check the website of the Astronomical Society of the Desert at www.astrorx.org for a schedule of star parties. The primary, more-accessible location for our star parties is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 111, within four miles south of Highway 111 in Palm Desert. Our next session there will be on Saturday, March 28, from 7 to 10 p.m. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have a star party starting at dusk on Saturday, March 21. The list of star parties on the society’s website includes maps and directions for both locations. Star parties can be cancelled in poor observing weather.

Also, remember to check the Impromptu Star Parties link on the Astronomical Society’s webpage. I’ll be offering sky watches in Palm Springs at the pedestrian bridge over Tahquitz Creek at North Riverside Drive and Camino Real and at other locations. Some sessions will be held in the daytime or at dusk to observe the changing phases of Venus, and some in the predawn to follow the gathering of the three bright outer planets.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. Subscriptions are $12 per year for three printed issues mailed quarterly. The March 2020 issue of the calendar will feature the rare compact gathering of the three bright outer planets in predawn skies, and Venus ascending to its greatest height in the evening sky.

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. Now retired, he often collaborates with John S. French on the Sky Calendar, and enjoys providing sky-watching opportunities for a variety of groups, mostly in the California desert and in Michigan.

In the western evening sky, Mercury reaches one of its highest positions at dusk for 2020. In the predawn darkness of Feb. 18, the moon covers and uncovers Mars. Meanwhile, all three bright outer planets—bright Jupiter, with Mars to its upper right, and Saturn to its lower left—are gradually coming together in the southeast before dawn, until their rare, once-in-20-years compact gathering in late March!

You won’t fail to notice brilliant Venus well up in the west-southwest to west at dusk. Mercury makes an appearance to its lower right. Mercury shines at magnitude -1 on Feb. 1, fading to magnitude 0 on Feb. 13, and magnitude +1 by Feb. 17; it then dims rapidly and drops into bright twilight within a few days. Mercury lingers 24 degrees from Venus Feb. 4-11. The revolution of the planets around the sun is counterclockwise, as viewed from above the northern side of the solar system. Fast-moving Mercury and Venus are gaining on Earth and coming around from the far side to near side of the sun. This causes Mercury (but not cloud-covered Venus) to fade as the planet displays narrowing crescent phases on the near side of its orbit. Mercury appears at greatest elongation, 18 degrees from the sun, on Feb. 10.

Sirius, the “Dog Star” and brightest of the nighttime stars, twinkles vigorously in the southeast. It is the lowest member of the huge Winter Hexagon of stars of first magnitude or brighter. In clockwise order, they are Sirius, Procyon, Pollux (with fainter twin Castor just 4.5 degrees away), Capella (nearly overhead), Aldebaran, Rigel and back to Sirius. Betelgeuse is normally the brightest star inside the boundaries of the Hexagon, but something has happened to this star! At the time of this writing, Betelgeuse appears barely as bright as Bellatrix, the other shoulder of Orion. Keep an eye on Betelgeuse, comparing it to other stars of known brightness; refer to the resources posted at the end of this article.

Other bright stars in February at dusk include Deneb, the last star of the Summer Triangle to slip away in the northwest, and Regulus, heart of Leo, at opposition to the sun on Feb. 18.

Jupiter is the brightest morning “star,” with Mars to its upper right, and Saturn emerging early in February to Jupiter’s lower left. Ranking next after Jupiter in brightness are golden Arcturus, high in the southwest, and blue-white Vega, high in the east-northeast to east. Look for Spica in the southwest, far below Arcturus; Regulus, sinking in the west to west-northwest; reddish Antares, heart of the Scorpion, in the south; and the stars Altair and Deneb completing the Summer Triangle in the eastern sky. By observing the sky at dawn in February, we can get a “sneak preview” of the stars in the positions we’ll see them in at dusk in July.

For three consecutive mornings, Feb. 18-20, the waning crescent moon appears close to each of the three bright outer planets.In fact, on Feb. 18, before dawn, the moon actually occults (covers) Mars. It’s the bright leading edge of the moon that covers Mars, so an optical aid will be needed. From the Coachella Valley, Mars will disappear behind the leading bright edge of the moon at 3:36 a.m., and reappear at the moon’s unlit side at 4:30 a.m. Note the disappearance occurs very low in the sky, only 5 degrees up as seen from our valley. By the time of reappearance, the moon and Mars will be 14 degrees up the southeast. The next morning, on Feb. 19, the moon will be close to Jupiter, and on Feb. 20, close to Saturn.

As you observe these events before sunrise, imagine you are on the forward side of Spaceship Earth in our orbit around the sun. The sun is below the horizon to your left, while our spaceship is gaining on the three bright outer planets ahead of us. We’ll overtake Jupiter and Saturn within a week of each other in July, as we pass between those giant planets and the sun. They’ll appear at opposition, 180 degrees from the sun, and so when the moon appears near them in July, it will appear full. Not until October will we overtake fast-moving Mars, and see a full moon near the red planet.

There are wide pairings of the crescent moon and Venus on Feb. 26 and 27. You can also look just before sunset for Venus in daylight, 10 degrees to the upper right of the moon on Feb. 26, and 6-7 degrees to the lower right of the moon on Feb. 27.

On Friday, Feb. 7, author and columnist Dennis Mammana will present an astronomy lecture, “From Darkness Comes Light,” at the Portola Community Center, at 45480 Portola Ave., in Palm Desert. Doors open at 6:30 p.m. for refreshments, and the talk begins at 7 p.m.

Check the website of the Astronomical Society of the Desert at www.astrorx.org for more information on the lecture and a schedule of star parties.

The primary, more-accessible location for our star parties is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74, within 4 miles south of Highway 111, in Palm Desert. Our next session there will be on Saturday, Feb. 29, from 6 to 9 p.m.Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have a star party starting at dusk on Saturday, Feb. 22.The list of star parties on the society’s website includes maps and directions for both locations. Star parties can be cancelled in poor observing weather.

Also, remember to check the Impromptu Star Parties link on the Astronomical Society’s webpage. I’ll be offering sky watches in Palm Springs at the pedestrian bridge over Tahquitz Creek at North Riverside Drive and Camino Real, and at other locations. Some sessions be held in the daytime or at dusk to observe the changing phases of Venus, and some in the predawn to follow the gathering of the three bright outer planets.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly. The March 2020 issue of the calendar will feature the rare compact gathering of the three bright outer planets in predawn skies, and Venus ascending to its greatest height in the evening sky.

Wishing you clear skies!

For more on Betelgeuse:

http://stars.astro.illinois.edu/sow/betelgeuse.html

https://www.nytimes.com/interactive/2020/01/09/science/betelgeuse-supernova-fading.html

https://www.skyandtelescope.com/observing/fainting-betelgeuse/

https://www.aavso.org/sites/default/files/10startutorial-2013.pdf

https://www.aavso.org/aavso-alert-notice-690

https://www.aavso.org/

(Enter “alf ori” into the “Pick a Star” box, then select “Plot a light curve” or “Check recent observations.”)

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. Now retired, he often collaborates with John S. French on the Sky Calendar, and enjoys providing sky watching opportunities for a variety of groups, mostly in the California desert and in Michigan. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University. He remains active in research and public outreach in astronomy.Dr. Jeffrey L. Hunt, a retired planetarium director now living in the Chicago area, has taught astronomy and sky watching to all ages. He studied astronomy education at Abrams Planetarium at Michigan State University. Jeff provided the graphs of planet rising and setting times (below); writes an astronomy blog at jeffreylhunt.wordpress.com; and can be followed on Twitter at @jeff_hunt.

Venus climbs higher above the setting sun week by week, and late in January sets more than three hours after sunset. Mercury, after passing the far side of the sun on Jan. 10, emerges into the west-southwest evening twilight sky to the lower right of Venus by the last week of month.

Mars, very slowly brightening, appears in the southeast morning sky. Jupiter emerges into the southeast morning sky to the lower left of Mars by mid-January, followed by Saturn in early February.

By modeling the solar system on orbit charts, or—here’s a weird party idea—asking friends to act out the motions of the planets, you can see why, when an outer planet such as Mars, Jupiter or Saturn is behind the sun, it is transitioning from the evening sky to the morning sky; and why, when either inner planet, Mercury or Venus, is behind the sun, it is transitioning from morning to evening visibility. Each planet moves at a faster angular speed around the sun than any planet farther out, and the direction of rotation of the Earth on its axis is in the same sense as the revolution of the planets around the sun, i.e., counterclockwise as seen from “above,” or north of the solar system.

Search online for: “Professor Zlata! You’re just in time to be the planet Neptune!” I used to have students do this in my astronomy classes long before I ever saw the cartoon.

On evenings in January 2020, Venus climbs ever higher in a dark sky. As Venus advances 1.2 degrees per day through the zodiac compared to the sun’s 1.0 degrees, watch it pass background stars in Capricornus and Aquarius on Jan. 6-8, Jan. 21-24, and Jan. 27. Mercury emerges to the lower right of Venus in the last week of the month (30 degrees on Jan. 23, to 26 degrees on Jan. 31), and will climb highest in evening twilight around Feb. 10, when it will be 24 degrees from Venus.

In second week of January, the “Twin” stars Castor and Pollux in Gemini are at opposition to the sun and are visible all night: Low in the east-northeast at dusk, high in the south in middle of the night, and low in the west-northwest at dawn.

The moon in the morning sky: On Dec. 27, Jupiter was in conjunction on the far side of the sun, and by mid-January, it will emerge into the southeast morning sky, to the lower left of Mars and Antares. The waning moon appears in January’s morning sky, passing near Regulus on Jan. 13, Spica on Jan. 17, and Mars and Antares on Jan. 20; it appears to the upper right of Jupiter on Jan. 22.

After the new moon on Jan. 24, the moon returns to the evening sky. On Jan. 25, just a half-hour after sunset, you’ll need very clear skies to see the young, very thin crescent moon, about 1 percent full and just 3 or 4 degrees up in the west-southwest. Can you spot Mercury within 3 degrees to the moon’s lower right? Binoculars will give the best view of the delicate crescent moon with Mercury in the same field. Mercury will have just emerged from its Jan. 10 superior conjunction on the far side of the sun, and now starts its best evening appearance of the year. It will get easier to see, as Mercury gets higher and sets later each evening until the second week of February. On Jan. 27 and 28 at dusk, Venus appears 6 or 7 degrees from the lunar crescent.

After Jan. 25, the waxing moon climbs higher nightly. On Jan. 26, the 5 percent crescent appears 13 degrees to the upper left of Mercury and 16 degrees to the lower right of Venus. On Monday, Jan. 27, at dusk, the 9 percent crescent moon appears 6 degrees to the lower left of Venus. That day, find the moon about 30 degrees up in the southwest shortly before sunset, and try to spot Venus in the daytime, by looking 6 degrees to the upper right of the lunar crescent. Use a telescope for a closeup of Venus, which displays a tiny gibbous disk 15 arcseconds (1/240 of a degree) across, and 75 percent illuminated. In the coming months, Venus will be ever more fascinating to watch as it comes around to the near side of its orbit; looms ever larger in apparent size; and becomes backlighted by the sun. By late in March, as Venus stands high in the western sky, 46 degrees from the sun, it will be half illuminated, and by late in April, Venus will reach greatest brilliance, while appearing as a crescent, about one-quarter full.

The year begins with Mars as our only morning planet. On Jan. 1, we find Mars at magnitude +1.6 in the southeast, about 12 degrees to the upper right of brighter first-magnitude Antares (whose name, from Greek, ant + Ares, means rival of or opponent to Mars). The two red objects appear no more than 10 degrees apart Jan. 5-30, and no more than 5 degrees Jan. 16-20. They’re closest, within 4.8 degrees, as Mars passes north of the star on Jan. 18. Enjoy them in the same field of view of binoculars for several mornings! Watch for Jupiter emerging to the lower left of Mars in mid-January, and Saturn to the lower left of Jupiter by early February. Antares wins its ongoing brightness contest with Mars for now, but during March, Mars begins to outshine the star, and there’ll be a rare compact gathering of all three bright outer planets late that month. Earth closes in on the red planet until early October, so watch it brighten until then, to magnitude -2.6, outshining Jupiter!

How often does Mars pass Antares in our sky? If we were located at the sun, the answer would be every 687 days, or about every 22.6 months, the sidereal period of revolution of Mars around the sun. But as seen from our moving Earth, conjunctions of Mars-Antares do not occur at equal intervals. After Jan. 18, 2020, the next will occur low in the morning sky on Dec. 27, 2021, when Mars will pass 4.5 degrees north of the star. On the next two occasions, on Dec. 8, 2023, and Nov. 18, 2025, Mars and Antares will appear too close to the sun to be seen from Earth. After those, the next visible conjunction of Mars-Antares will occur very low in evening sky on Oct. 29, 2027 (3.7 degrees apart). The next two, also in the evening, will be on Oct. 7, 2029 (3.3 degrees) and Sept. 10, 2031 (2.5 degrees). Then the Mars-Antares pairings shift back to mornings, on Feb. 25, 2033 (5.3 degrees) and Jan. 27, 2035 (4.9 degrees, similar to this year’s).

Saturn will be in conjunction with the sun on Jan. 13 and will follow Jupiter into the morning sky by early February. Then all three bright outer planets will be visible in morning sky, in a gathering that will become ever more compact until Mars passes the two giant planets late in March 2020.

For a preview of sky events through August 2020, with monthly all-sky charts for dusk and dawn, and graphs of planet rising and setting times, visit the Sky Calendar extra content page at www.abramsplanetarium.org/msta.

Check the website of the Astronomical Society of the Desert at www.astrorx.org for dates and times of our evening star parties.Our primary, more-accessible location is at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, within 4 miles south of Highway 111 in Palm Desert). Our next session there will be on Saturday, Jan. 18, from 5 to 8 p.m. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have a star party starting at dusk on Saturday, Jan. 25.

Remember to check the Impromptu Star Parties link on the Astronomical Society’s webpage. I’ll be offering sky watches in Palm Springs at the pedestrian bridge over Tahquitz Creek at North Riverside Drive and Camino Real, and at other locations.

On Friday, Jan. 24, I will present a preview of sky events in 2020, including the year’s rare and beautiful planetary gatherings. The event will be at the Portola Community Center, 45480 Portola Ave., in Palm Desert. Doors open at 6:30 p.m. for refreshments, and the talk begins at 7 p.m.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly. The March 2020 issue of the calendar will feature the rare compact gathering of the three bright outer planets in predawn skies, and Venus ascending to its greatest height in the evening sky.

Wishing you an abundance of clear skies in 2020!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. Now retired, he often collaborates with John S. French on the Sky Calendar, and enjoys providing sky watching opportunities for a variety of groups. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

Venus becomes ever more prominent in the evening, while Jupiter, and then Saturn, sink into the southwest twilight glow in December. Mars, slowly brightening, appears in the southeast morning sky, with bright Mercury below it in the first half of the month.

Do not miss Venus and Saturn within 5 degrees Dec. 7-14 (see right), with their closest pairing 1.8 degrees apart on Dec. 10; and the spectacular Venus-moon conjunction on Dec. 28.

Three planets span 18 degrees in the southwest at dusk in early December. On Dec. 1, find Venus, magnitude -3.9, with Jupiter, magnitude -1.8, just 8 degrees to the lower right, and Saturn, magnitude +0.6, 11 degrees to Venus’ upper left. Venus is now on the far side of its orbit, with its light taking 12 minutes to reach us, compared to the sun’s eight minutes. Light reflected from Jupiter and Saturn takes 51 and 90 minutes, respectively, to travel to Earth on Dec. 1.

As stars appear at dusk, find the Summer Triangle of Vega, Altair and Deneb dropping downward from high in the west; Fomalhaut, mouth of the Southern Fish, crossing through south; Capella, the mother goat star, ascending in the northeast; and Aldebaran, eye of Taurus, climbing in the east-northeast to east. In twilight before month’s end, Orion’s bright stars Rigel and Betelgeuse, and his three-star belt midway between them, appear in the east, followed by Gemini’s twin stars, Castor and Pollux, rising farther north along the horizon.

Note the first-magnitude star Aldebaran, eye of Taurus, low in the east at dusk on Dec. 1. Visualize: As Earth passes between Aldebaran and sun, the star is at opposition and up all night. The revolution of Earth and other planets around the sun is counterclockwise, from the viewpoint of an observer above the north side of our solar system. So Earth on Dec. 1 is moving directly away from a point 90 degrees east of the sun and 90 degrees west of Aldebaran; that’s 2 degrees west of the third-magnitude star Lambda in Aquarius, in the southern sky at nightfall. Inner planets move faster, so Venus, now on the far side of its orbit and gaining on us, continues to move farther out from last August’s place on far side of the sun, until reaching greatest elongation, 46 degrees east of the sun, on March 24, 2020. Venus will overtake us 10 weeks later, when it passes inferior conjunction, nearly between the Earth and the sun, on June 3.

We’re leaving Jupiter and Saturn behind. Earth’s faster revolution around the sun will cause Jupiter to pass behind the sun on Dec. 27, and Saturn to do so on Jan. 13. During this month, before these solar conjunctions, when will you last spot Jupiter low in the southwest at dusk? When will you last see Saturn? Pick a spot where nearby mountains won’t block your view. Using binoculars can help you delay these planets’ departures by a few days.

In morning sky, on Dec. 2, Earth is heading toward Leo, 10 degrees east of Regulus. Speedy Mercury, a few days past greatest elongation on Nov. 28, is leaving us behind and heading toward superior conjunction on the far side of the sun, on Jan. 10. When will you last see Mercury before then? Mars begins December at faint magnitude +1.7. We’re gaining on the red planet, so watch it brighten until its closest approach and opposition in October 2020, when it will gleam at magnitude -2.6.

Follow the moon and planets: The earliest sunsets of the year in December provide a convenient opportunity for families to enjoy the night sky, and this year, the planets provide much to see. In the southwest, the brightest planet, Venus, is easy to spot by half an hour after sunset. In early December, find bright Jupiter to Venus’ lower right, and Saturn to Venus’ upper left. In December’s first week, Jupiter and Saturn are 18 degrees apart, with brilliant Venus between them, while the waxing moon moves farther from the planets nightly. Each evening in early December, Venus moves farther from Jupiter and closer to Saturn. On Dec. 2, foreground Venus appears nearly midway between the distant giants. On Dec. 3, the moon reaches first-quarter phase, when it appears half-full. On the evenings of Dec. 10 and 11, Venus will pass less than 2 degrees to the lower left of Saturn. Can you still spot Jupiter those evenings, before it sinks into even brighter twilight? Find Jupiter 17 degrees to the lower right of the Venus-Saturn pair on Dec. 10.

By then, the moon, shifting its place eastward by an average of 13 degrees per day against background stars, has moved into the constellation Taurus, the Bull. On Tuesday, Dec. 10, note the first-magnitude star Aldebaran, eye of the Bull and follower of the Pleiades, to the lower left of the moon. On the next evening, find Aldebaran to the upper right of the full moon. Continue to follow the moon for several more evenings after Dec. 11—if you’re OK with staying up later each night.

Alternatively, early risers can shift their moon-watching time to mornings, one hour before sunrise. At that time on Dec. 11, the moon and Aldebaran are within 3 degrees and about to set in the west-northwest, while Orion is setting in west, and Sirius, the brightest star, is low in the west-southwest. Mercury, just risen in the east-southeast, is in the head of Scorpius on the morning of Dec. 11, while the moon is just above the head of Taurus—opposite to Scorpius in the zodiac, the belt of constellations where the sun, moon and planets are always found. Look in the southeast for faint Mars, 18 degrees to the upper right of Mercury on Dec. 11, and for a first magnitude star, Spica, nearly 21 degrees to the upper right of Mars. Spica is in Virgo, another zodiac constellation. Note that Mercury, Mars and Spica are in a nearly straight line.

Mornings the next two weeks, watch the waning moon pass several bright stars and planets in the zodiacal band: Pollux and Castor of Gemini on Dec. 14; Regulus, heart of Leo, on Dec. 17; Spica in Virgo on Dec. 20 and 21; Mars in Libra on Dec. 22 and 23; and Antares in Scorpius on Dec. 24. By then, Mercury has moved closer to the sun and may be too difficult to observe in bright twilight.

The new moon is invisible as it passes the sun late on Christmas Day. At dusk on Dec. 27, the young crescent can be seen low in the southwest to the lower right of Venus. Using binoculars, can you spot Saturn within 7 degrees to the lower right of the moon?

Whatever you plan for Saturday, Dec. 28, be sure to include time for views of the southwest sky at dusk! At sunset, Venus will be within 2 degrees above and slightly to the right of the moon. Can you spot Venus before sunset? By 40 minutes after sunset, the view of Venus just to the upper right of the crescent moon will be spectacular! Keep watch as the moon and Venus sink toward the horizon. They’ll be little more than one degree apart as they set.

For a preview of sky events through August 2020, with monthly all-sky charts for dusk and dawn, visit the Sky Calendar extra content page at www.abramsplanetarium.org/msta.

Check the website of the Astronomical Society of the Desert at www.astrorx.org, and come to our free evening star parties, offered monthly at two locations.Our primary, more accessible venue is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74, within four miles south of Highway 111, in Palm Desert. Our next session there will be on Saturday, Dec. 21, from 5 to 8 p.m.Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will next host a session on Saturday, Dec. 28, starting at dusk.

At various locations, some members of the Astronomical Society of the Desert will host observing sessions for special events, including gatherings of moon and planets. These might be announced on short notice, so periodically check the link to Impromptu Star Party Dates, on the society’s website.

You can also pre-register for one of the Stargazing Parties offered several times each month at the Rancho Mirage Library Observatory. Visit www.ranchomiragelibrary.org/observatory.html; click on Stargazing Parties, then sign up for their eNewsletter to receive registration information. If you go farther afield, check out the Sky’s the Limit Observatory and Nature Center in Twentynine Palms, at www.skysthelimit29.org.

Wishing you clear skies!

Robert C. Victor was staff astronomer at Abrams Planetarium at Michigan State University. Now retired, he often collaborates in producing new issues of the Sky Calendar he originated in 1968, and enjoys providing sky watching opportunities for a variety of groups. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

The sky’s highlights in November include Mars and Spica forming a colorful pair before dawn on Nov. 10. Mercury crosses the sun Nov. 11 to join Spica and Mars a week later. Venus and Jupiter form a brilliant pair at dusk Nov. 23-24. The moon passes three bright evening planets Nov. 27-29.

Our evening twilight chart for November shows Venus higher each evening at the same stage of twilight, while Jupiter and Saturn, dragged westward along with the starry background, appear lower. The Abrams Planetarium Sky Calendar highlights the resulting spectacular gatherings of Nov. 24, Nov. 28 and Dec. 10 involving these planets.

Planets at dusk: Begin looking low in the southwest about a half-hour after sunset to catch the two brightest planets, Venus (magnitude -3.9), and Jupiter (-1.9, only one-sixth as bright). They are 20 degrees apart on Nov. 4; 10 degrees apart on Nov. 14; and within 5 degrees, fitting within a binocular field, Nov. 19-28. Don’t miss this spectacular pair at its closest, 1.5 degrees apart, on Nov. 23 and 24.

Saturn, of magnitude +0.6, one-tenth as bright as Jupiter, is 22 degrees to the upper left of Jupiter on Nov. 1; 19 degrees to the upper left of the Venus-Jupiter pair on Nov. 24; and 12 degrees to the upper left of Venus on Nov. 30. Venus will pass 1.8 degrees from Saturn on Dec. 10; by then, Jupiter will be almost gone.

The first, young crescent moon of a new cycle appears within 6 degrees to the lower right of Jupiter on Nov. 27. Don’t miss the crescent moon within 3 degrees to the upper left of Venus on Thanksgiving, Nov. 28, and even closer to Saturn on the next evening.

Mornings: About one hour before sunrise, enjoy dim red Mars (magnitude +1.8) and blue Spica (+1.0), low in the east-southeast within a five-degree binocular field Nov. 4-16. They’ll appear closest on Nov. 10, as Mars passes 2.8 degrees north (to the upper left) of Spica. The next two Mars-Spica pairings, in 2021 and 2023, will be lost in the glare of the sun. Their next visible pairing after this one: They’ll be 2.2 degrees apart on Sept. 13, 2025.

Mercury transits across the face of the sun on Nov. 11. The disk of Mercury is tiny, only 10 arcseconds across, little more than 1/200th of the sun’s diameter. Use a telescope magnifying 50x to 100x with a solar filter securely installed over its front end, or use equipment to project an image of the sun on a white screen or paper 1-2 feet from the eyepiece. Mercury will appear as a tiny black dot already near the center of the solar disk at 7:20 a.m., just more than an hour after sunrise in the Coachella Valley. The leading edge of Mercury’s disk reaches the edge of the sun near 10:03 a.m.; egress from the solar disk is complete 1.7 minutes later. The next transit of Mercury visible in U.S. won’t be until May 7, 2049, so you might want to catch this one!

In the days after the transit, Mercury rises before sunrise, but is in a thin crescent phase, too faint to be seen for several mornings. Mercury brightens quickly, reaching magnitude +0.7 by Nov. 19, within 12 degrees to the lower left of Mars, and -0.1 by Nov. 22, within 10 degrees to the lower left of Mars. Once Mercury emerges from the solar glare, follow the striking lineup of Spica, Mars and Mercury. Watch the waning, old crescent moon slide downward past Spica, Mars and Mercury, in order, Nov. 23-25, while Mercury pauses 9.5 degrees to Mars’ lower left. On Nov. 28, only 17 days after its transit, Mercury shines at magnitude -0.6 and stands at greatest elongation, 20 degrees from the sun.

The morning twilight chart for November below shows Spica and Mars getting higher daily, while Mercury ascends to its highest position before month’s end. The panel of Sky Calendar illustrations also shows Mars passing Jupiter and Saturn in late March 2020, after the giant planets have emerged from behind the sun to join Mars in the morning sky. For a summary of planetary visibility in 2019-20, visit www.abramsplanetarium.org/msta.

Check the website of the Astronomical Society of the Desert at www.astrorx.org and come to our free evening star parties offered monthly at two locations. Our primary, more-accessible venue is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, within 4 miles south of Highway 111 in Palm Desert). Our next session there will be on Saturday, Nov. 2, from 6-9 p.m. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will next host sessions on Saturday, Nov. 23, starting at dusk. At various locations, some members will host observing sessions for special events, including the transit of Mercury and gatherings of planets. These might be announced on short notice, so periodically check the link to Impromptu Star Party Dates. You can also pre-register for one of the stargazing parties offered several times each month at the Rancho Mirage Library Observatory by visiting www.ranchomiragelibrary.org/observatory.html. Click on Stargazing Parties, then sign up for their eNewsletter to receive registration information.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

As October both begins and ends, the moon will be sweeping through an evening lineup of four planets.

On October evenings, bright Jupiter is in the south-southwest to southwest at dusk, with Saturn to its left in the south to south-southwest; both remain outstanding for telescopic viewing, Jupiter with its cloud belts and four bright moons, and Saturn with its rings now tipped 25 degrees from edgewise. These giant planets appear 26 degrees apart on the sky’s dome on Oct. 1, narrowing to 22 degrees apart by Oct. 31. Follow their eastward motions against background stars, until the seasonal westward drift of the constellations drags both slow-moving planets to the southwest horizon before year’s end. Note reddish twinkling Antares, heart of Scorpius, 10 to 14 degrees to the lower right of Jupiter during October. Watch Jupiter pass 2.1 degrees north of a third-magnitude star on Oct. 22.

Look early in the evening twilight to catch Venus; binoculars are indispensable for nearby Mercury. From the Coachella Valley, Venus sets only 37 minutes after sunset on Oct. 1, improving to 64 minutes by month’s end. Mercury, near magnitude 0 almost all month, sets a maximum of 60 minutes after the sun Oct. 18-24; reaches greatest elongation, 25 degrees to the upper left of the sun on the 19th; and appears highest in twilight for a few days around then. But this is the year’s poorest evening apparition of Mercury, because the zodiac belt where the planets are found makes its shallowest angle with the evening horizon when the southernmost zodiac constellation Sagittarius is in southern sky. Using binoculars, find Mercury to the upper left of Venus during the first three weeks—by 7 degrees Oct. 2-3; 8 degrees Oct. 8-16; and back to 7 degrees Oct. 20-21. On Oct. 23, Mercury is 6 degrees to the upper left of Venus. Next, Mercury passes left of Venus, by 5.2 degrees on Oct. 25, and 4.6 degrees on Oct. 26. Then Mercury appears to Venus’ lower left, by 4 degrees on the 27th, and 3.4 degrees on the 28th. On Oct. 30, Mercury passes within 2.6 degrees south of Venus, but has begun its rapid fade.

Follow the moon at dusk through Oct. 13, and again Oct. 27-Nov. 12. On Oct. 3, find bright Jupiter within 3 degrees to the lower right of the moon. On Oct. 4, the fat (44 percent) crescent moon is 15 degrees to the upper left of Jupiter and 10 degrees to the lower right of Saturn. On Oct. 5, the moon, 54 percent full, is just past its first-quarter phase, when it’s half full and 90 degrees—a quarter of the way around the sky—from the sun.

On Oct. 13, watch the full moon rise some 20-25 minutes after sunset, just north of due east. As you looked daily in evening twilight through Oct. 13, the moon took two weeks to travel through a half-dozen zodiac constellations, from western horizon to eastern horizon, passing four planets along the way. In the first five evenings its next time around, Oct. 29-Nov. 2, the moon will pass the same four planets.

Other bright stellar markers not in the zodiac are Fomalhaut, mouth of the Southern Fish, climbing in the southeast, and golden Arcturus, the “Bear-watcher” star, sinking in the west to west-northwest.

By Oct. 16, moonrise is late enough to allow at least a brief interval of dark skies unaffected by moonlight. This “window” of darkness lasts longer each evening as the moon rises later. If you’re in a dark place, enjoy the Milky Way passing through the Summer Triangle of Vega, Altair and Deneb overhead, and the Andromeda Galaxy above the curved chain of stars starting at one corner of the Great Square of Pegasus in the east.

Follow the moon at dawn from when it is full, low in the west on Oct. 13, through last quarter (half full and 90 degrees west of the sun) on Oct. 21, to a thin crescent, low and south of east, on Oct. 26. The brightest star in October’s morning twilight is Sirius, in the southern sky, as dawn brightens. Confirm by noting that the three-star belt of Orion, with stars bluish Rigel marking his foot and reddish Betelgeuse his shoulder, points directly to Sirius. Extend the belt in the opposite direction, and you’ll pass near Aldebaran, eye of Taurus the Bull, and farther to the Pleiades or Seven Sisters star cluster, a wonderful target for binoculars.

Four days after it’s full and low in the west on Oct. 13, the moon is within 6 degrees to the lower right of Aldebaran on Oct. 17. For the next three mornings, Oct. 18-20, the waning gibbous moon moves through the huge Winter Hexagon. Next, on Oct. 21, the last-quarter moon, half full, is 7 degrees southeast of Pollux, and in line with the “Twin” stars, Castor and Pollux of Gemini. Our Spaceship Earth is heading in the direction of the half-lit moon in our orbit around the sun. If the moon stood still, it would take us only about 3 1/2 hours to reach it.

Our view of the peak of the Orionid meteor shower, in the predawn hours of Oct. 22, is affected by moonlight. On Oct. 23, the crescent moon will pass 4 degrees north of Regulus, heart of Leo, the Lion. In just three more mornings, on Oct. 26, look for the last easy old crescent moon, 4 percent full, just south of east, with Mars 5 degrees to its lower right. The dim red planet is now at magnitude +1.8, as faint as it ever gets. In just less than a year, in October 2020, the Earth will pass between Mars and the sun, and it will appear at opposition, and shine at magnitude -2.7, some 60 times brighter than now. At the end of October, Spica will be emerging out of the morning twilight glow, 7 degrees below Mars.

Notice the star Arcturus rising on the morning twilight chart. Arcturus is equally visible low in the west-northwest at dusk on Oct. 29 as it is in the east-northeast at dawn on Oct. 30. At this time of year, Arcturus leads the procession of stars and constellations through the night, and brings up the rear.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. The calendar illustrates many of the present and future events described above. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly. For a preview of evening and morning planet gatherings through August 2020, visit the Sky Calendar Extra Content Page at www.abramsplanetarium.org/msta.

Would you enjoy telescopic views of Jupiter, Saturn and an assortment of deep sky objects? Check the website of the Astronomical Society of the Desert at www.astrorx.org and come to our free evening star parties offered monthly at two locations.Our primary, more accessible venue is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74, within four miles south of Highway 111 in Palm Desert. Our next sessions there will be on Saturday, Oct. 5, from 7 to 10 p.m., and on Saturday, Nov. 2, from 6 to 9 p.m. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will next host a session on Saturday, Oct. 26, starting at dusk.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

From Sagittarius to Gemini and back, the moon swings! And the crescent rocks!

Enjoy watching moonrises? The harvest moon on Friday the 13th is the first of a half-dozen moonrises in a row taking place in the early evening, through Sept. 18. Meanwhile, Jupiter shines steady and brightest at dusk, and Sirius, the “Dog Star,” twinkles brightest at dawn.

Overnight on Sept. 22—actually at 12:50 a.m., Monday, Sept. 23—the sun is directly over Earth’s equator, marking the start of autumn for residents of the Northern Hemisphere. On the date of an equinox, the sun rises in the east, and sets in the west 12 hours later. (Well, this is not precisely true, because of the way sunrise and sunset are defined—when the top of the solar disk, rather than its center, appears on an ideal, flat horizon; refraction by our atmosphere uplifts the sun’s disk and lengthens the day by several minutes.)

The moon travels around the Earth in an orbit inclined 5 degrees to the Earth’s orbital plane, traveling through the same belt of the zodiac and returning to the same stars after only 27.3 days, the sidereal period of the revolution of the moon. So in less than four weeks, the moon’s rising and setting places on the horizon and height at mid-path range from southern to northern extremes and back.

On Saturday, Sept. 7, the moon “rides low,” reaching the southernmost part of its 27.3-day trip around the zodiac, in the constellation Sagittarius, the Archer. From Palm Springs, the moon rises nearly 28 degrees south of east at 3:10 p.m. It reaches its highest point in south at 8:16 p.m., only 33 degrees above the horizon.

As the moon passes south on Sept. 7, look for Saturn 5 degrees to its left; Jupiter 23 degrees to the moon’s right; and the third-magnitude star Kaus Borealis, northern star of the Archer’s bow, within 3 degrees to Luna’s lower right. September’s southernmost moon sets nearly 28 degrees south of west later that night.

Might we call the lunar event of Sept. 7-8 a “Lunastice”? There are two solstices each year, when the “sun stands still” directly over the Tropic of Capricorn and the Tropic of Cancer at the southern and northern extremes of the sun’s annual journey around the zodiac. But the moon takes just 27.3 days to make the same circuit. That’s about two days less than the moon’s 29.5-day cycle of phases, so each successive time the moon “rides low” (or “rides high,” or returns to the same star background) occurs 2.2 days earlier in its phase cycle. Since the moon makes just more than 13 trips around the zodiac annually, there are 26 or 27 “Lunastices” each year, spaced at intervals averaging just less than two weeks.

After Sept. 7, the moon rises farther north, getting later each day. By Sept. 11, the moon rises 19 degrees south of east at 6:04 p.m., some 55 minutes before sunset, so it’s still possible from some places in the Coachella Valley to view sun and moon simultaneously. On Sept. 12, the moon rises 15 degrees south of east at 6:37 p.m., just 20 minutes before sunset. For the next five nights through Sept. 17, moonrise occurs only about a half-hour later on each successive night. Short daily delays in the time of moonrise, significantly less than the long-term average of 50 minutes per day, always happen around the full moon near the beginning or autumn, and is called the Harvest Moon Effect.On Friday, Sept. 13, the full moon rises 10 degrees south of east at 7:07 p.m., just 11 minutes after sunset.

This month’s full moon also happens to be the most distant of this year. It’s also the faintest of all the full moons (except for those eclipsed by Earth’s shadow)—not only because of its distance, but also because it passes 5 degrees south of the point opposite the sun and reflects less of its light back toward Earth. (Look up “opposition effect.”) By Sept. 15, the moon rises about one degree north of east at 8:05 p.m., and by the 17th, 12 degrees north of east at 9:04 p.m. September’s northernmost moonrises occur on Saturday evening, Sept. 21, at 11:44 p.m., and on the next night, Sunday, Sept. 22—actually Monday morning, Sept. 23, at 12:40 a.m., some 27 degrees north of east. On both occasions, the moon “rides high” in Gemini, passing within 12 degrees south of overhead on Sept. 22 at 7:04 a.m., and on Sept. 23 at 8:01 a.m., setting 7 hours and 20 minutes later.

Follow the moon at dusk through Sept. 14, and again Sept. 29-Oct. 13. Follow the moon at dawn Sept. 13-27. Note the “tipped bowl” orientation of the waxing lunar crescents in the western sky at dusk through Sept. 3 and Sept. 29-Oct. 2, preceding the nearly first-quarter (half) moons found low in the southern sky around sunset on Sept. 5 and on Oct. 4 and 5. Note the “upright bowl” waning lunar crescents in the eastern sky at dawn Sept. 25-27, following the nearly half-moon close to last-quarter phase found high in the southern sky around sunrise on Sept. 21 and 22. Best views of zodiacal light (reflected off comet and asteroid dust in the plane of the solar system) can be had from dark places free of light pollution just before start of morning twilight, 90 minutes before sunrise, Sept. 27-Oct. 11. All these observations are related!

The only planets easy for the unaided eye to see in September are both conveniently placed in the southern sky in the early evening: Bright Jupiter, in the south-southwest at dusk; and Saturn, in the south-southeast to south, 29 to 26 degrees east (left) of Jupiter. Telescopes show Jupiter’s disk, now just over 0.01 degrees in apparent diameter, usually with two dark equatorial belts, and the four bright Galilean satellites. Since their orbits lie nearly in plane of Jupiter’s equator, and Jupiter’s south pole is tipped more than 2 degrees toward Earth for rest of 2019, it’s often possible to mentally work out whether a satellite of Jupiter is on the near or far side of its orbit. Currently, if a moon is displaced north of a line through Jupiter’s center parallel to its equator, then that moon must be on the near side of Jupiter. If displaced south, it must be on far side of its orbit. Jupiter’s equator will appear edge-on in early 2021, and so, nearly, will the orbits of the satellites, making them appear in a straight line.

Saturn’s rings span slightly wider than Jupiter’s apparent size. Saturn’s north pole is now tipped toward Earth by more than 25 degrees, giving us our best view of the rings until 2030, when the south pole will be tipped toward us by a similar angle. Before then, the rings will be edgewise to the Earth and sun during spring 2025. Maximum tilt of rings, nearly 27 degrees with north face visible, occurred in 2017; the maximum with south face visible will occur in 2032.

There are no naked-eye planets in September’s morning sky, but the brightest star visible is Sirius, in the southeast to east-southeast as dawn brightens. Confirm by noting that the three-star belt of Orion—between bluish Rigel marking his foot and reddish Betelgeuse his shoulder—points directly to Sirius.

For a preview of the wonderful gatherings of the moon and planets in 2019-2020, visit www.abramsplanetarium.org/msta. Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. The calendar illustrates many of the present and future events described above. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly.

Check the website of the Astronomical Society of the Desert at www.astrorx.org for dates and times of our evening star parties at two locations: Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have its next monthly sessions starting at dusk on Saturday, Aug. 31 and Sept. 28. Monthly sessions resume Saturday, Oct. 5, at our primary, more accessible location, the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, within 4 miles south of Highway 111 in Palm Desert).

But don’t wait until then! You can pre-register for one of the Stargazing Parties offered several times each month at the Rancho Mirage Library Observatory. Visit www.ranchomiragelibrary.org/observatory.html; click on Stargazing Parties, then sign up for their eNewsletter to receive registration information. If you go farther afield, check out the Sky’s the Limit Observatory and Nature Center in Twentynine Palms, at www.skysthelimit29.org.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

Evenings this month feature the gas-giant planets, Jupiter and Saturn, and on dark moonless nights, the Milky Way. Predawn skies include the bright stars we’ll meet again on winter evenings—and a brief visit by our solar system’s smallest planet, Mercury.

In the evening, bright Jupiter gleams in the south to south-southwest at dusk, while Saturn is in the southeast to south-southeast, 31 to 29 degrees east (to the left) of Jupiter. Note Antares, heart of Scorpius, twinkling to Jupiter’s lower right. Jupiter lingers 7 degrees from this red supergiant star from mid-July through first week of September; their least separation of 6.7 degrees occurs Aug. 8-15 as Jupiter ends retrograde on Aug. 11.

Follow the moon at dusk Aug. 2-15. On Aug. 2, the thin crescent moon is easy to see, though very low, a little north of due west. Don’t miss a striking pairing of the moon and Jupiter, within 3 degrees, at dusk on Aug. 9, and the moon and Saturn, just 3 degrees apart on Aug. 11. By the evening of Aug. 12, the moon has moved 9 degrees east of Saturn. On Aug. 15, the moon, past full, is rising in the east-southeast. The moon returns to the evening sky as a crescent low in the west on Aug. 31.

The year’s best Milky Way viewing after evening twilight occurs through Aug. 2, and Aug. 20-Sept. 1. Go to a dark place to enjoy these with the unaided eye and binoculars: the Cygnus Star Cloud, along axis of the Northern Cross or neck of the Swan, within the Summer Triangle; the Great Sagittarius Star Cloud, above the spout of the Teapot; the Great Rift, a dark lane of dust dividing the Milky Way into two streams southward from Cygnus; Lagoon Nebula M8 (Messier 8), above the tip of the spout; star clusters M7 and M6, near the end of the tail of Scorpius; and much more.

As for the mornings: Mercury makes a brief visit to the a.m. sky. It brightens past first magnitude (to +0.9) by Aug. 5 to become visible low in the east-northeast morning twilight. During Aug. 5-10, it lingers 9 degrees to the lower right of Pollux while brightening another magnitude to -0.1. Mercury reaches greatest elongation, 19 degrees west of the sun, on Aug. 10, and on Aug. 11, a line from Castor to Pollux, 4.5 degrees apart, extended nearly 10 degrees, locates Mercury. Late in the month, Mercury sinks into bright twilight; superior conjunction beyond the sun will occur Sept. 3. The “Dog Star” Sirius, the brightest star, emerges in the east-southeast morning twilight before mid-August. Sirius rises 4 minutes earlier each morning, climbing higher as the month progresses. Note Orion’s belt points almost directly to Sirius.

Follow the moon in morning sky Aug. 15-29: On Aug. 15, the moon is full, setting in the west-southwest. The moon passes last quarter phase on Aug. 23, while 9 degrees south of Pleiades. On Aug. 24, the fat crescent moon is 2 degrees north of Aldebaran, eye of the Bull. On Sunday, Aug. 25, the 30 percent crescent moon occults third-magnitude Zeta Tauri, tip of southern horn of Taurus. From the Coachella Valley, the star disappears behind the bright edge of the moon at 3:46 a.m., and reappears from behind the dark, earthlit side at 4:41 a.m. It’s best viewed with a telescope.

Absent in August are Venus, in superior conjunction on night of Aug. 13, and Mars, in conjunction on Sept. 2. When passing beyond the sun, Venus and Mars remain out of sight for longer than other planets, because their motions most closely match that of Earth; Venus is the next planet inward from Earth, and Mars is the next planet beyond Earth’s orbit. Venus goes faster than Earth and so emerges from beyond the sun into the evening sky. Mars goes more slowly and emerges into the morning sky. During the 2019-20 school year, each participates in a spectacular gathering: Venus, with Jupiter and Saturn at dusk in late November-early December; and Mars, with Jupiter and Saturn at dawn in late March 2020. Stay tuned!

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. The calendar illustrates many of the present and future events described here. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues, mailed quarterly.

For a preview of evening and morning planet viewing through August 2020, see Jeffrey Hunt’s two-page graphic summary of moon and planet setting and rising times, relative to the times of sunset and sunrise, exact for Palm Springs, below. The graph of evening planet setting times shows the departure of Jupiter and Saturn in December 2019, and Venus improving until its very favorable evening appearance in March 2020, when it will set 3 1/2 hours after sunset, followed by its rapid departure from the evening sky in May. The graph of morning-planet-rising times shows the gradual emergence of Mars before dawn in autumn 2019; the emergence of Jupiter and Saturn in January-February 2020; and the sudden rise of Venus into predawn prominence in June-July 2020. The charts also make it easy to pick out the best dates to see Mercury in evening and morning skies.

Check the website of the Astronomical Society of the Desert at www.astrorx.org for dates and times of our evening star parties. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet—wear warm clothes), will have its next monthly sessions starting at dusk on Saturdays, Aug. 31 and Sept. 28. Our primary, more-accessible location is at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, within four miles south of Highway 111 in Palm Desert). Monthly sessions there will resume on Saturday, Oct. 5.

But don’t wait until then! You can pre-register for one of the Stargazing Parties offered several times each month at the Rancho Mirage Library Observatory at www.ranchomiragelibrary.org/observatory.html. (Click on Stargazing Parties, then sign up for their eNewsletter to receive registration information.) If you go farther afield, check out the Sky’s the Limit Observatory and Nature Center in Twentynine Palms, at www.skysthelimit29.org.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

In July, watch Saturn follow Jupiter into the evening sky. Witness a complete lunar cycle from beginning to end, as the best season for Milky Way evening viewing gets under way.

On July 9, the Earth overtakes Saturn, and the planet appears at opposition, 180 degrees from the sun, and visible all night: In the southeast at dusk, highest in the south in middle of night, and in the southwest at dawn. We overtook Jupiter 29 days earlier, on June 10. Each is a worthy showpiece for telescopic viewing: Jupiter, with dark cloud belts parallel to its equator, and four bright satellites discovered by Galileo in 1610; and Saturn, with rings now tipped a generous 24 degrees from edgewise. As we overtake them, both planets retrograde—go west against background stars, by just more than 2 degrees in July. So they stay 31 degrees apart all month, with Jupiter creeping closer to Antares, and Saturn backing toward the Teapot of Sagittarius. Saturn passes 1.1 degrees north of the third-magnitude star Pi in the “Teaspoon” of Sagittarius on July 18.

An entire lunation—new moon to new moon—fits into July with a day to spare. In bright dawn twilight on July 1, an old crescent moon, some 31 hours before new, appears in the east-northeast, 5 degrees to the upper right of Venus. We’re getting our last views of Venus before superior conjunction on Aug. 13. On July 1, Venus is 12 degrees from the sun, and rises 50 minutes before sunup; by the 31st, these numbers shrink to 4 degrees, and about 20 minutes.

After a total solar eclipse in the South Pacific, Chile and Argentina on July 2, we in California will see a young crescent moon very low in the west-northwest at dusk on July 3. The moon’s age will be 32-33 hours. You’ll probably need binoculars to see Mars (magnitude +1.8) and Mercury (magnitude +1.4) 3.8 degrees apart, within 2 degrees and 5 degrees of the upper left of the moon. These planets are in their last days of visibility, appearing lower nightly, with Mercury dropping faster than Mars, and fading to equal Mars by July 6. Mercury will pass inferior conjunction, nearly between Earth and the sun, on July 21. Mercury, in its crescent phases, is faint, because, unlike Venus, it is cloudless, and we see its surface, where features cast shadows, dimming Mercury’s total brightness.

Dominating the evening sky this summer and well into autumn are the two giant planets of our solar system. On July evenings, find steady, bright Jupiter in the southeast to south at dusk, with Saturn 31 degrees to its lower left, and twinkling red Antares, heart of Scorpius, 8.5 degrees to 6.8 degrees to Jupiter’s right/lower right. Also, look for the Summer Triangle of Vega, Altair and Deneb in the northeast to east, rising higher as the month progresses; golden Arcturus and blue-white Spica well up in the southwestern quadrant of the sky; and in the west, sinking into the west-northwest twilight glow, Regulus, heart of Leo.

The Milky Way in a dark sky, from the Cygnus Star Cloud along the Swan’s neck within the Summer Triangle, down through the Great Rift—clouds of dust obscuring the stars behind and dividing the Milky Way into two streams, with “clouds of steam” appearing to billow out of the spout of the Teapot of Sagittarius—is an inspiring sight all should experience! The best dates for Milky Way viewing in evening hours this summer are through July 3, after end of twilight; July 4-6, after evening moonset; July 21-Aug. 2, after twilight; Aug. 3-5, after evening moonset; Aug. 20-31, after end of twilight; and Sept. 1-2, after evening moonset.

Follow the moon on July evenings. A waxing crescent moon passes just 2-3 degrees to the upper right of Regulus on July 5. After passing first-quarter phase while below the horizon early on July 9, a slightly gibbous moon appears 7 degrees to the upper left of Spica that evening. On the evening of July 12, find Jupiter 9 degrees to the moon’s lower left, and Antares 8 degrees below a fat gibbous moon. On the next evening, July 13, the moon will appear 4-5 degrees to the left of Jupiter, while Saturn will appear within 27 degrees to the moon’s lower left. On July 14, the moon appears 17 degrees to the lower left of Jupiter and 14 degrees to the upper left of Saturn. On July 15, the nearly full moon will appear only 1-2 degrees to the right of Saturn. On July 16 at dusk, the moon, six hours past full, appears 11 degrees to the lower left of Saturn.

Observe in mornings to follow the moon for rest of July. In brightening dawn twilight on the 16th, the moon, not quite full, appears 2 degrees to the upper left of Saturn, low in the southwest to west-southwest. By July 25, the waning moon has passed last quarter phase, and appears slightly less than half full in the southeast. On July 27, the crescent moon will appear in the east, with the Pleiades cluster 9 degrees to the upper left, and bright Aldebaran, eye of Taurus, within 7 degrees to the moon’s lower left. Look early enough, before the sky brightens too much, to enjoy these fields through binoculars. Stars of the Hyades cluster can be seen between the moon and Aldebaran that morning. By late in July, Orion’s shoulder, red Betelgeuse, and his foot, blue Rigel, can be spotted low in the east, with his three-star belt between them. On July 28, the crescent moon appears 7-8 degrees to the lower left of Aldebaran. On the 29th, a beautiful, thinner crescent moon with earthshine will appear 14 degrees to the upper left of Betelgeuse. On July 30, look for the last, easy crescent low in east-northeast, with the Gemini Twins—Pollux 4.5 degrees below Castor—11-12 degrees to the left of the moon.

In your July predawn forays, look for the Summer Triangle well up in the west to west-northwest; the Mother Goat star Capella in the northeast; and Fomalhaut, mouth of the Southern Fish, in the south to south-southwest. Note the stars, and slow-moving Saturn, are in about the same positions they’ll occupy in the evening sky in December, several months hence.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. The calendar illustrates many of the events described here. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly.

Check the website of the Astronomical Society of the Desert at www.astrorx.org for dates and times of our evening star parties. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have its next monthly sessions starting at dusk on Saturdays, July 27 and Aug. 31.

You can pre-register for one of the Stargazing Parties offered several times each month at the Rancho Mirage Library Observatory at www.ranchomiragelibrary.org/observatory.html. (Click on Stargazing Parties; then sign up for their e-newsletter to receive registration information.) If you go farther afield, check out the Sky’s the Limit Observatory and Nature Center in Twentynine Palms, at www.skysthelimit29.org.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

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