CVIndependent

Sun02182018

Last updateWed, 27 Sep 2017 1pm

Evenings during twilight in early December 2017 feature a half-dozen stars of first magnitude or brighter, including the Summer Triangle of Vega, Altair and Deneb well up in the west, getting lower as month progresses; Fomalhaut, mouth of the Southern Fish, in the south; and Capella, the Mother Goat star, ascending in the northeast, with red-orange Aldebaran, eye of Taurus, to its lower right.

Binoculars and an unobstructed view are needed to spot Saturn, with Mercury close to its lower left, very low in the southwestern twilight glow 2.8 to 2.3 degrees apart Dec. 1-3, some 40 minutes after sunset. But both sink lower each evening, with Mercury fading to the equal of Saturn by Dec. 3, and fading rapidly thereafter. Mercury passes inferior conjunction, nearly between Earth and the sun, on Dec. 12, and Saturn hides in conjunction on the far side of the sun on Dec. 21.

In evening twilight late in month—or later in the evening in early December—watch the eastern horizon for the rising of reddish Betelgeuse and blue-white Rigel. About midway between them, Orion’s vertical three-star belt confirms their identity as Hunter’s shoulder and foot.

Our morning chart (below) depicts the sky about 45 minutes before sunrise, but we advise you to begin viewing at least a half-hour earlier than that, to allow time to locate all the bright objects before they are drowned out in the brightening twilight. Steady Jupiter in the southeast is the most prominent object during the half-hour beginning 75 minutes before sunup. (Venus doesn’t rise until 45 minutes before sunrise on Dec. 1; 30 minutes before on Dec. 12; and only 15 minutes before sunrise on Dec. 23.) Binoculars are increasingly useful for spotting Venus before sunup on the last possible date before superior conjunction, beyond the sun on Jan. 9.

Next in prominence after Jupiter are twinkling blue-white Sirius in the southwest to west-southwest, until it sinks from view late in the month; golden Arcturus high in the east; blue-white Vega rising higher in the northeast; and Capella sinking in the northwest. Mercury, very low in the east-southeast to southeast, attains magnitude +1 by Dec. 20, and magnitude 0 by Dec. 24, and for the rest of month ranks second in brilliance, after only Jupiter, since Sirius has departed.

Other bright morning objects include the Winter Hexagon, which has Sirius and Capella marking its southern and northern vertices, and red Betelgeuse inside. But Rigel, Aldebaran, Sirius and Betelgeuse exit the morning sky in December, leaving only the upper arch of Procyon, Pollux (with Castor 4.5 degrees to its right, not shown) and Capella.

Regulus, heart of Leo, is high in the southwest to west-southwest following the Hex across the sky. I like to imagine Leo chasing his menu, which includes some beef (Aldebaran in Taurus), two dogs (Sirius and Procyon in Canis Major and Canis Minor), a mother goat (Capella in Auriga) and even some human fare (Rigel and Betelgeuse of Orion, the Hunter, becoming the Hunted; and Pollux and Castor, of Gemini, the Twins).

Following Regulus across the sky are Arcturus and Spica. The latter star marks the ear of grain in the hand of Virgo, the next zodiac constellation east of Leo. The zodiac constellations serve as hosts to the bright objects of the solar system, namely the sun, moon and planets.

On Dec. 1, dim red Mars appears just 3 degrees from Spica and 16 degrees to the upper right of Jupiter. Jupiter itself is 4 degrees west-northwest of the third-magnitude star Alpha in Libra on Dec. 1; within 1 degree of that star Dec. 18-26; and as close as 0.7 degrees from Alpha Lib on Dec. 21-23. On Dec. 31, Mars is 3 degrees to the upper right of Jupiter, and 20 degrees to the lower left of Spica. On the last morning of 2017, Alpha Lib lies nearly midway between the planets, 1.5 degrees from Mars and 1.7 degrees from Jupiter—a beautiful sight for binoculars! The star’s Arabic name, Zubenelgenubi, meaning “Southern Claw,” refers to its assignment to a larger early version of the Scorpion, the next zodiacal constellation east of Libra. The pairing of Jupiter with Alpha Lib on Dec. 22 is the first of a triple conjunction between them. Jupiter, retrograding, will pass closely north of the star on June 3, 2018, and then, after resuming direct (eastward) motion, will pass closely north of it a third time, on Aug. 15.

Mercury, pulling away from its inferior conjunction of Dec. 12, brightens rapidly in the morning sky and holds a steady 28 degrees to the lower left of Jupiter Dec. 21-27. Look 8 degrees to the upper left of Antares, heart of the Scorpion, Dec. 20-27. During Dec. 28-30, Mercury is 9 degrees to the left or lower left of Antares. On Dec. 31, Mercury is 31 degrees to the lower left of Jupiter and 10 degrees to the lower left of Antares. On New Year’s morning, Mercury reaches greatest elongation, 23 degrees from the sun. On the mornings of Jan. 6 and 7, Mars will appear only 0.3 degrees from Jupiter. Within a week later, on Jan. 13, Mercury will pass 0.8 degrees south of Saturn. Wouldn’t a good pair of binoculars to view these events make a great gift for a skywatcher?

December opens with a few brightly moonlit nights. On Saturday evening, Dec. 2, the moon rises 20 minutes before sunset and is nearly full. An hour after sunset, find the Pleiades 10 degrees to the moon’s upper left, and Aldebaran, whose name means “the Follower” (of the Pleiades), within 14 degrees below the Pleiades and 7 degrees to the moon’s lower left. The moon creeps closer to Aldebaran throughout that night. During morning twilight on Sunday, Dec. 3, use binoculars to spot Aldebaran very close to the moon’s upper left. A “supermoon,” the closest full moon of 2017, occurs at 7:47 a.m. that morning, just more than an hour after moonset in Palm Springs. The moon reaches its least distance from Earth just 17 hours later, at 12:46 a.m. on Dec. 4.

Moonrise early on Sunday evening, Dec. 3 (as seen from Palm Springs), occurs at 5:11 p.m. Although more than nine hours past full, the moon, rising 33 minutes after sunset, will be impressive. Note Aldebaran 8 degrees to the moon’s upper right.

After it’s full, moonrise occurs later each night: On Monday, Dec. 4 at 6:10 p.m.; on Dec. 5 at 7:13 p.m. (northernmost moonrise of the month); on Dec. 6 at 8:19 p.m.; on Dec. 7 at 9:25 p.m.; and on Dec. 8 at 10:30 p.m.

On Dec. 5, two weeks have elapsed since Nov. 21, when Earth passed between the sun and the Pleiades (Seven Sisters) star cluster. Starting on Dec. 5, the moon is well below the horizon at the end of evening twilight, nearly 1 1/2 hours after sunset, and the sky is then dark and moonless. Starting on the evening of Dec. 5, face east-northeast to east at dusk and watch the Pleiades emerge and ascend in the deepening twilight. The scene is well described in lines by Alfred Lord Tennyson.

After the full moon, you can follow its motion in the morning sky, averaging 13 degrees per day eastward through the constellations of the zodiac. Watch the waning gibbous moon pass 9 degrees south of Pollux on Dec. 6, and leapfrog over Regulus on Dec. 8 and 9. On Dec. 12, find the waning crescent moon 9 degrees above Spica. On Dec. 13, the moon is 4 degrees to the upper left of Mars and 9 degrees to the lower left of Spica.

The moon rises very late on the night of Dec. 13 (as a 13 percent crescent at 3:21 a.m. on Dec. 14), leaving the peak of the Geminid meteor shower, overnight on Dec. 13-14, excellent for viewing meteors. Best hours are from Wednesday at 9 p.m. until first light of dawn at 5:15 a.m. on Thursday, although a few long trails from meteors grazing Earth’s atmosphere might be seen anywhere in the sky as Castor, near the shower’s radiant, rises soon after 6 p.m.

On the morning of Dec. 14, perhaps after a few good hours of meteor-watching, look for the moon passing 4 degrees north of Jupiter. On Dec. 15, find the moon within 12 degrees to the lower left of Jupiter. On the 16th, the last easy old crescent moon will appear 23 degrees to the lower left of Jupiter. If you have a very good low horizon between east-southeast and southeast, use binoculars to find Antares rising 9 degrees to the lower right of the crescent moon in brightening morning twilight.

In case the sky is very clear just after 6 a.m. on the morning of Sunday, Dec. 17, we have a site selected in northwestern Palm Springs to attempt a sighting of a very old moon, just a little more than 16 hours before new. We’ll announce the details in the “Impromptu Star Parties” link mentioned below.

We’re still checking out sites in Desert Hot Springs and the eastern Coachella Valley to attempt a sighting of a very young moon shortly after 5 p.m. on Monday, Dec. 18. The moon’s age will be just more than 18.5 hours. As the date draws near, visit the same link for details. Twelve days later, on Saturday, Dec. 30, the daytime waxing gibbous moon rising at 2:53 p.m. is covering Aldebaran. Telescopes may show the star emerging along the moon’s bright edge at 3:51 p.m.

The website of the Astronomical Society of the Desert, at www.astrorx.org, has a listing of our evening star parties at two locations. The 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). A session is scheduled there on Saturday, Dec. 23, from 5-8 p.m. Sawmill Trailhead, our high-altitude site (elevation 4,000 feet—wear warm clothes), will have a star party starting at dusk on Saturday, Dec. 9. The society’s website includes maps and directions for both locations. Star parties can be cancelled in poor observing weather. See the link to “Impromptu Star Parties” on that website.

On Friday, Jan. 5, I will present a summary of the coming year’s sky events. The summer and early autumn of 2018 will be outstanding for viewing planets in the evening sky, and there will be total lunar eclipses in January 2018 and January 2019. The talk will be held 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.

Also, check out the Sky’s the Limit Observatory and Nature Center in Twentynine Palms, at 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.

Published in Astronomy

Evening twilight: Venus rules! You won’t fail to notice this brilliant light in the southwest at dusk. Look for Mars to its upper left, and, for the first two or three weeks of December, Mercury to Venus’ lower right, provided you have an unobstructed view. The moon passes through this section of sky Nov. 30-Dec. 5.

The Summer Triangle of Vega, Altair, and Deneb is not far west of overhead in twilight in early December, and drifts westward as this month progresses. Blue-white Vega is next in brightness after Venus among objects visible in December’s evening twilight. Yellow Capella in the northeast is almost as bright. To Capella’s lower right, red-orange in color, is Aldebaran, eye of Taurus, the Bull, ascending in the east-northeast to east. Later in the month, Orion’s brightest stars, reddish Betelgeuse and bluish Rigel, rise almost together not far from due east. In December at dusk, look for Fomalhaut, mouth of the Southern Fish, crossing the southern sky about 25 degrees above the horizon.

Later in the evening, Orion is higher, and now the “Dog stars,” Sirius and Procyon, following the Hunter across the sky, have risen into view. Notice that Orion’s belt points downward to Sirius, the brightest star, and upward toward Aldebaran and the Hyades star cluster, and beyond to the Pleiades, or Seven Sisters, star cluster. Both star clusters are spectacular fields for binoculars!

Morning twilight: Now Orion and company are descending in the western sky, with some stars already out of view. Jupiter is the dominant “morning star” in the southeast to south, with first-magnitude Spica in Virgo not far below. After Sirius departs in the southwest, the brightest actual star remaining is golden-orange Arcturus in the east. Vega, reincarnated in the northeast, and Capella, sinking in the northwest, are almost as bright. Regulus, heart of Leo, the Lion, is high in the southern sky, going west as weeks pass. Before month’s end, watch for Antares and Saturn emerging out of the sun’s glare in the southeast.

Moon and planets: Watch the waxing crescent moon pass three planets Nov. 30-Dec. 5. The moon will appear to the upper right of Mercury on Nov. 30; above Mercury and to the lower right of Venus on Dec. 1; near Venus on Dec. 2 and 3; and near Mars on Dec. 4 and 5. Mercury stays 24 degrees to the lower right of Venus Dec. 2-12, then falls away and fades. Venus-Mars are 23 degrees apart on Dec. 2, narrowing to 12 degrees on Dec. 31.

See Venus in daytime: On Tuesday, Dec. 6, Venus follows the sun’s path. Place the sun just above an object such as a treetop or building around midday or in the afternoon. Return to the same observing location three hours and 12 minutes later, and Venus will appear in the same spot! On that date, telescopes show Venus two-thirds full. Watch for big changes in coming months, as Venus draws closer to Earth and becomes backlighted by the sun.

Aldebaran, eye of Taurus, is occulted by the moon on evening of Monday, Dec. 12. Since the moon is almost full, a telescope is needed to observe the star’s disappearance and reappearance. From the Coachella Valley, the leading dark edge of the moon covers the star shortly after 7:02 p.m., and the star reappears at the moon’s bright edge at 8:09 p.m.

The full moon on Tuesday, Dec. 13, rises within a quarter-hour after sunset. The peak of the Geminid meteor shower later that night will be greatly spoiled by moonlight; only the brighter meteors will be seen. Meteors might appear anywhere in the sky. To check if a meteor is a member of the Geminid shower, extend its track backward beyond the point where you saw the meteor light up. The track should extend back toward the radiant of the shower, near the star Castor in Gemini. Castor is very low in the northeast two hours after sunset, and nearly overhead shortly before 2 a.m.

After passing full, the waning gibbous moon, in the morning sky, passes the Twin stars Pollux and Castor in Gemini on Dec. 16; and Regulus, heart of Leo, on Dec. 18.

Winter begins on Dec. 21 at 2:44 a.m. On the next morning, Dec. 22, the moon appears as a thick crescent near Jupiter and Spica, and then several days later on Dec. 26 and 27 as a much thinner crescent near Antares and Saturn.

On Tuesday, Dec. 27, as morning twilight brightens, bright Jupiter is in the south-southeast, approaching its high point in the south. Look low in the southeast to east-southeast for the last easy old crescent moon, with Saturn 4 degrees below. In late December, Jupiter and Saturn are 60 degrees apart.

On Wednesday, Dec. 28, the old moon is hard to see, but it’s worth trying for rare opposing crescent moons on consecutive days: Dec. 28 at dawn, and Dec. 29 at dusk. On Dec. 28, using binoculars 20 to 30 minutes before sunrise, try for the crescent moon rising 9-10 degrees to the lower left of Saturn. The new moon occurs later that day, at 10:53 p.m. At early dusk on Thursday, Dec. 29, about 20 minutes after sunset, note Venus well up in the southwest. Using binoculars, try for the young crescent moon within 39 degrees to the lower right of Venus. To see the old moon on Dec. 28 and the young moon on Dec. 29, you’ll need very clear skies, unobstructed views, and binoculars or a telescope. Good luck!

On New Year’s Eve, you can conveniently find the most distant planet of our solar system. Get your telescope out at nightfall (about 90 minutes after sunset), and point it at Mars. Neptune, very faint at eighth magnitude, will appear very closely east of Mars, following the red planet through the telescopic field. As the evening progresses, Mars will appear to close in on the dim, more-distant planet.

Star parties: They provide wonderful opportunities to join with other folks to get great views of astronomical objects through a variety of binoculars and telescopes. The Whitewater Preserve will be hosting a star party on Saturday, Dec. 10, weather permitting, from dusk until 9 p.m. Reservations are requested; please call 760-325-7222.

The Astronomical Society of the Desert will host the next of our series of monthly star parties on Saturday, Dec. 17, from 5 to 8 p.m. They are held 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. Check www.astrorx.org for listings of our high altitude star parties at Sawmill Trailhead starting at dusk. The next one (at 4,000 feet—wear warm clothes!) will be held on Saturday, Dec. 3. Also, check the link to our “Impromptu Star Parties,” which could be announced on short notice at any time.

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. 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.

Published in Astronomy

December’s evening views begin with Venus near its brightest and highest in the southwest; the Summer Triangle of Vega-Altair-Deneb high in the west; and Fomalhaut, mouth of the Southern Fish, just east of due south.

At the start of December, the only bright objects in the eastern sky at mid-twilight are Capella, the mother goat star, in the northeast, and Aldebaran, eye of Taurus, very low in the east-northeast. Around Dec. 1 each year, that star is up all night from dusk to dawn. Wait a few minutes to allow the evening sky to darken a bit, and you’ll notice the compact Pleiades, or Seven Sisters cluster, 14 degrees above Aldebaran. The scene is beautifully described in Alfred Lord Tennyson’s “Locksley Hall”: “Many a night I saw the Pleiades / rising thro’ the mellow shade / glittering like a swarm of fireflies / tangled in a silver braid.” Don’t miss the view of the Pleiades through binoculars!

By month’s end, Venus is much lower in the west-southwest, because it’s heading toward inferior conjunction, nearly between Earth and the sun, on Jan. 11. The Summer Triangle is lower, too, and Fomalhaut crosses west of south, both owing to Earth’s revolution around the sun. Capella and Aldebaran rise higher in December for the same reason. Betelgeuse and Rigel, Orion’s brighter shoulder and foot, appear above the eastern horizon four minutes earlier each evening during twilight as the year’s end draws near. Between them, note the vertical line of three stars—Orion’s belt! Poet Robert Frost in “The Star-Splitter” (about a farmer who set fire to his house to collect insurance money to buy a telescope) describes what you can observe here in the Coachella Valley at this time of year: “You know Orion always comes up sideways / throwing a leg up over our fence of mountains …”

In the final days of December, bright Jupiter appears above our evening twilight horizon. From a good vantage point, you can spot Venus and Jupiter simultaneously. As Venus approaches the horizon, watch for Jupiter to rise in the opposite direction. Of course, you can spot Jupiter on any date this month just by looking late enough in the evening.

Don’t miss Venus near the crescent moon early on Thursday evening, Dec. 5. It’s also a great chance to spot Venus in the daytime, all afternoon! Here are times for each Sunday when Venus is directly south, with its height above the horizon in degrees, as seen from the Coachella Valley: Dec. 1, 2:40 p.m., 32 degrees up; Dec. 8, 2:28 p.m., 33 degrees up; Dec. 15, 2:10 p.m., 34 degrees up; Dec. 22, 1:44 p.m., 36 degrees up; and Dec. 29, 1:09 p.m., 38 degrees up. Many roads in the valley run north-south, which will help you face the right direction. Aim your binoculars at a distant mountain, and focus. Then point toward Venus, and observe its current crescent phase, getting thinner and larger in size as this month progresses! (Take care that you do not aim binoculars at the sun.)

Our morning twilight map (below) shows the sky nearly 45 minutes before sunup. On Sunday, Dec. 1, five solar-system bodies are easily visible. From west to east, they are Jupiter, about halfway from horizon to overhead in west; Mars, even higher in the south-southeast; and a clustering of Saturn, the old crescent moon, and Mercury low in the east-southeast. From the Coachella Valley, Saturn is 4 degrees above the thin moon, and Mercury appears within 4 degrees to the moon’s lower left. There are less than 35 hours until the invisible new moon (on Dec. 2 at 4:22 p.m.), so the moon will be gone by Monday morning. Mercury drops out of sight in December’s second week, on its way to the far side of the sun on Dec. 28.

The two brightest objects in our morning sky are steady Jupiter, sinking west toward west-northwest, and twinkling Sirius, until it sets in the west-southwest.

On Dec. 1, Earth is heading in the direction of 10 degrees east (left) of Regulus. As the Earth curves around the sun in the next five months, it will overtake the slower-moving outer planets: Jupiter in early January, Mars in early April, and Saturn before the middle of May. As a result, these planets, along with their background stars, will progress toward the western horizon in our morning sky, and will appear above our eastern horizon in the early evening sky as Earth passes them in turn.

On Dec. 2, Mars appears midway between Regulus and Spica, 27 degrees from each.

If you enjoy chasing very thin crescent moons in twilight, there’ll be three chances in coming weeks: (1) A young crescent on the evening of Tuesday, Dec. 3, age 25 hours, very low in west-southwest 28 degrees to the lower right of Venus; (2) a very old crescent on the morning of Dec. 31, 21 hours before new, very low in the east-southwest, 20 degrees to the lower left of Antares; and (3) an extremely young crescent in the very early evening on Jan. 1, age 14 hours, within 8 degrees to the lower right of Venus. (My personal record for a youngest moon sighting is 13.5 hours past new.)

The Geminid meteor shower is largely spoiled by bright moonlight this year. The best viewing with the least moonlight will occur on Friday, Dec. 13 from 3:30 to 5:30 a.m., and on Saturday, Dec. 14, from 4:30 to 5:30 a.m.

Comet ISON will pass within 725,000 miles of the sun’s surface on Thanksgiving Day and make a sharp turn to the north, or upper left, of the predawn sun. By Dec. 6, it will rise as morning twilight begins. Visit www.pa.msu.edu/abrams/ison/ for updates on the comet.

The Astronomical Society of the Desert will host a skywatching session on Saturday, Dec. 7, from 5 to 8 p.m. at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument on Highway 74, about four miles south of Highway 111 in Palm Desert. For more on the club’s activities, visit astrorx.org. The Whitewater Preserve is hosting a skywatch on Friday, Dec. 20, from 5:30 to 9 p.m., preceded by afternoon viewing of the crescent Venus. I hope to see you there, and at some of the WildLights evenings at the Living Desert, where we’ll show the crescent Venus and other sky phenomena.

Robert C. Victor was a staff astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller, who provided the twilight charts, 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.

Published in Astronomy