An old Moon joins Morning Mercury and Saturn, and Moonless Nights reveal the Winter Milky Way!
The Moon and Planets
The moon spends most of this week in the pre-dawn sky, where it shows a lovely crescent that thins as it approaches the sun, and New Moon phase, on Friday. With the moon sitting near the sun during this period, we are treated to especially dark night skies. (More on this later.) With the moon leading the sun across the sky, you can look for it, to the right of the sun, in the daytime until late afternoon.
On Tuesday morning, low in the southeastern sky, the crescent moon visits the morning planet Saturn, landing only a few finger widths (3°) to the upper left of the yellowish planet. The best time to look for the pair is between 6 and 7 am local time. Even lower in the southeastern sky on Wednesday and Thursday, the moon hops over Mercury, appearing about 6° (a palm’s width) above the planet (Wed) and to the left of the planet (Thu). You’ll need to look between about 6:45 am and 7 am local time.
On Saturday, the moon returns to the western evening sky as a very thin “Cheshire cat” smile visible in the twilight immediately after sunset, which occurs around 5:20 pm local time. On Sunday evening will be easier to spot the young moon.
Venus is the brilliantly bright object visible every evening in the western sky, until it sets around 9:30 pm local time. In a telescope, Venus continues to show a “half-moon” shape (phase) this week. Meanwhile, reddish Mars continues to sit about a palm’s width to the upper left of Venus, and sets about 9:50 pm local time.
Blue-green Uranus is halfway up the southwestern sky at dusk — just inside the western (right) arm of the “V” of Pisces the Fishes. The planet sets just before midnight local time. Tiny Neptune is in Aquarius the Water-bearer, well to the lower right of Venus, and it sets about 8:15 pm local time.
Don’t forget that the large asteroid Vesta is near peak brightness this month, sitting about 5° (less than a palm’s width) below the bright star Pollux in Gemini the Twins. At apparent magnitude 6.3, the asteroid is observable with unaided eyes (under this week’s dark skies), in binoculars, and in small telescopes. Its rapid motion through the background stars can be noted by observing it on separate evenings. I posted a sky chart with its track here.
Bright, white Jupiter is a late night target, rising in the east just before midnight local time. All winter, it’s been sitting just a few finger widths from the bright white star Spica in Virgo the Maiden. By dawn, it’s moved above the southern horizon. Soon, I’ll start reporting the Jupiter moon events and Great Red Spot sighting opportunities.
Saturn is rising this week about 5 am local time. You should easily see its yellowish dot low in the east for half an hour before sunrise, while the sky is still dark. A few days ago, Mercury reached its greatest angle west of the sun, and maximum visibility for this apparition, but you can continue to hunt for it this week for a few minutes centred around 6:45 am local time, very low above the southeastern horizon.
Trace the Winter Milky Way
Our solar system sits inside the vast flattened disk of our galaxy, about one-third of the way towards the outer edge. So the faint Milky Way band, made up of countless stars in our galactic disk, can be traced in a huge circle around the sky. The core of the galaxy, and therefore most of the stars, are in the part of the sky visible in summer nights, and the outer rim sits in the opposite direction — gracing our winter evening skies. Except for a period of time in late spring when the Milky Way aligns with the horizon, there’s always a part of it visible in the night sky.
On a clear night, especially this week, when the moon leaves the night sky dark, head outside to an open area away from city lights and look for the outer reaches of the Milky Way. It rises out of the southeastern horizon just to the left (east) of the bright star Sirius in Canis Major the Big Dog, and gradually diminishes in intensity as you follow it higher, passing between Orion the Hunter and Gemini the Twins, and higher, just beyond Taurus the Bull’s horn tips.
The point in the sky directly opposite the galactic core is a few degrees above the moderately bright star Alnath, which is Taurus’ higher horn tip and also sits opposite the bright yellow star Capella in the ring of stars that form the constellation Auriga the Charioteer. By now, you’re looking near the zenith, at the top of the sky. But the Milky Way isn’t visually dimmest here. Because the galaxy has a non-uniform structure of spiral arms wrapping around the central bulge, and because dark gas and dusk block the starlight here and there, our Milky Way’s dimmest location is one constellation farther along, in Perseus the Hero, near Perseus’ brightest star, Mirfak.
Turn around and face northwest. In January, Perseus sits high in the northern sky, above the distinctive “W” shaped constellation Cassiopeia the Queen. The Milky Way is very dim here, but it builds in intensity again as we trace its thickening disk down through Cassiopeia and lower, towards the southern horizon, passing just to the left of her husband, Cepheus the King.
Most of the famous Messier List objects sit on or near the Milky Way because they are made up of concentrations of stars (clusters) and gas (nebulae). But looking above and below the plane of the Milky Way (to the left and right of it this time of year), reveals other cities of stars — separate galaxies that aren’t obscured by the stars in our backyard. The brightest and easiest one to spot is the great Andromeda Galaxy, which sits only 15° (or 1.5 outstretched fist widths) to the lower left of Cassiopeia’s bottom half.
Stargazing News for this week (from January 22nd) by Chris Vaughan.