This Week’s Sky at a Glance, January 12 – 20

Moon, Antares, Saturn, Mercury in the dawn, Jan. 13, 2018

On Saturday morning January 13th, the waning Moon points the way down to Mercury and Saturn in conjunction. They're still very low as dawn grows bright. Binoculars will help; their visibility in bright twilight is exaggerated here.

Moon, Mercury, Saturn, Jan 14, 2018

As dawn brightens on Sunday the 14th, the slim Moon hangs closer over Mercury and Saturn as the two planets move apart.

Moon, Mercury, Saturn at dawn, Jan 15, 2018

Then on Monday morning the 15th, use binoculars to help pick up the hairline crescent low to the two planets' left. Think photo challenge! Use a tripod and maximum zoom, or better, a long lens. For the scale of this scene, Mercury and Saturn appear only 3° apart (roughly the width of two fingers held at arm's length).

Friday, January 12

• Sirius, the Dog Star, rises in the east-southeast around the end of twilight now, if you're near latitude 40° north (New York, Denver, Madrid, Athens). From such latitudes, Procyon — left of Sirius, by 2½ fists at arm's length — precedes it up; "Procyon" is from the ancient Greek for "before the dog."

But if you're as far south as San Diego, the Gulf Coast, Jacksonville, or Cairo, Egypt, they rise almost at the same time.

• The eclipsing binary star Algol should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 9:45 p.m. EST. Algol takes several additional hours to fade and to rebrighten.

• As dawn brightens on Saturday the 13th, the waning crescent Moon hangs far to the lower left of Jupiter and Mars (outside the chart here), and upper left of Antares. Far to the Moon's lower left, near the southeast horizon, use binoculars to help find Mercury and Saturn. They're in conjunction about 0.8° apart (depending on your longitude).

Saturday, January 13

• Vega still twinkles quite low in the northwest after dusk. It’s sometimes called the Summer Star, but it’s way out of season now! It’ll soon be gone, to return to the evening sky next spring.

• In dawn on Sunday the 14th the Moon hangs above Mercury and Saturn, as shown in the series at right.

Sunday, January 14

• The Northern Cross in Cygnus, with Deneb at its top, plants itself nearly upright on the northwest horizon around 7 p.m. this week.

Monday, January 15

• In this coldest time of the year, the dim Little Dipper (Ursa Minor) hangs straight down from Polaris after dinnertime, as if, per Leslie Peltier, from a nail on the cold north wall of the sky. The Big Dipper, meanwhile, is creeping up low in the north-northeast. Its handle is very low and its bowl is to the upper right.

Tuesday, January 16

• After dinnertime, the enormous Andromeda-Pegasus complex runs from near the zenith down toward the western horizon.

Just west of the zenith, spot Andromeda's high foot: 2nd-magnitude Gamma Andromedae (Almach), slightly orange. Andromeda is standing on her head. About halfway down from the zenith to the west horizon is the Great Square of Pegasus, balancing on one corner. Down from its bottom corner run the stars outlining Pegasus's neck and head, ending at his nose: 2nd-magnitude Enif, due west and also slightly orange.

• New Moon (exact at 9:17 p.m. EST).

Wednesday, January 17

• On these moonless nights, explore little-known sights in Cassiopeia, high in the northwest — do you know about Eddie's Coaster? — using Sue French's Deep-Sky Wonders article, chart, and photos in the January Sky & Telescope, page 54.

For some more ambitions dark-sky targets, try for the dark clouds in Taurus charted in Alan Whitman's Going Deep column on page 57 of the same issue.

Thursday, January 18

• Sirius twinkles brightly after dinnertime below Orion in the southeast. Around 8 or 9 p.m., depending on your location, Sirius shines precisely below fiery Betelgeuse in Orion's shoulder. How accurately can you time this event for your location, perhaps using a plumb bob or the vertical edge of a building? Of the two, Sirius leads early in the evening, and Betelgeuse leads later. Welcome to pre-telescopic astronomy.

Friday, January 19

• The Moon is still just a thin waxing crescent and, in any case, it sets pretty soon after dusk. So: is your sky dark enough for you to see the winter Milky Way? By midevening now, the Milky Way runs vertically up and across the zenith: from Canis Major low in the southeast, up between Orion and Gemini, through Auriga and Perseus almost straight overhead, and down through Cassiopeia, Cepheus, and Cygnus to the northwest horizon.

Saturday, January 20

• Zero-magnitude Capella high overhead, and equally bright Rigel in Orion's foot, are at almost the same right ascension. This means they cross your sky’s meridian at almost exactly the same time: around 9 p.m. now, depending on how far east or west you live in your time zone. (Capella goes exactly through your zenith if you're at latitude 46° north: Portland, Oregon; Montreal; central France.)

So whenever Capella passes its very highest, Rigel is always marking true south over your landscape, and vice versa.

________________________

Want to become a better astronomer? Learn your way around the constellations! They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy.

Pocket Sky Atlas, jumbo edition

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and hundreds of telescopic galaxies, star clusters, and nebulae among them. Shown above is the Jumbo Edition for easier reading in the night. Larger view. Sample chart.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, is the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger Night Sky Observer's Guide by Kepple and Sanner.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."


This Week's Planet Roundup

Jupiter on Jan. 7, 2018

Jupiter's Great Red Spot is still as prominently orange as it was during last year's observing season. Christopher Go in the Philippines took this image before dawn on January 7th, using a 14-inch scope and video stacking during poor seeing. To simulate the view in the eyepiece of a telescope, squint your eyes and view the screen from a distance. Your amount of squinting can simulate the view in a 3-inch to a 16-inch scope. South is up.

Mercury (magnitude –0.3) and Saturn (half as bright at magnitude +0.5) are low in the morning twilight, as shown in the illustrations above.

Venus remains hidden behind the glare of the Sun.

Mars and Jupiter (magnitudes +1.5, and –1.8, respectively) rise in the east-southeast around 2 or 3 a.m. and are high in the south-southeast by early dawn. Jupiter is the brightest point in the sky. Mars is to Jupiter's lower left. They're 3° apart on January 13th, widening to 7° apart by the 20th.

Uranus (magnitude 5.8, in Pisces) is high in the south-southwest right after dark.

Neptune (magnitude 7.9, in Aquarius) is still findable low in the west-southwest immediately after dark. For both dim planets use our finder charts online or in the October Sky & Telescope, page 50.

______________________

All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.

Eastern Standard Time (EST) is Universal Time (also called UT, UTC, GMT, or Z time) minus 5 hours.

______________________

"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
— Carl Sagan, 1996

______________________

"Objective reality exists. Facts are often determinable. Vaccines save lives. Carbon dioxide warms the globe. Bacteria evolve to thwart antibiotics, because evolution. Science and reason are not fake news, not a liberal conspiracy. Civilization's survival depends on our ability, and willingness, to use them."
— Alan MacRobert, your Sky at a Glance editor

______________________

"Facts are stubborn things."
— John Adams, 1770

______________________

"The most damaging consequences of Truth Decay include the erosion of civil discourse, political paralysis, alienation and disengagement of individuals from political and civic institutions, and uncertainty over national policy."
Rand Corporation report, 2018


 

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.

COMMENT

This site uses Akismet to reduce spam. Learn how your comment data is processed.