This Week’s Sky at a Glance, March 30 – April 7

 

Mars and Saturn in conjunction at dawn, April 2, 2018

Mars and Saturn glow like a pair of tilted, unequal eyes in early dawn on the morning of their conjunction.

Friday, March 30

• After nightfall, Orion is still well up in the southwest in his spring orientation: striding down to the right, with his belt horizontal. Shining above the belt is bright orange Betelgeuse. Down below the belt is bright white Rigel.

• Now that it's spring, the signature fall-and-winter constellation Cassiopeia retreats downward after dark. But for skywatchers at mid-northern latitudes Cassiopeia is circumpolar, never going away completely. Look for it fairly low in the north-northwest these evenings. Its W pattern stands roughly on end. By midnight or 1 a.m. it's at its lowest due north, lying not quite horizontally.

Saturday, March 31

• Full Moon (exact at 8:37 a.m. EDT). Look lower right of the Moon for Spica. Look three times farther left of the Moon for brighter Arcturus.

Sunday, April 1

• Now Spica shines to the Moon's upper right.

• Before dawn on Monday morning April 2rd, Mars and Saturn are in conjunction, 1.3° apart. Spot them in the south-southeast, as shown above. They're not quite equal; Mars is 0.2 magnitude brighter, and it's tinted a deeper, fiery orange-yellow compared to Saturn's pale yellow-white.

Monday, April 2

• The Big Dipper glitters softly high in the northeast after dusk, tipping leftward on its handle. You probably know that the two stars forming the front of the Dipper's bowl (currently on top) are the Pointers; they point to Polaris, currently to their lower left. And, you may know that if you follow the curve of the Dipper's handle out and around by a little more than a Dipper length, you'll arc to Arcturus, now low in the east.

But did you know that if you follow the Pointers backward the opposite way, you'll land in Leo?

Draw a line diagonally across the Dipper's bowl from where the handle is attached, continue far on, and you'll go to Gemini.

And look at the two stars forming the open top of the Dipper's bowl. Follow this line past the bowl's lip far across the sky, and you come to Capella.

• By 11 p.m. the waning gibbous Moon is well up in the east-southeast. Look for Jupiter glaring some 7° below it. They rise higher into the early-morning hours. As dawn begins on Tuesday morning the 3rd, you'll find the Moon and Jupiter in the south-southwest.

Tuesday, April 3

• Capella is the bright star high in the west-northwest during and after dusk. Its pale-yellow color matches that of the Sun, meaning they're both about the same temperature. But otherwise Capella is very different. It consists of two yellow giant stars orbiting each other rather closely every 104 days.

Moreover, for telescope users, Capella is distantly accompanied by a tight pair of red dwarfs: Capella H and L, magnitudes 10 and 13. Article and finder charts.

Wednesday, April 4

• High above the Big Dipper late these evenings, nearly crossing the zenith for mid-northern skywatchers, are three pairs of dim naked-eye stars, all 3rd or 4th magnitude, marking the Great Bear's feet. They're also known as the Three Leaps of the Gazelle, from early Arab lore. They form a long line roughly midway between the Bowl of the Big Dipper and the Sickle of Leo.

According to Arab lore, the gazelle was drinking at a pond — the big, dim Coma Berenices star cluster — and dashed away when startled by a flick of Leo's nearby tail, Denebola. Leo, however, seems quite unaware, facing the other direction.

Thursday, April 5

• The Sickle of Leo stands vertical high in the south these evenings. Its bottom star is Regulus, the brightest of Leo. Leo himself is walking horizontally westward. The Sickle forms his front leg, chest, mane, and part of his head.

Moon, Mars, Saturn at dawn April 6, 7, 8, 2018

The waning Moon passes Mars and Saturn in early dawn. The Moon, as always, is drawn three times its actual apparent size. And it's always positioned for an observer near the middle of North America (exact for latitude 40° N, longitude 90° W).

• As dawn approaches on Friday the 6th, look for Mars and Saturn to the left of the waning Moon, as shown here.

Friday, April 6

• Right after dark, Orion is still well up in the southwest in his spring orientation: striding down to the right, with his belt turning roughly horizontal. The belt points left toward Sirius and right toward Aldebaran and, farther on, the Pleiades.

• As dawn approaches on Saturday the 7th, you'll find the waning Moon bunching up with Mars and Saturn, as shown here.

Saturday, April 7

• At this time of year, the two Dog Stars stand vertically aligned around the end of twilight. Look southwest. Brilliant Sirius in Canis Major is below; Procyon in Canis Minor is high above.

• Last-quarter Moon tonight (exactly so at 3:18 a.m. April 8th EDT). The Moon rises around 2 or 3 a.m. your local daylight saving time, some 8° or 10° to the lower left of Mars and Saturn. By dawn on the 8th they're all well up in the south-southeast, as shown here.

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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

Mars on Feb. 22, 2018

Mars was only a tiny 6.4 arcseconds wide when Damian Peach used the 1-meter Chilescope to take this stacked-video image remotely. "Amazing to think that Mars will be almost four times as wide by the end of July," he writes. "We are in for a real treat!" South is up. Syrtis Major is close to the right limb, and the Hellas basin far to its south is bright. A patch of orographic clouds is lower left of center, created by winds passing over Elysium Mons. "The famous Gale crater, location of the Curiosity rover, is located at the end of the longer of the tuning-fork prongs of Gomer Sinus." Those extend from the lower edge of dark Mare Cimmerium above center.

Jupiter on March 18, 2018

Jupiter on March 18th, imaged by Christopher Go. South is up. If you can see the Great Red Spot in your scope early these mornings, can you see the two subtler dark lumps in the North Equatorial Belt at the same longitude? For all of the Great Red Spot's predicted transit times, see the March Sky & Telescope, page 50.

Mercury is hidden in the glare of the Sun.

Venus (magnitude –3.9) shines low in the west in twilight. It sets as night becomes complete.

Mars and Saturn, together in Sagittarius, rise around 2 a.m. daylight-saving time. By the beginning of dawn they're two bright points close together in the south-southeast, above the fainter Sagittarius Teapot.

They appear closest, 1.3° apart, on the morning of April 2nd. They remain less than 2° apart from March 31st through April 5th, but watch their orientation change each morning.

Mars is brightening on its way to an unusually close opposition this summer. It's now slightly brighter than Saturn (they're about magnitude +0.2 and +0.5, respectively), and their color difference is obvious.

And before the first glimmer of dawn early this week, use binoculars to find the hazy globular star cluster M22 even closer to Mars than Saturn is. It's 5th magnitude.

Jupiter (magnitude –2.4, in Libra) rises around 10 or 11 p.m. daylight-saving time and shines as the brightest point in the late-night sky. It's highest in the south, presenting the sharpest views in a telescope, around 3 a.m.

Uranus and Neptune are lost in the glare of the Sun.

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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 Daylight Time (EDT) is Universal Time (also called UT, UTC, GMT, or Z time) minus 4 hours.

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"Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious."
— Stephen Hawking, 1942–2018

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"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

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"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 a liberal conspiracy. They are how we determine facts. Civilization's survival depends on our ability, and willingness, to do so."
— Alan MacRobert, your Sky at a Glance editor

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


 

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