This Week's Sky at a Glance, April 5 – 14

Periodic Comet Pons-Brooks is at its predicted peak brightness, about magnitude 4.5, low in the west-northwest at the very end of twilight. It's in range of binoculars even through a mediocre suburban sky, and it's detectable naked-eye in a truly black sky. Brightness outbursts are possible; the comet has had two big ones in the last year (brightening by 5 and 3 magnitudes!), so check it every clear evening.

It's lower right of Jupiter and heading toward it, across Aries. But it's dim enough that you'll have to know just where to look! Use the finder chart with the article in the March Sky & Telescope, page 48, or this interactive chart (set your date there, and note the field sizes in the captions. 10° is nearly twice the width of a typical binocular's field of view. The direction down on the chart is probably not down in your view).

On March 31st I spotted the comet near Alpha Arietis with 10x50 binocs through a mediocre suburban sky, just at the very end of twilight. It was a little gray fuzzball, elongated upward. I didn't need averted vision.

Betelgeuse has stopped fading. Orion's red supergiant, always a slow variable star, lost 0.3 or 0.4 magnitude (visual) from late January to early March, prompting speculation that another "great dimming" might be starting like its one in winter 2000. But for the last month Betelgeuse has held at about mag +0.7. That amounts to hardly more than its usual slow wobbles. Will it resume fading? Or rebrighten? Keep watch using Aldebaran and Procyon as your comparison stars.

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FRIDAY, APRIL 5

■ Shortly after nightfall around this time of year, Arcturus, the bright Spring Star climbing in the east, stands just as high as Sirius, the brighter Winter Star descending in the southwest (for skywatchers at mid-northern latitudes).

These are the two brightest stars in the sky at the time. But Capella is a very close runner-up to Arcturus! Spot it high in the northwest.

SATURDAY, APRIL 6

■ More Sirius doings: The two Dog Stars stand vertically aligned around the end of twilight. Sirius in Canis Major is the bottom one, and Procyon in Canis Minor is about two fists above it. When will they appear exactly vertical for your location and date? Hint: Like everything else among the fixed stars, it happens 4 minutes earlier each day.

SUNDAY, APRIL 7

■ High above the Big Dipper late these evenings, nearly crossing the zenith, 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 Springs (or Leaps) of the Gazelle, from early Arab lore. They form an east-west line that lies roughly midway between the bowl of the Big Dipper and the Sickle of Leo. The line is 30° (three fists) long. See the evening constellation chart in the center of the April Sky & Telescope.

According to the ancient Arabian story, the gazelle was drinking at a pond — the big, dim Coma Berenices star cluster — and bounded away when startled by a flick of Leo's nearby tail, Denebola. Leo, however, seems quite unaware of this, facing the other way.

Another version sees Coma Berenices as Leo's extended tailtip and the pond as formed by stars in Ursa Major. For more of the legend see Steve O'Meara "Springs of the Gazelle" in the April Sky & Telescope, page 45.

MONDAY, APRIL 8

■ New Moon, and oh by the way, the result this time is an eclipse of the Sun in case you hadn't heard.

■ After the recovered Sun sets a few hours later, looking all innocent like nothing happened, and twilight fades and the stars come out, you'll find Orion still well up in the southwest in his spring orientation: striding down to the right, with his belt horizontal. The belt points left toward Sirius and right toward Aldebaran and, farther on, the Pleiades 0ver Jupiter.

TUESDAY, APRIL 9

■ This is the time of year when the dim Little Dipper juts to the right from Polaris (the Little Dipper's handle-end) during late evening. With the Moon gone from the evening sky, the subtle Little Dipper stands out about as well as it ever does.

The much brighter Big Dipper curls over high above it, "dumping water" into it. The two dippers do the reverse water dump in the fall.

■ Vega, the bright "Summer Star," rises in the northeast these evenings. How early or late depends on your latitude and on your longitude within your time zone.

Exactly where should you watch for it to come up? Spot the Big Dipper almost overhead in the northeast. Look at Mizar at the bend of its handle. If you can see Mizar's tiny, close companion Alcor (binoculars show it easily), follow a line from Mizar through Alcor all the way down to the horizon. That's where Vega makes its appearance.

WEDNESDAY, APRIL 10

■ Having moved well east of our line of sight to the Sun, the Moon now appears as a thin crescent in evening twilight, hanging about 4° upper right of Jupiter.

■ After full dark, Castor and Pollux shine together west of the zenith. Pollux is slightly the brighter of these "twins."

Draw a line from Castor through Pollux, follow it farther left by 26° (about 2½ fist-widths at arm's length), and you're at the dim head of Hydra, the Sea Serpent. In a dark sky it's a subtle but distinctive star grouping, about the width of your thumb at arm's length. Binoculars show it easily through light pollution.

Continue that line farther on by 1½ fists and you hit Alphard, Hydra's orange, 2nd-magnitude heart.

Another way to find the head of Hydra: It's almost midway from Procyon to Regulus.

THURSDAY, APRIL 11

■ Now the Moon hangs about 6° over the Pleiades during and after dusk. Think photo opportunity. Brace your camera on something, and zoom in.

FRIDAY, APRIL 12

■ Just above the crescent Moon this evening is Beta Tauri (El Nath), which at magnitude +1.6 just misses being a 1st-magnitude star. Far to their right or upper right is brighter Capella. A little farther to their left or lower left is Betelgeuse.

SATURDAY, APRIL 13

■ Arcturus shines brightly in the east these evenings. The Big Dipper, high in the northeast, points its curving handle lower-right down toward it.

Arcturus forms the pointy end of a long, narrow kite asterism formed by the brightest stars of Boötes, the Cowherd. The kite is currently lying on its side to Arcturus's left. The head of the kite, at the far left, is bent slightly upward. The kite is 23° long, about two fist-widths at arm's length.

SUNDAY, APRIL 14

■ The Moon, less than a day from first quarter, hangs under Castor and Pollux this evening.

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This Week's Planet Roundup

Mercury, Venus, and Neptune are hidden in the glare of the Sun. But Venus and Jupiter will blaze into view in daytime during the April 8th total solar eclipse! See What Will We See in the Sky During Totality? Even if you have only a deep partial eclipse, the sky may become dim enough for Venus and Jupiter to show through. They'll be on opposite sides of the blazing crescent, Jupiter twice as far from it as brighter Venus.

Mars and Saturn, both about magnitude +1.2, rise after dawn begins. Use binoculars to try for them just above the east-southeast horizon about 45 minutes before sunrise. They're 3° apart on the morning of April 6th, as shown below. They're in conjunction, ½° apart, on the 10th and 11th. Mars is the redder one.

Jupiter, magnitude –2.1 in Aries, is the bright "star" shining in the west in twilight, not very high. It sinks lower after dark and sets around 10 p.m. Jupiter is now the only easy planet in the entire night sky.

Uranus, magnitude 5.8 in Aries, hides about 2° above Jupiter in early evening. Immediately after dark, once you're done with Comet Pons-Brooks nearby, use your binoculars to find Uranus with the finder charts in last November's Sky & Telescope, pages 48-49 (which do not show Jupiter).

The thin crescent Moon joins Jupiter, Uranus, and the comet on Wednesday evening the 10th.

Neptune is hidden in the sunrise.

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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 and graphics that also depend on longitude (mainly Moon positions) are for North America.

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

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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 a more detailed constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy.

Once you get a telescope, to put it to good use you'll need a much more 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 all 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, are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to mag 9.75). And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.

Can computerized telescopes replace charts? Not for beginners I don't think, especially not on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning the sky. 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."

If you do get a computerized scope, make sure the drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).

However, finding faint telescopic objects the old-fashioned way with charts isn't simple either. Learn the tricks at How to Use a Star Chart with a Telescope. 

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Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the naked-eye heavens above. It's free.

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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

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

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