This Week’s Sky at a Glance, April 16 – 24 – Sky & Telescope

This has was a crackling month for novae! The newest is Nova Scorpii 2021. It popped up and peaked round magnitude 8.6 on April 13th, then rapidly dropped to 10.Zero by the 15th. Will it rebound? See Bob King’s A Bouquet of Novae Brightens April Nights.

Nova Cassiopeiae 2021 (V1405 Cas) was, in the meantime, nonetheless holding regular at about magnitude 8.1 as of April 15th. It’s been about like that for 4 weeks now. See Bright Nova Erupts in Cassiopeia.

Comet ATLAS, at ninth magnitude, is crossing Hercules excessive within the early-morning sky, awaiting 6-inch and bigger telescopes. See Make the Most of Comet ATLAS.At the top of that article are data and charts for Nova Sagittarii 2021 No. 2 (V6595 Sgr), simply off the spout of the Sagittarius Teapot in good view earlier than the primary mild of daybreak. In the final two weeks this one has light steadily from magnitude 8.Zero to 10.5.



■ This night the waxing crescent Moon types a quadrilateral with Mars above it and Taurus’s horntip stars, Beta and fainter Zeta Tauri, to the perimeters as proven under.

Both Mars and the Moon move upward between the horntips of Taurus.SATURDAY, APRIL 17

■ Now the Moon shines higher left of tiny Mars, as proven above.

■ Bright Arcturus ascends within the jap sky throughout night whereas Capella, its shut match for brightness, descends within the northwest. They stand at precisely the identical altitude across the finish of twilight, relying in your location.

■ And at that point, the Sickle of Leo stands upright excessive within the south. Its backside star is Regulus, the brightest of Leo. Leo himself is strolling westward. The Sickle types his entrance leg, chest, mane, and a part of his head. Off to the left, a lengthy proper triangle types his hind finish and lengthy tail.■ Spot brighter Procyon almost 4 fists to the decrease proper of Regulus. About midway alongside that line and simply a bit under, search for the dim head of Hydra, the Sea Serpent.


■ The Moon shines in central Gemini this night underneath Pollux and Castor, forming a lengthy, tall triangle with them. Farther left of the Moon is Procyon. Much farther proper of the Moon is Capella.

■ At this time of 12 months, the 2 Dog Stars stand vertically aligned in late twilight. Look straight southwest. Brilliant Sirius in Canis Major is under, and Procyon in Canis Minor is excessive above. They’re roughly two fists aside.

■ This can be when, because the final of twilight fades away, the bowl of the dim Little Dipper extends straight to the appropriate of Polaris within the north.■ And excessive above the top-stars of the Little Dipper’s bowl, you will discover the top-stars of the Big Dipper’s bowl. That pair is sort of twice as huge aside.


■ First-quarter Moon (precise at 2:59 a.m. EDT). Look excellent of the Moon for Pollux and Castor almost lined up with it. Lower left of the Moon shines Procyon.


■ This night, use binoculars to select M44, the Beehive star cluster, about 4° or so under the Moon. That’s roughly two-thirds or three-quarters the width of a typical binocular’s subject of view. This a lot moonlight is hardly best for viewing a deep-sky object, however the Beehive stars are usually not tough in binocs, and the Moon does make a very useful reference level to begin from.

■ Arcturus shines brightly within the east these evenings. It’s the sharp finish of a lengthy, slender kite-formed asterism shaped by the brightest stars of Bootes, the Cowherd. The kite is presently mendacity on its facet, extending to Arcturus’s left. The head of the kite, at the far left, is bent barely upward. The kite is 23° lengthy: about two fist-widths at arm’s size.


■ The Moon this night type an isosceles triangle with Regulus and Algieba (Gamma Leonis), the second-brightest star of Leo’s Sickle, as proven under. The precise peak of the isosceles triangle will rely in your longitude, for the reason that Moon strikes eastward by an considerable quantity every hour.The scenes listed below are all the time plotted precise for an observer close to the center of North America, at latitude 40° N, longitude 90° W. If you are close to the East Coast the Moon will probably be simply a little to the appropriate of the place it is plotted under. On the West Coast the Moon will seem a little left of the place plotted.By how a lot? Measure by the truth that the hole between the 2 Moons under is 24 hours of lunar movement.

The Moon passes between Regulus and Algieba (the orange star above Regulus) between the North American evenings of Wednesday and Thursday, April 21st and 22nd. (The Moon is drawn about thrice its precise obvious dimension.)■ In the early-morning hours of Thursday the Lyrid meteor bathe, often weak however typically unpredictable, ought to at its most exercise. The mild of the waxing gibbous Moon will intervene till the Moon units about an hour earlier than the primary glimmer of daybreak. That darkish hour is one of the best window to plan for. See Robert Lunsford’s Viewing the Lyrids in 2021.


■ Now the Moon types a triangle with Regulus and Algieba on their left facet slightly than their proper facet, as proven above.This new triangle is sort of completely equilateral across the time twilight ends within the Eastern and Central time zones.


■ The Arch of Spring. As evening descends, look excessive within the west for Pollux and Castor lined up virtually horizontally relying in your latitude. These two stars, the heads of the Gemini twins, type the highest of the large Arch of Spring. To their decrease left is Procyon, the left finish of the Arch. Farther to their decrease proper is the opposite finish, shaped by Menkalinan (Beta Aurigae) after which good Capella.

This spring the Arch has an intruder: little Mars. Tonight you will discover Mars the identical distance decrease proper from the Castor-Pollux pair as it’s decrease left from Capella. The complete array sinks within the west via the night.

Modern skywatchers are usually not alone in seeing the Arch of Spring as one massive asterism. Extend it down previous Procyon so as to add Sirius, and you have got the Hawai‘ian Canoe-Bailer of Makali‘i. Looks sufficiently big to bail the ocean.

■ The Moon shines on the other facet of the sky after darkish. Look higher left of the Moon by lower than fist at arm’s size for 2nd-magnitude Denebola, the tail star of Leo.

Nearly 4 fists left of the Moon shines brighter Arcturus, magnitude 0, the main mild of Bootes.


■ This night Arcturus shines about three fists left of the Moon.

And look under the Moon by hardly greater than half that distance, and maybe a bit left, to search out Spica, the main mild of Virgo.


This Week’s Planet Roundup

Mercury and Venus stay buried within the sundown, however not for lengthy. Next week they will begin rising into low twilight view collectively.

Mars (magnitude +1.4, crossing from Taurus into Gemini) shines within the west after darkish. In a telescope Mars is a mere 5 arcseconds huge, simply a tiny shimmering blob.

Jupiter and Saturn (each in dim Capricornus) are low within the southeast simply earlier than and through early daybreak. Jupiter grabs the attention at magnitude –2.1. Saturn glows a thirteenth as vibrant at magnitude +0.7. Catch Saturn a little greater than a fist at arm’s size to Jupiter’s proper or higher proper earlier than daybreak grows too vibrant.

Jupiter’s Great Red Spot facet, imaged on April third by Christopher Go from his tropical latitude of 10° north. The darkish dot shouldn’t be a moon’s shadow however darkish Callisto itself, caught in a uncommon equatorial transit throughout Jupiter.South right here is up. The northern two thirds of the Equatorial Zone are pale orange tan slightly than white. Bordering the Equatorial Zone on the north is the darkish purple fringe of the North Equatorial Belt.Uranus and Neptune stay hidden low in night and morning twilight, respectively.

All descriptions that relate to your horizon — together with the phrases up, down, proper, and left — are written for the world’s mid-northern latitudes. Descriptions that additionally rely on longitude (primarily Moon positions) are for North America.

Eastern Daylight Time, EDT, is Universal Time minus Four hours. Universal Time is also referred to as UT, UTC, GMT, or Z time. To grow to be extra skilled about time techniques than 99% of the folks you will ever meet, see our compact article Time and the Amateur Astronomer.

Want to grow to be a higher astronomer? Learn your means across the constellations. They’re the important thing to finding all the things fainter and deeper to hunt with binoculars or a telescope.

This is an out of doors nature passion. For a simple-to-use constellation information protecting the entire night sky, use the large month-to-month map within the middle of every difficulty of Sky & Telescope, the important journal of astronomy.

Once you get a telescope, to place it to good use you will want a detailed, massive-scale sky atlas (set of charts). The fundamental normal is the Pocket Sky Atlas (in both the unique or Jumbo Edition), which exhibits stars to magnitude 7.6.

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and a whole lot of telescopic galaxies, star clusters, and nebulae amongst them. Shown right here is the Jumbo Edition, which is in exhausting covers and enlarged for simpler studying outdoor by purple flashlight. Sample charts. More in regards to the present editions.Next up is the bigger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; almost thrice as many. The subsequent up, as soon as you already know your means round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And you’ll want to learn the way to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, corresponding to Sky Atlas 2000.0 Companion by Strong and Sinnott, or the larger (and illustrated) Night Sky Observer’s Guide by Kepple and Sanner.

Can a computerized telescope substitute charts? Not for novices, I do not suppose, and never on mounts and tripods which are lower than high-high quality mechanically, that means heavy and costly. And as Terence Dickinson and Alan Dyer say of 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.”

Audio sky tour. Out underneath the night sky with yourearbuds in place, hearken to Kelly Beatty’s monthlypodcast tour of the heavens above. It’s free.

“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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