This Week’s Sky at a Glance, April 23 – May 1

Novae replace:   Nova Cassiopeiae 2021 (V1405 Cas) was nonetheless holding at about magnitude 7.8 as of April twenty third. It’s been about like that ever because the day after its March 18th discovery, with solely a very slight fade and rebrightening within the interim. But it has sunk low within the north after dusk, particularly for observers at southerly latitudes, so that you’re higher off catching it when it is greater within the north-northeast earlier than the beginning of daybreak. For charts see Bright Nova Erupts in Cassiopeia.

That’s fairly in contrast to the more moderen Nova Sagittarii 2021 No. 2 (V6595 Sgr) and Nova Scorpii 2021 (V1710 Sco). Both of these have light from magnitude 8 or 8.5 at discovery to 11 or 11.5. See A Bouquet of Novae Brightens April Nights.

Comet ATLAS continues at about ninth magnitude. It’s now crossing Corona Borealis and Bootes in effective, excessive view within the east by late night. See Make the Most of Comet ATLAS.


■ Venus and Mercury are starting their twilight emergence simply above the west-northwest horizon, as proven under, however they’re nonetheless being very shy about it. Start in search of them there with binoculars about quarter-hour after sundown. The farther north you’re the higher.

Can you catch Venus and maybe Mercury but? Scan with binoculars simply above the west-northwest horizon beginning about quarter-hour after sundown. Their visibility is exaggerated right here.
Five days later Mercury and Venus are considerably simpler.

These scenes are drawn for latitude 40° north. That’s the place Mercury and Venus will seem lined up vertically as proven right here on April thirtieth. At totally different latitudes, you may discover them tilted by about the identical angle that your latitude differs from 40°.

The Arch of Spring. As night time descends, look very 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 big Arch of Spring. To their decrease left is Procyon, the left finish of the Arch. Farther to their decrease proper is the opposite finish, fashioned by Menkalinan (Beta Aurigae) after which sensible Capella.

This spring the Arch has an intruder: little Mars. It’s not fairly midway from Capella to Procyon and, for a lot of the week, a little under that line. The complete array sinks within the west by way of the night.

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

Nearly 4 fists left or decrease 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 brightest star of Virgo.


■ Look to the decrease proper of the Moon, by about 6°, for Spica.

Several instances farther to their higher left shines brighter Arcturus.

And Vega, the Summer Star the zero-magnitude equal of Arcturus is now twinkling low within the northeast after dusk. . . relying in your latitude. The farther north you’re the greater will probably be. If you are within the latitudes of the southern US, you may have to attend till a bit later after darkish for it to look.


■ Spot little Mars within the toes of Gemini practically due west after darkish. Find it a bit lower than midway from Capella to Procyon and, for many of this week, a little decrease.

This night use a telescope (what with the intense moonlight!) to search for the open cluster M35 simply ½° to Mars’s left.

Mars glows at the trailing foot of Castor.

■ Full Moon (precise at 11:32 p.m. EDT). The Moon shines in Virgo, with Spica a few levels to its decrease proper and brighter Arcturus a lot farther to its higher left.


■ This night M35 is ¾° under or decrease left of Mars. The moonlight stays brilliant.


Now you’ve got acquired a dark-sky window of about a half hour between the top of twilight and moonrise (relying in your latitude) to see M35 freed from moonlight in all its glory. It’s now 1.1° under Mars.

■ By midnight tonight the waning gibbous Moon is up within the southeast. Orange Antares is about 4° to its decrease proper. How a lot else of higher Scorpius are you able to see to the precise of the Moon?

By the daybreak of Wednesday the twenty ninth, the Moon shines above Antares.


■ Face north simply after dusk, look very excessive, and you will find the Pointers, the top stars of the Big Dipper’s bowl, on the meridian pointing towards Polaris straight down under. From the Pointers to Polaris is about three fists at arm’s size.


■ Arcturus is the brightest star excessive within the east these evenings. Spica shines decrease proper of it by about three fists at arm’s size. To the precise of Spica by half that distance is the distinctive four-star constellation of Corvus, the springtime Crow.


■ Even although May has begun, wintry Sirius nonetheless twinkles very low within the west-southwest at the top of twilight. It units quickly after. How for much longer into the spring can you retain Sirius in view? In different phrases, what will probably be its date of “heliacal setting” as seen by you? The farther north you’re, the earlier Sirius is gone for the season.


This Week’s Planet Roundup

Mercury and Venus start rising collectively from deep within the sundown. Reader Tony on northerly Vancouver Island (latitude about 48° N) known as Venus “easy” in 16x50 binoculars on the seventeenth. On Sunday the twenty fifth search for Mercury 1.2° to Venus’s higher proper, as proven at the highest of this web page. Venus is magnitude –3.9, and Mercury is unusually brilliant at –1.6.

Start trying as early as quarter-hour after sundown to catch their transient window of visibility between when the sky is simply too brilliant and the planets get too low and disappear into the atmospheric extinction. The precise greatest time after sundown will rely in your latitude (the farther north the higher) and the readability of the air.

Both planets are a little greater and simpler every night, Mercury particularly. By Friday the thirtieth, Mercury stands 4.5° above Venus. Venus will keep its brightness, however Mercury by then will probably be all the way down to magnitude –1.1.

Mars (magnitude +1.5, in Gemini at the texture of the Castor determine) glows within the west after darkish. It’s a little lower than midway from Capella to Procyon and, for a lot of the week, a bit under that line. In a telescope it is a mere 5 arcseconds extensive: simply a tiny shimmering blob.

Jupiter and Saturn (at dim Capricornus) rise greater than an hour earlier than the primary mild of daybreak. As daybreak begins, spot them low within the southeast. Jupiter grabs the attention at magnitude –2.2. Saturn is 15° to Jupiter’s proper or higher proper, one fifteenth as brilliant at magnitude +0.7.

Jupiter on April thirteenth. South right here is up. “I finally had clear skies and better seeing conditions,” writes Christopher Go from his latitude of 10° N. “The Great Red Spot halo is very dark.” And be aware the way it curls farther across the Red Spot than in his picture 10 days earlier, under.

The South Equatorial Belt following (proper of) the Red Spot is unusually pale. The Equatorial Zone continues to indicate advanced tan patterns throughout its northern two-thirds, and the south fringe of the North Equatorial Belt is darkish red.

An picture by Go from April third. The darkish dot is just not a moon’s shadow however darkish Callisto itself, caught in a uncommon equatorial transit throughout Jupiter.

Uranus and Neptune are hidden within the glare of the Sun.

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 4 hours. Universal Time is often known as UT, UTC, GMT, or Z time. To develop into extra knowledgeable about time methods than 99% of the folks you may ever meet, see our compact article Time and the Amateur Astronomer.

Want to develop into a higher astronomer? Learn your way across the constellations. They’re the important thing to finding every little thing fainter and deeper to hunt with binoculars or a telescope.

This is an out of doors nature pastime. For an easy-to-use constellation information masking the entire night sky, use the large month-to-month map within the heart of every situation of Sky & Telescope, the important journal of astronomy.

Once you get a telescope, to place it to good use you may want a detailed, large-scale sky atlas (set of charts). The primary customary is the Pocket Sky Atlas (in both the original or Jumbo Edition), which reveals stars to magnitude 7.6.

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and tons of 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 open air by red flashlight. Sample charts. More about the current editions.

Next up is the bigger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; practically 3 times as many. The subsequent up, as soon as your way round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And remember to learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, resembling (*23*) by Strong and Sinnott, or the larger (and illustrated) Night Sky Observer’s Guide by Kepple and Sanner.

Can a computerized telescope exchange charts? Not for inexperienced persons, I do not assume, and never on mounts and tripods which might be lower than top-quality mechanically, which 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 below the night sky along with your
earbuds in place, hearken to Kelly Beatty’s month-to-month
podcast 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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