This Week’s Sky at a Glance, July 9 – 17

Nova Cas continues wobbly. It’s been almost 4 months since Nova Cassiopeiae 2021 erupted to magnitude 7.7. It has stayed roughly that brilliant ever since (making it formally a “slow nova”) apart from swelling to five.3 for a week in May. Recently it has been wavering. As of July eighth it was about 7.8, having instantly dropped from a mini-peak of 6.6 the week earlier than.

It’s pretty effectively up within the north-northeast after darkish, relying in your latitude. It climbs excessive later within the evening. See Bob King’s replace: Noctilucent Cloud Show, a Mercurial Nova, and More, with charts and comparability stars.


■ Venus continues to shine low within the west-northwest throughout twilight. Mars, only one/200 as brilliant, is 2° to its higher left this night; binoculars assist. They set earlier than twilight’s finish.

Watch the 2 planets shut in to their conjunction about ½° aside on July twelfth and thirteenth.

■ New Moon (precise at 9:17 p.m. EDT).

■ When twilight ends, you may discover the 2 brightest stars of summer season, Vega and Arcturus, about equally close to the zenith: Vega towards the east, Arcturus towards the southwest (relying in your location).

About a third of the way from Arcturus to Vega is the faint semicircle of Corona Borealis, the Northern Crown, with its modestly brilliant crown jewel, Alphecca or Gemma, on its entrance.

Nearly two thirds of the way from Arcturus to Vega is the Keystone of Hercules.

For extra see Fred Schaaf’s “The Path from Arcturus to Vega” within the July Sky & Telescope, web page 45.


■ If you may have a darkish sufficient sky on these previous couple of moonless nights for a whereas, search for the Milky Way forming a magnificent arch excessive throughout the entire japanese sky. It runs all of the way from under Cassiopeia within the north-northeast, up and throughout Cygnus and the underside of the Summer Triangle within the east, and down previous the spout of the Sagittarius Teapot within the south.


■ A really skinny crescent Moon hangs a few levels to the best of Venus (and faint little Mars) low within the west-northwest throughout twilight, as proven under.

If you may see Mars (deliver binoculars), you may undoubtedly see brighter Regulus twinkling 12° to Venus’s higher left.

The new crescent Moon steps up low in twilight simply as Venus and Mars undergo conjunction. (The Moon is drawn about thrice its precise obvious dimension.)


■ Big, macho Venus, Goddess of Love, and wimpy little Mars, God of War, are at their closest collectively now, about ½° aside, low within the west-northwest in twilight. The crescent Moon shines higher left of them this night, as proven above.

Look for Regulus a little much less far left or decrease left of the Moon.


■ Mars is now ½° underneath Venus. The Moon has thickened and moved farther to their higher left. Regulus is about halfway between them, as proven above.


■ The ever-waxing Moon is now decrease left of Denebola, Leo’s 2nd-magnitude tail tip. They’re lower than a fist at arm’s size aside.

The brighter star way off three fists left of the Moon is 1st-magnitude Spica.


■ With the advance of summer season the Sagittarius Teapot, within the south-southeast decrease left of Scorpius after darkish, is beginning to tilt and pour from its spout to the best. The Teapot will tilt farther and farther for the remainder of the summer season — or for a lot of the evening if you happen to keep out late.


■ In late twilight, Spica shines three of 4 finger-widths decrease left of the first-quarter Moon (precisely first-quarter at 6:11 a.m. EDT Saturday morning the seventeenth). High above them is brighter Arcturus, tinted with a decrease colour temperature (yellow-orange).

Now Mars strikes away decrease proper of Venus, whereas brighter Regulus houses in from the higher left. Regulus will go 1° from Venus on the night of the twenty first.

■ The tail of Scorpius is low due south proper after darkish, to the decrease proper of the Sagittarius Teapot. How low is dependent upon how far north or south you reside: the farther south, the upper.

Look for the 2 stars particularly shut collectively within the tail. These are Lambda and fainter Upsilon Scorpii, often called the Cat’s Eyes. They’re canted at an angle; the cat is tilting his head a little to the best and winking (Upsilon is fainter than Lambda; they’re magnitude 1.6 and a couple of.6). Both are blue-white supergiants, 700 and 500 gentle years away, respectively. Yes, the nearer of the 2 is fainter.

Between the Cat’s Eyes and the Teapot’s spout are the open star clusters M6 and particularly M7, showy in binoculars.

A line by the Cat’s Eyes factors west (proper) by almost a fist-width towards Mu Scorpii, a a lot tighter pair often called the Little Cat’s Eyes. They’re oriented nearly precisely the identical way as Lambda and Upsilon. Can you resolve the Mu pair with out utilizing binoculars?


■ The Moon remains to be basically first-quarter this night (at the night instances for the Americas). Spot Spica a fist to the Moon’s decrease proper, and Arcturus thrice as far to the Moon’s higher proper.

■ Cassiopeia is now effectively previous its bottoming-out for the year as seen quickly after darkish. Look for its tilted W sample low within the north-northeast. The farther north you reside, the upper it will likely be.



This Week’s Planet Roundup

Mercury glimmers very low within the east-northeast as daybreak grows brilliant. It sinks a little decrease this week however doubles in brightness, from magnitude 0.0 to –0.7. Binoculars assist.

Don’t confuse Mercury with Aldebaran more and more far to its higher proper, to not point out Capella even farther higher left.

Venus (magnitude –3.9) continues to shines low within the west-northwest throughout twilight. Right close to it’s tiny Mars, 200 instances fainter at magnitude +1.8. They seem closest, about ½° aside, at conjunction on July twelfth and thirteenth. By the sixteenth Mars is 2° to Venus’s decrease proper. Both planets proceed to set earlier than twilight ends.

Farther higher left of Venus you may discover Regulus, transferring nearer to Venus daily. It’s a half magnitude brighter than Mars.

Saturn (magnitude +0.3, in Capricornus) and brighter Jupiter (magnitude –2.7, in Aquarius) rise within the east-southeast a little later: Saturn across the finish of twilight, brighter Jupiter an hour later to Saturn’s decrease left. They’re highest within the south, at their telescopic finest, round 3 a.m. daylight saving time. See “Action at Jupiter” within the July Sky & Telescope, web page 50, and “Saturnian Challenges,” web page 52.

Both attain opposition in August.

Before daybreak, look 20° decrease left of Jupiter for Fomalhaut, now forming an nearly excellent isosceles proper triangle with Jupiter and Saturn. Jupiter is at the best angle.

Two darkish red barges have been close to Jupiter’s central meridian when Christopher Go took this picture on June fifteenth (at 19:03 UT, when the System II longitude of the central meridian was 79°). The remainder of the North Equatorial Belt has light significantly, apart from a very darkish red line alongside its southern edge. (South is up.) Meanwhile, the usually white Equatorial Zone largely stays a pale, nearly belt-like tan colour.

Uranus (magnitude 5.8, in Aries) is effectively up within the east simply earlier than daybreak begins.

Neptune (magnitude 7.9, in Aquarius 21° east of Jupiter) is increased within the south-southeast simply earlier than daybreak begins.

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 also called UT, UTC, GMT, or Z time. To turn out to be extra skilled about time programs than 99% of the folks you may ever meet, see our compact article Time and the Amateur Astronomer.

Want to turn out to be a higher astronomer? Learn your way across the constellations. They’re the important thing to finding the whole lot fainter and deeper to hunt with binoculars or a telescope.

This is an outside nature interest. For an easy-to-use constellation information protecting 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.

Pocket Sky Atlas cover, Jumbo edition
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 laborious covers and enlarged for simpler studying outside 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; almost thrice 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 make sure you learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, corresponding to (*17*) 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 novices, I do not assume, and never on mounts and tripods which are lower than top-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 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

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart