This Week’s Sky at a Glance, July 2 – 10

Nova Cas will get jumpy. It’s been 3½ months since Nova Cassiopeiae 2021 erupted to magnitude 7.7 in mid-March. It has stayed roughly that shiny ever since (making it formally a “slow nova”) aside from briefly swelling to five.3, faint naked-eye visibility, for a week in May. It’s been wavering since then and sooner now. As of July 1 it was about 7.4, having dropped from 6.7 (a halving of brightness) in simply the earlier two days.

The nova is pretty properly up within the north-northeast after darkish relying in your latitude. It climbs larger later within the night time. See Bob King’s new replace: Noctilucent Cloud Show, a Mercurial Nova, and More, with charts and comparability stars for the nova.


■ Venus continues to shine low within the west-northwest throughout twilight. Mars, just one/175 as shiny, is now simply 6° to its higher left as proven under. They set earlier than twilight’s finish.

Watch the 2 planets shut in on one another daily. They’ll be in conjunction, ½° aside, on July twelfth and thirteenth.

Venus and Mars level a line to Regulus within the western twilight. The stars of the Beehive, behind Venus this night, are way too faint to be plotted. But they’re there. . . .
Mercury and Aldebaran low at dawn, July 3, 2021.
Mercury, low within the daybreak, will double in brightness this week. Can you see it but? The visibility of faint factors in shiny twilight is exaggerated right here!


■ Low within the northwest or north at the tip of those lengthy summer time twilights, would you acknowledge noctilucent clouds for those who noticed them? They’re essentially the most astronomical of all cloud varieties, what with their excessive altitude and their formation on, partially, meteoric mud particles. And they’re pretty uncommon — although they’ve develop into extra frequent in latest years because the local weather and the ambiance change, significantly the ambiance’s methane content material. See Bob King’s Noctilucent Cloud Show, a Mercurial Nova, and More.

■ After darkish, the Summer Triangle holds sway on the jap aspect of the sky. Its prime star is Vega, the brightest. The brightest star to Vega’s decrease left is Deneb. Farther to Vega’s decrease proper is Altair. The Milky Way (if in case you have a darkish sufficient sky) runs throughout contained in the Triangle’s decrease edge.

■ As night grows late and even Altair rises excessive, look left of Altair, by hardly greater than a fist, for the compact little constellation Delphinus, the Dolphin.

Did you get it? Then strive for even fainter, smaller Sagitta, the Arrow. It’s to Altair’s higher left simply a little nearer. The Arrow factors towards decrease left, previous the nostril of Delphinus.


■ Star colours are largely refined, and completely different individuals have a better or more durable time seeing them. To me, the tints of shiny stars present a little higher on a late-twilight sky background than in a absolutely darkish sky.

For occasion, the 2 brightest stars of summer time are Vega, excessive within the east in late twilight, and Arcturus, even larger within the southwest. Vega is white with simply a contact of icy blue. Arcturus is a yellow-orange large. Do their colours stand out a little higher for you in late twilight than in darkish night time?

Binoculars, after all, all the time make star colours a lot simpler.


■ As daybreak begins on Monday morning the sixth, the waning crescent Moon hangs between the Pleiades above it and Aldebaran under it, as proven under.

The waning crescent Moon poses above Aldebaran and Mercury on the mornings of, respectively, July sixth and seventh.


■ Look for Mercury, low however persevering with to brighten, under the skinny Moon as daybreak brightens on Wednesday morning the seventh as proven above.


■ Antares and the remainder of starry Scorpius are at their highest within the south simply after these lengthy July twilights lastly fade away.

The head of Scorpius is the near-vertical row of three stars higher proper of Antares. Three high-quality doubles stars await you right here. The prime star of the row is Beta Scorpii or Graffias, a high-quality binary for telescopes: separation 13 arcseconds, magnitudes 2.8 and 5.0.

Just 1° under it’s the very large naked-eye pair Omega1 and Omega2 Scorpii, diagonal from higher proper to decrease left. They’re 4th magnitude and ¼° aside. Binoculars present their slight shade distinction; they’re spectral varieties B9 and G2.

Upper left of Beta by 1.6° is Nu Scorpii, separation 41 arcseconds, magnitudes 3.8 and 6.5. In reality that is a telescopic triple. High energy in good seeing reveals Nu’s brighter part itself to be a shut double, separation 2 arcseconds, magnitudes 4.0 and 5.3, aligned virtually north-south.

And extra: In the identical binocular area with Antares, or almost so, are two very completely different globular star clusters for binoculars and telescopes. M4 is a huge, dim fuzzy comparatively close by for a globular. M80 is fainter and far more compact; actually it may be onerous to differentiate in binoculars from an Eighth-magnitude star. It’s a larger and denser cluster than M4 however greater than 4 instances as distant. Use the chart for them with Matt Wedel’s Binocular Highlight column within the July Sky & Telescope, web page 43.


■ With the advance of summer time, the Sagittarius Teapot, within the south-southeast decrease left of Scorpius after darkish, is beginning to tilt and pour from its spout to the precise. The Teapot will tilt farther and farther for the remainder of the summer time — or for a lot of the night time for those who keep out late.

■ Jupiter’s Great Red Spot ought to be on the planet’s central meridian round 2:45 a.m. Eastern Daylight Time. Around that point Callisto and Ganymede are each at their farthest east of the planet, whereas Io and Europa are shut in to Jupiter’s west. There, Europa disappears into eclipse by Jupiter’s shadow round 3:39 a.m. EDT.

For timetables of many extra the phenomena amongst Jupiter and its satellites this month, good worldwide, see the July Sky & Telescope, pages 50-51.


■ As twilight involves its finish, you may now discover the 2 brightest stars of summer time, Vega and Arcturus, 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 one modestly shiny 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.

■ New Moon (actual at 9:17 p.m. EDT).


■ If you will have a darkish sufficient sky on these moonless nights, the Milky Way now types a magnificent arch excessive throughout the entire jap sky. It runs all of the way from under Cassiopeia within the north-northeast, up and throughout Cygnus and the Summer Triangle within the east, and down previous the spout of the Sagittarius Teapot within the south.



This Week’s Planet Roundup

Mercury glimmers very low within the east-northeast as daybreak grows shiny. Mercury stays low all week however brightens from magnitude +0.8 to 0.0. Binoculars or a wide-field telescope will assist. Don’t confuse Mercury with faster-twinkling Aldebaran more and more far to its higher proper; see the illustration for July 3 above.

Venus (magnitude –3.8) shines low within the west-northwest throughout twilight. Tiny Mars, almost 200 instances fainter at magnitude +1.8, is closing in on Venus from the higher left. They’re separated by 6° on July 2nd, closing to 2° by the ninth. They’ll be in conjunction, ½° aside, on July twelfth and thirteenth. Both planets set earlier than twilight ends.

Saturn (in Capricornus) and brighter Jupiter (in Aquarius) present up by late night. Saturn rises across the finish of twilight. Jupiter comes up one hour later, to Saturn’s decrease left. They’re up in high-quality view after midnight, and so they’re highest within the south at their telescopic greatest within the hour earlier than daybreak begins. See “Saturnian Challenges” within the July Sky & Telescope, web page 52.

Jupiter dominates at magnitude –2.6. Saturn, 20° to Jupiter’s west (proper), is a extra modest +0.4. They’ll attain opposition in August.

Before daybreak, look 20° under or decrease left of Jupiter for Fomalhaut. It types an isosceles proper triangle with Jupiter and Saturn. Jupiter is at the (virtually) proper 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 pale vastly, aside from a very darkish red line alongside its southern edge. (South is up.) Meanwhile, the usually shiny Equatorial Zone largely stays a pale, virtually belt-like tan shade.

Uranus (magnitude 5.8, in Aries) is pretty low within the east earlier than daybreak begins.

Neptune (magnitude 7.9, in Aquarius 21° east of Jupiter) is properly up within the southeast 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 depend upon 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 skilled about time techniques than 99% of the individuals 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 all the things 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 middle 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 fundamental commonplace 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 tons of of telescopic galaxies, star clusters, and nebulae amongst them. Shown right here is the Jumbo Edition, which is in onerous covers and enlarged for simpler studying outdoor 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 to learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, comparable 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 rookies, 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 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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