This Week’s Sky at a Glance, Aug. 27 – Sept. 4

RS Ophiuchi slows its fading. On August eighth the recurrent nova RS Ophiuchi lept from its regular magnitude 11.2 to 4.8, dim naked-eye brightness, after 15 years of simmering quietly close to minimal. It fading quickly at first, then way more slowly. As of August twenty sixth it had remained about magnitude 8.0 for 4 days and was reddening. See Bob King’s Recurrent Nova RS Ophiuchi Just Blew its Top! with finder charts and comparability stars. Ophiuchus is ideally positioned excessive within the early night sky.

Nova Cassiopeiae 2021, in the meantime, has bounced round in brightness ever because it erupted from fifteenth magnitude to 7.7 final March. Its greatest bumps have been to magnitude 5.5 in early May and 6.0 round July twenty seventh. As of August twenty sixth it additionally had been holding at 8.0 for a number of days, after it dipped to eight.6 earlier in August. Cassiopeia too is excellently positioned within the night sky. Charts and comparison stars.


■ Whenever vivid Vega crosses nearest your zenith, because it does quickly after darkish now, you recognize the Sagittarius Teapot is at its highest due south.

Two hours later when Deneb crosses closest to the zenith, it is the flip of little Delphinus and boat-shaped Capricornus down under it to face at their highest due south. This season, after all, Capricornus is way outshone its company Jupiter and Saturn.

Week by week Jupiter and Saturn come into sight ever greater in twilight, as seen right here.


■ Now that the Moon is out of the night sky, this week is prime Milky Way time! After darkish, the Milky Way runs from Sagittarius within the south, up and a bit left left throughout Aquila and Cygnus excessive overhead, and on down via Cassiopeia to Perseus low within the north-northeast.

Cygnus sports activities the Cygnus Star Cloud, one of many Milky Way’s richest areas. Explore in depth all via right here with binoculars or a small scope utilizing Matt Wedel’s “Touring Cygnus with Binoculars” article and massive chart within the September Sky & Telescope, beginning on web page 34.

Though the waning moon is gone from the early night sky, it is very a lot current from the nighttime via daybreak. Watch it march throughout Taurus from Sunday via Tuesday mornings.


■ Last-quarter Moon tonight (precisely last-quarter at 3:13 a.m. August thirtieth EDT). The Moon rises round 11 or midnight native time. It’s in Taurus, between the Pleiades cluster above it and, as soon as it climbs excessive sufficient, orange Aldebaran under it. By early daybreak on the thirtieth the scene shifts considerably, as proven above.


■ Late these evenings as autumn approaches, Fomalhaut, the Autumn Star, makes its inevitable look above the southeast horizon. Its rising time will depend upon the place you reside. But by about 10 or 11 p.m. you should not have any hassle recognizing it low within the southeast; simply discover an open view in that course. This year Fomalhaut is less complicated to find than regular: Look about two fists under Jupiter and a bit left.


■ An indication of the advancing season: Cassiopeia is excessive within the northeast, its W sample tilting up. And under it, starry Perseus is reaching up.

The highest a part of Perseus consists of the wintry Double Cluster. To discover it, look under the bottom two stars of the Cassiopeia W (they’re the faintest two), by considerably extra that the gap between them. You’re searching for what looks as if a small spot of enhanced Milky Way glow. Binoculars or a finderscope will provide help to detect the Double Cluster even via a truthful quantity of sunshine air pollution. The pair is a glory in a telescope.


■ As August wanes and nights start to show chilly, the Great Square of Pegasus looms up within the east, balancing on one nook. Its stars are solely 2nd and third magnitude, and your fist at arm’s size suits inside it.

From the Square’s left nook extends the principle line of the constellation Andromeda: three stars (together with the nook) about as vivid as these forming the Square.

This entire large sample was named “the Andromegasus Dipper” by the late Sky & Telescope columnist George Lovi. It’s formed type of like a large Little Dipper with an extra-big bowl, and it is at present lifting its contents upward.


■ The precise Little Dipper, in the meantime, is tipping over leftward within the north. It’s solely 40% so long as the Andromegasus Dipper, and most of it’s a lot fainter. As all the time, you may discover that it is oriented greater than 90° counterclockwise in comparison with Andromegasus. It’s at present dumping its contents out.

■ Low within the northwest or north at the tip of summer season twilights, would you acknowledge noctilucent clouds if you happen to noticed them? They’re probably the most astronomical of all cloud varieties, with their excessive altitude and formation on meteoric mud particles. And they’re pretty uncommon — although turning into extra frequent in current years because the ambiance adjustments. See Bob King’s article.

■ Before and through early daybreak Friday morning the third, the waning crescent Moon hangs under Castor and Pollux within the east. Far to the appropriate of this tableau, Orion has already risen excessive to warn that winter is coming.

Look far beneath Orion for Sirius. Between Sirius and the Moon shines Procyon.


■ The coming of September implies that Scorpius, the proudly starring constellation of the southern sky in July, is tilting over and mendacity low within the southwest after darkish, getting ready to mattress down and drift off for the season.

The skinny waning Moon steps down within the east-northeast within the dawns of Saturday and Sunday September 4th and fifth. On the sixth, shortly earlier than dawn, it can nearly actually be too low and slim to detect even with binoculars or a telescope, even when the air could be very clear; the Moon might be solely about 16 hours from new for East-Coast crescent hunters, and solely about 13 hours from new earlier than dawn within the Pacific time zone.


■ Look fastidiously at Venus low within the west-southwest as twilight fades. Tonight Spica, only one/100 as vivid, glimmers 1.8° to Venus’s decrease left.

Tomorrow they’re going to be 1.6° aside.


This Week’s Planet Roundup

Mercury (magnitude 0.0) could be very deep within the sundown, about 16° decrease proper of Venus all week. You may have a likelihood at it with binoculars or a wide-field scope. About 15 or 20 minutes after sundown, scan for it simply above your horizon due west. Good luck.

Venus, good at magnitude –4.0, shines vivid white within the west-southwest throughout twilight. It nonetheless units round twilight’s finish.

Jupiter and Saturn shine within the southeast in late twilight and after darkish. They’re magnitudes –2.9 and +0.3, respectively, in Capricornus.

Jupiter begins the night lowest. Saturn glows 18° (about two fists) to Jupiter’s higher proper. The pair ranges out round 10 p.m. daylight-saving time. By then they’re nearing their highest within the south, at their telescopic greatest.

Saturn reached opposition on August 1st, Jupiter on August nineteenth. So they’re nonetheless almost at their closest, greatest, and brightest of the year. See “Saturnian Challenges” beginning on web page 52 of the July Sky & Telescope, additionally “Dog Days with the Gas Giants” on web page 40 of August.

Three satellites on Jupiter, two shadow transits, and extra! “The day I have been waiting for all year has finally come,” wrote Christopher Go from the Philippines on August fifteenth. “Today we had a grand slam event. A very rare triple transit on Jupiter with the moons Callisto, Ganymede and Europa in transit. As a bonus, a partially eclipsed Io was seen just before it went behind Jupiter. After the triple transit there was a very rare event when Ganymede occulted Europa followed by Ganymede eclipsing Europa! Seeing the shadow of Ganymede over Europa was surreal! Everything went PERFECTLY. Seeing was incredible and the sky was totally clear!” In the photographs right here, north is up.

But one of the best way to comply with the sequence of occasions is by video! The Washington Post put all of it collectively together with a step-by-step information to every part that is taking place. Here’s the story: Watch this ‘surreal’ Jupiter eclipse that you probably missed.

Saturn on July 25, 2021
Saturn on July twenty fifth. North is up. This beautiful stacked-video picture exhibits element within the broad B Ring, in addition to the skinny Encke Gap simply contained in the outer fringe of the outer A Ring. Saturn’s Equatorial Zone is vivid as regular, and its North Equatorial Belt is distinct. The slim darkish band seemingly on the opposite aspect of the Equatorial Zone is definitely the dim, inside C ring. Agapios Elia of Nicosia, Cyprus, took video throughout 45 minutes on July twenty fifth utilizing a 9.25-inch Schmidt-Cassegrain scope. He de-rotated the globe throughout processing after which stacked giant numbers of the of greatest frames.

Uranus (magnitude 5.7, in Aries) and Neptune (magnitude 7.8, at the Aquarius-Pisces border) are excessive within the southeast to south within the early-morning hours.

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 also referred to as UT, UTC, GMT, or Z time. To develop into extra knowledgeable about time methods 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 every part fainter and deeper to hunt with binoculars or a telescope.

This is an out of doors nature interest. For an easy-to-use constellation information protecting the entire night sky, use the massive month-to-month map within the heart of every challenge 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 exhibits 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 onerous 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 3 times as many. The subsequent up, as soon as you recognize your way round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And you should definitely learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, similar 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 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 beneath the night sky together with your
earbuds in place, take heed 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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