This Week’s Sky at a Glance, July 30 – August 7

Nova Cas takes one other brightness bump! Nova Cassiopeiae 2021 erupted to magnitude 7.7 final March. It has stayed largely about that brilliant ever since making it a “slow nova” however with a brightness spike to five.5 in early May and smaller bumps since then. For a whereas it appeared executed for, however as of July twenty seventh UT it had climbed again as much as 6.0. Two day later it dropped to about 7.0. Charts and comparison stars.


■ As summer season progresses, Arcturus strikes down the western facet of the night sky. Arcturus kinds the underside level of the Kite of Bootes. The Kite, slightly slim, extends higher proper from Arcturus by 23°, about two fists at arm’s size. The decrease proper facet of the kite is dented inward, as if some celestial intruder as soon as banged into it.


■ On this Saturn-day, Saturn is at some point earlier than opposition. Do you discover that Saturn’s rings are distinctly brighter, in comparison with Saturn’s globe, than they normally are? This Seeliger effect is attributable to the strong ring particles backscattering sunlight to us when the Sun is nearly instantly behind us. The dusty surfaces of the Moon and Mars do that too, however Saturn’s clouds don’t. In the case of Saturn the impact is known as for Hugo von Seeliger, who studied it intimately and revealed his findings in 1887.

■ Last-quarter Moon (actual at 9:16 a.m. EDT). By the time the Moon rises late tonight, round midnight or 1 a.m. native daylight saving time, its terminator might be now not precisely straight however very barely concave. Look about 15° above the Moon for the brightest stars of Aries, 2nd and Third magnitude.

By the very first trace of daybreak Sunday morning the Moon might be fairly excessive. Spot the Pleiades to its left, Aldebaran a comparable distance under the Pleiades, and the a lot looser Hyades simply above and proper of Aldebaran.


Saturn is at opposition, reverse the Sun as seen from Earth. This year Saturn’s rings are tilted 18° to our line of sight a lot lower than their most tilt of 26°, which they displayed from 2016 by means of 2018, however nowhere close to the edge-on side they may current in 2025. But their present middling tilt appears (to me anyway) to make Saturn look probably the most characteristically Saturnlike.

Today is Lammas Day or Lughnasadh, one of many 4 conventional “cross-quarter” days halfway between the solstices and the equinoxes. Sort of. In the various centuries after this custom took maintain in Europe the calendar drifted with respect to nature’s seasons, till our present Gregorian calendar was instituted a few centuries in the past to cease such issues. So in 2021, the midpoint between the June solstice and the September equinox really falls on August sixth, at 5:02 p.m. Eastern Daylight Time (21:02 UT).

That minute is the precise center-balance of astronomical summer season: the very prime of the circle of the year (as outlined by the astronomical seasons, for the Northern Hemisphere.)


■ With the advance of summer season the Sagittarius Teapot, within the south after darkish now, is tilting and pouring from its spout to the proper. The Teapot will tilt farther and farther for the remainder of the summer season — or for a lot of the night time when you keep out late.

■ Tonight, telescope customers can watch Jupiter’s moon Europa slowly disappear into eclipse by Jupiter’s shadow round 12:29 a.m. EDT. Following behind is Io, which can likewise disappear into Jupiter’s shadow round 2:19 a.m. EDT. (Subtract 1 hour from these to get CDT, and so forth.)

Earlier within the night time, Jupiter’s Great Red Spot ought to cross Jupiter’s central meridian round 10:24 p.m. EDT. The spot needs to be seen nearly as simply for about an hour earlier than and after, in a good 4-inch telescope if the atmospheric seeing is sharp and regular. A light-weight blue or green filter helps a bit.

The Red Spot transits about each 9 hours 56 minutes. But not fairly like clockwork! It drifts east or west in Jupiter’s environment considerably irregularly. A change typically turns into detectable to visible transit timers over a span of some months. Our transit-time predictions are primarily based on pretty latest observations, however do not be stunned if the Red Spot has taken it into its head to maneuver a couple of minutes off schedule.


Hunting Hebe. The asteroid 6 Hebe is a little previous opposition, a pinpoint of about magnitude 8.4 north of the Sagittarius Teaspoon. A pair of 10×50 or bigger binoculars, used with care and precision beneath a darkish sky, could be sufficient so that you can decide it out utilizing the finder chart within the July Sky & Telescope, web page 50. (The chart there reveals Hebe’s place for 0:00 UT on the dates indicated, which falls on the night of the earlier date for North America.)


■ If you employ a telescope a lot you are most likely acquainted with Lyra overhead, harboring Vega, the Double-Double, and the Ring Nebula amongst different sights. And close by is Albireo, the beak of Cygnus and one of many sky’s best gold-and-blue double stars.

But between Albireo and Lyra, what in regards to the much-overlooked globular cluster M56? At magnitude 8.3 you may even be capable to detect it with giant binoculars in a darkish sky. To pinpoint the spot, hone in with Matt Wedel’s “Lost in Space,” his Binocular Highlight column and chart for this lesser-known discover within the August Sky & Telescope, web page 43.

■ It will be the top of summer season, however wintry Gemini is arisen within the east by the point daybreak begins. The waning crescent Moon crosses it on Thursday and Friday mornings, August fifth and sixth, as proven under.

Most of the stars of Gemini have light into the rising mild of day by the point dawn is just 45 minutes away. You’ll do higher to look earlier when the constellation is decrease. If you do get outside on the late facet, binoculars will assist, and the waning Moon offers a reference. (The Moon positions listed below are, as at all times, actual for an observer in the course of North America.)


■ The Big Dipper hangs diagonally within the northwest after darkish. From its midpoint, look to the proper to seek out Polaris (not very brilliant) glimmering due north as at all times.

Polaris is the tip of the Little Dipper’s deal with. The solely different Little Dipper stars which can be even reasonably brilliant are the 2 forming the outer finish of its bowl: 2nd-magnitude Kochab and Third-magnitude Pherkad. On August evenings you will discover them to Polaris’s higher left (by about a fist and a half). They’re referred to as the Guardians of the Pole, since they ceaselessly circle round Polaris by means of the night time and thru the year.


■ Bright Vega passes closest to overhead round 10 or 11 p.m. now, relying on how far east or west you’re in your time zone.

How carefully it misses your zenith is determined by how far north or south you’re. It passes proper by means of your zenith when you’re at latitude 39° north (Washington DC, Cincinnati, Kansas City, Lake Tahoe). How carefully are you able to choose this simply by trying?

Deneb crosses closest to the zenith nearly precisely two hours after Vega. But to see Deneb precisely straight up it is advisable be farther north, at latitude 45°: Portland, Minneapolis, Montreal, southern France, northern Italy.


■ Have you been seeing any Perseids meteors but? For now you will solely see the very occasional Perseid throughout your observing classes, however their numbers are progressively rising. The bathe is because of peak late subsequent Wednesday night time, August 11, however occasional forerunners start displaying up as a lot as two or three weeks beforehand. Already the sky is moonlessly darkish. For extra on this year’s Perseids see the August Sky & Telescope, web page 48.

You’ll know it is nearly definitely a Perseid if, round this time of year, you hint its path backward far sufficient throughout the sky and discover that the road intersects the northern a part of Perseus.



This Week’s Planet Roundup

Mercury is hidden together with the Sun.

Venus (brilliant at magnitude –3.9) shines low due west throughout twilight. It units round twilight’s finish.

Mars is hidden deep within the sundown.

Jupiter (magnitude –2.8, in Aquarius) and Saturn (magnitude +0.2, in Capricornus) shine within the east-southeast after darkish. Jupiter begins the night time lowest, nevertheless it’s by far the brighter of the 2. Saturn glows yellowly 19° (about two fists at arm’s size) to Jupiter’s higher proper. The pair ranges out round midnight, relying in your date and placement. By then they’re almost at their highest within the south, at their telescopic finest.

Saturn reaches opposition on August 1st, Jupiter on August nineteenth, in order that they’re already primarily as shut and large as they will get this year. See “Saturnian Challenges” beginning on web page 52 of the July Sky & Telescope, additionally “Action at Jupiter” within the August issue, web page 50, and “Dog Days with the Gas Giants” on web page 49 of August.

Jupiter on July 12, 2021
Jupiter on July twelfth, imaged by Christopher Go. South is up. The South and North Equatorial Belts have largely diminished to slim darkish strains. Red barges and spots proceed simply north of the NEB. Much of the Equatorial Zone continues pale yellow-tan. The Great Red Spot is on the opposite facet of Jupiter, however observe the row of white ovals within the south temperate space.
Saturn on July 25, 2021
Saturn on July 25. North is up. This beautiful stacked-video picture reveals element within the broad A Ring, in addition to the skinny Encke Gap simply contained in the outer fringe of the outer B Ring. Agapios Elia of Nicosia, Cyprus, took video throughout 45 minutes on July 25, 2021, utilizing a 9.25-inch Schmidt-Cassegrain scope. He de-rotated the globe in processing and stacking giant numbers of the of finest frames.

Uranus (magnitude 5.7, in Aries) is excessive within the east-southeast earlier than daybreak begins.

Neptune (magnitude 7.8, at the Aquarius-Pisces border 23° east of Jupiter) crosses excessive within the 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 called UT, UTC, GMT, or Z time. To grow to be extra skilled about time methods than 99% of the individuals you will ever meet, see our compact article Time and the Amateur Astronomer.

Want to grow to be 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 pastime. For an easy-to-use constellation information protecting the entire night sky, use the massive month-to-month map within the heart of every problem of Sky & Telescope, the important journal of astronomy.

Once you get a telescope, to place it to good use you will want a detailed, large-scale sky atlas (set of charts). The fundamental 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 tons of 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 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’ll want to learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, reminiscent of 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 change charts? Not for novices, I do not assume, and never on mounts and tripods which can be 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.”

(*7*)Audio sky tour. Out beneath the night sky along 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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