This Week’s Sky at a Glance, September 10 – 18 – Sky & Telescope

The recurrent nova RS Ophiuchi had pale down previous magnitude 9.Zero as of September ninth. But Nova Cassiopeiae 2021 has jumped up but once more, to six.6 on that date, a magnitude brighter than its unique explosion final March. This is its seventh bump-up since March. It will not give up! It’s now classed as a “very slow nova.” Charts and comparability stars.


■ We proceed to have three vivid night planets this week: Venus low within the west-southwest at nightfall, Jupiter greater within the southeast to south throughout night, and dimmer Saturn practically two fists to Jupiter’s proper. By late night, faint Uranus and Neptune lurk excessive within the east.

■ The two brightest stars of September evenings are at all times Vega excessive overhead and Arcturus within the west, each magnitude zero. Draw a line from Vega all the way down to Arcturus. A 3rd of the way in which down you cross the dim Keystone of Hercules. Two thirds of the way in which you cross the fragile semicircle of Corona Borealis with its one modestly vivid star: Alphecca, the gem of the crown.


■ Look left of the thick crescent Moon for the pinnacle stars of Scorpius lined up not fairly vertically, and farther left for orange Antares. Halfway between the Moon and Antares (for the Americas) is the brightest of the pinnacle stars, the lengthy-time period eruptive variable Delta Scorpii. It’s been holding pretty regular round magnitude 1.Eight since 2010. Delta Sco is among the Gamma Cassiopeiae class of sizzling variable stars spinning at practically breakup pace. Read concerning the unique at Meet Gamma Cassiopeiae, the Classic Eruptive Variable.


■ Now the Moon shines higher proper of Antares. as proven under. They’re about 3° aside in early night for the Americas.

Sunday night the Moon shines over Antares. Monday night finds the Moon simply a few hours previous actual its first-quarter section (night within the Americas).


■ First-quarter Moon (actual at 4:39 p.m. EDT), shining within the toes of Ophiuchus. The Moon is about halfway between Antares to its decrease proper and the Sagittarius Teapot to its left (for North America). Look quickly after twilight ends, earlier than they sink decrease.


■ Now the Moon shines within the lid of the Sagittarius Teapot. The Teapot is tilting and pouring to the fitting, because it at all times does in September. Binoculars will aid you choose it out from the moonlight and light-weight air pollution. (Remember, the Teapot spans some 13°, about twice the width of a typical binocular’s discipline of view.)


■ Jupiter, Saturn, and the waxing gibbous Moon kind a gently curving line this night, with the Moon on the decrease proper. Extend a line from Saturn by way of the Moon and the identical quantity onward, and also you’re within the Sagittarius Teapot.


■ Now the Moon shines about 5° beneath Saturn, as indicated under. (Actually, the “Harvest Moon effect” extra usually refers back to the Moon persevering with to mild the early-night panorama for a number of days after full close to the September equinox. Before full the Moon lights the early night each month, although it is not essentially low.)

■ Polaris crosses a line. Roger Sinnott, Sky & Telescope’s longtime grasp of all issues celestial-mechanical, writes, “I found a neat curiosity when engaged on the Skygazer’s Almanac for 2021. Owing to precession, on September 16th Polaris reaches proper ascension 3h (equinox of date) for the primary time in 26,000 years, after having crossed 2h in 1964 and 1h in 1828.

“Of course, this doesn’t have any profound ramifications. But Polaris’s changing R.A. is very noticeable when you look it up in star charts or catalogues for equinox 2000.0 vs. 1950.0. It also shows up easily when you compare the 2021 Skygazer’s Almanac [our annual events-through-the-night chart that comes with every January’s issue of S&T ] with those from 10, 20, or 40 years ago. The nearer Polaris gets to the celestial pole, the more rapidly its R.A. changes.”


■ And now the gibbous Moon hangs decrease proper of the intense Jupiter at nightfall, as proven above.Later within the evening, because the sky turns, The Moon turns into immediately under Jupiter. That’s how you will discover them round midnight (daylight saving time).


■ You can see within the stars that the season is altering; We’ve reached the time of 12 months when, simply after dusk, chilly-climate Cassiopeia has already climbed a little greater within the northeast than the nice and cozy-climate Big Dipper has sunk within the northwest. Cas bedecks the excessive northern sky in early night in the course of the fall-winter half of the 12 months. The Big Dipper takes over for the milder evenings of spring and summer season.

Almost halfway between them stands Polaris. It’s at present a little above the midpoint between the 2.



This Week’s Planet Roundup

Mercury (about magnitude +0.2) could be very deep down within the sundown, 16° decrease proper of Venus this week. You may need a likelihood at it with binoculars or a broad-discipline scope. About 15 or 20 minutes after sundown, scan for it simply above your horizon due west. Good luck.Between Venus and Mercury is fainter Spica, magnitude +1.0.

Venus, good at magnitude –4.1, shines within the west-southwest throughout twilight. It nonetheless units round twilight’s finish.

Jupiter and Saturn shine within the southeast to south these evenings. They’re magnitudes –2.Eight and +0.4, respectively, on reverse sides of dim Capricornus.Jupiter begins the night as barely the decrease of the 2. Saturn glows 17° (nearly two fists) to Jupiter’s higher proper. They stage out round 9 or 10 p.m. daylight-saving time. By then they’re about at their highest within the south at their telescopic finest. After that they begin to tilt the opposite approach, with Saturn now decrease.Look for 1st-magnitude Fomalhaut about two fists (22°) to Jupiter’s decrease left. And this week, Jupiter is passing 1½° north of third-magnitude Delta Capricorni.

Uranus (magnitude 5.7, in southern Aries) will get excessive within the east after midnight.

Neptune (magnitude 7.8, at the Aquarius-Pisces border) is excessive within the southeast by 10 p.m.

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 upon longitude (primarily Moon positions) are for North America.

Eastern Daylight Time, EDT, is Universal Time minus Four hours. Universal Time is often known as UT, UTC, GMT, or Z time. To grow to be extra professional about time programs than 99% of the folks you will ever meet, see our compact article Time and the Amateur Astronomer.

Want to grow to be a higher astronomer? Learn your approach 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 a simple-to-use constellation information protecting the entire night sky, use the massive month-to-month map within the middle of every subject of Sky & Telescope, the important journal of astronomy.

Once you get a telescope, to place it to good use you will want a detailed, giant-scale sky atlas (set of charts). The primary commonplace is the Pocket Sky Atlas (in both the unique or Jumbo Edition), which exhibits 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 arduous covers and enlarged for simpler studying outside by purple flashlight. Sample charts. More concerning the present editions.

Next up is the bigger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; practically thrice as many. The subsequent up, as soon as you realize your approach 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 easy methods to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, akin to the massive Night Sky Observer’s Guide by Kepple and Sanner.

Can a computerized telescope exchange charts? Not for learners, I do not suppose, and never on mounts and tripods which might be lower than high-high 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 with yourearbuds in place, hearken to Kelly Beatty’s monthlypodcast 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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