#astronomy This Week’s Sky at a Look, September 10 – 18 – Sky & Telescope

September 11, 2021 - Comment

The recurrent nova RS Ophiuchi has light down previous magnitude 9.zero as of September 10th. However Nova Cassiopeiae 2021 has jumped up but once more, to six.6 on that date, a magnitude brighter than its authentic explosion final March. That is its seventh bump-up since March. It will not stop! It is now classed as

The recurrent nova RS Ophiuchi has light down previous magnitude 9.zero as of September 10th. However Nova Cassiopeiae 2021 has jumped up but once more, to six.6 on that date, a magnitude brighter than its authentic explosion final March. That is its seventh bump-up since March. It will not stop! It is now classed as a “very sluggish nova.” Charts and comparability stars.


■ We proceed to have three vibrant 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 2 brightest stars of September evenings are all the time 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 best way down you cross the dim Keystone of Hercules. Two thirds of the best way you cross the fragile semicircle of Corona Borealis with its one modestly vibrant 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. Midway between the Moon and Antares (for the Americas) is the brightest of the pinnacle stars, the long-term eruptive variable Delta Scorpii. It has been holding pretty regular round magnitude 1.eight since 2010.

Delta Sco is likely one of the Gamma Cassiopeiae class of scorching variable stars spinning at practically breakup pace. Learn in regards to the authentic at Meet Gamma Cassiopeiae, the Basic Eruptive Variable.


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

Moon over Antares and Scorpius, Sept. 12-13, 2021Sunday night the Moon shines over Antares. Monday night within the Americas finds the Moon just some hours previous its precise first-quarter part.


■ First-quarter Moon (precise at four: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 suitable, like all the time in September. Binoculars will show you how to decide it out from moonlight and lightweight air pollution. (Do not forget that the Teapot spans some 13°, about twice the width of a typical binocular’s area of view.)


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


■ Now the Moon shines about 5° below Saturn, as indicated beneath. (Truly, the “Harvest Moon impact” extra typically refers back to the Moon persevering with to gentle the early-evening panorama for a number of days after full close to the September equinox. Earlier than full the Moon lights the early night each month, although it isn’t essentially low.)

Waxing gibbous Moon passing under Saturn and Jupiter, Sept. 16-17, 2021.

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.

“In fact, this does not have any profound ramifications. However Polaris’s altering R.A. could be very noticeable if you look it up in star charts or catalogues for equinox 2000.zero vs. 1950.zero. It additionally exhibits up simply if you examine the 2021 Skygazer’s Almanac [our annual events-through-the-night chart, which comes with every January’s S&T ] with these from 10, 20, or 40 years in the past. The nearer Polaris will get to the celestial pole, the extra quickly its R.A. modifications.”


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


■ You possibly can see within the stars that the season is altering: We have reached the time of 12 months when, simply after dusk, cold-weather Cassiopeia has already climbed a bit of greater within the northeast than the warm-weather Huge 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 Huge Dipper takes over for the milder evenings of spring and summer season.

Virtually halfway between them stands Polaris. It is at the moment a bit of above the midpoint between the 2.



This Week’s Planet Roundup

Mercury (about magnitude +zero.2) could be very deep down within the sundown, 16° decrease proper of Venus this week. You may need an opportunity 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.

Between Venus and Mercury is fainter Spica, magnitude +1.zero.

Venus, sensible at magnitude –four.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 +zero.four, respectively, on reverse sides of dim Capricornus.

Jupiter begins the night as barely the decrease of the 2. Saturn glows 17° (virtually 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 greatest. After that they begin to tilt the opposite means, with Saturn now the decrease one.

Search 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.eight, on 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 depend upon longitude (primarily Moon positions) are for North America.

Jap Daylight Time, EDT, is Common Time minus four hours. Common Time is also called UT, UTC, GMT, or Z time. To grow to be extra skilled about time programs than 99% of the folks you will ever meet, see our compact article Time and the Beginner Astronomer.

Need to grow to be a greater astronomer? Study your means across the constellations. They’re the important thing to finding all the things fainter and deeper to hunt with binoculars or a telescope.

That is an out of doors nature interest. For an easy-to-use constellation information protecting the entire night sky, use the large month-to-month map within the middle of every difficulty of Sky & Telescope, the important journal of astronomy.

When you get a telescope, to place it to good use you will want an in depth, large-scale sky atlas (set of charts). The essential customary is the Pocket Sky Atlas (in both the unique or Jumbo Version), which exhibits stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo editionThe Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and a whole lot of telescopic galaxies, star clusters, and nebulae amongst them. Proven right here is the Jumbo Version, which is in arduous covers and enlarged for simpler studying outside by pink flashlight. Pattern charts. Extra in regards to the present editions.

Subsequent up is the bigger and deeper Sky Atlas 2000.zero, plotting stars to magnitude eight.5; practically 3 times as many. The subsequent up, as soon as you recognize your means round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.zero (stars to magnitude 9.75). And be sure you learn easy methods to use sky charts with a telescope.

You will additionally desire a good deep-sky guidebook, akin to the large Evening Sky Observer’s Information by Kepple and Sanner.

Can a computerized telescope exchange charts? Not for learners, 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 Yard Astronomer’s Information, “A full appreciation of the universe can not come with out growing the talents to search out issues within the sky and understanding how the sky works. This data comes solely by spending time below the celebrities 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 is free.

“The risks of not considering clearly are a lot higher now than ever earlier than. It isn’t that there is one thing new in our mind-set, it is that credulous and confused considering might be far more deadly in methods it was by no means earlier than.”
            — Carl Sagan, 1996

“Info are cussed issues.”
            — John Adams, 1770


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