#astronomy This Week’s Sky at a Look, Sept. 24 – Oct. 2 – Sky & Telescope

September 25, 2021 - Comment

Nova Cassiopeiae 2021 carries on, fluctuating unpredictably because it stays in binocular view six months after its March explosion. As of September 21st it was again as much as magnitude 6.7, greater than twice as brilliant as its unique March eruption from its 15th-magnitude baseline. Charts and comparability stars. FRIDAY, SEPTEMBER 24 ■ Vivid Jupiter

Nova Cassiopeiae 2021 carries on, fluctuating unpredictably because it stays in binocular view six months after its March explosion. As of September 21st it was again as much as magnitude 6.7, greater than twice as brilliant as its unique March eruption from its 15th-magnitude baseline. Charts and comparability stars.


■ Vivid Jupiter and fainter Saturn proceed to dominate the southern night sky, 16° aside. All week Jupiter shines simply above or higher proper of Third-magnitude Delta Capricorni, Deneb Algedi (the identify means “Tail of the Younger Goat”). The scene is proven beneath for late twilight this night.

Farther to the higher proper of Saturn, search for Alpha and Beta Capricorni. Each are binocular double stars. Alpha is a large pair of yellow-orange giants that the smallest binoculars simply resolve; so does our chart beneath. The elements of Beta are half as far aside, rather more unequal, and oriented roughly the identical approach because the Alpha pair.

As the celebs come out this week, search for Third-magnitude Delta Capricorni slightly below or decrease left of Jupiter. Tonight they’re 1.5° aside, a few finger’s width at arm’s size. Jupiter is 175 occasions brighter! How early (or extra possible, late) in twilight are you able to first make out Delta Cap?

Delta Cap is an attention-grabbing star: a magnetic white subgiant, spectral class A7m, 9 occasions brighter than the Solar and intently orbited by a small, dim orange dwarf nearly precisely as soon as a day. The dwarf passes in entrance of the brilliant star each orbit from our standpoint, dimming it by zero.24 magnitude. That is theoretically discernable by eye — however with out near-match comparability stars close by, good luck. The system is barely 39 light-years away.

■ Jupiter’s Nice Crimson Spot ought to cross Jupiter’s central meridian round 9:04 p.m. Jap Daylight Time. For full timetables of the Crimson Spot’s transits in addition to the doings of Jupiter’s moons and their shadows, see the Celestial Calendar part of Sky & Telescope journal.


■ Cygnus the Swan floats nearly straight overhead these evenings. Its brightest stars kind the large Northern Cross. While you face southwest and crane your head approach, approach up, the cross seems to face upright. It is about two fists at arm’s size tall, with Deneb as its prime. Or to place it one other approach, whenever you face that course the Swan seems to be diving straight down.

The waning gibbous Moon would not rise now till about an hour after darkish. So take this chance to search for the Milky Approach operating straight up from the west-southwest horizon, alongside the spine of Aquila and simply to the appropriate of brilliant Altair excessive within the south; then alongside the shaft of the Northern Cross overhead, and straight down by Cassiopeia and northern Perseus to the east-northeast horizon.


■ Vivid Arcturus, pale yellow-orange, shines ever decrease within the west-northwest at dusk. The slim kite form of its constellation, Bootes, extends two fists at arm’s size to Arcturus’s higher proper. Arcturus is the place the kite’s downward-hanging tail is tied on.

To the appropriate of the highest of the kite, the Massive Dipper is popping extra degree.

And that is the time of 12 months when, through the night, the dim Little Dipper “dumps water” into the bowl of the Massive Dipper approach down beneath. The Massive Dipper will dump it again within the evenings of spring.

■ Tonight Jupiter’s Nice Crimson Spot ought to cross the planet’s central meridian round 10:42 p.m. EDT (7:42 p.m. Pacific). It stays in good view for about an hour earlier than and after that point.


■ Arcturus shines within the west in late twilight these evenings. Capella, equally brilliant, is simply rising within the north-northeast (relying in your latitude; the farther north you’re the increased it is going to be). They’re each magnitude zero.

Later within the night, Arcturus and Capella shine at equal heights of their respective compass instructions. When will this occur? That is dependent upon each your latitude and longitude.

When it does, flip round and look low within the south-southeast. There will likely be 1st-magnitude Fomalhaut on the about similar peak too — precisely so if you happen to’re at latitude 43° north (in regards to the latitude of Boston, Buffalo, Milwaukee, Boise, Eugene). Seen from south of that latitude, Fomalhaut will seem increased than Capella and Arcturus are. Seen from north of there, it is going to be decrease.


■ Final-quarter Moon tonight (actual at 9:57 p.m. Jap Daylight Time). The Moon rises round 11 or midnight in Gemini, down beneath Capella and the remainder of Auriga.

An hour later look off to the Moon’s proper, and there is Orion stepping up over the japanese horizon (for viewers at mid-northern latitudes).


■ The starry W of Cassiopeia stands excessive within the northeast after darkish. The precise-hand facet of the W (the brightest facet) is tilted up.

Take a look at the second phase of the W counting down from the highest. Discover the dim naked-eye stars alongside that phase (not counting its two ends). The brightest of those, on the appropriate, is Eta Cassiopeiae, magnitude three.four. It is a remarkably Solar-like star simply 19 light-years away, and it has a orange-dwarf companion, magnitude 7.three, separation 13 arcseconds — a beautiful binary in a telescope.

Left of it, and fainter, is a naked-eye pair in a darkish sky: Upsilon1 and Upsilon2 Cassiopeiae, a very good zero.three° aside. They’re yellow-orange giants unrelated to one another, 200 and 400 light-years distant from us. Upsilon2 is barely the brighter of the pair. It is also the nearer one.

■ Evening owl? Look east any time from 1 or 2 a.m. to early daybreak Thursday morning, and you will find the waning Moon close to Pollux in Gemini. Above Pollux is Castor.


■ The large asteroid 2 Pallas, nearly three weeks previous opposition, stands excessive within the southeast by 9 or 10 p.m. It is nonetheless in small-telescope attain at magnitude eight.four. This week Pallas is eight° or 9° higher proper of Neptune, magnitude eight.7, which is also previous opposition. Examine each and hunt them down utilizing the finder charts in Asteroid Pallas Makes a Level in Pisces.


■ Vega is the brightest star simply west of the zenith after darkish. Face west and look to Vega’s proper by 14° (almost a fist and a half at arm’s size) for Eltanin, the nostril of Draco the Dragon. The remainder of Draco’s fainter, lozenge-shaped head is a bit farther behind. Draco at all times eyes Vega as they wheel across the sky.

The principle stars of Vega’s personal constellation, Lyra — faint by comparability — prolong to its left (by 7°).

■ Earlier than and through early daybreak Saturday morning October 2nd, look beneath the crescent Moon by a few fist at arm’s size for Regulus, forefoot of Leo already making his early-apparition look, as proven beneath.

Leo publicizes spring when it is on the rise within the early night sky. However Leo’s arrival within the east at the start of daybreak? That says October.


■ Throughout night, look simply above the northeast horizon — far beneath excessive Cassiopeia — for brilliant Capella on the rise. How quickly Capella rises, and the way excessive you may discover it, is dependent upon your latitude. The farther north you might be, the earlier and better.

■ Vega is the brightest star very excessive within the west, and Arcturus is getting low within the west-northwest. The brightest star within the huge expanse between them, a few third of the best way from Arcturus up towards Vega, is Alphecca, magnitude 2.2 — the crown jewel of dim Corona Borealis. Alphecca is a 17-day eclipsing binary, however (like most variable stars!) its brightness dips are too slight for the attention to see reliably.

■ Earlier than and through early daybreak Sunday morning October Third, the waning crescent Moon types a flat, nearly isosceles triangle with Regulus and Algieba (Gamma Leonis) to Regulus’s left or higher left, as proven above (for North America).



This Week’s Planet Roundup

Mercury is hidden deep within the glare of the Solar.

Venus, sensible at magnitude –four.2, shines low within the southwest throughout twilight. And it nonetheless units round twilight’s finish.

Jupiter and Saturn proceed to shine within the southeast to south throughout night. They’re magnitudes –2.7 and +zero.5, respectively, 16° aside on reverse sides of dim Capricornus.

Throughout twilight brilliant Jupiter, on the left, is barely the decrease of the 2. They degree out quickly after darkish, and later they tilt the opposite approach, with Saturn now the decrease one. Saturn units round 2 a.m. daylight-saving time, adopted down by Jupiter about an hour later.

Within the night search for 1st-magnitude Fomalhaut 23° (two fists) decrease left of Jupiter. And fewer than 2° beneath or decrease left of Jupiter is Third-magnitude Delta Capricorni, described within the caption above.

Additionally, see Amateurs Spot New Impression Flash at Jupiter. With movies of it taken by two newbie Jupiter-impact screens.

Uranus (magnitude 5.7, in southern Aries) climbs excessive within the east by midnight.

Neptune (magnitude 7.eight, on the Aquarius-Pisces border) is excessive within the southeast by 9 or 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 on longitude (primarily Moon positions) are for North America.

Jap Daylight Time, EDT, is Common Time minus four hours. Common Time is often known 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 Newbie Astronomer.

Wish to develop into a greater astronomer? Study your approach across the constellations. They’re the important thing to finding every little thing fainter and deeper to hunt with binoculars or a telescope.

That is an out of doors nature passion. For an easy-to-use constellation information overlaying 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.

When you get a telescope, to place it to good use you may want an in depth, large-scale sky atlas (set of charts). The essential commonplace 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 tons of 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 open air by crimson 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; almost 3 times as many. The following up, as soon as your approach round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.zero (stars to magnitude 9.75). And make sure you learn The best way to Use a Star Chart on the Telescope.

You may additionally need a good deep-sky guidebook, equivalent to the large Evening Sky Observer’s Information by Kepple and Sanner.

Can a computerized telescope change charts? Not for novices, I do not suppose, and never on mounts and tripods which might be 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’t come with out creating the talents to seek out issues within the sky and understanding how the sky works. This data comes solely by spending time underneath the celebs with star maps in hand.”

Audio sky tour. Out underneath 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 is free.

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

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


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