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

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 shiny as its unique March eruption from its 15th-magnitude baseline. Charts and comparability stars.


■ Bright 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 Young Goat”). The scene is proven beneath for late twilight this night.

Farther to the higher proper of Saturn, search for Alpha and Beta Capricorni. Both 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 method 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, about a finger’s width at arm’s size. Jupiter is 175 occasions brighter! How early (or extra doubtless, late) in twilight are you able to first make out Delta Cap?Delta Cap is an fascinating star: a magnetic white subgiant, spectral class A7m, 9 occasions brighter than the Sun and carefully orbited by a small, dim orange dwarf nearly precisely as soon as a day. The dwarf passes in entrance of the intense star each orbit from our standpoint, dimming it by 0.24 magnitude. That’s theoretically discernable by eye — however with out close to-match comparability stars close by, good luck. The system is just 39 gentle-years away.

■ Jupiter’s Great Red Spot ought to cross Jupiter’s central meridian round 9:04 p.m. Eastern Daylight Time. For full timetables of the Red 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 massive Northern Cross. When you face southwest and crane your head method, method up, the cross seems to face upright. It’s about two fists at arm’s size tall, with Deneb as its high. Or to place it one other method, while you face that route the Swan seems to be diving straight down.

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


■ Bright 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 fitting of the highest of the kite, the Big Dipper is popping extra stage.

And that is the time of yr when, in the course of the night, the dim Little Dipper “dumps water” into the bowl of the Big Dipper method down beneath. The Big Dipper will dump it again within the evenings of spring.

■ Tonight Jupiter’s Great Red 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 shiny, is simply rising within the north-northeast (relying in your latitude; the farther north you’re the increased will probably be). They’re each magnitude 0.

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

When it does, flip round and look low within the south-southeast. There will probably be 1st-magnitude Fomalhaut at the about identical top too — precisely so when you’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, will probably be decrease.


■ Last-quarter Moon tonight (actual at 9:57 p.m. Eastern 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 jap horizon (for viewers at mid-northern latitudes).


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

Look at the second phase of the W counting down from the highest. Notice the dim bare-eye stars alongside that phase (not counting its two ends). The brightest of those, on the fitting, is Eta Cassiopeiae, magnitude 3.4. This is a remarkably Sun-like star simply 19 gentle-years away, and it has a orange-dwarf companion, magnitude 7.3, separation 13 arcseconds — a beautiful binary in a telescope.

Left of it, and fainter, is a bare-eye pair in a darkish sky: Upsilon1 and Upsilon2 Cassiopeiae, a good 0.3° aside. They’re yellow-orange giants unrelated to one another, 200 and 400 gentle-years distant from us. Upsilon2 is barely the brighter of the pair. It’s additionally the nearer one.

■ Night 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 massive asteroid 2 Pallas, nearly three weeks previous opposition, stands excessive within the southeast by 9 or 10 p.m. It’s nonetheless in small-telescope attain at magnitude 8.4. This week Pallas is 8° or 9° higher proper of Neptune, magnitude 8.7, which is also previous opposition. Read about each and hunt them down utilizing the finder charts in Asteroid Pallas Makes a Point in Pisces.


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

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

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

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


■ During night, look simply above the northeast horizon — far beneath excessive Cassiopeia — for shiny Capella on the rise. How quickly Capella rises, and the way excessive you will discover it, is determined by 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, about a third of the way in which 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.

■ Before and through early daybreak Sunday morning October third, the waning crescent Moon kinds 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 Sun.

Venus, sensible at magnitude –4.2, 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 +0.5, respectively, 16° aside on reverse sides of dim Capricornus.During twilight shiny Jupiter, on the left, is barely the decrease of the 2. They stage out quickly after darkish, and later they tilt the opposite method, with Saturn now the decrease one. Saturn units round 2 a.m. daylight-saving time, adopted down by Jupiter about an hour later.In the night search for 1st-magnitude Fomalhaut 23° (two fists) decrease left of Jupiter. And lower than 2° beneath or decrease left of Jupiter is third-magnitude Delta Capricorni, described within the caption above.Also, see Amateurs Spot New Impact 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 7.8, at 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 depend 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 skilled about time methods 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 method across the constellations. They’re the important thing to finding every little thing fainter and deeper to hunt with binoculars or a telescope.

This is an out of doors nature passion. For a straightforward-to-use constellation information overlaying the entire night sky, use the massive month-to-month map within the middle 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, giant-scale sky atlas (set of charts). The primary normal is the Pocket Sky Atlas (in both the unique or Jumbo Edition), which reveals stars to magnitude 7.6.

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and a whole bunch 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 purple flashlight. Sample charts. More in regards to 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 understand your method 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 a Star Chart at the Telescope.

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

Can a computerized telescope exchange charts? Not for freshmen, I do not assume, and never on mounts and tripods which can be lower than high-high 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.”

Audio sky tour. Out underneath 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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