This Week’s Sky at a Glance, October 8 – 16

Long-lasting, ever fluctuating Nova Cassiopeiae 2021 was about magnitude 7.4 as of October eighth. That’s barely brighter than when it exploded final March. Charts and comparison stars.


■ Bright Jupiter and fainter Saturn proceed to dominate the southern night sky this week. They’re 15° aside.

■ This night, spot Venus low within the southwest as early in twilight as you possibly can. Then look decrease proper of it by some 12° (about a fist at arm’s size) for the skinny crescent Moon, 2½ days outdated. Binoculars assist.

If you catch the best time window between the sky nonetheless being too vibrant and the Moon sinking too low, you must get a advantageous view of earthshine dimly lighting the Moon’s nightlands contained in the crescent. And the Moon is at perigee immediately, so it would seem simply a little bit bigger than common: a supercrescent moon.

You haven’t got photometric-quality eyes, however for those who did, you may discover that earthshine on the Moon has gotten just a trace dimmer on common in current years. This is because of a gradual change in Earth’s common reflectivity (albedo) over some 20 years on account of altering cloudiness tendencies. The earthshine fade that P. R. Goode and colleagues measured throughout twenty years from Big Bear Solar Observatory is tiny; it quantities to Earth absorbing a further 0.5 watt per sq. meter of incoming daylight on common. But they are saying this variation matches measurements made by different strategies and is “climatologically significant.”

■ The very weak Draconid meteor bathe must be at its peak round this date. But even below very best dark-sky circumstances it normally produces not more than 10 meteors seen per hour. . . and virtually no person’s circumstances are very best.

But not like most meteor showers, which carry out greatest within the early-morning hours, the very best time to look at for Draconids is within the night, the earlier after darkish the higher. Why? The bathe’s radiant (within the head of Draco) begins the night excessive within the northwest and wheels decrease because the hours go by.

The meteors are bits of particles from Comet Giacobini-Zinner, so the bathe is usually referred to as the Giacobinids. In the previous it has stormed spectacularly for a few hours or much less, notably in 1933 and 1946 and to a lesser extent a number of occasions since, however do not anticipate that this year; the comet is just not close to us in its orbit.

■ Jupiter’s Great Red Spot ought to cross Jupiter’s central meridian round 10:41 p.m. EDT (7:41 p.m. PDT). The Red Spot stays nearer to the central meridian than to the planet’s edge for 50 minutes earlier than and after it transits. A lightweight blue or green filter at the eyepiece helps a bit.


■ Now the Moon shines solely about 3° above Venus in twilight (for North America), simply whereas Venus is passing ¾° decrease left of 2nd-magnitude Delta Scorpii, as proven beneath. Bring binoculars!

Crescent Moon with Venus in the head of Scorpius, Oct. 9, 2021
Set your calendar for nightfall on the ninth to catch the Moon at the side of Venus, whereas Venus is in nearer conjunction with Delta Scorpii. Bring your binoculars.


■ Did you already know that October is aurora season? Your likelihood of catching a show of the Northern Lights is bigger now than common across the year, for causes having to do with the lean of Earth’s magnetic axis with respect to the incoming solar wind and the form of Earth’s magnetosphere. This month the magnetosphere’s northern “throat”is effectively aimed to swallow charged particles from the Sun and steer them down towards the world’s north polar area. Sometimes a gust of particles widens the throat to incorporate lands farther south. The mid-hours of the night time are the likeliest time, and naturally you need the Moon to have set by then. Keep a watch to the low north. See the October Sky & Telescope, web page 48.


■ Vega is the brightest star very excessive west of the zenith after darkish. Less excessive within the south-southwest is Altair, not fairly as vibrant. Just higher proper of Altair, by a finger-width at arm’s size, is little orange Tarazed. Down from Tarazed runs the dimmer stick-figure spine of Aquila, the Eagle.


■ First-quarter Moon (actual at 11:25 p.m. EDT). The Moon shines simply east (left) of the deal with of the Sagittarius Teapot. Far to the Moon’s higher left are Saturn after which Jupiter.

■ The Great Square of Pegasus balances on its nook excessive within the east throughout early night. Away from the Great Square’s left nook runs the primary line of Andromeda, three 2nd-magnitude stars about as vibrant as these of the Square and spaced equally far aside. (The three embrace the Square’s nook.) This complete dipper-shaped sample was named the Andromegasus Dipper by the late Sky & Telescope columnist George Lovi becoming a member of the Big and Little Dippers, the Milk Dipper of Sagittarius (these days normally subsumed into the Teapot), and the tiny dipper sample of the Pleiades.


■ With the season turning chill, Deneb has changed Vega because the zenith star of early darkness (for skywatchers at mid-northern latitudes). Accordingly, Capricornus has changed Sagittarius because the zodiacal constellation low within the south. This year, after all, Capricornus is overwhelmed by its two vibrant visitors: Jupiter and Saturn.

■ Jupiter’s Great Red Spot ought to transit the planet’s central meridian round 9:49 p.m. EDT.


■ The Moon shines below Jupiter and Saturn, practically equidistant from them as seen from the Americas in early night; see the scene beneath. It’s as if the Moon is swinging in a hammock that is tied to Jupiter and Saturn at its ends. Much fainter within the background is the hammock form of Capricornus, bigger than the brilliant one and askew to it.

Moon under Jupiter and Saturn, Oct. 14-15, 2021
The gibbous Moon passes below Jupiter and Saturn because it waxes towards full. Down beneath, how early in twilight are you able to choose up autumnal Fomalhaut twinkling into view?


■ Spot Venus low within the west in twilight. Just decrease left of it, by 1½° (about a finger width at arm’s size), search for orange Antares. It’s lower than 1% as vibrant. Venus stays about this near Antares for the following two days, however watch their orientation change.


■ This is the time of year when, quickly after dusk, W-shaped Cassiopeia stands on finish midway up the northeastern sky — and when, off to its left within the north, the dim Little Dipper extends immediately leftward from Polaris.


This Week’s Planet Roundup

Mercury emerges into daybreak view at the tip of this week. By about October 18th, search for it low above the east horizon about 50 minutes earlier than dawn. Don’t confuse Mercury with Arcturus, which is barely above the northeast horizon (relying in your latitude) way off to Mercury’s left.

Mercury is on its way up towards its greatest morning apparition of the year. Stay tuned.

Mars stays out of sight, barely previous its October 7-8 conjunction with the Sun.

Venus, good at magnitude –4.3, shines low in southwest throughout twilight, in higher Scorpius. It units quickly after twilight’s finish. Venus will cross 1.4° north of Antares on Saturday the sixteenth.

Jupiter and Saturn proceed to shine within the south throughout night, 15° aside on reverse sides of Capricornus. Jupiter is the eye-grabber at magnitude –2.7. Saturn, to its proper, is a twentieth as vibrant at magazine +0.5.

In late twilight they shine equally excessive within the south-southeast. As night progresses watch them tilt as they transfer to the correct, with Saturn changing into the decrease one. Saturn units round 1 a.m. daylight-saving time, adopted by Jupiter about an hour later.

After darkish look 23° (two fists at arm’s size) decrease left of Jupiter for 1st-magnitude Fomalhaut.

Here’s a beginner’s telescopic guide to Jupiter.

Jupiter on October sixth, imaged by S&T‘s Sean Walker with a 12-inch reflector in New Hampshire. North is up. “Last night we were treated to some excellent seeing conditions.” he writes. “I spent hours shooting and observing the planet, watching the GRS transit, as well as the dark barges in the NEB, and the series of white ovals south of the SEB. It was a magical night of observing — I was seeing the first diffraction ring around Io and Europa; don’t think I can ever recall seeing that before. Wish I could have shared it with others.”

Uranus (magnitude 5.7, in southern Aries) climbs excessive within the east by 11.

Neptune (magnitude 7.8, at the Aquarius-Pisces border) is already effectively up within the within the southeast by twilight’s finish.

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 4 hours. Universal Time is often known as UT, UTC, GMT, or Z time. To grow to be extra professional about time techniques 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 all the pieces fainter and deeper to hunt with binoculars or a telescope.

This is an outside nature passion. For an easy-to-use constellation information masking 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 normal 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 a whole lot 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 open air 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; practically 3 times as many. The subsequent up, as soon as you already know your way 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 How to Use a Star Chart with a Telescope.

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

Can a computerized telescope exchange charts? Not for newbies, I do not assume, and never on mounts and tripods which can be lower than top-quality mechanically, which means heavy and costly. And as Terence Dickinson and Alan Dyer say of their Backyard Astronomer’s Guide, (*16*)

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’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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