Home / Space force / This Week's Sky at a Glance, September 18 – 26 – Sky & Telescope

This Week's Sky at a Glance, September 18 – 26 – Sky & Telescope

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■ Jupiter and Saturn this week proceed shining almost stage within the south at nightfall, as proven under. They tilt to the appropriate as night advances. They set within the southwest round midnight or 1 a.m.

Saturn and Jupiter shining in the south at disk, mid-late September 2020

■ The season is altering; you’ll be able to see it within the stars. We have reached the time of yr when, simply after dusk, Cassiopeia has already climbed somewhat greater within the northeast than the Large Dipper has sunk within the northwest. Cassiopeia, a flattened W form, marks the excessive northern sky in early night throughout the chilly fall-winter half of the yr. The Large Dipper takes over for the milder evenings of spring and summer season.

Nearly midway between them stands Polaris, due north. It is presently somewhat above the midpoint between the 2.


■ Arcturus, the “Spring Star,” shines somewhat decrease within the west after darkish each week as summer season turns to fall (the September equinox comes on Tuesday). From Arcturus, the slim, kite-shaped sample of Bootes extends somewhat extra that two fists at arm’s size to the higher proper.

■ Moonless evenings will quickly finish for this month, however there’s nonetheless time to catch the Milky Means beneath a darkish sky. When Deneb crosses your zenith (two hours after Vega; round 9 or 10 p.m. now), the Milky Means does too — working straight up from the southwest horizon, and straight all the way down to the northeast horizon.


■ How nicely do you actually know the long-lasting Ring Nebula in Lyra? Within the night after moonset it is excessive overhead, in most likely the darkest a part of your sky. Discover its subtleties with Howard Banich’s Going Deep column within the September Sky & Telescope, beginning on web page 58.

And discover the realm of the outstretched hand of Andromeda, together with the Blue Snowball nebula, a delicate galaxy, and a number of other good double stars, beginning on web page 62.


■ Mercury and fainter Spica seem solely 2/three° aside this night, and three/four° aside tomorrow night, for North America. They’re magnitudes zero and +1, respectively, however they could be a problem to identify even with binoculars since they’re already very low above the west-southwest horizon in brilliant twilight simply 15 or 20 minutes after sundown. And throughout a lot of North America, your low view could also be additional hindered by forest-fire smoke excessive within the environment.

Mercury and Spica seem shut sufficient collectively to suit simply into the view of a telescope at 50x or much less. . . as soon as you discover them.

Moon occults double star this night. The darkish fringe of the waxing crescent Moon eclipses the positive telescopic double star Beta Scorpii, magnitudes 2.6 and four.5, for many of North America besides the Northeast. Use a telescope to look at the pair disappear stepwise behind the Moon’s earthlit edge, one after the opposite some seconds aside.

Within the East the Moon might be very low. The mid-longitudes of the continent get the most effective view, in early-evening darkness with the Moon much less low. Close to the West Coast the star’s disappearance occurs in daylight, and its reappearance out from behind the Moon’s brilliant limb happens in twilight. Map and timetables for a lot of cities.


■ Summer time ends and fall begins (within the Northern Hemisphere) at this time at 9:31 a.m. EDT (13:31 UT). That is when the Solar crosses the equator heading south for the season. The Solar rises nearly due east and units nearly due west, very near 12 hours aside.

■ Coincidentally, round when summer season turns to autumn yearly, Deneb takes over from brighter Vega because the zenith star after dusk (for skywatchers at mid-northern latitudes).

■ Round dusk, search for Antares to the decrease proper of the crescent Moon. They’re getting low within the southwest.

■ Jupiter’s Nice Pink Spot ought to transit Jupiter’s central meridian round 9:23 p.m. Japanese Daylight Time. Simply four minutes later Jupiter’s moon Io enters the jap fringe of the planet’s disk, adopted by Io’s tiny black shadow at 10:42 p.m. EDT. Io and its shadow go away the opposite facet of Jupiter’s face at 11:43 p.m. and 12:58 a.m. EDT, respectively.


■ First-quarter Moon (actual at 9:55 p.m. EDT). The Moon shines within the south at nightfall. To its left are Jupiter and Saturn, pointing at it.


■ Now the Moon, a day previous first quarter, shines just some levels from Jupiter. Saturn seems on from their left, as proven under.

Moon with Jupiter and Saturn, Sept. 24-25, 2020


■ Now it is Saturn’s flip to pair with the Moon, whereas Jupiter shines to their proper, as proven above.


■ The waxing gibbous Moon shines within the south in mid-evening, contained in the dim boat-shaped sample of Capricornus. Off to its proper are Saturn after which Jupiter.

Look somewhat farther to the Moon’s decrease left for Fomalhaut, the Autumn Star, slowly gaining altitude.


This Week’s Planet Roundup

Mercury is having a really low, poor apparition deep within the sundown. Not less than it is pretty brilliant at magnitude –zero.1 this week, so go forward and check out. Carry binoculars not less than. About 15 minutes after sundown whereas twilight remains to be brilliant, begin scanning for it simply above the west-southwest horizon. Good luck.

Additionally within the neighborhood is Spica, a magnitude fainter and twinklier. Spica and Mercury are ¾° or much less from one another on September 21st and 22nd, once they’ll simply match collectively in a telescope’s 40-power view.

Venus (magnitude –four.2, crossing from Most cancers into Leo) rises in deep darkness two hours earlier than daybreak begins, within the east-northeast far under Pollux and Castor. By the point daybreak will get beneath approach, Venus shines prominently within the east, as proven under. Every morning it is drawing nearer to a lot fainter Regulus.

Procyon shines about 30° (about three first at arm’s size) to Venus’s higher proper. To the appropriate or decrease proper of Procyon shines effulgent Sirius — the brightest star, however nowhere close to a match for Venus.

In a telescope, Venus continues to shrink slowly into the gap; it is now 17 arcseconds in diameter. And it is changing into extra gibbous, 67% sunlit now, because it rounds towards passing behind the Solar subsequent winter.

Regulus is climbing up out of the daybreak on its approach to passing about ½° from Venus on October 2nd and third.

Mars shines ever greater, brighter and nearer because it approaches its October 13th opposition! It can go closest by Earth on October sixth. And it is rising earlier too. This week it rises within the east in late twilight, shining brilliant orange at magnitude –2.three, nearly Jupiter-bright. Mars climbs greater by means of the night and stands at its highest and telescopic greatest round 2 or three a.m. daylight-saving time, beaming down from excessive within the south. It is close to the dim (4th-magnitude) Knot of Pisces.

Mars is already 21 or 22 arcseconds in obvious diameter, as large for all sensible functions as will probably be when passing closest by Earth (22.6 arcseconds). Search for its white South Polar Cap, now drastically shrunken as summer season advances in Mars’s southern hemisphere. There might or will not be any patches of cloud; this appears to be a transparent season on Mars.

However Mars’s dusky floor markings are the everlasting attraction. To get a map of the facet dealing with Earth on the date and time you may observe, you should use our Mars Profiler. The map there’s sq.; keep in mind to mentally wrap it onto the facet of a globe. (Options close to the map’s edges turn out to be very foreshortened.)

Mars on August 27th, imaged at very excessive decision by Enrico Enzmann and Damian Peach with a 76cm (30-inch) telescope. South is up. Darkish Syrtis Main juts down from heart. Higher left of it’s darkish Mare Tyrrhenum. Above them is the big, round Hellas Basin, lighter in coloration however not as brilliant as when it is crammed with cloud or frost. Sinus Meridiani is on the heart of the right-hand (morning) limb.
One other facet of Mars, imaged by Peach on September 11 with a 250-cm (10-inch) Mewlon Dall-Kirkham telescope. Darkish Mare Sirenum and Mare Cimmerium prolong to the appropriate and much proper, respectively. The South Polar Cap seems even smaller than earlier than. A few of the grey South Polar Cloud Hood extends round from the underside limb. Left of heart, the pair of small, weak whitish marks are orographic cloud at Arsia Mons, says Peach.

Jupiter and Saturn (magnitudes –2.four and +zero.four, respectively) shine within the south throughout nightfall and early night, as proven on the high of this web page, then transfer to the southwest as night grows late. Jupiter is the brightest. Saturn stays eight° to its left.

Very excessive above them shines Altair, magnitude +zero.eight. It is white-hot, 11 instances as luminous because the Solar, and simply 17 light-years away.

A lot nearer under Jupiter after darkish is the deal with of the Sagittarius Teapot. The brightest star of the deal with (the upper-right one) is Sigma Sagittarii or Nunki, magnitude 2.zero. It is a fair bigger, hotter blue-white star: four.5 instances the diameter of the Solar, 3300 instances as luminous, and 230 light-years away.

Telescopically, there’s lots occurring on Jupiter now; see Bob King’s Stormy Times on Jupiter. And comply with the interaction of Jupiter with its moons and their shadows, and discover the transit instances of Jupiter’s Nice Pink Spot, within the Celestial Calendar part of the September Sky & Telescope, web page 50.

Jupiter on August 23rd, imaged by Christopher Go at 11:28 UT. South right here is up. Darkish “eyeliner” outlines the north facet of the Pink Spot Hole. Simply above the Pink Spot is massive, pale Oval BA adopted on its decrease proper by a line of blackish turbulence. Broad, bluish festoon bases line the south fringe of the reddish, chaotic North Equatorial Belt. And under, discover the “white whale” of the brand new upwelling outbreak within the slim North Tropical Zone.

Expert, well-equipped amateurs like Go can seize extraordinary planetary element by considered use of video-image stacking and processing. For comparability, here’s a Hubble image of Jupiter taken two days later (with a NASA press launch about it). Full-res version, with distinction and coloration distinction boosted approach up. Go makes use of a 14-inch scope on his condominium balcony in Cebu Metropolis, Philippines. The Hubble is a fantastically refined 92-inch telescope above the environment!

Practically the identical face of Jupiter imaged by Go 21 days later, on September 13th. Loads has modified. Oval BA and its turbulent wake have moved left (towards previous) with respect to the Pink Spot, and the Pink Spot’s “eyeliner” has damaged up. In the meantime far under, the North Tropical Zone outbreak has raced far to the left with respect to the Pink Spot and is trailing a really lengthy plume of combined brilliant and darkish materials. “Jupiter could be very busy as of late,” writes Go. What number of different adjustments can you discover?

Uranus (magnitude 5.7, in Aries) is pretty nicely up within the east by 10 or 11 p.m. daylight-saving time, about 12° east of Mars.

Neptune (magnitude 7.eight, in Aquarius) is greater within the south-southeast at the moment. It was at opposition on September 11th. Finder charts for Uranus and Neptune.

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.

Japanese Daylight Time, EDT, is Common Time (also referred to as UT, UTC, GMT, or Z time) minus four hours.

Need to turn out to be a greater astronomer? Be taught your approach 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 pastime. For an easy-to-use constellation information masking the entire night sky, use the massive month-to-month map within the heart of every challenge 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 customary 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 tons of of telescopic galaxies, star clusters, and nebulae amongst them. Proven right here is the Jumbo Version, in exhausting covers and enlarged for simpler studying outdoor at night time. Sample chart. More about the recent new editions.

Subsequent up is the bigger and deeper Sky Atlas 2000.0, plotting stars to magnitude eight.5; almost 3 times as many. The subsequent up, as soon as your approach round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And skim how to use sky charts with a telescope.

You may additionally desire a good deep-sky guidebook, equivalent to Sky Atlas 2000.0 Companion by Sturdy and Sinnott, or the larger (and illustrated) Night Sky Observer’s Guide 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, 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 can not come with out growing the talents to seek out issues within the sky and understanding how the sky works. This information comes solely by spending time beneath the celebs with star maps in hand.”

Audio sky tour. Out beneath 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 hazards of not pondering clearly are a lot better now than ever earlier than. It isn’t that there is one thing new in our mind-set, it is that credulous and confused pondering may be way 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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