- On August twenty ninth, the waxing crescent Moon is positioned in Libra, approaching Scorpius; observations of the globular cluster M71 in Sagitta are beneficial, noting its comparatively free construction in comparison with denser clusters.
- August thirtieth marks Iapetus’ biggest western elongation from Saturn, providing a possibility to look at its various brightness attributable to differing hemispheric albedo; different Saturnian moons, together with Titan, Tethys, Rhea, and Dione, are additionally seen.
- August thirty first options Venus close to the Beehive Cluster (M44) in Most cancers earlier than dawn; the First Quarter Moon passes Antares, offering a night viewing alternative.
- Observations of Delta Cephei, a Cepheid variable star in Cepheus, are recommended starting September 1st, encouraging observers to trace its brightness variations over a number of nights.
Sky This Week is dropped at you partly by Celestron.
Friday, August 29
The waxing Moon lies in southern Libra tonight. Our satellite tv for pc is shortly approaching Scorpius, the place it’ll meet the Scorpion’s brightest star in only a few days.
Excessive within the southeast within the few hours after sundown is the small constellation Sagitta the Arrow. It lies above the bigger, extra simply recognizable constellation Aquila the Eagle, which is marked by the intense star Altair (a part of the Summer time Triangle).
Tonight, we’re on the lookout for the globular cluster M71, an Eighth-magnitude ball of historic stars that sits roughly midway between Delta (δ) and Gamma (γ) Sagittae. Round 9:30 P.M. native daylight time, magnitude 3.8 Delta lies some 9.7° above magnitude 0.8 Altair. Magnitude 3.5 Gamma Sge lies simply to Delta’s higher left, about 3° away. M71 sits halfway between them, overlaying about 7’ on the sky. The cluster’s shiny central core is simple to identify with binoculars or a small scope, whereas increased magnification (or bigger scopes) will reveal an rising variety of stars. M71 is a comparatively loosely packed cluster, so notice how its look differs from denser objects, equivalent to M13 in Hercules.
M71 lies about 13,000 light-years away, and its shiny core covers a real diameter in area of about 24 light-years.
Dawn: 6:25 A.M.
Sundown: 7:36 P.M.
Moonrise: 12:53 P.M.
Moonset: 10:23 P.M.
Moon Section: Waxing crescent (36%)
*Occasions for dawn, sundown, moonrise, and moonset are given in native time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. native time from the identical location.
Saturday, August 30
Saturn’s moon Iapetus reaches biggest western elongation at present, now positioned 9.5’ west of the ringed planet. Iapetus has two vastly completely different hemispheres, one mild and one darkish. Because the moon orbits Saturn, it slowly rotates in order that one after which the opposite facet faces us, with its brightness various vastly relying on which area is pointed at Earth. At western elongation the icy, brighter facet of Iapetus is turned towards us, bringing the moon’s brightness as much as Tenth magnitude, consistent with a few of Saturn’s different moons (Rhea, Tethys, and Dione). Titan, at mid-Eighth-magnitude, remains to be brightest — we’ll ensure to find it tonight, too.
Saturn is rising within the east about an hour after sundown. Give it a bit time to climb out of the horizon haze after which level your scope at it late this night or in a single day into the early-morning hours. Round 11 P.M. native daylight time, it’s reached 25° in altitude within the east, hanging under the Circlet of Pisces and shining because the brightest level of sunshine in that area of the sky.
By way of a telescope, you’ll spot Titan some 3’ east of Saturn; once more, it’s the brightest of the planet’s moons. Then look far — a full 9.5’! — west of Saturn to identify Tenth-magnitude Iapetus. A lot nearer in, round midnight EST you’ll additionally see Tethys simply off the jap finish of the rings, with Rhea simply north of the rings additionally to the planet’s east. Dione lies west of the western fringe of the rings, with a lot fainter (twelfth magnitude) Enceladus between it and the sting of the rings. You could not be capable of spot Enceladus, so don’t be shocked in the event you can’t make it out.
There’s extra happening across the ringed planet this week — and all subsequent month, because it approaches opposition September 21 — so keep tuned. We’ll be again on this area of the sky quickly!
Dawn: 6:26 A.M.
Sundown: 7:34 P.M.
Moonrise: 1:56 P.M.
Moonset: 10:58 P.M.
Moon Section: Waxing crescent (45%)
Sunday, August 31
Brilliant Venus hangs close to the beautiful Beehive Cluster (M44) in Most cancers this morning. Each rise greater than two hours earlier than the Solar and attain practically 20° excessive within the east an hour earlier than dawn. Venus shines at magnitude –3.9, a blazing beacon simply 1.4° southwest (to the higher proper) of the Beehive.
At magnitude 3.1, M44 is seen to the bare eye, though viewing it this fashion whereas it’s low within the sky and twilight is approaching will likely be troublesome. As a substitute, strive for the intense, scattered stars of the Beehive with binoculars or your telescope’s finder scope. A small scope with a large discipline of view will even reveal a number of of its suns, and even catch Venus inside the view.
By way of a telescope, Venus exhibits off a 12”-wide gibbous disk that’s 84 p.c lit. What you’re seeing is daylight reflecting off the venusian cloud tops, because the planet is swathed in a thick blanket of carbon dioxide that each hides the floor from view and creates a strong greenhouse impact that heats the planet to some 870 levels Fahrenheit (465 levels Celsius).
First Quarter Moon happens at 2:25 A.M. EDT this morning. The Moon then passes 0.7° south of Antares at 7 A.M. EDT, though neither is seen at the moment. You may catch the pairing within the southern sky this night, with the waxing Moon now sitting about 7.5° to the left (southeast) of ruddy Antares within the darkening twilight. They continue to be above the horizon for a number of hours, setting round 11:30 P.M. native time.
Dawn: 6:27 A.M.
Sundown: 7:33 P.M.
Moonrise: 2:57 P.M.
Moonset: 11:41 P.M.
Moon Section: Waxing gibbous (54%)
Monday, September 1
Cepheid variables are a number of the most well-known variable stars within the sky, liable for serving to astronomers precisely measure cosmic distances and famously clueing Edwin Hubble in to the truth that the Andromeda Galaxy was far past the Milky Approach. So, tonight let’s start September by discovering the Cepheid variable that began all of it: Delta Cephei, the archetype Cepheid variable.
Associated: The star that modified the cosmos
If you understand how stellar names work, you’ll already know the place to seek out this star — it’s within the constellation Cepheus. The King lies excessive within the north after darkish right now of yr, his house-shaped define showing upside-down early within the night, then slowly rotating onto its facet because the hours progress. Cepheus is a circumpolar constellation, that means it seems to circle the North Celestial Pole (and the North Star, Polaris) reasonably than rise within the east and set within the west.
Two hours after sundown, Cepheus is 50° excessive within the north, standing on the highest of its peaked roof, marked by magnitude 3.2 Gamma Cep. The 2 stars marking the eaves of the home (on the high of its sq. form when rightside-up) are above Gamma right now — they’re magnitude 3.2 Beta (β) and magnitude 3.5 Iota (ι) Cep. Above Beta is magnitude 2.5 Alpha (α) Cep, and above Iota is magnitude 3.4 Zeta (ζ) Cep. It’s close to Zeta that we’ll lastly discover our goal, Delta Cep, which lies about 2.5° to Zeta’s northeast, or that star’s decrease proper early this night.
Delta Cep varies in brightness between magnitudes 3.6 to 4.3 over a interval of 5.three hundred and sixty six days. So, you should use Zeta as a comparability as soon as you discover the star — is Delta shut in brightness to Zeta, or is it notably fainter? When you’ve famous the relative magnitude, ensure to come back again daily for the subsequent a number of nights and watch whether or not it brightens or fades. When you’re skilled in taking astrophotos, strive taking a photograph every evening to chart the star’s adjustments; its cycle could also be simpler to comply with on a collection of photographs than together with your reminiscence and your eyes.
Dawn: 6:28 A.M.
Sundown: 7:31 P.M.
Moonrise: 3:55 P.M.
Moonset: —
Moon Section: Waxing gibbous (64%)
Tuesday, September 2
Mercury passes 1.2° north of Regulus at 6 A.M. EDT; the pair is seen within the east simply earlier than dawn, but it surely could be a difficult statement. You’ll wish to get to a location above the encircling terrain if attainable, with an jap horizon freed from tall timber or buildings.
Rising round 5:30 A.M. native daylight time, Mercury reaches an altitude of 4° roughly half an hour earlier than dawn. It’s now magnitude –1.3, which ought to assist it stand out in opposition to the brightening sky, though binoculars may enable you find it to the far decrease left of blazing Venus, which stands some 20° excessive right now. Magnitude 1.4 Regulus will likely be more difficult and should solely be seen with binoculars or a telescope, simply over a level to the decrease proper of Mercury within the sky as they’re rising. The star ought to be simply inside the similar discipline of view because the planet with a telescope, and positively inside a single binocular discipline.
When you’re utilizing a telescope, take a second to deal with Mercury as effectively. The tiny planet seems 5” broad — practically 2.5 instances smaller than Venus’ disk, at the moment — and is 90 p.c lit, barely greater than Venus’ 85 p.c. The latter, brighter planet hangs 2° straight under M44 this morning, so in the event you’d wish to catch a binocular view of the 2, you possibly can search for them a bit earlier, whereas the sky remains to be darkish — strive some 60 to 90 minutes earlier than dawn.
Word that it’s best to at all times put away any binoculars or telescope no less than a couple of minutes earlier than dawn happens out of your location, which can differ barely from the instances listed under.
Dawn: 6:29 A.M.
Sundown: 7:30 P.M.
Moonrise: 4:44 P.M.
Moonset: 12:33 A.M.
Moon Section: Waxing gibbous (73%)
Wednesday, September 3
With a waxing Moon lighting the sky for a lot of the evening, we’re specializing in brighter stars this night. Our goal for tonight is a well-known asterism that’s at the moment seen all evening lengthy. You may catch it already above the horizon within the east an hour after the Solar disappears, then comply with its progress because it arcs by way of the sky in a single day.
Look east an hour after sundown and also you’ll spot a big diamond of stars — that is the Nice Sq. of Pegasus, which depicts the physique of the Winged Horse. It’s bounded by 4 stars; lowest early within the night is magnitude 2.8 Gamma Pegasi. Shifting counterclockwise, some 16.5° to its higher proper (west) is magnitude 2.5 Markab (Alpha Peg). The subsequent star is Scheat (Beta Peg), which shines at magnitude 2.5 and sits roughly 13° north (to the higher left) of Markab. Because the Nice Sq. is Rising, Scheat seems on the high of the diamond, straight above Gamma.
Ending off the Nice Sq. is a star that isn’t really in Pegasus — it’s Alpheratz, Andromeda’s magnitude 2.1 alpha star, which lies simply over 14° east (to the decrease left) of Scheat.
Though the sky is shiny with moonlight tonight, taking the time to study the Nice Sq. will assist information your option to many fainter objects when the nights develop darker once more.
Dawn: 6:30 A.M.
Sundown: 7:28 P.M.
Moonrise: 5:27 P.M.
Moonset: 1:34 A.M.
Moon Section: Waxing gibbous (82%)
Thursday, September 4
We’re again at Saturn early this morning (or late on the third within the western half of the U.S.) to catch a transit of Titan along with its shadow throughout the ringed world.
The shadow transits first, starting at 1 A.M. EDT (once more, early on the 4th within the jap half of the U.S. however late on the third within the Mountain and Pacific time zones). Presently, Saturn is excessive within the southeast within the jap U.S., whereas appreciably decrease and within the east on the West Coast.
Watch by way of a telescope as Titan’s shadow slowly seems on the northeastern limb of the planet, taking some 25 minutes to completely emerge. Titan remains to be removed from the limb because it casts its shadow right now, as Saturn remains to be greater than two weeks from opposition. The moon’s shadow takes about two hours to achieve halfway throughout the disk (round 3 A.M. EDT), as Titan slowly closes in. Titan lastly begins its transit, which is able to carry it solely partially throughout Saturn’s northern polar area, round 5 A.M. EDT — not lengthy after the shadow has begun its half-hour-long disappearing act over on the northwestern limb. Titan’s shadow is absolutely gone from the disk by 5:15 A.M. EDT, and Titan’s partial transit ends quarter-hour later.
Tenth-magnitude Tethys can also be transiting this morning, crossing Saturn between about 4:30 A.M. EDT and 6:25 A.M. CDT (notice the time change, as dawn happens on the East Coast in the course of the transit). Planetary imagers would possibly be capable of decide up the small moon, whereas it could be invisible to visible observers. Its shadow will possible be indistinguishable as effectively.
The Moon passes 0.06° south of Pluto at 10 A.M. EDT.
Dawn: 6:31 A.M.
Sundown: 7:26 P.M.
Moonrise: 6:03 P.M.
Moonset: 2:40 A.M.
Moon Section: Waxing gibbous (89%)
Friday, September 5
Rising earlier than midnight and visual all morning lengthy till daybreak, the distant planet Uranus now resides inside the area of Taurus the Bull. Its present location makes it simpler than normal to seek out, simply 4.5° south-southeast of the Pleiades (M45). By 4 A.M. native daylight time, the area is a few 60° excessive within the east, above the easy-to-find three-star belt of Orion.
At the moment, you’ll discover Uranus to the decrease proper of the Pleiades. With binoculars, scan 4.5° due south of Alcyone (Eta [η] Tauri) to land on a pair of Sixth-magnitude stars in an east-west line. The easternmost star is 14 Tauri, and Uranus is slightly below 3° east of this star.
The ice large is at the moment 1.8 billion miles (2.9 billion kilometers) from Earth and spans 4” on the sky — small however decidedly nonstellar by way of a telescope. You could discover it seems “flatter” than the pinprick stars close by, and in addition exhibits off a grayish hue.
Uranus is creeping westward by way of the sky relative to the background stars, ever-so-slowly closing in on 14 Tau (and its jap associate, 13 Tau), passing south of this pair in December.
Dawn: 6:32 A.M.
Sundown: 7:25 P.M.
Moonrise: 6:34 P.M.
Moonset: 3:52 A.M.
Moon Section: Waxing gibbous (95%)
