#astronomy This Week’s Sky at a Look, July 16 – 24 – Sky & Telescope

July 17, 2021 - Comment

Nova Cas replace. It has been 4 months since Nova Cassiopeiae 2021 erupted to magnitude 7.7. It has stayed roughly that shiny ever since, making it formally a “gradual nova,” however with a brightness spike to five.5 in early Might and smaller bumps since. As of July 17th it was 7.four. Charts and comparability stars.

Nova Cas replace. It has been 4 months since Nova Cassiopeiae 2021 erupted to magnitude 7.7. It has stayed roughly that shiny ever since, making it formally a “gradual nova,” however with a brightness spike to five.5 in early Might and smaller bumps since. As of July 17th it was 7.four. Charts and comparability stars.


■ Venus continues to shine low within the western twilight this week. Tiny, distant Mars, a mere 1/200 as shiny, is sliding away to Venus’s decrease proper as proven beneath. In the meantime, twinkly Regulus, a half magnitude brighter than Mars, is quickly transferring in on Venus from the higher left.

Now Mars strikes away to the decrease proper from Venus, whereas brighter Regulus properties in on Venus from the higher left. Regulus will go 1° from Venus on the night of the 21st.

■ First-quarter Moon this night and tomorrow night (the Moon is strictly first quarter at 6:11 a.m. on July 17th EDT). Tonight, spot Spica about 6° to the Moon’s decrease left.


■ Now the eastward-marching Moon, nonetheless basically first-quarter, shines with Spica to its decrease proper.

■ Orange Antares and the remainder of starry Scorpius are highest within the south simply after darkish, with Antares about three fists left of the Moon. Do not let the moonlight cease you! Scorpius is shiny, and it is wealthy in double stars for binoculars and telescopes shiny sufficient to shine by means of. This is a rundown:

The top of Scorpius is the vertical row of three stars to the suitable of Antares. The highest of the row is Beta Scorpii, a nice telescopic binary: separation 13 arcseconds, magnitudes 2.eight and 5.zero.

Simply 1° decrease left of it’s the very extensive naked-eye pair Omega1 and Omega2 Scorpii, diagonal from higher proper to decrease left. They’re 4th magnitude and ¼° aside. Binoculars present their slight coloration distinction; they’re spectral varieties B9 and G2.

Higher left of Beta by 1.6° is Nu Scorpii, separation 41 arcseconds, magnitudes three.eight and 6.5. Actually this can be a telescopic triple. Excessive energy in good seeing reveals Nu’s brighter element itself to be an in depth double, separation 2 arcseconds, magnitudes four.zero and 5.three, aligned nearly north-south.

■ And the tail of Scorpius, the constellation’s different finish, is about two fists decrease left of Antares. Search for the 2 stars particularly shut collectively within the tail. These are Lambda and fainter Upsilon Scorpii, the Cat’s Eyes, zero.6° aside. They’re canted at an angle; the cat is tilting his head to the suitable and winking (Lambda is brighter than Upsilon; they’re magnitudes 1.6 and a couple of.6).

A line by means of the Cat’s Eyes factors proper or decrease proper by almost a fist towards Mu Scorpii, a a lot tighter pair referred to as the Little Cat’s Eyes. These are oriented nearly precisely the identical means as Lambda and Upsilon, however they’re solely zero.1° aside, and fainter: magnitudes three.zero and three.5. A cat six instances farther away?


■ Cassiopeia is now nicely previous its bottoming-out for the 12 months. Search for its tilted W sample slowly transferring up within the north-northeast. The farther north you reside, the upper it is going to be.


■ Now the waxing gibbous Moon is butting proper into the top of Scorpius, passing between Beta and Delta Scorpii throughout night for japanese and central North America. Antares is about 7° to the Moon’s decrease left.


■ Now the Moon shines a couple of fist over the Cat’s Eyes and the Little Cat’s Eyes. See July 17 above.


■ Low within the western twilight, Venus is now along side Regulus. The star glimmers just one/140 as shiny as Venus, about 1.1° decrease left of it as proven beneath.

Venus and Regulus are in conjunction this night, 1° aside. With binoculars, can you continue to choose up Mars 5° to their decrease proper? The visibility of faint objects in twilight is exaggerated right here.


Fourth star for the Summer season Triangle. The following-brightest star close to the Summer season Triangle is Rasalhague, the top of Ophiuchus.

First determine the Triangle. Face east quickly after darkish and crane your neck excessive to identify shiny Vega. Look two fists decrease left of it for Deneb. Three or 4 fists decrease proper of Vega is Altair.

Subsequent, Rasalhague. As you continue to face east, it is three fists to the suitable of Vega and three fists higher proper of Altair.

Admittedly, at 2nd magnitude it is not as shiny because the three Triangle stars. However embrace it and you have an enormous, flattened quadrilateral.


■ The Moon, simply after full, is up shining brightly within the east by late twilight. Search for Saturn a couple of fist at arm’s size to the Moon’s left.

By daybreak on the 24th they shift to the southwest and twist round in order that Saturn is above the Moon, as proven beneath.

The waning gibbous Moon passes Saturn, then Jupiter.


■ Now each Regulus and Mars are nicely right down to Venus’s decrease proper, by four° and seven° respectively as proven beneath . Bye-bye!

Deliver binoculars or a wide-field scope for a final strive on the two departing fainties.

■ And within the east after darkish, Saturn shines higher proper of the Moon and Jupiter shines farther to the Moon’s left. Once more, by daybreak this scene of motion shifts to the southwest and the sample turns into reoriented. See the graphic for daybreak on July 24–26 above.

■ As summer time progresses, shiny Arcturus strikes down the western aspect of the night sky. Its pale ginger-ale tint all the time helps determine it.

Off to Arcturus’s proper within the northwest, the Large Dipper scoops to the suitable.



This Week’s Planet Roundup

Mercury this week sinks even decrease down towards the east-northeast horizon in shiny daybreak. Nevertheless it does continues to brighten: from magnitude –zero.eight to –1.5.

Venus (magnitude –three.9) continues to shine low within the west throughout twilight. Decrease left of it’s tiny Mars, 200 instances fainter at magnitude +1.eight. Mars will get decrease every single day. Each planets set earlier than twilight ends.

Higher left of Venus you may discover Regulus early within the week, transferring nearer to Venus daily. It is brighter than Mars by a half magnitude, not even counting their completely different quantities of atmospheric extinction. It passes 1° from Venus on the 21st.

Saturn (magnitude +zero.2, in Capricornus) and brighter Jupiter (magnitude –2.eight, in Aquarius) rise within the east-southeast in twilight, Jupiter an hour after Saturn. By late night they make a formidable duo within the southeast. Jupiter will seize your eye first. Discover Saturn 20° to its higher proper.

They’re highest within the south, at their telescopic greatest, round 2 a.m. daylight saving time. See “Motion at Jupiter” within the July Sky & Telescope, web page 50, and “Saturnian Challenges” beginning on web page 52. They’re going to attain opposition subsequent month, in order that they’re already about as shut and massive as they’re going to get.

Uranus (magnitude 5.eight, in Aries) is nicely positioned within the east earlier than daybreak begins.

Neptune (magnitude 7.eight, in Aquarius 22° east of Jupiter) is increased within the south-southeast earlier than daybreak begins.

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 techniques than 99% of the individuals you may ever meet, see our compact article Time and the Newbie Astronomer.

Need to develop into a greater astronomer? Study your means across the constellations. They’re the important thing to finding every thing 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 large month-to-month map within the heart of every subject 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 fundamental customary is the Pocket Sky Atlas (in both the unique or Jumbo Version), which reveals 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 onerous covers and enlarged for simpler studying outdoor by crimson flashlight. Pattern charts. Extra concerning 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 you recognize your means round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.zero (stars to magnitude 9.75). And you should definitely learn how you can use sky charts with a telescope.

You may additionally desire a good deep-sky guidebook, similar to Sky Atlas 2000.zero Companion by Sturdy and Sinnott, or the larger (and illustrated) Evening Sky Observer’s Information by Kepple and Sanner.

Can a computerized telescope substitute charts? Not for newbies, I do not assume, and never on mounts and tripods which can 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 search out issues within the sky and understanding how the sky works. This information comes solely by spending time below the celebs with star maps in hand.”

Audio sky tour. Out below the night sky together 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 higher 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 might be far 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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