#astronomy This Week’s Sky at a Look, July 23 – 31 – Sky & Telescope

July 25, 2021 - Comment

Nova Cas would not stop. 4 months in the past Nova Cassiopeiae 2021 erupted to magnitude 7.7. It has largely stayed about that brilliant ever since — a “gradual nova” — however with a brightness spike to five.5 in early Might and smaller bumps since. As of July 25th it again as much as 6.four.

Nova Cas would not stop. 4 months in the past Nova Cassiopeiae 2021 erupted to magnitude 7.7. It has largely stayed about that brilliant ever since — a “gradual nova” — however with a brightness spike to five.5 in early Might and smaller bumps since. As of July 25th it again as much as 6.four. Charts and comparability stars.


■ Full Moon (precise at 10:37 p.m. EDT). The Moon is up within the east by late twilight. Search for Saturn a couple of fist at arm’s size to its left. Later after darkish, Jupiter rises farther to the Moon’s decrease left.

By daybreak on the 24th, this group shifts to the southwest and twists clockwise in order that Saturn is above the Moon, as proven under.

Full Moon passing Saturn and Jupiter as seen at dawn, July 24-26, 2021. The Moon passes Saturn, then Jupiter, when it is full and because it turns waning gibbous.


■ Now each Regulus and Mars are effectively all the way down to Venus’s decrease proper, by four° and seven° respectively as proven under. Bye-bye!

Venus, Regulus and Mars very low in the western twilight, July 24, 2021.Venus marks the low west in twilight. Carry binoculars or a wide-field scope for one final attempt at Regulus and even-dimmer Mars.

■ And within the east after darkish, Saturn now shines higher proper of the Moon, and Jupiter shines farther to the Moon’s left. Once more, by daybreak on the 25th this scene of motion shifts to the southwest and twists clockwise. See the graphic for daybreak on July 24–26 above.

■ As summer time progresses, brilliant Arcturus strikes down the western aspect of the night sky. Its pale ginger-ale tint at all times helps determine it. Off to Arcturus’s proper within the northwest, the Huge Dipper scoops to the correct.


■ Look once more to Arcturus excessive within the west. In astronomy lore at this time, Arcturus could also be finest identified for its cosmic historical past: It is an orange big some 7 billion years previous, older than the photo voltaic system, racing by our a part of area on a trajectory that signifies it was born in one other galaxy: a dwarf galaxy that fell into the Milky Manner and merged with it.

However within the astronomy books of our grandparents, Arcturus had a special declare to fame: It turned on the lights of the 1933 World’s Honest in Chicago celebrating “a century of progress.” Astronomers rigged the newly invented photocell to the attention finish of massive telescopes across the US and aimed them the place Arcturus would go on the appropriate second on opening night time. The star’s mild crept onto the cells, the weak alerts had been amplified and despatched over telegraph wires to Chicago, and on blazed the huge lights to the cheers of tens of hundreds.

Why Arcturus? Astronomers of the time thought its was 40 light-years away (fashionable worth: 36.7 ±zero.2). So the sunshine would have been in flight since Chicago’s earlier such occasion, the World’s Columbian Exhibition in 1893.

And earlier? Arcturus was the primary of the acquainted nighttime stars to be seen within the daytime with a telescope: by Jean-Baptiste Morin in 1635.


■ With the advance of summer time, the Sagittarius Teapot, within the south after darkish now, is tilting and pouring from its spout to the correct. The Teapot will tilt farther and farther for the remainder of the summer time — or for a lot of the night time if you happen to keep out late.


Homing in on Hebe. The asteroid 6 Hebe is simply previous opposition, a magnitude eight.four pinpoint north of the Sagittarius Teaspoon. A pair of 10×50 or bigger binoculars, used very fastidiously below a darkish sky earlier than moonrise, could also be sufficient so that you can choose it out utilizing the finder chart within the July Sky & Telescope, web page 50. (The chart there exhibits Hebe’s place for zero:00 UT on the dates indicated, which falls on the night of the earlier date for North America.)


■ The lengthy, drawn-out Southern Delta Aquariid meteor bathe ought to peak someday round this date, although the sunshine of the waning gibbous Moon will intrude late tonight.

And talking of lengthy, drawn-out meteor showers, the Perseids have already begun. For now you may solely see the very occasional Perseid throughout the course of your observing periods, however their numbers are steadily rising. The bathe is because of peak on the night time of August 11-12 below near-perfect moonless circumstances. See the August Sky & Telescope, web page 48.


Sundown problem. I’ve stated Regulus and Mars are disappearing for the season all the way down to Venus’s decrease left. Nicely, if you would like one final problem, Regulus and Mars this night are in conjunction, zero.6° aside.

Get Venus in your lowest-power, widest-field eyepiece as quickly after sundown as you’ll be able to. Then shift to look at eight° to Venus’s decrease proper to see whether or not you’ll be able to choose up Regulus and fainter Mars earlier than they get too low and set within the fading twilight, as proven right here:

Mars and Regulus are in conjunction. Good luck.

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 brilliant 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 correct of Vega and three fists higher proper of Altair.

Admittedly, at 2nd magnitude it is not as brilliant because the three Triangle stars. However embrace it and you have a large, flattened quadrilateral.


■ As summer time progresses, Arcturus strikes down the western aspect of the night sky. Arcturus kinds the underside level of the Kite of Bootes. The Kite, fairly slender, extends higher proper from Arcturus by 23°, about two fists at arm’s size. The decrease proper aspect of the kite is dented inward, as if some celestial intruder as soon as banged into it.


Saturn is at opposition tomorrow night time. Do you already discover that Saturn’s rings are distinctly brighter, in comparison with Saturn’s globe, than they normally are? This Seeliger impact is attributable to the stable ring particles backscattering daylight to us when the Solar is sort of immediately behind us. The dusty surfaces of the Moon and Mars do that too, however Saturn’s clouds don’t. Within the case of Saturn the impact is called for Hugo von Seeliger, who studied it intimately and printed his findings in 1887.



This Week’s Planet Roundup

Mercury is out of sight deep within the glow of dawn.

Venus (magnitude –three.9) continues to shine low within the west throughout twilight. It units round twilight’s finish.

Mars is disappearing from sight deep within the sundown, decrease proper of Venus.

Saturn (magnitude +zero.2, in Capricornus) and brighter Jupiter (magnitude –2.eight, in Aquarius) shine within the east-southeast as the celebs come out. Saturn is a lone, regular yellowish level. Jupiter shines brighter about two fists at arm’s size to Saturn’s decrease left. By late night they make a formidable duo greater within the southeast. They’re highest within the south, at their telescopic finest, round 1 or 2 a.m. daylight saving time.

Saturn reaches opposition on August 1st, Jupiter on August 19th, so that they’re already primarily as shut and massive as they’re going to get. See “Motion at Jupiter” within the July Sky & Telescope, web page 50, and “Saturnian Challenges” beginning on web page 52. Additionally “Canine Days with the Fuel Giants” within the August subject, web page 49.

Jupiter on July 12, 2021Jupiter on July 12th, imaged by Christopher Go. South is up. The South and North Equatorial Belts have largely diminished to skinny darkish traces. Pink barges and spots proceed simply north of the NEB. A lot of the Equatorial Zone continues pale yellow-tan. The Nice Pink Spot is on the opposite aspect of Jupiter, however word the row of white ovals within the south temperate space.

Uranus (magnitude 5.eight, in Aries) is excessive within the east-southeast earlier than daybreak begins.

Neptune (magnitude 7.eight, in Aquarius 23° east of Jupiter) is excessive within the south 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 depend upon longitude (primarily Moon positions) are for North America.

Jap Daylight Time, EDT, is Common Time minus four hours. Common Time is also called UT, UTC, GMT, or Z time. To grow to be extra professional about time techniques than 99% of the individuals you may ever meet, see our compact article Time and the Novice Astronomer.

Need to grow to be a greater astronomer? Be taught your method 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 outside nature interest. For an easy-to-use constellation information overlaying the entire night sky, use the massive month-to-month map within the middle 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 essential customary is the Pocket Sky Atlas (in both the unique or Jumbo Version), which exhibits stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo editionThe Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and a whole lot of telescopic galaxies, star clusters, and nebulae amongst them. Proven right here is the Jumbo Version, which is in arduous covers and enlarged for simpler studying open air by crimson flashlight. Pattern charts. Extra in regards to 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 method round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.zero (stars to magnitude 9.75). And remember to learn use sky charts with a telescope.

You may additionally need a good deep-sky guidebook, reminiscent of Sky Atlas 2000.zero Companion by Robust and Sinnott, or the larger (and illustrated) Night time Sky Observer’s Information by Kepple and Sanner.

Can a computerized telescope substitute charts? Not for newcomers, 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 Yard Astronomer’s Information, “A full appreciation of the universe can not come with out creating the abilities to search out issues within the sky and understanding how the sky works. This data comes solely by spending time below the celebs with star maps in hand.”

Audio sky tour. Out below the night sky along with your
earbuds in place, take heed to Kelly Beatty’s month-to-month
podcast tour of the heavens above. It is free.

“The hazards of not considering clearly are a lot higher now than ever earlier than. It is not that there is one thing new in our mind-set, it is that credulous and confused considering could be far more deadly in methods it was by no means earlier than.”
            — Carl Sagan, 1996

“Details are cussed issues.”
            — John Adams, 1770


Supply hyperlink


Comments are disabled for this post.