This Week’s Sky at a Glance, June 18 – 26

Nova Cassiopeiae carries on. It’s been three months since Nova Cas 2021 erupted to magnitude 7.7. Surprisingly, it has stayed roughly that brilliant ever since aside from swelling to five.3, faint naked-eye visibility, for a week in early-mid May earlier than dropping again to 7.7. As of June seventeenth it had crept again as much as 6.8.

The nova is pretty effectively up within the north-northeast proper after darkish, relying in your latitude. It climbs larger via the evening. Charts and comparison stars.

And now, Nova Herculis. On June twelfth Seiji Ueda of Japan found an 8.4-magnitude nova at the Hercules-Aquila border. Within hours Nova Herculis 2021 reached 6.3, then started fading quick. As of June seventeenth it was right down to 9.5 visually. It’s distinctly red. See Bob King’s Bright Nova in Hercules on a Roller Coaster Ride, with charts.


■ This night the Moon shines near Third-magnitude Gamma (γ) Virginis (Porrima), proven beneath. Gamma Vir is a beautiful equal-brightness double star for telescopes. Its elements are 3.1 arcseconds aside this year and widening barely year by year. They’re each type-F1 stars considerably bigger and warmer than the Sun, shining to us from 39 light-years away.

The Moon shines with Gamma Virginis on the 18th, then over Spica on the nineteenth. It will not really seem this near the stars; the Moon right here is at all times drawn about 3 times its precise obvious dimension.

■ We’re coming into the time of year when the 2 brightest stars of summer time, Arcturus and Vega, are about equally excessive overhead as night grows late: Arcturus towards the southwest, Vega towards the east.

Arcturus and Vega are 37 and 25 light-years away, respectively. They signify the 2 commonest sorts of naked-eye star: a yellow-orange Okay big and a white A main-sequence star. They’re 150 and 50 instances brighter than the Sun, respectively — which, mixed with their nearness, is why they dominate among the many night stars.


■ Spica (260 light-years away) shines beneath the Moon, as proven above.

Much larger above them is brighter Arcturus. Spica is pale, icy blue-white. Arcturus is candleflame yellow-orange.


■ We go via the solstice in the present day at 11:32 p.m. EDT. This is when the Sun is farthest north for the year (in Earth’s sky) and begins its six-month return southward. Summer formally begins within the Northern Hemisphere, winter within the Southern Hemisphere. For us northerners, that is the year’s longest day and shortest evening.

It’s additionally the day when (within the north temperate latitudes) the noon Sun passes the closest it ever can to being straight overhead, and thus when your shadow turns into the shortest it may well ever be at your location. This occurs at your native obvious [solar] midday, which might be rather far removed from midday in your civil time (clock time).

And when you have a good west-northwest horizon (in mid-northern latitudes), mark fastidiously the place the Sun units. In a few days it’s best to be capable to detect that the Sun is once more beginning to set a simply little south (left) of that time.


■ After dusk, search for the Big Dipper hanging straight down excessive within the northwest. Its backside two stars, the Pointers, level decrease proper towards modest Polaris, the tip of the Little Dipper’s deal with.

Examine the center star of the Big Dipper’s deal with, Mizar. Can you see its faint little companion Alcor nestled subsequent to it? It’s simply higher proper of Mizar — pointing, as at all times, the course from Mizar to Vega.


■ The nearly-full Moon shines over Antares this night. By 11 or midnight they’re due south on the meridian, as proven beneath, which means that Scorpius is as excessive because it will get. In addition to Antares, how a lot else of the constellation are you able to make out via the moonlight?

Moon over Scorpius, June 22, 2021
The full Moon of June known as the Honey Moon as a result of it rides low throughout the sky via the evening, the place summer time humidity-haze usually colours it yellow. Above, the Moon is getting very near when it is full on the twenty fourth. (The 10° scale is in regards to the dimension of your fist at arm’s size, a helpful angular measure.)


■ Mars is passing via the center of the Beehive Star Cluster, M44, this night for North America. Get your binoculars or low-power, wide-field telescope on Mars, very low within the west-northwest, proper at the tip of nightfall. (Faint Mars is a fist at arm’s size higher left of brilliant Venus.) At nightfall at different longitudes world wide, Mars can be extra towards one fringe of the cluster.

Almost there. . . . Venus traces up with Castor and Pollux in another day, on Thursday the twenty fourth, identical to Mars did on June seventh.


■ Full Moon (precise at 2:40 p.m. EDT). The Moon rises in twilight about a half hour after sundown. After darkish, you will see that it is within the fringe of the Sagittarius Teapot when you can see the Teapot’s 2nd and Third-magnitude stars via the moonlight! Binoculars assist. Remember, the Teapot (12° large) way overspills a binocular’s discipline of view (usually 6° or 8° or so).


■ Leo the Lion is generally a constellation of late winter and spring. But he isn’t gone but. As twilight ends look due west, considerably low, for Regulus, his brightest and now lowest star: the forefoot of the Lion stick determine. The Sickle of Leo extends higher proper from Regulus.

The remainder of the Lion’s constellation determine runs higher left from there for nearly three fist-widths, to his tail star Denebola, the best. He’ll quickly be treading offstage into the sundown.


■ On the japanese facet of the sky, the massive Summer Triangle holds sway after darkish. Its high star is Vega, the brightest in all of the east. The brightest to Vega’s decrease left is Deneb. Farther to Vega’s decrease proper is Altair. The Milky Way (when you have a darkish sky) runs alongside the Triangle’s decrease edge.

As night grows later and even Altair rises excessive, look left of Altair, by hardly greater than a fist, for the compact little constellation Delphinus, the Dolphin.

Did you notice it? Then attempt for even fainter, smaller Sagitta, the Arrow, to Altair’s higher left and simply a little nearer. The Arrow goals decrease left, previous the nostril of Delphinus.


This Week’s Planet Roundup

Mercury hides very low within the glow of daybreak.

Venus (magnitude –3.8, in Gemini) shines low within the west-northwest throughout twilight. It hardly strikes now with respect to your panorama from week to week, however its background stars are actually transferring proper alongside. Watch Castor and Pollux, to Venus’s proper, place themselves to line up with the dazzling planet on June twenty fourth.

Mars (magnitude +1.8, in Cancer) glows very modestly in late twilight low within the west-northwest, higher left of Venus. Mars is about as faint and small as it may well ever get, glimmering with only one/175 of Venus’s gentle. The two planets slender from 14° aside on June 18th to 10° on the twenty fifth. They’ll attain conjunction, ½° aside, on July twelfth and thirteenth.

On the twenty third Mars is smack in entrance of the fragile Beehive Star Cluster, M44.

Jupiter and Saturn (in Aquarius and Capricornus, respectively) rise in the course of the evening, Jupiter about an hour after Saturn. They shine at their highest and telescopic finest in early daybreak, a time when the atmospheric seeing usually steadies. Jupiter dominates at magnitude –2.5. Saturn, 20° to Jupiter’s proper, is a extra modest +0.5. They’ll attain opposition in August.

As daybreak begins, look 20° beneath Jupiter for Fomalhaut, the “Autumn Star.” It’s rising from the dawn glow even earlier than the official begin of summer time.

Jupiter’s Great Red Spot was crossing the planet’s central meridian on May twenty first when Christopher Go took this stacked-video picture centered on 21:09 UT (when the System II central-meridian longitude was 358°). South is up.

Lower proper of the Red Spot are two of Jupiter’s satellites: darkish gray Ganymede and smaller, brilliant orange Io with its darker polar areas. The black circle decrease left of the Red Spot is Io’s shadow. (The distinction of this picture has been boosted.)

Uranus (magnitude 5.8, in Aries) is low within the east simply earlier than daybreak begins.

Neptune (magnitude 7.9, in Aquarius 20° east of Jupiter) is effectively up within the southeast earlier than daybreak.

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.

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 knowledgeable about time methods 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 every thing fainter and deeper to hunt with binoculars or a telescope.

This is an outside nature pastime. For an easy-to-use constellation information overlaying the entire night sky, use the massive month-to-month map within the heart of every concern 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 exhibits stars to magnitude 7.6.

Pocket Sky Atlas cover, Jumbo edition
The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6, and lots of of telescopic galaxies, star clusters, and nebulae amongst them. Shown right here is the Jumbo Edition, which is in exhausting covers and enlarged for simpler studying outdoor by red flashlight. Sample charts. (*18*).

Next up is the bigger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; almost 3 times as many. The subsequent up, as soon as your way round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And make sure to learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, similar to Sky Atlas 2000.0 Companion by Strong and Sinnott, or the larger (and illustrated) Night Sky Observer’s Guide by Kepple and Sanner.

Can a computerized telescope exchange charts? Not for rookies, I do not suppose, and never on mounts and tripods which are 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 cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand.”

Audio sky tour. Out beneath 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’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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