This Week’s Sky at a Glance, May 14 – 22

UPDATE: Nova Cassiopeiae 2021 abruptly shot as much as magnitude 5.4 round May eighth making it faintly seen to the bare eye in a darkish sky a full eight weeks after its preliminary outburst to magnitude 7. It had remained at Seventh or eighth magazine all throughout the interim. As of May 14th it light again a bit to about magazine 5.8. See Nova in Cassiopeia Brightens Suddenly, with finder charts and comparability stars.

The nova is low within the north within the night however excessive within the northeast earlier than the primary beginnings of daybreak. Set your alarm to go look at least two hours earlier than your native dawn time.


FRIDAY, MAY 14

■ Find Mercury and Venus low within the west-northwest in twilight this week. The first of them it’s possible you’ll spot is Venus, brilliant at magnitude –3.9, very low precisely west-northwest. As the sky darkens, Mercury will become visible about 8° above Venus as proven under. Mercury retains fading this week, from magnitude +0.2 to +1.0. Meanwhile, little Mars stays to their higher left. And this night, the crescent Moon hangs in between.

The bulge of the crescent Moon factors the way right down to Mercury and Venus, even because the Moon pairs up with Mars. (The Moon is these scenes is drawn about 3 times its precise obvious measurement. Positions are precise for an observer at latitude 40° N, longitude 90° W, close to the inhabitants heart of North America; your association might differ barely. And bear in mind, the visibility of faint objects in brilliant twilight is exaggerated right here.)

SATURDAY, MAY 15

■ Now the crescent Moon shines with faint, distant Mars, as proven above. Mars is sort of on the alternative aspect of its orbit from us, 18 light-minutes away in comparison with the Moon’s 1.3 light-seconds.

■ Summer continues to be 5 weeks off, however the Summer Triangle is making its look within the east, one star after one other.

Its first star in view is brilliant Vega, within the northeast as twilight fades. Next is Deneb, decrease left of Vega by a little greater than two fists at arm’s size. The third nook of the triangle is Altair. It rises within the east, far to the decrease proper of Vega and Altair, round 11 p.m.

SUNDAY, MAY 16

■ Meanwhile, Arcturus is the brightest star very excessive within the east. Spica shines decrease proper of it by about three fists at arm’s size. Look to the precise of Spica by half that distance for the distinctive four-star constellation of Corvus, the springtime Crow.

More on Arcturus? See the June Sky & Telescope, web page 45, for the “many distinctions” of this star.

MONDAY, MAY 17

■ What is the oldest factor you will have ever seen? For everybody on the earth it is at least the Sun and different objects of the solar system, age 4.6 billion years. Everything on or close to the Earth’s floor is way youthful.

Next is Arcturus, which most individuals have certainly seen whether or not they knew it or not, because it’s one of many brightest stars within the sky. It’s a Population II orange large, age about 7 billion years, simply passing by way of our area of the Milky Way.

Amateur astronomers have globular clusters. Most are older nonetheless, at least partially. The white dwarfs within the acquainted M4 in Scorpius have been dated at 12.7 ±0.7 billion years.

But particular person stars that you would be able to observe? For that you really want Bob King’s new article In Search of Ancient Suns, with finder charts. Assigning dates to particular person stars from the primary eras after the Big Bang continues to be iffy; astronomers need to work from the near-absence of heavy parts of their spectra. But a comparatively close by Sixth-magnitude star in Bootes and a Seventh-magnitude star in Libra, each in binocular vary, await you these May and June evenings. They most likely date from about 12½ billion and at least 13 billion years in the past, respectively. These will most likely be the oldest issues you will have ever seen, or will. The Big Bang itself is nicely dated at 13.8 billion years.

One may choose nits. Pick a proton, any proton proper in entrance of you, and it has very seemingly remained intact because the Big Bang’s first millionth of a second. And what a variegated historical past it has seen since then!

TUESDAY, MAY 18

■ This night the Moon hangs in western Leo, under the entrance of the Sickle as proven under.

As quickly as evening is totally darkish, look nearly two fists at arm’s size under the Moon for the dim head of Hydra.

The Moon steps throughout Leo because it passes by way of first quarter, similar to it does each May.

WEDNESDAY, MAY 19

■ First-quarter Moon (precisely so at 3:13 p.m. EDT). This night it shines over Regulus, as proven above.

THURSDAY, MAY 20

■ The gibbous Moon a day or two previous first quarter is, I feel, my favourite part to look at. The terminator crosses every kind of wealthy but acquainted lunar territory, and the Moon is highest within the handy night hours.

Did you recognize there are seven classical crater varieties? Pre-space-age, these classes spanned every little thing from the most important “walled plains” to the tiniest telescopic “crater pits.” This stepwise classification reigned from 1837 till 1960, when space science was turning extra severe and the affect concept of crater origins lastly displaced the extensively assumed volcanism of earlier generations.

But the previous descriptors nonetheless work for telescopic observers. Explore them, with examples, utilizing the article within the June Sky & Telescope, web page 52.

FRIDAY, MAY 21

■ Vega is now properly up within the east-northeast after darkish. Look for its faint little constellation Lyra, the Lyre, dangling down from it with its backside canted to the precise. Lyra’s fundamental stars type a little equilateral triangle (Vega is one nook) and a parallelogram hooked up to the triangle’s backside star.

SATURDAY, MAY 22

■ Vega is the brightest star within the east-northeast after darkish. Look 14° (about a fist and a half at arm’s size) to its higher left for Eltanin, the 2nd-magnitude nostril of Draco the Dragon. Closer above and higher left of Eltanin are the three fainter stars forming the remainder of Draco’s stick-figure head, additionally known as the Lozenge. Draco all the time factors his nostril to Vega, regardless of how he is oriented. He appears interested by it. Do dragons eat jewels? He has made no transfer on it but.

The faintest star of Draco’s head, reverse Eltanin, is Nu Draconis. It’s a high quality, equal-brightness double star for binoculars (separation 61 arcseconds, each magnitude 4.9). The pair is 99 light-years away. Both are scorching, chemically peculiar type-Am stars considerably bigger, hotter, and extra large than the Sun.

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This Week’s Planet Roundup

Mercury and Venus become visible within the west-northwest within the afterglow of sundown. You might first spot Venus, brilliant at magnitude –3.9, very low. Look about 30 or 40 minutes after sunset to catch it earlier than it units.

As the sky darkens additional, Mercury comes into view about 8° above or higher left of Venus. Mercury is getting fainter; it fades from magnitude +0.2 to +1.0 this week.

Mars (magnitude +1.7, in Gemini) glows within the west-northwest proper after darkish. It’s lower than midway from Procyon (left of it) to Capella (farther proper of it). In a telescope Mars is a mere 4.4 arcseconds broad: simply a tiny, shimmering blob.

Jupiter and Saturn (in dim Aquarius and Capricornus, respectively) are nicely up within the southeast earlier than the primary mild of daybreak. Jupiter grabs consideration at magnitude –2.3. Saturn, 17° to Jupiter’s proper, is one sixteenth as brilliant at magnitude +0.7.

Jupiter on May 2nd. South right here is up. The “eyeliner” marking under the Great Red Spot is unusually darkish. The South Equatorial Belt (which the eyeliner indents into) stays fairly pale. And word the small white spot higher proper (south following) from the GRS, within the South Temperate Belt. Image by Christopher Go.
A mutual occultation of Jupiter’s moons. “I was able to capture a rare occultation of Callisto by Europa with Ganymede close by,” writes Christopher Go. In the 21 minutes from the primary to 3rd body, small, bright-surfaced Europa moved off the sting of bigger, dark-surfaced Callisto whereas Ganymede occurred to be slightly below. The date was April twenty ninth.

We’re in a season of such mutual eclipses of Jupiter’s moons; see predictions for this month within the May (*22*), web page 50. Will you be fortunate sufficient to have one happen whereas Jupiter is in its transient pre-dawn view out of your location? Don’t anticipate your scope to resolve Jupiter’s moons into disks like this visually!

Uranus is hidden within the glow of daybreak.

Neptune continues to be low within the east as 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.

Eastern Daylight Time, EDT, is Universal Time minus 4 hours. Universal Time is also referred to as UT, UTC, GMT, or Z time. To turn into extra skilled about time programs than 99% of the individuals you will ever meet, see our compact article Time and the Amateur Astronomer.


Want to turn into a higher astronomer? Learn your way across the constellations. They’re the important thing to finding every little thing fainter and deeper to hunt with binoculars or a telescope.

This is an out of doors nature interest. For an easy-to-use constellation information overlaying the entire night sky, use the large month-to-month map within the heart of every challenge 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 primary commonplace 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 a whole lot 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 outside by red flashlight. Sample charts. More about the current editions.

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 you recognize your way round, are the even bigger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to magnitude 9.75). And you’ll want to learn how to use sky charts with a telescope.

You’ll additionally need a good deep-sky guidebook, reminiscent of 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 inexperienced persons, I do not assume, 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 (*14*), “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 underneath the night sky together with your
earbuds in place, hearken 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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