The Sky This Week from August 16 to 25 – Astronomy Magazine
Sagittarius above a Cape Cod beach house
The famous Teapot asterism in Sagittarius stands out to the upper right of this vacation home, while the central regions of the Milky Way arc through the top of the image.
John Chumack
Asteroid 15 Eunomia reached opposition and peak visibility just four days ago, and the view tonight is essentially the same. The main-belt object traverses the sky from dusk to dawn and climbs halfway to the zenith in the southern sky around 1 a.m. local daylight time. Eunomia shines at magnitude 8.2 and should be easy to find through binoculars under a dark sky and in a 4-inch telescope from the suburbs. The asteroid is currently moving westward against the backdrop of Aquarius the Water-bearer. Tonight, it lies 4.3° due west of magnitude 2.9 Beta (β) Aquarii.
Saturday, August 17
Mercury reached greatest western elongation August 9, but it is actually easier to see before dawn this weekend. The innermost planet rises nearly 90 minutes before the Sun and climbs 6° high in the east-northeast 45 minutes before sunup. But the reason it is so simple to see is because it shines so brightly. At magnitude –0.9, it appears more than twice as bright as it did at greatest elongation. If you have trouble spotting the planet with your naked eye, scan the area with binoculars. When viewed through a telescope, Mercury shows a disk that spans 6.2″ and appears about two-thirds lit.
The Moon reaches apogee, the farthest point in its orbit around Earth, at 6:49 a.m. EDT. It then lies 252,429 miles (406,244 kilometers) from Earth’s center.
Sunday, August 18
For those of you up for an observing challenge, try to spot Pluto this evening. The dwarf planet glows at 14th magnitude and shows up as a faint pinprick of light through 8-inch or larger telescopes from under a dark sky. The key is to have a go-to telescope or be able to star-hop from a relatively bright (though still dim) star. Tonight offers a prime opportunity, as Pluto slides 12′ due north of magnitude 9.4 HD 183431. And tomorrow night, the distant world slides just 2′ north of a magnitude 10.5 field star.
Monday, August 19
Evenings this week are great times to explore the constellation Sagittarius the Archer. This star group lies due south and at peak altitude around 10 p.m. local daylight time, shortly after the last vestiges of twilight have faded away. The brightest stars within the constellation form the shape of a teapot — a distinctive asterism once you’ve found it. The central regions of the Milky Way pass through Sagittarius, so it’s always worth exploring the area through binoculars or a telescope.
