Northern Sky August 15-28
Now that we’re in the middle of August, it’s two months since the June solstice, and summer is
noticeably fading. But the good news is, the night sky is expanding, meaning the stars come out
earlier and fade away later.
In the predawn sky, Venus shines in the east as a brilliant morning star. A waning crescent moon
rose just above Venus the morning of August 15. On the 16th, the moon comes up next to Pollux,
the brighter of the Gemini twins. On the 17th the moon rises beneath the twins. That morning,
the bright star that rises off to the right of the moon and a little bit lower is Procyon, in Canis
Minor, the little dog. After the 17th, the moon disappears into the sun’s glare.
This month Venus has been pretty much holding its ground as the stars of Gemini and other
winter constellations stream past it. Also in the predawn sky is Mars, the lone bright light high in
the south. At the end of August, Mars’s opposition will be barely six weeks away. When Mars is
at opposition, Earth sweeps between the sun and the red planet, causing it to appear opposite the
sun in the sky. As that day approaches, Mars is brightening. It’s already brighter than Sirius, the
brightest star in the night sky, and its candlepower is still waxing. If you can’t wait to compare
Mars and Sirius, go outside close to dawn near the end of the month, when Sirius will be rising
in the southeast.
A new moon arrives on the 18th. At that moment the moon passes into the evening sky, but we’ll
have a few days before it gets bright enough to seriously interfere with watching stars and
planets. At nightfall in the southeast to south we have our old friends Jupiter and, off to the left,
Saturn. If you want to see them in the evening, remember that while Jupiter comes out around
sunset, Saturn doesn’t show up very well until the sky gets good and dark. These planets have
been moving away from each other and reach a maximum separation, 8.3 degrees, on August 28;
after that date, they start to draw closer. The distance between them will be steadily shrinking
until the winter solstice, when they make a very close pass. Also on August 28, a fat waxing
moon appears just below Jupiter.
In the neighborhood of these planets we have, low in the south to southwest, Scorpius, with
Antares, the bright red star at the scorpion’s heart. Immediately east is the Teapot of Sagittarius,
and then Jupiter. Above Jupiter is a curved line of stars known as the Teaspoon. It sits above the
giant planet like a hat. If you go outside around 11 o’clock, Mars will be low in the east, Jupiter
and Saturn in the south, and you can see three planets at once.
But back to nightfall. Look to the west for the brilliant star Arcturus, which anchors the kite-
shaped constellation Bootes, the herdsman. This time of year, the kite stands upright above the
horizon as Arcturus seems to drag it down like a stone.
Above and east of Jupiter and Saturn is the big Summer Triangle of bright stars. Just a few words
about the star at the Triangle’s southern vertex. This is Altair, sandwiched between two dimmer
stars in the constellation Aquila, the eagle. Altair is close; only about 17 light-years away. It’s
famous for rotating very fast—once every 10 hours, or more than twice as fast as Earth. This has
flattened Altair into a shape not unlike that of a pumpkin.