Messier 11
Messier 11 is a cluster that contains about 3,000 stars packed into a small volume of space. It’s in the southeast this evening, to the upper left of teapot-shaped Sagittarius. Under dark skies, M11 is just visible to the unaided eye.
Delta Scuti
As night falls, Scutum, the shield, stands above the teapot outline of Sagittarius. One of its stars, Delta Scuti, pulses in and out like a beating heart. That makes the star’s brightness vary by about 20 percent every 4.5 hours.
The Dolphin’s Snout
A pretty binary star system climbs across the southern sky on summer nights. Gamma Delphini represents the snout of Delphinus, the dolphin. The little constellation is in the east as night falls, with the snout on the left and the tail on the right.
Moon and Aldebaran
The Moon will flirt with Aldebaran, the brightest star of Taurus, the next couple of mornings. The star will stand to the lower left of the Moon at first light tomorrow, and about the same distance to the upper right of the Moon the next day.
Distant Planet
The constellation Virgo is in the southwest at nightfall. Astronomers recently discovered a big, heavy planet orbiting one of its stars, HR 5183. The system is about 100 light-years away.
Last-Quarter Moon
The Moon reaches last quarter at 8:18 p.m. CDT. It lines up at a right angle to the line between Earth and Sun, so sunlight illuminates exactly half of the lunar hemisphere that faces our way.
Outcast Stars
The Big Dipper is in the northwest this evening, with the handle above the bowl. The five stars in the middle of the dipper are all related, but the stars at the tip of the handle and lip of the bowl move through the galaxy independently of the others.
Starry Sky
When darkness falls tonight the sky will come alive with stars: the Summer Triangle up in the east, the scorpion low in the south, and the stars of spring sliding from view in the west.
Dog Days
Mid-summer is called the Dog Days because the “dog star,” Sirius, appears near the Sun. Since Sirius is the brightest star in the night sky, ancient skywatchers associated it with especially hot days.
Touchdown!
The first astronauts landed on the Moon on July 20, 1969. And this year the Moon is at its greatest separation from Earth for the month on the 50th anniversary of that date, roughly 13,000 miles farther than the average distance of 239,000 miles.