Astro Bob: August calendar of night-sky highlights
A look at what the month has in store for stargazers.
August is a time of transition. After a long spell in the morning sky, Jupiter and Saturn become full-fledged evening planets that climb higher and become more obvious with each passing night. On Aug. 1, Saturn shines low in the southeastern sky at dusk, with Jupiter rising around 11 p.m. local time. By month's end, Jupiter pops its head out two hours earlier. The solar system's largest planet looks so bright you might mistake it for an airplane on its landing approach.
The red planet Mars slowly brightens, gaining almost half a magnitude this month as it continues to rise earlier and earlier. On Aug. 1, it glows low in the northeastern sky starting around 1 a.m. local time. By month's end look for it closer to midnight. Mars spends all of August near the familiar Pleiades star cluster, the one shaped like a small dipper. Early on, you'll find the planet about a fist to the right of the group. Later in the month it hangs below the Pleiades.
Venus heads in the direction of the sun and by next month will be lost in the glow of morning twilight. It's still easy to see during the first three weeks of August, low in the northeastern sky an hour to 45 minutes before sunrise. Mercury will be too near the sun to view this month.
During the first week of August, Mars and Uranus will be in conjunction, which will present a fine opportunity to spot the remote planet with binoculars with Mars lending a hand. You can download and print out a current map of the sky showing the positions of the evening planets and bright constellations at skymaps.com/downloads .
Although the full moon will spoil the month’s biggest astronomical event − the Perseid meteor shower − it won’t snuff it out. You’ll still see meteors, so don’t miss the show's peak on the Friday night, Aug. 12-13. Because it takes the Earth more than a month to fully cross the Perseid meteor stream, you'll seen at least a few Perseid meteors every night through the end of August. To confirm they belong to the shower, trace their paths backwards. If they lead to the radiant in Perseus just below the W of Cassiopeia, they're Perseids alright.
As the Big Dipper slides down into the northwestern sky this month, the summer constellations Sagittarius, Cygnus, Aquila and Lyra dominate the southern sky. But even as the season reaches its climax, winter sends us a reminder: mighty Orion and his three belt stars rise in the southeast before the start of morning twilight near month’s end.
*Note: When “a.m.” follows the date, it refers to an event visible in the morning sky after midnight. All times are Central Daylight Time (CDT) unless otherwise noted.
Aug. 1 – Mars in conjunction with Uranus, passing 1.4° to its south. With the help of the Red Planet, you can spot Uranus in a pair of binoculars. One degree is equal to the width of your little finger held at arm’s length against the sky. Most binoculars have fields of view of 5-6°.
Aug. 5 – First quarter moon
Aug. 11 – Full Sturgeon Moon
Aug. 11 – The full moon will pass about 5° below (south) of Saturn in conjunction. Moon-planet pairings like these are a great way to use the moon as a planet-finder.
Aug. 12-13 – Peak of the annual Perseid meteor shower. Were it not for the nearly full moon we might see some 60-80 meteors per hour. Bright moonlight will cut that number at least in half. No worries. It’s still well worth your while and fun to watch with family and friends. All you need is a reclining chair and a wide-open view of the night sky.
Whatever direction you choose to watch, be sure to face away from the moon to keep your eyes as dark-adapted as possible. I'd suggest facing north. Watch from 10 p.m. till dawn local time. The later you’re up the more meteors you’ll see.
Aug. 14 – Saturn reaches opposition, when it’s brightest and closest to Earth for the year. Tonight, it shines from a distance of 823.7 million miles (1.3 billion km). That's equal to 74 light-minutes or the time it takes light from the ringed planet to reach your eyes. Saturn resides in eastern Capricornus and rises into good view in the southeastern sky around 10-10:30 p.m. local time. It’s the only bright “star” in that direction. Telescopes will show the north face of Saturn’s famous rings, which are tipped 13° to our line of sight.
Aug. 14 – Waning gibbous moon passes 4° below Jupiter in conjunction
Aug. 18 – Last quarter moon
Aug. 19 a.m. – The waning moon passes 2° above (north) of Mars in conjunction. Use binoculars to see the Seven Sisters star cluster a few degrees to the moon’s upper left. A pretty trio!
Aug. 25 a.m. – A thin lunar crescent hovers 6° above Venus during mid-morning twilight. Venus has been approaching the sun all summer and sink into the bright glow of twilight later this month.
Aug. 27 – New Moon
Aug. 29 – Thin crescent moon returns to the evening sky. Watch for a sliver of light low in the west about 20 minutes after sunset.