If you're an early riser, the sky just before dawn this month is a spectacular sight. You don't need binoculars or a telescope to enjoy it, though of course those items make it even better, and the farther away you are from the light pollution the more spectacular the viewing will be. Those of you in the Playa Encanto area are to be envied.
On July 17- 19 the waning crescent Moon anchors a beautiful display low in the eastern sky, showcasing the Pleiades, Venus, Mars and the star Aldebaran. The Moon is above the others on the morning of the 17th, beside Mars on the 18th, and to the left of Venus on the 19th. Aldebaran stays to the right of Venus.
So big and bright that people often mistake it for a UFO, Venus, the "morning star", rises a couple hours before sunrise right now. On the 18th you will see it to the right of the Moon. The orange star Aldebaran, the "eye" of Taurus the bull, is about the same distance to the right of Venus, with Mars directly above Aldebaran. Since Mars and Aldebaran are both orange, and they are about the same brightness, they form an eye-catching pair. Together, the Pleiades, Mars, Aldebaran, and Venus form a mirror-reversed letter "L" in the east.
To the left of this group (to the Northeast) and slightly above it you will see what looks like a sideways letter "W". This is part of the constellation of Cassiopeia and is what's called an asterism. The difference between an asterism and a constellation is that an asterism isn’t one of the 88 “official” constellations. Rather, it’s just a recognizable group of stars that forms some picture.
The “Big W” in Cassiopeia includes five of the constellation’s brightest stars. To
name them in the morning sky when it's sideways like this, start at the top with Beta (β) Cas, then head down to Alpha (α), Gamma (γ), Delta (δ) and finish up with Epsilon (ε) Cassiopeiae. But it’s only a W about half of a 24-hour period. The other half, it’s just as fair to call it the “Big M.” Cassiopeia is one of the few CIRCUMPOLAR CONSTELLATIONS for the northern hemisphere, meaning it truly never rises nor sets below any horizon from as far south as 30 degrees north. Rather, it appears - if you were able to observe it throughout its 24-hour spin - to describe a complete circle centered on the North Star, Polaris. (Source) The Big Dipper (another asterism) does the same thing. Cassiopeia, by the way, is smack dab in the middle of the Milky Way. The constellation is a Queen in her chair who got herself in trouble with Poseidon boasting she was more beautiful than the Nereids (sea nymphs) and that leads to an entertaining story. Google it. ;)Looking to the southwest you will see Jupiter in the dawn sky. Of the planets only Venus, and on the rare occasion Mars, gets brighter than Jupiter. Rising earlier in the night each month, by late July it is rising in the evening sky a couple of hours after sunset and will be visible all night, moving across the sky from east to west.
Do you have a pair of binoculars? If so, get them out and take a look at Jupiter. It's big enough that you should be able to see that it's a globe even without a telescope, and that's pretty cool! If it's good and dark where you are you might even be able to see up to 4 "stars" in a line next to it. These "stars" are its 4 largest moons (Io, Europa, Ganymede, Callisto) which were discovered by Galileo in 1610, nearly 400 years ago!
And of course in the northern sky you can always see the Big Dipper and Little Dipper (two more asterisms), rotating around the North Star as the night progresses. There's always something comforting about the Big Dipper; maybe it's its steadiness and easy recognizability. To find the North Star, which is not a big bright star as one might imagine, first find the Big Dipper, locate the two stars that form the outer edge of the Big Dipper's cup and draw an imaginary line straight through those two stars toward the center star of the "Big W" (the Big Dipper and the W are always opposite each other). About midway between those two asterisms is the North Star, which is the brightest star in the Little Dipper, at the end of its handle.As the year progresses, Mars will continue to pull farther away from the Sun and be visible for more of the night. By late in the year, it will be in view for more than half of the night, which means it will be higher in the sky at dawn, and will outshine all except Venus and Jupiter and one star.
On July 27 Mars and Aldebaran will line up very close together again, well up in the east at dawn with Mars slightly higher than Aldebaran.
Venus switches back and forth from only being observable in the morning to only being observable in the evening. Next year, Venus will be back in the evening sky.
A historical moment:
On July 20 in 1969, at 4:18 p.m. EDT, the first men landed on the Moon. You can follow a complete, 40-years-later realtime replay of all mission-control communications with Apollo 11 throughout the entire mission. NASA is also providing historical information about Apollo 11 and has set up a 40th anniversary website.
If you want to learn about how to recognize constellations, etc., a good source for you is About.com's space/astronomy pages.
And don't forget as you're heading home at night or stepping outside with a cup of coffee in the wee hours, maybe getting reading for a fishing trip, to look up!
Sources:
Sky and Telescope
Space/Astronomy at About.com
