Starry Night: Early July

Posted Wednesday, June 29, 2011 in Features

Starry Night: Early July

The Albireo double star system in Cygnus, the Swan.

by Tristan Radtke

Following last month's meteor shower, partial solar eclipse for extreme northern viewers, and total lunar eclipse for a wide swath of the eastern hemisphere and portions of South America, the month of July will bring another partial solar eclipse, this time off the coast of Antarctica, before settling into a quiet pattern until a pair of meteor showers bring a return to the activity that we have grown accustomed to the past few months.

With its warm temperatures, July offers a great chance to catch a glimpse of some of the man-made objects that orbit the planet. Spotting a human-made satellite is not quite as easy as spotting a familiar star or planet, since they behave erratically, changing their paths and directions across the sky frequently. NASA, however, has made spotting some of the many satellites in orbit today much easier with a web-based Java tool to check when the next pass of several will cross over your location, using zip code or international city information. That tool is available here, and lists several satellites including the International Space Station and Hubble Space Telescope, amongst other less familiar ones. Satellites are trickier objects to watch for, but in general you should seek a satellite pass with a high elevation, which is listed in the tool in degrees, since these passes will be the most visible.

**The Stars**

Now that the weather is improving, let's take a more detailed look at the stars of the summer triangle.

High overhead is an almost perfect equilateral triangle of stars, consisting of stars from three different constellations, bisected by the Milky Way.

Deneb is the tail of the constellation Cygnus the Swan, which, with its wings and long neck  outstretched, flies along the milky river of light.  Cygnus is also known as the Northern Cross - in midwinter, it stands upright in the northwest sky.  Deneb is a blue-white supergiant star, one of the most luminous stars in the sky.

At the other end of the constellation lies Albireo, the beak of the swan, which is actually a a beautiful double star system consisting of a large gold star and a smaller star of sapphire blue.

The bright star Altair lies in the constellation Aquila the Eagle, which was a servant of Zeus. Altair means "the flying one," and Altair flies around its axis once every 6 and a half  hours. Astronomers calculate that because of this rapid rotation, it must be twice as wide at its equator as at its poles.

The other star in the triangle is Vega, which is the second brightest star in the northern hemisphere.  Vega lies almost directly overhead this time of year.  In the constellation Lyra, a harp that belonged to Orpheus, Vega is easy to spot, although the constellation is trickier to make out.

** The Planets **

Mercury: As July begins, Mercury remains lost in the glare of the sunrise. By mid-month, it will have moved back out of the Sun's glare to set about thirty minutes after sunset.
Venus: Venus begins July rising around 4:15 a.m. By mid-month, it will have swapped places with Mercury, likely lost in the Sun's rising glare.
Mars: Mars rises at about 3 a.m. at the beginning of July, moving slowly earlier into the morning to rise by 2:45 a.m. by mid July. 
Jupiter: Jupiter continues to move further towards the evening sky in July, starting off the month rising around 1:30 a.m., and reaching the middle of the month rising around 12:30 a.m.
Saturn: Saturn moves the opposite direction from Jupiter in early July, setting just after midnight on July 1 and by 11:30 p.m. by July 15.
Uranus: Uranus begins July rising at 12:15 a.m. By the middle of the month it will rise at about 11:30 p.m.
Neptune: On July 1, Neptune will rise around 11 p.m. By July 15, it will rise around 10 p.m.
Pluto: Pluto rises just about as the Sun sets all month in July.

** The Moon **

The Moon begins July completely new on July 1. By July 8 it will have waxed to first quarter, and it will reach its full phase on July 15.

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