Saturday, July 28, 2012

Tonight's Sky: Astronomical Events August 2012

Backyard stargazers get a monthly guide to the northern hemisphere's skywatching events with "Tonight's Sky." In August, we have two full moons in one month, a great look at the Ring Nebula, and the Perseid meteor shower.

"Tonight's Sky" is produced by HubbleSite.org, online home of the Hubble Space Telescope. This is a recurring show, and you can find more episodes — and other astronomy videos — at HubbleSite.org.

Evening Planets
In the evening twilight, Saturn and Mars form a lovely trio with the bright star Spica as they dip toward the western horizon. Aim a telescope at the planets to reveal their stunning features.

Morning Planets
During the middle of the month, three planets grace the morning sky just before sunrise. Mercury hovers just above the eastern horizon. Gaze upward to see Venus and Jupiter. While Mercury can be a challenge to find, Venus and Jupiter will be easy to spot throughout the month.

Constellations and Deep-Sky Objects
Stargazing on a hot August night reveals a multitude of wonders in the summer night sky.

Lyra, the Small Harp, lies high in the late evening sky. Its main star is the great Vega, one of the brightest in the sky.

Look for Lyra by locating Vega and then the parallelogram of stars nearby.

Epsilon Lyrae, the bright star near Vega, is actually a wonderful quadruple-star system, known as the Double-Double. 

In the parallelogram of Lyra lies the dramatic Ring Nebula. It is an expanding shell of glowing gas expelled by the dying star at its center.

The great constellation Cygnus, the Swan, flies high through the August night.

Using bright Vega as your guide star, look for the cross just to the east. Cygnus is also known as the Northern Cross.

Albireo, at the head of the Swan, is a showpiece for small telescopes. This spectacular pair of stars features contrasting colors of sapphire and golden topaz.

Deneb, the Swan’s tail, is a supergiant star. If Deneb replaced the Sun in the center of our solar system, it would engulf Mercury and Venus.

On a clear night, hazy patches of nebulae can be seen by casually panning across the Cygnus area with binoculars.

The most prominent is the North America Nebula, an area of gas and dust illuminated by the nearby, brilliant star Deneb.

Cygnus also hosts several clusters of stars. The easiest to find are M29 and M39.

M29 is found near the center of the Northern Cross. When viewed in a small telescope, it resembles a small square.

Best seen in binoculars, M39 is a loosely bound cluster of about 30 stars, just to the north of Deneb.

Just south of Cygnus lies the small constellation Vulpecula, the Little Fox, first charted by Polish astronomer Johannes Hevelius in the 17th century.

Vulpecula hosts the Dumbbell Nebula, which can be seen as a faint smudge in binoculars. A small telescope reveals its double-lobed shape.

Aquila, the Eagle, was known to the ancient Greeks as the great bird of Zeus. 

Altair, the brightest star in Aquila, is only 16 light-years from Earth.

The bright stars of the summer night sky, Vega, Altair, and Deneb, make up the Summer Triangle.

Events
The Perseid meteor shower is an always-anticipated feature of the August night  sky. Look for meteors during the early morning hours of August 12th and 13th. These streaks of light are tiny bits of a comet burning up as they enter Earth’s atmosphere. The cometary debris trail, through which Earth passes once a year, was left behind by Comet Swift-Tuttle during its many visits to the inner solar system.

Visit Tonight's Sky on HubbleSite.

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