As the sky begins to darken, you might be tempted to make a wish on the first star you see.
"Star light, star bright,
First star I see tonight . . ."
Go ahead and make that wish. Just be sure that the star you wish upon is really a star.
Even with the western sky bathed in the glow of twilight, one of the first stars will appear be high in the southwest. This bright star really stands out against the background and almost screams for your attention. There's only one problem: it's not a star. It's a planet.
A good rule of thumb for telling the difference between the stars and the planets is to remember that usually, stars twinkle and planets don't. If you see a steady star-like object that's not twinkling and not moving, it's probably a planet. In this case, you are looking at Jupiter.
Mighty Jupiter, the largest planet in our solar system, is currently moving eastward through the dimmer stars of Virgo the maiden. The only bright star in the immediate vicinity to compare it to is blue-white Spica. However, Spica may not emerge from the twilight until 30 minutes to an hour later. If the weather is clear on the evening of June 15, Jupiter will appear near the first quarter Moon.
If you have a clear western horizon, try looking for Venus about 45 minutes after sunset - before the sky really gets dark This 'evening star' lies nine degrees above the horizon. Conveniently, your fist held at arm's length measures about ten degrees wide, from knuckle to knuckle. The hunt for this challenge object will be easier if you scan that part of the sky with binoculars. On the evenings of June 24-26, Saturn and Mercury will pass close by Venus with all three visible in your binoculars' field of view.
Brilliant Vega, rising in the east, will try to woo you away from Jupiter. Vega is fifth on the list of bright stars we see in the night sky, and it marks one corner of an easily locatable star pattern called the Summer Triangle - where each corner star is part of a different constellation.
While Vega shines brightly, it is part of a relatively dim constellation called Lyra - said to look like a harp or lyre. Unfortunately, the person who drew this picture must've been a liar because it looks less like a musical instrument and more like a German beer stein with the lid open.
The dimmest of the three stars in the triangle is called Deneb and marks the tail of Cygnus the swan. The nearest bright star that lies inside the triangle represents the body of the swan. Continue the line from the tail through the body, and you can trace out the long neck of the swan to the head star Albireo. The swan's wings are spread wide as he glides along the Milky Way.
If this is a bit too complex, you can simplify the image by looking for the Northern Cross. The line from head to tail of the swan is the pole of the cross, and a line drawn from one wingtip to the other forms the crossbar.
Right on the money is where Deep Impact has to be to place a 1-meter-long (39-inch) impactor spacecraft in the path of a comet about as big as the island of Manhattan that is bearing down on it at 37,100 kilometers per hour (6.3 miles per second). At the same time, from the safe distance of 500 kilometers (310 miles), a flyby spacecraft will be monitoring the event. This all occurs in the wee hours of July 4 - at 12:52 am Central time - at a distance of 133.6-million kilometers (83-million miles) from Earth.
"The Hubble Space Telescope is assured a ringside seat," says Principal Investigator Dr. Michael A'Hearn of the University of Maryland, College Park. "Their observations, along with space telescopes Chandra and Spitzer and numerous ground-based observatories, will provide us with the most scientific bang for our buck with Deep Impact."
The crater produced by the impact could range from the width of a large house up to the size of a football stadium, and from 2 to 14 stories deep. Ice and dust debris will be ejected from the crater, revealing the material beneath.
For more information about Deep Impact, visit deepimpact.jpl.nasa.gov, and watch NASA TV that night, as the dramatic events unfold.
