Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 November 17 
Posted on 11/17/2002 12:03:53 AM PST by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 November 17
Explanation: Is Leo leaking? Leo, the famous sky constellation visible on the left of the above all-sky photograph, appears to be the source of all the meteors seen in last year's Leonids Meteor Shower. That Leonids point back to Leo is not a surprise - it is the reason that this November meteor shower is called the Leonids. Sand-sized debris expelled from Comet Tempel-Tuttle follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation Leo. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Leo. Over 100 bright meteors can be seen in the above half-hour exposure. The intensity of the Leonid Meteor Shower in 2002 is uncertain but may approach one per second for some locations on November 18 and 19.
Have you noticed that the Leonid Meteor Shower has been a subject of discussion at the APOD 5 times in 2 weeks?
This is a not-to-be-missed event. Check back in the APODs to find a webcam if your weather doesn't cooperate.
So how do we see sand-grain-sized particles burning up in the atmosphere miles up? Speed has a lot to do with it. Leonid meteors are some of the fastest; they can enter our atmosphere at speeds of 160,000 miles an hour. At these speeds, the light emitted from collision with air molecules is quite striking. Color can range from red to white to blue and even green. Watch out for larger meteors - fireballs are a sight to see!
Got camera? Some meteors leave a trail of glowing gas for several minutes!
See the Leonids 2001 Meteor Gallery for amazing photos!
If you have meteor-related questions, this site might have the answers:
American Association of Amateur Astronomers: About Meteors and Meteor Showers. Enjoy!
That would be of an object travelling in the opposite direction than earth. Earth's speed plus the asteroid's speed plus gravitational effects = 160,000 mph maximum.
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