Astronomy Picture Of the Day (APOD)Seven Sisters Versus California
In the lower left corner, dressed in blue, is the Pleiades. Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and most easily visible open clusters on the sky. The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across.
The United States at Night
This is what the United States of America looks like at night! Can you find your favorite US city on this image? Surprisingly, city lights make this task quite possible. The above picture is actually a composite of over 200 images made by satellites orbiting the Earth.
APOD is One Year Old Today
The first Astronomy Picture of the Day (APOD) appeared one year ago today. Pictured above are Robert Nemiroff (left) and Jerry Bonnell (right), engaged in creating the APOD web pages. APOD started over speculative conversations on the ultimate value of the World Wide Web.
Walking in Space
Pictured above is the first american astronaut to walk in space: Edward White. White is seen floating outside the Gemini 4 capsule in 1965. The term "spacewalk" is deceiving since astronauts do not actually walk - they float - usually without their feet touching anything solid. White was connected to the spaceship only by a thick tether.
Floating Free in Space
NASA astronauts can float free in space without any connection to a spaceship. Here astronaut Bruce McCandless maneuvers outside the Space Shuttle Challenger by firing nitrogen gas thrusters on his manned maneuvering unit (MMU). This picture was taken in 1984 and records this first untethered spacewalk. The MMU was developed because astronauts found tethers restrictive.
Vela Supernova Remnant in Optical
About 11,000 years ago a star in the constellation of Vela exploded. This bright supernova may have been visible to the first human farmers. Today the Vela supernova remnant marks the position of a relatively close and recent explosion in our Galaxy. A roughly spherical, expanding shock wave is visible in X-rays.
Vela Supernova Remnant in X-ray
What happens when a star explodes? A huge fireball of hot gas shoots out in all directions. When this gas slams into the existing interstellar medium, it heats up so much it glows in X-rays.
Doomed Star Eta Carinae
Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - make it an excellent candidate for a full blown supernova.
Here's a switch: the above picture is of the Earth taken from a lunar observatory! This false color picture shows how the Earth glows in ultraviolet (UV) light. UV light is so blue humans can't see it.
Blasting Off From the Moon
How did the astronauts get back from the Moon? The Lunar Module that landed two astronauts on the Moon actually came apart. The top part containing the astronauts carried additional rocket fuel which allowed it to blast away, leaving the bottom part on the Moon forever.