Every day since June 16, 1995, Professor Robert Nemiroff at Michigan Technological University and NASA scientist Jerry Bonnell have posted an image on the Web as their Astronomy Picture of the Day. Click through 10 of Nemiroff's favorites in this slideshow, which pays tribute to an event called 100 Hours of Astronomy. Astronomers around the world are encouraging people to peer at the skies just as Galileo did 400 years ago – and just as the stargazers in this image are doing.
All over the world, people gaze out at the horizon as the moon rises – and perhaps ponder distant worlds. This famous shot, made as Apollo 8 astronauts rounded the far side of the moon in 1968, pulls a switcheroo. "I think maybe people put their existence in some kind of context," Nemiroff says of the image's impact. "We are all on the same big blue marble."
Astronaut Harrison Schmitt walks alongside a moon buggy during the final lunar landing mission of the Apollo program in December 1972. While there are many historic images from the surface of the moon, Nemiroff says, "I like this one. It shows the moon surface, it shows some desolation, it shows the magnificence. And there's a human for scale, so people can identify." Schmitt and Apollo 17 commander Gene Cernan, who took this picture, were the last astronauts to walk on the moon.
Ah, the sun ... or should that be "AHHH, the sun!!" Nemiroff says our star is the most well-known object in the sky, but this image casts it in a different – and slightly terrifying – light. The view from the orbiting Solar and Heliospheric Observatory, or SOHO, shows the sun as a complex, busy sphere. On the lower left is a large flare reaching out like a giant claw. "The earth could easily fit in that claw," Nemiroff says.
Some people travel thousands of miles to see a total eclipse of the sun – when the full moon passes between the sun and Earth, temporarily blotting the sun from the sky. Travelers on the Mir space station captured this rare image of the spectacle as seen from space on Aug. 11, 1999. For Nemiroff, it's a fantastic educational tool: "People suddenly understand that when the moon covers the sun, there's a shadow on the earth – and if you stand in the shadow, that's where you see the total eclipse of the sun," he says.
This iconic image of the pillars of creation in the Eagle Nebula was captured by the Hubble Space Telescope in 1995. The giant pillars are light-years-long columns of dense gas and dust that condense to form stars. "You can actually look into the pillars and see things," Nemiroff says. "The end of the topmost pillar is being boiled away by stars." The nebula is about 7,000 light-years from earth.
An entirely different take on the famed pillars of creation was gained with this wide-field image of the Eagle Nebula made with the 0.9-meter telescope on Arizona's Kitt Peak. "It puts the other image that is well-known – that is in the very center – puts it in a bigger perspective," Nemiroff says. "And you can see a star nebula as an open cluster of stars forming there – the pink."
The Andromeda Galaxy is our Milky Way's closest spiral galactic neighbor, located about 2 million light-years away. Though visible as a faint smudge with the naked eye, the galaxy comes to life when viewed with basic observing equipment. Amateur astronomer Robert Gendler combined 40 gray-scale frames of the galaxy to create this beautiful image. Color came from previous images. Access to these tools, Nemiroff notes, allows amateurs to contribute scientifically valuable images to astronomy.
Images gathered by a swarm of Defense Department satellites were stitched together to make this snapshot of the earth at night. "It is interesting to people because people like to find where they are [and] it shows where people are on planet Earth," Nemiroff says. Urban legend, he adds, erroneously attributes the creation of the popular image to a single picture taken from the space shuttle. The thoughtful observer will realize that night is everywhere in the image, which never happens.
On April 12, 1981, the space shuttle Columbia blasted off from NASA's Kennedy Space Center in Florida, launching a new era of human spaceflight. This photo was taken on the night before the historic launch. Nemiroff says it's a "historically fascinating, visually interesting image." The two-day checkout flight ended with a safe, airplane-style landing at Edwards Air Force Base in California. The shuttle program continues, primarily helping NASA complete the international space station.
Nemiroff and APOD colleague Jerry Bonnell like to have fun with their Web site every now and again, and usually post something a bit tongue-in-cheek on April Fools' Day. One of Nemiroff's recent favorites shows a robot, named Dextre, apparently attacking the international space station. "You see the common earth, you see the space station, you see complex things on the space station, but then there's this strange robot thing," he says. Though truly a robot, Dextre is friendly, helping astronauts with building and repairs.