Browse NASA Astronomy Picture of the Day archive by date and media: Archive Discoveries
Browse the NASA APOD archive without needing the exact date first. Filter by media type and keep moving deeper into older images and videos.
Small Star
A dim double star system cataloged as Gliese 623 lies 25 light-years from Earth, in the constellation of Hercules . The individual stars of this binary system were distinguished…
Mercury And The Sun
Just days before the peak of the Leonid meteor shower , skywatchers were offered another astronomical treat as planet Mercury crossed the face of the Sun on November 15. Viewed…
A Sirius Leonid Meteor
In the sky or on the web, did you watch this year's Leonid meteor shower? If you did, meteors flashing through the night sky should be a familiar sight. Recorded last year during…
A Leonid Meteor Explodes
Tonight, a lucky few may see a meteor explode. Over the next 36 hours the Earth will pass unusually close to debris expelled from Comet Tempel-Tuttle , causing many sand-sized…
A RADARSAT Map of Antarctica
It's not easy to make a map of Antarctica . Earth's southern most continent is so cold and inhospitable that much of it remains unexplored . From space , though, it is possible to…
In the Shade of a Historic Planet
For the first time, astronomers have recovered independent evidence that distant planetary systems exist. Last Friday, a team led by G. W. Henry ( Tenn. State ) and G. Marcy ( UC…
M31: The Andromeda Galaxy
Andromeda is the nearest major galaxy to our own Milky Way Galaxy . Our Galaxy is thought to look much like Andromeda . Together these two galaxies dominate the Local Group of…
Tempel-Tuttle: The Leonid Comet
Star trails streak this composite time exposure of Comet Tempel-Tuttle recorded by T. Puckett on January 26, 1998. Then passing through the inner solar system on its 33 year orbit…
1998 Leonid Fireball
Will this be the year ? Last year's Leonid meteor shower did not produce the meteor storm many had hoped for. Still, it put on a dazzling show with many bright fireball meteors .…
Mercury And The Moon
Mercury is the closest planet to the Sun and never moves far from our parent star in Earth's sky . Racing around its tight orbit, this well-done world is a little over 1/3 the…
The Belt of Venus
Although you've surely seen it, you might not have noticed it. During a cloudless twilight , just before sunrise or after sunset , part of the atmosphere above the horizon appears…
Spiral Galaxies in Collision
Billions of years from now, only one of these two galaxies will remain. Until then, spiral galaxies NGC 2207 and IC 2163 will slowly pull each other apart, creating tides of…
Lunation
Our Moon's appearance changes nightly. This slow-loading time-lapse sequence shows what our Moon looks like during a lunation , a complete lunar cycle. As the Moon orbits the…
The Heart Of NGC 4261
Who knows what evil lurks in the hearts of galaxies? The Hubble knows. This Hubble Space Telescope picture of the center of the nearby elliptical galaxy NGC 4261 tells one…
X-ray Transit of Mercury
This sequence of false color X-ray images captures a rare event - the passage or transit of planet Mercury in front of the Sun. Mercury's small disk is silhouetted against the…
The Shadow Of Phobos
Hurtling through space above the Red Planet , potato-shaped Phobos completes an orbit of Mars in less than eight hours. In fact, since its orbital period is shorter than the…
Gamma-Ray Bursting
Using graphics and data from NASA's Compton Gamma Ray Observatory , this animation illustrates one of the most exciting mysteries of modern astrophysics, gamma-ray bursts .…
M32: Blue Stars in an Elliptical Galaxy
Elliptical galaxies are known for their old, red stars. But is this old elliptical up to new tricks? In recent years, the centers of elliptical galaxies have been found to emit…
Aurora Through a Moonlit Sky
A night sky can glow in fascinating ways. Through a clearing in the woods, the pictured sky above Alaska shines by reflected light from a nearby city, by the brightness of the…
The Rotten Egg Planetary Nebula
Not all evolving stars eject gas clouds that look like people. OH231.8+4.2 was a star much like our Sun that ran out of nuclear fuel to fuse in its core. It has therefore entered…
The Cat's Eye Nebula
Three thousand light-years away, a dying star throws off shells of glowing gas. This image from the Hubble Space Telescope reveals The Cat's Eye Nebula to be one of the most…
Mars Rocks, Sojourner Rolls
This sharp color image featuring Mars rock Yogi and the rolling Sojourner robot shows off Yogi's two-toned surface. Yogi appears to be leaning into the prevailing winds causing…
The USNO Millennium Time Ball
In the nineteenth century , dropping a time ball from a prominent location was a practical way of communicating the time to the surrounding country side and ships at sea .…
X-Ray Jet From Centaurus A
Spanning over 25,000 light-years, comparable to the distance from the Sun to the center of our own Milky Way galaxy, a cosmic jet seen in X-rays blasts from the center of…
Viewing discoveries from 20 November 1999 through 28 October 1999.