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.
Unusual Aurora During Solar Wind Dropout
On May 10, for some unknown reason, the Solar Wind virtually stopped. Normally our Sun emits a wind of between five and ten energetic particles per cubic centimeter moving outward…
Perigee Moon, Apogee Moon
Tonight, those blessed with clear skies can enjoy a glorious full moon , the last full moon of the “Y1.9K”s. In fact, tonight's moon will be a full-perigee-solstice moon, reaching…
XMM Launched
X-ray astronomy entered a golden age earlier this month with the successful launch of the X-ray Multi-Mirror (XMM) satellite. XMM 's three huge telescope barrels each hold 58…
Lava Fountain on Jupiter's Io
A lava fountain shooting over a kilometer high has been discovered on Jupiter 's moon Io . The robot Galileo spacecraft orbiting Jupiter photographed the volcanic eruption during…
Accretion Disk Binary System
Our Sun is unusual in that it is alone - most stars occur in multiple or binary systems . In a binary system, the higher mass star will evolve faster and will eventually become a…
Irregular Galaxy Sextans A
Grand spiral galaxies often seem to get all the glory. Their newly formed, bright, blue star clusters found along beautiful, symmetric spiral arms are guaranteed to attract…
Hot Gas In Hydra A
The Hydra A galaxy cluster is really big. In fact, such clusters of galaxies are the largest gravitationally bound objects in the Universe. But individual galaxies are too cool to…
Supernova Remnant In M82
This false-color radio wavelength picture of an expanding stellar debris cloud is the product of one of the largest radio astronomy experiments ever. Combining the output of 20…
A Nova In Aquila
On December 1st , experienced observers patroling the night sky with binoculars noticed what seemed to be a new star in the constellation of Aquila (The Eagle) . It wasn't really…
High Velocity Clouds and the Milky Way
Where are these gas clouds going so quickly? High velocity clouds (HVCs) of gas have been seen for decades but their origins and destinations have remained mysterious. Recent…
A Magellanic Starfield
Stars of many types and colors are visible in this Hubble Space Telescope vista of the Large Magellanic Cloud (LMC). Over 10,000 stars are visible -- the brightest of which are…
NGC 4314: A Nuclear Starburst Ring
Is this old galaxy up to new tricks? The barred spiral galaxy NGC 4314 is billions of years old, but its appearance has changed markedly over just the past few millions of years.…
A Close Encounter Of The Stellar Kind
The unassuming star centered in this sky view will one day be our next door stellar neighbor . The faint 9th magnitude red dwarf , currently 63 light-years away in the…
Spot The Planet
OK, it's a picture of the Sun (duh!), but can you spot the planet ? Of course, most of the spots you've spotted are sunspots, as large or larger than planet Earth itself. The…
X-ray Hot Supernova Remnant in the SMC
The Q-shaped cloud seen in this false-color X-ray image from the orbiting Chandra Observatory is big ... about 40 light-years across. It's hot too, as its X-ray glow is produced…
Moon Struck
Craters produced by ancient impacts on the airless Moon have long been a familiar sight . But now observers have seen elusive optical flashes on the lunar surface - likely the…
The Cat's Paw Nebula
As soon as we find out whose cat did this . . . Nebulae are as famous for being identified with familiar shapes as perhaps cats are for getting into trouble. No cat, though, could…
M83: The Southern Pinwheel Galaxy from VLT
M83 is one of the closest and brightest spiral galaxies on the sky. Visible with binoculars in the constellation of Hydra , majestic spiral arms have prompted its nickname as the…
Rhea: Saturn's Second Largest Moon
Rhea is the second largest moon of Saturn , behind Titan , and the largest without an atmosphere. It is composed mostly of water ice, but has a small rocky core. Rhea 's rotation…
Mars Polar Lander Target Ellipse
South is up in this recent composite color picture of Mars Polar Lander's target region near the Martian South Pole taken on November 28. Imaged by the orbiting Mars Global…
Southern Mars
This topographical map of the southern hemisphere of Mars was generated using data from the Mars Orbiter Laser Altimeter (MOLA). Flying on the Mars Global Surveyor spacecraft,…
1999 Leonid Fireball
Most Leonid meteoroids, the bits of comet debris which produce the annual Leonid meteor shower , range from a mere millimeter to a centimeter in diameter. Yet these cosmic grains…
Landing At The Martian South Pole
The latest invader from Earth, the Mars Polar Lander (MPL) spacecraft, is scheduled to touch down on the Red Planet's surface on Friday, December 3rd . If all goes well the…
Henize 70: A SuperBubble In The LMC
Massive stars -- upwards of tens of times the mass of the Sun - profoundly affect their galactic environment. Churning and mixing the clouds of gas and dust between the stars,…
Viewing discoveries from 23 December 1999 through 30 November 1999.