Astronomy Picture Of the Day (APOD)A Quasar-Galaxy Collision?
In 1963 astronomers were astounded to discover that certain faint, star-like objects have very large redshifts. The large redshifts imply that these objects, now known as quasars (QUASi-stellAR objects), lie near the edge of the observable Universe.
A Glimpse of Titan's Surface
The surface of Titan, Saturn's largest moon, is normally hidden from view by its thick, hazy atmosphere. However, for the first time astronomers have been able to see surface features in images like the one above, made at near-infrared wavelengths with the Hubble Space Telescope.
Asteroid Gaspra's Best Face
Above is the best yet color image of the asteroid Gaspra based on data returned by NASA's Galileo spacecraft. Color variations have been added to high resolution images and enhanced to highlight changes in reflectivity, surface structure and composition. The illuminated portion of the asteroid is about 11 miles long.
Globular Cluster M5
The globular cluster M5, pictured above, contains roughly 100,000 stars. These stars formed together and are gravitationally bound. Stars orbit the center of the cluster, and the cluster orbits the center of our Galaxy. So far, about 160 globular clusters are known to exist in a roughly spherical halo around the Galactic center.
A Storm on Saturn
The white wisp shown on Saturn's cloud tops is actually a major storm system only discovered in December of 1994. Saturn's clouds are composed of primarily hydrogen and helium, but the storm's white clouds are actually ammonia ice crystals that have frozen upon upheaval to the top of the atmosphere.
Galaxy Dwingeloo 1 Emerges
If you look closely at the center of the above photograph, you will see a spiral galaxy behind the field of stars. Named Dwingeloo 1, this nearby galaxy was only discovered recently (1994) because much of its light was obscured by dust, gas and bright stars of our own Milky Way galaxy.
Starburst Galaxy M94
The spiral galaxy M94 is somewhat unusual in that it shows a great ring of bright young stars particularly apparent when observed in ultraviolet light, as shown above. Such a high abundance of these young blue stars may cause a galaxy to be designated a starburst galaxy.
Iapetus: Saturn's Disappearing Moon
Iapetus has an unusual surface, one half of which is very dark, the other half very light. This caused it's discoverer Cassini to remark that Iapetus could only be seen when on one side of Saturn but not the other. The reason for the difference between hemispheres is presently unknown.
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 and orbit are locked together (just like Earth's Moon) so that one side always faces Saturn.
Jupiter, Io, and Ganymede's Shadow
Jupiter, the solar system's largest planet, is seen here next to Io, its closest Galilean moon. On the cloud tops of Jupiter near the left edge of the picture can be seen a dark circular spot which is caused by the shadow of Jupiter's largest moon Ganymede.