Astronomy Picture Of the Day (APOD)The X-ray Sources of M31
Just like our own Milky Way Galaxy, the nearest major galaxy M31 has many star systems spewing high energy radiation. High energy X-radiation is visible to certain satellites in Earth orbit such as ROSAT - which took the above picture.
LMC X-1: A Black Hole Candidate
The strongest source of X-rays in the Large Magellanic Cloud originates from an unusually energetic binary star system. This strong source, dubbed LMC X-1, is thought to be a normal and compact star orbiting each other. Gas stripped of the normal star falls onto the compact star, heats up, and emits X-rays.
NGC 4361: Galaxy Shaped Planetary Nebula
Glowing in the red light emitted by hydrogen atoms, the planetary nebula NGC 4361 is pictured above. The nebula itself is formed by the outer layers of gas shrugged off by the central star visible in the image.
NGC 6240: When Galaxies Collide
Sometimes even galaxies can suffer a fatal attraction. Here gravity causes two galaxies to collide in a spectacular display of energetic gas, dust, and light. When galaxies collide it is rare that any stars in the galaxies themselves collide, or that any change will be seen in a human lifetime.
Nova Cygni 1992
In 1992 a tremendous explosion occurred in the constellation of Cygnus. Dubbed Nova Cygni 1992, this event most probably occurred in an accretion disk binary system. Astronomers hypothesize that this system's white dwarf had so much gas dumped onto it's surface that conditions became ripe for nuclear fusion.
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 compact object - either a white dwarf star, a neutron star, or black hole.
During the 1968 Christmas season Frank Borman, James Lovell, and William Anders flew the Apollo 8 command module From the Earth to the Moon and back (launched Dec. 21, achieved 10 lunar orbits, landed Dec. 27).
Uranus' Moon Miranda
NASA's robot spacecraft Voyager 2 passed the planet Uranus and its moons in 1986. While the cloud tops of Uranus proved to be rather featureless, the surface of Miranda, the innermost of Uranus' large moons, showed several interesting features.
Prometheus, Pandora and Saturn's F Ring
The third and fourth innermost moons of Saturn were unexpectedly discovered to be gravitational "shepards." The inner moon Prometheus and the outer moon Pandora use their gravitational attraction to define Saturn's outermost ring.
Summer at the South Pole
December 22 marks the Winter Solstice - the beginning of winter in the Earth's northern hemisphere, and the first day of summer in the south! This view of Earth's southern hemisphere near the beginning of its summer was created using images from the Galileo spacecraft taken during the December 1990 flyby.