Lava Fountain on Jupiter's Io

1999-12-20

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 its close flyby of the moon late last month. The fountain is ...

Accretion Disk Binary System

1999-12-19

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 ...

Irregular Galaxy Sextans A

1999-12-18

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 attention. But small irregular galaxies form stars too, like this lovely, ...

Hot Gas In Hydra A

1999-12-17

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 be recorded in this false-color Chandra Observatory X-ray image ...

Supernova Remnant In M82

1999-12-16

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 radio telescopes scattered around planet Earth, astronomers have ...

A Nova In Aquila

1999-12-15 Till Credner

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 a new star though. A comparison with detailed skymaps revealed the ...

High Velocity Clouds and the Milky Way

1999-12-14

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 measurements have now placed at least one of these clouds in the halo ...

A Magellanic Starfield

1999-12-13

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 giant stars. Were our Sun 170,000 light-years distant and among ...

NGC 4314: A Nuclear Starburst Ring

1999-12-12

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. During that time, a nuclear ring of bright young stars has been ...

A Close Encounter Of The Stellar Kind

1999-12-11

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 constellation Ophiucus, was recently discovered to be approaching our Solar ...