While analyzing NASA Hubble Space Telescope images of the Sagittarius dwarf irregular galaxy (SagDIG), an international team of astronomers led by Simone Marchi, Yazan Momany, and Luigi Bedin discovered 13 sucessive faint trails left by a tiny asteroid. The trails are seen as a series of reddish arcs on the right in this August 2003 Advanced Camera for Surveys image.

At first glance, Jupiter looks like it has a mild case of the measles. Five spots - one colored white, one blue, and three black - are scattered across the upper half of the planet. Closer inspection by NASA's Hubble Space Telescope reveals that these spots are actually a rare alignment of three of Jupiter's largest moons - Io, Ganymede, and Callisto - across the planet's face. In this image, the telltale signatures of this alignment are the shadows [the three black circles] cast by the moons. Io's shadow is located just above center and to the left; Ganymede's on the planet's left edge; and... Read more

This image of comet C/2001 Q4 (NEAT) was taken at the WIYN 0.9-meter telescope at Kitt Peak National Observatory near Tucson, Ariz., on May 7, 2004.

The image was captured with the Mosaic I camera, which has a one-square degree field of view, or about five times the size of the Moon. Even with this large field, only the comet's coma and the inner portion of its tail are visible. A small star cluster (C0736-105, or Melotte 72) is visible in the lower right of the image, between the head of the comet and the bright red star in the lower-right corner.

As Saturn grows closer through the eyes of the Cassini spacecraft, which is hurtling toward a rendezvous with the ringed world on June 30 (July 1, Universal Time), both Cassini and the Earth-orbiting Hubble Space Telescope snapped spectacular pictures of the planet and its magnificent rings. Cassini is approaching Saturn at an oblique angle to the Sun and from below the ecliptic plane. Cassini has a very diferent view of Saturn than Hubble's Earth-centered view. For the first time, astronomers can compare views of equal-sharpness of Saturn from two very different perspectives.

Resembling a diamond-encrusted bracelet, a ring of brilliant blue star clusters wraps around the yellowish nucleus of what was once a normal spiral galaxy in this new image from NASA's Hubble Space Telescope (HST). This image is being released to commemorate the 14th anniversary of Hubble's launch on April 24, 1990 and its deployment from the space shuttle Discovery on April 25, 1990. The galaxy, cataloged as AM 0644-741, is a member of the class of so-called "ring galaxies." It lies 300 million light-years away in the direction of the southern constellation Volans.

Astronomers poring over 35 NASA Hubble Space Telescope images of the solar system's farthest known object, unofficially named Sedna, are surprised that the object does not appear to have a companion moon of any substantial size. This unexpected result might offer new clues to the origin and evolution of objects on the far edge of the solar system.

At a distance of over 8 billion miles, Sedna is so far away it is reduced to one picture element (pixel) in the image [at lower right] taken in high-resolution mode with Hubble's Advanced Camera for Surveys. This image sets an upper limit on Sedna's size of 1,000 miles in diameter.

Atmospheric features on Uranus and Neptune are revealed in images taken with the Space Telescope Imaging Spectrograph and the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope. A wider view of Uranus, taken with the Advanced Camera for Surveys, reveals the planet's faint rings and several of its satellites. The observations were taken in August 2003.

Astronomers have discovered two of the smallest moons yet found around Uranus. The new moons, uncovered by NASA's Hubble Space Telescope, are about 8 to 10 miles across (12 to 16 km) - about the size of San Francisco. The two moons are so faint they eluded detection by the Voyager 2 spacecraft, which discovered 10 small satellites when it flew by the gas giant planet in 1986. The newly detected moons are orbiting even closer to the planet than the five major Uranian satellites, which are several hundred miles wide. The two new satellites are the first inner moons of Uranus discovered from an... Read more

This is a series of images of Saturn, as seen at many different wavelengths, when the planet's rings were at their maximum tilt of 27 degrees toward Earth. Saturn experiences seasonal tilts away from and toward the Sun, much the same way Earth does. This happens over the course of its 29.5-year orbit. This means that approximately every 30 years, Earth observers can catch their best glimpse of Saturn's South Pole and the southern side of the planet's rings. Between March and April 2003, researchers took full advantage to study the gas giant at maximum tilt. They used NASA's Hubble Space Telescope to... Read more

Astronomers using NASA's Hubble Space Telescope have discovered three of the faintest and smallest objects ever detected beyond Neptune. Each object is a lump of ice and rock - roughly the size of Philadelphia - orbiting beyond Neptune and Pluto, where the icy bodies may have dwelled since the formation of the solar system 4.5 billion years ago. They reside in a ring-shaped region called the Kuiper Belt, which houses a swarm of icy rocks that are leftover building blocks, or "planetesimals," from the solar system's creation. The biggest surprise of the Hubble search is that so few small Kuiper Belt... Read more