An international team of astronomers has identified a candidate for the smallest-known black hole using data from NASA's Rossi X-ray Timing Explorer (RXTE).

The evidence comes from a specific type of X-ray pattern, nicknamed a "heartbeat" because of its resemblance to an electrocardiogram. The pattern until now has been recorded in only one other black hole system.

Hubble's Wide Field Camera 3 has captured this image of a giant cloud of hydrogen gas illuminated by a bright young star.

The image shows how violent the end stages of the star-formation process can be, with the young object shaking up its stellar nursery.

Like wine in a glass, vast clouds of hot gas are sloshing back and forth in Abell 2052, a galaxy cluster located about 480 million light years from Earth.

X-ray data (blue) from Chandra shows the hot gas in this dynamic system, and optical data (gold) from the Very Large Telescope shows the galaxies. The hot, X-ray bright gas has an average temperature of about 30 million degrees.

In early November 1572, observers on Earth witnessed the appearance of a "new star" in the constellation Cassiopeia, an event now recognized as the brightest naked-eye supernova in more than 400 years.

It's often called "Tycho's supernova" after the great Danish astronomer Tycho Brahe, who gained renown for his extensive study of the object. Now, years of data collected by NASA's Fermi Gamma-Ray Space Telescope reveal that the shattered star's remains shine in high-energy gamma rays.

The compact nature of globular clusters is a double-edged sword. On the one hand, having so many stars of a similar age in one bundle gives astronomers insights into the chemical makeup of our galaxy in its early history.

But, at the same time, the high density of stars in the cores of globulars also makes it difficult for astronomers to resolve individual stars.

About 3,700 years ago people on Earth would have seen a brand-new bright star in the sky.

As it slowly dimmed out of sight, it was eventually forgotten, until modern astronomers found its remains -- called Puppis A. Seen as a red dusty cloud in this image from WISE, Puppis A is the remnant of a supernova explosion.

Opportunity has found bright veins of a mineral, apparently gypsum, deposited by water.

Analysis of the vein will help improve understanding of the history of wet environments on Mars.

ESA's Gaia star-mapper has passed a critical test ahead of its launch in 2013: the spacecraft's sunshield has been deployed for the first time.

Gaia's sunshield is an essential component of the mission. It keeps Gaia in shadow, maintaining the scientific instruments at a constant temperature of around -110°C.

No asteroid or rocky planet looks quite like the asteroid Vesta, which Dawn has been orbiting since July 2011; countless craters, furrows and slopes define the landscape of this celestial body.

The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) has produced a 3D film from the imagery recorded by the cameras on board the spacecraft. This film makes it possible, for the first time ever, for this asteroid to appear close enough to reach out and touch.

Vesta appears in a splendid rainbow-colored palette in new images obtained by Dawn. The colors, assigned by scientists to show different rock or mineral types, reveal Vesta to be a world of many varied, well-separated layers and ingredients.

Vesta is unique among asteroids visited by spacecraft to date in having such wide variation, supporting the notion that it is transitional between the terrestrial planets -- like Earth, Mercury, Mars and Venus -- and its asteroid siblings.

Voyager 1 has entered a new region between our solar system and interstellar space. Data obtained from the spacecraft over the last year reveal this new region to be a kind of cosmic purgatory.

In it, the wind of charged particles streaming out from our sun has calmed, our solar system's magnetic field is piled up, and higher-energy particles from inside our solar system appear to be leaking out into interstellar space.

NASA's Kepler mission has confirmed its first planet in the "habitable zone," the region where liquid water could exist on a planet's surface.

Kepler also has discovered more than 1,000 new planet candidates, nearly doubling its previously known count. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.

Three thousand light-years from Earth lies the strange protoplanetary nebula IRAS 09371+1212, nicknamed the Frosty Leo Nebula.

Despite their name, protoplanetary nebulae have nothing to do with planets: they are formed from material shed from their aging central star. The Frosty Leo Nebula has acquired its curious name as it has been found to be rich in water in the form of ice grains, and because it lies in the constellation of Leo.

The New Horizons mission reached a special milestone on Friday, December 2, 2011 on its way to reconnoiter the Pluto system, coming closer to Pluto than any other spacecraft.

It's taken New Horizons 2,143 days of high-speed flight – covering more than a million kilometers per day for nearly six years--to break the closest-approach mark set by NASA's Voyager 1 in January 1986. Pluto wasn't on Voyager's mission path, but after making historic flybys of Jupiter in 1979 and Saturn in 1980, the intrepid probe came about 983 million miles (1.58 billion kilometers) from Pluto as it raced to the solar system's outskirts.

A research team led by Steve Howell, NASA Ames Research Center, has shown that one of the brightest stars in the Kepler star field has a planet with a radius only 1.6 that of the earth's radius and a mass no greater that 10 earth masses, circling its parent star with a 2.8 day period.

With such a short period, and such a bright star, the team of over 65 astronomers (that included David Silva, Ken Mighell and Mark Everett of NOAO) needed multiple telescopes on the ground to support and confirm their Kepler observations. These included the 4 meter Mayall telescope and the WIYN telescope at Kitt Peak National Observatory.