We know the Voyager spacecraft has left the solar system. What no one can really say is when. Boundaries in space are entirely human vanities, there is no 'Now leaving the Local System' sign after Pluto.

Well, it's all so unsettled that two percent of astronomers even decided Pluto wasn't even a planet. 

But no matter how we define a planet, the solar system has a new most-distant member, according to new work from Carnegie's Scott Sheppard and Chadwick Trujillo of the Gemini Observatory. In Nature, they report the discovery of the distant dwarf planet 2012 VP113 beyond the known 'edge' of the Solar System.

Astronomers have announced the surprise discovery that the asteroid Chariklo is surrounded by two dense and narrow rings, by far the smallest object to have rings. 

The rings of Saturn are, of course, one of the most spectacular sights in the sky. Despite many careful searches, no rings had been found around smaller objects orbiting the Sun in the Solar System. Now observations of the distant minor planet (10199) Chariklo as it passed in front of a star have shown that it is surrounded by two fine rings. Minor planet? Yes, the IAU which demoted Pluto has generally made a mess of things and so asteroid and minor planet are interchangeable in common parlance.

A decades old space mystery has been solved by an international team of astronomers who investigated hot, young, white dwarfs — the super-dense remains of Sun-like stars that ran out of fuel and collapsed to about the size of the Earth. 

It has been known that many hot white dwarfs atmospheres, essentially of pure hydrogen or pure helium, are contaminated by other elements – like carbon, silicon and iron. What was not known, however, was the origins of these elements, known in astronomical terms as metals.

How many ways can you describe an object?

If you look at an apple, you might estimate its weight, shape and color but beyond that it is difficult. We are unable to describe the chemical composition of its flesh.

Something similar also applies to astronomical objects, like neutron stars. We might describe their size, or as the thing in which Thor's hammer, Mjolnir, was forged, but describing neutron stars at the nuclear physics level is extremely complex, and several complicated equations of state have been proposed. However, to date there is no agreement as to which is the correct (or the best) one.

An international team of astronomers, led by Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil), has used telescopes at seven locations in South America, including the 1.54-meter Danish and TRAPPIST telescopes at ESO’s La Silla Observatory in Chile, to make a surprise discovery in the outer Solar System.

A research team has detected water vapor in the atmosphere of tau Boo b, a "hot Jupiter" planet outside our solar system. 

The team applied a Doppler technique to the infrared to directly detect tau Boo b and demonstrate the presence of water in its atmosphere. Tau Boo b orbits the nearby star tau Boötis, 51 light years away. Unlike our Jupiter, which is fairly cold and has an orbital period of about 12 years, the hot Jupiter tau Boo b orbits its star every 3.3 days and is heated to extreme temperatures by its proximity to the star. Under these conditions, water will exist as a high temperature steam.

2 million images collected by NASA's orbiting Spitzer Space Telescope, which went into space in 2003, have been stitched together to create a 360 degree portrait of the Milky Way.

The world's leading particle collider experiments, Fermilab's Tevatron and CERN's Large Hadron Collider (LHC), have joined forces. Scientists from the four experiments involved — ATLAS, CDF, CMS and DZero — announced their joint findings on the mass of the top quark today at the Rencontres de Moriond international physics conference in Italy. 

They pooled their data analysis power to arrive at a new world's best value for the mass of the top quark of 173.34 plus/minus 0.76 GeV/c2.

Scientists have discovered a new, persistent structure in one of two radiation belts surrounding Earth  - high-energy electrons in the inner Van Allen radiation belt display a persistent pattern that resembles slanted zebra stripes.

Surprisingly, this structure made of high-energy electrons is produced by the slow rotation of Earth, previously considered incapable of affecting the motion of radiation belt particles, which have velocities approaching the speed of light.

New evidence gathered by NASA's MESSENGER spacecraft at Mercury solves an apparent enigma about Mercury's evolution. 

The data indicate the tiny planet closest to the sun, only slightly larger than earth's moon, has shrunk up to 7 kilometers in radius over the past 4 billion years, much more than earlier estimates. Older images of surface features indicated that, despite cooling over its lifetime, the rocky planet had barely shrunk at all. But modeling of the planet's formation and aging could not explain that finding.