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Hubble to search for worlds beyond Pluto

NASA’S NEW HORIZONS spacecraft, launched in January 2006, is closing in on its primary target, the dwarf planet Pluto. Arrival at the icy outer world is on track for 14 July 2015.

But when it reaches Pluto, New Horizons won’t be able to stop and admire the scenery. By necessity (ie. orbital mechanics and the fact that it doesn’t have a rocket motor to slow itself down) it will go sailing straight past, after having given us our first-ever close up glimpse of what used to be called the ninth planet. (I still do call it the ninth planet. Ed.)

This was always the plan. And the plan also calls for a second stage for the mission – a visit to one or more other icy worlds that orbit the Sun far beyond Pluto.

Artist's impression of the New Horizons spacecraft at Pluto

Artist’s impression of the New Horizons spacecraft at Pluto.

They’re called Kuiper Belt objects (KBOs), as they belong to a family of small, ice bodies that live in that part of the Solar System, called the Kuiper Belt.

The aim is to redirect New Horizons – once it has passed Pluto – onto a course that will take it near one or more of these KBOs.

But even though astronomers have been hunting for candidate KBOs for some years, they’ve yet to find one that is in the right place for New Horizons to visit. Yet there are probably some there that they just can’t see at the moment. So they’ve put out a call for help from the telescope best suited to spot any hidden KBOs – the Hubble Space Telescope.

This week, the Hubble Space Telescope Time Allocation Committee – the body that decides who gets to use the telescope – has recommended it be pressed into service.

The telescope will examine a small region of space to see if it can spot any KBOs. The first step will be doing a pilot study to see if Hubble can indeed spot KBOs in that region and at that distance – 8 billion kilometres from the Sun.

If it finds any, that will give the astronomers enough confidence to push ahead with a deeper, longer search to find the candidate KBOs for New Horizons to visit.

Image courtesy NASA.

Rain of comets in alien star system

Artist's conception of the Eta Corvi star system

This artist's conception illustrates a storm of comets in the Eta Corvi star system. Evidence for this barrage comes from NASA's Spitzer Space Telescope, whose infrared detectors picked up indications that one or more comets was recently torn to shreds after colliding with a rocky body.

NASA’S SPITZER SPACE TELESCOPE has detected signs that icy bodies are raining down in an alien planetary system. The downpour resembles our own Solar System several billion years ago during a period known as the ‘Late Heavy Bombardment,’ when water and other life-forming ingredients may have been brought to Earth.

During this epoch, comets and other frosty objects that were flung inwards from the outer Solar System pummelled the inner planets. The barrage scarred our Moon and produced large amounts of dust.

Now Spitzer has spotted a band of dust around a nearby star called Eta Corvi that strongly matches the contents of an obliterated giant comet. This dust is located close to Eta Corvi, where Earth-sized worlds could exist, suggesting a collision took place between a planet and one or more comets.

The Eta Corvi system is approximately one billion years old, which researchers think is about the right age for such a hailstorm.

Similar to our Solar System

Astronomers used Spitzer’s infrared detectors to analyse the light coming from the dust around Eta Corvi. Certain chemical fingerprints were observed, including water ice, organics and rock, which indicate a giant comet source.

The light signature emitted by the dust around Eta Corvi also resembles the Almahata Sitta meteorite, which fell to Earth in fragments across Sudan in 2008. The similarities between the meteorite and the object obliterated in Eta Corvi imply a common birthplace in their respective planetary systems.

A second, more massive ring of colder dust located at the far edge of the Eta Corvi system seems like the proper environment for a reservoir of cometary bodies. This bright ring, discovered in 2005, is about 150 times the distance from Eta Corvi as the Earth is from the Sun.

Our Solar System has a similar region, known as the Kuiper Belt, where icy and rocky leftovers from planet formation linger. The new Spitzer data suggest that the Almahata Sitta meteorite may have originated in our own Kuiper Belt.

Adapted from information issued by NASA / JPL-Caltech / R. Hurt (SSC).

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