Up close with the planet hunters


Earth-like planets orbiting distant stars may be far more common than astronomers realised, which greatly increases the possibility of other life in the universe, writes DICK AHLSTROM

THE MILKY Way galaxy may be littered with Earth-like planets, according to new research. Far from being a rarity, up to 20 per cent of stars similar to our Sun may be orbited by rocky, watery planets.

And where there is water, can we assume there is life? Certainly the more Earth-like planets with water that can be found, the greater the likelihood that we might find one that harbours life.

Research findings issued earlier this week at the Royal Astronomical Society’s national astronomy meeting in Glasgow suggest that we will identify endless numbers of potential homes should we ever have to leave Earth – provided of course we develop a way to reach them.

The search for exoplanets, planets that orbit stars away from our own solar system, has been a popular subject for astronomers presenting findings at the Society’s 2010 meeting.

And exoplanets also feature in research that appears this morning in the journal Nature about a new more sensitive method for finding distant planets.

The discovery of new exoplanets has become a near daily occurrence – with 446 found as of last Tuesday – since the first was found in 1995.

Most located so far are gas giants like Jupiter, so evidence that galaxies across the universe might have huge numbers of planets more similar to Earth proved a dramatic finding for delegates at the Society’s meeting.

Dr Jay Farihi lead a team at Leicester University that surveyed White Dwarfs, the compact remains of stars that were once like our own Sun.

He found that at least 3 per cent and as many as 20 per cent of these stars showed signs of “contamination”. They should have contained nothing more than helium and hydrogen but many also contained heavy element “pollutants” including metals like magnesium and iron.

The prevailing theory held that this pollution was gradually mopped up from the interstellar space between stars, trapped by the star’s gravitational field. But Farihi showed that in fact the heavy elements could only have come from rocky planetary debris. He was able to show that the chemical pollution came from the break-up of rocky planets, with the material deposited in the star in its younger days.

This, Farihi says, implies that a similar proportion of stars akin to our sun and also slightly larger stars are able to build up rocky planets. Effectively the astronomers were conducting a form of “stellar archeology”, picking over the remains of a former sun and its surrounding planets.

Once found, scientists can sample the light signal coming from the planet, looking for signs of oxygen, carbon dioxide or methane, possible indicators of active bacteriological or plant life.

Delegates to the Edinburgh meeting also heard on Tuesday about the discovery of nine new exoplanets, but were dumbfounded by the news that some of them were orbiting their stars in the wrong direction.

Current theories require that all planets should orbit in the same direction as the star’s rotation, but these new exoplanets break these rules.

Separately, Naturereports on a new way to find difficult to spot exoplanets orbiting very close to their host stars. Exoplanets orbiting tightly can’t readily be seen because of the star’s own glare, but scientists at the Jet Propulsion Lab in California developed a new technique that will reveal these hidden planets.

twitter: @dickahlstrom

Talking the science talk

THE annual Science Speak competition takes place at the RDS in Dublin on April 27th, when university students will explain their research to a lay audience. Now in its fifth year, the event showcases the talents and creative thinking of some of our brightest science and mathematics students.

A panel of judges select the top three students, and this year the panel includes Met Éireann meteorologist Evelyn Cusack; RTÉ presenter Keelin Shanley; former Rose of Tralee, teacher and physicist Aoibhínn Ní Shúilleabháin; head of Discover Science and Engineering Peter Brabazon and Dick Ahlstrom, Science Editor of The Irish Times.

RTÉ broadcaster Pat Kenny will host the event and Tánaiste Mary Coughlan will present the prizes. There is a prize fund worth €1,900, with a top award worth €1,000.

The event is free and open to the public and takes place at 7pm in the RDS Concert Hall. Advance booking for this event is essential.

Book online at universityscience.ie, e-mail science@rds.ie or contact the RDS at 01-2407217. Science Speak is organised by the RDS and The Irish Timesin association with Irish Universities Promoting Science.