‘Sauna-like’ planet found orbiting distant star

A newly-discovered planet orbiting a distant star is covered by deep oceans, according to an international team of astronomers. The ‘water world’ is only a little larger than Earth, but it is much less dense, leading the astronomers to suggest it is exceptionally watery, with a small rocky core.

...but what good's an ocean without a beach? Image: Hypothesisnow

With a ‘surface’ temperature of 190^oC, the planet may also have a rather steamy, ‘sauna-like’, atmosphere.

The planet, named GJ 1214b, consists of almost 50% water: in comparison, only around 0.06% of the Earth’s mass is water, despite it being known as the ‘blue planet’. Astronomers inferred the existence of the planet from the way it dimmed the light of its parent star every time it passed in front of it – once every 1.6 days. It also causes the star to wobble slightly as it orbits – another tell-tale sign of an orbiting planet.

The amount of light-dimming and the wobble told astronomers the size and mass of GJ 1214b, which in turn allowed them to work out its density. GJ1214b is slightly larger than Earth (its radius is 2.68 times that of Earth) and much less dense (1.9 grams per centimetre³ compared to Earth’s 5.5 grams per cm³. The only plausible way a planet could be that big but weigh so little would be if it consisted of lots of water around a rocky core, perhaps with a thin atmosphere of hydrogen and helium.

The presence of liquid water is rather exciting because, as far as we know, water is one of the prerequisites of life, and finding inhabited planets is one of the long-term goals of astronomy. The new discovery also takes us one step closer to finding a truly Earth-like planet out there somewhere. NASA’s Kepler space telescope is sensitive enough to find exo-planets even smaller than GJ 1214b, so maybe one day we’ll find a home-from-home. The only tricky part then will be actually getting there…

Paper Reference: Charbonneau , D., et al, (2009). A super-Earth transiting a nearby low-mass star. Nature, 462, p891-894. doi:10.1038/nature08679

Life on Earth is quite unlikely

Scientists have concluded that life is unlikely to form on planets around stars like our Sun because these stars emit high levels of x-rays and ultraviolet light early in their existence – both deadly to life as we know it.

“The Sun does not seem like the perfect star for a system where life might arise.” said Professor Edward Guinen from Villanova University in the USA, who carried out the work alongside other researchers from the USA and from the Netherlands. Guinen and colleagues suggest that smaller, cooler stars called orange dwarfs are the best places to look for life. Orange dwarfs live much longer than yellow stars like our Sun, and their “goldilocks zone” – the area of space surrounding the star in which planets are most likely to harbour life – will also last much longer, giving life a better chance of getting started.

And it doesn’t stop there. According to Guinen, “we have also found indications that planets like Earth are also not necessarily the best suited for life to thrive”. Instead, larger planets may be better suited to harbouring life because they can hold on to their atmospheres for longer due to their stronger gravity. They also have much larger iron cores, which support a more powerful magnetic field for longer, protecting the atmosphere and any developing life from harmful cosmic rays.

The researchers made their surprising discovery by looking at other stars very similar to our Sun, but which are much younger. The Sun, at 4.5 billion years old, is in a relatively calm phase of its lifecycle. In its early days, when it was less than half a billion years old, the Sun went through a wild phase, throwing out massive amounts of destructive radiation and making it very hard for life to survive.

Obviously life on Earth has survived despite the odds, but the work could alter where we look in our ongoing hunt for extraterrestrial life. There are many more orange dwarfs than there are Sun-like stars in the galaxy, so maybe it will be easier than we thought to find life out there.

Stars - they grow up so fast... Image: IAU

Out of this world

As you may have heard, Monday 20th July 2009 marks the 40th anniversary of man’s first landing on another world – the moon. To celebrate this achievement (and jump on the media bandwagon!), Hypothesis Now will be running a series of space-themed stories over the next few days.

NASA now sees the moon as a stepping stone out of the Earth’s gravity well and onwards to the rest of the solar system. But what do we know of our nearest planetary neighbours? A few recent news stories show just how far our understanding of worlds beyond our own has come:

Missions to Mars

The surface of Mars. Such a welcoming place...*

Mars, the enigmatic Red Planet, is the latest focus of international space research and exploration efforts. A new study has provided vital measurements of the infrared absorbance of different types of soils that might be found on Mars. Using this information, scientists will be able to make accurate predictions of Martian surface conditions from instruments in orbit, which will be vital when future missions to the Red Planet look for areas where water, or even life, may be hidden. NASA’s next Mars mission – the Mars Science Laboratory – is due for launch in 2011.

Visions of Venus

An extremely expensive firework? The Venus Express is sent on it's way **

Last week saw the announcement that the European Space Agency’s Venus Express probe has found evidence that Venus once had an ocean and plate tectonics. Using infrared to “see” through the thick Venusian atmosphere, the probe mapped the surface of Venus’ southern hemisphere – the reflected infrared light suggested it was composed of granite rock – which can only form under the influence of both water and plate tectonics.

In terms of size, Venus is the most Earth-like planet in the solar system, yet in many other respects it differs markedly. The planet is wrapped in thick yellow clouds containing sulphuric acid and a runaway greenhouse effect sees surface temperatures reaching 460^oC! These new results will help astronomers understand why the planets have ended up with such contrasting climates.

Colliding Comets

Comets: Responsible for life on Earth?***

3.8 billion years ago the Earth and Moon were caught in a barrage of asteroids and comets caused, it is now thought, by the rearrangement of the gas giant planets – Jupiter, Saturn, Uranus and Neptune. The impacts on Earth altered the environment, making it more suitable for the emergence of life.

A new model suggests the rearrangement of the major planets flung many comets inwards from the cold, dark edge of interstellar space. The comets collided with asteroids, dislodging them from their stable orbits and sending fragments of both towards Earth. The results shed light on the last dramatic rearrangement of our solar system and tell scientists much more about how solar systems like ours may have formed.

*Image credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University.

**Image credit: Credit ESA/STARSEM-S. CORVAJA.

***Image credit: Miketsukunibito. Used under GDFl License.