Feeds

Mega-planet spotted orbiting fading star

Big and clever

Build a business case: developing custom apps

Astronomers have discovered the biggest transiting exoplanet yet. Orbiting a fading star in the constellation of Hercules, planet TrES-4 is a whopping 70 per cent bigger than Jupiter.

Computer generated impression of the giant planet orbiting its home star. Credit: Jeffrey Hall, Lowell Observatory

To put these numbers in context, Jupiter is a mere 16 per cent (or so) bigger than Saturn, but is almost four times the mass. Although volume scales as the cube of the radius increases, as a planet gets heavier its increased gravity tends to collapse it inwards, and so the stepwise increase in mass is even steeper that you would expect.

But the alien world has a twist in its tale: despite its enormous size, it is less massive than our solar system's biggest planet, making it roughly as dense as a cork.

The planet is so diffuse, that its gravity only has the most tenuous of grasps on its upper atmosphere: the team at the Lowell Observatory who made the discovery suggests the planet probably has a diaphanous tail of material spiralling towards its parent star.

"It is about 70 percent bigger than Jupiter, the Solar System’s largest planet, but less massive, making it a planet of extremely low density. Its mean density is only about 0.2 grams per cubic centimetre, or about the density of balsa wood," says Georgi Mandushev, the lead author of the paper detailing the discovery.

And it the planet's density, or lack thereof, that has the boffins baffled.

"TrES-4 appears to be something of a theoretical problem,” said Edward Dunham, Lowell Observatory Instrument Scientist. "It is larger relative to its mass than current models of superheated giant planets can presently explain. Problems are good, though, since we learn new things by solving them."

As with all transiting planets, TrES-4 betrayed its existence by causing an observable dip in its parent star's brightness as it passed between the star and our telescopes. The transit was confirmed by the Sleuth telescope, maintained by David Charbonneau (CfA) and Francis O'Donovan (Caltech), at Caltech's Palomar Observatory.

The stats: TrES-4 is about 1400 light years from us, and orbits its parent star in three and a half days, at a distance of about 4.5m miles. This distance is small enough in astronomical terms (it is just 12 times the distance from Earth to the moon) that the planet's surface is extremely hot, clocking in at around 1,600 Kelvin. ®

Boost IT visibility and business value

More from The Register

next story
Just TWO climate committee MPs contradict IPCC: The two with SCIENCE degrees
'Greenhouse effect is real, but as for the rest of it ...'
Asteroid's DINO KILLING SPREE just bad luck – boffins
Sauricide WASN'T inevitable, reckon scientists
Brit amateur payload set to complete full circle around PLANET EARTH
Ultralight solar radio tracker in glorious 25,000km almost-space odyssey
Boffins spot weirder quantum capers as neutrons take the high road, spin takes the low
Cheshire cat effect see neutrons and their properties walk different paths
NASA Mars rover FINALLY equals 1973 Soviet benchmark
Yet to surpass ancient Greek one, however
Famous 'Dish' radio telescope to be emptied in budget crisis: CSIRO
Radio astronomy suffering to protect Square Kilometre Array
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Maximize storage efficiency across the enterprise
The HP StoreOnce backup solution offers highly flexible, centrally managed, and highly efficient data protection for any enterprise.