Feeds

Mega-planet spotted orbiting fading star

Big and clever

High performance access to file storage

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. ®

High performance access to file storage

More from The Register

next story
Fancy joining Reg hack on quid-a-day challenge?
Recruiting now for charity starvation diet
Red-faced LOHAN team 'fesses up in blown SPEARS fuse fiasco
Standing in the corner, big pointy 'D' hats
KILLER SPONGES menacing California coastline
Surfers are safe, crustaceans less so
LOHAN's Punch and Judy show relaunches Thursday
Weather looking good for second pop at test flights
Discovery time for 200m WONDER MATERIALS shaved from 4 MILLENNIA... to 4 years
Alloy, Alloy: Boffins in speed-classification breakthrough
Elon Musk's LEAKY THRUSTER gas stalls Space Station supply run
Helium seeps from Falcon 9 first stage, delays new legs for NASA robonaut
Top Secret US payload launched into space successfully
Clandestine NRO spacecraft sets off on its unknown mission
New FEMTO-MOON sighted BIRTHING from Saturn's RING
Icy 'Peggy' looks to be leaving the outer rings
prev story

Whitepapers

Top three mobile application threats
Learn about three of the top mobile application security threats facing businesses today and recommendations on how to mitigate the risk.
Combat fraud and increase customer satisfaction
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
SANS - Survey on application security programs
In this whitepaper learn about the state of application security programs and practices of 488 surveyed respondents, and discover how mature and effective these programs are.