Astronomy Now Home
Home Magazine Resources Store

On Sale Now!

The October 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). Astronomy Now is the only astronomy magazine specially designed to be read on tablets and phones. Download the app from Google Play Store or the Apple App Store.

Top Stories

Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...

Exoplanet clouds out atmospheric models
Posted: 31 August 2010

Bookmark and Share

Astronomers studying a young gas giant planet with the W. M. Keck Observatory have found that the planet sports an atmosphere unusually thick with dust clouds.

The planet, HR 8799b, is one of three gas giants orbiting its parent star HR 8799 in the constellation Pegasus, 130 light years away. The system was discovered by direct imaging in 2008.

Keck II image of the young extrasolar planet HR 8799 b, seen as the point source in centre of image. The bright light from the parent star HR 8799 is seen in background in yellow/red and has been removed in an annular region centered on the planet. Image: Brendan Bowler and Michael Liu, IfA/Hawaii.

Astronomers from the University of Hawaii used the W. M. Keck Observatory's adaptive optics system to obtain spectra of the light emitted by the planet to obtain information on the planet's temperature, chemical composition and cloud properties. The presence or absence of gaseous methane can be used as a thermometer, but the team found very little traces of methane. Assessing their spectrum and comparing it with archival data and models, the team estimated the coolest possible temperature as 1,200 kelvin.

But the models were not able to match all the data. Current theoretical models predict the seven Jupiter mass planet should be about 400 Kelvin cooler than they measured, based on the age of the planet and the amount of energy it is currently emitting. The team propose that the planet is much more dusty and cloudy than current models predict.

“Direct studies of extrasolar planets are just in their infancy,” says University of Hawaii astronomy professor Michael Liu. “But even at this early stage, we are learning they are a different beast than objects we have known about previously.”

Just six of the nearly 500 known exoplanets were detected through direct imaging, and three of those are around HR 8799.

“Adaptive optics systems on Keck and other large ground-based telescopes make sharper images than even the Hubble Space Telescope,” says co-author Trent Dupuy. “With adaptive optics, we are learning an incredible amount about objects that are smaller than the lowest-mass stars and larger than the most massive gas-giant planets in our Solar System.”

The results of the study will be published in a forthcoming edition of the Astrophysical Journal.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!


© 2014 Pole Star Publications Ltd.