NASA catches light from another planet

Scientists working with NASA's Spitzer Space Telescope have directly observed light from a known extra-solar planet. The US space agency has hailed the breakthrough as the beginning of a "new age" in planetary science.

Regular Register readers might remember a picture of an extra-solar planet, released in January this year. This is a mere planetary candidate however, so is not quite so exciting to the men and women in white coats. The lead scientist on that project, Glenn Schneider, told New Scientist that he suspects the "planetary mass" formed quite differently to the planets in our own solar system.

This new research involves planets classed as "Hot Jupiters", which orbit sun-like stars, and probably evolved in a similar way to Earth. The results reveal that the so-called "hot Jupiters" are worth of the name. Both planets clock in at least 1,000 Kelvin, or 727 degrees Celsius. Further analysis is expected to uncover more detail about the condition and composition of the planets' atmospheres.

The technique is reasonably simple. The team aimed Spitzer at two already-confirmed planets, named HD 209458b and TrES-1 (in traditionally romantic space parlance) and their parent stars. Watching in the infrared, the researchers collected the total amount of light from star and planet combined. Then, when the planet passed behind the star, they measured the amount of light left over. The difference between the two samples let them know how much infrared light was emanating directly from the planet. More details here.

Drake Deming from NASA's Goddard Space Flight Center is lead author on one of the studies, to be published in Nature. He told New Scientist: "This is the first time we have actually seen light."

Dr David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, lead author of the other paper, to be published in Astrophysical Journal, commented: "We've been hunting for this light for almost 10 years, ever since extra-solar planets were first discovered. In visible light, the glare of the star completely overwhelms the glimmer of light reflected by the planet. In infrared, the star-planet contrast is more favourable because the planet emits its own light."

The Spitzer telescope was not designed to image extra-solar planets, and is best suited for studying planets that transit their sun-sized parent star, and are at a distance of up to 500 light-years. In 2016, NASA plans to launch the Terrestrial Planet Finder coronagraph. This will be able to snap pictures of extra-solar planets as small as Earth. ®

Update

Our thanks to vulture-eyed reader Thomas Davie for pointing out that a team of astronomers at St. Andrew's University did something very similar last century. In a statement at the time, the Particle Physics and Astronomy Research Council described the system as follows: "The planet’s parent star, Tau Bootis, is located 55 light years from the Earth. It is easily seen by the naked eye but its planet has only been suggested at before based on the "wobble" in the light coming from the star as the planet travels around it."

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