Astronomers verify directly imaged planet

Posted 06-22-2010 by Liz Kruesi

A group confirms that a planet orbitting 1RXS J160929.1–210524 is about 8.4 times Jupiter's mass and orbits at 330 times times the distance from Earth to the Sun. Gemini Observatory photo
In the fall of 2008, a number of institutions announced that their scientists had directly imaged planets orbiting around other stars — one of the biggest stories of the past few years of astronomy. Still, some of the astronomy teams acknowledged that there was a chance the imaged planet and sun were either actually chance alignments or a star and a companion brown dwarf.

One of those groups recently re-imaged their discovered system with the same instrument — the Gemini North telescope on Mauna Kea in Hawaii. David Lafrenière of the University of Montréal and Ray Jayawardhana and Marten H. van Kerkwijk of the University of Toronto have confirmed that the object they initially imaged is indeed a companion planet to the young star 1RXS J160929.1–210524. Jayawardhana adds: “We also obtained images/spectra at other wavelengths, which confirm the temperature and mass we derived in 2008.”

The team determined that the planet is about 8.4 times Jupiter’s mass, and is about 1800 kelvin (2780° Fahrenheit). The planet orbits its star at 330 times the distance from Earth to the Sun. Its star is similar to ours in a couple of ways. It has a mass about 85 percent of the Sun’s and a temperature about 70 percent as great as our star’s. However, it’s much younger. While our Sun is roughly 4.6 billion years old, 1RXS J160929.1–210524 is only about 5 million. 

The team’s findings will appear in a future issue of The Astrophysical Journal. You can read the preprint at For more about the initial discovery, see the news release "Gemini North telescope captures first picture of likely planet."


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  • adastragrl said:

    If the star is ~15% smaller than our sun and 30% cooler and  the planet is 330AUs away, wouldn't the planet be much cooler? How can the planet be 2780deg F??

    June 22, 2010 2:54 PM
  • Rich Talcott said:

    If my understanding is correct, the reason is that it is so young (5 million years old). Such young gas giants are still radiating away the energy from their formation, so they are much warmer than they would be if at the age of Jupiter (4.5 billion years). The fact that the planet also weighs a lot more than Jupiter would further increase its temp.

    Your are right that if the only source of heat were from its star, it would be much cooler. Even Jupiter radiates a bit more energy than it receives from the Sun.

    June 22, 2010 3:47 PM

About Liz Kruesi

Liz Kruesi
Liz Kruesi is an associate editor with Astronomy magazine.
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