Temperate, Jupiter-Sized World Resembles the Planets of Our Solar System

By Andrew Moseman | March 17, 2010 3:56 pm

corot9bIt’s the size of Jupiter, orbits at about the distance of Mercury, and isn’t too far from the temperature range of Earth. Meet Corot-9b, the newest find in the cavalcade of exoplanets and the one its discoverers say is most like the worlds of our own solar system.

“Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium,” said team member Tristan Guillot of the Côte d’Azure Observatory in Nice, France. “And it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures” [Space.com]. The large group of astronomers reporting the find in Nature estimate the planet’s temperature at a range between just below zero and slightly above 300 degrees Fahrenheit. It completes an orbit in 95 days, though it’s about 1,500 light years away.

The new exoplanet draws its name from the French space agency’s Corot (Convection, Rotation and planetary Transits) satellite, which first spotted it by noticing its star dim as the planet passed in front. Actually confirming a planetary cause of that dimming takes painstaking follow-up work at telescopes on the ground. Most often the researchers look for Doppler shifts in the host star’s light as the planet’s gravity regularly tugs the star nearer to and then farther from Earth [Scientific American]. Back in September, the Corot satellite also was the first to find Corot-7b, which was the first exoplanet discovered to be close to the Earth in size.

Determining Corot-9b’s distance from its star and the type of that star allowed the team, led by Hans Deeg, to hypothesize that the planet’s temperature range is close to that of Earth’s. But is it a pale blue dot like our own home world? “We don’t know the colour. It’s likely that it has high atmosphere water clouds which might make it blue but that depends on the mixture of gases which we really do not know” [BBC News], Deeg says.

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Image: Ilustration courtesy Instituto de Astrofísica de Canarias

  • Catsceo

    Couldn’t there be a possibility of life-sustaning exomoons around COROT-9b?

  • http://lablemming.blogspot.com/ Lab Lemming

    Moons would cause transit timing variations.

  • http://clubneko.net nick

    I thought nitrogen was responsible for our blue atmosphere, not the clouds?

  • ed

    so how do u explain the reddish and yellowish colors at dusk dawn?…color you see inside the atmosphere has to do with the distance light travels in the atmosphere. Gas composition has more to do with perceived color when you are an observer outside the planets atmosphere

  • ed

    and our planet is blue from space because of the blue ocean water

  • Dedalus1953

    Isn’t our planet blue from space, not because of “blue water,” but because of water reflecting blue sky? Which, if you want to be semantically picky, means the water actually is blue (just as it’s grey on those gloomy days).

    But we digress …

  • Gergy

    Ed, Your wrong. The ocean is blue because it reflects the light of the blue atmosphere.

    And it is Ozone (O3) that causes the atmosphere to be blue. As dusk falls more ozone gets in the way of the suns light reaching your eye, In turn reducing the speed of the light and forcing it to transform into a deeper colour in the spectrum.

    Jesus, I’m only 15 years old you guys…

  • Georg

    what an assemble of wrong ideas!
    I’d thought that such nonsense is no longer possible
    today, when information is not more than some
    mouseclicks away…
    Anybody ever heard of “Rayleigh scattering”?

  • Grant H

    Rayleigh scattering causes the sky to appear blue due to nitrogen and oxygen scattering the blue wavelength of the sun’s light. The affect causes the sky to appear blue to an observer from both within the Earth’s atmosphere and from outside of it. Look at photos of the Earth from space to see that the atmosphere appears to be layered striations of blue gas.
    This same Rayleigh scattering affect causes parts or all of the sky to turn red during a sunset or sunrise due to the observer’s point of observation. Basically the blue wavelength of the sun’s light is still scattered by the atmosphere, but there is sufficient atmosphere between the observer and the sun that there is only a small quantity of the blue wavelength of the sun’s light reaching the sky in the observer’s location and the red wavelength is far more prominent. The percent of the globe in day and night is far higher at any one time than the percent of the globe experiencing sunset and sunrise, so it’s fair to say the Earth’s sky is blue (not including the affect of clouds).
    Generally speaking, if nitrogen and/or oxygen is the prominent component of the atmosphere, there’s a good chance there’ll be a blue sky. Although I want to add that I’m certain Hans Deeg is far more knowledgeable than myself and of course I’m happy to believe him when he says that water vapour mixed with certain gasses can cause a planet to appear blue.

  • Georg

    Hello Grant H,
    this sounds a lot better, only “Nitrogen and Oxygen” is not correct.
    Any gas (substance) shows that raleigh scattering. (Of course with
    substances having a colour like eg chlorine the scatter is obscured)
    The intensity varies with polarizatibility of the gas,
    thus it is a function of electron density as a first approximation.
    Ammonia or Hydrogen will be weaker in scattering than air,
    carbon dioxide stronger, Ethane about equal to air.
    (At the same pressure)

  • Grant H

    Hi George,
    Any gas? I thought that nitrogen and oxygen particles are about the right size to affect the blue wavelength, while the particles of other gasses are generally either too big or too small…?
    I could be wrong, I’m getting older and school’s descending further into the past.

  • Georg

    Hello Grant H,
    not only any gas in fact any substance shows Rayleigh scattering.
    But in practice most liquids are not pure enough.
    (Having some colorized impurities)
    An example, where it shows up, is the scattering in the purest
    light wave guide fibres. If the material is pure enough,
    the tranparency is limited by the Rayleigh scattering only.

    Rayleigh scattering comes from the electrons of a substance,
    which are “shaken” a little bit by the electromagnetic light wave.
    (This is the classical explanation, the quantum explanation is
    much more difficult, for that my school time is too lang ago)

  • Grant H

    George, thanks. It’s good to learn something new.
    I had the idea in my head that Rayleigh scattering occurred because light waves exhibit the properties of particles in certain situations.

  • m

    amusing – a 15 year old thinks the speed of light changes

    George – i had thought light scatters because we observe the angle at whcih light passes across the atmosphere when the earth turns? Like light passing through a prism…turn the prism and you will see different colors. turn slightly from 180 degrees to see blues, purples, etc. turn even more and start seeing reds. Go back to 180 and start seeing white again.

    any insights George?

  • amphiox

    “amusing – a 15 year old thinks the speed of light changes”

    Except that it does. Although that post was wrong on specifics. The speed of light varies depending on what substance the light is traveling through. That is how lenses and prisms work and why gemstones sparkle.

    Though I’m not sure if the difference in speed between vacuum and air, (or any specific gases or mixture of gases) is all that significant.

  • ed

    great responses…

  • Cory

    Yup, light can definitely slow down. It just can’t be sped up past “c”.

  • andy

    Unfortunately the planet is rather too close to the star for habitability of moons to be likely, but it is the first transiting exoplanet for which a system of massive satellites is a reasonable possibility.

    As for the transit timing variations (TTV), as far as I can tell, CoRoT only observed one complete transit (16 May 2008), the observations of the second transit were affected by instrument interruption. The discovery paper also refers to observation of a transit on 1 June 2009 at ground-based observatories. Not sure how much information about possible TTVs can be obtained from such a sparse dataset. Unfortunately the discovery paper, being in Nature, is short and doesn’t address the TTV issue.

  • Camille


    Just a comment on the formatting of these articles– the author’s name & the date of the article should appear at the beginning of the article, not the end. It’s hard to find the date of the article– it’s important to know if you are reading something that’s current or not.


  • New Moons

    In our solar system the combined mass of the moons orbiting each gas giant is always one ten thousandth the mass of their host planet. So, if the 1:10,000 mass ratio rule holds true for Corot 9b, it could possess a moon almost as massive as the planet Mercury.

    Being quite close to its star could have made it difficult for the moons of Corot 9b to have held onto any appreciable atmosphere. After all, Mercury, which is only slightly closer to the sun, has had its atmosphere completely blown away. However, since Mercury is almost tidally locked to the sun and only had a very weak magnetic field to protect its atmosphere, it might not be a good analogy. Perhaps, a moon in close orbit around Corot 9b is afforded some protection by sharing Corot 9b’s magnetic field or has a strong magnetic field itself, induced by the combined tidal pull of Corot 9b and other nearby moons on its iron core and therefore, unlike Mercury, has managed to keep an atmosphere.

    If, any moon of Corot 9b does possess an atmosphere, it could be quite an exotic place, even hotter than Venus.

  • New Moon

    The strength of the tidal forces acting on a Mercury sized moon in a stable orbit around Corot 9b would not be nearly enough to induce plate tectonics and a magnetic field would only protect the moon’s surface from dangerous radiation and would not help it hold onto any significant atmosphere.

    Therefore, only near Earth sized planets captured by Corot 9b, in its early history as it moved tracked towards Corot 9, could theoretically have held onto any kind of appreciable atmosphere, to this day.

    So, in conclusion, sorry for the lazy and ill thought out last comment but I obviously have way too much time on my hands!

  • Faber

    The discoveries of these exoplanets is one of the most exciting aspects of astronomy, amazing that we can detect them from such vast distances.


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