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The Corot satellite strikes again with another fascinating planet discovery. This time, the newly discovered gas giant planet may have an interior that closely resembles those of Jupiter and Saturn in our own Solar System.
Very few planets are temperate enough to allow the presence of liquid water, but the newly discovered Corot-9b is one of them. It was found on 16 May 2008 and orbits its star every 95.274 days, a little longer than Mercury takes to go round the Sun.
More than 400 exoplanets have been discovered so far and 70 of them have been found by the ‘transit’ method. A transit is a kind of eclipse and occurs when a celestial body passes in front of its host star and blocks some but not all of the star’s light. This temporarily dims the apparent brightness of the star and enables the planet’s mass, diameter, density and temperature to be deduced. The time between similar transits gives the orbital period of the planet.
Corot-9b is the first transiting planet to have both a longer period and a near-circular orbit. Its orbit is slightly elliptical but at closest approach to its parent star it reaches a distance of 54 million kilometres. Although that is only about the distance of Mercury in our Solar System, it is by far the largest orbit of any transiting planet found so far. Because it orbits a star cooler than our Sun, calculations estimate that Corot-9b’s temperature could lie somewhere between –23°C and 157°C.
Corot-9b has a radius around 1.05 times that of Jupiter but only 84% of the mass. This leads to a density of 0.90 g/cc, or 68% that of Jupiter. “Corot-9b is the first exoplanet that is definitely similar to a planet in our Solar System,†says Hans Deeg, a researcher at the Instituto de AstrofÃsica de Canarias, whose paper on the discovery is published today in Nature.
One of the methods for detecting exoplanets is to look for the drop in brightness they cause when they pass in front of their parent star. Such a celestial alignment is known as a planetary transit. From Earth, both Mercury and Venus occasionally pass across the front of the Sun. When they do, they look like tiny black dots passing across the bright surface Such transits block a tiny fraction of the light that COROT is able to detect. Credits: CNES
The similarity is caused by the fact that Corot-9b is sufficiently far from its star to prevent tidal forces from heating its interior. Tidal forces are created by the strength of gravity weakening from the front to back of the celestial body. When the difference between the near side and the far side is great, the tidal force can prevent the planet from spinning quickly, forcing it to only show one face to the star. It can also provide heat to the interior of the planet, changing its physical condition.
Based on calculations, neither of these is possible in this case. “Although we don’t know, because we can’t see the planet directly, there is reason to believe that this planet has a normal day-night cycle,†says Malcolm Fridlund, ESA Project Scientist for Corot. It means that lacking a tidal heat source, Corot-9b’s interior is likely to have remained similar to the gas giants in our Solar System.
There is also one other tantalising possibility about this world. Although the planet itself is a gas giant and hence has no solid surface to stand on, what if it possessed a moon like Saturn’s Titan? If the temperature were towards the lower end of the estimated range, then any moon would be an ice ball. If it were towards the upper end, it would be rather too hot for liquid water. But what if it were somewhere in the middle? …
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Corot (Convection rotation and planetary transits) is a mission led by the French space agency, CNES, with contributions from ESA, Austria, Belgium, Germany, Spain and Brazil. |
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I just finished watching Exodus Earth (Space Week) on the Science Channel. The host, hunky British quantum physicist Basil Singer, delves into the eventual exploration and human colonization of planets and large satellites within our own solar system and exoplanets of nearby stars (Gliese 581c for example).
He does not mention the role machine intelligence will ultimately play in space exploration and the evolution of humans. Which made me wonder, is consciousness and thought process relegated to the realm of the biological? Or, is machine intelligence an emergent property of intelligent beings?
We simply don’t expend enough money, time or effort in learning all we can about the universe in which we live. Or the galaxy in which we live. Nor in our own solar system or own planet.I don’t suspect this record will last for long, despite our inadequate sciences, we will discover bigger beasts.
Not all stars have orbiting planets, particularly the new ones, the ejected matter or spare matter in these hasn't coalesced and cooled enough to become planets.
The milky way is just one galaxy amongst a whole bunch.
Go look at some shots from the Hubble Telescope and you'll see our little galaxy has many friends out there, every one of them with billions of stars (a lot of those stars with their own solar systems)
I really think the planet-vs.-moon problem is a non-problem. Moons, as in satellites, are pretty well-defined. They're objects that orbit another object. In fact, you could conceivably define a planet as a star's satellite. Aha, you say, but you're including asteroids and comets. Well, sure, they're already considered minor planets. Probably the most acceptable way to break the categories down is the way that the IAU did: minor planets (small solar system bodies that are not round), dwarf planets (little round things) and dominant planets (bigger round things). In our own solar system, it's rather obvious which are the dominant planets, but we already know that the “clearing out the orbit” idea doesn't work in other solar systems (for example, large resonant planets such as HD 82943 b and c). I think the “orbit the sun” requirement doesn't work, either, because that ties you up when it comes to the issue of rogue or free-floating planets. We shouldn't get too doctrinaire about such a common term. Now, on the original topic, I definitely agree that adding Eris or Makemake or 1992 QB1 will make no difference in the efficacy of astrology. But we should figure out what to do about that asteroid, whether it comes on Wednesday, in 2012, 2036 or 4028.
If it orbits a sun and formed as part of that sun's accretion disk, then its a gas giant planet. If it doesn't orbit another sun or didn't form as part of a sun's accretion disk (captured object), then its a brown dwarf.
Not all stars have orbiting planets, particularly the new ones, the ejected matter or spare matter in these hasn't coalesced and cooled enough to become planets.
Your right on the solar system description.
The milky way is just one galaxy amongst a whole bunch.
Go look at some shots from the Hubble Telescope and you'll see our littl galaxy has many friends out there, every one of them with billions of stars (a lot of those stars with their own solar systems)