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First Image of Extrasolar Planet Confirmed
An anonymous reader writes "The year-long controversy about whether the European Southern Observatory had indeed captured the first picture of an extrasolar planet has apparently been resolved. Journal publication today of a fuzzy image of this Jupiter-sized, extrasolar planet led Christophe Dumas, a member of the discovery team, to say enthusiastically: 'The thrill of seeing this faint source of light in real-time on the instrument display was unbelievable. Although it is surely much bigger than a terrestrial-size object, it is a strange feeling that it may indeed be the first planetary system beyond our own ever imaged.'"
It's actually (according to the BBC and eso.org) 5x the size of Jupiter, or about half the size of our sun
Remember that when astronomers talk about "size", they are actually talking about mass. Our sun is 1000x the mass of Jupiter, so this planet is still 200x smaller.
The minimum mass to call a big planet a "star" is about 70 times Jupiter (that's the minimum mass to start nuclear fusion).
Wrong, this planet is *not* 5x the size of Jupiter. It has a *mass* 5x that of Jupiter. Due to gravity etc no planet can grow much beyond the size of Jupiter. Don't remember the exact size but it was some 10-30% larger that was the limit.
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The reason why they are called failed suns is because they are. Gravity pulls the matter in towards the center of the planet. This makes the center hot and dense (think ideal gas law). If there is enough mass in the planet, the gravitational attraction is strong enough that it forces the pressure and temperature at the planets core to exceed the thresholds required for nuclear fusion (hydrogen to hydrogen) to occur. If the body is massive enough to do this it is a bona-fide star. Stars slightly less massive are known as brown dwarfs (there are technical reasons why they are not called planets), and bodies even less massive are planets.
Jupiter is giving off heat because the gravitational attraction is causing the temperature and pressure inside the star to be relatively high -- just not high enough for fusion.