[aldo_14]

http://www.theregister.co.uk/2006/01/25/smallest_exoplanet/

An international colloboration of astronomers has used a microlensing technique to spot an Earth-like exoplanet just five times bigger than our own piece of rock - the smallest such body discovered so far, and only the third pinpointed with microlensing from a list of around 160 known exoplanets.

The snappily-named OGLE-2005-BLG-390Lb is orbiting a red dwarf "roughly five times less massive than our Sun", 25,000 light years from Earth, close to the centre of our own Milky Way galaxy. Its orbital period is ten years and it lies around three times further from its parent as we do from the Sun.

[Taristin]

What is an exoplanet? And by "Earth-like" what do they mean?

[karajorma]

Exoplanets are any planet not in our Solar System IIRC.

I presume Earth-like means rocky (possibly with an atmosphere) as opposed to gas giants like pretty much every other exoplanet spotted so far.

[Shade]

An exo-planet is simply a planet outside our solar system. Short for extra-solar planet, in fact. And earth-like gives the wrong impression, the proper term being terrestrial planet which is a planet composed of minerals rather than gas (which are called jovian planets, after jupiter).

[Prophet]

http://www.theregister.co.uk/2006/01/25/smallest_exoplanet/

The snappily-named OGLE-2005-BLG-390Lb is orbiting a red dwarf "roughly five times less massive than our Sun", 25,000 light years from Earth, close to the centre of our own Milky Way galaxy. Its orbital period is ten years and it lies around three times further from its parent as we do from the Sun.

Yep. Thats Earth-like allright.  

[Night Hammer]

yeah but dont red dwarves prouduce more heat or radiation or somthin?

[Shade]

Not really, they're just very small stars where, because of their small size and thereby comparatively low pressure, the nuclear reactions take place at a much slower rate than on larger stars. So they are colder and dimmer across the spectrum than a star like out own sun.

Given this and the quoted orbital distance of about 3 AUs, that's likely to be one cold planet.

[Wanderer]

Whats wrong with that? Surface temperature estimated to be nice - 220 degrees C and if it has atmosphere... well of what? Methane? nope, too cold... Ammonia? Waay too cold... Nitrogen? marginally. but too cold again, though there could perhaps be liquid nitrogen.. Oxygen could fit but it doesnt appear in known nature as free without life and is far too reactive anyway..

And some red dwarfs (spectral type M stars) are flare stars but not all..

[aldo_14]

http://news.bbc.co.uk/1/hi/sci/tech/4647142.stm

BBC story.

I believe it's termed earth-like if it possesses an atmosphere and an approximate mass (presumably the range of mass is rather flexible as IIRC this is 5 times Earths' size)

[Wanderer]

It says 5 times the size and as the planet is much further away from the star than the 'snow line' distance it is most likely has much lower density than the Earth. So 5 times the size might still have roughly equal or even lower mass.

And IIRC 'earthlike' or 'terrestrial' = rocky planet with alternative being 'jovian' planet or in other words gas giant. Usage is a bit random though..

EDIT: Snow line = where volatile compounds condense - > causes supposedly larger but less dense planets

[DeepSpace9er]

Why dont these scientists just say that they are guessing and they dont know. They never actually did see the planet, just detected its gravity effects.

[karajorma]

So what do you want them to say? We found something that has the gravitational pull of a planet and is where we might expect to find a planet but could actually be the 3rd Deathstar?

[aldo_14]

So what do you want them to say? We found something that has the gravitational pull of a planet and is where we might expect to find a planet but could actually be the 3rd Deathstar?

"We saw a thing"
"what thing?"
"Not sure.  We can guess, though, based on sensible scientific calculations."
"And what would you guess?"
"Can't say - we don't have pictures."