A matter of mistaken mass?

Seemingly, everyone’s a bit uncertain about a star named MOA-2007-BLG-192L. It’s known to have a planet in tow, and everyone agrees that it’s a small planet, but exactly how small seems to be a contentious issue.

The planet was originally reported in 2008 as weighing a mere 3.3 Earth masses, making one of the lightest planets discovered. The caveat was that its host star was a feeble brown dwarf. At a distance of around 0.6 AU, that would be a fairly cold planet.

However, New Scientist (amongst others) caused a stir by reporting findings that it’s only a mere 1.4 Earth masses, and that the host star is in fact a red dwarf. That might still be too cold for any prospective life there, but on the other hand, it would be the first planet with an Earth-like mass discovered around a main sequence star*.

As it happens, that might not be entirely accurate. If the star is a red dwarf, then it might be 1.4 Earth masses. For now, I guess, we’ll just have to sit tight and wait for them to confirm the masses of the two objects. Only then will we be able to say if we have indeed found a true terrestrial planet…

Either way, whether it’s 3.3 or 1.4 Earth masses, it’s still an impressively small world to have discovered. Gravitational microlensing is evidently a rather powerful tool in the planet hunters arsenal.

*For the record, much smaller planets (including one that could actually be a comet) have been found around pulsars. For some reason everyone always forgets about those when discussing exoplanets…

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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