Smallest known exoplanet may actually be Earth-mass


Cool news recently in New Scientist: the hitherto smallest known planet around a star other than the Sun may be even smaller than first thought.

Initially, the team that discovered the planet–the oh-so-cleverly-named MOA-2007-BLG-192-L b–believed that the planet’s host star was a brown dwarf, a class of objects too puny to sustain nuclear fusion, as normal stars do. That suggested MOA-2007-BLG-192-L b weighed 3.3 Earths.

But now, after more recent observations and some recalculation, the team believes the parent star is actually a red dwarf, and thus heavier than first thought (those pesky dwarfs with all their confusing colours…)

The implication is that if the star is heavier then the planet is lighter: significantly so, in fact, weighing in at around a mere 1.4 Earths. In size terms, that makes it a near twin of our own planet, closer in mass than any known planet except Venus.

So good news: we’ve found a planet much closer in size to Earth than other exoplanets we’ve found to date.

But bad news: it’s still around 3000 light years from Earth, made mostly of rock and ice, and if it has any sort of atmosphere it’s likely to be composed primarily of hydrogen. So if we do somehow discover FTL and ever get there no smoking, okay?

More details can be found here.

– S.

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2 Responses to Smallest known exoplanet may actually be Earth-mass

  1. Anonymous

    Hi Stephen,

    I came across an old blog of yours with a link to Saturn in G Minor but it doesn’t seem to work.

    Do you have a new link somewhere on your blog where I can view the story?

  2. Hi Anon –

    I’d posted the story for a month or so last year when it was nominated for Canada’s Prix Aurora Award so that voters could read it for themselves, but I have no plans to put it online again.

    If you’d like to read the story why not pick up a copy of WRITERS OF THE FUTURE XXIII? It’s still available and is full of 12 fantastic stories by some amazing new writers–it was a privilege to be counted amongst them.

    Best wishes,

    – S.

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