A fish story worth listening to

When I was a junior astronomy nut between the ages of about 10 and 12, the innumerable books on the subject I checked out of the Concord (N.H.) Public Library all included confident claims that, one day, we would find planets orbiting stars other than our own. It was simply inevitable based on statistical principles alone, unless one bought into the idea that the Earth really was of divine provenance. (Astronomers in particular, hearkening to the travails of Galileo Galilei, had little use for that idea.)
Although I wanted to see this prediction realized tomorrow, I figured that, between the ongoing basic game efforts of observatory drones and the ever-increasing power of optical telescopes, I would at least live to see it.
That day is here, and the already iconic image courtesy of the Hubble telescope leaves no doubt.
Fomalhaut__b.jpg
If you want the real skydirt, skip this drivel and read Steinn Sigurðsson’s post. My less technical and far less informed treatise follows.


The planet was discovered orbiting the star Fomalhaut in the constellation Piscis Austrinis (“Southern Fish”). Fomalhaut appears as the 17th-brightest star in the night sky, but this is owed more to its proximity than its luminosity: At a distance of 25 light-years, only a comparative smattering of stars lie nearer. It is a young star–perhaps 200 to 300 million years–and so glows white, making it a class A star in the Hertzsprung-Russell classification. It is about twice as massive as our sun; this is likely a necessary condition for a star to have planets, since the real big ‘uns are older and have probably expanded far beyond their original reach, thus engulfing whatever may have been close enough to achieve a gravitationally stable orbit.
So, it makes perfect sense that the first planet caught on film outside our solar system would be both smallish (so as not to have eaten its young) and close to us (so we can see the damned thing).
The planet, about 120 times as far from its star as Earth is from Sol, has been termed Fomalhaut b. Normally, astronomers are much more whimsical with their nomenclature, but there’s still hope. Hell, since Fomalhaut means “mouth of the whale,” why not Jonah? Yeah, we’ll roll with that. Jonah is Jupiter-like in mass, thus presumably mostly gaseous in composition.
One final, interesting note: With Pluto’s dolorous declassification last year, the discovery of Jonah brings the total number of known planets in the universe back to the familiar nine. But how long are we likely to have to wait to catch on film what we know owing to things such as stellar “wobbles” as well as the odds is there, moving us into double digits?

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  1. #1 by llewelly on November 15, 2008 - 1:46 am

    9 planets? Why are you discounting the 3 planets imaged by the Keck observatory, which orbit HR 8799 (only 130 ly away), and 326 or so extrasolar planets confirmed by means other than direct imaging?

    It’s not as if any of them are dwarf planets or plutinos!

  2. #2 by eddie on November 15, 2008 - 9:35 am

    25 ly?!
    That means they could be tuning in to new duran duran on the radio, and launching their nukes appropriately.

  3. #3 by Pierce R. Butler on November 15, 2008 - 10:55 am

    Why not name Fomalhaut b “Baleen”? or “Ahab”?

  4. #4 by Kevin Beck on November 16, 2008 - 12:39 am

    “That means they could be tuning in to new duran duran on the radio, and launching their nukes appropriately.”
    Easily the funniest fucking response to anything I’ve read here, or anywhere, in a long time. Please keep commenting,
    llewelly–I wasn’t aware that the Keck collection clearly documented planets, but I’m happy to be in error.

  5. #5 by Jinchi on November 16, 2008 - 10:24 am

    It is about twice as massive as our sun; this is likely a necessary condition for a star to have planets, since the real big ‘uns are older and have probably expanded far beyond their original reach
    A star has to be twice as massive as our sun to have planets?
    I think you lost something in your editing, because none of that sentence makes sense. Both red dwarves and blue giants can have planets, and our sun will likely have most of its planets after it expands into a red giant several billion years from now.

  6. #6 by Kevin Beck on November 16, 2008 - 11:18 am

    “I think you lost something in your editing”
    That’s being generous; I probably lost a lot in my chain of overall knowledge. More to the point, I oversimplified. I often ignore the fact that most of my readers know more than I do about the things I write about, but am happy for the repercussions.
    I would think that in order for us to be able to detect planets from Earth, the parent stars in question would more or less have to match the characteristics of a smallish star in a stable thermonuclear state, and be close by. If intrinsically megaluminous but distant stars like Rigel or Capella had planets, it would be impossible, given the constraints of current technology, to find them. Does that make sense?

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