A wobbly star!

I remember reading an article when I was just a kid called “The Hunt for Wobbling Stars”. I can’t have been much more than 8 years old, but the concept seemed simple enough even then. Any planet tugs on a star as it orbits it. So finding planets should be as easy as watching for the star to wobble in the sky. Simple, right? Well, apparently not…

Astrometry is the art of carefully tracking the motion of a star in the sky. With enough precision, you should be able to spot the tiny deviations that a planet’s gravity will cause. I won’t go into details, but it’s all about celestial mechanics and extreme accuracy. The thing is, the concept was first attempted about 50 years ago, but it’s only now that astronomers have finally found a planet this way. And it took a group of NASA scientists 9 years to do it. In the UK, that’s about 3 generations worth of PhD students!

So, lying around 20 light years from us in the constellation of Aquilla (The Eagle), is a miniscule red dwarf star named VB10. Fantastically enough, it has a companion planet, systematicaly named VB10b. A hulking gas giant 6 times the size of Jupiter in an orbit comparable to Mercury’s in our own solar system. This image shows a comparison (click it to be taken to a larger image and a full caption). That seems close until you consider how tiny VB10 is. And it’s really tiny! Actually, for a long time, it was the smallest star we’d found in the galaxy. Under a twelfth the mass of the Sun, it’s close to the lower limit for how small a star would be. Much smaller and it would be little more than a brown dwarf.

A star this tiny doesn’t give out much heat, so despite a Mercurial orbit, this gas giant is thought to be closer to our own Jupiter in temperature. The NASA press release conjectures though that being a gas giant, it might be somewhat Earth-like in temperature. That seems fair to me. After all, we know that our friendly neighbourhood gasballs all seem to have an internal energy source keeping them warm.

They also conjecture that any more Earth-like rocky planets might lie even closer to the host star. A miniature solar system, if you will. That rather implies that there’s a slim (but non-zero) chance of finding a planet in a habitable zone, if not around this star then around another similar one. Of course, whether or not red dwarfs are habitable is still a matter of open debate.

One thing’s for certain though. The more we learn about planets, the more we’re realising how ubiquitous they really are in the Galaxy!

The NASA press release is available here, together with a little video explaining a bit more about the astrometry behind VB10b’s discovery.
Image credit: NASA JPL/Caltech.

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
This entry was posted in Imported from Livejournal and tagged , , , . Bookmark the permalink.

2 Responses to A wobbly star!

  1. invaderxan says:

    Re: Red dwarfs and planets
    I remember hearing about Van der Kamp, yeah… Just goes to show how tricky astrometry can be, I guess! Sadly, it seems, in most cases where nothing more is said, it’s because no one managed to verify the result (rather pivotal to getting a discovery accepted!). There’s always the chance that no one’s actually tried verifying the claim though…
    Pan-STARRS is more about Solar system objects, isn’t it though? I’m not sure about exoplanets, but I’m hoping it might find a couple of interesting Kuiper Belt objects! :)

  2. Anonymous says:

    Red dwarfs and planets
    Poor old Peter van der Kamp thought he’d bagged a few planets around Barnard’s Star – he had orbital solutions for about 5 planets in the end. Problem was no one else – no other telescope that is – could see the star-wobbles. Just van der Kamp’s telescope, so eventually the problem was tracked down to subtle oscillations in the tracking system.
    I’ve got to wonder what’s happened to the 2/3 planets around Lalande 21185 that George Gatewood and the Allegheny Observatory claimed to have spotted via astrometry in 1996. Nothing much has been mentioned about them since.
    The latest find, its data gathered with an eye to past problems, is solid – but astrometry takes so very long… Wish there was some way of speeding it up. I wonder if Pan-STARRS will add to the astrometry capture count?

Comments are closed.