The list of known planets outside our solar system has grown a little, with the announcement of Wasp 3, Wasp 4 and Wasp 5. These three planets orbit so close to their stars that their years are all less than two days and they have surface temperatures of over 2,000oC, as reported by the UK’s BBC, Times, Guardian. All three planets will be officially unveiled at a conference in China this week (Telegraph).
Just to make sure we weren’t getting the wrong end of the stick I put in a very quick call to one of the researchers to check these years were two Earth days, and not two days on the planets themselves. And this is where it gets a little more complicated and a lot more interesting…
The Wide Angle Search for Planets (hence WASP) project finds planets by monitoring up to 400,000 stars every minute and looking for the ‘blink’ in light as a planet passes in front. This is a pretty standard technique and has contributed to there now being over 200 extra-solar planets on our books (see the Extrasolar Planets Encyclopaedia). This is as far as most of the news coverage out there goes.
After confirming with Pierre Maxted, one of the researchers from Keele University, that the planets did indeed orbit their stars in two of our days the next obvious question is how long are their actual days, ie one rotation. According to Maxted you can’t really measure this but it’s likely that tidal effects lock the planets so one side always faces the sun, much like our Moon facing us.
The next obvious question (or – if you’re me the question that only occurs after you have hung up, necessitating another call) is where does this 2,000oC surface temperature come from? Surely the side facing the sun all the time would be much hotter than the back side? Well, kind of: Maxted says these new Jupiter-like planets are more examples of the strangely “puffed up” planets previously detected (on this see the Guardian and New Scientist’s previous take on the WASP project).
Not all the measurements are clear at the moment but at least one of the planets appears to have a fairly uniform temperature. And the puffed up planet mystery – which is much more interesting than just a new planet – continues.
The planets were detected by researchers from three universities: Queen’s in Belfast, Northern Ireland; St Andrews in Scotland; Keele in England (press releases: Queen’s, Keele, St Andrews). There is local paper coverage from Belfast’s Telegraph and BBC Northern Ireland has a nice piece on the WASP project.
Image: artist’s impression of extra-solar planet