Recently the International Astronomical Union decided that planets might start getting named after things. Previously they’d been given a lower-case letter after the name of their host star. Now they could get other names, something that inspired this memorable XKCD cartoon.
Well it turns out some of the planets aren’t terribly happy about the prospect too. In-fact Gliese 581d is pretty miserable about the idea of getting a dull or bizarre name, especially if you decide to name it after your cat, Colin. Gl 581d is a planet that’s a bit more massive than the Earth orbiting a faint, red star in the constellation of Libra. It might have a temperature that means it isn’t too hot or too cold to have liquid water (the so-called “Goldilocks zone“). This means it might have life. All it wants is to get a nice mythical name like the planets in the Solar System, preferably Norse but any pantheon would do. It really doesn’t want to be called after a celebrity or your mum or Permadeath, just a nice normal, mythical name. It’s been bombarded by comets for a billion years so don’t you think it deserves a break?
Be careful however, there are some mythical names are a bad choice, particularly Vulcan. This was a planet proposed around the Sun to explain the unusual orbit of Mercury. However it wasn’t there, the change in Mercury’s orbit was due to a subtle gravitation effect that wasn’t properly understood until Einstein came along with his theory of General Relativity.
Sometimes people have named stars for monetary or patriotic reasons like Herschel originally naming Uranus “George’s Star” after the British king at the time, so steer clear of that. Also a lot of asteroids have unusual names like Moomintroll, and it isn’t keen on that either. So please give a planet a break and name it something sensible.
Thanks to @ruthangus for doing the drawing, @emilulu and Russ for helping record this at AMNH, @astrodrian for lending me his guitar, @noisyastronomer for her camera and to .astronomy and the NERD Centre. The video was partly inspired by “Hey There Andy Murray” by Far-In Jim.
The audio file is also on Soundcloud.
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Ok, so you’re young, you’re surprisingly dusty, and you don’t match the models. No, not a picture of my geeky childhood, but the extrasolar planet HR 8799b. It orbits the star HR 8799 and, along with its two companions, is one of the two extrasolar planetary systems to be directly imaged, as shown above. Unsurprisingly it’s the dot labelled ‘b’.
If directly imaging extrasolar planets is hard (because they are so much fainter than their host stars), then taking spectra of them to study the composition of their atmospheres is, well, harder. This is just what astronomers at the University of Hawaii have managed to do for HR 8799b however, using the adaptive optics system on the Keck Telescope. To quote Trent Dupuy, one of the co-authors on the paper (from their handy press release),
Adaptive optics systems on Keck and other large ground-based telescopes make sharper images than even the Hubble Space Telescope. With adaptive optics, we are learning an incredible amount about objects that are smaller than the lowest-mass stars and larger than the most massive gas-giant planets in our solar system.
When they analysed their data they found little or no methane, which, since the amount of this gas can be used as a thermometer, meant that the planet is ~1200 Kelvin; this is ~400 Kelvin warmer than its predicted to be by the current best theoretical models. This, they think, is because it has more dust and clouds in its atmosphere than expected.
In related news, in a totally different part of the Galaxy, two more groups of astronomers (in Exeter and Florida) have also been taking spectra of two other extrasolar planets – HD 80606 b and XO-2b, this time using the Gran Telescopio Canarias. In these cases however, their big result is the first detection of potassium in their atmospheres, a result that this time was just what the modellers were expecting.
This is an exciting time for exoplanet work. The data are finally catching up with the models and, as usual some things match well, and some things raise more questions than they answer. Clearly, there are fun times ahead!
Brendan P. Bowler, Michael C. Liu, Trent J. Dupuy, Michael C. Cushing (2010). Near-Infrared Spectroscopy of the Extrasolar Planet HR 8799 b accepted by ApJ : 1008.4582
Knicole D. Colon, Eric B. Ford, Seth Redfield, Jonathan J. Fortney, Megan Shabram, Hans J. Deeg, & Suvrath Mahadevan (2010). Probing potassium in the atmosphere of HD 80606b with tunable filter
transit spectrophotometry from the Gran Telescopio Canarias submitted to MNRAS arXiv: 1008.4800v1
D. K. Sing, J.-M. Desert, J. J. Fortney, A. Lecavelier des Etangs, G. E. Ballester, J. Cepa, D. Ehrenreich, M. Lopez-Morales, F. Pont, M. Shabram, A. Vidal-Madjar (2010). GTC OSIRIS Transiting Exoplanet Atmospheric Survey: Detection of potassium in XO-2b from spectrophotometry submitted to A&A : 1008.4795