List of planets spotted outside our solar system now tops 500
It was only a little over a year ago that the , but time flies when you鈥檙e discovering exoplanets. The 19th of November 2010 marked the date that over 500 exoplanets had been confirmed on The Encyclopedia.
Though it鈥檚 an arbitrary number to celebrate, the fact that we鈥檝e confirmed the existence over 500 exoplanets since their initial 20 years ago is deserving of merriment. Discovery of exoplanets has really ramped up over the last few years, thanks in part to the ESA鈥檚 satellite, the Hubble and Spitzer , the Keck Interferometer, and the improvement of observational techniques to discover and confirm exoplanets. NASA鈥檚 has over 700 candidates for exoplanets. Only 7 planets have been confirmed after being discovered by the Kepler so far, though.
Jean Schneider, an astrobiologist at the Paris-Meudon Observatory, keeps up a of the confirmed exoplanetary discoveries at . He posted a warning about how muddle the declaration of 鈥渢he discovery of the 500th 鈥� could be. He wrote in the warning:
鈥淭he number of exoplanets, recored for instance at http://exoplanet.eu is necessarily subject to some uncertainty for several reasons:
- the mass limit below which a substellar object is called a is somewhat arbitrary
- the mass measurement is always affected by some instrumental inaccuracy
- whatever this mass limit is, the true mass for most planets is subject to some uncertainty, intrinsic to the detection method (unkown inclination of the , modelisation of planet )
- some planet detections, even published in refereed papers, are sometimes retracted afterwards
For all these reasons
1/ The boundary between 鈥渃onfirmed鈥�/鈥漸nconfirmed鈥� planets is somewhat fuzzy
2/ The number of planet candidates at http://exoplanet.eu ;(collected in the survey of professional litterature, conferences or websites) is affected by an uncertainty of a few units.鈥�
In essence, to say that there is a 鈥�500th exoplanet鈥� is really not possible, given that there needs to be confirmation of . Even after that confirmation, there could be the possible retraction of the planet from the database. 5 confirmations were posted on the 19th, all of them published in refereed papers and discovered in 2010. This kicked the total over 500. But then another was announced the next , and it was discovered in 2007 but only recently confirmed. So, putting a number on the 500th to be confirmed is pretty much impossible, arbitrary at best.
Schneider was interviewed by Scientific American on just why he is the keeper of the encyclopedia, and some of his thoughts on the discoveries made so far and the future of the field. The text of the interview is .
Complicating matters even further, there is another running tally of maintained by the NASA鈥檚 Jet Laboratory at . Their count on the 22nd of November was only 497, and today rests at 500. The Extrasolar Planets Encyclopedia now stands at 504.
PlanetQuest has this video that succinctly describes the history of extrasolar planet discovery, for those interested:
Even if it鈥檚 arbitrary, you can still have that 鈥�500th exoplanet鈥� party if you鈥檇 like, complete with Kepler satellite-shaped hats. Nobody will likely stop you; if they do, there will likely be another few dozen planets discovered 鈥� or a few retracted 鈥� by then anyways, making their point rather moot.
Source: , and
Nicholos Wethington blogs at .
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