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originally posted by: tanka418
This afternoon I was researching the confirmed Exoplanets, to get a feel for the length of planetary periods. I'm developing WEASA - WolfMagick Exoplanet Adaptive Search Algorithm. ...I'll talk about that technology later on the observatories thread.
The average period of an extra solar planet is on the order of 723 days, a bit less than two years
Over 730 days: 212 10.62%
365 – 730: 109 5.46%
270 – 364: 42 2.10%
180 – 270: 45 2.25%
90 – 180: 80 4.0%
1 – 90: 1331 66.68%
0 – 1: 13 0.65%
Its a bit interesting that most 66.68%, 2/3 of exoplanets are close in and fast moving with a period less than 90 days. While the average is still at 723 days, but those 212 slow planets can be rather slow...
I still have to do more analysis on the 1 - 90 day period planets...
Of the slow planets the average period is 5717.72 days. This average is inflated like this due to 2 planers; 1) HR8799b at 164250 days, and 2) Fomalhautb at 320000 days.
originally posted by: JadeStar
You also have to consider tanka, the selection bias of various exoplanet detection techniques.
For instance radial velocity and transit photometric searches both require the planet to make several orbits around it's star before it is confirmed as real.
So the bias here is towards planets which orbit close to their star as they make more frequent transits.
There's also the bias due to the amount of planets around red dwarfs, the most common type of star in the universe. Planets around these stars are interesting because they can have more frequent transits yet exist in the stars habitable zone. And on top of this, because the star they orbit is dimmer they are easier seen in transit searches and are more sought after as potential future targets for direct imaging space telescope missions.
So yeah, never forget selection bias.
originally posted by: DragonsDemesne
It is true that most discovered exoplanets are large and quite near their own suns, because the method used to detect them works best on this exact type of planet. Still, it is interesting to me how we have found lots of big planets, both earth-like and gas-like, very near their suns, when in our own solar system, we have four earth-like planets nearer the sun, and four gas-like planets farther out. I'm not sure what implications this has for things like how solar systems and planets are formed, but I do find it interesting that we have found solar systems that differ dramatically from our own in this manner. It's impossible to know what the most 'common' type of solar system is without more data because, as was said, the data is biased due to the method of detection, but I hope we'll learn someday!