Question: how many planets are known now in space by humens
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Lots. No idea how many but lots and the number keeps going up as astronomers continue to look out into space. Best check with NASA or an astronomer for the number.
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Hi students and H-zone scientists,
The current tally is 563 planets outside the solar system. You can get up-to-date information from the online Extrasolar Planets Encyclopaedia here: http://exoplanet.eu/
Hi Matt and others,
There are two other methods for detecting exoplanets (other than the radial velocity method Matt talks about) that are becoming increasingly important: “transit”, where you look for planets passing in front of a star and dimming its light; and “gravitational microlensing” where you look for the effect of the planet on the gravitational bending of light by the star-planet system.
And the days of “hot Jupiters” are coming to an end — the hunt is on for terrestrial planets! Nature News did some feature articles a few months ago: http://www.nature.com/news/specials/exoplanets/index.html
Edward
There are 8 planets in our solar system (orbiting the sun) but over 500 planets have been found outside our solar system! It is likely that even more will be found as our space-scanning technology gets more advanced. Not much is know about these other planets as they are very far away, so maybe some of them could be home to extraterrestrial creatures!
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Aimee’s right. There’s a lot. More each week.
New planets are found by quite a crude technique. You watch a distant star and you see if it’s wobbling from side to side on like a month/year timescale. The movement is TINY but we can see it. If you see the wobble it’s probably because there’s a great big planet orbiting the star.
Now the problem with that is that to see the effect the planet has to be BIG. Really big. Like Jupiter big. Sadly those are the planets that are unlikely to support life. Most of the planets we see are like that. You then kind of assume that if there are big planets, there will be small ones that might support life. So far we’ve not directly seen an Earth-sized planet. With better, more accurate telescopes and better techniques at analysing what we’re looking at I bet we will soon, though.
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what more can I say?
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