11th Jan. 2012 ::
The ExoPlanet Count is Likely to Reach Trillions
Through various means, astronomers have now confirmed over 700 exoplanets. In addition, there are nearly two and a half thousand more candidates awaiting observational confirmation - confirmation that will more than likely come for the overwhelming majority.
The Kepler mission
[1] is of course leading the way, with it's precise optics operating with the benefit of an unobstructed heliocentric orbit, and outside of our flickering atmosphere.
Kepler is now reporting tiny planets as well as the larger mulit-Jupiter mass planets. Just today the Kepler team has announced three planets all orbiting the same star with radii of just 60% to 80% that of the radius of Earth
[2], making the smallest of them similar in size to Mars.
New Kepler planet relative sizes.
Image: NASA/ Kelper
Meanwhile, as Kepler has been stealing headlines, a lesser known search for exoplanets has been in progress. A small international team has been using a technique called gravitational lensing to conduct a 6 year survey of millions of stars.
Tomorrow, in the journal Nature they will announce that their observations indicate that "
planets are more common than stars"
[3]. Microlensing requires a very rare chance alignment of a background and lensing star for an event to be detected. In addition, to spot a planet during the lensing event, an additional chance alignment of the planet's orbit is also needed, putting the planet between the two stars and in alignment with the earth bound observer. These unlikely requirements mean that any such detections can only be put down to one of two things; either sheer blinding good luck, or (more likely of course) a statistical likelihood from the fact that there are an awful lot of planets.
Daniel Kubas, co-lead author of the paper explains: "We used to think that the Earth might be unique in our galaxy. But now it seems that there are literally billions of planets with masses similar to Earth orbiting stars in the Milky Way"
Of course, if we consider that there are perhaps somewhere in the region 100 billion galaxies in the observable universe - as of today, and this announcement - it looks more likely than ever that there are (will be, and have been) thousands of trillions of planets. And perhaps billions of Earths!
Some of the sunsets and some of the sunrises must be spectacular! Such an amazing wonder to live in a time when these discoveries are being made - our understanding of the Universe is truly growing daily. And yet, such a shame to live in a time when these types of view live only in the imagination...
[1]
http://kepler.nasa.gov/
[2]
http://planetquest.jpl.nasa.gov/news/tiny_trio
[3]
http://www.nature.com/nature/journal/v481/n7380/full/nature10684.html
