February 20, 2008

Possibly over Two billion earths in the Milky Way

(Hat tip Bad Astronomy), About 1% of the stars in the Milky Way could have earth like planets (smaller rock like planets) Another study shows the Milky Way is twice as big as previously thought. So instead 100 billion stars there could be 200 billion and of those 1% or two billion could have earth like worlds around sun like stars. Centauri Dreams also has coverage of the earth like worlds study

A Spitzer Space Telescope study found that 10-20% of young stars had these disks of dusty debris around them. As it happens, about 10% of the stars in the Milky Way can be categorized as sun-like, which is about 10 billion stars. If 10% of them have rocky planets, as this study indicates, then there may be a billion Earths orbiting stars in our galaxy alone! And that’s only for stars like the Sun; lower mass stars also can form planetary systems, and there are far more of them then stars like the Sun. It is entirely possible that there are many billions of terrestrial planets in the galaxy… and there are hundreds of billions of galaxies in the Universe.

Up to 62 percent of the surveyed stars have formed, or may be forming, planets. The correct answer probably lies somewhere between the pessimistic case of less than 20 percent and optimistic case of more than 60 percent.

In separate but related news, the Milky way galaxy is twice as big as previously thought

Astrophysicist Professor Bryan Gaensler led a team that has found that our galaxy - a flattened spiral about 100,000 light years across - is 12,000 light years thick, not the 6,000 light years that had been previously thought.

The University of Sydney team's analysis differs from previous calculations because they were more discerning with their data selection. "We used data from pulsars: stars that flash with a regular pulse," Professor Gaensler explains. "As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down.

"If you know the distance to the pulsar accurately, then you can work out how dense the WIM is and where it stops - in other words where the Galaxy's edge is.

"Of the thousands of pulsars known in and around our Galaxy, only about 60 have really well known distances. But to measure the thickness of the Milky Way we need to focus only on those that are sitting above or below the main part of the Galaxy; it turns out that pulsars embedded in the main disk of the Milky Way don't give us useful information."

Choosing only the pulsars well above or below us cuts the number of measurements by a factor of three, but it is precisely this rejection of data points that makes The University of Sydney's analysis different from previous work.


Lobo7922 said...

And where are they?
That is the classic question of the Fermi Paradox, if there are so many chances of life and inteligence to develop, why we havent found any other inteligent creature in the universe?
Where are their Dyson spheres and their Bracewell probes? :)

bw said...

My view on that is that we will have to look harder to get the universe to provide answers. Make hypertelescopes over the next few decades to image millions of worlds and see what is going on. Then if there is still a mystery to send probes and then to physically go to all of the planets. There are not many good answers from the current theory of a fermi paradox == naval gazing.

My personal guess is that if there are a lot of other civilizations then ours is not that interesting and we have no idea what to look for. What we think is natural phenomena might not be.

Lobo7922 said...

Then we are alone.
Perhaps they are out there but they havent develop a technology as ours yet, that means, we are alone.
Perhaps they are a Jack Vance's like Aliens "almost-inteligent" if they are inteligent as Gorillas or inteligent as Dolphins, we are alone too.
Or perhaps we should ask, where are OUR Dyson Spheres and Bracewell probes?
If we havent the time or the resources to show our existence to the other inteligent beings in the galaxy, why should we expect them to?