Billions of Planets In Milky Way?

jeffsenter writes, "The Washington Post has the story: 'NASA scientists using the Hubble Space Telescope have discovered what they believe are 16 new planets deep in the Milky Way, leading them to conclude there are probably billions of planets spread throughout the galaxy.' What sets these potential planets apart is they are in the central bulge of the Milky Way where most stars are located. More planets in the galaxy means more chances for life." The 16 are planet candidates at this point, until verified by spectroscopic measurement of their parent stars' wobbles, which probably can't be done until the James Webb Space Telescope files in 2013.

Comments

Re:Good ol' hubble

[AsmCoder8088]

There are some advantages to ground-based scopes versus ones such as the Hubble. For instance, you can get a great deal more sensitivity on the ground than in space simply due to the fact that the aperture of the primary mirror can be made much larger for a ground scope than a space scope. The reason behind this is cost - it is far more expensive to put a large mirror in space than on the ground. However, since it is in space, the smaller mirror does have better resolution. So it is simply a trade-off between sensitivity and resolution. With greater sensitivity, you can pull in fainter objects, but with better resolution, you can differentiate more easily between distance objects.

This is a great example of a ground-based telescope that could easily rival any space telescope:

OWL Telescope

Re:Billions of *Jupiter sized* gas giants

[dgatwood]

Assuming we don't kill ourselves before our sun fails catastrophically:

• The viable lifespan of our sun: 9.2 billion years (main sequence)
• The period during which Earth has had life: 3.8bn + 4.6bn = 8.4 billion years
• Period of human existence: 2 million + 4.6bn ~= 4.6 billion years
• Probability of intelligent life: ~50%

What remains to be determined are:

• Number of stars with rocky planets.
• Average number of rocky planets per star with rocky planets.
• Percentage of rocky planets within band where life is expected (currently speculated to be 0.958 AU +/- 0.023 AU out of about 40 AU to Pluto, so about 1/869.565217)
• Number of rocky planets in this band with the proper chemical makeup for life to begin (presumed to be nearly all of them, but...)

So from this, a good guess might be 1/1700 of the rocky planets out there are habitable. If our solar system is typical, we have 5 rocky planets, so there would be a (1 - (1699/1700)*(1699/1700)*(1699/1700)*(1699/1700)*(1 699/1700)) or chance of our solar system evolving any life at all, or about 0.29%. Multiply times the odds of a habitable planet having intelligent life at any given time (about 1/2), and we have about a 0.145% chance (only a little better than 1/1000) of finding intelligent life in a solar system with rocky planets.

Nowhere near the 1 in a million long shot speculated, but this assumes that Earth is typical, which is not necessarily a valid assumption.

Re:Good ol' hubble

[Pooua]

Spinning liquids to form mirrors works on Earth because Earth's gravity acts perpendicular to the plane of spin. We would need some way of replicating those two forces in space. All the methods I know about would cost more than simply launching a solid mirror.

A method of putting cheap mirrors into space that I proposed to my physics mentor a few decades ago is to use inflatable mirrors. He brushed off the idea at the time. Now, though, NASA has research on the general concept:

NASA Tech: Parabolic Membrane-Thickness Variation for Inflatable Mirror

A Google search for inflatable mirrors turns up many more results.