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

Working on it!

[ThankfulJosh]

I work for the Shuttle program. The current plan is to send up a Hubble repair mission. Can't say when, but it's definitely planned.

Re:Billions of *Jupiter sized* gas giants

[IDontAgreeWithYou]

Until a few years ago we weren't sure that there were any other planets at all. Once astronomers figured out how to find these large planets, hundreds were discovered in short order. The implication is that planets are common and while we still can't detect earth-like planets, but it's certainly much easier to believe that they exist.

Re:Billions of *Jupiter sized* gas giants

[Squiffy]

Despite the fact that many people call the sun a "yellow dwarf" or an "average star", it's actually in the top 10%, by brightness. That also probably puts it in the top 10% by mass, radius, etc. Find the Gliese 3.0 catalog if you don't believe me.

Why James Webb ST?

[helioquake]

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.

A detection of Doppler motion due to planetary perturbation is miniscule. It could take an accuracy of less than one km/s, or more likely a few dozen meter per second. It is extremely hard to make a high resolution spectroscopic instrument for a space satellite to meet that criterion. Calibrating out all the uncertainties in the motion of the satellite would become an issue as well. That said, I don't think the James Webb ST would do much in this topic.

Besides, the designers for JWST don't strongly desire to have a spectrographic instrument on board the JWST. It may end up as a purely imaging mission, which is extremely boring for physicists.

The verification is better done with adaptive optics + Echelle grating at V, R or IR band from ground.

Only 8 planets...

[masnare]

Sorry guys, no matter what these people saw, there are only 8 planets -- not 16 -- and certainly not billions. From the IAU site:

RESOLUTION 5A The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:

(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

(emphasis mine)

The page goes on to list the eight planets:

The eight "planets" are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

I can't help but think it's a pretty stupid requirement, but it is what it is...