Hubble discovers a hundred exoplanets??

[Jugalator]

http://news.bbc.co.uk/1/hi/sci/tech/3856401.stm

Cool quotes:

"If confirmed it would almost double the number of planets known to be circling other stars to about 230."

"The discovery will lend support to the idea that almost every sunlike star in our galaxy, and probably the Universe, is accompanied by planets."

Oh my...

How could it suddenly discover so many?

Have they started using new techniques of finding them or what... Or just pointed Hubble to a gold mine? Hmm...

[selden]

Jugulator,

Sahu's observations are based on the principle of gravitational microlensing.

I haven't found the report that the BBC references, but here's a description of his previous observations of a globular cluster. http://hubblesite.org/newscenter/newsdesk/archive/releases/2001/20/

The principle is the same: look at a large number of stars and watch for fluctuations in their light. Some will be caused by planets crossing the line of sight between us and a star. There are lots of stars in the field of view when Hubble points toward the center of the galaxy, so some of them are bound to have planetary orbits with the right alignment. Of course, the luminosity profiles have to be examined very carefully to separate out the different kinds of effects that cause fluctuations.

[Ynjevi]

Sahu's observations are based on the principle of gravitational microlensing.

No, they were found via transiting method.

Here:

A tiny decrease -- less than a tenth of 1 percent -- in the light was a sign that something, perhaps a planet, was passing in front of the star. A similar phenomenon entranced millions of earthlings when Venus transited the sun June 8.

[selden]

Ynjevi,

Please remember that newspaper science articles are triviailzed in order to be partially understandable by the non-scientific reader. The description there does not rule out gravitational microlensing. That also causes a decrease in light, although it's usually followed by a slignt increase.

We need to see a copy of the report written by the researchers in order to know exactly which techniques were used. So far I haven't found it.

[selden]

I haven't found a description of the results, but here's a copy of the preliminary research proposal: http://www.stsci.edu/observing/phase2-public/9750.pro

It just says they're looking for "transit events" without specifying the light profile. This suggests that both simple (light reducing) transits and microlensing effects would be detected.

[Ynjevi]

Please remember that newspaper science articles are triviailzed in order to be partially understandable by the non-scientific reader. The description there does not rule out gravitational microlensing. That also causes a decrease in light, although it's usually followed by a slignt increase.

Maybe, but aren't the microlensing stars too dim to be studied properly (with the radial velocity method for example) like is the case with OGLE 2003-BLG-235? And can hot Jupiters be detected with the microlensing technique? And if they orbit at some greater distance from the parent star RV confirmation takes time.

I found this from the Hubble Daily Reports (February-March 2004):

NICMOS 9750

The Galactic Bulge Deep Field: A Planetary Transit Survey and Very
Deep Stellar Mass Function

We propose to observe a Galactic bulge field continuously with ACS/WFC
over a 7-day period. We will monitor ~167, 000 F, G, and K dwarfs down
to V=23, in order to detect transits by orbiting Jovian planets. If
the frequency of "hot Jupiters" is similar to that in the solar
neighborhood, we will detect over 100 planets, more than doubling the
number of extrasolar planets known. For the brighter stars with
transits, we will confirm the planetary nature of the companions
through radial- velocity measurements using the 8-m VLT. We will
determine the metallicities of most of the planet-bearing stars as
well as a control sample, through follow-up VLT spectroscopy. The
metallicities of the target stars range over more than 1.5 dex,
allowing for a determination of the dependence of planet frequency
upon metallicity--a crucial element in understanding planet formation.
We will be able to discriminate between the equally numerous disk and
bulge stars via proper motions. Hence we will determine, for the first
time, the frequencies of planets in two entirely different stellar
populations. We will also determine for the first time the
distribution of planetary radii for extrasolar planets for both these
populations. Parallel observations with NICMOS will provide ultra-deep
near-infrared images of a nearby bulge field, which will be used to
determine the stellar luminosity and mass functions down to the
brown-dwarf regime. The data will also be useful for a variety of
spinoff projects, including a census of variable stars and of hot
white dwarfs in the bulge, and the metallicity distribution of bulge
dwarfs.

We need to see a copy of the report written by the researchers in order to know exactly which techniques were used. So far I haven't found it.

They probably release it after the RV measurements... Well, lets hope it won't take very long .

[Evil Dr Ganymede]

How would they know if they're looking at a transiting planet or a sunspot? Do they have the radial velocity profiles for these stars?

[selden]

They don't know yet. (See the project proposal quoted above.) They're planning to use the ESO's VLT in Chile for follow-up studies.

[Jugalator]

Ah, OK, so the flashy title "Hubble discovers 100 new planets" is stretching the truth a bit since they aren't 100% confirmed yet, and it's more like "planet candidates"? Hmm, I knew something fishy were going on...

But hopefully, as many as possible will actually be confirmed to be in the follow up studies then.

I soo much wish we would have better means of detecting these sneaky planets, and detecting more about their atmospheric compositions. It's probably the most fascinating field of space science to me right now, which makes this page one of my NASA favorites.