Exoplanets

[Neil]

What's the current count of exoplanets found. Is anyone keeping count?

[filrabat]

As of February 5,2005 - 136 are known.
http://exoplanets.org/

[scorpio711]

I have slightly different numbers (as of March 4th):
- 134 planetary systems
- 152 planets
- 14 multiple planet systems
from http://cfa-www.harvard.edu/planets/catalog.html

Scorpio

[nomadicdemon]

that's a lot of exoplanets, are any of them in our own solar system? Have we named these exoplanets or are they just out there? please answer my question

[scorpio711]

Mullet, by definition "exoplanet" stands for "extrasolar planet", that is, a planet orbiting around a start different than our sun.
These exoplanets don't have names, but bear the name of the stars around which they orbit, followed by a lowercase letter (starting with "b"). And within a same 'star system', they are denominated in their order of discovery. For example, 4 planets have been discovered orbiting around "55 cnc" (star 55 of constellation cancer), named "55 cnc e", "55 cnc b", "55 cnc c" and "55 cnc d".
Hope this helps,
Scorpio

[buzzlightbeer]

how do u determine which planets mite be earth-like - or have the potential to harvest life?

[astromark]

We do not yet have any Earth sized planets as confermed targets in the search for exoplanets. As our equipment becomes more sensative we might find Planets in the life zone of a size that might saport life as we know it. Its to early to tell just yet. I / We are confident that within fifty light years of Earth we will find earth like planets.

[Nyrath]

Originally posted by buzzlightbeer@Mar 11 2005, 04:08 AM
how do u determine which planets mite be earth-like - or have the potential to harvest life?

The question is currently moot, since all the planets detected to date are far too huge to be earth-like.

The main thing is for the planet to be approximately earth-sized, and at a distance where the planet is neither a frozen block of ice or an oven-like desert (technically called "being within the ecosphere" or "being with the habitable zone").

The planet also need large amounts of water, and it wouldn't hurt to have a sun of spectral class F, G, or K.

[filrabat]

Originally posted by Nyrath+Mar 11 2005, 04:39 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Nyrath &#064; Mar 11 2005, 04:39 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-buzzlightbeer@Mar 11 2005, 04:08 AM
how do u determine which planets mite be earth-like - or have the potential to harvest life?

The question is currently moot, since all the planets detected to date are far too huge to be earth-like.

The main thing is for the planet to be approximately earth-sized, and at a distance where the planet is neither a frozen block of ice or an oven-like desert (technically called "being within the ecosphere" or "being with the habitable zone").

The planet also need large amounts of water, and it wouldn&#39;t hurt to have a sun of spectral class F, G, or K. [/b][/quote]
Although it&#39;s plausible to speculate that, for those gas giants that are within the habitable zone, (whether liquid H20 or whatever else you may care to believe about exobiology) -- the larger moons of those planets might be have some form of life detectable from our solar system once we have the technology to detect O2, H2O, CO2 and N2 signatures of other planets .

[Guest_nicolii]

We must not forget the galactic region in which the planetary system is located. The frequency of planetary mass extinction events would occur with greater frequency closer to the galactic center. These consist of but are not limited to cometary belt perturbations, gamma ray bursts, and supernova, more hazardous simply because of the greater star density.

[Nereid]

Originally posted by buzzlightbeer@Mar 11 2005, 04:08 AM
how do u determine which planets mite be earth-like - or have the potential to harvest life?

There are several techniques used to determine the mass, size, and orbit of exoplanets - doppler, transits, astrometric ... the websites provided in earlier links also explain (in considerable detail) how each of these parameters is determined (or constrained).

Astrobiology is very young field of science, so theories are currently poorly constrained; it&#39;s also a very exciting field&#33; There&#39;s the opportunity to find ways to mix geophysics, biology, planetary science, and astrophysics to make very interesting theories and predictions. Too, techniques are advancing rapidly in their sensitivity and scope, so observational constraints may become quite interesting in as little as two decades*&#33;&#33;

*that&#39;s a very short time for a field of science.

[John L]

Originally posted by buzzlightbeer@Mar 10 2005, 10:08 PM
how do u determine which planets mite be earth-like - or have the potential to harvest life?

And I&#39;d like to add that we are currently designing future space based telescopes that will combine the light collected by multiple mirrors, some widely spaced, so that we can resolve the actual planets in their orbits. The hope is that we can measure the spectrum of light reflected off the individual planets to identify those with nitrogen/oxygen/carbon dioxide atmospheres that have ample water vapor. Find that combination and you&#39;ve probably found another Earth, full of life.

[Planetwatcher]

The planet also need large amounts of water, and it wouldn&#39;t hurt to have a sun of spectral class F, G, or K.

It would be prudent to explain the spectral classses to Mullet as he appears somewhat new to astronomy.

In a nutshell, and making all things equal, spectral class is the color and size a star according to spectrometer type observation equipment based on the approx. temperture and size of the star.

Red dwarf is the coolest of what we call main sequence stars. I won&#39;t get into non-main sequence varations here. Red dwarf has the spectral class of M.

Next is orange dwarf. It is larger and hotter then red dwarf, and also more stable in it&#39;s life cycle. They are known as K class stars. The larger of this class is where we begin to speculate the possibility of life development.

Yellow dwarf is next. Dubbed as G class. This is the catagory our Sun is in.

Yellow/white subgiant or giant are F class. These are the largest and hottest stars believed to have any possiblity of life.

White/blue giant stars are in the A class. Their lives are much shorter then the others, and they put out too much radiation to harber life in what would otherwise be the safe zone.

Blue giants are the B class.

Finally the super-giants and hypergiants are known as O class. Those are the largest stars known. If our Sun were an O class star, everything out to past Saturn would be inside the star itself. Uranus and Neptune would boil away, and even Pluto and Sedna would be cinders much like Mercury is now.

[filrabat]

I elaborated on the star class matter at this post:

http://www.universetoday.com/forum/index.p...t=0&#entry57903