http://www.nature.com/nature/journal/v441/...ature04828.html
Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called 'hot Neptunes' or 'super-Earths' around Sun-like stars. These planets have masses 5–20 times larger than the Earth and are mainly found on close-in orbits with periods of 2–15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun–Earth distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star.

Here is a story about a new solar system discovery. The system features 3 Neptune size planets and an asteroid belt. The middle of the three Neptune sized planets falls in the "liquid water" range. I imagine that the chances that this planet has a moon capable of supporting life as we know it are pretty decent. Or, since all three Neptune-sized planets are apparently rocky and not gasous, life capable of handling higher gravity than we do might exist on the planet in the habitable zone. Interesting!

merged duplicate topics

Using the ultra-precise HARPS spectrograph on ESO's 3.6-m telescope at La Silla
(Chile), a team of European astronomers have discovered that a nearby star is
host to three Neptune-mass planets. The innermost planet is most probably rocky,
while the outermost is the first known Neptune-mass planet to reside in the
habitable zone. This unique system is likely further enriched by an asteroid
belt. With three roughly equal-mass planets, one being in the habitable zone,
and an asteroid belt, this planetary system shares many properties with our own
solar system.

Read further ESO 18/06 at

http://www.eso.org/outreach/press-rel/pr-2006/pr-18-06.html

A rocky planet the size of Neptune... I wonder how it may look like. Probably very volcanic, with a lot of unusual volcanic materials on its surface, like sulphur. Or a Venus-like atmosphere. But we can only imagine for now.

While these planets themselves may not harbor life, I wonder about
any moons circling them?

The potential for tidally heated icy and temperate moons around exoplanets

Authors: Caleb A. Scharf

Comments: 28 pages, 8 Figures, AASTex, Accepted for publication in the Astrophysical Journal

http://arxiv.org/abs/astro-ph/0604413

The HST will not be outdone by the ESO:

PRESS RELEASE NO.: STScI-PR06-22

ASTRONOMERS USE INNOVATIVE TECHNIQUE TO FIND EXTRASOLAR PLANET

An international team of professional and amateur astronomers, using
simple off-the-shelf equipment to trawl the skies for planets outside
our solar system, has hauled in its first "catch." The astronomers
discovered a Jupiter-sized planet orbiting a Sun-like star 600
light-years from Earth in the constellation Corona Borealis. The team,
led by Peter McCullough of the Space Telescope Science Institute in
Baltimore, Md., includes four amateur astronomers from North America and
Europe.

This artist's impression shows a dramatic close-up of the extrasolar planet, called XO-1b, passing in front of a Sun-like star 600 light-years from Earth. The Jupiter-sized planet is in a tight four-day orbit around the star.

To see and read more about this research on the Web, visit:

http://hubblesite.org/news/2006/22
http://mcdonaldobservatory.org/news/
http://media.rice.edu/media/Default.asp
http://www.bu.edu/phpbin/news/releases/browse.php
http://www.ifa.hawaii.edu/info/press-releases/

I think this is 192 planet so far. Soon we shall have reached 200 mark

The official paper:

A Transiting Planet of a Sun-like Star

Authors: P. R. McCullough, J. E. Stys, Jeff A. Valenti, C. M. Johns-Krull, K. A. Janes, J. N. Heasley, B. A. Bye, C. Dodd, S. W. Fleming, A. Pinnick, R. Bissinger, B. L. Gary, P. J. Howell, T. Vanmunster

Comments: 31 pages, 9 figures, accepted for part 1 of ApJ

http://arxiv.org/abs/astro-ph/0605414

Well, hmm... depending on the age of the planetary system, any such moon of a Neptune-mass planet within the habitable belt of a star would have to share certain properties with Earth (enough mass to hold on to an atmosphere, liquid water on the surface, a magnetic field to protect the planet from both the solar wind and the primary's radiation belts, etc.) such that life could develop.

As long as all of those conditions exist, I don't see why life couldn't develop on such moons.

Of course, the star-wiggle technique will likely never be able to identify Earth-sized moons of hot Jupiters or hot Neptunes (or even temperate versions of similarly-massed planets). So we'll need SIM and TPF to get even the first clue as to how many of those there might be out there.

-the other Doug

Kepler may have some ability to detect them if they're big enough -- and even to detect major giant-planet ring systems like Saturn's. You'll have to crunch the data for a considerable period to confirm this firmly, though.

There has been at least one recent study of how likely it is that giant planets could retain their moons against the growing tidal tuggings of the central star while migrating into the inner part of their solar systems, and it was rather encouraging. I'll *sigh* try to track it down in my records...

Just a minor nit-pick. Solar System refers to the 'Sol' system, our own stomping ground. For clarity and to name the things correctly it should be extrasolar system or refered to by the name of the system star.

Three issues that come right out of my head.
Magnetic field IIRC could strip the atmosphere.
Also IIRC they could be locked in one position with night/day permenent spheres.
Cometary impacts from comets attracted by gravity of the main planet.
I found article regarding this :
http://skyandtelescope.com/resources/seti/article_255_1.asp

Paxdan:

I'd say we have a monopoly on the Solar System, but that there are other solar systems!

So, Sirius System, the solar system around Sirius, extraSolar planets...

I confess to being an inveterate proofreader and picker of small insects out of the fur of other members of Genus Homo!




Toymaker:

Horrible radiation belts, flux tubes zapping the surface, terrible tides, evil organic goo from other moons, oh, and the rest...

Sounds like fun!

For a weekend, anyway...

Bob Shaw

Modern astronomical technology is allowing people to make all kinds of
observations and discoveries these days:

http://arxiv.org/abs/astro-ph/0605598

I reply to the latter one here:
Yes its most likely that any moon will have bound rotation and so have the same hemisphere facing the planet all the time.
But that doesnt cause one hemisphere to be cast in permanent darkness as it appear that to me that your writing.
The duration of daylight on such a moon would be about half of each orbit. Yes about, eclipses by the main planet can make it a bit shorter on the planet facing hemisphere, on most of the out-facing hemisphere of that moon world the eclipse would happen in the night and would not be seen.
_____________

As for finding such moons with a Terrestrial planet finder type of instrument would be hard. First we would have to remove the stellar light, but then the Neptune mass (and perhaps sized) planet would be much brigher than any moon in orbit. The large planet might perhaps not be a complete showstopper, but I do think it adds a major complication for such a search.