[semi-OT] habitable planets about other stars

Hey all,

I'm forwarding this off to the mailing list for those people who are doing the
campaign things and are interested in building or developing their own star
systems.

I was just going to send the link, but I found that my antiquated Netscape
(4.7) gets buggered up when trying to read it. Plus I don't
know how many people on the list here have fancy-dancy browsers, and
how many do not. :-)  (note the last paragraph that speaks of space
telescopes in the next decade is in "hoping" land ;-).

Mk

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http://www.ras.org.uk/html/press/pn0413ras.html

RAS Press Notice PN04-13 (NAM 10):
Planetary systems with habitable Earths?

Date: 1 April 2004

Issued by Jacqueline Mitton and Peter Bond, RAS Press Officers.

National Astronomy Meeting Press Room phones (30 March - 2 April only):
+44 (0)1908 659726   +44 (0)1908 659729   +44 (0)1908 659730

CONTACT DETAILS ARE LISTED AT THE END OF THIS RELEASE.

**************************************************************

PLANETARY SYSTEMS WITH HABITABLE 'EARTHS'?

More than 100 planetary systems have already been discovered around distant
stars. Unfortunately, the limitations of current technology mean that only
giant planets (like Jupiter) have so far been detected, and smaller, rocky
planets similar to Earth remain out of sight.

How many of the known exoplanetary systems might contain habitable
Earth-type planets? Perhaps half of them, according to a team from the
Open University, led by Professor Barrie Jones, who will be describing their
results today at the RAS National Astronomy Meeting in Milton Keynes.

By using computer modelling of the known exoplanetary systems, the group has
been able to calculate the likelihood of any 'Earths' existing in the
so-called habitable zone - the range of distances from each central star
where life as we know it could survive. Popularly known as the "Goldilocks"
zone, this region would be neither too hot for liquid water, nor too cold.

By launching 'Earths' (with masses between 0.1 and 10 times that of our Earth)
into a variety of orbits in the habitable zone and following their progress
with the computer model, the small planets have been found to suffer a variety
of fates. In some systems the proximity of one or more
Jupiter-like planets results in gravitational ejection of the 'Earth'
from anywhere in the habitable zone. However, in other cases there are safe
havens in parts of the habitable zone, and in the remainder the entire zone is
a safe haven.

Nine of the known exoplanetary systems have been investigated in detail using
this technique, enabling the team to derive the basic rules that determine the
habitability of the remaining ninety or so systems.

The analysis shows that about half of the known exoplanetary systems could
have an 'Earth' which is currently orbiting in at least part of the habitable
zone, and which has been in this zone for at least one billion years. This
period of time has been selected since it is thought to be the minimum
required for life to arise and establish itself.

Furthermore, the models show that life could develop at some time in about two
thirds of the systems, since the habitable zone moves outwards as the central
star ages and becomes more active.

HABITABLE MOONS

A different aspect of this problem is being studied by PhD student David
Underwood, who is investigating the possibility that Earth-sized moons
orbiting giant planets could support life. A poster setting out the
possibilities will be presented during the RAS National Astronomy Meeting.

All of the planets discovered so far are of similar mass to Jupiter, the
largest planet in our Solar System. Just as Jupiter has four
planet-sized
moons, so giant planets around other stars may also have extensive satellite
systems, possibly with moons similar in size and mass to Earth.

Life as we know it cannot evolve on a gaseous, giant planet. However, it
could survive on Earth-sized satellites orbiting such a planet if the
giant is located in the habitable zone.

In order to determine which of the gas giants located within habitable zones
could possess a life-friendly moon, the computer models search for
systems
where the orbits of Earth-sized satellites would be stable and confined
within the habitable zone for at least the one billion years needed for life
to emerge.

The OU team's method of determining whether any putative 'Earths' or
Earth-sized satellites in habitable zones can offer suitable conditions
for life to evolve can be applied rapidly to any planetary systems that are
newly announced. Future searches for 'Earths' and extraterrestrial life should
also be assisted by identifying in advance the systems most likely to house
habitable worlds.

The predictions made by the simulations will have a practical value in years
to come when next-generation instruments will be able to search for the
atmospheric signatures of life, such as large amounts of oxygen, on 'Earths'
and Earth-sized satellites.

BACKGROUND

There are currently 105 known planetary systems other than our own, with 120
Jupiter-like planets orbiting them. Two of these systems contain three
known planets, 11 contain two and the remaining 92 each have one. All but one
of these planets has been discovered by their effect on their parent stars'
motion in the sky, causing them to wobble regularly. The extent of these
wobbles can be determined from information within the light received from the
stars. The remaining planet was discovered as the result of a slight dimming
of starlight caused by its regular passage across the disk of its parent star.

Future discoveries are likely to contain a higher proportion of systems that
resemble our Solar System, where the giant planets orbit at a safe distance
beyond the habitable zone. The proportion of systems that could have habitable
'Earths' is, therefore, likely to rise. By the middle of the next decade,
space telescopes should be capable of seeing any 'Earths' and investigating
them to see if they are habitable, and, indeed, whether they actually support
life.

NOTES FOR EDITORS The 2004 RAS National Astronomy Meeting is hosted by the
Open University, and sponsored by the UK Particle Physics and Astronomy
Research Council (PPARC).

CONTACTS:

> From 30 March to 2 April, Professor Jones and Mr. Underwood can be

Normal contact details:

Professor Barrie W. Jones Physics & Astronomy Dept. Open University Milton
Keynes MK7 6AA
     Tel: +44 (0)1908-653229