Planetary Systems With Habitable Earths?

In my opinion, since the galaxy is of finite age, all life evolved on any of
the billions of planets has probably reached the same point more or less
depending of how oppressive their religions are.
This is probably why all alien visitations are fictious. I would think that
closer to the center of our galaxy, where it is more busy as far as suns and
planets and their closer proximity, some civilizations may have gone between
solar systems where we have only gone to our moon. But going from there to
the outer rim where we are is most likely out of there reach. Forget about
going to other galaxies, this is only a dream for our kind.

"Ron" wrote in message
m...
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
contacted
via the NAM press office (see above).

Normal contact details:

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

David R. Underwood,
Open University (see above)
Tel: +44 (0)1908-652123,
E-mail:

FURTHER INFORMATION AND IMAGES CAN BE FOUND ON THE WEB AT:

The Extrasolar Planets Encyclopedia:

http://www.obspm.fr/encycl/encycl.html


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Forget about
going to other galaxies, this is only a dream for our kind.

But maybe not for another "kind" having vastly more durable bodies and more
extensive knowledge of energy and space.

"Rodney Kelp" wrote in message
...
In my opinion, since the galaxy is of finite age, all life evolved on any
of
the billions of planets has probably reached the same point more or less
depending of how oppressive their religions are.

OTOH, 'we' killed a few billion years as single-celled organisms. Perhaps
other life, if it exists, went multicell 1 billion years before we did.

---
Dave Boll
http://www.daveboll.com/

"Rodney Kelp" wrote in message
...
In my opinion, since the galaxy is of finite age, all life evolved on any
of
the billions of planets has probably reached the same point more or less
depending of how oppressive their religions are.
This is probably why all alien visitations are fictious. I would think
that
closer to the center of our galaxy, where it is more busy as far as suns
and
planets and their closer proximity, some civilizations may have gone
between
solar systems where we have only gone to our moon. But going from there to
the outer rim where we are is most likely out of there reach. Forget about
going to other galaxies, this is only a dream for our kind.

Humans and alligators have a common ancestor, yet we build spaceships and
they don't. We don't know what the rate of evolution is on other planets.
If the dinosaurs hadn't gone extinct, they might have built their first
spaceship 50 million years ago. If a planet was 100 million years older
than Earth, that could make a big difference in terms of how advanced their
life is.

We could get to another galaxy with existing technology, but it would take
10 million years to get there. It would be super expensive, so it isn't
likely to be funded anytime soon.

G EddieA95 wrote:
Forget about
going to other galaxies, this is only a dream for our kind.

But maybe not for another "kind" having vastly more durable bodies and more
extensive knowledge of energy and space.

But even so you are talking about a journey of not less than 10000 years.

--
Sander

+++ Out of cheese error +++

Mike Rhino wrote:
"Rodney Kelp" wrote in message
...
In my opinion, since the galaxy is of finite age, all life evolved on any
of
the billions of planets has probably reached the same point more or less
depending of how oppressive their religions are.
This is probably why all alien visitations are fictious. I would think
that
closer to the center of our galaxy, where it is more busy as far as suns
and
planets and their closer proximity, some civilizations may have gone
between
solar systems where we have only gone to our moon. But going from there to
the outer rim where we are is most likely out of there reach. Forget about
going to other galaxies, this is only a dream for our kind.

Humans and alligators have a common ancestor, yet we build spaceships and
they don't. We don't know what the rate of evolution is on other planets.

Or don't yet? The problem with alligators is that they have a good niche and
are overspecialised. So they have a really steep learning curve to climb.

If the dinosaurs hadn't gone extinct, they might have built their first
spaceship 50 million years ago. If a planet was 100 million years older
than Earth, that could make a big difference in terms of how advanced their
life is.

In 100 million years, earth my well have seen more than one wave of intelligent
life. Chimps might make it in a million - provided we don't create chimp-offshoot
intelligent races before then - and octopuses are another potential candidate
(much longer term).

It is *not* however clear that all intelligent races, no matter how advanced,
will necessarily go into spaceflight.


We could get to another galaxy with existing technology, but it would take
10 million years to get there. It would be super expensive, so it isn't
likely to be funded anytime soon.


The problem is not so much time to get there - once you can buidl large o'neill
colonies you just need engines on them and you can undertake really long voyages -
but the motivation and being sure that anybody actualy arrives there, something
that is presently not known to be true.

There is also the small matter of just how many homely sun style stars there
are in this galaxy, never mind all stars around which humans can probably
confortably live.

--
Sander

+++ Out of cheese error +++

"Sander Vesik" wrote ...
G EddieA95 wrote:
Forget about
going to other galaxies, this is only a dream for our kind.

But maybe not for another "kind" having vastly more durable bodies and more
extensive knowledge of energy and space.

But even so you are talking about a journey of not less than 10000 years.

Be a real shame if you turned up just as the lights were being turned out
.... although that would take rather longer than 10,000 years.