Ultimate solar system could contain 60 Earths
* 13:32 30 May 2014 by _Jacob Aron_
(http://www.newscientist.com/search?rbauthors=Jacob+Aron)
Why settle for one habitable planet, when you can have 60? An
astrophysicist has designed the ultimate star system by cramming in as many
Earth-like
worlds as possible without breaking the laws of physics. Such a monster
cosmic neighbourhood is unlikely to exist in reality, but it could inspire
future exoplanet studies.
_Sean Raymond_ (http://www.obs.u-bordeaux1.fr/e3arths/raymond/) of
Bordeaux Observatory in France started his game of _fantasy star system_
(http://planetplanet.net/2014/05/13/building-the-ultimate-solar-system/) with
a
couple of ground rules. First, the arrangement of planets must be
scientifically plausible. Second, they must be gravitationally stable over
billions of
years: there is no point in putting planets into orbit only to watch them
spiral into the sun.
"The arguments were based on the recent scientific literature as well as
some simple calculations I did," says Raymond. In some cases it was
impossible to choose between two scenarios because of a lack of data, so he
just
picked the one he liked best.
A red dwarf star could support 24 habitable, Earth-sized planets (Image:
planetplanet.net)
To start with he chose a red dwarf star as the system's host because they
have a lower mass than stars like our sun and so live longer, _giving a
stable habitable zone_
(http://www.newscientist.com/article/dn23750-three-habitable-worlds-found-around-the-same-star.html)
– the region around a star in
which liquid water can exist.
Next, he used a couple of tricks to boost the planetary potential of his
system. An Earth-sized planet can also have an almost Earth-sized moon, with
the two worlds orbiting around a central point. What's more, two pairs of
planets can orbit a star at the same distance, provided that they are
separated by 60 degrees, thanks to a couple of gravitationally stable points.
In
our solar system these points are normally inhabited by asteroids, rather
than planets, but nothing rules out a multiple planet scenario. Objects in
this configuration are known as Trojans – Jupiter has thousands, and _even
Earth has one_
(http://www.newscientist.com/article/mg21128234.200-earth-stalker-found-in-eternal-twilight.html)
.
There is room for six of these orbital configurations in the habitable
zone of a red dwarf, giving a total of 24 habitable planets in one system. But
it turns out there is also another way to build a packed system: Jupiters.
A star system with four gas giants could support 36 habitable worlds
(Image: planetplanet.net)
Gas giants such as Jupiter are not habitable to life as we know it, but
they can be orbited by Earth-like moons. In our solar system, Europa and
Enceladus, which orbit Jupiter and Saturn, respectively, are _prime candidates
for extraterrestrial life_
(http://www.newscientist.com/article/dn25379-squirting-moons-face-off-in-race-to-find-alien-life.html)
. Raymond calculates
that a red dwarf could hold four Jupiter-like planets, each with five
Earth-like moons. What's more, the Trojan trick can allow another two
Earth-like
planets on either side of the orbiting Jupiters, upping the total number of
habitable worlds around the red dwarf to 36.
Finally, Raymond turned his star system into a binary one, with two red
dwarfs separated by roughly the distance from our sun to the edge of the
solar system. Theory allows one star to carry the Earth-only configuration,
and
the other to carry the Earth-plus-Jupiters configuration. This creates the
ultimate star system, with 60 habitable planets to choose from.
"It is thought provoking," says _Mikko Tuomi_
(http://users.utu.fi/miptuom/) of the University of Hertfordshire in Hatfield,
UK, who helped to
discover the _star system with the largest number of known planets_
(http://www.newscientist.com/blogs/shortsharpscience/2012/04/new-planet-record-suggests-sol
.html) , but the odds of something like it actually forming in the real
universe are slim to none. "This would be due to the lack of matter at or
near the habitable zone in the accretion disk from which planets form," says
Tuomi. Sufficiently advanced aliens could build a system like this, he says,
but it is not clear why they would bother.
"I admit that it would be extremely fortuitous for nature to produce a
system that was so spectacular," says Raymond. "Still, each piece of the
system is plausible and even expected from simulations of planetary
formation."
Coming up with the system has also thrown up new scientific questions, he
says. "I ended up doing a lot of research into the different pieces of the
puzzle, and coming at it from this point of view gave me some new ideas I'm
planning to test in the future."
The ultimate solar system: a binary star system supporting 60 habitable
planets (Image: planetplanet.net)
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[RC] Ultimate solar system could contain 60 Earths
BILROJ via Centroids: The Center of the Radical Centrist Community Sat, 31 May 2014 00:51:07 -0700
