Tweet
Was a Giant Planet Ejected
From the Solar System?
The Fifth Planet sounds like a great name for a sci-fi movie -- perhaps a
sequel to the 1997 movie "The Fifth Element." But the fifth planet may be
real; a hypothesized giant world that was flung out of our solar system
four billion years ago. It would have drifted tens of thousands of light years
away by now.
Why even suspect that such a planet existed?
Though astronomers have found many planetary systems around
neighboring stars, our own solar system looks like it's the exception rather
than the rule. We're discovering that our system is an uncommonly orderly
place where the planets behave themselves in wide orbits that are nearly
circular.
But the planetary systems around other stars found so far present sort of
a Wild West of planets. Their orbits can be steeply inclined to one another
(our eight major planets are coplanar). There are many giant planets that
have migrated precariously close to their stars. Other planets are in roller
coaster highly elliptical orbits that alternatively freeze and cook them.
Even more befuddling, it's hard for theoreticians to build a planet formation
model that winds up looking like our solar system.
A new set of computer simulations by David Nesvorny of the Southwest
Research Institute in Boulder, Colorado, shows that this will work if there
was once a fifth giant planet in addition to Jupiter, Saturn, Uranus, and
Neptune.
Nesvorny models place a fifth hefty planet, several dozen times the mass
of the Earth at various possible locations in the outer solar system: midway
between Saturn and Uranus, and just beyond Neptune. In this game of
orbital musical chairs, the fifth planet was ejected after a tussle with
Jupiter –- sort of a celestial King Kong vs. Godzilla.
This may sound extraordinary but there is plenty of evidence for orphaned
free-floating planets wandering our galaxy. A 2006-2007 survey of the
Milky Way used gravitational lensing to find 10 dark objects drifting in front
of distant background stars. Statistically, this means there could be as
many as hundreds of billions of castoff planets plying inside our galaxy.
Looking for evidence of a fifth giant planet calls for solar system forensics.
God didn't leave behind any file footage of the solar system's formative
years, after all.
First, it is known that Uranus and Neptune are too far from the sun for
them to have formed in their present locations. There simply has not been
enough time and materials for them to agglomerated into 15-Earth mass
worlds. Uranus and Neptune must have formed closer into the sun and then
migrated outward.
This implies that the early solar system was very chaotic. Smaller bodies,
the planetesimals, were gravitationally kicked around and the exchange of
momentum widened the orbits of the outer planets. Our moon bears the
scars of this rough and tumble period called the Late Heavy Bombardment,
of about 4 billion years ago.
The planetesimal debris was then snowplowed outward to form the Kupier
belt, where Pluto dwells. Kuiper belt objects are not spread out uniformly in
but are clustered into three distinct populations. This means that the belt
was; extensively sculpted by the gravitational influence of the giant
planets.
The ejected planet would not necessarily be lifeless even though it is
sailing through the numbing cold of interstellar space. It presumably would
have moons. Gravitational tidal forces could heat them so that they would
remain warm in the absence of a star. The moons Io (orbiting Jupiter) or
Enceladus (orbiting Saturn) are the archetype of what would be plausible.
Microbes could live happily without the need for a sun in the sky. Among
the billions of flung off worlds in our galaxy, this one would be isotopically
stamped: Made By Sol.
Was a Giant Planet Ejected From the Solar System? : Discovery News
From the Solar System?
The Fifth Planet sounds like a great name for a sci-fi movie -- perhaps a
sequel to the 1997 movie "The Fifth Element." But the fifth planet may be
real; a hypothesized giant world that was flung out of our solar system
four billion years ago. It would have drifted tens of thousands of light years
away by now.
Why even suspect that such a planet existed?
Though astronomers have found many planetary systems around
neighboring stars, our own solar system looks like it's the exception rather
than the rule. We're discovering that our system is an uncommonly orderly
place where the planets behave themselves in wide orbits that are nearly
circular.
But the planetary systems around other stars found so far present sort of
a Wild West of planets. Their orbits can be steeply inclined to one another
(our eight major planets are coplanar). There are many giant planets that
have migrated precariously close to their stars. Other planets are in roller
coaster highly elliptical orbits that alternatively freeze and cook them.
Even more befuddling, it's hard for theoreticians to build a planet formation
model that winds up looking like our solar system.
A new set of computer simulations by David Nesvorny of the Southwest
Research Institute in Boulder, Colorado, shows that this will work if there
was once a fifth giant planet in addition to Jupiter, Saturn, Uranus, and
Neptune.
Nesvorny models place a fifth hefty planet, several dozen times the mass
of the Earth at various possible locations in the outer solar system: midway
between Saturn and Uranus, and just beyond Neptune. In this game of
orbital musical chairs, the fifth planet was ejected after a tussle with
Jupiter –- sort of a celestial King Kong vs. Godzilla.
This may sound extraordinary but there is plenty of evidence for orphaned
free-floating planets wandering our galaxy. A 2006-2007 survey of the
Milky Way used gravitational lensing to find 10 dark objects drifting in front
of distant background stars. Statistically, this means there could be as
many as hundreds of billions of castoff planets plying inside our galaxy.
Looking for evidence of a fifth giant planet calls for solar system forensics.
God didn't leave behind any file footage of the solar system's formative
years, after all.
First, it is known that Uranus and Neptune are too far from the sun for
them to have formed in their present locations. There simply has not been
enough time and materials for them to agglomerated into 15-Earth mass
worlds. Uranus and Neptune must have formed closer into the sun and then
migrated outward.
This implies that the early solar system was very chaotic. Smaller bodies,
the planetesimals, were gravitationally kicked around and the exchange of
momentum widened the orbits of the outer planets. Our moon bears the
scars of this rough and tumble period called the Late Heavy Bombardment,
of about 4 billion years ago.
The planetesimal debris was then snowplowed outward to form the Kupier
belt, where Pluto dwells. Kuiper belt objects are not spread out uniformly in
but are clustered into three distinct populations. This means that the belt
was; extensively sculpted by the gravitational influence of the giant
planets.
The ejected planet would not necessarily be lifeless even though it is
sailing through the numbing cold of interstellar space. It presumably would
have moons. Gravitational tidal forces could heat them so that they would
remain warm in the absence of a star. The moons Io (orbiting Jupiter) or
Enceladus (orbiting Saturn) are the archetype of what would be plausible.
Microbes could live happily without the need for a sun in the sky. Among
the billions of flung off worlds in our galaxy, this one would be isotopically
stamped: Made By Sol.
Was a Giant Planet Ejected From the Solar System? : Discovery News