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Did a lost star knock the Earth off its orbit? New theory to explain why our planet circles the sun at an angle to the solar equator
- The Earth circles around the solar system at an angle 7 degrees off the solar equator
- Theory suggests that gravity from errant star travelling near to our solar system pulled the planets out of whack
By DAMIEN GAYLE
|
It has been a long standing puzzle to astronomers: why is the Earth's orbit tipped 7 degrees relative to the sun's equator?
Now
a new
theory suggests that violent stage of our solar system's history, an
errant young star strayed close and pulled our developing planets out of
whack with the sun's equator.
Konstantin
Batygin of the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Massachusetts, suggests that our star had a near stellar
neighbour at the time Earth formed.
Our
solar system: All the planets in our system orbit at angles to the
sun's equator. A new theory suggests they may have been pulled out of
whack by a nearby stellar neighbour that has long ago left the scene
It
is the gravitational of this nearby star on our developing system that
explains why the planets don't orbit neatly around the sun's
equator.
Dr
Batygin outlines his theory in a letter published in the journal Nature
titled A primordial origin for misalignments between stellar spin axes
and planetary orbits.
It
was thought that such planets were victims of violent events in which
the gravitational force of another planet kicked them on to their
odd paths.
LOST IN SPACE: THE HOMELESS PLANET WITHOUT A STAR TO ORBIT
A ‘homeless planet’ which floats through space without orbiting a star had been discovered for the first time.
Scientists
have speculated on the existence of such a planet and have been
trawling the night skies for more than a decade, although the hunt was
described as looking for a ‘needle in a thousand haystacks’.
The
isolated planet, shown below in an artist's impression, which
astronomers believe may have been flung away during its formation, is
not tied by gravity to a star and in 100 light years away.
But
Dr Konstantin contends that young suns may develop in clusters, with
the disks of matter surrounding them and nearly always spreading from
the equator being tugged by a neighbouring star.
In
his letter to Nature, he calculates how a young star's protoplanetary
disk can be yanked off its equatorial orbit by a second star.
'I
think somewhere in the Milky Way, there's a star that's responsible for
tilting us,' he writes, adding that it probably then fled the after the
planets formed.
Josh Winn, an astronomer at the Massachusetts Institute of Technology in Cambridge, told ScienceNOW that he thinks Dr Batygin's theory is 'an entirely plausible idea'.
'The
best thing about it is we can test it,' he added, telling the online
magazine that he hopes to use instruments to observe multiplanet systems
and to evaluate the theory.
Nasa's
Kepler spacecraft has so far measured the tilt of just one multiplanet
system, Kepler 30, whose three planets all line up with their sun's
equator.
Of
course, there are many solar systems that still have more than one
star, for example our nearest neighbour Alpha Centauri, which has three
stars - one of which has a planet similar in size to our own.
'There's a good chance that astronomers will find misalignment in the Alpha Centauri system,' Dr Batygin says.
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