In a very incredible world first, astrophysicists have detected multiple planets in another galaxy. These planets range from masses as small as the Moon to ones as great as Jupiter. Given how much difficult it is to find exoplanets even within our Milky Way galaxy, this is no mean feat.
Researchers at the
University of Oklahoma achieved this thanks to clever use of gravitational
microlensing. The technique, first predicted by Einstein's theory of general
relativity, has been used to find exoplanets within Milky Way, and it's the
only known way of finding the smallest and most distant planets, thousands of
light-years from Earth. As a planet orbits a star, the gravitational field of
the system can bend the light of a distant star behind it.
We know what this looks like
when it's just two stars, so when a planet enters the mix, it creates a further
disturbance in the light that reaches us - a recognisable signature for the
planet.
So far, 53 exoplanets within
the Milky Way have been detected using this method. To find planets farther
afield, though, something a little bit more powerful than a single star was
required.
Oklahoma University
astronomers Xinyu Dai and Eduardo Guerras studied a quasar 6 billion
light-years away called RX J1131-1231, one of the best gravitationally lensed
quasars in the sky. The gravitational field of a galaxy 3.8 billion light-years
away between us and the quasar bends light in such a way that it creates four
images of the quasar, which is an active supermassive black hole that's
extremely bright in X-ray, thanks to the intense heat of its accretion disc.
Using data from NASA's
Chandra X-ray observatory, the researchers found that there were peculiar line
energy shifts in the quasar's light that could only be explained by planets in
the galaxy lensing the quasar. It turned out to be around 2,000 unbound planets
with masses ranging between the Moon and Jupiter, between the galaxy's stars.
"We are very excited
about this discovery. This is the first time anyone has discovered planets
outside our galaxy," Dai said.
Of course, we haven't seen
the planets directly, and are unlikely to in the lifetime of anyone alive
today. But being able to detect them at all is an incredible testament to the
power of microlensing, not to mention being evidence that there are planets in
other galaxies. Of course, common sense would dictate that planets are out
there - but evidence is always nice.
"This is an example of
how powerful the techniques of analysis of extragalactic microlensing can
be," said Guerras. "This galaxy is located 3.8 billion light years
away, and there is not the slightest chance of observing these planets
directly, not even with the best telescope one can imagine in a science fiction
scenario.
"However, we are able
to study them, unveil their presence and even have an idea of their masses.
This is very cool science."
The research has been
published in The Astrophysical Journal.
Via Sciencealert
No comments