Have We Found the First Planet Outside the Milky Way?

Planets are small and difficult to spot out in the vast reaches of space, but researchers think they've identified one in another galaxy for the first time. Learn more about M51-ULS-1b in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/first-planet-outside-milky-way-news.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of I Heart Radio.
Hey brain Stuff Lauren bol Obam here for those interested
in space science or even science fiction. Astronomers have been
full of fascinating news in the past few years. As
technology improves, researchers have been able to discover even more
celestial objects than we ever imagined, from comets and asteroids

(00:25):
zipping through our Solar System to dark matter and planets
orbiting distant stars. Now we have evidence of planets far
beyond those we've ever discovered before. But all the planets
we found through our advanced technology have been within our
own Milky Way Galaxy until now. That is. In a

(00:45):
paper published in October one in the journal Nature Astronomy,
a team of astronomers and astrophysicists has put forth a
new planetary candidate farther away than we've ever seen before.
It's called Catcheley M fifty one U L S one
B and is located in Messier fifty one, also called
the Whirlpool Galaxy. While humans might never see or even

(01:08):
confirm the existence of this potential planet, even its theoretical
reality paves the way for more discoveries and the deep
reaches of space beyond anything yet discovered. So let's talk
about how we find planets. Four decades researchers have used
data from Earth based and orbital telescopes to find planets

(01:29):
beyond those in our Solar system, called exoplanets. Typically, researchers
look for a transit event, which is when the planet's
orbit takes it in front of its star. From our perspective,
transits occur in our Solar system too. You might recall
one of the most recent transits that occurred in twenty
nineteen when tiny Mercury passed in front of the Sun.

(01:50):
Depending on the size of the planet relative to the star,
a transit event will cause the star's brightness too dim,
even when the star doesn't emit light along the visible wavelength.
That's why the Chandra X ray observatory was used to
discover this new planetary candidate. In many cases, researchers are
able to observe the star dimming and surmise that a

(02:11):
planet must be orbiting that star or stars, as there
are circumbinary planets that orbit two stars. These planetary candidates
are put forward to the scientific community to verify with
additional data, and have resulted in more than four thousand
confirmed exoplanets. Up until this point, though every proposed exo
planet has been located within a small region of our

(02:33):
own galaxy, the Milky Way. What makes this new paper
compelling is the proposal that the researchers have a planetary
candidate outside the Milky Way. Way outside the Milky Way.
According to their research, the potential planet is an estimated
twenty million light years from Earth. They also proposed a
new term for such planets, extra planets. The researchers chose

(02:56):
to look outside our galactic neighborhood for two reasons. For
there's a better probability of discovering a planetary candidate using
an X ray transit technique, since the binary stars that
omit X rays are physically smaller and thus more likely
to be fully obscured when one of their planets transits
across them. The second reason was practical. The team had

(03:17):
access to use the Chandra X ray observatory at a
time when the observatory was pointed at an area of
space where there were lots of data points for the article.
This episode is based on how Stuff Work spoke with
Theoron Carmichael, one of the papers authors, speaking on behalf
of the team. He explained the focus outside of the
Milky Way was due to the number of X ray

(03:38):
sources within the field of view of the Chandra observatory.
This made things more convenient to observe by allowing for
a focus on one area of the sky and not
having to point the telescope in very different locations in
the sky. As of now, we're not aware of any
new exo planet candidates that orbit X resources in the
Milky Way. This technique is certainly applicable to X resources

(03:59):
within the Milky Way, and perhaps now scientists will be
inspired to look when their turn comes up on Chandra. Unfortunately,
due to this potential planet's tremendous distance from Earth and
unique system composition, it's going to take a long time
to verify whether it actually exists. The system has two stars,

(04:21):
a neutron star or black hole astronomers aren't exactly sure
which that's emitting the X rays observed to be dimming
during the transit, and a companion star that's twenty times
the mass of our own son. The planetary candidate orbits
both of those celestial objects, making it circumbinary, and it
takes roughly seventy years to make that orbit, so the

(04:43):
next time a transit might be visible would be several
decades from now. Carmichael said, Since the next transit event
is so uncertain, it could be as soon as decades
from now or much longer. There aren't any plans in
place to take follow up observations of this particular planet candidate. Instead,
new X ray observations and archival data of previous observations

(05:04):
are more readily available to search for more planet candidates
like this one. So while the existence of M fifty
one u l S one B might never be verified,
researchers plan to use it as inspiration to search for
other planetary candidates like it, far beyond the bounds of
our galaxy and perhaps even within it. Today's episode is

(05:30):
based on the article Researchers find first potential planet outside
the Milky Way on how stuff works dot Com, written
by Valerie Stymack. Brain Stuff is production by Heart Radio
in partnership with how stuff works dot Com, and it
is produced by Tyler Clang. Or more podcasts from my
heart Radio, visit the i heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows.