NASA's Found Exoplanet orbiting in a triple star system!
In 2009, NASA's Kepler mission was launched. Kepler was a space telescope designed to survey
a portion of the Milky Way galaxy in search of exoplanets, which are planets outside our
solar system. Using data from the Kepler mission and the
extended K2 mission, scientists have identified more than 2,800 candidate exoplanets and have
confirmed more than 2,600 of these as bona fide planets. A handful of planets are thought
to be rocky like Earth (but a bit bigger), and orbit in the habitable zone of their stars,
where liquid water - an essential ingredient of life as we know it - might exist.
Since the number of planets it's huge, Kepler mission has to set aside some of the candidate
exoplanets and continue to work on the most promising ones.
These uncertain candidates are usually buried and forgotten, but sometimes, Kepler has to
resurrect some of them from the dead. It is the case of the KOI-5Ab exoplanet, one
of the first candidates to be found by the mission.
What makes KOI-5Ab so interesting? Well, it is orbiting in a triple-star system,
with consequences on his orbital path.
Follow me on this journey through the universe to get to know more about this strange world
and the triple-star system he lives in!
Shortly after NASA's Kepler mission began operations back in 2009, the space telescope
spotted what seemed to be a planet about half the size of Saturn, in a multiple-star system.
(as a criterion for comparison, Saturn has a radius of 36,183.7 miles (58,232 kilometres))
KOI-5Ab was only the second planet candidate to be found by the mission, and exciting as
it was at the time, it was ultimately set aside as Kepler racked up more and more planet
discoveries. In fact, by the end of the spacecraft’s
operations in 2018, Kepler had discovered a whopping 2,394 exoplanets or planets orbiting
stars beyond our sun, and an additional 2,366 exoplanet candidates that would still need
confirmation. In fact, scientists must gather many observations
and carefully analyze their data before they can be even somewhat sure that they’ve discovered
new worlds. But what is it needed to get a...confirmation?
Well, for instace, they have to make sure the planet signature obtained with the transit
method couldn't be something else. In fact, not all dips in a star's brightness are caused
by transiting planets and there may be another object – such a companion star, a group
of asteroids, a cloud of dust or a brown dwarf – that makes a regular trip around the target
star. Also, it is needed a follow up with a second
detection method, because finding the same planet candidate using two different techniques
is a strong sign that the planet exists, and is the standard for “confirming” a planet.
(that's also the reason why a vast network of ground-based telescopes will be looking
for the same planet candidates that were detected). Another step is to write a paper after thoroughly
analyzing the data, and running tests to make sure that their result still looks like the
signature of a planet. The paper has to be reviewed by scientific experts not involved
in the study (peer review). Also, did you know that scientists sometimes
even uncover planets with the help of people like you?
Exoplanet K2-138 was discovered through citizen scientists in Kepler’s K2 mission data.
Based on surveys so far, scientists calculate that almost every star in the Milky Way should
have at least one planet. That makes billions more, waiting to be found!
Anyway, KOI-5Ab planet passed all of these steps.
<<I thought to myself, "I remember this target”, KOI-5Ab got abandoned because it was complicated,
and we had thousands of candidates>> said David Ciardi, chief scientist of NASA's Exoplanet
Science Institute. <<There were easier pickings than KOI-5Ab, and we were learning something
new from Kepler every day, so that KOI-5 was mostly forgotten.>>
Now, after a lengthy hunt that spanned many years and many telescopes, Ciardi said he
has "resurrected KOI-5Ab from the dead." Thanks to new observations from NASA’s second planet-hunting
mission, the Transiting Exoplanet Survey Satellite, or TESS, and a number of ground-based telescopes,
Ciardi was finally able to untangle all the evidence surrounding KOI-5Ab and prove its
existence. There are some intriguing details about it to mull over.
Most likely a gas giant planet like Jupiter or Saturn in our solar system given its size,
KOI-5Ab is unusual in that it orbits a star in a system with two other companion stars,
circling on a plane that’s out of alignment with at least one of the stars. The arrangement
calls into question how each member in this system formed out of the same swirling clouds
of gas and dust. Ciardi, who is located at Caltech in Pasadena, California presented
the findings at a virtual meeting of the American Astronomical Society.
Here's a little bit of history of the discovery. After its initial detection by Kepler, Ciardi
and other researchers picked up the trail on KOI-5Ab as part of a cache of planet candidates
they were following upon. Using data from the W. M. Keck Observatory in Hawaii, Caltech's
Palomar Observatory near San Diego and Gemini North in Hawaii, Ciardi and other astronomers
determined that KOI-5b appeared to be circling one star in a triple-star system. However,
they still couldn’t tease out whether the planet signal was actually an erroneous glitch
from one of the two other stars, or, if the planet was real, which of the stars it orbited.
Then, in 2018, TESS came along. Like Kepler, TESS looks for the blinking of starlight that
comes when a planet crosses in front of, or transits, a star. TESS observed a portion
of Kepler's field of view, including the KOI-5 system. Sure enough, TESS also identified
KOI-5Ab as a candidate planet, though TESS calls it TOI-1241b. As Kepler had observed
previously, TESS found that the planet orbited its star roughly every five days.
He then went back and re-analyzed all the data, and then searched for new clues from
ground-based telescopes. Deploying an alternate technique to Kepler and TESS, the Keck Observatory
is often used for follow-up searches of exoplanets by measuring the slight wobble in a star as
a planet circle around it and exerts a gravitational tug. Ciardi, teaming up with other scientists
through an exoplanet collaboration group called the California Planet Search, looked for any
wobbles in Keck’s data on the KOI-5 system. They were able to tease out a wobble produced
by the inner companion star orbiting the primary star from the wobble of the apparent planet
as it orbits the primary star. Together, the different collections of data from the space-
and ground-based telescopes helped confirm that KOI-5Ab is, indeed, a planet orbiting
the primary star. “Bingo – it was there! If it weren't for
TESS looking at the planet again, I would never have gone back and done all this detective
work," he said. “But it truly did take a lot of sleuthing within data collected from
many different telescopes to finally nail down this planet.”
KOI-5Ab orbits Star A, which has a relatively close companion, Star B. Star A and Star B
orbit each other every 30 years. A third gravitationally bound star, Star C, orbits stars A and B every
400 years. Can you imagine how strange and beautiful
is the universe we are living in? We live in the solar system, on the planet
we call Earth, that is a planet orbiting a single star, the Sun, but the experience teaches
us that a star system could be very different from our solar system. And that a huge variety
of planets exist.
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Anyway, the combined data set also reveals that the orbital plane of the planet is not
aligned with the orbital plane of Star B, the second inner star as might be expected
if the stars and planet all formed from the same disk of swirling material. Astronomers
are not sure what caused the misalignment of KOI-5Ab but believe that the second star
gravitationally kicked the planet during its development, skewing its orbit and causing
it to migrate inward. Triple-star systems make up about 10% of all-star systems.
This is not the first evidence of planets in double- and triple-star systems. One striking
case involves the triple-star system GW Orionis, in which a planet-forming disk has been torn
into distinct, misaligned rings, where planets may be forming. Yet despite hundreds of discoveries
of planets in the multiple-star system, far fewer planets have been observed than in single-star
systems. This could be due to an observational bias (single-star planets are easier to detect),
or because planet formation is, in fact, less common in multiple-star systems.
“This research emphasizes the importance of NASA’s full fleet of space telescopes
and their synergy with ground-based systems," said Jessie Dotson, the project scientist
for the Kepler space telescope at NASA’s Ames Research Center in California’s Silicon
Valley. "Discoveries like this one can be a long haul.”
Future instruments, such as the Palomar Radial Velocity Instrument at the 200-inch Hale Telescope
at Palomar, the NASA and National Science Foundation’s NEID instrument in southern
Arizona, and the Keck Planet Finder will open up new avenues for learning about exoplanets.
This could be a chance to go deeper in the studying of the planet formation process.
As Ciardi said: “We don’t know of many planets that exist
in triple-star systems, and this one is extra special because its orbit is skewed, “We
still have a lot of questions about how and when planets can form in multiple-star systems
and how their properties compare to planets in single-star systems. By studying this system
in greater detail, perhaps we can gain insight into how the universe makes planets."
It was long ago when humans started to look at the sky, thinking about the physics that
governs the universe, and it still amazes us.
Every time we dig deep in the understanding of something, whether it is a planet or a
black hole, we found ourselves astonished because reality is always a little bit complicated
and -I would say- creative than we expected. And we have to thank science because it is
the medium that allows us to enjoy the unexpected artwork of the Universe.
"This video ends here! Thanks for watching everyone! What are your thoughts about the
importance of TESS and ground-based telescopes? Did you know about the existence of KOI-5Ab?
Let us know in the comments below! See you next time on the channel!"