Astronomers have confirmed a world that’s less than a
million years old as the youngest known planet, using data from NASA-funded
archives. Called Elias 2-24 b, the baby planet is still whirling in its natal
disk of dust and gas.
“Our planet-formation models already struggled to
explain the previous record holders for the youngest known planet — a four-way
tie between two planets orbiting the star PDS 70 and two planets orbiting the
star WISPIT 2 — which are all more than 5 million years old,” said Lucas Cieza,
a professor at the Instituto de Estudios Astrofísicos in Chile and co-author of
a paper detailing the results. “Elias 2-24 b shows us that even our best
planet-formation models are still missing some important processes.”
In a study published Wednesday in The Astrophysical
Journal Letters, a team led by Andrea Bernardi, a doctoral candidate at the
Universidad Diego Portales in Chile, homed in on archival observations of seven
stars that were observed using the coronagraph at the W. M. Keck Observatory in
Hawaii, which partners with NASA under a cooperative agreement. Each of these
stars hosts a debris disk chock-full of dust, gas, and chunks of ice and rock
with structures and gaps in the disk hinting that planets may be forming around
them.
Artist’s concept depicting Elias 2-24 b, the youngest
exoplanet detected to date, still growing within the disk of gas and dust
surrounding its young host star. Material from the disk is actively accreting
onto the Jupiter-mass planet, which sits within a prominent gap in the disk,
supporting the leading theory of giant planet formation.
W. M. Keck Observatory/Adam Makarenko
With the coronagraph blocking light from the host
stars, astronomers searched for fainter planets orbiting those stars that could
be embedded in the dusty disks. Planets found outside our own solar system are
called exoplanets.
“The planets should be found within the gaps, since
they are carving them,” Bernardi said. “And that’s exactly where we found Elias
2-24 b.”
The planet orbiting the star Elias 2-24 is about as
massive as Jupiter and the star is about 450 light-years from Earth. Studying
this system offers a time machine of sorts for scientists to explore what our
own planetary system may have been like billions of years ago.
Construction zone
Stars are born in swirling clouds of gas and dust,
swaddled in haze. Orbiting planets form from leftover material that clumps up
and gradually sculpts a path around the star. But it’s difficult to study an
exoplanet’s newborn stage because of all the dust that shrouds them.
Most of the exoplanets we’ve discovered so far have
been found using transits, which happen when a planet passes in front of its
star and temporarily dims the amount of light we receive.
Those transits are hard to spot when the planets are
still deeply buried in dust or orbiting far from the star. That’s why an
overwhelming majority of the 6,000 currently confirmed exoplanets are billions
of years old and very close to their stars. Current planet-formation models
rely on a combination of complex theories and simulations, along with
observations of young stars with disks where the presence of planets cannot yet
be detected. Finding and studying more baby planets like Elias 2-24 b will help
astronomers refine those models.
“The galaxy churns out new stars and planets
continuously, so there are many in every stage of evolution,” Cieza said. “That
means we can see the entire process in theory, but there is a large gap in what
most telescopes can detect. We are mostly blind to these baby planets right
now.”
Artist’s animation depicting Elias 2-24 b, the
youngest exoplanet detected to date, still growing within the disk of gas and
dust surrounding its young host star. Material from the disk is actively
accreting onto the Jupiter-mass planet, which sits within a prominent gap in
the disk, supporting the leading theory of giant planet formation.
W. M. Keck Observatory/Adam Makarenko
Connecting dots
The confirmation using Keck data solves a mystery that
has puzzled astronomers for a decade. About a decade ago, observations from
ALMA (Atacama Large Millimeter/submillimeter Array) in Chile showed a gap in
the young star’s dusty disk. The European Southern Observatory’s Very Large
Telescope in Chile then detected a faint point of light sitting in that gap.
Astronomers debated whether it could be a planet;
according to planet formation theories, such gaps appear too early and too far
from their stars for planets to have formed. Current models predict that it
takes about 5 million years to form a Jupiter-size planet at Jupiter’s distance
from the Sun (which is just over five times larger than the distance of Earth
to the Sun), and even longer farther out. Yet the glowing dot they spotted was
55 times farther from its star than Earth is from the Sun and already behaving
like a forming planet.
So Bernardi’s team searched the Keck Observatory
Archive, a NASA-funded partnership between Keck Observatory and the NASA
Exoplanet Science Institute at Caltech/IPAC, for the same little point of light
again and found it in observations from 2018 and 2020. They stitched the
observations together to analyze its motion over time and found that it behaved
more like a planet than an imaging defect or background star, ultimately
confirming it as Elias 2-24 b.
“We usually hear about telescopes working separately,
but this confirmation was possible only by using multiple telescopes together,”
Bernardi said. “Elias 2-24 b is at the limit of what current telescopes can
detect, but with new instruments like NASA’s Nancy Grace Roman Space Telescope,
such detections should become easier.”
Roman, which just launched Aug. 30, is equipped with
an even more powerful coronagraph and is capable of spotting planets that are
much harder for other telescopes to see. By employing the same technique, Roman
could find planets in much smaller orbits, including true Jupiter analogs that
are currently impossible to see through the glare. Elias 2-24 b is about 10
times farther out from its host star.
“This is just the beginning of a new era of
discovery,” Cieza said. “It’s incredible that with modern technology, we are
actually able to see planet formation in action, and Roman will take planet
hunting to the next level.”
To learn more about NASA’s exploration of exoplanets,
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Source: Newfound ‘Baby’ Planet Smashes Record for Youngest Known World - NASA Science
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