This illustration depicts the aftermath of a collision between two giant exoplanets. What remains is a hot, molten planetary core and a swirling, glowing cloud of dust and debris. Mark A. Garlick
The Discovery:
A glowing
cosmic cloud has revealed a cataclysmic collision.
Key Facts:
Even within
our own solar system, scientists have seen evidence of giant, planetary
collisions from long ago. Remaining clues like Uranus’ tilt and the existence
of Earth’s moon point to times in our distant history when the planets in our
stellar neighborhood slammed together, forever changing their shape and place
in orbit. Scientists looking outside our solar system to far off exoplanets can
spot similar evidence that, across the universe, planets sometimes crash. In
this new study, the evidence of such an impact comes from a cloud of dust and
gas with a strange, fluctuating luminosity.
Details:
Scientists
were observing a young (300-million-year-old) Sun-like star when they noticed
something odd: the star suddenly and significantly dipped in brightness. A team
of researchers looked a little closer and they found that, just before this
dip, the star displayed a sudden spike in infrared luminosity.
In studying
the star, the team found that this luminosity lasted for 1,000 days. But 2.5
years into this bright event, the star was unexpectedly eclipsed by something,
causing the sudden dip in brightness. This eclipse endured for 500 days.
The team
investigated further and found that the culprit behind both the spike in
luminosity and the eclipse was a giant, glowing cloud of gas and dust. And the
most likely reason for the sudden, eclipse-causing cloud? A cosmic collision
between two exoplanets, one of which likely contained ice, the researchers
think.
In a new study
detailing these events, scientists suggest that two giant exoplanets anywhere
from several to tens of Earth masses crashed into one another, creating both
the infrared spike and the cloud. A crash like this would completely liquify
the two planets, leaving behind a single molten core surrounded by a cloud of
gas, hot rock, and dust.
After the
crash, this cloud, still holding the hot, glowing remnant of the collision,
continued to orbit the star, eventually moving in front of and eclipsing the
star.
Fun Facts:
This study was
conducted using archival data from NASA’s now-retired WISE mission – the
spacecraft continues to operate under the name NEOWISE. This star was first detected in 2021 by the ground-based robotic survey ASAS-SN (All-Sky Automated
Survey for Supernovae).
While this
data revealed remnants of this planetary collision, the glow of this crash
should still be visible to telescopes like NASA’s James Webb Space Telescope.
In fact, the research team behind this study is already putting together
proposals to observe the system with Webb.
Discoverers:
The study, “A planetary collision afterglow and transit of the resultant debris cloud,” was published Oct. 11, 2023, in Nature by lead author Matthew Kenworthy alongside 21 co-authors.
Source: Discovery Alert: Glowing Cloud Points to a Cosmic Collision - NASA Science
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