Image courtesy of NAOJ/Ko Arimatsu.
Joel Kontinen
A tiny The
object, located in the Kuiper Belt of distant frozen bodies at the edge of the
solar system, is formally named (612533) 2002 XV93, after the date of its
discovery nearly a quarter of a century ago. It has a diameter of less than 500
kilometres.
he object
also belongs to a class of objects known as plutinos because they are in the
same stable orbit as Pluto, completing three revolutions around the sun for
every two made by Neptune.
It seems
that this object, though it is small, has an atmosphere,
On 10
January 2024, 2002 XV93 passed in front of a distant star, causing what is
called an occultation. Ko Arimatsu at Kyoto University and his colleagues
observed this event from three locations in Japan.
The team
saw the star gradually fade and recover over about 1.5 seconds near the edge of
the shadow.
“These
gradual changes are best explained if the star’s light was bent by a very thin
atmosphere around 2002 XV93,” says Arimatsu.
The team
estimates a surface pressure of about 100 to 200 nanobars, roughly 5 million to
10 million times thinner than Earth’s atmosphere and about 50 to 100 times
thinner than Pluto’s tenuous atmosphere.
“You could
not breathe it, feel wind from it, or see anything like Earth’s sky,” says
Arimatsu. “But it is not negligible scientifically because even such a thin
atmosphere can measurably bend starlight, and it tells us that volatile gases
are present or being supplied around a very small icy body.”
The team
couldn’t determine the composition of the atmosphere directly from the
data. Arimatsu suggests methane, nitrogen and carbon monoxide are the most
plausible candidates because they are among the few substances volatile enough
to become gases at the very low temperatures of the outer solar system.
“This
discovery challenges our conventional view of small worlds in the outer solar system,” says Arimatsu. “Until now, clearly detectable atmospheres in the solar
system were essentially associated with planets, dwarf planets and some
large satellites. 2002 XV93 appears to be one of the smallest solar system
bodies yet with a clearly detected atmosphere.”
Souurse:
James Woodford 2026 Tiny frozen world unexpectedly appears to have an atmosphere | New Scientist 4 May
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