Astronomers unexpectedly find strange planetary system where day and night look exactly the same

Coconuts-2b is a gas giant six times the mass of Jupiter, and is orbiting a low-mass red dwarf star over nine hundred billion kilometres from it

Adam Smith
Monday 02 August 2021 07:54
Astronomers Capture Closet Ever Image of Nearby Exoplanet

Astronomers have uncovered a strange new planet only 35 light years from Earth where night and day look exactly the same.

The exoplanet, called Coconuts-2b, is a gas giant six times the mass of Jupiter and is orbiting a low-mass red dwarf star over nine hundred billion kilometres from it - 6000 times more than the relatively short 151.87 million kilometres between the Earth and the Sun.

Its wide orbit, and the low temperature of its red dwarf star, means that daytime looks almost the same as its night in its skies, with the star appearing as a bright red light.

The classification of Coconuts-2b, and the Coconut-2 system it is part of, was unexpected as it came from a graduate student from the University of Hawaii’s Institute for Astronomy, Zhoujian Zhang. Coconuts-2b was first detected in 2011 by the Wide-field Infrared Survey Explorer satellite, but it was thought to be a free-floating object rather than orbiting around a star.

Coconuts-2b is also bound to a low-mass star, called Coconuts-2a, which is has one-third of the mass of our Sun, and is 10 times younger than our four billion year-old Sun.

“With a massive planet on a super-wide-separation orbit, and with a very cool central star, Coconuts-2 represents a very different planetary system than our own solar system,” Zhang, who was aiming to find wide-separation companions around stars for his PhD thesis, said.

Coconuts-2b is the second-coldest exoplanet ever imaged at a temperature of only 160 degrees Celsius, and can only be detected using infrared light due to its low energy output. There is some residual heat from the planet that has been trapped since it was formed, but is still more than one million times weaker than that of our Sun.

“Directly detecting and studying the light from gas-giant planets around other stars is ordinarily very difficult, since the planets we find usually have small-separation orbits and thus are buried in the glare of their host star’s light,” said Michael Liu, Zhang’s thesis advisor.

“With its huge orbital separation, Coconuts-2b will be a great laboratory for studying the atmosphere and composition of a young gas-giant planet.”

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