Gliese 832 c facts for kids
An artist's impression of Gliese 832 c.
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| Orbital characteristics | |
|---|---|
| 0.162 (± 0.017) AU | |
| Eccentricity | 0.18 (± 0.13) |
| 35.68 (± 0.03) d | |
| Star | Gliese 832 |
| Physical characteristics | |
| Mass | ≥5.4 (± 1) M⊕ |
Gliese 832 c (also known as Gl 832 c or GJ 832 c) was once thought to be a planet orbiting a star called Gliese 832. This star is a red dwarf and is about 16.2 light-years away from us. It is located in the constellation of Grus.
For a while, scientists believed Gliese 832 c was a "super-Earth". This means it was bigger than Earth but smaller than planets like Neptune. They also thought it might be in its star's habitable zone. This is the area around a star where temperatures could be just right for liquid water to exist on a planet's surface.
However, in 2022, new studies showed that Gliese 832 c probably doesn't exist. The signals scientists saw were likely caused by activity on the star itself, not by a planet orbiting it. This is similar to how some other "planets" around red dwarfs were later found not to be real.
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What We Thought We Knew About Gliese 832 c
Even though Gliese 832 c is now thought not to exist, it's interesting to look at what scientists believed about it.
Size, Weight, and Temperature
Scientists thought Gliese 832 c was at least 5.4 times heavier than Earth. If it had a similar density to Earth, it would have been about 1.75 times wider than our planet.
The planet was thought to have an orbit that wasn't perfectly round. This meant its distance from its star changed a lot. Its average temperature was predicted to be about -20°C (-4°F). But because its orbit was not round, the temperature could change from -40°C (-40°F) when it was farthest from the star to 7°C (45°F) when it was closest.
Because it was thought to be so heavy, Gliese 832 c might have had a very thick atmosphere. This could have made it much hotter, perhaps even like Venus, which has a very hot, dense atmosphere.
Its Home Star
Gliese 832 c was thought to orbit a star called Gliese 832. This star is a red dwarf, which is a type of star smaller and cooler than our Sun. Gliese 832 has one other known planet, called Gliese 832 b.
Gliese 832 is about 0.45 times the mass of our Sun and 0.48 times its radius. Its temperature is around 3620 K (about 3347°C or 6056°F). For comparison, our Sun is about 4.6 billion years old and has a temperature of 5778 K (about 5505°C or 9941°F). Gliese 832 is much older, estimated to be about 9.54 billion years old.
From Earth, Gliese 832 appears quite dim. You can't see it without a telescope.
Its Orbit
Scientists believed Gliese 832 c completed one orbit around its star in about 36 days. This is much faster than Earth's year, which is about 365 days. The planet was thought to orbit much closer to its star than Earth orbits the Sun. Its distance from Gliese 832 was about 0.162 AU. To compare, Mercury, the closest planet to our Sun, orbits at about 0.389 AU.
Could It Have Supported Life?
Even though Gliese 832 c is now thought not to exist, the idea that a "super-Earth" could be in a star's habitable zone is exciting. The habitable zone is often called the "Goldilocks zone" because it's not too hot and not too cold for liquid water.
Gliese 832 is a red dwarf, so its habitable zone is much closer to the star than our Sun's habitable zone. Scientists thought Gliese 832 c received about the same amount of energy from its star as Earth gets from the Sun.
Stars like Gliese 832 can live for a very long time, up to 50-60 billion years. This is 5 to 6 times longer than our Sun will live. This long lifespan could give life a lot of time to develop if a planet were truly in its habitable zone.
Scientists also thought Gliese 832 c might be "tidally locked". This means one side of the planet would always face its star, like how the Moon always shows us the same side. One side would be in constant daylight, and the other in constant darkness. However, there might be a "terminator line" between these two sides. This is a narrow band where temperatures could be just right for liquid water. If the planet had a thick enough atmosphere, it could also spread heat to the dark side, making more of the planet habitable.
However, there was also a concern that Gliese 832 c might have been more like Venus. If it had a very thick atmosphere, it could have experienced a "runaway greenhouse effect". This is when a planet gets so hot that any oceans boil away, and the water vapor traps even more heat, making the planet incredibly hot. In this case, Gliese 832 c would have been a very hot, dry desert planet instead of an ocean planet.
Discovery and Doubts
Gliese 832 c was first announced in 2014 by a team of astronomers led by Robert A. Wittenmyer. At the time, it was considered one of the most Earth-like planets found and was added to the "Habitable Exoplanets Catalog." Its discoverers even called it "the nearest best habitable world candidate so far."
However, doubts about its existence started to appear in 2015. Scientists noticed that the signal they thought was from a planet might actually be from the star itself. In 2022, further studies confirmed this. The signal was caused by activity on the star Gliese 832, not by a planet orbiting it. This is similar to what happened with other supposed "super-Earths" around red dwarfs, like those around Gliese 581 and Kapteyn's Star, which were also later disproven.
See also
