Hidden in the constellation Libra, about 20 light-years from Earth, sitsGliese 581c。As one of the first super-Earth exoplanets (planets outside the solar system) to be discovered, this planet has caused quite a bit of speculation since it was discovered in 2007. Does it harbor life, or is it more like the scorching environment of Venus?
In 2007, the discovery of Gliese 581C was announced in the journal Astronomy and Astrophysics, thanks to the work of an international team led by Stephane Udry of the Geneva Observatory. The team detected Gliese 581c using the radial velocity method, which identifies planets by the slight gravitational drag they exert on the host star.
It's worth noting that the Gliese 581C is not alone. It is one of two super-Earth planets (planets 10 times the size of Earth) discovered by the UDRY team, both of which are located on the edge of the star's habitable zone. Researchers have called Gliese 581c "the most Earth-like exoplanet known" because it is only about five times more massive than Earth. As the first terrestrial planet to be discovered, Gliese 581c caused a great sensation when it was announced.
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Gliese 581c aroundGliese 581orbit, Gliese 581 is an m-class or red dwarf that is cooler than the Sun. Due to its lower temperatures, the habitable zone of Gliese 581 is closer than that of our solar system. The m-dwarf makes it easy to search for its planets because of its relative faintness, which makes it easier to spot planets that pass through the star. Gliese 581c is the third planet of its host star, Gliese 581. The other planets in this planetary system are Gliese 581b, Gliese 581d, and Gliese E.
Researchers rely on the planet's influence on other celestial bodies to infer their characteristics. Depending on the radius of the planet, Gliese 581c may resemble a terrestrial planet (with a smaller atmosphere) or a Neptune-like planet (with a thicker atmosphere).
Gliese 581c is very close to its star, causing it to orbit very fast, only orbiting in about 13 days, which could lead to tidal locking. This means that one side of the planet is always facing its star, while the other side is in perpetual darkness, which has a significant impact on its habitability.
Its actual surface temperature may be between 0 degrees Celsius and 40 degrees Celsius. Such a wide range is due to the fact that scientists (so far) have not detected the composition of the planet – either rock or water. The composition determines the temperature. Models of planetary orbits over time suggest that tide-locked heat could mean that the surface heat flux (the amount of thermal energy passing through a surface) is three times greater than that of Jupiter's moon Europa. This can mean that there are volcanoes and plate tectonics.
When Gliese 581c was first discovered, researchers were optimistic that it might be located in the habitable zone of the star, an area where liquid water may be present on the planet's surface. However, later studies suggest that the planet may be more similar to Venus in our solar system, with extremely high surface temperatures and runaway greenhouse effects under a thick atmosphere.
If the Gliese 581c is indeed tidally locked, this could also complicate the livability situation. Earth's regular day-night cycle has played an important role in the evolution and adaptation of life forms. On a planet that is always bathed in daylight on one side and darkness on the other, it is not clear how life will adapt.
The 2013 study also showed that its rocky center is unlikely to evolve into a terrestrial rock-like planet with a thin atmosphere (like the planets in our inner solar system). Instead, these planets tend to remain small rocky cores engulfed by large hydrogen-rich atmospheres. The rock surface is one of the requirements for livability.
In recent years, Gliese 581c has not been the focus of scientific research. The discovery of exoplanets or extrasolar planets (extrasolar planets) by the Kepler and Tess space telescopes has led to the discovery of many other "terrestrial" planets, some of which have masses closer to Earth.
Still, as future space missions dedicated to finding habitable planets continue, who knows what new insights we'll gain from Gliese 581c and other interesting worlds?