At 4.2 light years away Proxima Centauri is the nearest star to the sun, but as it is so small and dim it cannot be viewed with the naked eye.
The star can be found in the Centaurus constellation, a centaur is a Greek mythological half man half horse creature, proxima is Latin for next or nearest.
The red dwarf Proxima Centauri is part of the three star Alpha Centauri system, the other two stars, Alpha Centauri A and B, are similar to our own sun.
Proxima Centauri is extremely distant from its two companions, orbiting them at a distance of around 1.2 trillion miles (1.9 trillion km).
Stars like our sun exist for a few billion years, red dwarfs like Proxima Centauri burn their fuel at a much lower rate and can therefore exist far longer.
In August 2016 it was announced that an Earth sized planet had been discovered orbiting the habitable zone around Proxima Centauri, the planet named Proxima b could possibly have liquid water on its surface.
Proxima b is the closest known planet outside our solar system.
The star Proxima Centauri was discovered in 1915 by the Scottish born astronomer Robert Innes.
Proxima Centauri Radius
Proxima Centauri is a very small red dwarf with a radius of around 60,000 miles (97,000 km), which is around 14% the size of our sun.
Proxima Centauri Mass
Proxima Centauri is estimated to have a mass of around 12% of that of the sun.
Proxima Centauri Temperature
Proxima Centauri is estimated to have surface temperatures of around 3000C (5400F), around 55% as hot as the sun.
Proxima Centauri Luminosity (energy emitted)
Red dwarfs emit far less energy than larger stars, its luminosity is less than one percent of that of our sun.
Proxima Centauri Statistics
Also Known As: Alpha Centauri C
Distance From Earth: 4.2 light years
Constellation: Centaurus
Star Type: Red Dwarf - M Class
Mass: 12% of the Sun
Luminosity: 0.17% of the Sun
Diameter: 120,000 miles (193,000 km) - 14% of the Sun
Temperature: Approx 3,000C (5,400F)
Age: Approx 5 billion years old
Rotation Period: 84 days
The sun's closest stellar neighbors are three stars in the Alpha Centauri system. The two main stars are Alpha Centauri A and Alpha Centauri B, which form a binary pair. They are an average of 4.3 light-years from Earth. The third star is Proxima Centauri. It is about 4.22 light-years from Earth and is the closest star other than the sun.
Alpha Centauri A and B orbit a common center of gravity every 80 years. The average distance between them is about 11 astronomical units (AU) — about the same distance as the sun is to Uranus. Proxima Centauri is about one-fifth of a light-year or 13,000 AUs from the two other stars, a distance that makes some astronomers question whether it should be considered part of the same system.
Proxima Centauri may be passing through the system and will leave the vicinity in several million years, or it may be gravitationally bound to the binary pair. If it's bound, it has an orbital period around the other two of about 500,000 years.
The planet is also in the star's habitable zone, that just-right range of distances where liquid water can exist. Proxima b lies just 4.7 million miles (7.5 million kilometers) from its host star and completes one orbit every 11.2 Earth-days. As a result, it's likely that the exoplanet is tidally locked, meaning it always shows the same face to its host star, just as the moon shows only one face (the near side) to Earth.
However, it's unclear just how habitable Proxima b is from today's telescopes. This means that astronomers need to run models and do comparative studies to better understand how habitable the planet might be. As a start, the planet needs a closer look for investigators to look for signs of an atmosphere. From there, the investigators can extrapolate if that atmosphere (if present) allows liquid water to flow on the surface. Even the surface temperature of the planet depends on the atmosphere, which would also play into habitability characteristics.
Because Proxima b is so close to a red dwarf, habitability problems are already coming to scientists' minds. For one thing, the planet is so close that it likely is tidally locked to the star, meaning that one side of the planet is always facing the star. This means one side of the planet would be very warm, while the opposite side would be very cold – unless winds could distribute the heat around the planet. That makes it hard for life to exist.
But the planet's close distance to the red dwarf presents other problems too. Red dwarfs are unstable stars, particularly when they are young – they have a lot of stellar activity and produce charged particles, which can produce intense radiation on nearby planets. Some of this radiation can strip molecules off the top of a planet's atmosphere and thin it over time, according to 2017 studies led by the NASA Goddard Space Flight Center in Greenbelt, Maryland.
Binary stars
To the naked eye, the two main stars shine as one, making them the third brightest "star" in our night sky. The two separate stars can be seen through a small telescope; one of the finest binary stars that can be observed. Proxima Centauri is too faint to see unaided, and through a telescope it appears about four diameters of the full moon away from the other two. [Infographic: The Nearest Stars to Earth]
By itself, Alpha Centauri A, also known as Rigel Kentaurus, is the third brightest star in the night sky; just a bit dimmer, by 0.02 of a magnitude, than Arcturus. It is a yellow star of the same type (G2) as the sun, and it is about 25 percent larger. Alpha Centauri B is an orange K2-type star, slightly smaller than the sun. Proxima Centauri is a red dwarf about seven times smaller than the sun, or one-and-a-half times bigger than Jupiter. All three stars are a bit older — 4.85 billion years old — than the sun, which is about 4.6 billion years old. Alpha Centauri Stars & Planet Explained: Our Nearest Neighbors.
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