Proxima Centauri, differently called Alpha Centauri C is a red dwarf, a small low-mass star, about 4.2 light-years from the Sun in the constellation of Centaurus.

This star is the nearest one to the sun, but as it is so small and dim we cannot see it with the naked eye.

The Scottish astronomer Robert Innes, the Director of the Union Observatory in South Africa, discovered it in 1915.

Astronomers measure its angular diameter directly, because of Proxima Centauri’s close distance to Earth. It is about one-seventh the diameter of the Sun. It has a mass about an eighth of our star’s mass, and its average density is about 40 times that of the Sun. Although it has a very low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness. That is because of the magnetic activity. Convection throughout the stellar body creates the star’s magnetic field. And the resulting flare activity generates a total X-ray emission similar to that produced by the Sun. The mixing of the fuel at Proxima Centauri’s core through convection and its relatively low energy-production rate mean that it will be a main-sequence star for another four trillion years or nearly 300 times the current age of the universe.

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. But the star is extremely distant from its two companions. It orbits 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.

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 Temperature

Astronomers estimate that Proxima Centauri might have surface temperatures of around 3000C (5400F), around 55% as hot as the sun.

About its Planet, Proxima Centauri b

In August 2016 scientists discovered that an Earth sized planet is 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.

Proxima Centauri b orbits the star at a distance of roughly 0.05 AU (7,500,000 km) with an orbital period of approximately 11.2 Earth days and has an estimated mass of at least 1.3 times that of the Earth.

Even though Proxima Centauri b is in the habitable zone, the planet’s habitability has been questioned. That’s because of several potentially hazardous physical conditions. The exoplanet is close enough to its host star that it might be tidally locked. In this case, expectations are that any habitable areas would be confined to the border region between the two extreme sides, generally referred to as the terminator line, since it is only here that temperatures might be suitable for liquid water to exist.

How was it discovered?

The European Southern Observatory announced the discovery of the planet in August 2016. The planet was found using the radial velocity method. A method where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object. From these readings, the radial velocity of the parent star relative to the Earth is varying with an amplitude of about 2 meters (7 feet) per second. According to Guillem Anglada‐Escudé, its proximity to Earth offers an opportunity for robotic exploration of the planet with the Starshot project or, at least, “in the coming centuries”.