Proxima Centauri

Proxima Centauri is the nearest star to Earth after the Sun. It is located 4.25 light-years away in the southern constellation of Centaurus. This small, faint star was discovered in 1915 and is part of the Alpha Centauri star system.

Proxima Centauri is a red dwarf with a mass about 12.5% of the Sun's mass. Though it is very dim and hard to see without a telescope, it sometimes brightens suddenly due to magnetic activity. Because of its steady, slow burning of fuel, Proxima Centauri will continue shining for about four trillion years.

Scientists have found two planets orbiting Proxima Centauri. The closest, called Proxima Centauri b, lies in the star’s habitable zone, meaning it could possibly have liquid water. However, the star’s bright flares make this uncertain. Another smaller planet, Proxima Centauri d, orbits very close to the star. There may also be a third, more distant planet called Proxima Centauri c.

General characteristics

Proxima Centauri is a small, dim star known as a red dwarf. It is very faint and not visible to the naked eye. It shines with only a tiny fraction of the Sun’s brightness, mostly in infrared light.

This star is very dense, packing a lot of mass into a small space. It is about one-seventh the width of the Sun but has a very high density. Astronomers have measured its mass to be roughly 12% of the Sun’s mass, which is about 129 times the mass of Jupiter.

Structure and fusion

Proxima Centauri, being a small star, has its whole interior moving, which helps it share energy instead of letting it build up in one spot. This movement also creates a magnetic field that sometimes causes bright flashes called flares. These flares can become very hot and bright, but they only last for short moments.

Even when Proxima Centauri is quiet, it still has a lot of activity on its surface, more than the Sun does. This activity makes the star's outer layer very hot. Over time, this kind of star tends to calm down, and Proxima Centauri is already showing signs of this as it ages.

Life phases

Proxima Centauri, a small red dwarf star, will stay on its main sequence for about four trillion years. During this time, it will slowly become smaller and hotter, eventually turning into what is called a "blue dwarf." Near the end of this long period, it will become brighter, reaching about 2.5% of the Sun's luminosity and warming any planets that might orbit it for several billion years.

Eventually, Proxima Centauri will use up its hydrogen fuel and transform into a helium white dwarf without becoming a red giant first. It will then slowly cool down over time. Scientists think the Alpha Centauri system may have formed when a low-mass star like Proxima was captured by a more massive pair of stars. This could mean that Proxima and the other stars share similar elements. Its gravity might have also affected the early disks around the other stars, possibly bringing more water and other materials to any planets forming there.

Motion and location

Proxima Centauri is the closest star to the Sun, located about 4.25 light-years away. It moves quickly across the sky and is part of the Alpha Centauri system, which includes two other stars. From Earth, Proxima Centauri looks very faint because it is a small, cool star.

Proxima Centauri is often called Alpha Centauri C because it is connected to the Alpha Centauri binary star system. It orbits this system in a long, stretched path, coming close to the two main stars and then moving far away again. Together with several other stars, Proxima Centauri moves through space as part of a group that may have formed in the same place long ago.

Main article: Alpha Centauri

Planetary system

As of 2025, three planets have been found orbiting Proxima Centauri. One of these planets, called Proxima Centauri b, is about the size of Earth and lies in the habitable zone where liquid water might exist. Another possible planet, Proxima Centauri c, orbits much farther out and might be a gas dwarf. A third planet, Proxima Centauri d, is one of the smallest ever detected.

Scientists have been searching for planets around Proxima Centauri since the 1970s. In 2016, they confirmed the existence of Proxima Centauri b using special telescopes. They also found hints of other planets, but some discoveries are still being studied to make sure they are real.

Observational history

In 1915, the astronomer Robert Innes discovered a star that moved in the same way as Alpha Centauri. He named it Proxima Centauri. Later measurements showed that it was about the same distance from the Sun as Alpha Centauri. At the time, it was the dimmest star known.

Because Proxima Centauri is very faint, we need a telescope to see it. It is also a flare star, which means it sometimes suddenly shines much brighter. In 2016, scientists observed the biggest flare ever seen from this star. The New Horizons spacecraft also took pictures of Proxima Centauri in 2020, showing how its position appears to change from different viewpoints.

Future exploration

Because Proxima Centauri is the closest star to Earth after the Sun, it has been suggested as a destination for future space travel. Using current technology, a spacecraft would take thousands of years to reach Proxima Centauri. However, advanced ideas like nuclear pulse propulsion or special projects such as Breakthrough Starshot could make the trip in just a few centuries. These tiny space probes would travel at a fifth of the speed of light and could reach Proxima Centauri to take pictures and gather information about any planets there. It would still take over four years for that information to travel back to Earth.