Proxima Centauri is the dimmest and smallest of the Alpha Centauri system, but it has the honor of being the nearest star.
PROXIMA CENTAURI VITALS
Official name (IAU-approved) Proxima Centauri
Other Designations Alpha Centauri C, HIP 70890
Nicknames --
Apparent Magnitude 11.13
Distance from Earth 4.24 light-years
Type :M5.5
Color :Red
Mass :0.123 M☉
Radius :0.15 R☉
Constellation Centaurus
Right Ascension 14h 29m 43s
Declination -62° 40' 46”
Multiple system? Yes, third member of the Alpha Centauri system
Variable star? Yes, eruptive variable
Exoplanets status Two known exoplanets
Probable fate White dwarf
PHYSICAL CHARACTERISTICS:
Of all the stars in the universe — and there are untold billions of them — Proxima Centauri, a run-of-the-mill red dwarf star, is closest to the Sun. It’s about 14% the Sun’s diameter and located in the southern celestial sky.This graphic shows the relative sizes of several stars and Jupiter, including the three known members of the Alpha Centauri triple system. (The Sun is between Rigil Kentaurus and Toliman.)
ESO
But wait, you may be thinking, I thought Alpha Centauri was the closest star to the Sun. Well, that’s basically true, too. Even casual space enthusiasts are familiar with the name Alpha Centauri. Located a “mere” 4.35 light-years away, it’s indeed the closest of the Sun’s stellar neighbors, but this isn’t the whole story. Although Alpha Centauri appears to be a singleton to the unaided eye, closer inspection shows that it’s actually a system of three stars. Two of them, Alpha Centauri A and Bofficially named Rigil Kentaurus and Toliman, respectively), are a binary pair that are roughly the same size as the Sun. We see the combined light of these two stars when we’re looking at Alpha Centauri.But the third member of the group, separated from the other two by a considerable distance, is Alpha Centauri C — or as it’s officially known, Proxima Centauri. Proxima is about 4.24 light-years from our neighborhood, so it’s this stellar runt that currently holds the precise distinction of “closest.” Despite its proximity, Proxima is quite dim, partly because it outputs much of its energy at infrared wavelengths, which are invisible to human eyes.Proxima Centauri flare
This artist's conception of a powerful stellar flare from Proxima Centauri shows an accompanying coronal mass ejection that's sending material out into space. Such an ejection of particles likely accompanied a flare on May 1, 2019.
S. Dagnello / NRAO / AUI / NSF
But don’t be too cavalier with the word “close,” as the distances involved are here still astounding: Proxima is 40,208,000,000,000 km, or 268,770 astronomical units (a.u.), from us. Don’t make any vacation plans just yet!
Proxima is about 13,000 a.u. from its companions, circling them every 550,000 years in a slow and enormous orbit. The laws of celestial mechanics dictate that objects orbiting close to their parent star (Mercury, for example) travel faster than those orbiting at a great distance (like Neptune), so Proxima’s slow pace is a product of its vast distance.
Red dwarf stars are the most common type of star in the universe, so it’s not surprising to find Proxima (and Barnard’s Star) in our immediate vicinity. Proxima Centauri has a feisty personality, as it’s prone to occasional fiery outbursts of stellar flares, but it’s also an enduring star. Because of their small size, red dwarfs are cooler, and they don’t expend their fuel sources as rapidly as larger stars. So even though they have fewer atoms to fuse, the rate of consumption is so slow that these fuel sources can last a very long time. If Proxima Centauri continues its fusion at the current rate, it will continue shining for several trillion years!This artist’s impression shows what the sky might look like on Proxima Centauri b if the planet has a surface and an atmosphere.
ESO / M. Kornmesser
Proxima hosts two exoplanets: a rocky but likely airless world dubbed Proxima Centauri b, with a mass of about 1.27 Earths and an orbital period of just 11 days, and Proxima Centauri c, a world probably around the size of Neptune.A good chart is essential for identifying Proxima Centauri within the densely packed Milky Way star field.
Sky & Telescope:
It’s possible that future technology could allow for robotic exploration of nearby stars, and Proxima Centauri would make an interesting candidate. But you don’t have to wait for the future to start your own exploration of the nearby red dwarf. You just need the right location and — just as importantly — the right telescope.You’ll need to be south of roughly 30°N latitude to see Proxima. The further south you go, the higher the dim star rises out of the turbulent air near the horizon, and the easier it will be to see. So while it’s theoretically possible to see Proxima from southern U.S. mainland states like Florida or Texas, for stargazers in Australia, Central and South America, and parts of Africa and Asia, the view should be excellent.
Proxima can make for an interesting telescopic challenge, especially for experienced amateurs who are used to finding dim objects by “star-hopping.” The binary A and B pair are easy enough to split visually, but Proxima is separated a full 2° from Alpha Centauri AB, so it requires a bit of searching. How big will your telescope need to be? While local atmospheric and light pollution conditions will always play a factor, a 6-inch or larger reflector should be able to pull in the 11th-magnitude Proxima. This can be a great project for astrophotographers as well, who can better record the star’s red color.
Proxima may not look like much through your telescope, especially compared to the much brighter A and B stars, but it can be interesting to reach out and gather the light of this dim star that is so very far — but not that far — away. Have you ever spotted our nearest stellar neighbor?
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