Meet Proxima Centauri: The Closest Star

Proxima Centauri Vitals

Official title (IAU-approved) Proxima Centauri
Other Designations Alpha Centauri C, HIP 70890
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 standing Two identified exoplanets
Probable destiny White dwarf

Physical Characteristics

Of all of the stars within 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 situated within the southern celestial sky.

star sizes with Jupiter
This graphic exhibits the relative sizes of a number of stars and Jupiter, together with the three identified members of the Alpha Centauri triple system. (The Sun is between Rigil Kentaurus and Toliman.)

But wait, you could be pondering, I assumed Alpha Centauri was the closest star to the Sun. Well, that’s principally true, too. Even informal space fanatics are acquainted with the title Alpha Centauri. Located a “mere” 4.35 light-years away, it’s certainly the closest of the Sun’s stellar neighbors, however this isn’t the entire story. Although Alpha Centauri seems to be a singleton to the unaided eye, nearer inspection exhibits that it’s truly a system of three stars. Two of them, Alpha Centauri A and B (formally named Rigil Kentaurus and Toliman, respectively), are a binary pair which might be roughly the identical measurement because the Sun. We see the mixed gentle of those two stars after we’re Alpha Centauri.

But the third member of the group, separated from the opposite two by a substantial distance, is Alpha Centauri C — or because it’s formally identified, Proxima Centauri. Proxima is about 4.24 light-years from our neighborhood, so it’s this stellar runt that presently holds the exact distinction of “closest.” Despite its proximity, Proxima is kind of dim, partly as a result of it outputs a lot of its vitality at infrared wavelengths, that are invisible to human eyes.

Proxima Centauri flare
This artist’s conception of a strong stellar flare from Proxima Centauri exhibits an accompanying coronal mass ejection that is sending materials out into space. Such an ejection of particles possible accompanied a flare on May 1, 2019.
S. Dagnello / NRAO / AUI / NSF

But don’t be too cavalier with the phrase “close,” because the distances concerned are right here nonetheless astounding: Proxima is 40,208,000,000,000 km, or 268,770 astronomical models (a.u.), from us. Don’t make any trip plans simply but!

Proxima is about 13,000 a.u. from its companions, circling them each 550,000 years in a gradual and large orbit. The legal guidelines of celestial mechanics dictate that objects orbiting near their dad or mum star (Mercury, for instance) journey sooner than these orbiting at a terrific distance (like Neptune), so Proxima’s gradual tempo is a product of its huge distance.

Red dwarf stars are the commonest sort of star within the universe, so it’s not shocking to search out Proxima (and Barnard’s Star) in our rapid neighborhood. Proxima Centauri has a feisty character, because it’s susceptible to occasional fiery outbursts of stellar flares, however it’s additionally an everlasting star. Because of their small measurement, red dwarfs are cooler, they usually don’t expend their gas sources as quickly as bigger stars. So regardless that they’ve fewer atoms to fuse, the speed of consumption is so gradual that these gas sources can final a really very long time. If Proxima Centauri continues its fusion on the present fee, it is going to proceed shining for a number of trillion years!

illustration of Proxima Centauri b
This artist’s impression exhibits what the sky may appear like on Proxima Centauri b if the planet has a floor and an environment.
ESO / M. Kornmesser

Proxima hosts two exoplanets: a rocky however possible airless world dubbed Proxima Centauri b, with a mass of about 1.27 Earths and an orbital interval of simply 11 days, and Proxima Centauri c, a world most likely across the measurement of Neptune.

Origin / Mythology

No historic tradition would have been conscious of Proxima Centauri’s existence — the star is just too faint to see with out optical assist. But the Alpha Centauri system as an entire shines at 0.28 magnitude and is a significant part of the big Centaurus constellation — so there’s no scarcity of myths and legends surrounding Centaurus and Alpha Centauri specifically.

Greco-Roman traditions are answerable for the constellation’s trendy title and fundamental form — that of a mythological half horse/half man creature. The particular centaur depicted by the starry define might be a centaur named Chiron, a clever particular person and tutor of legendary heroes like Hercules, Achilles, Jason, and others.

Outside the Mediterranean, Alpha Centauri appeared in different constellations and myths. The Incan tradition of South America mixed a number of the darkish areas of the Milky Way’s Great Rift to kind a picture of a mom llama, with Alpha Centauri and Hadar (Beta Centauri) because the animal’s eyes (see the August 2021 issue of Sky & Telescope for extra of those fascinating “dark constellations”). Some Aboriginal Australian teams as a substitute noticed Alpha and Beta Centauri as sharks chasing a stingray, whereas some African traditions envisioned Alpha and Beta Centauri because the neck of a giraffe with the Southern Cross as its head. Native Hawaiians referred to as Alpha Centauri Kamaile Hope and used it and Hadar as tips that could the Southern Cross — a helpful trick stargazers nonetheless use at present.

Even although the utilitarian label Alpha Centauri has turn out to be the system’s widespread title, which means merely that it’s the brightest star of the Centaurus constellation, you’ll additionally see the first star known as Rigil Kentaurus. That’s an Arabic phrase, which means “foot of the centaur,” with related etymology to the extra acquainted Rigel that marks Orion’s left foot, and it’s now the star’s official title based on the International Astronomical Union. Alpha Centauri B’s official title is Toliman, one other conventional title for the system.

How to See Proxima Centauri

Proxima Centauri sky chart
A very good chart is important for figuring out Proxima Centauri throughout the densely packed Milky Way star subject.
Sky & Telescope

It’s potential that future technology might enable for robotic exploration of close by stars, and Proxima Centauri would make an attention-grabbing candidate. But you don’t have to attend for the longer term to begin your personal exploration of the close by red dwarf. You simply want the suitable location and — simply as importantly — the suitable telescope.

You’ll have to be south of roughly 30°N latitude to see Proxima. The additional south you go, the upper the dim star rises out of the turbulent air close to the horizon, and the better it will likely be to see. So whereas it’s theoretically potential to see Proxima from southern U.S. mainland states like Florida or Texas, for stargazers in Australia, Central and South America, and components of Africa and Asia, the view must be wonderful.

Proxima could make for an attention-grabbing telescopic problem, particularly for knowledgeable amateurs who’re used to discovering dim objects by “star-hopping.” The binary A and B pair are straightforward sufficient to separate visually, however Proxima is separated a full 2° from Alpha Centauri AB, so it requires a little bit of looking out. How huge will your telescope have to be? While native atmospheric and light-weight air pollution situations will at all times play an element, a 6-inch or bigger reflector ought to be capable to pull within the Eleventh-magnitude Proxima. This is usually a nice challenge for astrophotographers as effectively, who can higher file the star’s red colour.

Proxima might not appear like a lot via your telescope, particularly in comparison with the a lot brighter A and B stars, however it may be attention-grabbing to succeed in out and collect the sunshine of this dim star that’s so very far — however not that far — away. Have you ever noticed our nearest stellar neighbor?

Alpha and Beta Centauri function on this picture. Faint Proxima Centauri is circled in red.
Wikimedia Commons


Daniel Johnson is a Wisconsin-based freelance author {and professional} photographer and the co-author of over a dozen books. He’s a longtime beginner astronomer and lucky sufficient to reside in a rural area with wonderful seeing situations. You can view a few of Dan’s pictures (he does plenty of animals!) at

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart