Alpha Centauri

Alpha Centauri is the brightest object in the constellation of Centaurus (top left).
Apparent and true orbits of Alpha Centauri. The A component is held stationary, and the relative orbital motion of the B component is shown. The apparent orbit (thin ellipse) is the shape of the orbit as seen by an observer on Earth. The true orbit is the shape of the orbit viewed perpendicular to the plane of the orbital motion. According to the radial velocity versus time, the radial separation of A and B along the line of sight had reached a maximum in 2007, with B being further from Earth than A. The orbit is divided here into 80 points: each step refers to a timestep of approx. 0.99888 years or 364.84 days.
The relative sizes and colours of stars in the Alpha Centauri system, compared to the Sun
Relative positions of Sun, Alpha Centauri AB and Proxima Centauri. Grey dot is projection of Proxima Centauri, located at the same distance as Alpha Centauri AB.
The two bright stars at the lower right are Alpha (right) and Beta Centauri (left, above antenna). A line drawn through them points to the four bright stars of the Southern Cross, just to the right of the dome of the Danish 1.54 m telescope at La Silla Observatory in Chile.
Alpha Centauri AB taken in daylight by holding a Canon Powershot S100 in line with the eyepiece of a 110-mm refractor. The photo is one of the best frames of a video. The double star is clearly visible.
View of Alpha Centauri from the Digitized Sky Survey-2
Alpha Centauri A is of the same stellar type G2 as the Sun, while Alpha Centauri B is a K1-type star.
Closest stars to the Sun
Distances of the nearest stars from 20,000 years ago until 80,000 years in the future
Animation showing motion of Alpha Centauri through the sky. (The other stars are held fixed for didactic reasons) "Oggi" means today. "Anni" means years.
The discovery image of Alpha Centauri's candidate Neptunian planet, marked here as "C1".
Looking towards the sky around Orion from Alpha Centauri with Sirius near Betelgeuse, Procyon in Gemini, and the Sun in Cassiopeia generated by Celestia.
Simulated night-sky image with a "W" of stars from Cassiopeia connected by lines, and the Sun, labeled "Sol", as it would appear to the left of the "W"
The Very Large Telescope and Alpha Centauri

For other uses, see Alpha Centauri (disambiguation).

- Alpha Centauri
Alpha Centauri is the brightest object in the constellation of Centaurus (top left).

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Alpha

Arcturus is the brightest star in the constellation of Boötes.

Arcturus

Brightest star in the northern constellation of Boötes, the fourth-brightest in the night sky, and the brightest in the northern celestial hemisphere.

Brightest star in the northern constellation of Boötes, the fourth-brightest in the night sky, and the brightest in the northern celestial hemisphere.

Arcturus is the brightest star in the constellation of Boötes.
Optical image of Arcturus (DSS2 / MAST / STScI / NASA)
Arcturus in Arctophyllax
Arcturus next to the head of Comet Donati in 1858

With an apparent visual magnitude of −0.05, Arcturus is the brightest star in the northern celestial hemisphere and the fourth-brightest star in the night sky, after Sirius (−1.46 apparent magnitude), Canopus (−0.72) and α Centauri (combined magnitude of −0.27).

Animated 3D map of the nearest stars, centered on the Sun.

List of nearest stars and brown dwarfs

This list covers all known stars, brown dwarfs, and sub-brown dwarfs within 5.0 pc of the Solar System.

This list covers all known stars, brown dwarfs, and sub-brown dwarfs within 5.0 pc of the Solar System.

Animated 3D map of the nearest stars, centered on the Sun.
Distance and angle conformal map of the celestial neighbourhood within 12 light years of Sol.
Distances of the nearest stars from 20,000 years ago until 80,000 years in the future

The Local Bubble also contains the neighboring G-Cloud, which contains the stars Alpha Centauri and Altair.

Astronomers have mistakenly reported observations of a double star in place of J 900 and a faint star in the constellation of Gemini.

Double star

Pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes.

Pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes.

Astronomers have mistakenly reported observations of a double star in place of J 900 and a faint star in the constellation of Gemini.
Artist's impression of the discs around the young stars HK Tauri A and B.

Alpha Centauri

Thomas Henderson, c.1820s Scottish Astronomer Royal

Thomas Henderson (astronomer)

Thomas Henderson, c.1820s Scottish Astronomer Royal
1 Hillside Crescent, Edinburgh
Memorial to Thomas Henderson at the observatory on Calton Hill
The grave of Alexander James Adie, Greyfriars Kirkyard
Memorial or gravestone for Thomas Henderson in Greyfriars Kirkyard

Thomas Henderson FRSE FRS FRAS (28 December 1798 – 23 November 1844) was a Scottish astronomer and mathematician noted for being the first person to measure the distance to Alpha Centauri, the major component of the nearest stellar system to Earth, the first to determine the parallax of a fixed star, and for being the first Astronomer Royal for Scotland.

C. A. Jensen, Friedrich Wilhelm Bessel, 1839 (Ny Carlsberg Glyptotek)

Friedrich Bessel

German astronomer, mathematician, physicist, and geodesist.

German astronomer, mathematician, physicist, and geodesist.

C. A. Jensen, Friedrich Wilhelm Bessel, 1839 (Ny Carlsberg Glyptotek)
Königsberg Observatory in 1830. It was destroyed by bombing in the Second World War.
Tabulae Regiomontanae reductionum observationum astronomicarum ab anno 1750 usque ad annum 1850 computatae, 1830

Nearly at the same time Friedrich Georg Wilhelm Struve and Thomas Henderson measured the parallaxes of Vega and Alpha Centauri.

The smaller object is Gliese 229B, about 20 to 50 times the mass of Jupiter, orbiting the star Gliese 229. It is in the constellation Lepus, about 19 light-years from Earth.

Brown dwarf

Brown dwarfs are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, unlike a main-sequence star.

Brown dwarfs are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, unlike a main-sequence star.

The smaller object is Gliese 229B, about 20 to 50 times the mass of Jupiter, orbiting the star Gliese 229. It is in the constellation Lepus, about 19 light-years from Earth.
Planets, brown dwarfs, stars (not to scale)
An artistic concept of the brown dwarf around the star HD 29587, a companion known as HD 29587 b, and estimated to be about 55 Jupiter masses
A size comparison between the Sun, a young sub-brown dwarf, and Jupiter. As the sub-brown dwarf ages, it will gradually cool and shrink.
Artist's vision of a late-M dwarf
Artist's vision of an L dwarf
Artist's vision of a T dwarf
Artist's vision of a Y dwarf
WISE 0458+6434 is the first ultra-cool brown dwarf (green dot) discovered by WISE. The green and blue comes from infrared wavelengths mapped to visible colors.
Artist's illustration of a brown dwarf's interior structure. Cloud layers at certain depths are offset as a result of layer shifting.
Wind measured (Spitzer ST; Artist Concept; 9 Apr 2020)
Brown dwarfs Teide 1, Gliese 229B, and WISE 1828+2650 compared to red dwarf Gliese 229A, Jupiter and our Sun
Chandra image of LP 944-20 before flare and during flare
Multi-epoch images of brown dwarf binaries taken with the Hubble Space Telescope. The binary Luhman 16 AB (left) is closer to the Solar System than the other examples shown here.
A visualization representing a three-dimensional map of brown dwarfs (red dots) that have been discovered within 65 light-years of the Sun
The HH 1165 jet launched by the brown dwarf Mayrit 1701117 in the outer periphery of the sigma Orionis cluster
Artist's impression of a disc of dust and gas around a brown dwarf
Brown dwarf illustration<ref>{{cite web |first1=Megan |last1=Tannock |first2=Stanimir |last2=Metchev |first3=Amanda |last3=Kocz |title=Caught Speeding: Clocking the Fastest-Spinning Brown Dwarfs |url=https://noirlab.edu/public/news/noirlab2114/ |publisher=NOIRLab |date=7 April 2021 |access-date=9 April 2021 }}</ref>

Luhman 16 is the third closest system to the Sun after Alpha Centauri and Barnard's Star.

61 Cygni, a binary K-type star system.

K-type main-sequence star

Orange dwarf, is a main-sequence star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("red dwarfs") and yellow/white G-type main-sequence stars.

Orange dwarf, is a main-sequence star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("red dwarfs") and yellow/white G-type main-sequence stars.

61 Cygni, a binary K-type star system.

Well-known examples include Alpha Centauri B (K1 V) and Epsilon Indi (K5 V).

The constellation Crux

Acrux

Brightest star in the southern constellation of Crux.

Brightest star in the southern constellation of Crux.

The constellation Crux
α Crucis with the nearby HD 108250

It is the most southerly star of the asterism known as the Southern Cross and is the southernmost first-magnitude star, 2.3 degrees more southerly than Alpha Centauri.

Star system named DI Cha. While only two stars are apparent, it is actually a quadruple system containing two sets of binary stars.

Star system

Small number of stars that orbit each other, bound by gravitational attraction.

Small number of stars that orbit each other, bound by gravitational attraction.

Star system named DI Cha. While only two stars are apparent, it is actually a quadruple system containing two sets of binary stars.
Orbits of the HR 6819 hierarchical triple star system: an inner binary with one star (orbit in blue) and a black hole (orbit in red), encircled by another star in a wider orbit (also in blue).
Subsystem notation in Tokovinin's Multiple Star Catalogue
Sirius A (center), with its white dwarf companion, Sirius B (lower left) taken by the Hubble Space Telescope.
HD 98800 is a quadruple star system located in the TW Hydrae association.

Alpha Centauri is a triple star composed of a main binary yellow dwarf pair (Alpha Centauri A and Alpha Centauri B), and an outlying red dwarf, Proxima Centauri. Together, A and B form a physical binary star, designated as Alpha Centauri AB, α Cen AB, or RHD 1 AB, where the AB denotes this is a binary system. The moderately eccentric orbit of the binary can make the components be as close as 11 AU or as far away as 36 AU. Proxima Centauri, also (though less frequently) called Alpha Centauri C, is much farther away (between 4300 and 13,000 AU) from α Cen AB, and orbits the central pair with a period of 547,000 (+66,000/-40,000) years.

On 24 August 2016, ESO hosted a press conference to discuss the announcement of exoplanet Proxima b at its headquarters in Germany. In this picture, Pete Worden giving a speech.

Breakthrough Starshot

On 24 August 2016, ESO hosted a press conference to discuss the announcement of exoplanet Proxima b at its headquarters in Germany. In this picture, Pete Worden giving a speech.
A solar sail concept

Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail interstellar probes named Starchip, to be capable of making the journey to the Alpha Centauri star system 4.37 light-years away.