Proxima Centauri

From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the star in the Alpha Centauri system. For other uses, see Proxima Centauri (disambiguation).

Coordinates: Sky map 14h 29m 42.9487s, −62° 40′ 46.141″

Proxima Centauri
New shot of Proxima Centauri, our nearest neighbour.jpg
Proxima Centauri as seen by Hubble
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Centaurus
Pronunciation /ˈprɒksɪmə sɛnˈtɔr/[nb 1]
Right ascension 14h 29m 42.9487s[1]
Declination −62° 40′ 46.141″[1]
Apparent magnitude (V) 11.05[1]
Characteristics
Spectral type M5.5 Ve[1]
Apparent magnitude (J) 5.35 ± 0.02[1]
U−B color index 1.43[1]
B−V color index 1.90[1]
Variable type Flare star
Astrometry
Radial velocity (Rv) −21.7 ± 1.8[2] km/s
Proper motion (μ) RA: −3775.40[1] mas/yr
Dec.: 769.33[1] mas/yr
Parallax (π) 768.7 ± 0.3[3] mas
Distance 4.243 ± 0.002 ly
(1.3009 ± 0.0005 pc)
Absolute magnitude (MV) 15.49[4]
Details
Mass 0.123 ± 0.006[5] M
Radius 0.141 ± 0.007[6] R
Luminosity (bolometric) 0.0017[7] L
Surface gravity (log g) 5.20 ± 0.23[5] cgs
Temperature 3,042 ± 117[5] K
Metallicity [Fe/H] 0.21[8] dex
Rotation 83.5 days[9]
Rotational velocity (v sin i) < 0.09[10] km/s
Age 4.85[11] Gyr
Other designations
Alpha Centauri C, CCDM J14396-6050C, GCTP 3278.00, GJ 551, HIP 70890, LFT 1110, LHS 49, LPM 526, LTT 5721, NLTT 37460, V645 Centauri[1]
Database references
SIMBAD data

Proxima Centauri (Latin proxima, meaning "next to" or "nearest to")[12] is a red dwarf about 4.24 light-years from the Sun, inside the G-cloud, in the constellation of Centaurus.[13][14] It was discovered in 1915 by the Scottish astronomer Robert Innes, the Director of the Union Observatory in South Africa, and is the nearest known star to the Sun,[11] although it is too faint to be seen with the naked eye, with an apparent magnitude of 11.05. Its distance to the second- and third-nearest stars, which form the bright binary Alpha Centauri, is 0.237 ± 0.011 ly (15,000 ± 700 AU).[15] Proxima Centauri is very likely part of a triple star system with Alpha Centauri A and B, but its orbital period may be greater than 500,000 years.

Because of Proxima Centauri's proximity, its distance from Earth and angular diameter can be measured directly, from which it can be determined that its diameter is about one-seventh of that of the Sun.[11] Proxima Centauri's mass is about an eighth of the Sun's (M), and its average density is about 40 times that of the Sun.[nb 2] Although it has a very low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness because of magnetic activity.[16] The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun.[17] 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,[18] or nearly 300 times the current age of the universe.[19]

Searches for companions orbiting Proxima Centauri have been unsuccessful, ruling out the presence of brown dwarfs and supermassive planets.[20][21] Precision radial velocity surveys have also ruled out the presence of super-Earths within the star's habitable zone.[22][nb 3] The detection of smaller objects will require the use of new instruments, such as the James Webb Space Telescope, which is scheduled for deployment in 2018.[23] Because Proxima Centauri is a red dwarf and a flare star, whether a planet orbiting it could support life is disputed.[24][25] Nevertheless, because of the star's proximity to Earth, it has been proposed as a destination for interstellar travel.[26]

Observation[edit]

In 1915, the Scottish astronomer Robert Innes, Director of the Union Observatory in Johannesburg, South Africa, discovered a star that had the same proper motion as Alpha Centauri.[27][28][29][30] He suggested it be named Proxima Centauri[31] (actually Proxima Centaurus).[32] In 1917, at the Royal Observatory at the Cape of Good Hope, the Dutch astronomer Joan Voûte measured the star's trigonometric parallax at 0.755 ± 0.028″ and determined that Proxima Centauri was approximately the same distance from the Sun as Alpha Centauri. It was also found to be the lowest-luminosity star known at the time.[33] An equally accurate parallax determination of Proxima Centauri was made by American astronomer Harold L. Alden in 1928, who confirmed Innes's view that it is closer, with a parallax of 0.783 ± 0.005″.[28][31]

Stars closest to the Sun, including Proxima Centauri (April 25, 2014).[34]

In 1951, American astronomer Harlow Shapley announced that Proxima Centauri is a flare star. Examination of past photographic records showed that the star displayed a measurable increase in magnitude on about 8% of the images, making it the most active flare star then known.[35][36] The proximity of the star allows for detailed observation of its flare activity. In 1980, the Einstein Observatory produced a detailed X-ray energy curve of a stellar flare on Proxima Centauri. Further observations of flare activity were made with the EXOSAT and ROSAT satellites, and the X-ray emissions of smaller, solar-like flares were observed by the Japanese ASCA satellite in 1995.[37] Proxima Centauri has since been the subject of study by most X-ray observatories, including XMM-Newton and Chandra.[38]

Because of Proxima Centauri's southern declination, it can only be viewed south of latitude 27° N.[nb 4] Red dwarfs such as Proxima Centauri are far too faint to be seen with the naked eye. Even from Alpha Centauri A or B, Proxima would only be seen as a fifth magnitude star.[39][40] It has an apparent visual magnitude of 11, so a telescope with an aperture of at least 8 cm (3.1 in.) is needed to observe it, even under ideal viewing conditions—under clear, dark skies with Proxima Centauri well above the horizon.[41]

Characteristics[edit]

Proxima Centauri is a red dwarf, because it belongs to the main sequence on the Hertzsprung–Russell diagram and is of spectral class M5.5. M5.5 means that it falls in the low-mass end of M-type stars.[11] Its absolute visual magnitude, or its visual magnitude as viewed from a distance of 10 parsecs, is 15.5.[4] Its total luminosity over all wavelengths is 0.17% that of the Sun,[7] although when observed in the wavelengths of visible light the eye is most sensitive to, it is only 0.0056% as luminous as the Sun.[42] More than 85% of its radiated power is at infrared wavelengths.[43]

This illustration shows the comparative sizes of (from left to right) the Sun, α Centauri A, α Centauri B, and Proxima Centauri
The two bright stars are (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri.

In 2002, optical interferometry with the Very Large Telescope (VLTI) found that the angular diameter of Proxima Centauri was 1.02 ± 0.08 milliarcsec. Because its distance is known, the actual diameter of Proxima Centauri can be calculated to be about 1/7 that of the Sun, or 1.5 times that of Jupiter. The star's estimated mass is 12.3% M, or 129 Jupiter masses (MJ).[44] The mean density of a main-sequence star increases with decreasing mass,[45] and Proxima Centauri is no exception: it has a mean density of 56.8 × 103 kg/m3 (56.8 g/cm3), compared with the Sun's mean density of 1.411 × 103 kg/m3 (1.411 g/cm3).[nb 2]

Because of its low mass, the interior of the star is completely convective, causing energy to be transferred to the exterior by the physical movement of plasma rather than through radiative processes. This convection means that the helium ash left over from the thermonuclear fusion of hydrogen does not accumulate at the core, but is instead circulated throughout the star. Unlike the Sun, which will only burn through about 10% of its total hydrogen supply before leaving the main sequence, Proxima Centauri will consume nearly all of its fuel before the fusion of hydrogen comes to an end.[18]

Convection is associated with the generation and persistence of a magnetic field. The magnetic energy from this field is released at the surface through stellar flares that briefly increase the overall luminosity of the star. These flares can grow as large as the star and reach temperatures measured as high as 27 million K[38]—hot enough to radiate X-rays.[46] Indeed, Proxima Centauri's quiescent X-ray luminosity, approximately (4–16) × 1026 erg/s ((4–16) × 1019 W), is roughly equal to that of the much larger Sun. The peak X-ray luminosity of the largest flares can reach 1028 erg/s (1021 W.)[38]

Proxima Centauri's chromosphere is active, and its spectrum displays a strong emission line of singly ionized magnesium at a wavelength of 280 nm.[47] About 88% of the surface of Proxima Centauri may be active, a percentage that is much higher than that of the Sun even at the peak of the solar cycle. Even during quiescent periods with few or no flares, this activity increases the corona temperature of Proxima Centauri to 3.5 million K, compared to the 2 million K of the Sun's corona.[48] However, Proxima Centauri's overall activity level is considered low compared to other red dwarfs,[17] which is consistent with the star's estimated age of 4.85 × 109 years,[11] since the activity level of a red dwarf is expected to steadily wane over billions of years as its stellar rotation rate decreases.[49] The activity level also appears to vary with a period of roughly 442 days, which is shorter than the solar cycle of 11 years.[50]

Proxima Centauri has a relatively weak stellar wind, resulting in no more than a 20% M mass loss rate from the solar wind. Because the star is much smaller than the Sun, however, the mass loss per unit surface area from Proxima Centauri may be eight times that from the solar surface.[51]

A red dwarf with the mass of Proxima Centauri will remain on the main sequence for about four trillion years. As the proportion of helium increases because of hydrogen fusion, the star will become smaller and hotter, gradually transforming from red to blue. Near the end of this period it will become significantly more luminous, reaching 2.5% of the Sun's luminosity (L) and warming up any orbiting bodies for a period of several billion years. Once the hydrogen fuel is exhausted, Proxima Centauri will then evolve into a white dwarf (without passing through the red giant phase) and steadily lose any remaining heat energy.[18]

Distance and motion[edit]

Based on the parallax of 768.7 ± 0.3 milliarcseconds, measured using the Hipparcos astrometry satellite,[52] and more precisely with the Fine Guidance Sensors on the Hubble Space Telescope,[3] Proxima Centauri is about 4.24 light years from the Sun, or 270,000 times more distant than Earth is from the Sun. From Earth's vantage point, Proxima is separated by 2.18°[53] from Alpha Centauri, or four times the angular diameter of the full Moon.[54] Proxima also has a relatively large proper motion—moving 3.85 arcseconds per year across the sky.[55] It has a radial velocity toward the Sun of 21.7 km/s.[1]

Distances of the nearest stars from 20,000 years ago until 80,000 years in the future. Proxima Centauri is in yellow

Among the known stars, Proxima Centauri has been the closest star to the Sun for about 32,000 years and will be so for about another 33,000 years, after which the closest star to the Sun will be Ross 248.[56] In 2001, J. García-Sánchez et al. predicted that Proxima will make its closest approach to the Sun, coming within 3.11 light years of the latter, in approximately 26,700 years.[2] A 2010 study by V. V. Bobylev predicted a closest approach distance of 2.90 ly in about 27,400 years.[57] Proxima Centauri is orbiting through the Milky Way at a distance from the Galactic Center that varies from 8.3 to 9.5 kpc, with an orbital eccentricity of 0.07.[58]

Ever since the discovery of Proxima it has been suspected to be a true companion of the Alpha Centauri binary star system. At a distance to Alpha Centauri of just 0.21 ly (15,000 ± 700 astronomical units [AU]),[15] Proxima Centauri may be in orbit around Alpha Centauri, with an orbital period of the order of 500,000 years or more. For this reason, Proxima is sometimes referred to as Alpha Centauri C. Modern estimates, taking into account the small separation between and relative velocity of the stars, suggest that the chance of the observed alignment being a coincidence is roughly one in a million.[59] Data from the Hipparcos satellite, combined with ground-based observations, is consistent with the hypothesis that the three stars are truly a bound system. If so, Proxima would currently be near apastron, the farthest point in its orbit from the Alpha Centauri system. Such a triple system can form naturally through a low-mass star being dynamically captured by a more massive binary of 1.5–2 M within their embedded star cluster before the cluster disperses.[60] More accurate measurement of the radial velocity is needed to confirm this hypothesis.[15]

If Proxima was bound to the Alpha Centauri system during its formation, the stars would be likely to share the same elemental composition. The gravitational influence of Proxima may also have stirred up the Alpha Centauri protoplanetary disks. This would have increased the delivery of volatiles such as water to the dry inner regions. Any terrestrial planets in the system may have been enriched by this material.[15]

Six single stars, two binary star systems, and a triple star share a common motion through space with Proxima Centauri and the Alpha Centauri system. The space velocities of these stars are all within 10 km/s of Alpha Centauri's peculiar motion. Thus, they may form a moving group of stars, which would indicate a common point of origin,[61] such as in a star cluster. If it is determined that Proxima Centauri is not gravitationally bound to Alpha Centauri, then such a moving group would help explain their relatively close proximity.[62]

Though Proxima Centauri is the nearest bona fide star, it is still possible that one or more as-yet undetected sub-stellar brown dwarfs may lie closer.[63][needs update]

Proxima Centauri distance estimates

Source Parallax, mas Distance, pc Distance, ly Distance, Pm Ref.
Voûte (1917) 755±28 1.32±0.05 4.32+0.17
−0.15
40.9+1.6
−1.5
[32][33]
Innes (1917) ~ 784 ~ 1.3 ~ 4.2 ~ 39.4 [32]
Alden (1928) 783±5 1.277±0.008 4.165+0.027
−0.026
39.41±0.25 [31]
Woolley et al. (1970) 761±5 1.314±0.009 4.286±0.028 40.55+0.27
−0.26
[64]
Gliese & Jahreiß (1991) 771.8±4.1 1.296±0.007 4.226+0.023
−0.022
39.98±0.21 [65]
van Altena et al. (1995) 769.8±6.1 1.299±0.01 4.24±0.03 40.08±0.32 [66]
Perryman et al. (1997) (Hipparcos) 772.33±2.42 1.295±0.004 4.223±0.013 39.95+0.13
−0.12
[67]
Perryman et al. (1997) (Tycho) (absents) [68]
Benedict et al. (1999) 768.7±0.3 1.3009±0.0005 4.243±0.0017 40.142±0.016 [3]
Henry et al. (2004) 1.17±0.19 3.82±0.62 [69]
Jao et al. (2005) 774.25±2.08 1.292±0.003 4.213±0.011 39.85±0.11 [70]
van Leeuwen (2007) 771.64±2.60 1.296±0.004 4.227±0.014 39.99+0.14
−0.13
[71]
RECONS TOP100 (2012) 768.85±0.29[nb 5] 1.3006±0.0005 4.2421±0.0016 40.134±0.015 [72]
Lurie et al. (2014) 768.13±1.04 1.3019±0.0018 4.246±0.006 40.17±0.05 [73]

Non-trigonometric distance estimates are marked in italic. The most precise estimate is marked in bold.

Possible companions[edit]

RV-derived upper mass limits of hypothetical companion[22]
Orbital
period

(days)
Separation
(AU)
Maximum
mass[nb 3]
(× Earth)
3.6–13.8 0.022–0.054 2–3
<100 <0.21 8.5
<1000 <1 16

If a massive planet is orbiting Proxima Centauri, it would cause some displacement of Proxima Centauri over the course of the planet's orbit. If the orbital plane of the planet is not perpendicular to the line of sight from Earth, then this displacement would cause periodic changes in the radial velocity of Proxima Centauri. The fact that multiple measurements of the star's radial velocity have detected no such shifts has lowered the maximum mass that a possible companion to Proxima Centauri could possess.[3][20] The activity level of the star adds noise to the radial velocity measurements, limiting future prospects for detection of a companion using this method.[74]

In 1998, an examination of Proxima Centauri using the Faint Object Spectrograph on board the Hubble Space Telescope appeared to show evidence of a companion orbiting at a distance of about 0.5 AU.[75] However, a subsequent search using the Wide Field Planetary Camera 2 failed to locate any companions.[21] Proxima Centauri, along with Alpha Centauri A and B, was among the "Tier 1" target stars for NASA's now-canceled Space Interferometry Mission (SIM), which would theoretically have been able to detect planets as small as three Earth-masses (M) within two AU of a "Tier 1" target star.[23]

Habitable zone[edit]

The TV documentary Alien Worlds hypothesized that a life-sustaining planet could exist in orbit around Proxima Centauri or other red dwarfs. Such a planet would lie within the habitable zone of Proxima Centauri, about 0.023–0.054 AU from the star, and would have an orbital period of 3.6–14 days.[76] A planet orbiting within this zone will experience tidal locking to the star, so that Proxima Centauri moves little in the planet's sky, and most of the surface experiences either day or night perpetually. However, the presence of an atmosphere could serve to redistribute the energy from the star-lit side to the far side of the planet.[24]

Proxima Centauri's flare outbursts could erode the atmosphere of any planet in its habitable zone, but the documentary's scientists thought that this obstacle could be overcome (see continued theories). Gibor Basri of the University of California, Berkeley, even mentioned that "no one [has] found any showstoppers to habitability." For example, one concern was that the torrents of charged particles from the star's flares could strip the atmosphere off any nearby planet. However, if the planet had a strong magnetic field, the field would deflect the particles from the atmosphere; even the slow rotation of a tidally locked dwarf planet that spins once for every time it orbits its star would be enough to generate a magnetic field, as long as part of the planet's interior remained molten.[77]

Other scientists, especially proponents of the Rare Earth hypothesis,[78] disagree that red dwarfs can sustain life. The tide-locked rotation may result in a relatively weak planetary magnetic moment, leading to strong atmospheric erosion by coronal mass ejections from Proxima Centauri.[25]

Brightest and nearest stars from Proxima Centauri[edit]

The following is a list of the 10 brightest and nearest known stars to Proxima Centauri, generated by the program Celestia. Some values may be outdated, as Celestia has not been updated since 2011.

Nearest[edit]

Star Apparent mag. Apparent mag. from Earth Distance (2015) Spectral type
Alpha Centauri A −6.63 0.01 0.2051 G2V
Alpha Centauri B −5.30 1.33 0.2048 K1V
Luhman 16 A 14.7 16 3.52 L7.5
Luhman 16 B 19.7 21 3.52 T0.5
Sun 0.40 −26.74 4.242 G2V
Barnard's Star 9.77 9.511 6.569 M4V
WISE 0855-0714 30.1 30 8.019 Y
Ross 154 10.09 10.44 8.218 M3.5V
Wolf 359 13.65 13.54 8.231 M6.5 Ve
SCR 1845-6357 A 16.68 17.4 9.021 M8.5

Brightest[edit]

Star Apparent mag. Apparent mag. from Earth Distance (2015) Spectral type
Alpha Centauri A −6.63 0.01 0.2051 G2V
Alpha Centauri B −5.30 1.33 0.2048 K1V
Sirius A −1.25 −1.47 9.336 A1V
Canopus −0.63 −0.74 306.8 F0II
Arcturus −0.07 −0.04 36.36 KOIII
Rigel 0.19 0.13 863.8 B8 lae
Vega 0.19 0.03 26.97 A0Va
Capella Ab 0.24 0.76 46.57 G1III
Capella Aa 0.26 0.91 46.57 K0III
Sun 0.40 −26.74 4.242 G2V

Interstellar travel[edit]

The Sun as seen from the Alpha Centauri system, using Celestia

Proxima Centauri has been suggested as a possible first destination for interstellar travel.[26] The star is in motion toward Earth at a rate of 21.7 km/s.[1] Ηowever, after 26,700 years, when it will come as close as 3.11 light-years, it will begin to move farther away.[2] If non-nuclear propulsion were used, a voyage of a spacecraft to a planet orbiting Proxima Centauri would probably require thousands of years.[79] For example, Voyager 1, which is now travelling 17.043 km/s (38,120 mph) relative to the Sun, would reach Proxima in 73,775 years, were the spacecraft traveling in the direction of that star. A slow-moving probe would have only several tens of thousands of years to catch Proxima Centauri near its closest approach, and could end up watching it recede into the distance.[80] Nuclear pulse propulsion might enable such interstellar travel with a trip timescale of a century, beginning within the next century, inspiring several studies such as Project Orion, Project Daedalus, and Project Longshot.[80]

From Proxima Centauri, the Sun would appear as a bright 0.4-magnitude star in the constellation Cassiopeia.[81]

See also[edit]

References[edit]

Explanatory notes[edit]

  1. ^ Proxima is pronounced /ˈprɒksɪmə/. Centauri may be pronounced /sɛnˈtɔriː/ or /sɛnˈtɔraɪ/.
  2. ^ a b The density (ρ) is given by the mass divided by the volume. Relative to the Sun, therefore, the density is:
    \rho = \begin{smallmatrix}\frac{M}{M_{\odot}} \cdot \left( \frac{R}{R_{\odot}} \right)^{-3} \cdot \rho_{\odot}\end{smallmatrix}
    = 0.123 · 0.145−3 · 1.41 × 103 kg/m3
    = 40.3 · 1.41 × 103 kg/m3
    = 5.68 × 104 kg/m3

    where \begin{smallmatrix}\rho_{\odot}\end{smallmatrix} is the average solar density. See:

    • Munsell, Kirk; Smith, Harman; Davis, Phil; Harvey, Samantha (June 11, 2008). "Sun: Facts & Figures". Solar System Exploration. NASA. Retrieved July 12, 2008. 
    • Bergman, Marcel W.; Clark, T. Alan; Wilson, William J. F. (2007). Observing Projects Using Starry Night Enthusiast (8th ed.). Macmillan. pp. 220–221. ISBN 1-4292-0074-X. 
  3. ^ a b This is actually an upper limit on the quantity m sin i, where i is the angle between the orbit normal and the line of sight, in a circular orbit. If the planetary orbits are close to face-on as observed from Earth, or in an eccentric orbit, more massive planets could have evaded detection by the radial velocity method.
  4. ^ For a star south of the zenith, the angle to the zenith is equal to the Latitude minus the Declination. The star is hidden from sight when the zenith angle is 90° or more, i.e. below the horizon. Thus, for Proxima Centauri:
    Highest latitude = 90° + −62.68° = 27.32°.
    See: Campbell, William Wallace (1899). The Elements of Practical Astronomy. London: Macmillan. pp. 109–110. Retrieved August 12, 2008. 
  5. ^ Weighted parallax based on parallaxes from van Altena et al. (1995), Benedict et al. (1999), Jao et al. (2005) and van Leeuwen (2007).

Citations[edit]

  1. ^ a b c d e f g h i j k l "SIMBAD query result: V* V645 Cen – Flare Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved August 11, 2008. —some of the data is located under "Measurements".
  2. ^ a b c García-Sánchez, J.; Weissman, P. R.; Preston, R. A.; Jones, D. L.; Lestrade, J.-F.; Latham, D. W.; Stefanik, R. P.; Paredes, J. M. (2001). "Stellar encounters with the solar system". Astronomy and Astrophysics 379 (2): 634–659. Bibcode:2001A&A...379..634G. doi:10.1051/0004-6361:20011330. 
  3. ^ a b c d Benedict, G. Fritz et al. (1999). "Interferometric Astrometry of Proxima Centauri and Barnard's Star Using HUBBLE SPACE TELESCOPE Fine Guidance Sensor 3: Detection Limits for Substellar Companions". The Astronomical Journal 118 (2): 1086–1100. arXiv:astro-ph/9905318. Bibcode:1999astro.ph..5318B. doi:10.1086/300975. 
  4. ^ a b Kamper, K. W.; Wesselink, A. J. (1978). "Alpha and Proxima Centauri". Astronomical Journal 83: 1653–1659. Bibcode:1978AJ.....83.1653K. doi:10.1086/112378. 
  5. ^ a b c Ségransan, D. et al. (2003), "First radius measurements of very low mass stars with the VLTI", Astronomy and Astrophysics 397 (3): L5–L8, arXiv:astro-ph/0211647, Bibcode:2003A&A...397L...5S, doi:10.1051/0004-6361:20021714 
  6. ^ Demory, B.-O. et al. (October 2009), "Mass-radius relation of low and very low-mass stars revisited with the VLTI", Astronomy and Astrophysics 505 (1): 205–215, arXiv:0906.0602, Bibcode:2009A&A...505..205D, doi:10.1051/0004-6361/200911976 
  7. ^ a b See Table 1, Doyle, J. G.; Butler, C. J. (1990). "Optical and infrared photometry of dwarf M and K stars". Astronomy and Astrophysics 235: 335–339. Bibcode:1990A&A...235..335D.  and p. 57, Peebles, P. J. E. (1993). Principles of Physical Cosmology. Princeton, New Jersey: Princeton University Press. ISBN 0-691-01933-9. 
  8. ^ Schlaufman, K. C.; Laughlin, G. (September 2010), "A physically-motivated photometric calibration of M dwarf metallicity", Astronomy and Astrophysics 519, arXiv:1006.2850, Bibcode:2010A&A...519A.105S, doi:10.1051/0004-6361/201015016 
  9. ^ Benedict, G. F., McArthur, B. et al. (1998). "Photometry of Proxima Centauri and Barnard's Star Using Hubble Space Telescope Fine Guidance Sensor 3: A Search for Periodic Variations". The Astronomical Journal 116 (1): 429–439. arXiv:astro-ph/9806276. Bibcode:1998AJ....116..429B. doi:10.1086/300420. 
  10. ^ Torres, C. A. O. et al. (December 2006). "Search for associations containing young stars (SACY). I. Sample and searching method". Astronomy and Astrophysics 460 (3): 695–708. arXiv:astro-ph/0609258. Bibcode:2006A&A...460..695T. doi:10.1051/0004-6361:20065602. 
  11. ^ a b c d e Kervella, Pierre; Thevenin, Frederic (March 15, 2003). "A Family Portrait of the Alpha Centauri System: VLT Interferometer Studies the Nearest Stars". ESO. Retrieved July 9, 2007. 
  12. ^ "Latin Resources". Joint Association of Classical Teachers. Retrieved July 15, 2007. 
  13. ^ "Our Local Galactic Neighborhood". NASA. February 8, 2000. Retrieved March 22, 2013. 
  14. ^ Glister, Paul (September 1, 2010). "Into the Interstellar Void". Centauri Dreams. Retrieved March 22, 2013. 
  15. ^ a b c d Wertheimer, Jeremy G.; Laughlin, Gregory (2006). "Are Proxima and α Centauri Gravitationally Bound?". The Astronomical Journal 132 (5): 1995–1997. arXiv:astro-ph/0607401. Bibcode:2006astro.ph..7401W. doi:10.1086/507771. 
  16. ^ Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S.; Dupuis, J.; Keenan, F. P. (2004). "A Detailed Study of Opacity in the Upper Atmosphere of Proxima Centauri". The Astrophysical Journal 612 (2): 1140–1146. Bibcode:2004ApJ...612.1140C. doi:10.1086/422803. 
  17. ^ a b Wood, B. E.; Linsky, J. L.; Müller, H.-R.; Zank, G. P. (2001). "Observational Estimates for the Mass-Loss Rates of α Centauri and Proxima Centauri Using Hubble Space Telescope Lyα Spectra" (PDF). The Astrophysical Journal 547 (1): L49–L52. arXiv:astro-ph/0011153. Bibcode:2001ApJ...547L..49W. doi:10.1086/318888. Retrieved July 9, 2007. 
  18. ^ a b c Adams, Fred C.; Laughlin, Gregory; Graves, Genevieve J. M. Red Dwarfs and the End of the Main Sequence (PDF). Gravitational Collapse: From Massive Stars to Planets (Revista Mexicana de Astronomía y Astrofísica): 46–49. Retrieved June 24, 2008. 
  19. ^ Dunkley, J. et al. (2009). "Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results". The Astrophysical Journal Supplement Series 180 (2): 306–329. arXiv:0803.0586. Bibcode:2009ApJS..180..306D. doi:10.1088/0067-0049/180/2/306. 
  20. ^ a b Kürster, M. et al. (1999). "Precise radial velocities of Proxima Centauri. Strong constraints on a substellar companion". Astronomy & Astrophysics Letters 344: L5–L8. arXiv:astro-ph/9903010. Bibcode:1999A&A...344L...5K. 
  21. ^ a b Schroeder, Daniel J.; Golimowski, David A.; Brukardt, Ryan A.; Burrows, Christopher J.; Caldwell, John J.; Fastie, William G.; Ford, Holland C.; Hesman, Brigette et al. (2000). "A Search for Faint Companions to Nearby Stars Using the Wide Field Planetary Camera 2". The Astronomical Journal 119 (2): 906–922. Bibcode:2000AJ....119..906S. doi:10.1086/301227. 
  22. ^ a b Endl, M. & Kürster, M. (2008). "Toward detection of terrestrial planets in the habitable zone of our closest neighbor: Proxima Centauri". Astronomy and Astrophysics 488 (3): 1149–1153. arXiv:0807.1452. Bibcode:2008A&A...488.1149E. doi:10.1051/0004-6361:200810058. 
  23. ^ a b Watanabe, Susan (October 18, 2006). "Planet-Finding by Numbers". NASA JPL. Retrieved July 9, 2007. 
  24. ^ a b Tarter, Jill C. et al. (2007). "A Reappraisal of The Habitability of Planets around M Dwarf Stars". Astrobiology 7 (1): 30–65. arXiv:astro-ph/0609799. Bibcode:2007AsBio...7...30T. doi:10.1089/ast.2006.0124. PMID 17407403. 
  25. ^ a b Khodachenko, Maxim L. et al. (2007). "Coronal Mass Ejection (CME) Activity of Low Mass M Stars as An Important Factor for The Habitability of Terrestrial Exoplanets. I. CME Impact on Expected Magnetospheres of Earth-Like Exoplanets in Close-In Habitable Zones". Astrobiology 7 (1): 167–184. Bibcode:2007AsBio...7..167K. doi:10.1089/ast.2006.0127. PMID 17407406. 
  26. ^ a b Gilster, Paul (2004). Centauri Dreams: Imagining and Planning. Springer. ISBN 0-387-00436-X. 
  27. ^ Circular No. 30, 1915, October 12, of the Union Observatory (Proxima Centauri discovery paper).)
  28. ^ a b Glass, I. S. (July 2007). "The Discovery of the Nearest Star". African Skies 11: 39. Bibcode:2007AfrSk..11...39G. 
  29. ^ Glass, I.S. (2008). Proxima, the Nearest Star (other than the Sun). Cape Town: Mons Mensa. 
  30. ^ Go to WayBackMachine INTERNET ARCHIVE. Enter http://www.eso.org/outreach/press-rel/pr-2002/pr-22-02.html. Choose 20 August 2006 for ESO Press Release: "How Small are Small Stars Really?".
  31. ^ a b c Alden, Harold L. (1928). "Alpha and Proxima Centauri". Astronomical Journal 39 (913): 20–23. Bibcode:1928AJ.....39...20A. doi:10.1086/104871. 
  32. ^ a b c Circular No. 40, 1917, September 3, of the Union Observatory
  33. ^ a b Voûte, J. (1917). "A 13th magnitude star in Centaurus with the same parallax as α Centauri". Monthly Notices of the Royal Astronomical Society 77: 650–651. Bibcode:1917MNRAS..77..650V. 
  34. ^ Clavin, Whitney; Harrington, J.D. (April 25, 2014). "NASA's Spitzer and WISE Telescopes Find Close, Cold Neighbor of Sun". NASA. Archived from the original on April 25, 2014. Retrieved April 25, 2014. 
  35. ^ Shapley, Harlow (1951). "Proxima Centauri as a Flare Star". Proceedings of the National Academy of Sciences of the United States of America 37 (1): 15–18. Bibcode:1951PNAS...37...15S. doi:10.1073/pnas.37.1.15. PMC 1063292. PMID 16588985. 
  36. ^ Kroupa, Pavel; Burman, R. R.; Blair, D. G. (1989). "Photometric observations of flares on Proxima Centauri". PASA 8 (2): 119–122. Bibcode:1989PASAu...8..119K. 
  37. ^ Haisch, Bernhard; Antunes, A.; Schmitt, J. H. M. M. (1995). "Solar-Like M-Class X-ray Flares on Proxima Centauri Observed by the ASCA Satellite". Science 268 (5215): 1327–1329. Bibcode:1995Sci...268.1327H. doi:10.1126/science.268.5215.1327. PMID 17778978. 
  38. ^ a b c Guedel, M.; Audard, M.; Reale, F.; Skinner, S. L.; Linsky, J. L. (2004). "Flares from small to large: X-ray spectroscopy of Proxima Centauri with XMM-Newton". Astronomy and Astrophysics 416 (2): 713–732. arXiv:astro-ph/0312297. Bibcode:2004A&A...416..713G. doi:10.1051/0004-6361:20031471. 
  39. ^ "Proxima Centauri UV Flux Distribution". ESA/Laboratory for Space Astrophysics and Theoretical Physics. Retrieved July 11, 2007. 
  40. ^ Kaler, Jim. "Rigil Kentaurus". University of Illinois. Retrieved August 3, 2008. 
  41. ^ Sherrod, P. Clay; Koed, Thomas L.; Aleichem, Thomas L. Sholem (2003). A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations. Courier Dover Publications. ISBN 0-486-42820-6. 
  42. ^ Binney, James; Scott Tremaine (1987). Galactic Dynamics. Princeton, New Jersey: Princeton University Press. p. 8. ISBN 0-691-08445-9. 
  43. ^ Leggett, S. K. (1992). "Infrared colors of low-mass stars". Astrophysical Journal Supplement Series 82 (1): 351–394, 357. Bibcode:1992ApJS...82..351L. doi:10.1086/191720. 
  44. ^ Go to WayBackMachine INTERNET ARCHIVE. Enter http://www.eso.org/outreach/press-rel/pr-2002/pr-22-02.html. Choose 20 August 2006 for ESO Press Release: "How Small are Small Stars Really?"
  45. ^ Zombeck, Martin V. (2007). Handbook of Space Astronomy and Astrophysics (Third ed.). Cambridge, UK: Cambridge University Press. p. 109. ISBN 0-521-78242-2. 
  46. ^ Staff (August 30, 2006). "Proxima Centauri: The Nearest Star to the Sun". Harvard-Smithsonian Center for Astrophysics. Retrieved July 9, 2007. 
  47. ^ E. F., Guinan; Morgan, N. D. (1996). "Proxima Centauri: Rotation, Chromosperic Activity, and Flares". Bulletin of the American Astronomical Society 28: 942. Bibcode:1996BAAS...28S.942G. 
  48. ^ Wargelin, Bradford J.; Drake, Jeremy J. (2002). "Stringent X-Ray Constraints on Mass Loss from Proxima Centauri". The Astrophysical Journal 578 (1): 503–514. Bibcode:2002ApJ...578..503W. doi:10.1086/342270. 
  49. ^ Stauffer, J. R.; Hartmann, L. W. (1986). "Chromospheric activity, kinematics, and metallicities of nearby M dwarfs". Astrophysical Journal Supplement Series 61 (2): 531–568. Bibcode:1986ApJS...61..531S. doi:10.1086/191123. 
  50. ^ Cincunegui, C.; Díaz, R. F.; Mauas, P. J. D. (2007). "A possible activity cycle in Proxima Centauri". Astronomy and Astrophysics 461 (3): 1107–1113. arXiv:astro-ph/0703514. Bibcode:2007A&A...461.1107C. doi:10.1051/0004-6361:20066027. 
  51. ^ Wood, B. E.; Linsky, J. L.; Muller, H.-R.; Zank, G. P. (2000). "Observational Estimates for the Mass-Loss Rates of Alpha Centauri and Proxima Centauri Using Hubble Space Telescope Lyman-alpha Spectra". Astrophysical Journal 537 (2): L49–L52. arXiv:astro-ph/0011153. Bibcode:2000ApJ...537..304W. doi:10.1086/309026. 
  52. ^ Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J. et al. (July 1997), "The Hipparcos Catalogue", Astronomy and Astrophysics 323: L49–L52, Bibcode:1997A&A...323L..49P 
  53. ^ Kirkpatrick, J. Davy et al. (1999). "Brown Dwarf Companions to G-type Stars. I: Gliese 417B and Gliese 584C". The Astronomical Journal 121 (6): 3235–3253. arXiv:astro-ph/0103218. Bibcode:2001AJ....121.3235K. doi:10.1086/321085. 
  54. ^ Williams, D. R. (February 10, 2006). "Moon Fact Sheet". NASA. Retrieved October 12, 2007. 
  55. ^ Benedict, G. F. et al. Astrometric Stability and Precision of Fine Guidance Sensor #3: The Parallax and Proper Motion of Proxima Centauri (PDF). Proceedings of the HST Calibration Workshop: 380–384. Retrieved July 11, 2007. 
  56. ^ Matthews, R. A. J. (1994). "The Close Approach of Stars in the Solar Neighborhood". Quarterly Journal of the Royal Astronomical Society 35: 1–9. Bibcode:1994QJRAS..35....1M. 
  57. ^ Bobylev, V. V. (March 2010). "Searching for stars closely encountering with the solar system". Astronomy Letters 36 (3): 220–226. arXiv:1003.2160. Bibcode:2010AstL...36..220B. doi:10.1134/S1063773710030060. 
  58. ^ Allen, C.; Herrera, M. A. (1998). "The galactic orbits of nearby UV Ceti stars". Revista Mexicana de Astronomia y Astrofisica 34: 37–46. Bibcode:1998RMxAA..34...37A. 
  59. ^ Matthews, Robert; Gilmore, Gerard (1993). "Is Proxima really in orbit about Alpha CEN A/B?". MNRAS 261: L5. Bibcode:1993MNRAS.261L...5M. doi:10.1093/mnras/261.1.l5. 
  60. ^ Kroupa, Pavel (1995). "The dynamical properties of stellar systems in the Galactic disc". MNRAS 277: 1507. arXiv:astro-ph/9508084. Bibcode:1995MNRAS.277.1507K. doi:10.1093/mnras/277.4.1507. 
  61. ^ Johnston, Kathryn V.; Hernquist, Lars; Bolte, Michael (1995). "Fossil Signatures of Ancient Accretion Events in the Halo". The Astrophysical Journal 465: 278. arXiv:astro-ph/9602060. Bibcode:1996ApJ...465..278J. doi:10.1086/177418. 
  62. ^ Anosova, J.; Orlov, V. V.; Pavlova, N. A. (1994). "Dynamics of nearby multiple stars. The Alpha Centauri system". Astronomy and Astrophysics 292 (1): 115–118. Bibcode:1994A&A...292..115A. 
  63. ^ "WISE Satellite Set to Map the Infrared Universe". Scientific American. December 9, 2009. Retrieved December 10, 2009. 
  64. ^ Woolley R.; Epps E. A.; Penston M. J.; Pocock S. B. (1970). "Woolley 551". Catalogue of stars within 25 parsecs of the Sun. Retrieved May 11, 2014. 
  65. ^ Gliese, W. and Jahreiß, H. (1991). "Gl 551". Preliminary Version of the Third Catalogue of Nearby Stars. Retrieved May 11, 2014. 
  66. ^ Van Altena W. F., Lee J. T., Hoffleit E. D. (1995). "GCTP 3278". The General Catalogue of Trigonometric Stellar Parallaxes (Fourth ed.). Retrieved May 11, 2014. 
  67. ^ Perryman et al. (1997). "HIP 70890". The Hipparcos and Tycho Catalogues. Retrieved May 11, 2014. 
  68. ^ Perryman et al. (1997). "HIP 70890". The Hipparcos and Tycho Catalogues. Retrieved May 11, 2014. 
  69. ^ Henry, Todd J.; Subasavage, John P.; Brown, Misty A.; Beaulieu, Thomas D.; Jao, Wei-Chun; Hambly, Nigel C. (2004). "The Solar Neighborhood. X. New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs". The Astronomical Journal 128 (5): 2460–2473. arXiv:astro-ph/0408240. Bibcode:2004AJ....128.2460H. doi:10.1086/425052.  edit
  70. ^ Jao, Wei-Chun; Henry, Todd J.; Subasavage, John P.; Brown, Misty A.; Ianna, Philip A.; Bartlett, Jennifer L.; Costa, Edgardo; Méndez, René A. (2005). "The Solar Neighborhood. XIII. Parallax Results from the CTIOPI 0.9 Meter Program: Stars with mu >= 1.0" yr-1 (MOTION Sample)". The Astronomical Journal 129 (4): 1954–1967. arXiv:astro-ph/0502167. Bibcode:2005AJ....129.1954J. doi:10.1086/428489.  edit
  71. ^ van Leeuwen F. (2007). "HIP 70890". Validation of the new Hipparcos reduction. Retrieved May 11, 2014. 
  72. ^ "RECONS TOP100". THE ONE HUNDRED NEAREST STAR SYSTEMS brought to you by RECONS (Research Consortium On Nearby Stars). 2012. Retrieved May 11, 2014. 
  73. ^ Lurie, John C.; Henry, Todd J.; Jao, Wei-Chun; Quinn, Samuel N.; Winters, Jennifer G.; Ianna, Philip A.; Koerner, David W.; Riedel, Adric R.; Subasavage, John P. (2014). "The Solar Neighborhood. XXXIV. a Search for Planets Orbiting Nearby M Dwarfs Using Astrometry". The Astronomical Journal 148 (5): 91. arXiv:1407.4820. Bibcode:2014AJ....148...91L. doi:10.1088/0004-6256/148/5/91.  edit
  74. ^ Saar, Steven H.; Donahue, Robert A. (1997). "Activity-related Radial Velocity Variation in Cool Stars". Astrophysical Journal 485 (1): 319–326. Bibcode:1997ApJ...485..319S. doi:10.1086/304392. 
  75. ^ Schultz, A. B.; Hart, H. M.; Hershey, J. L.; Hamilton, F. C.; Kochte, M.; Bruhweiler, F. C.; Benedict, G. F.; Caldwell, John et al. (1998). "A possible companion to Proxima Centauri". Astronomical Journal 115 (1): 345–350. Bibcode:1998AJ....115..345S. doi:10.1086/300176. 
  76. ^ Endl, M.; Kuerster, M.; Rouesnel, F.; Els, S.; Hatzes, A. P.; Cochran, W. D. (June 18–21, 2002). Drake Deming, ed. Extrasolar Terrestrial Planets: Can We Detect Them Already?. Conference Proceedings, Scientific Frontiers in Research on Extrasolar Planets (Washington, DC): 75–79. arXiv:astro-ph/0208462. 
  77. ^ Alpert, Mark (November 2005). "Red Star Rising". Scientific American. Retrieved May 19, 2008. 
  78. ^ Ward, Peter D.; Brownlee, Donald (2000). Rare Earth: Why Complex Life is Uncommon in the Universe. Springer Publishing. ISBN 0-387-98701-0. 
  79. ^ Crawford, I. A. (September 1990). "Interstellar Travel: A Review for Astronomers". Quarterly Journal of the Royal Astronomical Society 31: 377–400. Bibcode:1990QJRAS..31..377C. 
  80. ^ a b Beals, K. A.; Beaulieu, M.; Dembia, F. J.; Kerstiens, J.; Kramer, D. L.; West, J. R.; Zito, J. A. (1988). "Project Longshot, an Unmanned Probe to Alpha Centauri" (PDF). NASA-CR-184718. U. S. Naval Academy. Retrieved June 13, 2008. 
  81. ^ The coordinates of the Sun would be diametrically opposite Proxima, at α=02h 29m 42.9487s, δ=+62° 40′ 46.141″. The absolute magnitude Mv of the Sun is 4.83, so at a parallax π of 0.77199 the apparent magnitude m is given by 4.83 − 5(log10(0.77199) + 1) = 0.40. See: Tayler, Roger John (1994). The Stars: Their Structure and Evolution. Cambridge University Press. p. 16. ISBN 0-521-45885-4. 

External links[edit]