Proxima Centauri
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Proxima Centrauri |
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| Observation data Equinox J2000 |
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|---|---|
| Constellation | Centaurus |
| Right ascension | 14h 29m 43.0s |
| Declination | -62° 40' 46" |
| Apparent magnitude (V) | 11.05 |
| Characteristics | |
| Spectral type | M5.5 V |
| U-B color index | 1.49 |
| B-V color index | 1.90 |
| Variable type | Flare star |
| Astrometry | |
| Radial velocity (Rv) | -20.3 km/s |
| Proper motion (μ) | RA: -3775.64 mas/yr Dec.: 768.16 mas/yr |
| Parallax (π) | 771.99 ± 2.25 mas |
| Distance | 4.22 ± 0.01 ly (1.295 ± 0.004 pc) |
| Absolute magnitude (MV) | 15.49 |
| Details | |
| Mass | 0.12 M☉ |
| Radius | 0.15 R☉ |
| Luminosity | 5-12 × 10-5 L☉ |
| Temperature | 2,670 K |
| Metallicity | 10% |
| Rotation | 30-33 days |
| Age | estimated 1 × 109 years |
| Other designations | |
The red dwarf star Proxima Centauri, part of the Alpha Centauri star system, is the nearest star to our Sun, 4.22 light years away. As the name suggests, it is located in the constellation of Centaurus. Proxima Centauri was discovered to share the same proper motion as Alpha Centauri in 1915 by Robert Innes while he was Director of the Union Observatory in Johannesburg, South Africa. It was Innes who suggested the name Proxima. In 1917 at the Royal Observatory, Cape of Good Hope, the Dutch astronomer J. Voûte measured the trigonometric parallax and determined that Proxima was indeed at the same distance as Alpha Centauri, and hence was also the lowest luminosity star known at the time[1].
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[edit] Characteristics
Red dwarfs in general are far too faint to be observable with the naked eye, and Proxima Centauri is no exception. It has an apparent magnitude of 11 while its absolute magnitude is a very dim 15.5. Seen from Alpha Centauri A or B, Proxima would be a 4.5 magnitude star.
Based on the parallax of 772.3 ± 2.4 milliarcseconds measured by Hipparcos (and the more precise parallax determined using the Fine Guidance Sensors on the Hubble Space Telescope of 768.7 ± 0.3 milliarcseconds), Proxima Centauri is roughly 4.2 light years from Earth, or 270,000 times more distant than the Sun. Its closest neighbors are Alpha Centauri A and B (at 0.21 light years), the Sun, and Barnard's Star (at 5.96 light years). From Earth's vantage point, Proxima is separated by 2° from Alpha Centauri, or 4 times the angular diameter of the full Moon.
At least among the known stars, Proxima Centauri has been the closest star to the Sun for about the last 32,000 years and will be so for about another 9,000 years, when it will be replaced by Barnard's Star. [3]
In 2002, VLTI used optical interferometry to measure an angular diameter of 1.02 ± 0.08 milliarcsec for Proxima Centauri. Knowing its distance, the actual diameter can be determined to be about 1/7 that of the Sun, or 1.5 times that of Jupiter. Its mass is also about 1/7 that of the Sun, or 150 times that of Jupiter.
At a distance to Alpha Centauri of just 1/20th of Proxima Centauri's distance to the Sun, Proxima may actually be in orbit about Alpha, with an orbital period on the order of 500,000 years or more. For this reason, Proxima is sometimes referred to as Alpha Centauri C. However, it is possible that it may not actually be in orbit, although the association is unlikely to be entirely accidental as it shares approximately the same motion through space as the larger star system[2].
Proxima, along with Alpha Centauri A and B, are among the "Tier 1" target stars for NASA's Space Interferometry Mission (SIM). SIM will be able to detect planets as small as three Earth-masses within two Astronomical Units of a "Tier 1" target. Due to Proxima's small mass and distance, SIM would be able to detect even smaller planets around this star, should they exist.
[edit] Traveling to Proxima Centauri
Proxima Centauri has been suggested as a logical first destination for interstellar travel, although as a flare star it would not be particularly hospitable. The current standard spaceship, the Space Shuttle, travels in orbit at 7.8 km/s. At that speed, it would take 160,000 years to reach Proxima. The fastest man-made spacecraft, the Helios II deep space probe, has set a speed record of 70.2 km/s. Even at that speed, the journey to Proxima Centauri would take ~17,800 years. The proposed VASIMR propulsion system, possibly able to achieve speeds up to 300 km/s, would shorten the journey to a "mere" 4,200 years —still firmly beyond the current lifespan of both man and machine. A proposed design of probe to Alpha Centauri system called Project Longshot using existing technology estimated time of travel of about 100 years. It follows that interstellar travel would require significant development of radical ideas to become feasible, such as hypothetical generation ships, laser-pushed solar sails, nuclear fusion powered Bussard ramjets, nuclear pulse drives, warp drives or Wormholes.
[edit] See also
[edit] References
- ^ J Voûte, A 13th magnitude star in Centaurus with the same parallax as α Centauri, Monthly Notices of the Royal Astronomical Society, Vol. 77 (June 1917), pp. 650-651; fulltext
- ^ R Matthews, G Gilmore, Is Proxima really in orbit around α Cen A/B?, Monthly Notices of the Royal Astronomical Society, Vol. 261, L5-L7 (1993); fulltext
3. ^ a b c Bell, George H. (April 2001). The Search for the Extrasolar Planets: A Brief History of the Search, the Findings and the Future Implications, Section 2. Arizona State University. Retrieved on 2006-08-10. Full description of the Van de Kamp planet controversy.
