Proxima Centauri b

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Exoplanet
Proxima Centauri b

Proxima Centauri (small, in the center of the picture), surrounded by the habitable zone (green) with the orbit of its planet; in the left half of the picture for comparison the sun with Mercury's orbit.

Proxima Centauri (small, in the center of the picture), surrounded by the habitable zone (green) with the orbit of its planet; in the left half of the picture for comparison the sun and Mercury's orbit.
Constellation centaur
Position
equinox : J2000.0
Right ascension 14h 29m 43s
declination −62 ° 40 ′ 46 ″
Orbit data
Central star Proxima Centauri
Major semi-axis 0.05 AU
eccentricity 0 (0 to 0.35)
Period of circulation 11,186 days
Further data
radius 1.1 earth radii
Minimum dimensions 1.27 earth masses
distance 1.295 pc
history
discovery Guillem Anglada-Escudé et al.
Date of discovery August 24, 2016 (Publication)

Proxima Centauri b (also called Proxima b for short ) is the closest known exoplanet to the Earth according to current research . It orbits the star Proxima Centauri , which is about 4.2 light-years from Earth , within its habitable zone and was detected in August 2016 using the radial velocity method . Liquid water could exist on it, an important prerequisite for earth-like life .

The discovery is important because of the relative proximity of the exoplanet, which facilitates further investigations. In addition, Proxima Centauri b has an Earth Similarity Index of 0.87, making it the front runner among the potentially habitable exoplanets at the time of its discovery . After all, the discovery is important because its star Proxima Centauri is one of the most common star types in our galaxy. An estimated 70 to 80 percent of all stars in the Milky Way are red dwarfs .

properties

At first it was assumed that the mass of Proxima Centauri b is at least 1.27  earth masses , depending on the orbit inclination unknown until 2020, the mass could have been greater, whereby it would have a mass of less than 3 earth masses with 90% probability. New measurements by the ESPRESSO spectrograph on the Very Large Telescope have shown a mass of only 1.17 earth masses; Due to its mass, Proxima Centauri b probably belongs to the Earth-like (exo-) planets.

The star Proxima Centauri around it is a red dwarf in the constellation Centaurus . It is the closest star at 4.224  light years from the Sun.

Proxima Centauri b presumably has a bound rotation . In this case it can be assumed that its light-flooded hemisphere is significantly hotter than the side facing away from the star. The equilibrium temperature of the planet calculated from the luminosity of the star, the distance and an assumed albedo of 0 is 234  Kelvin (-39  ° C ), but the surface temperature can be higher due to the greenhouse effect if the planet has an atmosphere .

According to simulations published in May 2017, liquid water is possible on the surface depending on the actual exact orbit parameters and the actual atmospheric composition.

discovery

The illustration shows changes in the speed of the star Proxima Centauri away from and towards the Earth from January 1, 2016. The regular pattern of the changing radial speeds (red and vertical axis) repeats with a period of 11.2 days - the orbital time of the planet, which is shown indirectly (blue line).

The first indications of the exoplanet were found in 2013 by Mikko Tuomi through the analysis of archived observation data. To confirm this discovery, the European Southern Observatory ESO , led by Guillem Anglada-Escudé, started a project called Pale Red Dot (an allusion to Pale Blue Dot ) in January 2016 . It finally found Proxima Centauri b using the radial velocity method .

The measurements were carried out in Chile with the HARPS spectrograph at the La Silla Observatory and the UVES spectrograph of the VLT at the Paranal Observatory . The discovery of the exoplanet was published on August 24, 2016 by the research team at Queen Mary University in London in the journal Nature .

Proxima Centauri b and its parent star

Comparison of the apparent size and color of the sun as seen from Earth (left) and Proxima Centauri as seen from Proxima Centauri b in an Earth-like atmosphere (right)

Seen from its planet, the mother star Proxima Centauri appears significantly larger than the sun from Earth. Proxima Centauri is much smaller than this one, but much closer to the planet. The apparent diameter of the central star is around 1.5 °, roughly three times the apparent size of the sun.

The term “red dwarf” must not be taken literally. Proxima Centauri is less hot than the sun, but its light appears white and not reddish because it arises from a photosphere temperature of 3040 K.

Speculative models of surface temperature

Since only its minimum mass, the period of revolution and the distance to the parent star are known of the planet, it is currently difficult to make any statements about the chemical and physical conditions on its surface. Simulations like the one in the following two videos show possible scenarios for the temperature distribution, once with a 3: 2 orbit resonance and once with a bound rotation .

The simulations assume an earth-like atmosphere and a water surface. The dashed line describes the transition from ice to liquid water.

Web links

Commons : Proxima Centauri b  - collection of images, videos and audio files

Individual evidence

  1. ↑ The Exoplanet in the "Encyclopedia of Extrasolar Planets" (English)
  2. ↑ Planet discovered around the closest star , orf.at from August 24, 2016
  3. ↑ Nicola Davis: Discovery of potentially Earth-like planet Proxima b raises hopes for life . In: The Guardian . August 24, 2016. Retrieved August 24, 2016.
  4. ↑ Earth-sized planet around nearby star is astronomy dream come true . In: Nature , August 24, 2016, pp. 381-382. 
  5. ↑ a b Guillem Anglada-Escudé et al .: A terrestrial planet candidate in a temperate orbit around Proxima Centauri . In: Nature . 536, No. 7617, August 25, 2016, ISSN  0028-0836 , pp. 437-440. doi : 10.1038 / nature19106 .
  6. ↑ a b A Potentially Habitable World in Our Nearest Star - Planetary Habitability Laboratory @ UPR Arecibo. In: upr.edu. phl.upr.edu, accessed August 25, 2016 .
  7. ↑ Earth-like planet near Proxima Centauri. In: mpg.de. Retrieved August 31, 2016 .
  8. ↑ If the angle between the normal vector of the orbit plane and the direction of observation Earth - Proxima Centauri, then the true mass is .
  9. ↑ Franck Marchis: Proxima Centauri b: Have we just found Earth's cousin right on our doorstep? . The Planetary Society . August 24, 2016. Retrieved August 24, 2016.
  10. ↑ Ian A. Boutle et al .: Exploring the climate of Proxima B with the Met Office Unified Model . In: EDP Sciences (Ed.): Astronomy & Astrophysics . tape 601 , May 17, 2017, doi : 10.1051 / 0004-6361 / 201630020 ( aanda.org [PDF]).
  11. ↑ A friendly climate on Proxima B? - Earth twin could offer amazingly stable climatic conditions. scinexx , May 17, 2017, accessed May 17, 2017 .
  12. ↑ Earth-like planet near Proxima Centauri. In: mpg.de. Retrieved August 31, 2016 .
  13. ↑ The news magazine Der Spiegel reported on the (suspected) discovery on August 12, 2016, see Scientific sensation: A possible second earth discovered in our neighborhood
  14. ↑ Robert Gast: Exoplanet "Proxima b": The best of the alien worlds In: Neue Zürcher Zeitung of August 24, 2016
  15. ^ Tilmann Althaus, Axel M. Quetz: Red dwarf - but no red lantern! In: Stars and Space 10/2016, page 27