Jean 581

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Star
gliese 581
DSS image by Gliese 581
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Libra
Right ascension 15 h 19 m 26.83 s
declination −07 ° 43 ′ 20.2 ″
Apparent brightness 10.57 mag
Typing
Known exoplanets 3
B − V color index +1.6 
Spectral class M5
Astrometry
Radial velocity (−9.7 ± 0.2) km / s
parallax (160.91 ± 2.62)  mas
distance (20.27 ± 0.33)  ly
(6.21 ± 0.10)  pc  
Visual absolute brightness M vis +11.6 mag
Proper movement 
Rec. Share: (−1227.67 ± 3.54)  mas / a
Dec. portion: (−97.78 ± 2.43)  mas / a
Physical Properties
Dimensions 0.33  M ☉
radius 0.38  R ☉
Luminosity

0.002  L ☉

Effective temperature 3480  K
Metallicity [Fe / H] −0.25
Rotation time 9.6 days
Other names
and catalog entries
Bonn survey BD −7 ° 4003
Gliese catalog FY 581 [1]
Hipparcos catalog HIP 74995 [2]
Tycho catalog TYC 5594-1093-1 [3]Template: Infobox star / maintenance / specification of the TYC catalog
Other names HO Librae • Wolf 562 • LHS 394 • LFT 1195 • LTT 6112 • LFT 1195 • LPM 564 • NLTT 39886 •

Gliese 581 [ ˈgliːzə ] is a star in the constellation Libra, about 20 light years (190 billion kilometers) away . It is one of the hundred stars closest to the sun and is usually referred to with its catalog number 581 from the Catalog of Nearby Stars ( Catalog of Nearby Stars , 1957) by Wilhelm Gliese . It is a red dwarf of the spectral class M2.5, which is about 500 times weaker than our sun and has only a third of its mass. There are currently three planetary companions secured: Gliese 581 b , c and e . Three other planetary companions are currently controversial ( d ) or have been rejected ( f and g ).

Planets

planet
 Discovery year Mass
(in M E ) 		Cycle time
(in days)
b 2005 unknown; > 17 5.4
c 2007 unknown; > 5 13
e 2009 unknown; > 1.9 3.15

Gliese 581 b

Gliese 581 b orbits its star every 5.366 days at a distance of 0.04  AU (six million kilometers). Its minimum mass is roughly 17 times the mass of the earth. The exoplanet was discovered in 2005 by a group of astronomers from Switzerland, France and Portugal led by Michel Mayor , Stéphane Udry and Xavier Delfosse.

Gliese 581 c

This planet, discovered in 2007, is one of the smallest known exoplanets. The orbit period of Gliese 581 c is 13 days. It has at least five times the mass of the earth.

He may be in the habitable zone of his solar system, that is, in the area where water can potentially exist in a liquid state. However, according to recent research, it is too close to its sun, making it too hot.

Gliese 581 e

Gliese 581 e orbits its central star every 3.15 days and has a minimum mass of approximately 1.9 earth masses.

Controversial property "Gliese 581 d"

The discovery of an exoplanet "Gliese 581 d" with the help of the HARPS instrument of the European Southern Observatory was announced in April 2007 by a team led by Stéphane Udry . The calculated orbital period was around 67 days, which would put the exoplanet in the habitable zone . In August 2009 there was an action in which messages were sent to Gliese 581d . People around the world were able to compose 160-character texts that were collectively broadcast on August 24th from the Canberra Deep Space Communication Complex . The over 25,000 greetings are expected to arrive on the planet by the end of 2029 (if it exists).

In 2014 Paul Robertson et al. an examination of the spectral data of Gliese 581, in which they took into account the influence of stellar activities on the spectral signal. The signal that led to the discovery of Gliese 581 d was questioned and identified as an artifact of the stellar activity of the central star. This work also called into question the existence of Gliese 581 g (see below).

In a more recent study (September 2014, published March 2015), English authors criticize the analytical methods of Robertson et al. shows that the signal for the planet could be real and Gliese 581d could therefore exist.

Artifact "Gliese 581 f"

Movement of planet and star around the common center of gravity ( barycenter / red cross). The movement of the star can be observed and measured.

The published on 29 September 2010 discovery was made using the radial velocity method , in which data of the HIRES - spectrograph on the Keck I telescope in Hawaii and the HARPS -Instruments 3.6 m of the La Silla Observatory of ESO were combined in Chile . The team included astronomers Steven S. Vogt, R. Paul Butler, Eugenio J. Rivera, Nader Haghighipour , Gregory W. Henry, and Michael H. Williamson. In 2011, the HIRES and HARPS data were subjected to statistical analysis by both Philipp C. Gregory and Mikko Tuomi, with the result that the existence of the planets Gliese 581 b , c , d and e could be confirmed. The existence of Gliese 581 f was not supported by the data, nor was that of Gliese 581 g.

Artifact "Gliese 581 g"

The publication of the possible discovery of Gliese 581 g took place together with Gliese 581 f on September 27, 2010. Among other things, it was described as possibly the most earth-like exoplanet known to date and it was speculated that Gliese 581 g might be made of stone and have enough mass to keep an atmosphere. According to the published orbit data, it would have been in the habitable zone . The analysis was based on 122 observations of the radial velocity of the star Gliese 581 over a period of 11 years with the HIRES spectrometer from the Keck Observatory on Mauna Kea , Hawaii , which were combined with observations from the HARPS spectrograph from the La Silla Observatory . Doubts about the alleged existence arose early on. Finally it could be shown that the statistical analysis in the publication of the discovery shows inadequacies.

A reanalysis of the data, published January 5, 2011, could not confirm the existence of an exoplanet with the claimed properties. For this purpose, models for a theoretical planetary model of one to six planets were simulated. The HARPS data thus excluded Gliese 581 g with the values ​​published at the time. In 2014 Paul Robertson et al. an examination of the spectral data of Gliese 581, in which they took into account the influence of stellar activities on the spectral signal and thus identified Gliese 581 g as an artifact of the same.

Summary of the scientific analyzes for the Gliese 581 system

An analysis of the system from 2011 suggested the existence of 4 planets, whereby the two planets postulated in 2010 ( f , g ) were rejected. In 2014 an analysis of the stellar activities of the star and its influence on spectral signals was carried out. This work suspected an artifact behind the apparent discovery of Gliese 581 g and also questioned the existence of Gliese 581 d . A work from 2015 suggests the existence of the latter planet again, as it regards its signal as real.

See also

Web links

Commons : Gliese 581  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Hipparcos catalog (ESA 1997)
  2. ↑ Pulkovo radial velocities for 35493 HIP stars
  3. ↑ a b c Hipparcos, the New Reduction (van Leeuwen, 2007)
  4. ↑ estimated from apparent brightness and distance
  5. ↑ Stéphane Udry et al .: The HARPS search for southern extra-solar planets XI. Super-Earths (5 & 8 M_Earth) in a 3-planet system . April 29, 2007, doi : 10.1051 / 0004-6361: 20077612 , arxiv : 0704.3841 .
  6. ^ "Hello from Earth" message for Gliese 581D. marspages.eu, August 17, 2009, accessed March 8, 2015 .
  7. ↑ Action page "Hello from Earth". (No longer available online.) Cosmos Magazine (Australia), 2009, archived from the original on November 5, 2013 ; accessed on March 8, 2015 .
  8. ↑ a b Earth twins exposed as a deception. Magnetic turbulence on the red dwarf simulated the signal from two super-earths . On: scinexx.de from July 4, 2014.
  9. ^ A b Paul Robertson, Suvrath Mahadevan, Michael Endl, Arpita Roy: Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581 . In: Science . July 2014. doi : 10.1126 / science.1253253 . Retrieved July 4, 2014.
  10. ↑ a b Guillem Anglada-Escudé, Mikko Tuomi: Comment on “Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581”. Science , March 6, 2015, accessed March 8, 2015 . ( doi: 10.1126 / science.1260796 )
  11. ↑ a b c The Lick-Carnegie Exoplanet Survey: A 3.1 M ⊕ Planet in the Habitable Zone of the Nearby M3V Star Gliese 581 (PDF file; 1.5 MB) (PDF; 1.6 MB) University of California. September 29, 2010. Retrieved September 29, 2010. ( arxiv : 1009.5733 )
  12. ^ A b Philipp C. Gregory: Bayesian re-analysis of the Gliese 581 exoplanet system. In: Monthly Notices of the Royal Astronomical Society vol. 415, no. 3, pp. 2523-2545, doi: 10.1111 / j.1365- 2966.2011.18877.x , arxiv : 1101.0800 .
  13. ↑ a b Mikko Tuomi: Bayesian re-analysis of the radial velocities of Gliese 581. Evidence in favor of only four planetary companions. In: Astronomy and Astrophysics , arxiv : 1102.3314 .
  14. ↑ Markus Becker: Controversy: Doubts about the existence of life-friendly planets. Spiegel Online , October 14, 2010, accessed October 15, 2010 .
  15. ^ Andrae et al .: Dos and donts of reduced chi-squared . December 16, 2010, arxiv : 1012.3754 .
  16. ↑ Bayesian Re-analysis of the Gliese 581 Exoplanet System . In: Cornell University (Ed.): Solar and Stellar Astrophysics . August. arxiv : 1101.0800 .