YZ Ceti

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Star
YZ Ceti
Position of YZ Ceti in the constellation Whale
Position of YZ Ceti in the constellation Whale
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation whale
Right ascension 01 h 12 m 30.64 s
declination -16 ° 59 ′ 56.4 ″
Apparent brightness 12.07 (12.03 to 12.18) mag
Typing
Known exoplanets 3
B − V color index +1.81 
U − B color index +1.43 
R − I index +1.76 
Spectral class M4.0 Ve
Variable star type BY + UV 
Astrometry
Radial velocity (+28.1 ± 0.1) km / s
parallax (269.36 ± 0.08)  mas
distance (12.10 ± 0.01)  ly
(3.71 ± 0.01)  pc
Visual absolute brightness M vis approx. 14 mag
Proper movement 
Rec. Share: (+1205.18 ± 0.17)  mas / a
Dec. portion: (+637.76 ± 0.12)  mas / a
Physical Properties
Dimensions (0.135 ± 0.003)  M ☉
radius (0.169 ± 0.005)  R ☉
Effective temperature (3056 ± 60)  K.
Metallicity [Fe / H] (−0.26 ± 0.08)
Age (4.0 ± 0.6) bill.  A
Other names
and catalog entries
Gliese catalog FY 54.1 [1]
Hipparcos catalog HIP 5643 [2]
Tycho catalog TYC 5851-171-1 [3]Template: Infobox star / maintenance / specification of the TYC catalog
2MASS catalog 2MASS J01123052-1659570 [4]
Other names YZ Ceti • LHS 138 • LTT 670 • Zkh 26

YZ Ceti is a red dwarf in the constellation Cetus (whale). Although it is relatively close to the Sun at a distance of around 12 light years , the star can not be observed with the naked eye due to its low apparent magnitude of only around 12 mag . He has a planetary system that consists of at least three, but possibly four, exoplanets .

The name part "YZ" follows the rules for naming variable stars and says that YZ Ceti is the 53rd variable star discovered in the constellation Whale.

properties

YZ Ceti is a UV Ceti star (flare star ) that shows periodic changes in its luminosity . Its mass is only about 8.5% of the mass of the sun, the star is 5500 times fainter than it.

Planetary system

In August 2017, a team of astronomers led by Nicola Astudillo-Defru announced the discovery of three planets around YZ Ceti after measurements with the Échelle spectrograph HARPS of the European Southern Observatory (ESO). At the time of their discovery, they were the lowest-mass exoplanets found using the radial velocity method .

The three planets are named YZ Ceti b , YZ Ceti c and YZ Ceti d and are many times closer to their central star than Mercury is to the sun. Their orbital times are only between about 2 and 4.6 earth days. Their minimum masses are comparable to the mass of the earth . YZ Ceti b has 0.75 times, YZ Ceti c 0.98 times, and YZ Ceti d 1.14 times the minimum mass of the earth. YZ Ceti b and YZ Ceti c continue to orbit approximately in a 2: 3 resonance around YZ Ceti. A planet with a minimum mass of 0.472 earth masses and an orbital period of 1.04 earth days is considered possible, but could not be confirmed with certainty.

Planetary system from YZ Ceti
Planet
(by distance from the star) 		Discovery
(year) 		Mass
(in M ⊕ ) 		Cycle time
(in days) 		Major semi-axis
(in AU ) 		eccentricity
YZ Ceti b 2017 0.75 ± 0.13 1.96876 ± 0.00021 0.01557 ± 0.00052 0.0 ± 0.12
YZ Ceti c 2017 0.98 ± 0.14 3.06008 ± 0.00022 0.02090 ± 0.00070 0.04 ± 0.11
YZ Ceti d 2017 1.14 ± 0.17 4.65627 ± 0.00042 0.02764 ± 0.00093 0.129 ± 0.096

Closest neighbors

YZ Ceti is unusually close to Tau Ceti , a yellow dwarf star belonging to the spectral class G8. Both stars are only about 1.6 light years apart. This is only a little more than a third of the distance between the Sun and its closest neighbor, Proxima Centauri . As with YZ Ceti, a planetary system has also been detected around Tau Ceti.

See also

List of nearest stars

Individual evidence

  1. ↑ a b c d e f g h i YZ Cet. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed September 16, 2018 .
  2. ↑ a b YZ Cet. In: VSX. AAVSO, accessed September 16, 2018 .
  3. ↑ a b c d e f g N. Astudillo-Defru et al .: The HARPS search for southern extra-solar planets XLII. A system of Earth-mass planets around the nearby M dwarf YZ Cet . arxiv : 1708.03336 .
  4. ↑ Nearest stars until 10pc (Zakhozhaj, 1979–1996)
  5. ↑ a b P. E. Kervella, F. Arenou, F. Mignard, F. Thévenin: Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly . In: Astronomy & Astrophysics . 623, p. A72. arxiv : 1811.08902 . bibcode : 2019A & A ... 623A..72K . doi : 10.1051 / 0004-6361 / 201834371 .
  6. ↑ a b c YZ Cet c. In: Extrasolar Planets Encyclopaedia . Retrieved September 16, 2018 .