Chalawan

Database links to 47 Ursae Majoris

Star Chalawan
Position of Chalawan on Psi Ursae Majoris
AladinLite
Observation dates equinox :  J2000.0 , epoch : J2000.0
Constellation	Big Bear
Right ascension	10 h 59 m 27.97 s
declination	+ 40 ° 25 ′ 48.9 ″
Apparent brightness	5.1 mag
Typing
Known exoplanets	3
B − V color index	+0.61
U − B color index	+0.13
R − I index	0.31
Spectral class	G1 V
Astrometry
Radial velocity	(+12.6 ± 0.9) km / s
parallax	(71.11 ± 0.25)  mas
distance	(45.87 ± 0.16)  ly (14.06 ± 0.05)  pc
Visual absolute brightness M vis	approx. +4.3 mag
Proper movement
Rec. Share:	(−315.92 ± 0.62)  mas / a
Dec. portion:	(+55.15 ± 0.50)  mas / a
Physical Properties
Dimensions	≈ 1  M ☉
radius	approx. 1.3  R ☉
Luminosity	approx. 1.5  L ☉
Effective temperature	5855  K
Age	approx. 6 · 10 9  a
Other names and catalog entries
Flamsteed name 47 Ursae Majoris Bonn survey BD + 41 ° 2147 Bright Star Catalog HR 4277 [1] Henry Draper Catalog HD 95128 [2] Hipparcos catalog HIP 53721 [3] SAO catalog SAO 43557 [4] Tycho catalog TYC 3009-2703-1 [5] Other names Gliese 407 • FK5  1282

Chalawan ( 47 Ursae Majoris , abbreviated: 47 UMa ) is a yellow dwarf similar to the Sun , located around 46 light-years away in the constellation Great Bear . The star has a planetary system that has been shown to consist of three exoplanets .

Origin of name

The original name of the star was 47 Ursae Majoris . After a publicly advertised IAU competition , Chalawan received its official name on December 15, 2015, after a crocodile king in the mythology of Thai folk beliefs.

Distance and visibility

Chalawan is relatively close to our solar system . Due to the astrometric parallax measurement by the Hipparcos satellite, which showed a parallax of about 71  milli-arcseconds , the star is at a distance of about 14.1 parsecs . Since the star has an apparent magnitude of 5.1, it is possible, under good conditions, to see this star in the night sky with the naked eye.

Stellar properties

The mass of Chalawan is roughly the same as that of the Sun, but the star has around 10% more iron than the Sun. The spectral type of Chalawan is G1V, which is why it is slightly warmer than the sun with just under 5855 K surface temperature. The absolute brightness is +4.29 magnitudes . This means that its luminosity is about 60% greater than that of the sun. Like the Sun, Chalawan is on the main sequence in the HR diagram . It converts in its core by means of nuclear fusion so hydrogen to helium to. Due to chromospheric activity , the star is estimated to be just under 6 billion years old, although evolutionary models suggest an age of 8.7 billion years.

Planetary system

The orbits of the planets of Chalawan (black) and the solar system (blue) in comparison

In 1996 the two American astronomers Geoffrey Marcy and R. Paul Butler demonstrated that Chalawan is orbited by a planet. This discovery was based on measurements of the star's radial velocity , which is easily affected by orbiting planets. These measurements were made using the Doppler effect in the star's spectrum . The planet with a little more than two and a half times the mass of Jupiter was named Taphao Thong and orbits its central star once in around 1078 days.

A second planet, called Taphao Kaew , was discovered in 2001 by Debra Fischer , Geoffrey Marcy and R. Paul Butler, again using the radial velocity method. It takes about 2391 days to complete one orbit and has about half the mass of Jupiter .

Both planets are in a similar configuration to Jupiter and Saturn in the solar system. The ratio of the cycle times is around 5: 2 in both systems, and the mass ratio is also identical. The smaller order of magnitude and the larger masses also imply that there are stronger mutual gravitational influences between the two planets than between Saturn and Jupiter. From this it follows that the true masses of the planets cannot be much larger than the minimum masses determined by the radial velocity measurements.

Following further analysis of the star's radial velocity data using Bayesian statistics , Philip C. Gregory and Debra Fischer announced in 2010 the discovery of a third planet, 47 Ursae Majoris d . It is located significantly further from its central star (approx. 11.6 AU) and takes about 38 years to complete one orbit. Its minimum mass is 1.6 times the mass of Jupiter.

Simulations show that in the inner area of ​​the habitable zone (the zone around a star where life could exist) of Chalawan a rocky planet could exist in a stable orbit. However, the presence of a gas giant within 2.5 AU of the star may have disrupted the formation of planets and water resources on them. Any planets in the habitable zone of Chalawan are therefore likely to be small and arid.

Chalawan planetary system

Planet (by distance from the star)	Discovery (year)	Mass (in M ♃ )	Cycle time (in days)	Major semi-axis (in AU )	eccentricity
Taphao Thong	1996	2.53 +0.07−0.06	1078 ± 2	2.100 ± 0.02	0.032 ± 0.014
Taphao Kaew	2001	0.540 +0.066−0.073	2391 +100−87	3.6 ± 0.1	0.098 +0.047−0.096
47 Ursae Majoris d	2010	1.64 +0.29−0.48	14002 +4018−5095	11.6 +2.1−2.9	0.16 +0.09−0.16

Individual evidence

1. ↑ ^{a b c d e} SIMBAD database
2. ↑ ^{a b c} Bright Star Catalog
3. ↑ ^{a b} Hipparcos catalog
4. ↑ HIP 53721 The Hipparcos and Tychokatalog. ESA (1997). (July 22, 2006)
5. ^ R. Butler et al .: Catalog of Nearby Exoplanets . In: The Astrophysical Journal . Volume 646, 2006, pp. 505-522.
6. ↑ Exoplanets Data Explorer . Exoplanets.org. Retrieved June 26, 2010.
7. ^ C. Saffe et al .: On the Ages of Exoplanet Host Stars . In: Astronomy and Astrophysics . Volume 443, No. 2, 2005, pp. 609-626.
8. ↑ Marcy, G .; Butler, RP: A Planet Orbiting 47 Ursae Majoris. Retrieved May 10, 2015 . 
9. ^ Fischer, DA et al .: A Second Planet Orbiting 47 Ursae Majoris . bibcode : 2002ApJ ... 564.1028F .
10. ↑ Gregory, PC; Fischer, DA: A Bayesian Periodogram Finds Evidence for Three Planets in 47 Ursae Majoris . arxiv : 1003.5549 .
11. ↑ Jones, BW; Underwood, DR; Sleep, PN: Prospects for Extrasolar "Earths" in Habitable Zones . arxiv : astro-ph / 0503178 .
12. ^ Raymond, SN: The Search for other Earths: limits on the giant planet orbits that allow habitable terrestrial planets to form . arxiv : astro-ph / 0605136 .
13. ↑ ^{a b c} NASA Exoplanet Archives: 47 UMa. Retrieved May 10, 2015 . 

Web links

Commons : 47 Ursae Majoris  - Collection of images, videos and audio files

• SolStation.com: 47 Ursae Majoris. Retrieved May 12, 2015 .