4 Ursae Majoris#Planetary system

{{about|π² Ursae Majoris|other stars with this Bayer designation|pi Ursae Majoris{{!}}π Ursae Majoris}}

{{Starbox begin

| name = Pi² Ursae Majoris

}}

{{Starbox image

| image ={{Location map|100x100

|AlternativeMap=Ursa Major IAU.svg

|caption=

|alt=Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings

|width=320

|lat=79.7 |long=68.6

|mark=Cercle rouge 100%.svg | marksize=12

|float=center

}}| caption=Location of π² Ursae Majoris (circled) near the center

}}

{{Starbox observe

| epoch = J2000.0

| constell = Ursa Major

| ra = {{RA|08|40|12.8172}}

| dec = {{DEC|+64|19|40.570}}

| appmag_v = +4.620

}}

{{Starbox character

| class = K2 III

| r-i =

| v-r =

| b-v = +1.159

| u-b = +1.193

| variable =

}}

{{Starbox astrometry

| radial_v = +14.62

| prop_mo_ra = {{val|−59.861|(80)}}

| prop_mo_dec = {{val|26.544|(88)}}

| pm_footnote =

| parallax = 13.2035

| p_error = 0.1164

| parallax_footnote =

| absmag_v = 0.150

}}

{{Starbox detail

| mass = {{nowrap|1.234 ± 0.15}}

| radius = {{val|18.79|0.38}}

| gravity = {{nowrap|1.8 ± 0.15}}

| luminosity = {{val|112.4|10.0}}

| temperature = {{val|4336|99}}

| metal_fe = {{nowrap|-0.25 ± 0.04}}

| rotational_velocity = 8

| age_gyr = {{nowrap|4.18 ± 1.95}}

}}

{{Starbox catalog

| names = π² Ursae Majoris, π² UMa, Pi² UMa, 4 Ursae Majoris, BD+64°698, FK5 2677, GC 11850, HD 73108, HIP 42527, HR 3403, PPM 16713, SAO 14616

}}

{{Starbox reference

| Simbad = HD+73108

| ARICNS =

}}

4 Ursae Majoris (sometimes abbreviated 4 UMa) is the Flamsteed designation of a star in the northern circumpolar constellation of Ursa Major. It also bears the Bayer designation of Pi² Ursae Majoris (Pi² UMa, π² Ursae Majoris, π² UMa) and is traditionally named Muscida. With an apparent visual magnitude of +4.6, this star is visible from suburban or darker skies based upon the Bortle Dark-Sky Scale. From parallax measurements made during the Gaia mission, this star is at a distance of {{Convert|247|ly|pc|abbr=off|lk=on}} from Earth. {{As of|2011}}, one extrasolar planet has been confirmed to be orbiting the star.

Properties

This star has a stellar classification of K2 III, indicating that, at an estimated age of around four billion years, it is an evolved star that has reached the giant stage. It has a mass about 1.2 times larger than the Sun, but has expanded to 18 times the Sun's girth. The effective temperature of the star's outer atmosphere is {{val|4415|fmt=commas|ul=K}}. This heat gives it the cool, orange-hued glow of a K-type star.

Pi² Ursae Majoris is a member of the Milky Way galaxy's thin disk population. It is following an orbit through the galaxy with an eccentricity of 0.10, which carries it as close to the Galactic Center as {{convert|27.7|kly|kpc|abbr=off}} and as far as {{cvt|34.1|kly|kpc}}. The inclination of this orbit lies close to the galactic plane, so it departs this plane by no more than {{cvt|260|ly|pc}}.

Planetary system

Based upon observed radial velocity changes in the star, in 2007 the presence of a planetary companion was announced. The planet, designated 4 Ursae Majoris b, is at least seven times more massive than Jupiter. Its orbit is eccentric, orbiting 4 Ursae Majoris at 87% the distance from Sun to Earth. Compared to the Sun, this star has a lower abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity. This is curious, because most main-sequence stars with planets tend to have a higher abundance of metals.

{{OrbitboxPlanet begin

| table_ref =

}}

{{OrbitboxPlanet

| exoplanet = b

| mass = >7.1 ± 1.6

| period = 269.3 ± 1.96

| semimajor = 0.87 ± 0.04

| eccentricity = 0.432 ± 0.024

}}

Naming and etymology

With π¹, σ¹, σ², ρ, A and d, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle. According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Ṭhibā were the title for seven stars: A as Althiba I, π¹ as Althiba II, this star (π²) as Althiba III, ρ as Althiba IV, σ¹ as Althiba V, σ² as Althiba VI, and d as Althiba VII.

References

{{reflist|refs=

{{citation | display-authors=1 | last1=Soubiran | first1=C. | last2=Bienaymé | first2=O. | last3=Mishenina | first3=T. V. | last4=Kovtyukh | first4=V. V. | title=Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants | journal=Astronomy and Astrophysics | year=2008 | volume=480 | issue=1 | pages=91–101 | bibcode=2008A&A...480...91S | doi=10.1051/0004-6361:20078788 |arxiv = 0712.1370 | s2cid=16602121 }}

{{citation | display-authors=1 | last1=Famaey | first1=B. | last2=Jorissen | first2=A. | last3=Luri | first3=X. | last4=Mayor | first4=M. | last5=Udry | first5=S. | last6=Dejonghe | first6=H. | last7=Turon | first7=C. | title=Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters | journal=Astronomy and Astrophysics | volume=430 | pages=165–186 | doi=10.1051/0004-6361:20041272 | bibcode=2005A&A...430..165F |arxiv = astro-ph/0409579 |date=January 2005| s2cid=17804304 }}

{{citation | last1=Bernacca | first1=P. L. | first2=M. | last2=Perinotto | title=A catalogue of stellar rotational velocities | journal=Contributi Osservatorio Astronomico di Padova in Asiago | volume=239 | issue=1 | year=1970 | bibcode=1970CoAsi.239....1B | page=1 }}

{{citation | last1=Jennens | first1=P. A. | last2=Helfer | first2=H. L. | title=A new photometric metal abundance and luminosity calibration for field G and K giants | journal=Monthly Notices of the Royal Astronomical Society | volume=172 | issue=3 | pages=667–679 | bibcode=1975MNRAS.172..667J |date=September 1975 | doi=10.1093/mnras/172.3.667| doi-access=free }}

{{citation | title=Discovery of a planet around the K giant star 4 Ursae Majoris | display-authors=1 | last1=Döllinger | first1=M. P. | last2=Hatzes | first2=A. P. | last3=Pasquini | first3=L. | last4=Guenther | first4=E. W. | last5=Hartmann | first5=M. | last6=Girardi | first6=L. | last7=Esposito | first7=M. | journal=Astronomy and Astrophysics | volume=472 | issue=2 | pages=649–652 | year=2007 | type =abstract | doi=10.1051/0004-6361:20066987 | bibcode=2007A&A...472..649D | arxiv=astro-ph/0703672 | s2cid=17662368 }}

{{citation|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20120222183238/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=February 22, 2012 }}

{{cite journal | title=Angular Diameters and Effective Temperatures of 25 K Giant Stars from the CHARA Array | last1=Baines | first1=Ellyn K. | last2=Döllinger | first2=Michaela P. | last3=Cusano | first3=Felice | last4=Guenther | first4=Eike W. | last5=Hatzes | first5=Artie P. | last6=McAlister | first6=Harold A. | last7=ten Brummelaar | first7=Theo A. | last8=Turner | first8=Nils H. | last9=Sturmann | first9=Judit | last10=Sturmann | first10=Laszlo | last11=Goldfinger | first11=P. J. | last12=Farrington | first12=Christopher D. | last13=Ridgway | first13=Stephen T. | display-authors=1 | journal=Astrophysical Journal | volume=710 | issue=2 | pages=1365–1374 | year=2010 | arxiv=0912.5491 | bibcode=2010ApJ...710.1365B | doi=10.1088/0004-637X/710/2/1365 | s2cid=799107 }}

{{citation | title=Star-Names and Their Meanings | last=Allen | first=Richard Hinckley | author-link=Richard Hinckley Allen | date=1899 | publisher=G. E. Stechert | location=New York | page=444 }}

{{citation | url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf | first1=Jack W. | last1=Rhoads | title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars | publisher=Jet Propulsion Laboratory, California Institute of Technology | date=November 15, 1971 | postscript=. }}

}}

External links

{{cite encyclopedia |url=http://exoplanet.eu/star.php?st=4+Uma |title=Notes for star 4 Uma |author=Jean Schneider |year=2011 |access-date=3 October 2011 |archive-date=10 February 2012 |archive-url=https://web.archive.org/web/20120210042059/http://exoplanet.eu/star.php?st=4+Uma |encyclopedia=Extrasolar Planets Encyclopaedia |url-status=dead }}

Category:K-type giants

Althiba III

Category:Durchmusterung objects