HAT-P-21#Planetary system

{{Starbox observe

| epoch = J2000

| constell = Ursa Major

| ra = {{RA|11|25|05.9859}}

| dec = {{DEC|+41|01|40.665}}

| appmag_v = 11.46

}}

{{Starbox character

| class = G3V

}}

{{Starbox astrometry

| radial_v = {{val|-51.87|0.48}}

| prop_mo_ra = {{val|−1.142|(17)}}

| prop_mo_dec = {{val|13.523|(24)}}

| pm_footnote =

| parallax = 3.5190

| p_error = 0.0228

| parallax_footnote =

}}

{{Starbox detail

| source = {{citation|arxiv=1609.04389|year=2016|doi=10.3847/1538-3881/aa5df3|last1=Stassun|first1=Keivan G.|last2=Collins|first2=Karen A.|last3=Gaudi|first3=B. Scott|title=Accurate Empirical Radii and Masses of Planets and Their Host Stars with Gaia Parallaxes|journal=The Astronomical Journal|volume=153|issue=3|page=136|bibcode=2017AJ....153..136S |s2cid=119219062 |doi-access=free }}{{citation|arxiv=1503.09111|title=A comparison of gyrochronological and isochronal age estimates for transiting exoplanet host stars|year=2015|doi=10.1051/0004-6361/201525774|last1=Maxted|first1=P. F. L.|last2=Serenelli|first2=A. M.|last3=Southworth|first3=J.|journal=Astronomy & Astrophysics|volume=577|pages=A90|bibcode=2015A&A...577A..90M|s2cid=53324330}}

| mass = 0.947{{±|0.042}}

| radius = 1.105{{±|0.083}}

| gravity = 4.33{{±|0.06}}

| luminosity = 1.06{{±|0.20|0.16}}

| temperature = 5634{{±|67}}

| metal = 0.04{{±|0.08}}

| rotation = 15.88{{±|0.02}} d

| rotational_velocity =3.5{{±|0.5}}

| age_gyr = 10.2{{±|2.5}}

}}

{{Starbox catalog

| names = {{odlist | name=Mazaalai | name2=HAT-P-21 | GSC=03013-01229 | 2MASS=J11250598+4101406 | TIC=17993892 | TOI=1800 | TYC=3013-1229-1}}

}}

{{Starbox reference

| Simbad = HAT-P-21

| NSTED = HAT-P-21

}}

HAT-P-21, also named Mazaalai, is a G-type main-sequence star about 927 light-years away. The star has amount of metals similar to solar abundance. The survey in 2015 has failed to detect any stellar companions.{{citation|arxiv=1507.01938|title=A Lucky Imaging search for stellar companions to transiting planet host stars|year=2015|doi=10.1051/0004-6361/201424091|last1=Wöllert|first1=Maria|last2=Brandner|first2=Wolfgang|last3=Bergfors|first3=Carolina|last4=Henning|first4=Thomas|journal=Astronomy & Astrophysics|volume=575|pages=A23|bibcode=2015A&A...575A..23W|s2cid=119250579}} The star is rotating rapidly, being spun up by the tides of giant planet on close orbit.

Naming

In 2019, the star HAT-P-21 received the proper name Mazaalai while its planet HAT-P-21b received the name Bambaruush in the international NameExoWorlds contest. These names refer to the Mongolian name for the endangered Gobi bear subspecies, and the Mongolian term for 'bear cub', respectively. Mazaalai was also the name of Mongolia's first satellite.{{Cite web |url=http://www.nameexoworlds.iau.org/final-results |title=IAU 100 NameExoWorlds Approved Names |access-date=2020-07-08 |archive-date=2019-12-19 |archive-url=https://web.archive.org/web/20191219084750/http://www.nameexoworlds.iau.org/final-results |url-status=dead }} Some IAU publications have misspelled the star's name as Mazalaai, but the latest IAU Catalog of Star Names lists Mazaalai.

Planetary system

In 2010 a transiting hot super-Jovian planet on moderately eccentric orbit was detected. Its equilibrium temperature is 1283{{±|50}} K. The transit-timing variation survey in 2011 have failed to rule out or confirm the existence of additional planets in the system, until the orbital parameters of HAT-P-21b are known with better precision.{{citation|arxiv=1109.0936|title=Prospecting transit duration variations in extrasolar planetary systems|year=2011|doi=10.1051/0004-6361/201117207|last1=Damiani|first1=C.|last2=Lanza|first2=A. F.|journal=Astronomy & Astrophysics|volume=535|pages=A116|bibcode=2011A&A...535A.116D|s2cid=118460941}}

The planetary orbit is likely aligned with the equatorial plane of the star, misalignment equal to 25{{±|16}} degrees.{{citation|arxiv=2205.10549|year=2022|title=The GAPS Programme at TNG|doi=10.1051/0004-6361/202243742 |last1=Mancini |first1=L. |last2=Esposito |first2=M. |last3=Covino |first3=E. |last4=Southworth |first4=J. |last5=Poretti |first5=E. |last6=Andreuzzi |first6=G. |last7=Barbato |first7=D. |last8=Biazzo |first8=K. |last9=Borsato |first9=L. |last10=Bruni |first10=I. |last11=Damasso |first11=M. |last12=Di Fabrizio |first12=L. |last13=Evans |first13=D. F. |last14=Granata |first14=V. |last15=Lanza |first15=A. F. |last16=Naponiello |first16=L. |last17=Nascimbeni |first17=V. |last18=Pinamonti |first18=M. |last19=Sozzetti |first19=A. |last20=Tregloan-Reed |first20=J. |last21=Basilicata |first21=M. |last22=Bignamini |first22=A. |last23=Bonomo |first23=A. S. |last24=Claudi |first24=R. |last25=Cosentino |first25=R. |last26=Desidera |first26=S. |last27=Fiorenzano |first27=A. F. M. |last28=Giacobbe |first28=P. |last29=Harutyunyan |first29=A. |last30=Henning |first30=Th. |journal=Astronomy & Astrophysics |volume=664 |pages=A162 |s2cid=248986121 |display-authors=1 }}

File:Exoplanet Comparison HAT-P-21 b.png

{{OrbitboxPlanet begin

| table_ref = {{citation|arxiv=1910.11438|title=Light Curve Analysis of Ground-Based Data from Exoplanets Transit Database|year=2020|doi=10.1016/j.newast.2019.101305|last1=Davoudi|first1=F.|last2=Jafarzadeh|first2=S.J.|last3=Poro|first3=A.|last4=Basturk|first4=O.|last5=Mesforoush|first5=S.|last6=Fasihi Harandi|first6=A.|last7=Gozarandi|first7=M.J.|last8=Zare Mehrjardi|first8=Z.|last9=Maley|first9=P.D.|last10=Khakpash|first10=S.|last11=Rokni|first11=K.|last12=Sarostad|first12=A.|journal=New Astronomy|volume=76|page=101305|bibcode=2020NewA...7601305D|s2cid=202931761}}

}}

{{OrbitboxPlanet

| exoplanet = b (Bambaruush)

| mass = 4.063{{±|0.161}}

| radius = 1.08{{±|0.18}}

| semimajor = 0.0494{{±|0.0007}}

| period = 4.124481{{±|0.000007}}

| eccentricity = 0.228{{±|0.016}}

| inclination = 88.6

}}

References

{{Reflist|refs=

{{citation|arxiv=1008.3388|title=HAT-P-20b–HAT-P-23b: FOUR MASSIVE TRANSITING EXTRASOLAR PLANETS|year=2010|doi=10.1088/0004-637X/742/2/116|last1=Bakos|first1=G. Á.|last2=Hartman|first2=J.|last3=Torres|first3=G.|last4=Latham|first4=D. W.|last5=Kovács|first5=Géza|last6=Noyes|first6=R. W.|last7=Fischer|first7=D. A.|last8=Johnson|first8=J. A.|last9=Marcy|first9=G. W.|last10=Howard|first10=A. W.|last11=Kipping|first11=D.|last12=Esquerdo|first12=G. A.|last13=Shporer|first13=A.|last14=Béky|first14=B.|last15=Buchhave|first15=L. A.|last16=Perumpilly|first16=G.|last17=Everett|first17=M.|last18=Sasselov|first18=D. D.|last19=Stefanik|first19=R. P.|last20=Lázár|first20=J.|last21=Papp|first21=I.|last22=Sári|first22=P.|journal=The Astrophysical Journal|volume=742|issue=2|page=116|bibcode=2011ApJ...742..116B |s2cid=119182075}}

{{cite web |title=IAU Catalog of Star Names |url=https://exopla.net/star-names/modern-iau-star-names/ |access-date=23 May 2025}}

}}

Category:Ursa Major

Category:G-type main-sequence stars

Category:Planetary systems with one confirmed planet

Category:Planetary transit variables