Gliese 436
{{Short description|Star in the constellation Leo}}
{{Starbox begin
| name = Gliese 436 / Noquisi
}}
{{Starbox observe
| epoch = J2000
| constell = Leo
| dec = {{DEC|+26|42|23.6508}}
}}
{{Starbox character
| appmag_1_passband = B
| appmag_2_passband = V
| appmag_3_passband = J
| appmag_3 = {{nowrap|6.900 ± 0.024}}
| appmag_4_passband = H
| appmag_4 = {{nowrap|6.319 ± 0.023}}
| appmag_5_passband = K
| appmag_5 = {{nowrap|6.073 ± 0.016}}
| variable =
}}
{{Starbox astrometry
| radial_v = {{val|+8.87|0.16}}
| prop_mo_ra = {{val|895.088|(26)}}
| prop_mo_dec = {{val|-813.550|(25)}}
| parallax = 102.3014
| p_error = 0.0302
}}
{{Starbox detail
| mass = 0.425{{±|0.009}}
| radius = 0.432{{±|0.011}}
| luminosity = 0.02463{{±|0.00029}}
| temperature = {{val|3477|46|44|fmt=commas}}
| metal_fe = -0.46{{±|0.31|0.24}}
| rotation = {{Val|39.9|0.8|u=d}}
}}
{{Starbox catalog
| names = {{odlist | name = Noquisi | 2MASS = J11421096+2642251 | GJ = 436 | HIP = 57087 | LTT = 13213 | LHS = 310 | Ross = 905 }}
}}
{{Starbox reference
| Simbad = LHS+310
| NSTED = GJ-436
}}
{{Starbox end}}
Gliese 436 is a red dwarf located {{Convert|31.9|ly|pc|abbr=off|lk=on}} away in the zodiac constellation of Leo. It has an apparent visual magnitude of 10.67, which is much too faint to be seen with the naked eye. However, it can be viewed with even a modest telescope of {{Convert|2.4|in|cm|abbr=on|sigfig=1}} aperture. In 2004, the existence of an extrasolar planet, Gliese 436 b, was verified as orbiting the star. This planet was later discovered to transit its host star.
Nomenclature
The designation Gliese 436 comes from the Gliese Catalogue of Nearby Stars. This was the 436th star listed in the first edition of the catalogue.
In August 2022, this planetary system was included among 20 systems to be named by the third NameExoWorlds project.{{cite web |url=https://www.nameexoworlds.iau.org/2022exoworlds |title=List of ExoWorlds 2022 |date=8 August 2022 |website=nameexoworlds.iau.org |publisher=IAU |access-date=27 August 2022 |archive-date=8 March 2023 |archive-url=https://web.archive.org/web/20230308103542/https://www.nameexoworlds.iau.org/2022exoworlds |url-status=live }} The approved names, proposed by a team from the United States, were announced in June 2023. Gliese 436 is named Noquisi and its planet is named Awohali, after the Cherokee words for "star" ({{wt|chr|ᏃᏈᏏ}}) and "eagle" ({{wt|chr|ᎠᏬᎭᎵ}}).
Properties
Gliese 436 is a M2.5V star, which means it is a red dwarf. Stellar models give both an estimated mass and size of about 43% that of the Sun. The same model predicts that the outer atmosphere has an effective temperature of 3,480 K, giving it the orange-red hue of an M-type star. Small stars such as this generate energy at a low rate, giving it only 2.5% of the Sun's luminosity.
Gliese 436 is older than the Sun by several billion years and it has an abundance of heavy elements (with masses greater than helium-4) less than half% that of the Sun. The projected rotation velocity is 1.0 km/s, and the chromosphere has a low level of magnetic activity. Gliese 436 is a member of the "old-disk population" with velocity components in the galactic coordinate system of U=+44, V=−20 and W=+20 km/s.
Planetary system
The star is orbited by one known planet, designated Gliese 436 b. The planet has an orbital period of 2.6 Earth days and transits the star as viewed from Earth. It has a mass of 22.2 Earth masses and is roughly 55,000 km in diameter, giving it a mass and radius similar to the ice giant planets Uranus and Neptune in the Solar System. In general, Doppler spectroscopy measurements do not measure the true mass of the planet, but instead measure the product m sin i, where m is the true mass and i is the inclination of the orbit (the angle between the line-of-sight and the normal to the planet's orbital plane), a quantity that is generally unknown. However, for Gliese 436 b, the transits enable the determination of the inclination, as they show that the planet's orbital plane is very nearly in the line of sight (i.e. that the inclination is close to 90 degrees). Hence the mass quoted is the actual mass. The planet is thought to be largely composed of hot ices with an outer envelope of hydrogen and helium, and is termed a "hot Neptune".{{cite journal | bibcode = 2007A&A...472L..13G | author = Gillon, M. | display-authors = etal | title = Detection of transits of the nearby hot Neptune GJ 436 b | journal = Astronomy and Astrophysics | volume = 472 | issue = 2 | pages = L13–L16 | date = 2007 | doi = 10.1051/0004-6361:20077799|arxiv = 0705.2219 | s2cid = 13552824 }}
{{OrbitboxPlanet begin
}}
{{OrbitboxPlanet
| exoplanet = b / Awohali
| mass_earth = {{val|21.36|0.20|0.21}}
| semimajor = {{val|0.028|0.01}}
| period = {{val|2.64388|0.00006}}
| eccentricity = {{val|0.152|0.009|0.008}}
| inclination = {{val|85.80|0.25|0.21}}
| radius_earth = 4.33 ± 0.18
}}
{{Orbitbox end}}
GJ 436 b's orbit is likely misaligned with its star's rotation.{{cite journal| title=A Spitzer Transmission Spectrum for the Exoplanet GJ 436b |date=2011| last1=Knutson | first1=Heather A.| doi=10.1088/0004-637X/735/1/27| journal=Astrophysical Journal| volume=735, 27 |issue=1|arxiv=1104.2901 |bibcode = 2011ApJ...735...27K | pages=27|s2cid=18669291}} In addition the planet's orbit is eccentric. Because tidal forces would tend to circularise the orbit of the planet on short timescales, this suggested that Gliese 436 b is being perturbed by an additional planet orbiting the star.{{cite journal|author=Deming, D. |display-authors=etal |title=Spitzer Transit and Secondary Eclipse Photometry of GJ 436b|date=2007|journal=The Astrophysical Journal|volume=667|issue=2|pages=L199–L202|doi=10.1086/522496|bibcode=2007ApJ...667L.199D|arxiv = 0707.2778 |s2cid=13349666 }}
===Claims of additional planets===
In 2008, a second planet, designated "Gliese 436 c" was claimed to have been discovered, with an orbital period of 5.2 days and an orbital semimajor axis of 0.045 AU.{{cite journal | author = Ribas, I. | author2 = Font-Ribera, S. | author3 = Beaulieu, J. P. | name-list-style = amp | title = A ~5 M⊙ Super-Earth Orbiting GJ 436?: The Power of Near-Grazing Transits | date = 2008 | journal = The Astrophysical Journal | volume = 677 | issue = 1 | pages = L59–L62 | doi = 10.1086/587961 | bibcode = 2008ApJ...677L..59R |arxiv = 0801.3230 | s2cid = 14132568 }} The planet was thought to have a mass of roughly 5 Earth masses and have a radius about 1.5 times larger than the Earth's. Due to its size, the planet was thought to be a rocky, terrestrial planet.{{cite web | url=http://www.space.com/scienceastronomy/080409-smallest-exoplanet.html | title=New Super-Earth is Smallest Yet | work=Space.com | date=9 April 2008 | access-date=2008-04-10 | archive-date=2010-10-30 | archive-url=https://web.archive.org/web/20101030081226/http://www.space.com/scienceastronomy/080409-smallest-exoplanet.html | url-status=live }} It was announced by Spanish scientists in April 2008 by analyzing its influence on the orbit of Gliese 436 b.{{cite news |title=Smallest planet outside solar system found |website=Reuters |date=9 April 2008 |archive-url=https://web.archive.org/web/20230607031428/https://www.reuters.com/article/scienceNews/idUSL0956988620080409 |archive-date=2023-06-07 |url-status=live |url=https://www.reuters.com/article/scienceNews/idUSL0956988620080409}} Further analysis showed that the transit length of the inner planet is not changing, a situation which rules out most possible configurations for this system. Also, if it did orbit at these parameters, the system would be the only "unstable" orbit on UA's Extrasolar Planet Interactions chart.[http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] {{Webarchive|url=https://web.archive.org/web/20160505160348/http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ |date=2016-05-05 }} The existence of this "Gliese 436 c" was thus regarded as unlikely,{{cite journal | author = Alonso, R. | display-authors = etal | title = Limits to the planet candidate GJ 436c | date = 2008 | journal = Astronomy and Astrophysics | volume = 487 | issue = 1 | pages = L5–L8 | doi = 10.1051/0004-6361:200810007 | bibcode = 2008A&A...487L...5A|arxiv = 0804.3030 | s2cid = 119194288 }} and the discovery was eventually retracted at the Transiting Planets conference in Boston, 2008.{{cite encyclopedia | url = http://voparis-exoplanet-new.obspm.fr/catalog/gj_436_b/ | title = Planet GJ 436 b | encyclopedia = The Extrasolar Planets Encyclopaedia | author = Schneider, J. | access-date = 2013-02-23 | url-status = dead | archive-url = https://web.archive.org/web/20141223004957/http://voparis-exoplanet-new.obspm.fr/catalog/gj_436_b/ | archive-date = 2014-12-23 }}
Despite the retraction, studies concluded that the possibility that there is an additional planet orbiting Gliese 436 remained plausible.{{cite journal|author=Bean, J. L.|author2=Seifahrt, A.|name-list-style=amp|title=Observational Consequences of the Recently Proposed Super-Earth Orbiting GJ436|date=2008|journal=Astronomy and Astrophysics|volume=487|issue=2|pages=L25–L28|doi=10.1051/0004-6361:200810278|bibcode=2008A&A...487L..25B|arxiv = 0806.3270 |s2cid=14811323}} With the aid of an unnoticed transit automatically recorded at NMSU on January 11, 2005, and observations by amateur astronomers, it has been suggested that there is a trend of increasing inclination of the orbit of Gliese 436 b, though this trend remains unconfirmed. This trend is compatible with a perturbation by a planet of less than 12 Earth masses on an orbit within about 0.08 AU of the star.{{cite journal|author=Coughlin, J. L. |display-authors=etal|title=New Observations and a Possible Detection of Parameter Variations in the Transits of Gliese 436b|date=2008|journal=The Astrophysical Journal|volume=689|issue=2|pages=L149–L152|doi=10.1086/595822|bibcode=2008ApJ...689L.149C|arxiv = 0809.1664 |s2cid=14893633}}
In July 2012, NASA announced that astronomers at the University of Central Florida, using the Spitzer Space Telescope, strongly believed they had observed a second planet.{{cite web
|url = http://www.smh.com.au/technology/sci-tech/alien-exoplanet-smaller-than-earth-discovered-20120719-22bc4.html
|title = Alien exoplanet smaller than Earth discovered
|agency = Reuters
|date = July 2012
|publisher = Sydney Morning Herald
|access-date = 2012-07-19
|archive-date = 2014-04-11
|archive-url = https://web.archive.org/web/20140411104522/http://www.smh.com.au/technology/sci-tech/alien-exoplanet-smaller-than-earth-discovered-20120719-22bc4.html
|url-status = live
}} This candidate planet was given the preliminary designation UCF-1.01, after the University of Central Florida.{{cite web |url=https://www.orlandosentinel.com/2012/07/18/planet-ucf-101-is-introduced-to-the-world-of-astronomy/ |title=Planet UCF 1.01 is introduced to the world of astronomy |date=July 18, 2012 |access-date=July 20, 2012 |last=Powers |first=Scott |work=Orlando Sentinel |archive-date=September 7, 2015 |archive-url=https://web.archive.org/web/20150907182920/http://articles.orlandosentinel.com/2012-07-18/news/os-ucf-planet-discovey-20120718_1_earth-size-planets-red-dwarf-star-nasa-spitzer-space-telescope |url-status=live }} It was measured to have a radius of around two thirds that of Earth and, assuming an Earth-like density of 5.5 g/cm3, was estimated to have a mass of 0.3 times that of Earth and a surface gravity of around two thirds that of Earth. It was thought to orbit at 0.0185 AU from the star, every 1.3659 days. The astronomers also believed they had found some evidence for an additional planet candidate, UCF-1.02, which is of a similar size, though with only one detected transit its orbital period is unknown. Follow up observations with the Hubble Space Telescope as well as a reanalysis of the Spitzer Space Telescope data were unable to confirm these planets.
See also
References
{{reflist|refs=
{{Cite Gaia DR3|4017860992519744384}}
{{cite journal | last1=Bean | first1=Jacob L. | last2=Benedict | first2=G. Fritz | last3=Endl | first3=Michael | title=Metallicities of M Dwarf Planet Hosts from Spectral Synthesis | journal=The Astrophysical Journal | date=2006 | volume=653 | issue=1 | pages=L65–L68 | bibcode=2006ApJ...653L..65B | doi=10.1086/510527 | type=abstract | arxiv=astro-ph/0611060 | s2cid=16002711 }}—for the metallicity, note that or 48%
{{cite journal |doi=10.1086/421374
| title=Meeting the Cool Neighbors. VIII. A Preliminary 20 Parsec Census from the NLTT Catalogue
| journal=The Astronomical Journal | volume=128
| issue=1 |pages=463 |bibcode=2004AJ....128..463R |arxiv=astro-ph/0404061 |last1=Reid |first1=I. Neill |last2=Cruz |first2=Kelle L. |last3=Allen |first3=Peter R. |last4=Mungall |first4=Finlay |last5=Kilkenny |first5=David |last6=Liebert |first6=James |last7=Hawley |first7=Suzanne L. |last8=Fraser |first8=Oliver J. |last9=Covey |first9=Kevin R. |last10=Lowrance |first10=Patrick |last11=Kirkpatrick |first11=J. Davy |last12=Burgasser |first12=Adam J. |year=2004 |s2cid=28314795 |url=https://cds.cern.ch/record/728686 |type=Submitted manuscript }}
| display-authors=1
| last1=Suárez Mascareño | first1=A. | last2=Rebolo | first2=R.
| last3=González Hernández | first3=J. I. | last4=Esposito | first4=M.
| title=Rotation periods of late-type dwarf stars from time series high-resolution spectroscopy of chromospheric indicators
| journal=Monthly Notices of the Royal Astronomical Society
| volume=452 | issue=3 | pages=2745–2756 | date=September 2015
| doi=10.1093/mnras/stv1441 | doi-access=free | bibcode=2015MNRAS.452.2745S
| arxiv=1506.08039 | s2cid=119181646 | postscript=.
}}
{{cite simbad | title=Gliese 436 | access-date=2018-10-06}}
| title=The M-dwarf Ultraviolet Spectroscopic Sample. I. Determining Stellar Parameters for Field Stars
| last1=Pineda | first1=J. Sebastian | last2=Youngblood | first2=Allison
| last3=France | first3=Kevin | display-authors=1
| journal=The Astrophysical Journal
| volume=918 | issue=1 | id=40 | pages=23 | date=September 2021
| doi=10.3847/1538-4357/ac0aea | arxiv=2106.07656
| bibcode=2021ApJ...918...40P | s2cid=235435757 | doi-access=free }}
{{cite web |url=https://www.nameexoworlds.iau.org/2022approved-names |title=2022 Approved Names |website=nameexoworlds.iau.org |publisher=IAU |access-date=7 June 2023 |archive-date=1 May 2024 |archive-url=https://web.archive.org/web/20240501010333/https://nameexoworlds.iau.org/2022approved-names |url-status=live }}
}}
External links
- {{cite web
| url=http://solstation.com/stars2/gl436.htm
| title=Gliese 436 / AC+27 28217
| publisher=Sol Company
| access-date=2007-11-28
| archive-date=2015-09-13
| archive-url=https://web.archive.org/web/20150913055200/http://solstation.com/stars2/gl436.htm
| url-status=dead
}}
- {{cite web
| url=http://media4.obspm.fr/exoplanets/base/etoile.php?nom=GJ+436
| title=GJ 436
| publisher=l'Observatoire de Paris
| access-date=2009-05-20
| archive-url=https://web.archive.org/web/20120401193040/http://media4.obspm.fr/exoplanets/base/etoile.php?nom=GJ+436
| archive-date=2012-04-01
| url-status=dead
}}
- {{cite web
| url=http://news.NationalGeographic.com/news/2012/07/120719-new-planet-ucf-spitzer-science-space-stevenson
| archive-url=https://web.archive.org/web/20120720194534/http://news.nationalgeographic.com/news/2012/07/120719-new-planet-ucf-spitzer-science-space-stevenson/
| url-status=dead
| archive-date=July 20, 2012
| title=New Planet Found: Molten "Mars" Is "Right Around the Corner"
| publisher=National Geographic
| access-date=2012-07-20}}
{{Sky|11|42|11.0941|+|26|42|23.652|33.4}}
{{Stars of Leo}}
{{DEFAULTSORT:Gliese 436}}
Category:M-type main-sequence stars
Category:Planetary transit variables
Category:Planetary systems with one confirmed planet
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