LP 890-9

{{Short description|Red dwarf star with Earth-like planet}} {{Starbox begin | name = LP 890-9 }} {{Starbox observe | epoch = [[J2000]] | constell = [[Eridanus (constellation)|Eridanus]]<ref>{{cite constellation|LP 890-9}}</ref> | ra = {{RA|04|16|31.16176}}<ref name="GaiaDR3"/> | dec = {{DEC|-28|18|52.9543}}<ref name="GaiaDR3"/> | appmag_v = {{val|18.0|0.2}}<ref name="Delrez2022"/> }} {{Starbox character | type = [[Main sequence]]<ref name="Delrez2022"/> | class = M6V<ref name="Kaltenegger2022"/> | appmag_1_passband = V | appmag_1 = {{val|18.0|0.2}}<ref name="Delrez2022"/> | appmag_2_passband = G | appmag_2 = {{val|15.791|0.003}}<ref name="GaiaDR3"/> | appmag_3_passband = J | appmag_3 = {{val|12.258|0.023}}<ref name="Delrez2022"/> | appmag_4_passband = H | appmag_4 = {{val|11.692|0.025}}<ref name="Delrez2022"/> | appmag_5_passband = K | appmag_5 = {{val|11.344|0.023}}<ref name="Delrez2022"/> }} {{Starbox astrometry | radial_v = {{val|28.84|2.84}}<ref name="GaiaDR3"/> | prop_mo_ra = {{val|218.569}} | prop_mo_dec = {{val|-251.145}} | pm_footnote = <ref name="GaiaDR3"/> | parallax = 30.9326 | p_error = 0.0418 | parallax_footnote = <ref name="GaiaDR3"/> | absmag_v = {{val|15.45|0.2}}<ref name="absmag" group="note"/> | absmag_bol = }} {{Starbox detail | source = <ref name="Delrez2022"/> | mass = {{val|0.118|0.002}} | radius = {{val|0.1532|0.0048|0.0024}} | luminosity_bolometric = {{val|0.001438|0.000037}} | habitable_inner = | habitable_outer = | gravity = {{val|5.139|0.013|0.028}} | temperature = {{val|2871|32|45}} | metal_fe = {{val|−0.028|0.089}} | rotation = | rotational_velocity = | age_gyr = {{val|7.2|2.2|3.1}} }} {{Starbox catalog | names = {{odlist | name = SPECULOOS-2 | 2MASS = J04163114-2818526 | LP = 890-9 | NLTT = 12925 | TIC = 44898913 | TOI = 4306 | WISEA = J041631.33-281855.5}}<ref name="SIMBAD"/> }} {{Starbox reference | Simbad = LP+890-9 | NSTED = LP-890-9 }} {{Starbox end}}

'''LP 890-9''', also known as '''SPECULOOS-2''' or '''TOI-4306''', is a high proper motion [[red dwarf]] star located {{convert|105|ly|pc|lk=on}} away from the [[Solar System]] in the constellation of [[Eridanus (constellation)|Eridanus]]. The star has 12% the mass and 15% the radius of the [[Sun]], and a temperature of {{convert|2871|K|C F|lk=on}}. It is extremely faint and, with an [[apparent magnitude]] of 18, is the faintest star with exoplanets discovered by the [[Transiting Exoplanet Survey Satellite]].<ref>{{Cite web |title=Planetary Systems |url=https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PS&constraint=default_flag=1&constraint=disc_facility+like+%27%25TESS%25%27 |access-date=2024-02-18 |website=exoplanetarchive.ipac.caltech.edu}}</ref>

== Planetary system ==

In 2022, two [[exoplanet]]s were discovered in orbit around this star. The first planet, LP 890-9 b, was initially identified using [[Transiting Exoplanet Survey Satellite|TESS]]. Further observations using [[SPECULOOS]] confirmed this planet and discovered a second planet, LP 890-9 c. Both planets are likely [[terrestrial planet]]s, somewhat larger than Earth. The outer planet LP 890-9 c orbits within the [[habitable zone]], and is a favorable target for atmospheric characterization using [[James Webb Space Telescope|JWST]].<ref name="Delrez2022"/><ref name="ULiège"/>

LP 890-9 c orbits near the inner edge of the conservative habitable zone, and models differ as to whether the planet is more likely to resemble [[Earth]] or [[Venus]]. Spectra from JWST should make it possible to distinguish between these two scenarios.<ref name="Kaltenegger2022"/> The planet is [[tidally locked]] to its host, meaning it has no [[day-night cycle]] like Earth.<ref>{{cite news |title=Two potentially habitable super-Earth planets have been discovered |url=https://www.newscientist.com/article/2337024-two-potentially-habitable-super-earth-planets-have-been-discovered/ |access-date=8 September 2022 |work=New Scientist |date=2022}}</ref> While the planet's location in the [[habitable zone]] suggests a strong possibility of an Earth-like atmosphere and climate, the planet's large size may count against its habitability. In addition, the planet is close enough to its star that the powerful [[radiation]] may reduce its chances of habitability.<ref>{{cite news |title=Astronomers spot 2 intriguing alien worlds around ultracool star |url=https://www.space.com/exoplanet-discovery-around-ultracool-dwarf-star |access-date=8 September 2022 |work=Space.com |date=7 September 2022 |language=en}}</ref> Another challenge for the potential habitability of LP 890-9 c is the magma ocean that would have formed during its infancy, which may have lasted for up to 50 million years. This could have removed eight Earth oceans’ worth of [[water]] and left 2000 bars of [[oxygen]] in its atmosphere, although if its initial [[hydrogen]] envelope had 0.1 Earth masses, no water would have been lost. Furthermore, the circulation of the planets orbit would take about 7 billion years, producing hundreds of terawatts of [[tidal heating]].<ref name=":0">{{Cite journal |last1=Barnes |first1=Rory |last2=Amaral |first2=Laura N. R. do |last3=Birky |first3=Jessica |last4=Carone |first4=Ludmila |last5=Driscoll |first5=Peter |last6=Livesey |first6=Joseph R. |last7=Graham |first7=David |last8=Becker |first8=Juliette |last9=Cui |first9=Kaiming |last10=Schlecker |first10=Martin |last11=Garcia |first11=Rodolfo |last12=Gialluca |first12=Megan |last13=Adams |first13=Arthur |last14=Ahmed |first14=MD Redyan |last15=Bonney |first15=Paul |date=2025-01-30 |title=History and Habitability of the LP 890-9 Planetary System |journal=The Planetary Science Journal |language=en |volume=6 |issue=1 |pages=25 |doi=10.3847/PSJ/ad94dc |doi-access=free |arxiv=2412.02743 |bibcode=2025PSJ.....6...25B |issn=2632-3338}}</ref>

The habitability of LP 890-9 c depends heavily on the initial [[Volatile (astrogeology)|volatile]] content and properties and the planet is unlikely to support [[life]].<ref name=":0" />

{{Orbitbox planet begin | name = LP 890-9 | table_ref = <ref name="Delrez2022"/> }} {{Orbitbox planet | exoplanet = b | mass_earth = <13.2 | radius_earth = {{val|1.320|0.053|0.027}} | semimajor = {{val|0.01875|0.00010}} | period = {{val|2.7299025|0.0000034|0.0000040}} | eccentricity = | inclination = {{val|89.67|0.22|0.33}} }} {{Orbitbox planet | exoplanet = c | mass_earth = <25.3 | radius_earth = {{val|1.367|0.055|0.039}} | semimajor = {{val|0.03984|0.00022}} | period = {{val|8.457463|0.000024}} | eccentricity = | inclination = {{val|89.287|0.026|0.047}} }} {{Orbitbox end}}

== See also == * [[Proxima Centauri]] - Closest [[star]] to the [[Sun]], a [[red dwarf]] that hosts terrestrial planets with one inside the habitable zone * [[Teegarden's Star]] - A nearby red dwarf in the constellation of [[Aries (constellation)|Aries]] with two known terrestrial planets in the habitable zone * [[TRAPPIST-1]] - An ultra-cool red dwarf in the constellation of [[Aquarius (constellation)|Aquarius]] * [[Wolf 359]] - A planet-hosting nearby ultra-cool red dwarf in the [[Leo (constellation)|Leo]] constellation

==Notes== {{reflist|group="note"|refs=

<ref name="absmag" group="note">The [[absolute magnitude]] <var>M<sub>V</sub></var> of the star can be calculated from its apparent magnitude <var>m<sub>V</sub></var> and distance <var>d</var> using the following equation: <math>\scriptstyle M_V = m_V - 5\log_{10} \left(\frac{d}{10\mathrm{\ parsecs}}\right)</math></ref>

}}

== References == <references> <ref name="SIMBAD">{{cite simbad |title=LP 890-9 |access-date=7 September 2022}}</ref>

<ref name="Delrez2022">{{cite journal |last1=Delrez |first1=L. |last2=Murray |first2=C. A. |display-authors=etal |date=September 2022 |title=Two temperate super-Earths transiting a nearby late-type M dwarf |journal=[[Astronomy & Astrophysics]] |volume=667 |issue= |pages=A59 |doi=10.1051/0004-6361/202244041 |arxiv=2209.02831 |s2cid=252110654 |bibcode=2022A&A...667A..59D}}</ref>

<ref name="Kaltenegger2022">{{cite journal |last1=Kaltenegger |first1=L. |last2=Payne |first2=R. C. |display-authors=etal |date=September 2023 |title=Hot Earth or Young Venus? A nearby transiting rocky planet mystery |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=524 |issue=1 |pages=L10–L14 |doi=10.1093/mnrasl/slad064 |doi-access=free |arxiv=2209.03105 |bibcode=2023MNRAS.524L..10K}}</ref>

<ref name="ULiège">{{cite web |url=https://www.news.uliege.be/cms/c_16795199/en/speculoos-discovers-a-potentially-habitable-super-earth |title=SPECULOOS discovers a potentially habitable super-Earth |last= |first= |date=7 September 2022 |website= |publisher=[[University of Liège]] |access-date=7 September 2022}}</ref> </references>

[[Category:Eridanus (constellation)]] [[Category:M-type main-sequence stars]] [[Category:Planetary systems with two confirmed planets]] [[Category:TESS Objects of Interest|4306]]