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| constell= [[Eridanus (constellation)|Eridanus]]
| constell= [[Eridanus (constellation)|Eridanus]]
| component1= LTT 1445 A
| component1= LTT 1445 A
| ra1= {{RA|03|01|51.39}}<ref name="Winters et al" />
| ra1= {{RA|03|01|51.39367}}<ref name="GaiaDR3"/>
| dec1= {{DEC|-16|35|36.1}}<ref name="Winters et al" />
| dec1= {{DEC|-16|35|36.0312}}<ref name="GaiaDR3"/>
| appmag_v1= 11.22 ± 0.02<ref name="Winters et al" />
| appmag_v1= {{val|11.22|0.02}}<ref name="Winters et al" />
| component2= LTT 1445 BC
| component2= LTT 1445 BC
| ra2= {{RA|03|01|51.04}}<ref name="Winters et al" />
| ra2= {{RA|03|01|51.04}}<ref name="Winters et al" />
| dec2= {{DEC|–16|35|31.1}}<ref name="Winters et al" />
| dec2= {{DEC|-16|35|31.1}}<ref name="Winters et al" />
| appmag_v2= 11.37±0.03<ref name="Winters et al" />
| appmag_v2= {{val|11.37|0.03}}<ref name="Winters et al" />
}}
}}
{{Starbox character
{{Starbox character
| class= M2.5+M3.0+M<ref>{{Cite journal |last1=Henry |first1=Todd J. |last2=Jao |first2=Wei-Chun
| class= M2.5+M3.0+M<ref name=henry2018/><ref name="Winters et al" />
|last3=Winters |first3=Jennifer G. |last4=Dieterich |first4=Sergio B.
|last5=Finch |first5=Charlie T. |last6=Ianna |first6=Philip A.
|last7=Riedel |first7=Adric R. |last8=Silverstein |first8=Michele L.
|last9=Subasavage |first9=John P. |last10=Vrijmoet |first10=Eliot Halley
|date=June 2018|title=The Solar Neighborhood XLIV: RECONS Discoveries within 10 parsecs |journal=The Astronomical Journal |language=en |volume=155 |issue=6 |pages=265 |doi=10.3847/1538-3881/aac262 |issn=0004-6256 |arxiv=1804.07377 |bibcode=2018AJ....155..265H |s2cid=53983430 }}</ref><ref name="Winters et al" />
}}
}}
{{Starbox astrometry
{{Starbox astrometry
| component1= LTT 1445 A
| component1 = LTT 1445 A
| radial_v=
| radial_v = {{val|-5.74|0.33}}<ref name="GaiaDR3"/>
| prop_mo_ra = −369.972
| prop_mo_ra= -369.196 ± 0.140<ref name="Gaia">{{Cite journal |last=Gaia Collaboration |date=2018-08-01 |title=Gaia Data Release 2 - Summary of the contents and survey properties |journal=Astronomy & Astrophysics |language=en |volume=616 |pages=A1 |arxiv=1804.09365 |doi=10.1051/0004-6361/201833051 |bibcode=2018A&A...616A...1G |s2cid=49211658 |issn=0004-6361 }}</ref>
| prop_mo_dec= -268.510 ± 0.147<ref name="Gaia" />
| prop_mo_dec = −267.931
| pm_footnote = <ref name="GaiaDR3"/>
| parallax= 145.6922
| p_error= 0.0244
| parallax = 145.6922
| p_error = 0.0244
| parallax_footnote= <ref name="GaiaEDR3">{{Cite Gaia EDR3|5153091836072107136}}</ref>
| parallax_footnote = <ref name="GaiaDR3"/>
}}
}}
{{Starbox orbit
{{Starbox orbit
Line 40: Line 36:
| primary = LTT 1445 B
| primary = LTT 1445 B
| name = LTT 1445 C
| name = LTT 1445 C
| period = 36.2 ± 5.3
| period = {{val|36.2|5.3}}
| axis = 1.159 ± 0.076
| axis = {{val|1.159|0.076}}
| axis_unitless =
| axis_unitless =
| eccentricity = 0.50 ± 0.11
| eccentricity = {{val|0.50|0.11}}
| inclination = 89.64 ± 0.13
| inclination = {{val|89.64|0.13}}
| node = 137.63 ± 0.19
| node = {{val|137.63|0.19}}
| periastron = 2019.2 ± 1.7
| periastron = {{val|2019.2|1.7}}
| periarg = 209 ± 13
| periarg = {{val|209|13}}
| k1 =
| k1 =
| k2 =
| k2 =
}}
}}
{{Starbox detail
{{Starbox detail
| component1 = A
| source= <!--[source url]-->
| mass= {{nowrap|A: 0.256 ± 0.014<ref name="Winters et al" />}}&nbsp;{{Solar mass}}<br/>{{nowrap|B: 0.215 ± 0.014<ref name="Winters et al" />}}&nbsp;{{Solar mass}}<br/>{{nowrap|C: 0.161 ± 0.014<ref name="Winters et al" />}}
| mass = {{val|0.257|0.014|u=Solar mass}}<ref name="Pass2023"/>
| radius= {{nowrap|A: {{val|0.276|0.024|0.019}}<ref name="Winters et al" />}}&nbsp;{{Solar radius}}<br/>{{nowrap|B: 0.236 ± 0.027<ref name="Winters et al" />}}&nbsp;{{Solar radius}}<br/>{{nowrap|C: 0.197 ± 0.027<ref name="Winters et al" />}}
| radius = {{val|0.271|0.019|0.010|u=Solar radius}}<ref name="Pass2023"/>
| luminosity_bolometric= A:&nbsp;0.00805 ± 0.00035<ref name="Winters et al" />
| luminosity_bolometric = {{val|0.00805|0.00035}}<ref name="Winters et al" />
| temperature= A:&nbsp;3337 ± 150<ref name="Winters et al" />
| temperature = {{val|fmt=commas|3337|150}}<ref name="Winters et al" />
| metal_fe= A:&nbsp;-0.34 ± 0.08<ref name="Winters et al" />
| metal_fe = {{val|-0.34|0.08}}<ref name="Winters et al" />
| gravity= A:&nbsp;{{val|4.967|0.061|0.075}}<ref name="Winters et al" />
| gravity = {{val|4.967|0.061|0.075}}<ref name="Winters et al" />
| age_gyr=
| rotation =
| age_gyr =
| component2 = B
| mass2 = {{val|0.215|0.014}}<ref name="Winters et al" />
| radius2 = {{val|0.236|0.027}}<ref name="Winters et al" />
| luminosity_bolometric2 =
| temperature2 =
| metal_fe2 =
| gravity2 =
| rotation2 =
| age_gyr2 =
}}
{{Starbox detail|no_heading=y
| component1 = C
| mass = {{val|0.161|0.014}}<ref name="Winters et al" />
| radius = {{val|0.197|0.027}}<ref name="Winters et al" />
| luminosity_bolometric =
| temperature =
| metal_fe =
| gravity =
| rotation = {{val|1.4|ul=d}}<ref name="Pass2023"/>
| age_gyr =
}}
}}
{{Starbox catalog
{{Starbox catalog
| names= [[Bonner Durchmusterung|BD]]-17&nbsp;588, [[Hipparcos#Published catalogues|HIP]]&nbsp;14101, [[Washington Double Star Catalog|WDS]]&nbsp;J03019-1633A,BC, [[IRAS]]&nbsp;02595-1647, [[2MASS]]&nbsp;J03015142-1635356, 2MASS&nbsp;J03015107-1635306, TIC&nbsp;98796344, [[Transiting Exoplanet Survey Satellite|TOI]]&nbsp;455, [[Gliese Catalogue of Nearby Stars|GJ]]&nbsp;3192, GJ&nbsp;3193
| names= [[Bonner Durchmusterung|BD]]−17&nbsp;588, [[Hipparcos#Published catalogues|HIP]]&nbsp;14101, [[Washington Double Star Catalog|WDS]]&nbsp;J03019-1633A,BC, [[IRAS]]&nbsp;02595-1647, [[2MASS]]&nbsp;J03015142-1635356, 2MASS&nbsp;J03015107-1635306, TIC&nbsp;98796344, [[Transiting Exoplanet Survey Satellite|TOI]]-455, [[Gliese Catalogue of Nearby Stars|GJ]]&nbsp;3192, GJ&nbsp;3193
}}
}}
{{Starbox reference
{{Starbox reference
Line 70: Line 87:
{{Starbox end}}
{{Starbox end}}


'''LTT 1445''' is a [[Star system|triple]] [[M dwarf|M-dwarf]] system about 22 [[light-year]]s distant<ref name="nasa">{{Cite web |url=https://exoplanets.nasa.gov/news/1598/discovery-alert-rocky-planet-swelters-under-three-red-suns/ |title=Discovery Alert: Rocky Planet Swelters Under Three Red Suns |last=Brennan |first=Pat |website=Exoplanet Exploration: Planets Beyond our Solar System |access-date=2020-02-13 }}</ref> in the constellation [[Eridanus (constellation)|Eridanus]]. The primary LTT&nbsp;1445&nbsp;A hosts two [[exoplanet]]s- one discovered in 2019 that [[Transiting exoplanet|transits]] the star every 5.36 days, and another found in 2021 that transits the star every 3.12 days, close to a 12:7 [[orbital resonance|resonance]]. As of August 2019 it is the second closest transiting exoplanet system discovered, with the closest being [[HD 219134]] bc.<ref name="nasa" />
'''LTT 1445''' is a [[Star system|triple]] [[M dwarf|M-dwarf]] system {{convert|22.4|ly|pc|lk=on|abbr=off}} distant<ref name="GaiaDR3"/> in the constellation [[Eridanus (constellation)|Eridanus]]. The primary LTT&nbsp;1445&nbsp;A hosts two [[exoplanet]]s—one discovered in 2019 that [[Transiting exoplanet|transits]] the star every 5.36 days, and another found in 2021 that transits the star every 3.12 days, close to a 12:7 [[orbital resonance|resonance]]. As of October 2022 it is the second closest transiting exoplanet system discovered, with the closest being [[HD 219134 b]][[HD 219134 c|c]].<ref name="Lavie2022"/>


== Stellar system ==
== Stellar system ==
All three stars in the system are M-dwarfs, with masses between 0.16 {{Solar mass|link=true}} and 0.26 {{Solar mass}}. LTT&nbsp;1445&nbsp;A and LTT&nbsp;1445&nbsp;BC are separated by about 34 [[astronomical unit]]s and orbit each other with a period of about 250 years. The BC pair orbit each other about every 36 years in an [[Orbital eccentricity|eccentric orbit]] (e= ~0.5). The alignment of the three stars and the edge-on orbit of the BC pair suggests [[Coplanarity|co-planarity]] of the system. The existence of a transiting planet [[LTT 1445Ab]] suggests that the entire system is co-planar, with orbits in one plane.<ref name="Winters et al">{{Cite journal
All three stars in the system are M-dwarfs, with masses between 0.16 {{Solar mass|link=true}} and 0.26 {{Solar mass}}. LTT&nbsp;1445&nbsp;A and LTT&nbsp;1445&nbsp;BC are separated by about 34 [[astronomical unit]]s and orbit each other with a period of about 250 years. The BC pair orbit each other about every 36 years in an [[Orbital eccentricity|eccentric orbit]] (e= ~0.5). The alignment of the three stars and the edge-on orbit of the BC pair suggests [[Coplanarity|co-planarity]] of the system. The existence of transiting planets suggests that the entire system is co-planar, with orbits in one plane.<ref name="Winters et al"/>
|last1=Winters |first1=Jennifer G. |last2=Medina |first2=Amber A. |last3=Irwin |first3=Jonathan M. |last4=Charbonneau |first4=David |last5=Astudillo-Defru |first5=Nicola |last6=Horch |first6=Elliott P. |last7=Eastman |first7=Jason D. |last8=Vrijmoet |first8=Eliot Halley |last9=Henry |first9=Todd J. |last10=Diamond-Lowe |first10=Hannah |last11=Winston |first11=Elaine
|display-authors=1
|date=October 2019
|url=https://iopscience.iop.org/article/10.3847/1538-3881/ab364d/pdf
|title=Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc
|journal=The Astronomical Journal |language=en |volume=158 |issue=4 |page=152 |doi=10.3847/1538-3881/ab364d |arxiv=1906.10147 |bibcode=2019AJ....158..152W |issn=0004-6256 |hdl=2144/39814 |s2cid=195584444 |hdl-access=free }}</ref>


The TESS light curve showed [[stellar flare]]s and rotational modulation due to [[starspot]]s, likely on either the B or C component.<ref name="Winters et al" /><ref>{{Cite journal
The TESS light curve showed [[stellar flare]]s and rotational modulation due to [[starspot]]s, likely on either the B or C component.<ref name="Winters et al" /><ref name=howard2019/>

== Planetary system ==
=== LTT 1445 Ab ===
LTT 1445 Ab is an [[exoplanet]] located approximately 22 light years away from [[Earth]]. Astrophysicists of the [[Harvard–Smithsonian Center for Astrophysics|Harvard Center for Astrophysics]] discovered it in June 2019 with data from the [[Transiting Exoplanet Survey Satellite]].<ref name="nasa" /><ref name="Winters et al" /> The team obtained follow-up observations, including [[High Accuracy Radial Velocity Planet Searcher|HARPS]] [[Doppler spectroscopy|radial velocity]] measurements to constrain the mass of the planet.

LTT 1445 Ab takes 5 days to orbit its star, which in turn orbits two sibling stars, making a total of three stars in the system.<ref name="nasa"/><ref name=bartels2019/><ref name="Winters et al"/>

In July 2021, the mass of the planet was measured as {{val|2.87|0.25}} Earth masses, confirming an Earth-like composition.<ref name="Winters2021" />

In 2022, a planetary transmission spectrum showed no evidence for an atmosphere, although an atmosphere with high altitude hazes cannot be ruled out yet.<ref name=diamondlowe2023/> LTT 1445 Ab likely has a rocky composition, and because it orbits close to the M-dwarf, it has an [[equilibrium temperature]] of {{val|431|23|ul=K}} ({{convert|431|K|C F|disp=out}}).<ref name="Pass2023"/>

=== LTT 1445 Ac ===
A second planet, LTT 1445 Ac, was also found in 2021 on a 3.12 day orbital period, with a mass of {{val|1.54|0.20|0.19}} Earth masses. Although it transits the star too, its smaller size made it difficult to detect before the radial velocity measurements, and still makes it difficult to estimate its exact size. The planets orbit near a 12:7 [[orbital resonance]] with one another - Ac orbiting 11.988 times for every 7 orbits Ab makes - oscillating one full orbit away from a 'perfect' resonance every 104 years.<ref name="Winters2021"/> The planet's existence was independently confirmed in 2022.<ref name="Lavie2022"/>

In 2023, observations with the [[Hubble Space Telescope]] allowed a more precise determination of the planet's size, supporting a rocky composition for both planets. Its equilibrium temperature is {{val|516|28|ul=K}} ({{convert|516|K|C F|disp=out}}).<ref name="Pass2023"/>

=== LTT 1445 Ad ===
A third planetary candidate on a 24.3-day orbit, LTT 1445 Ad, was found in 2022. This is a possibly rocky [[super-Earth]] orbiting within the [[habitable zone]].<ref name="Lavie2022"/>
{{OrbitboxPlanet begin
|name = LTT 1445 A
|table_ref = <ref name="Lavie2022"/><ref name="Pass2023"/>
}}
{{OrbitboxPlanet
|exoplanet = c
|mass_earth = {{val|1.37|0.19}}
|period = 3.1238994
|semimajor = {{val|0.02659|0.00047|0.00049}}
|radius_earth = {{val|1.07|0.10|0.07}}
|eccentricity = <0.223<ref name="Winters2021"/>
|inclination = {{val|87.46|0.13|0.21}}
}}
{{OrbitboxPlanet
|exoplanet = b
|mass_earth = {{val|2.73|0.25|0.23}}
|period = 5.3587635
|semimajor = {{val|0.03810|0.00067|0.00070}}
|radius_earth = {{val|1.34|0.11|0.06}}
|eccentricity = <0.110<ref name="Winters2021"/>
|inclination = {{val|89.53|0.33|0.40}}
}}
{{OrbitboxPlanet
|exoplanet = d
|mass_earth = {{val|2.72|0.75|p=≥}}
|period = {{val|24.30|0.03|0.08}}
|semimajor = {{val|0.09|0.02}}
|radius_earth =
|eccentricity =
|inclination =
}}
{{Orbitbox end}}

==See also==
* [[List of star systems within 20–25 light-years]]
* [[List of nearest exoplanets]]
* [[EZ Aquarii]] nearby M-dwarf triple
* [[GJ 1245]] nearby M-dwarf triple<ref name="Winters et al" />
* [[Gliese 667 Cc]]

==References==
{{Reflist|refs=

<ref name="GaiaDR3">{{Cite Gaia DR3|5153091836072107136}}</ref>

<ref name=diamondlowe2023>{{cite journal |last1=Diamond-Lowe |first1=Hannah |title=Ground-based Optical Transmission Spectroscopy of the Nearby Terrestrial Exoplanet LTT 1445Ab |journal=The Astronomical Journal |volume=165 |issue=4 |page=169 |year=2023 |arxiv=2210.11809 |doi=10.3847/1538-3881/acbf39 |last2=Mendonca |first2=Joao M. |last3=Charbonneau |first3=David |last4=Buchhave |first4=Lars A. |doi-access=free |bibcode=2023AJ....165..169D }}</ref>

<ref name=henry2018>{{Cite journal |last1=Henry |first1=Todd J. |last2=Jao |first2=Wei-Chun
|last3=Winters |first3=Jennifer G. |last4=Dieterich |first4=Sergio B.
|last5=Finch |first5=Charlie T. |last6=Ianna |first6=Philip A.
|last7=Riedel |first7=Adric R. |last8=Silverstein |first8=Michele L.
|last9=Subasavage |first9=John P. |last10=Vrijmoet |first10=Eliot Halley
|date=June 2018|title=The Solar Neighborhood XLIV: RECONS Discoveries within 10 parsecs |journal=The Astronomical Journal |language=en |volume=155 |issue=6 |pages=265 |doi=10.3847/1538-3881/aac262 |issn=0004-6256 |arxiv=1804.07377 |bibcode=2018AJ....155..265H |s2cid=53983430 |doi-access=free }}</ref>

<ref name=bartels2019>{{cite web |date=26 July 2019 |last1=Bartels |first1=Meghan |title=This Newfound Alien Planet Has 3 Suns |url=https://www.space.com/exoplanet-has-three-red-dwarf-suns.html |access-date=24 February 2021 |website=Space.com |language=en |archive-date=13 February 2021 |archive-url=https://web.archive.org/web/20210213082229/https://www.space.com/exoplanet-has-three-red-dwarf-suns.html |url-status=live }}</ref>

<ref name="nasa">{{Cite web |url=https://exoplanets.nasa.gov/news/1598/discovery-alert-rocky-planet-swelters-under-three-red-suns/ |title=Discovery Alert: Rocky Planet Swelters Under Three Red Suns |last=Brennan |first=Pat |website=Exoplanet Exploration: Planets Beyond our Solar System |access-date=2020-02-13 |archive-date=2023-05-23 |archive-url=https://web.archive.org/web/20230523100649/https://exoplanets.nasa.gov/news/1598/discovery-alert-rocky-planet-swelters-under-three-red-suns/ |url-status=live }}</ref>

<ref name=howard2019>{{Cite journal
|last1=Howard |first1=Ward S. |last2=Corbett |first2=Hank |last3=Law |first3=Nicholas M. |last4=Ratzloff
|last1=Howard |first1=Ward S. |last2=Corbett |first2=Hank |last3=Law |first3=Nicholas M. |last4=Ratzloff
|first4=Jeffrey K. |last5=Glazier |first5=Amy |last6=Fors |first6=Octavi |last7=del Ser |first7=Daniel
|first4=Jeffrey K. |last5=Glazier |first5=Amy |last6=Fors |first6=Octavi |last7=del Ser |first7=Daniel
|last8=Haislip |first8=Joshua
|last8=Haislip |first8=Joshua
|display-authors=1
|display-authors=1
|date=August 2019 |title=EvryFlare. I. Long-term Evryscope Monitoring of Flares from the Cool Stars across Half the Southern Sky |journal=Astrophysical Journal |language=en |volume=881 |issue=1 |pages=9 |doi=10.3847/1538-4357/ab2767 |issn=0004-637X |arxiv=1904.10421 |bibcode=2019ApJ...881....9H |s2cid=128361715 |doi-access=free }}</ref>
|url=https://iopscience.iop.org/article/10.3847/1538-4357/ab2767/pdf
|date=August 2019 |title=EvryFlare. I. Long-term Evryscope Monitoring of Flares from the Cool Stars across Half the Southern Sky |journal=Astrophysical Journal |language=en |volume=881 |issue=1 |pages=9 |doi=10.3847/1538-4357/ab2767 |issn=0004-637X |arxiv=1904.10421 |bibcode=2019ApJ...881....9H |s2cid=128361715 }}</ref>


<ref name="Winters et al">{{Cite journal
== Planetary system ==
|last1=Winters |first1=Jennifer G. |last2=Medina |first2=Amber A. |last3=Irwin |first3=Jonathan M. |last4=Charbonneau |first4=David |last5=Astudillo-Defru |first5=Nicola |last6=Horch |first6=Elliott P. |last7=Eastman |first7=Jason D. |last8=Vrijmoet |first8=Eliot Halley |last9=Henry |first9=Todd J. |last10=Diamond-Lowe |first10=Hannah |last11=Winston |first11=Elaine
[[LTT 1445Ab]] was discovered in June 2019<ref>{{citation |title=Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc |date=22 August 2019
|display-authors=1
|doi=10.3847/1538-3881/ab364d
|date=October 2019
|arxiv=1906.10147
|title=Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc
|last1=Winters |first1=Jennifer G. |last2=Medina |first2=Amber A.
|journal=The Astronomical Journal |language=en |volume=158 |issue=4 |page=152 |doi=10.3847/1538-3881/ab364d |arxiv=1906.10147 |bibcode=2019AJ....158..152W |issn=0004-6256 |hdl=2144/39814 |s2cid=195584444 |hdl-access=free |doi-access=free }}</ref>
|last3=Irwin |first3=Jonathan M. |last4=Charbonneau |first4=David
|last5=Astudillo-Defru |first5=Nicola |last6=Horch |first6=Elliott P.
|last7=Eastman |first7=Jason D. |last8=Vrijmoet |first8=Eliot Halley
|last9=Henry |first9=Todd J. |last10=Diamond-Lowe |first10=Hannah
|last11=Winston |first11=Elaine |last12=Barclay |first12=Thomas
|last13=Bonfils |first13=Xavier |last14=Ricker |first14=George R.
|last15=Vanderspek |first15=Roland |last16=Latham |first16=David W.
|last17=Seager |first17=Sara |last18=Winn |first18=Joshua N.
|last19=Jenkins |first19=Jon M. |last20=Udry |first20=Stéphane
|last21=Twicken |first21=Joseph D. |last22=Teske |first22=Johanna K.
|last23=Tenenbaum |first23=Peter |last24=Pepe |first24=Francesco
|last25=Murgas |first25=Felipe |last26=Muirhead |first26=Philip S.
|last27=Mink |first27=Jessica |last28=Lovis |first28=Christophe
|last29=Levine |first29=Alan M. |last30=Lépine |first30=Sébastien
|display-authors=1
|journal=The Astronomical Journal |volume=158 |issue=4 |page=152
|url=https://iopscience.iop.org/article/10.3847/1538-3881/ab364d/pdf
|access-date=9 July 2022
|bibcode=2019AJ....158..152W |s2cid=195584444 }}</ref> with data from the [[Transiting Exoplanet Survey Satellite]] by astrophysicists of the [[Harvard–Smithsonian Center for Astrophysics|Harvard Center for Astrophysics]].<ref name="nasa" /> The team obtained follow-up observations, including [[High Accuracy Radial Velocity Planet Searcher|HARPS]] [[Doppler spectroscopy|radial velocity]] measurements to constrain the mass of the planet. The planet orbits only one host star in a stable orbit. The planet likely has a rocky composition and because it orbits close to the M-dwarf, it has an [[equilibrium temperature]] of {{val|433|28|27}} [[Kelvin]] (160&nbsp;°C; 320&nbsp;°F). In July 2021, the mass of the planet was measured as {{val|2.87|0.25}} Earth masses, confirming an earthlike composition.<ref name="Winters2021" />


<ref name="Winters2021">{{cite journal|last1=Winters |first1=Jennifer G. |last2=Cloutier |first2=Ryan
A second planet, LTT 1445Ac, was also found on a 3.12 day orbital period, with a mass of {{val|1.54|0.20|0.19}} Earth masses. Although it transits the star too, its smaller size made it difficult to detect before the radial velocity measurements, and still makes it difficult to estimate its exact size. The planets orbit near a 12:7 [[orbital resonance]] with one another - Ac orbiting 11.988 times for every 7 orbits Ab makes - oscillating one full orbit away from a 'perfect' resonance every 104 years.<ref name="Winters2021">{{cite journal|last1=Winters |first1=Jennifer G. |last2=Cloutier |first2=Ryan
|last3=Medina |first3=Amber A. |last4=Irwin |first4=Jonathan M.
|last3=Medina |first3=Amber A. |last4=Irwin |first4=Jonathan M.
|last5=Charbonneau |first5=David |last6=Astudillo-Defru |first6=Nicola
|last5=Charbonneau |first5=David |last6=Astudillo-Defru |first6=Nicola
Line 160: Line 230:
|volume=163 |issue=4 |page=168
|volume=163 |issue=4 |page=168
|doi=10.3847/1538-3881/ac50a9
|doi=10.3847/1538-3881/ac50a9
|arxiv=2107.14737 |s2cid=236635391 |bibcode=2022AJ....163..168W |doi-access=free }}</ref>
|url=https://iopscience.iop.org/article/10.3847/1538-3881/ac50a9/pdf
|access-date=9 July 2022
|eprint=2107.14737 }}</ref> The planet existence was confirmed in 2022, alond with a 3rd planetary candidate on the 24.3 days orbit.<ref>{{citation|arxiv=2210.09713|year=2022|title=Planetary system around LTT 1445A unveiled by ESPRESSO:Multiple planets in a triple M-dwarf system}}</ref>.


<ref name="Lavie2022">{{cite journal|arxiv=2210.09713|year=2023|title=Planetary system around LTT 1445A unveiled by ESPRESSO:Multiple planets in a triple M-dwarf system|last1=Lavie |first1=B. |last2=Bouchy |first2=F. |last3=Lovis |first3=C. |last4=Zapatero Osorio |first4=M. |last5=Deline |first5=A. |last6=Barros |first6=S. |last7=Figueira |first7=P. |last8=Sozzetti |first8=A. |last9=Gonzalez Hernandez |first9=J. I. |last10=Lillo-Box |first10=J. |last11=Rodrigues |first11=J. |last12=Mehner |first12=A. |last13=Damasso |first13=M. |last14=Adibekyan |first14=V. |last15=Alibert |first15=Y. |last16=Allende Prieto |first16=C. |last17=Cristiani |first17=S. |last18=DOdorico |first18=V. |last19=Di Marcantonio |first19=P. |last20=Ehrenreich |first20=D. |last21=Genova Santos |first21=R. |last22=Lo Curto |first22=G. |last23=Martins |first23=C. J. A. P. |last24=Micela |first24=G. |last25=Molaro |first25=P. |last26=Nunes |first26=N. |last27=Palle |first27=E. |last28=Pepe |first28=F. |last29=Poretti |first29=E. |last30=Rebolo |first30=R. |journal=Astronomy and Astrophysics |volume=673 |pages=A69 |doi=10.1051/0004-6361/202143007 |display-authors=1 |bibcode=2023A&A...673A..69L|s2cid=252967989 }}</ref>
It is worth note that LTT 1445Ad receives approx. 76% of Earth's flux and is possibly rocky, spending full of its orbit near the middle of habitable zone. Also, there is a gap between its orbit and neighbouring LTT 1445Ab. If this gap is not empty, still undiscovered fourth planet in it will be a Venus-twin, prorably ever slighty smaller than Venus.

<ref name="Pass2023">{{cite journal |last1=Pass |first1=Emily K. |last2=Winters |first2=Jennifer G. |display-authors=etal |date=July 2023 |title=HST/WFC3 Light Curve Supports a Terrestrial Composition for the Closest Exoplanet to Transit an M Dwarf |journal=[[The Astronomical Journal]] |volume= 166|issue= 4|page=171 |doi= 10.3847/1538-3881/acf561|arxiv=2307.02970 |doi-access=free |bibcode=2023AJ....166..171P }}</ref>


{{OrbitboxPlanet begin
|name=LTT 1445A
|table_ref=<ref name="Winters et al" /><ref name="Winters2021" />
}}
{{OrbitboxPlanet
|exoplanet=[[LTT 1445Ac|c]]
|mass_earth= {{val|1.54|0.20|0.19}}
|period= 3.12390
|semimajor= {{val|0.02656|0.00047|0.00049}}
|radius_earth= >{{val|1.147|0.055|0.054}}
|eccentricity= <0.223
|inclination= {{val|87.43|0.18|0.29}}
}}
{{OrbitboxPlanet
|exoplanet=[[LTT 1445Ab|b]]
|mass_earth= {{val|2.66|0.26|0.25}}
|period= 5.35877
|semimajor= {{val|0.03805|0.00068|0.00070}}
|radius_earth= {{val|1.33|0.067|0.060}}
|eccentricity= <0.110
|inclination= {{val|89.68|0.22|0.29}}
}}
}}
{{OrbitboxPlanet
|exoplanet=[[LTT 1445Ad|d]]
|mass_earth= {{val|2.41|0.20|0.19}}
|period= 24.30388
|semimajor= {{val|0.01043|0.00117|0.0011}}
|radius_earth= >{{val|1.29 (predicted)}}
|eccentricity= low
|inclination= {{val|87.43|0.18|0.29}}
}}
{{Orbitbox end}}

==See also==
* [[List of star systems within 20–25 light-years]]
* [[List of nearest exoplanets]]
* [[EZ Aquarii]] nearby M-dwarf triple
* [[GJ 1245]] nearby M-dwarf triple<ref name="Winters et al" />
* [[Gliese 667 Cc]]

==References==
{{Reflist}}


{{Stars of Eridanus}}
{{Stars of Eridanus}}
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[[Category:M-type main-sequence stars]]
[[Category:M-type main-sequence stars]]
[[Category:TESS Objects of Interest|455]]
[[Category:TESS Objects of Interest|455]]
[[Category:Planetary systems with one confirmed planet]]
[[Category:Planetary systems with two confirmed planets]]
[[Category:Multi-star planetary systems|3]]
[[Category:Multi-star planetary systems|3]]
[[Category:Eridanus (constellation)]]
[[Category:Eridanus (constellation)]]

Latest revision as of 23:44, 3 January 2024

LTT 1445 A,BC

Hubble ACS/HRC image showing all three stars. Upper left is LTT 1445 A and in the lower right part of the image is the LTT 1445 BC pair.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Eridanus
LTT 1445 A
Right ascension 03h 01m 51.39367s[1]
Declination −16° 35′ 36.0312″[1]
Apparent magnitude (V) 11.22±0.02[2]
LTT 1445 BC
Right ascension 03h 01m 51.04s[2]
Declination −16° 35′ 31.1″[2]
Apparent magnitude (V) 11.37±0.03[2]
Characteristics
Spectral type M2.5+M3.0+M[3][2]
Astrometry
LTT 1445 A
Radial velocity (Rv)−5.74±0.33[1] km/s
Proper motion (μ) RA: −369.972 mas/yr[1]
Dec.: −267.931 mas/yr[1]
Parallax (π)145.6922 ± 0.0244 mas[1]
Distance22.387 ± 0.004 ly
(6.864 ± 0.001 pc)
Orbit[2]
PrimaryLTT 1445 B
CompanionLTT 1445 C
Period (P)36.2±5.3 yr
Semi-major axis (a)1.159±0.076″
Eccentricity (e)0.50±0.11
Inclination (i)89.64±0.13°
Longitude of the node (Ω)137.63±0.19°
Periastron epoch (T)2019.2±1.7
Argument of periastron (ω)
(secondary)		209±13°
Details
A
Mass0.257±0.014 M☉[4] M☉
Radius0.271+0.019
−0.010 R☉[4] R☉
Luminosity (bolometric)0.00805±0.00035[2] L☉
Surface gravity (log g)4.967+0.061
−0.075[2] cgs
Temperature3,337±150[2] K
Metallicity [Fe/H]−0.34±0.08[2] dex
B
Mass0.215±0.014[2] M☉
Radius0.236±0.027[2] R☉
C
Mass0.161±0.014[2] M☉
Radius0.197±0.027[2] R☉
Rotation1.4 d[4]
Other designations
BD−17 588, HIP 14101, WDS J03019-1633A,BC, IRAS 02595-1647, 2MASS J03015142-1635356, 2MASS J03015107-1635306, TIC 98796344, TOI-455, GJ 3192, GJ 3193
Database references
SIMBADA,BC

LTT 1445 is a triple M-dwarf system 22.4 light-years (6.9 parsecs) distant[1] in the constellation Eridanus. The primary LTT 1445 A hosts two exoplanets—one discovered in 2019 that transits the star every 5.36 days, and another found in 2021 that transits the star every 3.12 days, close to a 12:7 resonance. As of October 2022 it is the second closest transiting exoplanet system discovered, with the closest being HD 219134 bc.[5]

Stellar system[edit]

All three stars in the system are M-dwarfs, with masses between 0.16 M☉ and 0.26 M☉. LTT 1445 A and LTT 1445 BC are separated by about 34 astronomical units and orbit each other with a period of about 250 years. The BC pair orbit each other about every 36 years in an eccentric orbit (e= ~0.5). The alignment of the three stars and the edge-on orbit of the BC pair suggests co-planarity of the system. The existence of transiting planets suggests that the entire system is co-planar, with orbits in one plane.[2]

The TESS light curve showed stellar flares and rotational modulation due to starspots, likely on either the B or C component.[2][6]

Planetary system[edit]

LTT 1445 Ab[edit]

LTT 1445 Ab is an exoplanet located approximately 22 light years away from Earth. Astrophysicists of the Harvard Center for Astrophysics discovered it in June 2019 with data from the Transiting Exoplanet Survey Satellite.[7][2] The team obtained follow-up observations, including HARPS radial velocity measurements to constrain the mass of the planet.

LTT 1445 Ab takes 5 days to orbit its star, which in turn orbits two sibling stars, making a total of three stars in the system.[7][8][2]

In July 2021, the mass of the planet was measured as 2.87±0.25 Earth masses, confirming an Earth-like composition.[9]

In 2022, a planetary transmission spectrum showed no evidence for an atmosphere, although an atmosphere with high altitude hazes cannot be ruled out yet.[10] LTT 1445 Ab likely has a rocky composition, and because it orbits close to the M-dwarf, it has an equilibrium temperature of 431±23 K (158 °C; 316 °F).[4]

LTT 1445 Ac[edit]

A second planet, LTT 1445 Ac, was also found in 2021 on a 3.12 day orbital period, with a mass of 1.54+0.20
−0.19 Earth masses. Although it transits the star too, its smaller size made it difficult to detect before the radial velocity measurements, and still makes it difficult to estimate its exact size. The planets orbit near a 12:7 orbital resonance with one another - Ac orbiting 11.988 times for every 7 orbits Ab makes - oscillating one full orbit away from a 'perfect' resonance every 104 years.[9] The planet's existence was independently confirmed in 2022.[5]

In 2023, observations with the Hubble Space Telescope allowed a more precise determination of the planet's size, supporting a rocky composition for both planets. Its equilibrium temperature is 516±28 K (243 °C; 469 °F).[4]

LTT 1445 Ad[edit]

A third planetary candidate on a 24.3-day orbit, LTT 1445 Ad, was found in 2022. This is a possibly rocky super-Earth orbiting within the habitable zone.[5]

The LTT 1445 A planetary system[5][4]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
c 1.37±0.19 M🜨 0.02659+0.00047
−0.00049 		3.1238994 <0.223[9] 87.46+0.13
−0.21° 		1.07+0.10
−0.07 R🜨
b 2.73+0.25
−0.23 M🜨 		0.03810+0.00067
−0.00070 		5.3587635 <0.110[9] 89.53+0.33
−0.40° 		1.34+0.11
−0.06 R🜨
d ≥2.72±0.75 M🜨 0.09±0.02 24.30+0.03
−0.08 		— — —

See also[edit]

References[edit]

  1. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d e f g h i j k l m n o p q r s Winters, Jennifer G.; et al. (October 2019). "Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc". The Astronomical Journal. 158 (4): 152. arXiv:1906.10147. Bibcode:2019AJ....158..152W. doi:10.3847/1538-3881/ab364d. hdl:2144/39814. ISSN 0004-6256. S2CID 195584444.
  3. ^ Henry, Todd J.; Jao, Wei-Chun; Winters, Jennifer G.; Dieterich, Sergio B.; Finch, Charlie T.; Ianna, Philip A.; Riedel, Adric R.; Silverstein, Michele L.; Subasavage, John P.; Vrijmoet, Eliot Halley (June 2018). "The Solar Neighborhood XLIV: RECONS Discoveries within 10 parsecs". The Astronomical Journal. 155 (6): 265. arXiv:1804.07377. Bibcode:2018AJ....155..265H. doi:10.3847/1538-3881/aac262. ISSN 0004-6256. S2CID 53983430.
  4. ^ a b c d e f Pass, Emily K.; Winters, Jennifer G.; et al. (July 2023). "HST/WFC3 Light Curve Supports a Terrestrial Composition for the Closest Exoplanet to Transit an M Dwarf". The Astronomical Journal. 166 (4): 171. arXiv:2307.02970. Bibcode:2023AJ....166..171P. doi:10.3847/1538-3881/acf561.
  5. ^ a b c d Lavie, B.; et al. (2023). "Planetary system around LTT 1445A unveiled by ESPRESSO:Multiple planets in a triple M-dwarf system". Astronomy and Astrophysics. 673: A69. arXiv:2210.09713. Bibcode:2023A&A...673A..69L. doi:10.1051/0004-6361/202143007. S2CID 252967989.
  6. ^ Howard, Ward S.; et al. (August 2019). "EvryFlare. I. Long-term Evryscope Monitoring of Flares from the Cool Stars across Half the Southern Sky". Astrophysical Journal. 881 (1): 9. arXiv:1904.10421. Bibcode:2019ApJ...881....9H. doi:10.3847/1538-4357/ab2767. ISSN 0004-637X. S2CID 128361715.
  7. ^ a b Brennan, Pat. "Discovery Alert: Rocky Planet Swelters Under Three Red Suns". Exoplanet Exploration: Planets Beyond our Solar System. Archived from the original on 2023-05-23. Retrieved 2020-02-13.
  8. ^ Bartels, Meghan (26 July 2019). "This Newfound Alien Planet Has 3 Suns". Space.com. Archived from the original on 13 February 2021. Retrieved 24 February 2021.
  9. ^ a b c d Winters, Jennifer G.; et al. (30 July 2021). "A Second Planet Transiting LTT~1445A and a Determination of the Masses of Both Worlds". The Astronomical Journal. 163 (4): 168. arXiv:2107.14737. Bibcode:2022AJ....163..168W. doi:10.3847/1538-3881/ac50a9. S2CID 236635391.
  10. ^ Diamond-Lowe, Hannah; Mendonca, Joao M.; Charbonneau, David; Buchhave, Lars A. (2023). "Ground-based Optical Transmission Spectroscopy of the Nearby Terrestrial Exoplanet LTT 1445Ab". The Astronomical Journal. 165 (4): 169. arXiv:2210.11809. Bibcode:2023AJ....165..169D. doi:10.3847/1538-3881/acbf39.
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