HD 63433 d
{{Short description|Exoplanet orbiting G-type star HD 63433}}
{{Infobox planet
| discoverer = Capistrant, Soares-Furtado et al. (THYME)
| period = {{val|4.20975|0.000012|0.000023|ul=d}}
| mean_radius = {{val|1.073|0.046|0.044|ul=Earth radius}}
| name = HD 63433 d
| image = Hd63433d.jpg
| image_scale = 1.25
| caption = Artist's impression of
HD 63433 d as compared with Earth
| discovered = 10 January 2024
| discovery_method = Transit{{Cite web |last=Martin |first=Pierre-Yves |date=2024 |title=Planet HD 63433 b |url=https://exoplanet.eu/catalog/hd_63433_b--7399/ |access-date=2024-01-12 |website=exoplanet.eu |language=en}}
| alt_names = TOI-1726 d, BD+27 1490 d, HIP 38228 d, V377 Geminorum d
| semimajor = {{val|0.0503|0.0025|0.0027|ul=AU}}
| eccentricity = {{val|0.16|0.36|0.12}}
| inclination = {{val|88.73|0.85|1.06|ul=deg}}
| star = HD 63433
| single_temperature = {{val|1040|40|u=K}} {{nowrap|(767 ± 40°C)}} (mean),{{Efn|1=Assuming an albedo of 0.3|name=0.3 Albedo}}, {{convert|1530|K|C}} (daytime){{Efn|1=Assuming an albedo of 0, similar to the measured albedo of TRAPPIST-1b.|name=0 Albedo}}
}}
HD 63433 d (TOI-1726 d) is a confirmed exoplanet orbiting HD 63433, a Sun-like star located 73 light-years away in the constellation Gemini.{{Cite web |last=de Lazaro |first=Enrico |date=January 15, 2023 |title=Earth-Sized Exoplanet Found Orbiting HD 63433 |url=https://www.sci.news/astronomy/earth-sized-exoplanet-hd-63433d-12608.html |access-date=January 16, 2023 |website=SciNews}} Its radius is measured at around {{Earth radius|1.1|link=y}}, which makes it similar to the Earth in size.{{Cite journal |last1=Capistrant |first1=Benjamin K. |last2=Soares-Furtado |first2=Melinda |last3=Vanderburg |first3=Andrew |last4=Jankowski |first4=Alyssa |last5=Mann |first5=Andrew W. |last6=Ross |first6=Gabrielle |last7=Srdoc |first7=Gregor |last8=Hinkel |first8=Natalie R. |last9=Becker |first9=Juliette |last10=Magliano |first10=Christian |last11=Limbach |first11=Mary Anne |last12=Stephan |first12=Alexander P. |last13=Nine |first13=Andrew C. |last14=Tofflemire |first14=Benjamin M. |last15=Kraus |first15=Adam L. |date=January 10, 2024 |title=TESS Hunt for Young and Maturing Exoplanets (THYME). XI. An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400 Myr Ursa Major Moving Group |journal=The Astronomical Journal |language=en |volume=167 |issue=2 |pages=54 |doi=10.3847/1538-3881/ad1039 |issn=1538-3881 |doi-access=free|arxiv=2401.04785 |bibcode=2024AJ....167...54C }} It was the third (and most recent) exoplanet to be discovered in orbit around this star; the other two, HD 63433 b and c, were discovered in 2020. Orbiting its star at a distance of {{Convert|0.0503|AU|km|lk=in}}, HD 63433 d is the innermost planet orbiting HD 63433, and completes an orbit around it just every 4 days. Due to the proximity of its star, the planet is scorching hot, having a temperature estimated at 1260 °C at daytime.{{Cite web |last=Robert |first=Lea |date=January 12, 2024 |title=Newfound Earth-size exoplanet has a scorching-hot lava side |url=https://www.space.com/newfound-exoplanet-hd-63433d-lava-hemisphere-tess |url-status=live |archive-url=https://web.archive.org/web/20240112164309/https://www.space.com/newfound-exoplanet-hd-63433d-lava-hemisphere-tess |archive-date=January 12, 2024 |access-date=January 12, 2024 |website=Space}} The proximity of its star also causes it to be tidally locked.
Physical characteristics
Having a radius of {{val|1.073|ul=Earth radius}} ({{val|6845|fmt=commas|u=km|p=~}}), it is roughly the size of Earth, but its mass is still unknown. HD 63433 d is the innermost planet in the system, orbiting its star at a distance of {{convert|0.0503|AU|km|lk=in}} and completing one orbital period around it every 4 days and 5 hours. The proximity of its star causes HD 63433 d to be scorching hot, having a daytime temperature estimated at {{Convert|1260|C|F}}, {{Efn|name=0 Albedo}} which is similar to other lava planets such as Kepler-10b and CoRoT-7b,{{Cite web |last=Gohd |first=Chelsea |date=January 10, 2024 |title=Discovery Alert: Earth-sized Planet Has a 'Lava Hemisphere' |url=https://science.nasa.gov/universe/exoplanets/discovery-alert-earth-sized-planet-has-a-lava-hemisphere/ |url-status=live |archive-url=https://web.archive.org/web/20240115231238/https://science.nasa.gov/universe/exoplanets/discovery-alert-earth-sized-planet-has-a-lava-hemisphere/ |archive-date=January 15, 2024 |access-date=January 15, 2024 |website=science.nasa.gov}} and hot enough to melt all minerals on its surface.{{Cite web |last=Thomson |first=Jess |date=January 12, 2024 |title=Hellish World With 2,294 F 'Lava Hemisphere' Discovered by NASA |url=https://www.newsweek.com/exoplanet-lava-hemisphere-discovered-nasa-1860175 |access-date=January 23, 2024 |website=Newsweek}} In addition, the planet is tidally locked, meaning that one side of the planet always faces its star, while the other side always faces away from it, and it possibly lacks a substantial atmosphere. Tidal locking also happens with the Moon, which has one side always facing Earth.
It is believed that its dayside, always facing its star due to tidal locking, is completely molten and dominated by lava,{{Cite web |last=Gough |first=Evan |date=January 12, 2024 |title=Half of this Exoplanet is Covered in Lava |url=https://www.universetoday.com/165216/half-of-this-exoplanet-is-covered-in-lava/ |website=Universe Today}} in addition to possibly having volcanic activity.{{Cite web |last=Staff |first=Buzz |title=NASA Telescope Discovers Half-Lava Exoplanet Of Same Size As Earth |url=https://www.news18.com/amp/viral/nasa-telescope-discovers-half-lava-exo-planet-of-same-size-as-earth-8742680.html |access-date=January 16, 2024 |website=News18|date=16 January 2024 }}{{Cite web |last=Whitwam |first=Ryan |date=January 15, 2024 |title=Astronomers Discover Earth-Sized Planet That's Half Lava |url=https://www.extremetech.com/science/astronomers-discover-earth-sized-planet-thats-half-lava |access-date=January 17, 2024 |website=ExtremeTech}} Meanwhile, the night side of the planet could be as cold as Pluto, having glaciers of frozen nitrogen, depending on its composition.
With an age estimated at 414 million years, it is the smallest known exoplanet less than 500 million years old, and the nearest Earth-sized planet this young.
Importance
The small size, young age and the proximity of its star make HD 63433 an interesting planet for further exploration. According to the HD 63433 d discovery team, this planet and another young terrestrial planets are critical test beds to constrain the current theories of planetary formation and evolution.{{Cite web |last=Maruccia |first=Alfonso |date=January 16, 2024 |title=NASA discovers new exoplanet with a "lava hemisphere" in a distant star system |url=https://www.techspot.com/community/topics/nasa-discovers-new-exoplanet-with-a-lava-hemisphere-in-a-distant-star-system.283966/ |access-date=January 17, 2024 |website=Techspot}} The study of HD 63433 d could produce valuable information about the formation and evolution of Earth-sized planets.
Discovery
The planet was discovered by a team of scientists led by Benjamin Capistrant and Melinda Soares-Furtado after analyzing a transit observation made by the Transiting Exoplanet Survey Satellite (TESS). The team took the data and removed the transit signals of the other planets, thus revealing an additional transit signal that reappeared every 4.2 days. Later investigations validated that this transit signal was from a third planet around the star HD 63433.{{Cite web |date=January 17, 2024 |title='Extra hot and young' Earth-sized exoplanet with a 'lava hemisphere' discovered |url=https://www.wionews.com/science/scientists-discover-youngest-earth-sized-exoplanet-having-lava-hemisphere-679301/amp |archive-date= |website=wionews.com}} The discovery was announced on January 10, 2023, in The Astrophysical Journal.{{Cite web |last=Szondy |first=David |date=January 11, 2024 |title=Tidally locked exo-Earth has a lava ocean hemisphere |url=https://newatlas.com/space/tidally-locked-exoplanet-lava-ocean-hemisphere/ |url-status=live |archive-url=https://web.archive.org/web/20240116132806/https://newatlas.com/space/tidally-locked-exoplanet-lava-ocean-hemisphere/ |archive-date=January 16, 2024 |access-date=January 14, 2024 |website=New Atlas}}
The discovery of HD 63433 d is part of a project called TESS Hunt for Young and Maturing Exoplanets (THYME), which seeks to discover young transiting exoplanets in moving groups, stellar associations and open clusters.
Host star
{{Main article|HD 63433}}
The host star of HD 63433 d is HD 63433, a G-type main-sequence star which is located 73 light-years away in the Gemini constellation. Having a radius 91% similar to that of the Sun, and a mass 99% similar, HD 63433 has properties very similar to those of the Sun, being classified as a solar analog.{{Cite journal |last1=Mann |first1=Andrew W. |last2=Johnson |first2=Marshall C. |last3=Vanderburg |first3=Andrew |last4=Kraus |first4=Adam L. |last5=Rizzuto |first5=Aaron C. |last6=Wood |first6=Mackenna L. |last7=Bush |first7=Jonathan L. |last8=Rockcliffe |first8=Keighley |last9=Newton |first9=Elisabeth R. |last10=Latham |first10=David W. |last11=Mamajek |first11=Eric E. |last12=Zhou |first12=George |last13=Quinn |first13=Samuel N. |last14=Thao |first14=Pa Chia |last15=Benatti |first15=Serena |date=2020-10-01 |title=TESS Hunt for Young and Maturing Exoplanets (THYME). III. A Two-planet System in the 400 Myr Ursa Major Group |journal=The Astronomical Journal |volume=160 |issue=4 |pages=179 |doi=10.3847/1538-3881/abae64 |doi-access=free |arxiv=2005.00047 |bibcode=2020AJ....160..179M |issn=0004-6256}} With an apparent magnitude of 6.9, the star cannot be been with the naked eye, but can be with a small telescope{{Cite web |title=⬤ Exoplanet HD 63433 d |url=https://www.stellarcatalog.com/exoplanet.php?planetID=101438 |access-date=2024-01-16 |website=Stellar Catalog |language=en}} or binoculars.{{Cite web |last=Siegel-Itzkovich |first=Judy |date=January 14, 2024 |title=Earth-sized exoplanet discovered in 'our solar backyard' by international team |url=https://m.jpost.com/science/article-782104 |url-status=live |archive-url=https://web.archive.org/web/20240120145418/https://www.jpost.com/science/article-782104 |archive-date=January 20, 2024 |access-date=January 20, 2024 |website=The Jerusalem Post}} HD 63433 is part of the Ursa Major moving group, which makes its age estimated at 414 million years. Other stars located in this group include Alioth and Mizar, located in the Big Dipper.
HD 63433 also hosts two other exoplanets: HD 63433 b and c, two mini-Neptune planets discovered in 2020 by Mann et al.
See also
Notes
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