LHS 3844 b

{{Short description|Exoplanet in the constellation Indus}}

{{Infobox planet

| extrasolarplanet = yes

| name = LHS 3844 b / Kua'kua

| image = PIA23130-Exoplanet-LHS3844b-ArtistConcept-20190819.jpg

| caption = Artist’s illustration of LHS 3844 b

| apsis = astron

| discovery_ref =

| discoverer = Vanderspek et al.

| discovered = September 2018

| discovery_method = Transit

| alt_names = Kua'kua, TOI-136.01, TIC 410153553 b

| semimajor = {{val|0.00622|0.00017}} AU

| period = {{val|0.46292913|0.00000190}} d

| inclination = {{val|88.50|0.51}}

| star = LHS 3844

| mean_radius = {{val|1.303|0.022}} {{Earth radius|link=y}}

| albedo = <0.2

| single_temperature = {{convert|1040|K|C F}} (day side)

}}

LHS 3844 b, formally named Kua'kua{{Pronunciation needed|date=November 2024}}, is an exoplanet orbiting the red dwarf LHS 3844, about {{convert|48.5|ly|pc|lk=on|abbr=off}} away in the constellation Indus, discovered using the Transiting Exoplanet Survey Satellite. It orbits its parent star once every 11 hours, and its radius is 1.32 times that of Earth. It has a low albedo, indicating that its surface may resemble that of the Moon or Mercury. LHS 3844 b probably does not have an atmosphere as almost no heat goes to its night side, and it has a dayside temperature of {{convert|1040|K|C F}}.{{Cite web|url=http://www.nasa.gov/feature/jpl/nasa-gets-a-rare-look-at-a-rocky-exoplanets-surface|title=NASA Gets a Rare Look at a Rocky Exoplanet's Surface|last=Greicius|first=Tony|date=2019-08-19|website=NASA|access-date=2019-08-25}} The presence of cloudy atmosphere with cloud tops above pressure level of 0.1 bar cannot be excluded though.{{citation|arxiv=2008.05444|title=Optical Transmission Spectroscopy of the Terrestrial Exoplanet LHS 3844b from 13 Ground-based Transit Observations|year=2020|doi=10.3847/1538-3881/abaf4f|last1=Diamond-Lowe|first1=Hannah|last2=Charbonneau|first2=David|last3=Malik|first3=Matej|last4=Kempton|first4=Eliza M.-R.|last5=Beletsky|first5=Yuri|journal=The Astronomical Journal|volume=160|issue=4|page=188|bibcode=2020AJ....160..188D|s2cid=221103928 |doi-access=free }}

In order to explain the lack of atmosphere, it has been proposed that the planet was formed interior to the star system's snow-line, because if it formed beyond the snow-line it would have carried volatiles, on the surface and in a thick atmosphere, that according to models on atmospheric loss should have been enough to sustain an atmosphere to the present. The planet probably also formed with a volatile-poor outgassing mantle, in a stagnant lid regime, because if the mantle was similar in constitution to Earth's, with plate tectonics, then it should still have a thick atmosphere, unless the red dwarf consistently flared at an uncharacteristically extreme rate not yet considered in atmospheric loss models. An alternative explanation for the lack of atmosphere could be through a large impact event, one with enough momentum to strip the planet of its atmosphere and a large portion of its mantle. In order to explain the non-replenishment of volatiles via comets back onto the planet, it is also proposed that perhaps there is an outer gas giant in the star system.

It is thought that LHS 3844 b is tidally locked due to its surface being 'relatively cool', although this hypothesis could possibly be complicated by the fact that the research into the temperature of the planet assumed that there was no atmosphere, a point which is not definitively confirmed.{{Cite journal |last=Howlett |first=Joseph |date=2024-03-28 |title=This super-Earth is the first planet confirmed to have a permanent dark side |url=https://www.nature.com/articles/d41586-024-00414-z |journal=Nature |language=en |doi=10.1038/d41586-024-00414-z}}