TOI-1685 b

{{Short description|A super-Earth type exoplanet}}

'''TOI-1685 b''' is a terrestrial [[super-Earth]] that orbits around the [[red dwarf]] star [[TOI-1685]] which is located around 122.6 light years (37.6 [[Parsec|parsecs]]) from [[Earth]]. It is a hot and barren planet with a mass of about 3 Earths and a radius of 1.4 Earths. The planet orbits extremely close to its host star with an orbital period lasting only 0.69 days. This makes TOI-1685 b a [[Ultra-short period planet|ultra-short period]] (USP) planet.{{Cite journal |last=Burt |first=Jennifer A. |last2=Hooton |first2=Matthew J. |last3=Mamajek |first3=Eric E. |last4=Barragán |first4=Oscar |last5=Millholland |first5=Sarah C. |last6=Fairnington |first6=Tyler R. |last7=Fisher |first7=Chloe |last8=Halverson |first8=Samuel P. |last9=Huang |first9=Chelsea X. |last10=Brady |first10=Madison |last11=Seifahrt |first11=Andreas |last12=Gaidos |first12=Eric |last13=Luque |first13=Rafael |last14=Kasper |first14=David |last15=Bean |first15=Jacob L. |date=2024-08-01 |title=TOI-1685 b Is a Hot Rocky Super-Earth: Updates to the Stellar and Planet Parameters of a Popular JWST Cycle 2 Target |url=https://validate.perfdrive.com/fb803c746e9148689b3984a31fccd902/?ssa=a3373e70-ad1f-4d50-9db4-7965790df175&ssb=45256242791&ssc=https%3A%2F%2Fiopscience.iop.org%2Farticle%2F10.3847%2F2041-8213%2Fad5b52&ssi=d365751f-cnvj-4997-8898-55ab452aada0&ssk=botmanager_support@radware.com&ssm=39044746639661340101973174209033&ssn=00a11e64c79de8c774b656883c07afbf26a89e52dc0b-9107-4d76-b979f8&sso=0a9f4607-37ae5a2044f86d02a725d3bbacc8d8bcc9a9521233337c38&ssp=13937913441776830495177680493422636&ssq=63058150439154507405604391245464882698958&ssr=MjA4LjgwLjE1NS4xMTg=&sst=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36 Citoid/WMF (mailto:noc@wikimedia.org)&ssu=&ssv=&ssw=&ssx=eyJfX3V6bWYiOiI3ZjkwMDA5ZTUyZGMwYi05MTA3LTRkNzYtYjYwNy0zN2FlNWEyMDQ0ZjgxLTE3NzY4MDQzOTE5MTkwLTAwMzFmOGViNTExMDY1N2ZkYjExMCIsInJkIjoiaW9wLm9yZyIsInV6bXgiOiI3ZjkwMDAyNjI5YzkxNi1hMWQxLTQwNGUtYmMwMC1kOGRjNzk0ZTA4OTQxLTE3NzY4MDQzOTE5MTkwLWIzNTkxZTQwN2RlZjZjODIxMCJ9 |journal=The Astrophysical Journal Letters |volume=971 |issue=1 |pages=L12 |doi=10.3847/2041-8213/ad5b52 |issn=2041-8205}}

== Discovery ==
The planet was [[List of exoplanets discovered in 2021|discovered in the year 2021]] using the [[transit method]] by two discovery papers: (Bluhm et al. 2021) and (Hirano et al. 2021). While both papers included [[Photometry (astronomy)|photometric]] data from the [[Transiting Exoplanet Survey Satellite]] (TESS), the included a variety of additional data and methods of analysis. This led to significant disagreements between the characteristics of the host star and planet including their mass and radius. (Bluhm et al. 2021) reported this planet to have a mass of about 3.78 Earths and a radius of 1.70 Earths{{Cite journal |last=Bluhm |first=P. |last2=Pallé |first2=E. |last3=Molaverdikhani |first3=K. |last4=Kemmer |first4=J. |last5=Hatzes |first5=A. P. |last6=Kossakowski |first6=D. |last7=Stock |first7=S. |last8=Caballero |first8=J. A. |last9=Lillo-Box |first9=J. |last10=Béjar |first10=V. J. S. |last11=Soto |first11=M. G. |last12=Amado |first12=P. J. |last13=Brown |first13=P. |last14=Cadieux |first14=C. |last15=Cloutier |first15=R. |date=2021-06-01 |title=An ultra-short-period transiting super-Earth orbiting the M3 dwarf TOI-1685 |url=https://www.aanda.org/articles/aa/abs/2021/06/aa40688-21/aa40688-21.html |journal=Astronomy & Astrophysics |language=en |volume=650 |pages=A78 |doi=10.1051/0004-6361/202140688 |issn=0004-6361}} while (Hirano et al. 2021) reported this planet having a mass of about 3.43 Earths and a radius of 2.0 Earths.{{Cite journal |last=Hirano |first=Teruyuki |last2=Livingston |first2=John H. |last3=Fukui |first3=Akihiko |last4=Narita |first4=Norio |last5=Harakawa |first5=Hiroki |last6=Ishikawa |first6=Hiroyuki Tako |last7=Miyakawa |first7=Kohei |last8=Kimura |first8=Tadahiro |last9=Nakayama |first9=Akifumi |last10=Fujita |first10=Naho |last11=Hori |first11=Yasunori |last12=Stassun |first12=Keivan G. |last13=Bieryla |first13=Allyson |last14=Cadieux |first14=Charles |last15=Ciardi |first15=David R. |date=2021-09-23 |title=Two Bright M Dwarfs Hosting Ultra-Short-Period Super-Earths with Earth-like Compositions* |url=https://validate.perfdrive.com/fb803c746e9148689b3984a31fccd902/?ssa=acf80bcc-ba21-4065-992b-7f216aa8e11a&ssb=51470228760&ssc=https%3A%2F%2Fiopscience.iop.org%2Farticle%2F10.3847%2F1538-3881%2Fac0fdc&ssi=f569710a-cnvj-4382-ae57-d4a633e19ad8&ssk=botmanager_support@radware.com&ssm=17532412882799342104863196210171&ssn=4051ae22eab17e24d1af2a1646de1d644bef0ab434a8-7729-4761-a19dd7&sso=43308c6f-b38d52bb4febc9e5e3c85c77dbf65be16e5c832303389e29&ssp=08966429131776856513177680119158764&ssq=57954820470648044414104706583440988873391&ssr=MjA4LjgwLjE1NS4xMTg=&sst=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36 Citoid/WMF (mailto:noc@wikimedia.org)&ssu=&ssv=&ssw=&ssx=eyJfX3V6bWYiOiI3ZjkwMDAwYWI0MzRhOC03NzI5LTQ3NjEtYWM2Zi1iMzhkNTJiYjRmZWIxLTE3NzY4MDQ3MDY4NjIwLTAwMzQyNjZkODFiMzIwNzdiNmQxMCIsInV6bXgiOiI3ZjkwMDA0ODQxZjNlNy1kMWMxLTQzNWItYjAyOS1iNDkxZDdjMzk3N2MxLTE3NzY4MDQ3MDY4NjIwLTk1N2I3NzJiOWUyZDY4ZmYxMCIsInJkIjoiaW9wLm9yZyJ9 |journal=The Astronomical Journal |volume=162 |issue=4 |pages=161 |doi=10.3847/1538-3881/ac0fdc |issn=0004-6256}} The study (Burt et al. 2024) updates the characteristics of both the host star and the planet using updated [[Astronomical transit|transiting]] data and RV analysis.

== Phyaical characteristics ==
The planet was initially interpreted to have a mass between 3.43-3.78 Earths and a radius between 1.70-2.0 Earths. However it appears that TOI-1685 b is smaller with lower mass and higher densities than initially reported. The planet has a mass of 3.03 ±0.33 Earths and a radius of 1.468 ±0.050 Earths. It has a [[density]] of 5.3 ±0.8 g/cm -3 which is similar to the rough density of Earth which is 5.51 g/cm -3. The Earth-like density of this planet suggests that TOI-1685 b is likely a terrestrial planet. The [[Planetary equilibrium temperature|equilibrium temperature]] is high at 1062 ±27 Kelvin.

TOI-1685 b was initially thought to be either a hot and barren terrestrial planet or a [[Ocean world|water world]] composed of 50% [[water]] and 50% [[enstatite]] (MgSiO3). However its density and observations from the [[James Webb Space Telescope]] (JWST) during its second cycle reveals that TOI-1685 b is likely not a water world but more likely a hot barren world with negligible amounts of [[Volatile (astrogeology)|volatile]] materials.

=== Atmosphere ===
[[Hydrogen]]-dominated [[Atmosphere|atmospheres]] have been confidently ruled out and any hydrogen or [[helium]] gasses that would have formed with the planet appears to not exists anymore contributing little to its atmosphere. TOI-1685 b could have a [[secondary atmosphere]] that is made of purely of heavier gasses such as [[carbon dioxide]] (CO2), [[sulfur dioxide]] (SO2), water (H2O) or [[methane]] (CH4). Another scenario that could fit the data would be a mixed secondary atmosphere made up of [[carbon monoxide]] (CO), CO2 and SO2. A pure methane-dominated atmosphere appears to be unlikely and atmospheres composed purely of CO2 and water would require high-altitude clouds or a thin-cloud free atmosphere.{{Cite journal |last=Fisher |first=Chloe E |last2=Hooton |first2=Matthew J |last3=Gressier |first3=Amélie |last4=Zgraggen |first4=Merlin |last5=Tian |first5=Meng |last6=Heng |first6=Kevin |last7=Allen |first7=Natalie H |last8=Chatterjee |first8=Richard D |last9=Morris |first9=Brett M |last10=Borsato |first10=Nicholas W |last11=Espinoza |first11=Néstor |last12=Kitzmann |first12=Daniel |last13=Meier |first13=Tobias G |last14=Buchhave |first14=Lars A |last15=Burgasser |first15=Adam J |date=2026-01-05 |title=JWST NIRSpec finds no clear signs of an atmosphere on TOI-1685 b |url=https://academic.oup.com/mnras/article/doi/10.1093/mnras/staf2187/8378092 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=545 |issue=4 |doi=10.1093/mnras/staf2187 |issn=0035-8711}}

== Formation ==
The formation of ultra-short period planets in their current position has been deemed unlikely as the dust particles inside the [[protoplanetary disk]] sublimate at distances this close to the star. This suggest that TOI-1685 did not form in situ and instead [[Planetary migration|migrated]] to its current position, however the process on how it got to its current position is not known. The first scenario involves dynamical interactions with other planets in the system driving the orbit of TOI-1685 b from longer periods to shorter. However there is a lack of evidence for additional planets in the system. The second scenario is that ultra-short period planets like TOI-1685 b are the remnant cores of [[Hot Jupiter|hot Jupiters]] or [[Hot Saturn|hot Saturns]]. However evidence for this seems to be lacking as their is no abnormalities in the stars [[metallicity]].

== See also ==

# [[List of exoplanets discovered in 2021]]
# [[55 Cancri Ae|Janssen]]- an super-Earth with a thick atmosphere
# [[Kepler-78b]]- an Earth-sized lava world
# [[GJ 4256 b]]- an egg-shaped Earth-sized world that nearly reached its host stars [[roche limit]]

== References ==