TOI-561

Last updated
TOI-561
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Sextans
Right ascension 09h 52m 44.1851s [1]
Declination +06° 12′ 58.921″ [1]
Apparent magnitude  (V)10.25 [2]
Characteristics
Evolutionary stage main sequence
Spectral type G9V [2]
Astrometry
Proper motion (μ)RA: 124.612  mas/yr [1]
Dec.: −61.279  mas/yr [1]
Parallax (π)11.8342 ± 0.0208  mas [1]
Distance 275.6 ± 0.5  ly
(84.5 ± 0.1  pc)
Details
Mass 0.785±0.018 [2]   M☉
Radius 0.849±0.007 [2]   R☉
Luminosity 0.522±0.017 [3]   L☉
Surface gravity (log g)4.50±0.12 [2]   cgs
Temperature 5,372±70 [2]   K
Metallicity [Fe/H]−0.40±0.05 [2]   dex
Rotational velocity (v sin i)<2 [2]  km/s
Age 10±3 [3]   Gyr
Other designations
2MASS J09524454+0612589, TYC 243-1528-1, GSC 00243-01528, Gaia DR2 3850421005290172416
Database references
SIMBAD data

TOI-561 is an old, metal-poor, Sun-like star, known to have multiple small planets. [3] [2] [4] [5] It is an orange dwarf, estimated to be 10.5 billion years old, and about 79% the mass and 85% the radius of Sol, Earth's sun. [6] [5] It is located in the constellation Sextans, near the border with Leo.

Contents

In January 2021, a team led by Lauren Weiss of the University of Hawaii at Manoa announced that, using data from NASA's Transiting Exoplanet Survey Satellite, they had found a Super-Earth in a very close orbit, as well as two outer Sub-Neptunes. [7] [8] [6] [3] The innermost planet, TOI-561 b, orbits in under one Earth day. [2] [3] Another team led by Gaia Lacedelli of the University of Padua independently announced the discovery in a paper published in December 2020. [2] However, the two papers disagree on the structure of the system. While the innermost two planets were confirmed from data by both papers, Weiss proposes only a single third planet in a 16.3-day orbit, while Lacedelli argues that the system instead contains two further planets, in wider orbits of 25.6 and 77 days. [2]

Discovery and nomenclature

TOI-561 is also designated 2MASS J09524454+0612589 in the 2MASS catalog and TIC 377064495 in the TESS Input Catalog. When its planets were first identified, it was renamed TOI-561, with TOI standing for "TESS Object of Interest". [9]

The planetary system was independently confirmed and characterized by Lacedelli et al. 2020 and Weiss et al. 2021. Lacedelli et al. found evidence for four exoplanets: the Ultra-Short-Period (USP) Super-Earth TOI-561 b, and three Sub-Neptunes designated TOI-561 c, d, and e. The two planets TOI-561 d and TOI-561 e were originally listed as a single planet with a period of 16 days on ExoFOP, but Lacedelli could not detect a planet in that orbit using radial velocity data from HARPS, and instead interpreted it as two separate transits coming from planets correlating with periods of 25.6 and 77.2 days found by HARPS. [2]

In January 2021, Lauren Weiss and her team's study on TOI-561 was published. Unlike Lacedelli, they kept the 16-day signal and designated it TOI-561 d; [3] it is referred to as TOI-561 f on NASA's Exoplanet Archive to avoid confusion with the TOI-561 d from Lacedelli's paper. [9]

Characteristics

TOI-561 is a yellow or orange star approximately 80% the size of the Sun. According to Lacedelli, it is 85% the radius and 79% the mass of the Sun, with a temperature of 5455 K. [2] Weiss found the star to be 83.2% the radius and 80.5% the mass of the Sun, with a temperature of 5326 K and a luminosity just over half that of the Sun. [3] Both teams found that TOI-561 has an extremely low abundance of metals, or any element heavier than hydrogen or helium, and is very old; Weiss calculates an age of roughly 10 billion years. It is also a part of the Galactic Thick-Disk and is the first of those stars to have confirmed transiting exoplanets. [3]

Planetary system

Depending on the study, TOI-561 has either 3 (Weiss) or 4 (Lacedelli) planets. The discrepancy comes from different interpretations of the two transit events associated with TOI-561 d in Weiss 2020. Only two transits were observed by TESS, and a third transit for a 16-day period would have occurred in the middle of a data gap. [3] Weiss attributes the two transits to that of a single Sub-Neptune sized planet. However, in the radial velocity analysis by Lacedelli 2020, the 16-day signal is not recovered, but there are two additional signals of 26 and 77 days that they attribute to one of the two transits each. [2] The follow-up study in 2022 has confirmed the architecture of four-planet system. Additional, fifth planet on the 473+36
−25 days orbit is suspected. [10] The orbital parameters were refined with additional observations from CHEOPS and TESS in 2024, further confirming four transiting planets and a fifth non-transiting candidate. [11]

The TOI-561 planetary system [11]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 2.02±0.23  M🜨 0.01064±0.000160.4465697±0.0000003087.0+2.0
−2.1 ° 		1.39±0.027  R🜨
c5.93±0.67  M🜨 0.0889±0.001310.778838±0.0000180.023+0.034
−0.017		89.61+0.27
−0.33 ° 		2.865±0.041  R🜨
d13.33±0.98  M🜨 0.1587±0.002425.71268±0.000120.111+0.050
−0.039		89.51+0.25
−0.14 ° 		2.615±0.059  R🜨
e12.4±1.4  M🜨 0.3300±0.005077.14400±0.000270.074+0.044
−0.039		89.864+0.095
−0.094 ° 		2.517±0.045  R🜨
f(candidate)19.1±2.7 M🜨 1.043±0.035433+20
−18		0.083+0.080
−0.058		——

TOI-561 b

TOI-561 b is an USP Super-Earth with a radius of roughly 1.4 Earths. It has an extremely short orbital period of under 11 hours, less than half of an Earth day, resulting in an equilibrium temperature of 2,480 ± 200 K (2,207 ± 200 °C; 4,004 ± 360 °F). [3] The planet is believed to be far too small and irradiated to hold onto its primordial Hydrogen and Helium envelope. However, the composition of the planet varies greatly between the two studies. Weiss 2020 found a mass of around 3.2 Earths and a density of 5.5 grams per cubic centimetre, around the same as Earth and implying a rocky but iron-poor composition. [3] Lacedelli 2020, on the other hand, found a mass of only 1.59 Earths and a density of 3.0 grams per cubic centimetre, abnormally low for a planet of its size and suggesting a composition made of 50% or more of water. Even their higher mass estimate of 1.83 Earths is still consistent with a water-world. With an insolation 5,100 times greater than Earth, TOI-561 b should have lost its gaseous layer and have little volatiles, so the authors believe if the planet has a significant amount of water, it has been evaporated into a puffy steam atmosphere that makes the planet seem larger, less dense, and more water-rich. If it is an extremely water-rich world, TOI-561 b would prove formation scenarios about Super-Earths forming beyond the "Snow Line" and migrating inwards. [2]

TOI-561 c

TOI-561 c is a Mini-Neptune orbiting every 10.7 days with an equilibrium temperature of 860 ± 70 K (586.9 ± 70.0 °C; 1,088.3 ± 126.0 °F). [3] With a radius of 2.9 Earths and a mass of 5.4 to 7.0 Earths, the planet has a Neptune-like density of 1.3 to 1.6 grams per cubic centimetre, implying that it is a small gas planet with a similar composition, albeit far hotter and closer to its star than our system's ice giants.

TOI-561 d/e/f

Two additional transit events were observed by TESS. The original planet candidate from the SPOC pipeline included both transits with a period of 16 days. [9] [3] [2] Lacedelli et al. failed to find a significant radial velocity signal at that period, but found two others with periods of 25.6 and 77.2 days, and also noticed differences in the shape, duration, and depth of the two individual transits. They concluded that the 16-day signal was instead two separate single transit events from similarly sized but different planets, which corresponded with the additional signals found in their radial velocity analysis. They designated these planets TOI-561 d (25.6 days) and TOI-561 e (77.2 days). According to their analysis, both planets are slightly smaller than TOI-561 c at 2.5 and 2.7 Earths, but are both significantly more massive, at 12 and 16 times the mass of Earth. TOI-561 d and TOI-561 e are much denser at 4.1 and 4.6 grams per cubic centimetre, respectively. These are compatible with water-world compositions of >50% water by mass, or a thin H/He envelope on top of a water mantle and rocky core. [2] Weiss et al. interprets the two transits as a single planet, and also interprets an extremely faint radial velocity signal corresponding to about 3 Earth masses; [3] however, it is too imprecise to gain an accurate density estimate, and this scenario could be incorrect. To distinguish this from the previous reported TOI-561 e, the 16-day planet from Weiss et al. has been designated TOI-561 f on the Exoplanet Archive. [9]

Related Research Articles

<span class="mw-page-title-main">Super-Earth</span> Type of exoplanet

A Super-Earth or super-terran is a type of exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.

This page describes exoplanet orbital and physical parameters.

<span class="mw-page-title-main">CHEOPS</span> Optical space telescope (launched in 2019)

CHEOPS is a European space telescope. Its objective is to determine the size of known extrasolar planets, which will allow the estimation of their mass, density, composition and their formation. Launched on 18 December 2019, it is the first Small-class mission in ESA's Cosmic Vision science programme.

<span class="mw-page-title-main">Next-Generation Transit Survey</span> Ground-based robotic search for exoplanets

The Next-Generation Transit Survey (NGTS) is a ground-based robotic search for exoplanets. The facility is located at Paranal Observatory in the Atacama desert in northern Chile, about 2 km from ESO's Very Large Telescope and 0.5 km from the VISTA Survey Telescope. Science operations began in early 2015. The astronomical survey is managed by a consortium of seven European universities and other academic institutions from Chile, Germany, Switzerland, and the United Kingdom. Prototypes of the array were tested in 2009 and 2010 on La Palma, and from 2012 to 2014 at Geneva Observatory.

<span class="mw-page-title-main">LHS 1140</span> Star in the constellation Cetus

LHS 1140 is a red dwarf in the constellation of Cetus. Based on stellar parallax measurement, it is 48.8 light-years away from the Sun. 'LHS' refers to the Luyten Half-Second Catalogue of stars with proper motions exceeding half a second of arc annually. The star is over 5 billion years old and has only about 18% the mass of the Sun and 21% of its radius. LHS 1140's rotational period is 130 days. No flares have been observed.

<span class="mw-page-title-main">HD 21749</span> Star in the constellation Reticulum

HD 21749 is an orange main-sequence star in the constellation Reticulum. It has an apparent visual magnitude of 8.143, which means it is too dim to be seen with the naked eye. From parallax measurements by the Gaia spacecraft, it is located 53 ly (16 pc) from Earth.

<span class="mw-page-title-main">Proxima Centauri c</span> Exoplanet candidate orbiting Proxima Centauri

Proxima Centauri c is a controversial exoplanet candidate claimed to be orbiting the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. It is located approximately 4.2 light-years from Earth in the constellation of Centaurus, making it, Proxima b, and Proxima d the closest known exoplanets to the Solar System.

TOI-700 is a red dwarf 101.4 light-years away from Earth located in the Dorado constellation that hosts TOI-700 d, the first Earth-sized exoplanet in the habitable zone discovered by the Transiting Exoplanet Survey Satellite (TESS).

HD 260655 is a relatively bright and cool M0 V red dwarf star located 33 light-years away from the Solar System in the constellation of Gemini. HD 260655 has two confirmed rocky planets, named HD 260655 b and HD 260655 c, that were discovered in 2022. Both planets were detected by the TESS mission and confirmed independently with archival and new precise radial velocity data obtained with the HIRES observatory since 1998, and the CARMENES survey instruments since 2016.

<span class="mw-page-title-main">TOI-2180 b</span> Jovian-sized exoplanet orbiting TOI-2180

TOI-2180 b is a giant exoplanet orbiting the G-type star TOI-2180, also known as HD 238894. It was discovered with the help of the Transiting Exoplanet Survey Satellite and is currently the exoplanet with the longest orbital period TESS was able to uncover. TOI-2180 b orbits its host star every 260.16 days.

TOI-561 b is an USP Super-Earth with a radius of roughly 1.4 Earths. It has an extremely short orbital period of under 11 hours, less than half of an Earth day, resulting in an equilibrium temperature of 2,480 ± 200 K. The planet is believed to be far too small and irradiated to hold onto its primordial Hydrogen and Helium envelope. However, the composition of the planet varies greatly between the two studies. Weiss 2020 found a mass of around 3.2 Earths and a density of 5.5 grams per cubic centimetre, around the same as Earth and implying a rocky but iron-poor composition. Lacedelli 2020, on the other hand, found a mass of only 1.59 Earths and a density of 3.0 grams per cubic centimetre, abnormally low for a planet of its size and suggesting a composition made of 50% or more of water. Even their higher mass estimate of 1.83 Earths is consistent with a water world. With an insolation 5,100 times greater than Earth, TOI-561 b should have lost its gaseous layer and have little volatiles, so the authors believe if the planet has a significant amount of water, it has been evaporated into a puffy steam atmosphere that makes the planet seem larger, less dense, and more water-rich. If it is an extremely water-rich world, TOI-561 b would prove formation scenarios about Super-Earths forming beyond the "Snow Line" and migrating inwards.

GJ 3929 b is a confirmed exoplanet located 52 light-years away orbiting the red dwarf star GJ 3929. It is an Earth-sized planet, having a radius only 9% larger than that of Earth. It orbits its star at a distance of 0.0252 astronomical units (3,770,000 km), being located in the Venus zone of its star, and completes one orbit around it every 2 days and 15 hours. Because of the proximity of its star, and its low mass, GJ 3929 b is classified as a Venus-like planet, having an equilibrium temperature of around 300 °C and receiving planetary insolation 17 times more intense than Earth receives from the Sun.

<span class="mw-page-title-main">GJ 3929</span> Red dwarf star in the constellation Corona Borealis

GJ 3929, also known as Gliese 3929 and TOI-2013, is a red dwarf star located 51.6 light-years from Earth, in the constellation Corona Borealis. With an apparent magnitude of 12, it is not visible to the naked eye. In 2022, two exoplanets were detected orbiting the star.

HD 63433 c is a mini-Neptune exoplanet orbiting the Sun-like star HD 63433. It is the outermost planet in its planetary system, being located 0.1448 astronomical units (21,660,000 km) from its star, and completing one orbit every 21 days. Despite being the outermost planet in the system, it is still located close to its star, meaning that its temperature is hot, being estimated between 267 and 406 °C. HD 63433 c is about 2.7 times larger than Earth and 15.5 times more massive, but still smaller and less massive than Neptune. In 2022, a study showed that its atmosphere, made up of hydrogen, is being evaporated by the strong radiation from its star, causing it to slowly turn into a super-Earth planet.

References

  1. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Lacedelli, G.; et al. (2021). "An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561". Monthly Notices of the Royal Astronomical Society . 501 (3): 4148–4166. arXiv: 2009.02332 . Bibcode:2021MNRAS.501.4148L. doi: 10.1093/mnras/staa3728 . S2CID   221516470.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Weiss, Lauren M.; et al. (2020). "The TESS-Keck Survey II: Masses of Three Sub-Neptunes Transiting the Galactic Thick-Disk Star TOI-561". The Astronomical Journal. 161 (2) 56. arXiv: 2009.03071 . Bibcode: 2021AJ....161...56W . doi: 10.3847/1538-3881/abd409 . S2CID   229279232.
  4. ↑ Jean Schneider. "Planet TOI-561 b". Extrasolar Planets Encyclopaedia . Retrieved 2021-02-01.
  5. 1 2 Natali Anderson (2021-01-13). "Astronomers Discover 10-Billion-Year-Old Multiplanet System". Sci-news . Retrieved 2021-02-01. TOI-561 hosts at least three small transiting planets, named TOI-561b, c, and d, and is one of the oldest, most metal-poor planetary systems discovered yet in the Milky Way.
  6. 1 2 Michelle Starr (2021-01-14). "Astronomers Find an Astonishing 'Super-Earth' That's Nearly as Old as The Universe". ScienceAlert . Retrieved 2021-02-01. Around one of the galaxy's oldest stars, an orange dwarf named TOI-561 just 280 light-years away, astronomers have found three orbiting exoplanets - one of which is a rocky world 1.5 times the size of Earth, whipping around the star on a breakneck 10.5-hour orbit.
  7. ↑ Jules Bernstein (2021-01-11). "'Super Earth' discovered near one of our galaxy's oldest stars: Hot planet orbits its star twice during every Earth day". University of California Riverside . Retrieved 2021-02-01. A hot, rocky "super Earth," near one of the oldest stars in the galaxy has taken a team of planet-hunting scientists by surprise.
  8. ↑ Doris Lam (2021-01-18). "All About The Discovery Of TOI-561b, The 14-Billion-Year-Old 'Super-Earth' Scientists Recently Found". Tatler . Retrieved 2021-02-01.
  9. 1 2 3 4 "ExoFOP TIC 377064495" . Retrieved 2021-05-03.
  10. ↑ Lacedelli, G.; et al. (2022), "Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N, and TESS", Monthly Notices of the Royal Astronomical Society, 511 (3): 4551–4571, arXiv: 2201.07727 , doi: 10.1093/mnras/stac199
  11. 1 2 Piotto, G.; Zingales, T.; Borsato, L.; Egger, J. A.; Correia, A. C. M.; Simon, A. E.; Florén, H.-G.; Sousa, S. G.; Maxted, P. F. L.; Wilson, T. G.; Alibert, Y.; Adibekyan, V.; Bonfanti, A.; Luque, R.; Santos, N. C.; Hooton, M. J.; Fossati, L.; Serrano, L. M.; Smith, A. M. S.; Salmon, S.; Lacedelli, G.; Alonso, R.; Bárczy, T.; Barrado Navascues, D.; Barros, S. C. C.; Baumjohann, W.; Beck, T.; Benz, W.; Billot, N.; Brandeker, A.; Broeg, C.; Collier Cameron, A.; Csizmadia, Sz.; Cubillos, P. E.; Davies, M. B.; Deleuil, M.; Deline, A.; Demangeon, O. D. S.; Demory, B.-O.; Derekas, A.; Edwards, B.; Ehrenreich, D.; Erikson, A.; Fortier, A.; Fridlund, M.; Gandolfi, D.; Gazeas, K.; Gillon, M.; Güdel, M.; Günther, M. N.; Heitzmann, A.; Helling, Ch.; Isaak, K. G.; Kiss, L. L.; Korth, J.; Lam, K. W. F.; Laskar, J.; Lecavelier des Etangs, A.; Lendl, M.; Leonardi, P.; Magrin, D.; Mordasini, C.; Nascimbeni, V.; Olofsson, G.; Ottensamer, R.; Pagano, I.; Pallé, E.; Peter, G.; Pollacco, D.; Queloz, D.; Ragazzoni, R.; Rando, N.; Rauer, H.; Ribas, I.; Scandariato, G.; Ségransan, D.; Stalport, M.; Sulis, S.; Szabó, Gy. M.; Udry, S.; Ulmer-Moll, S.; Van Grootel, V.; Venturini, J.; Villaver, E.; Walton, N. A. (2024). "Architecture of TOI-561 planetary system". arXiv: 2410.18169 [astro-ph.EP].
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