Astronomy:Next-Generation Transit Survey

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Short description: Ground-based robotic search for exoplanets

[ ⚑ ] 24°36′57″S 70°23′28″W / 24.61583°S 70.39111°W / -24.61583; -70.39111

  • Top: NGTS facility with the VLT (left) and VISTA (right) in the background
  • Middle: the facility (rendered) and night observations
  • Bottom: The array of twelve 0.2-meter robotic telescopes

The Next-Generation Transit Survey (NGTS) is a ground-based robotic search for exoplanets.[1] 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.[2] The astronomical survey is managed by a consortium of seven European universities and other academic institutions from Chile, Germany, Switzerland, and the United Kingdom.[3] Prototypes of the array were tested in 2009 and 2010 on La Palma, and from 2012 to 2014 at Geneva Observatory.[3]

The aim of NGTS is to discover super-Earths and exo-Neptunes transiting relatively bright and nearby stars with an apparent magnitude of up to 13. The survey uses transit photometry, which precisely measures the dimming of a star to detect the presence of a planet when it crosses in front of it. NGTS consists of an array of twelve commercial 0.2-metre telescopes (f/2.8), each equipped with a red-sensitive CCD camera operating in the visible and near-infrared at 600–900 nm. The array covers an instantaneous field of view of 96 square degrees (8 deg2 per telescope) or around 0.23% of the entire sky.[4] NGTS builds heavily on experience with SuperWASP, using more sensitive detectors, refined software, and larger optics, though having a much smaller field of view.[5] Compared to the Kepler spacecraft with its original Kepler field of 115 square degrees, the sky area covered by NGTS will be sixteen times larger, because the survey intends to scan four different fields every year over a period of four years. As a result, the sky coverage will be comparable to that of Kepler's K2 phase.[4]

NGTS is suited to ground-based photometric follow-up of exoplanet candidates from space-based telescopes such as TESS, Gaia and PLATO.[1] In turn, larger instruments such as HARPS, ESPRESSO and VLT-SPHERE may follow-up on NGTS discoveries with a detailed characterization to measure the mass of a large number of targets using Doppler spectroscopy (wobble method) and make it possible to determine the exoplanet's density, and hence whether it is gaseous or rocky. This detailed characterization allows to fill the gap between Earth-sized planets and gas giants as other ground-based surveys can only detect Jupiter-sized exoplanets, and Kepler's Earth-sized planets are often too far away or orbit stars too dim to allow for the planet's mass determination. NGTS's wider field of view also enables it to detect a larger number of more-massive planets around brighter stars.[6][7]

Science mission

File:The Next-Generation Transit Survey (NGTS) at Paranal - Vid.ogg

Ground-based surveys for extrasolar planets such as WASP and the HATNet Project have discovered many large exoplanets, mainly Saturn- and Jupiter-sized gas giants. Space-based missions such as CoRoT and the Kepler survey have extended the results to smaller objects, including rocky super-Earth- and Neptune-sized exoplanets.[4] Orbiting space missions have a higher accuracy of stellar brightness measurement than is possible via ground-based measurements, but they have probed a relatively small region of sky. Unfortunately, most of the smaller candidates orbit stars that are too faint for confirmation by radial-velocity measurements. The masses of these smaller candidate planets are hence either unknown or poorly constrained, such that their bulk composition cannot be estimated.[4]

By focusing on super-Earth- to Neptune-sized targets orbiting cool, small, but bright stars of K and early-M spectral type, over an area considerably larger than that covered by space missions, NGTS is intended to provide prime targets for further scrutiny by telescopes such as the Very Large Telescope (VLT), European Extremely Large Telescope (E-ELT), and the James Webb Space Telescope (JWST). Such targets are more readily characterized in terms of their atmospheric composition, planetary structure, and evolution than smaller targets orbiting larger stars.[3]

In follow-up observations by larger telescopes, powerful means will be available to probe the atmospheric composition of exoplanets discovered by NGTS. For example, during secondary eclipse, when the star occults the planet, a comparison between the in-transit and out-of-transit flux allows computation of a difference spectrum representing the thermal emission of the planet.[8] Calculation of the transmission spectrum of the planet's atmosphere can be obtained by measuring the small spectral changes in the spectrum of the star that arise during the planet's transit. This technique requires an extremely high signal-to-noise ratio, and has thus far been successfully applied to only a few planets orbiting small, nearby, relatively bright stars, such as HD 189733 b and GJ 1214 b. NGTS is intended to greatly increase the number of planets that area analyzable using such techniques.[8] Simulations of expected NGTS performance reveal the potential of discovering approximately 231 Neptune- and 39 super-Earth-sized planets amenable to detailed spectrographic analysis by the VLT, compared to only 21 Neptune- and 1 super-Earth-sized planets from the Kepler data.[4]

Instrument

Development

The scientific goals of the NGTS require being able to detect transits with a precision of 1 mmag at 13th magnitude. Although at ground level this level of accuracy was routinely achievable in narrow-field observations of individual objects, it was unprecedented for a wide-field survey.[4] To achieve this goal, the designers of the NGTS instruments drew upon an extensive hardware and software heritage from the WASP project, in addition to developing many refinements in prototype systems operating on La Palma during 2009 and 2010, and at the Geneva Observatory from 2012 to 2014.[6]

Telescope array

NGTS employs an automated array of twelve 20-centimeter f/2.8 telescopes on independent equatorial mounts and operating at orange to near-infrared wavelengths (600–900 nm). It is located at the European Southern Observatory's Paranal Observatory in Chile, a location noted for low water-vapor and excellent photometric conditions.

Combined search

The NGTS telescope project cooperates closely with ESO's large telescopes. ESO facilities available for follow-up studies include the High Accuracy Radial Velocity Planet Searcher (HARPS) at La Silla Observatory; ESPRESSO for radial-velocity measurements at the VLT; SPHERE, an adaptive optics system and coronagraphic facility at the VLT that directly images extrasolar planets;[9] and a variety of other VLT and planned E-ELT instruments for atmospheric characterization.[4]

Partnership

Although located at Paranal Observatory, NGTS is not in fact operated by ESO, but by a consortium of seven academic institutions from Chile, Germany, Switzerland, and the United Kingdom:[3]

Results

  • On 31 October 2017, the discovery of NGTS-1b, a confirmed hot Jupiter-sized extrasolar planet orbiting NGTS-1, an M-dwarf star, about half the mass and radius of the Sun, every 2.65 days, was reported by the survey team.[10][11][12] Daniel Bayliss, of the University of Warwick, and lead author of the study describing the discovery of NGTS-1b, stated, "The discovery of NGTS-1b was a complete surprise to us—such massive planets were not thought to exist around such small stars – importantly, our challenge now is to find out how common these types of planets are in the Galaxy, and with the new Next-Generation Transit Survey facility we are well-placed to do just that."[12]
  • On 3 September 2018, the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34 day orbit. NGTS-4b has a mass 20.6 ± 3.0 M⊕ and radius 3.18 ± 0.26 R⊕, which places it well within the so-called "Neptunian desert". The mean density of the planet (3.45 ± 0.95 g cm−3) is consistent with a composition of 100% H2O or a rocky core with a volatile envelope.[13]

Discoveries

Planets

This is a list of planets discovered by this survey. This list is incomplete, and requires more information.

  Indicates that the planet orbits one or both stars in a binary system
Star Constellation Right
ascension 		Declination App.
mag. 		Distance (ly) Spectral
type 		Planet Mass
([[Astronomy:Jupiter mass		 J}}}}}}]]) Radius
([[Astronomy:Jupiter radius		 J}}}}}}]]) Orbital
period
(d) 		Semimajor
axis
(AU) 		Orbital
eccentricity 		Inclination
(°) 		Discovery
year
NGTS-1 Columba  05h 30m 51.41s −36° 37′ 51.53″ 15.67 711 M0.5 V NGTS-1b 0.812 1.33 2.65 0.023 0.016 85.27 2017[10]
NGTS-2 Centaurus  14h 20m 29.46s −31° 12′ 07.45″ 10.79 1,162 F5 V NGTS-2b 0.74 1.595 4.51 0.04 0 83.45 2018[14]
NGTS-3 Columba  06h 17m 46.74s −35° 42′ 22.91″ 14.669 2,426 G6 V + K1 V NGTS-3Ab 2.38 1.48 1.68 0.02 0? 89.56 2018[15]
NGTS-4 Columba  05h 58m 23.75s −30° 48′ 42.36″ 13.12 922 K2 V NGTS-4b 0.06 0.25 1.34 0.02 0 82.5 ± 5.8 2018[13]
NGTS-5 Virgo  14h 44m 13.97s 05° 36′ 19.42″ 13.77 1,009 K2 V + M2 V NGTS-5Ab 0.229 1.136 3.36 0.04 0? 86.6 ± 0.2 2019[16]
NGTS-6 Caelum  05h 03m 10.90s −30° 23′ 57.72″ 14.12 1,014 K4 V NGTS-6Ab 1.339 ± 0.028 1.326 0.882 0.01 0 78.231 2019[17]
NGTS-8 Capricornus  21h 55m 54.22s −14° 04′ 6.38″ 13.68 1,399 K0 V NGTS-8b 0.93 ± 0.01 1.09 ± 0.03 2.50 0.035 0.01 86.9 ± 0.5 2019[18]
NGTS-9 Hydra  09h 27m 40.95s −19° 20′ 51.53″ 12.80 1,986 F8 V NGTS-9b 2.90 ± 0.17 1.07 ± 0.06 4.435 0.058 0.06 84.1 ± 0.4 2019[18]
NGTS-10 Lepus  06h 07m 29.31s −25° 35′ 40.61″ 14.34 1,059 K5 V + K5 V NGTS-10Ab 2.162 1.205 0.77 0.0143 0? ? 2019[19]
NGTS-11 Cetus  01h 34m 05.14s −14° 25′ 09.16″ 12.46 621 K2 V NGTS-11b 0.344 0.817 35.455 0.201 0.11 ? 2020[20]
NGTS-12 Centaurus  11h 44m 59.99s −35° 48′ 26.03″ 12.38 1,456 G4 V NGTS-12b 0.208 1.048 7.53  0.0757 0? 88.90 ± 0.76 2020[21]
NGTS-13 Centaurus  11h 44m 57.68s −38° 08′ 22.96″ 12.70 2,151 G2 IV NGTS-13b 4.84 1.142 4.119 0.0549 0.086 88.7 2021[22]
NGTS-14 Grus  21h 54m 04.23s −38° 22′ 38.79″ 13.24 1,060 K1 V + M3 V NGTS-14Ab 0.092 0.44 3.536 0.0403 0? 86.7 2021[23]
NGTS-15 Eridanus  04h 53m 25.27s −32° 48′ 01.25″ 14.67 2,626 G6 V NGTS-15b 0.751 1.10 ± 0.10 3.276 0.0441 0 ? 2021[24]
NGTS-16 Fornax  03h 53m 03.34s −30° 48′ 16.71″ 14.36 3,008 G7 V NGTS-16b 0.667 1.30 4.845 0.0523 0 ? 2021[24]
NGTS-17 Caelum  04h 51m 36.14s −34° 13′ 34.18″ 14.31 3,366 G4 V NGTS-17b 0.764 1.24 ± 0.11 3.242 0.0391 0 ? 2021[24]
NGTS-18 Hydra  12h 02m 11.09s −35° 32′ 54.99″ 14.54 3,689 G5 V NGTS-18b 0.409 1.21 ± 0.18 3.051 0.0448 0 ? 2021[24]
NGTS-20 Eridanus  46h 17m 33.43s −21° 56′ 01.1″ 11.79 1,248 G1 IV NGTS-20b 2.98 1.07±0.04 54.189 0.313 0.432 ± 0.023 88.4 ± 0.6 2022[25]
NGTS-21 Sculptor  20h 45m 01.99s −35° 25′ 40.23″ 14.82 2,090 K3 V NGTS-21b 2.36 ± 0.21 1.33 ± 0.03 1.543 0.0236 0 83.85 ± 0.44 2022[26]
HATS-54 (NGTS-22)[note 1] Phoenix  13h 22m 32.4s −44° 41′ 20.0″ 13.914 2,348 G6 V HATS-54b (NGTS-22b) 1.015 ± 0.024 0.753 ± 0.057 2.544 0.0370 0 83.67 ± 0.34 2018[27][28]
NGTS-23 Horologium  04h 41m 43.6s −40° 02′ 41.0″ 14.010 3,232 F9 V NGTS-23b 0.613 ± 0.097 1.267 ± 0.030 4.076 0.0504 0 89.12 2022[28]
NGTS-24 Antlia  11h 14m 15.3s −37° 54′ 36.5″ 13.192 2,364 G2 IV NGTS-24b 0.520 1.214 3.467 0.0479 0 82.61 2022[28]
NGTS-25 Sagittarius  20h 29m 40.3s −39° 01′ 55.5″ 14.266 1,686 K0 V NGTS-25b 0.639 1.023 2.823 0.0388 0 89.34 2022[28]

Brown dwarfs

In addition, the survey has discovered two brown dwarfs.

Star Constellation Right
ascension 		Declination App.
mag. 		Distance (ly) Spectral
type 		Planet Mass
([[Astronomy:Jupiter mass		 J}}}}}}]]) Radius
([[Astronomy:Jupiter radius		 J}}}}}}]]) Orbital
period
(d) 		Semimajor
axis
(AU) 		Orbital
eccentricity 		Inclination
(°) 		Discovery
year
NGTS-7 A Sculptor  23h 30m 05.26s −38° 58′ 11.70″ 14.34 449 M3/4 V + M3/4 V NGTS-7Ab 75.5 1.349 16.22 h 0.0139 0? 88.43520 2019[29]
NGTS-19 Libra  15h 16m 31.6s −25° 42′ 17.24″ 14.12 1,223 K3 V NGTS-19b 69.5 1.034 17.84 0.1296 0.3767 88.72 2021[30]

See also

  • List of extrasolar planets

Other exoplanet search projects

For a complete list see footer "Exoplanet search projects"

Notes

  1. ↑ Discovered by HATNet, updated parameters by NGTS.

References

  1. ↑ 1.0 1.1 Wheatley, Peter J; West, Richard G; Goad, Michael R; Jenkins, James S; Pollacco, Don L; Queloz, Didier; Rauer, Heike; Udry, Stéphane et al. (2017). "The Next Generation Transit Survey (NGTS)". Monthly Notices of the Royal Astronomical Society 475 (4): 4476–4493. doi:10.1093/mnras/stx2836. 
  2. ↑ "New Exoplanet-hunting Telescopes on Paranal". European Southern Observatory. 14 January 2015. http://www.eso.org/public/news/eso1502/. 
  3. ↑ 3.0 3.1 3.2 3.3 "About NGTS". Next Generation Transit Survey. http://www.ngtransits.org/. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Wheatley, P. J.; Pollacco, D. L.; Queloz, D.; Rauer, H.; Watson, C. A.; West, R. G.; Chazelas, B.; Louden, T. M. et al. (2013). "The Next Generation Transit Survey (NGTS)". EPJ Web of Conferences 47: 13002. doi:10.1051/epjconf/20134713002. Bibcode: 2013EPJWC..4713002W. http://www.epj-conferences.org/articles/epjconf/pdf/2013/08/epjconf_hpcs2012_13002.pdf. 
  5. ↑ "Searching for Super-Earths". Queen's University. 2014. https://star.pst.qub.ac.uk/webdav/public/stfc2014/posters/a1/NGTS%20-%20Watson%20v2%20FINAL.pdf. 
  6. ↑ 6.0 6.1 McCormac, J.; Pollacco, D.; The NGTS Consortium. "The Next Generation Transit Survey Prototyping Phase". http://www.astroscu.unam.mx/rmaa/RMxAC..45/PDF/RMxAC..45_file6-02.pdf. 
  7. ↑ Daniel Clery (14 January 2015). "New exoplanet hunter opens its eyes to search for super-Earths". Science. https://www.science.org/content/article/new-exoplanet-hunter-opens-its-eyes-search-super-earths. 
  8. ↑ 8.0 8.1 "NGTS Science Programme". Next Generation Transit Survey. http://www.ngtransits.org/science.shtml. 
  9. ↑ "SPHERE - Spectro-Polarimetric High-contrast Exoplanet REsearch". European Southern Observatory. http://www.eso.org/sci/facilities/paranal/instruments/sphere.html. 
  10. ↑ 10.0 10.1 Bayliss, Daniel; Gillen, Edward; Eigmüller, Philipp; McCormac, James; Alexander, Richard D; Armstrong, David J et al. (2017). "NGTS-1b: A hot Jupiter transiting an M-dwarf". Monthly Notices of the Royal Astronomical Society 475 (4): 4467. doi:10.1093/mnras/stx2778. Bibcode: 2018MNRAS.475.4467B. 
  11. ↑ Lewin, Sarah (31 October 2017). "Monster Planet, Tiny Star: Record-Breaking Duo Puzzles Astronomers". Space.com. https://www.space.com/38625-monster-planet-circles-tiny-star.html. 
  12. ↑ 12.0 12.1 Staff (31 October 2017). "'Monster' planet discovery challenges formation theory". Phys.org. https://phys.org/news/2017-10-monster-planet-discovery-formation-theory.html. 
  13. ↑ 13.0 13.1 West, Richard G. et al. (2019). "NGTS-4b: A sub-Neptune transiting in the desert". Monthly Notices of the Royal Astronomical Society 486 (4): 5094–5103. doi:10.1093/mnras/stz1084. 
  14. ↑ Raynard, Liam et al. (2018). "NGTS-2b: An inflated hot-Jupiter transiting a bright F-dwarf". Monthly Notices of the Royal Astronomical Society 481 (4): 4960–4970. doi:10.1093/mnras/sty2581. 
  15. ↑ Günther, Maximilian N. et al. (2018). "Unmasking the hidden NGTS-3Ab: A hot Jupiter in an unresolved binary system". Monthly Notices of the Royal Astronomical Society 478 (4): 4720–4737. doi:10.1093/mnras/sty1193. 
  16. ↑ Eigmüller, Philipp et al. (2019). "NGTS-5b: A highly inflated planet offering insights into the sub-Jovian desert". Astronomy & Astrophysics 625: A142. doi:10.1051/0004-6361/201935206. 
  17. ↑ Vines, Jose I. et al. (2019). "NGTS-6b: An ultrashort period hot-Jupiter orbiting an old K dwarf". Monthly Notices of the Royal Astronomical Society 489 (3): 4125–4134. doi:10.1093/mnras/stz2349. 
  18. ↑ 18.0 18.1 Costes, Jean C. et al. (2019). "NGTS-8b and NGTS-9b: Two non-inflated hot-Jupiters". Monthly Notices of the Royal Astronomical Society. doi:10.1093/mnras/stz3140. 
  19. ↑ West, Richard G. et al. (2020). "NGTS-10b: The shortest period hot Jupiter yet discovered". Monthly Notices of the Royal Astronomical Society 493: 126–140. doi:10.1093/mnras/staa115. 
  20. ↑ Gill, Samuel et al. (2020). "NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event". The Astrophysical Journal Letters 898: L11. doi:10.3847/2041-8213/ab9eb9. 
  21. ↑ Bryant, Edward M. et al. (2020). "NGTS-12b: A sub-Saturn mass transiting exoplanet in a 7.53 day orbit". Monthly Notices of the Royal Astronomical Society 499 (3): 3139–3148. doi:10.1093/mnras/staa2976. 
  22. ↑ Grieves, Nolan et al. (2021). "NGTS-13b: A hot 4.8 Jupiter-mass planet transiting a subgiant star". Astronomy & Astrophysics 647: A180. doi:10.1051/0004-6361/202039586. 
  23. ↑ Smith, A. M. S. et al. (2021). "NGTS-14Ab: A Neptune-sized transiting planet in the desert". Astronomy & Astrophysics 646: A183. doi:10.1051/0004-6361/202039712. 
  24. ↑ 24.0 24.1 24.2 24.3 Tilbrook, Rosanna H. et al. (2021). "NGTS 15b, 16b, 17b, and 18b: Four hot Jupiters from the Next-Generation Transit Survey". Monthly Notices of the Royal Astronomical Society 504 (4): 6018–6032. doi:10.1093/mnras/stab815. 
  25. ↑ Ulmer-Moll, S. et al. (2022). "Two long-period transiting exoplanets on eccentric orbits: NGTS-20 b (TOI-5152 b) and TOI-5153 B". Astronomy & Astrophysics 666: A46. doi:10.1051/0004-6361/202243583. 
  26. ↑ Alves, Douglas R. et al. (2022). "NGTS-21b: An inflated Super-Jupiter orbiting a metal-poor K dwarf". Monthly Notices of the Royal Astronomical Society 517 (3): 4447–4457. doi:10.1093/mnras/stac2884. 
  27. ↑ Espinoza, N.; Hartman, J. D.; Bakos, G. Á.; Henning, T.; Bayliss, D.; Bento, J.; Bhatti, W.; Brahm, R. et al. (2019). "HATS-54b–HATS-58Ab: Five New Transiting Hot Jupiters Including One with a Possible Temperate Companion". The Astronomical Journal 158 (2): 63. doi:10.3847/1538-3881/ab26bb. 
  28. ↑ 28.0 28.1 28.2 28.3 Jackson, David G. et al. (2022). "The discovery of three hot Jupiters, NGTS-23b, 24b and 25b, and updated parameters for HATS-54b from the Next Generation Transit Survey". Monthly Notices of the Royal Astronomical Society 518 (4): 4845–4860. doi:10.1093/mnras/stac3192. 
  29. ↑ Jackman, James A G. et al. (2019). "NGTS-7Ab: An ultrashort-period brown dwarf transiting a tidally locked and active M dwarf". Monthly Notices of the Royal Astronomical Society 489 (4): 5146–5164. doi:10.1093/mnras/stz2496. 
  30. ↑ Acton, Jack S. et al. (2021). "NGTS-19b: A high-mass transiting brown dwarf in a 17-d eccentric orbit". Monthly Notices of the Royal Astronomical Society 505 (2): 2741–2752. doi:10.1093/mnras/stab1459. 

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