The Next-Generation Transit Survey (NGTS) is a ground-based robotic search for

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s. The facility is located at

Paranal Observatory Paranal Observatory is an astronomical observatory operated by the European Southern Observatory (ESO). It is located in the Atacama Desert of northern Chile on Cerro Paranal at altitude, south of Antofagasta. By total light-collecting area, it ...

in the Atacama desert in northern Chile, about 2 km from

ESO The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based ast ...

Very Large Telescope The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, ...

and 0.5 km from the VISTA Survey Telescope. Science operations began in early 2015. The

astronomical survey An astronomical survey is a general map or image of a region of the sky (or of the whole sky) that lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of images, spectra, or other observations of obje ...

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. The aim of NGTS is to discover super-Earths and exo-

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

s transiting relatively bright and nearby stars with an apparent magnitude of up to 13. The survey uses

transit photometry Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty ...

, 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 Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

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. NGTS builds heavily on experience with

SuperWASP WASP or Wide Angle Search for Planets is an international consortium of several academic organisations performing an ultra-wide angle search for exoplanets using transit photometry. The array of robotic telescopes aims to survey the entire sky, ...

, using more sensitive detectors, refined software, and larger optics, though having a much smaller field of view. 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. NGTS is suited to ground-based photometric follow-up of exoplanet candidates from space-based telescopes such as

TESS Tess or TESS may refer to: Music * Tess (band), a Spanish pop band active from 2000 to 2005 * TESS (musician), a UK musician Film and theatre * ''Tess'' (1979 film), a 1979 film adaptation of '' Tess of the d'Urbervilles'' * ''Tess'' (2016 film) ...

, ''Gaia'' and

PLATO Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was a Greek philosopher born in Athens during the Classical period in Ancient Greece. He founded the Platonist school of thought and the Academy, the first institution ...

. In turn, larger instruments such as

HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...

ESPRESSO Espresso (, ) is a coffee-brewing method of Italian origin, in which a small amount of nearly boiling water (about ) is forced under of pressure through finely-ground coffee beans. Espresso can be made with a wide variety of coffee beans and ...

and

VLT-SPHERE Spectro-Polarimetric High-contrast Exoplanet REsearch (VLT-SPHERE) is an adaptive optics system and coronagraphic facility at the Very Large Telescope (VLT). It provides direct imaging as well as spectroscopic and polarimetric characterization o ...

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.

Science mission

Ground-based surveys for extrasolar planets such as

WASP A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...

and the

HATNet Project The Hungarian Automated Telescope Network (HATNet) project is a network of six small fully automated "HAT" telescopes. The scientific goal of the project is to detect and characterize extrasolar planets using the transit method. This network is use ...

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. 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. 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

(VLT), European Extremely Large Telescope (E-ELT), and the

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope which conducts infrared astronomy. As the largest optical telescope in space, its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble Spa ...

(JWST). Such targets are more readily characterized in terms of their atmospheric composition, planetary structure, and evolution than smaller targets orbiting larger stars. 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. 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 HD 189733 b is an exoplanet approximately away from the Solar System in the constellation of Vulpecula. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. ...

and GJ 1214 b. NGTS is intended to greatly increase the number of planets that area analyzable using such techniques. 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.

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. 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.

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 The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...

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 The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...

(HARPS) at La Silla Observatory;

for radial-velocity measurements at the VLT;

SPHERE A sphere () is a Geometry, geometrical object that is a solid geometry, three-dimensional analogue to a two-dimensional circle. A sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

, an adaptive optics system and coronagraphic facility at the VLT that directly images extrasolar planets; and a variety of other VLT and planned E-ELT instruments for atmospheric characterization.

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: * DLR, Institute for Planetary Research * Geneva Observatory *

Queen's University Belfast , mottoeng = For so much, what shall we give back? , top_free_label = , top_free = , top_free_label1 = , top_free1 = , top_free_label2 = , top_free2 = , established = , closed = , type = Public research university , parent = ...

University of Cambridge , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

* University of Chile *

University of Leicester , mottoeng = So that they may have life , established = , type = public research university , endowment = £20.0 million , budget = £326 million , chancellor = David Willetts , vice_chancellor = Nishan Canagarajah , head_labe ...

University of Warwick The University of Warwick ( ; abbreviated as ''Warw.'' in post-nominal letters) is a public research university on the outskirts of Coventry between the West Midlands (county), West Midlands and Warwickshire, England. The university was founded i ...

Results

* On 31 October 2017, the discovery of

NGTS-1b NGTS-1b is a confirmed hot Jupiter-sized extrasolar planet orbiting NGTS-1, a red dwarf star about half the mass and radius of the Sun, every 2.65 days. The NGTS-1 system is about 716 light-years from Earth in the Columba constellation. Dis ...

, a confirmed

hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temp ...

-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. Daniel Bayliss, of the

, 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." * On 3 September 2018, the discovery of

NGTS-4b The Neptunian Desert or sub-Jovian desert is broadly defined as the region close to a star (period 0.1 ) exoplanets are found. This area receives strong irradiation from the star, meaning the planets do not retain their gaseous atmosphere as ...

, 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 and radius 3.18 ± 0.26 , which places it well within the so-called "

Neptunian Desert The Neptunian Desert or sub-Jovian desert is broadly defined as the region close to a star (period 0.1 ) exoplanets are found. This area receives strong irradiation from the star, meaning the planets do not retain their gaseous atmosphere as ...

". 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.

Discoveries

This is a list of planets discovered by this survey. This list is incomplete, and requires more information. ''Light green indicates that the planet orbits one or both stars in a binary system.'' In addition, the survey has discovered two brown dwarfs.

Notes

References

External links

* *
The Next Generation Transit Survey Becomes Operational at Paranal
ESO archive, The Messenger 165 – September 2016 {{Portal bar, Stars, Spaceflight, Solar System, Science Articles containing video clips Astronomical instruments Astronomical surveys European Southern Observatory Exoplanet search projects by small telescope Telescopes