NGTS-1

NGTS-1, also designated as TOI-551 is a solitary star located in the southern constellation Columba, the dove. With an apparent magnitude of 15.52,^[3] NGTS-1 can only be seen through a powerful telescope. Gaia DR3 parallax measurements imply a distance of 710 light-years^[2] and it is drifting away rapidly with a heliocentric radial velocity of 97.2 km/s.^[4]

NGTS-1

Observation data Epoch J2000.0 (ICRS)      Equinox J2000.0 (ICRS)
Constellation	Columba[1]
Right ascension	05h 30m 51.45227s[2]
Declination	−36° 37′ 50.8957″[2]
Apparent magnitude (V)	15.57±0.03[3]
Characteristics
Evolutionary stage	main sequence star[4]
Spectral type	M0.5[4]
B−V color index	+1.37[3]
R−I color index	+1.39[5]
Astrometry
Radial velocity (Rv)	97.18±0.01[4] km/s
Proper motion (μ)	RA: −31.887 mas/yr[2] Dec.: −41.077 mas/yr[2]
Parallax (π)	4.5935±0.017 mas[2]
Distance	710 ± 3 ly (217.7 ± 0.8 pc)
Details[4]
Mass	0.617+0.023 −0.062 M☉
Radius	0.573±0.077 R☉
Luminosity	(7.03±0.09)×10−2[6] L☉
Surface gravity (log g)	4.71±0.23 cgs
Temperature	3,916+71 −63 K
Rotational velocity (v sin i)	<1.0 km/s
Other designations
UCAC2 16099071, NGTS-1, UCAC4 267-006604, DENIS J053051.4-363750, TIC 192826603 USNO-B1.0 0533-00066386, 2MASS J05305145-3637508,UCAC3 107-15281, Gaia DR2 4821739369794767744
Database references
SIMBAD	data
Exoplanet Archive	data

Properties

NGTS-1 has a stellar classification of M0.5, indicating that is an early M-type star. It has 61% of the mass of the Sun and over half of its radius.^[4] Since red dwarfs are fully convective, they do not burn as much as more massive stars. As a result, NGTS-1 only radiates 7.02% of the luminosity of the Sun from its photosphere at an effective temperature of 3,916 K.^[4] There was difficulty determining the metallicity of the object due to its faintness, but NGTS-1 is assumed to be around solar metallicity.^[4] In addition, this also provided some uncertainty about the star's properties since red dwarfs properties are dependent on their metallicity. It spins too slowly for it to be measured accurately, having a projected rotational velocity lower than 1.0 km/s.^[4]

Planetary system

The discovery of a hot Jupiter orbiting the star was reported in 2017 as part of the Next Generation Transit Survey.^[4] The media also dubbed NGTS-1b as "monstrous" since the planet is relatively large compared to its host star.^[7]

The NGTS-1 planetary system^[4]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.812+0.066 −0.075 MJ	0.0326+0.0047 −0.0045	2.6473068±0.0000017[8]	0.016+0.023 −0.012	85.27+0.61 −0.73°	1.33+0.61 −0.33 RJ