Ross 128 is a red dwarf in the equatorial zodiac constellation of Virgo, near β Virginis. The apparent magnitude of Ross 128 is 11.13,^[3] which is too faint to be seen with the unaided eye. Based upon parallax measurements, the distance of this star from Earth is 11.007 light-years (3.375 parsecs), making it the twelfth closest stellar system to the Solar System. It was first cataloged in 1926 by American astronomer Frank Elmore Ross.^[16]

Quick Facts Observation data Epoch J2000 Equinox J2000, Constellation ...

Ross 128

Artist's impression of the planet Ross 128 b, with the star Ross 128 visible in the background[1] Credit: European Southern Observatory
Observation data Epoch J2000      Equinox J2000
Constellation	Virgo
Right ascension	11h 47m 44.39727s[2]
Declination	+00° 48′ 16.4003″[2]
Apparent magnitude (V)	11.13[3]
Characteristics
Evolutionary stage	Main sequence
Spectral type	M4V[4]
U−B color index	+2.685[5]
B−V color index	+1.59[6]
Variable type	Flare star[7]
Astrometry
Radial velocity (Rv)	−31.0[8][9] km/s
Proper motion (μ)	RA: 607.299±0.034 mas/yr[2] Dec.: −1223.028±0.023 mas/yr[2]
Parallax (π)	296.3053 ± 0.0302 mas[2]
Distance	11.007 ± 0.001 ly (3.3749 ± 0.0003 pc)
Absolute magnitude (MV)	13.53[3]
Details
Mass	0.176±0.004[10] M☉
Radius	0.198±0.007[10] R☉
Luminosity (bolometric)	0.00366 ± 0.00005[10] L☉
Surface gravity (log g)	3.40[11] cgs
Temperature	3,189+55 −53[10] K
Metallicity [Fe/H]	−0.02±0.08[12] dex
Rotational velocity (v sin i)	2.1±1.0[13] km/s
Age	5.0[14] Gyr
Other designations
FI Virginis, FI Vir, G 010-050, GCTP 2730, GJ 447, HIP 57548, LHS 315, Vyssotsky 286, LTT 13240, LFT 852, LSPM PM I11477+0048.[15]
Database references
SIMBAD	data
Ross 128 Location of Ross 128 in the constellation Virgo

Close

This low-mass star has a stellar classification of M4 V,^[4] which places it among the category of stars known as red dwarfs. It has about 18%^[10] of the mass of the Sun and 20%^[10] of the Sun's radius, but generates energy so slowly that it has only 0.033% of the Sun's visible luminosity;^[3] however, most of the energy being radiated by the star is in the infrared band, with the bolometric luminosity being equal to 0.37% of solar.^[10] This energy is being radiated from the star's outer atmosphere at an effective temperature of 3,180 K.^[4] This gives it the cool orange-red glow of an M-type star.

Ross 128 is an old disk star, which means it has a low abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, and it orbits near the plane of the Milky Way galaxy.^[17] The star lacks a strong excess of infrared radiation. An infrared excess is usually an indicator of a dust ring in orbit around the star.^[18][19]

In 1972, a flare was detected from Ross 128. It was observed to increase in brightness by about half a magnitude in the ultraviolet U band, returning to normal brightness in less than an hour. At optical wavelengths, the brightness changes were almost undetectable.^[20] It was classified as a flare star and given the variable star designation FI Virginis.^[21] Because of the low rate of flare activity, it is thought to be a magnetically evolved star. That is, there is some evidence that the magnetic braking of the star's stellar wind has lowered the frequency of flares, but not the net yield.^[22]

Brightness variations thought to be due to rotation of the star and magnetic cycles similar to the sunspot cycle have also been detected. These cause changes of just a few thousandths of a magnitude. The rotation period is found to be 165.1 days, and the magnetic cycle length 4.1 years.^[23]

Ross 128 is orbiting through the galaxy with an eccentricity of 0.122, causing its distance from the Galactic Center to range between 26.8–34.2 kly (8.2–10.5 kpc).^[24] This orbit will bring the star closer to the Solar System in the future. The nearest approach will occur in approximately 71,000 years, when it will come within 6.233 ± 0.085 ly (1.911 ± 0.026 pc).^[9]

Ross 128 b was discovered in July 2017 by the HARPS instrument at the La Silla Observatory in Chile, by measuring changes in radial velocity of the host star. Its existence was confirmed on 15 November 2017. It is the second-closest known Earth-size exoplanet, after Proxima b.^[27] It is calculated that Ross 128 b has a mass of 1.8 times the Earth, a radius 1.6 times that of the Earth, and orbits 20 times closer to its star than Earth orbits the Sun, intercepting only about 1.38 times more solar radiation than Earth,^[26][25][28] increasing the chance of retaining an atmosphere over a geological timescale. Ross 128 b is a closely orbiting planet, with a year (orbital period) lasting about 9.9 days.^[29][30] At that close distance from its host star, the planet is most likely tidally locked, meaning that one side of the planet would have eternal daylight and the other would be in darkness.^[31][32] Near-infrared high-resolution spectra from APOGEE have demonstrated that Ross 128 has near solar metallicity; Ross 128 b therefore most likely contains rock and iron. Furthermore, recent models generated with these data support the conclusion that Ross 128 b is a "temperate exoplanet in the inner edge of the habitable zone."^[33]

In the spring of 2017, Arecibo astronomers detected strange radio signals thought to originate from Ross 128 that were unlike any they had seen before.^[34] SETI's Allen Telescope Array was used for follow-up observations and was unable to detect the signal but did detect man made interference, making it seem clear that the Arecibo detections were due to transmissions from Earth satellites in geosynchronous orbit. Ross 128 has a declination (a coordinate which can be likened to latitude) of close to 0 degrees, which places it in the thick of a phalanx of these satellites. Therefore, it can be concluded that the signal was a result of man-made interference.^[35]

• List of nearest stars and brown dwarfs
• PSR B1919+21 – pulsar mistaken for an alien radio signal (LGM-1)