Hubbry Logo
Ross 128Ross 128Main
Open search
Ross 128
Community hub
Ross 128
logo
7 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Ross 128
Ross 128
Ross 128
View on Wikipedia
from Wikipedia
Ross 128
Ross 128 is located in the constellation Virgo.
Ross 128 is located in the constellation Virgo.
 Ross 128
Location of Ross 128 in the constellation Virgo

Observation data
Epoch J2000      Equinox J2000
Constellation Virgo[1]
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(34) mas/yr[2]
Dec.: −1223.028(23) mas/yr[2]
Parallax (π)296.3053±0.0302 mas[2]
Distance11.007 ± 0.001 ly
(3.3749 ± 0.0003 pc)
Absolute magnitude (MV)13.53[3]
Details
Mass0.176±0.004[10] M☉
Radius0.198±0.007[10] R☉
Luminosity (bolometric)0.00366 ± 0.00005[10] L☉
Surface gravity (log g)3.40[11] cgs
Temperature3,189+55
−53[10] K
Metallicity [Fe/H]−0.02±0.08[12] dex
Rotation101–223 days[13]
Rotational velocity (v sin i)2.1±1.0[14] km/s
Age5.0[15] Gyr
Other designations
FI Vir, GJ 447, HIP 57548, G 10-50, LFT 852, LHS 315, LSPM J1147+0048, LTT 13240, PLX 2730, Ross 128, Vyssotsky 286[16]
Database references
SIMBADdata
Exoplanet Archivedata

Ross 128 is a red dwarf star 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.[17]

Properties

[edit]
Distances of the nearest stars from 20,000 years ago until 80,000 years in the future

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.[18] 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.[19][20]

Light curves for a flare on FI Virginis, seen in ultraviolet, blue and visual band light, adapted from Lee and Hoxie (1972),[21]

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.[21] It was classified as a flare star and given the variable star designation FI Virginis.[22] 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.[23]

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.[24]

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).[25] 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]

Planetary system

[edit]
Main article: Ross 128 b
Artist's impression of the planet Ross 128 b, with the star Ross 128 visible in the background[26]

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] Ross 128 b has a minimum mass 1.4 times that of Earth; a 2019 study predicts a true mass about 1.8 times Earth and a radius about 1.6 times that of the Earth, with large margins of error.[28] It orbits 20 times closer to its star than Earth orbits the Sun, intercepting only about 1.38 times more solar radiation than Earth,[29][30] 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.[31][32] 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.[33][34] 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."[35]

The Ross 128 planetary system[13]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥1.40±0.13 M🜨 0.049640±0.000004 9.8556+0.0012
−0.0011 		0.21+0.09
−0.10 		— ~1.6+1.1
−0.65[28] R🜨

A 2024 study of the radial velocity data found an eccentricity of about 0.21 for Ross 128 b, higher than previous estimates and similar to that of Mercury. Given the planet's orbit near the inner edge of the habitable zone, such a high eccentricity would significantly decrease its potential for habitability. This study also searched for additional planets in the system, and did not find any.[13]

Radio signals

[edit]

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.[36] 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 most likely a result of man-made interference.[37]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Ross 128

View on Grokipedia
from Grokipedia
Ross 128 is a star of spectral type , located approximately 11 light-years (3.38 parsecs) from the Sun in the constellation Virgo. It has a mass of 0.168 solar masses, a radius of 0.197 solar radii, an of 3192 K, and a of 0.00362 solar luminosities, making it a cool, low-mass main-sequence star with solar ([Fe/H] = -0.02). The star exhibits minimal magnetic activity compared to many M dwarfs, with a rotation period of about 121 days and an age estimated at greater than 5 billion years. Its apparent visual magnitude is 11.15, rendering it invisible to the but observable with small telescopes. The most notable feature of the Ross 128 system is the Ross 128 b, a discovered in 2017 using measurements from ESO's HARPS instrument. This has a minimum mass of 1.40 masses and orbits its star every 9.87 days at a semi-major axis of 0.050 AU, placing it near the inner edge of the where liquid water might exist under certain atmospheric conditions. With an estimated equilibrium temperature ranging from 213 K to 301 K (depending on ), Ross 128 b is considered potentially temperate and rocky, though its exact and composition remain uncertain without direct or transit data. Likely tidally locked due to its close orbit—about 20 times nearer to its star than is to the Sun—the may feature one hemisphere in perpetual daylight and the other in endless night, influencing its climate and habitability prospects. Ross 128 b stands out as the second-closest potentially habitable to , after , and orbits the quietest nearby M dwarf known to host such a world, reducing the risk of atmospheric erosion from stellar flares. The system's proximity makes it a prime target for future observations with telescopes like ESO's , potentially allowing spectroscopic analysis of the planet's atmosphere for biosignatures. Additionally, Ross 128 is approaching our solar system and is projected to become its closest stellar neighbor in about 79,000 years.

Discovery and observation history

Cataloging and early studies

Ross 128 was discovered in 1926 by American astronomer Frank Elmore Ross as part of his systematic survey for high stars conducted at . Ross utilized photographic plates exposed over intervals of approximately 20 years, employing a blink comparator to detect stellar motion against the background of fixed stars. This method allowed him to identify faint, nearby stars moving rapidly across the sky relative to more distant ones. The star appeared as the 128th entry in Ross's second list of new proper motion stars, published in The Astronomical Journal, with a total proper motion of approximately 1.3 arcseconds per year, primarily in the direction. Historically, is computed from positional changes over time, approximated as μ = √[(Δα cos δ / t)^2 + (Δδ / t)^2], where t is the epoch baseline between plates. Early spectral analysis in classified Ross 128 as an M4 dwarf, consistent with its red coloration and faint luminosity indicative of a cool, low-mass main-sequence star. Trigonometric measurements provided initial distance estimates of around 10 light-years, refined in subsequent pre-Gaia studies to approximately 11 light-years based on improved photographic techniques and longer observational baselines.

Modern observations

Since the early 2000s, observations of Ross 128 have benefited from high-precision instruments focused on measurements and . Intensive monitoring with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph on the 3.6 m at began in 2007, accumulating over a decade of data comprising 72 measurements primarily aimed at detecting exoplanets around nearby M dwarfs. These observations provided detailed time series of the star's radial velocities, enabling the identification of periodic signals associated with planetary companions. The Gaia mission has further refined the astrometric parameters of Ross 128 through its Data Release 3 (DR3) in 2022, yielding a precise parallax of 296.3053 ± 0.0302 mas, corresponding to a distance of approximately 3.375 pc (as of 2025, this remains the most precise astrometry available). This release highlights the star's location in the constellation Virgo, positioned about 1.1° southwest of β Virginis, with proper motions of μ_α cos δ = 607.678 ± 0.137 mas yr⁻¹ and μ_δ = -1223.32 ± 0.078 mas yr⁻¹. Near-infrared high-resolution of Ross 128 was conducted using the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey, providing the first detailed chemical abundance analysis based on spectra in the 1.5–1.7 μm range at R ≈ 22,500. This revealed near-solar with [Fe/H] = +0.03 ± 0.09 dex (superseding earlier estimates of [Fe/H] = -0.02), alongside abundances for key elements such as [O/H] = -0.02 ± 0.06 dex, [Mg/H] = -0.10 ± 0.13 dex, and [Ca/H] = -0.01 ± 0.03 dex, derived through spectral synthesis modeling. Ross 128 has an of 11.153 ± 0.002 in the V-band, rendering it faint and challenging for ground-based optical observations without large telescopes, but well-suited for studies where it peaks in brightness.

Stellar characteristics

Physical properties

Ross 128 is classified as an M4.0 V star. Analysis of near- spectra from the APOGEE survey yields an of 3231 ± 100 K and a of log g = 4.96 ± 0.11 dex. Its is near solar, with [Fe/H] = -0.02 ± 0.08. The star's mass is estimated at 0.168 ± 0.017 M⊙ based on models calibrated to its spectral type and . Its measures 0.1967 ± 0.0077 R⊙, while the bolometric is 0.00362 ± 0.00039 L⊙. These parameters position Ross 128 as a low-mass, cool main-sequence star with subdued energy output compared to the Sun. The can be derived from the fundamental relation for : L=4πR2σT4L = 4\pi R^2 \sigma T^4 where σ=5.670×10−8\sigma = 5.670 \times 10^{-8} W m−2^{-2} K−4^{-4} is the Stefan-Boltzmann constant, RR is the stellar radius, and TT is the effective temperature. Substituting the measured values (R≈0.20R \approx 0.20 R⊙ = 1.39×1081.39 \times 10^8 m and T≈3200T \approx 3200 K) yields L≈0.0036L \approx 0.0036 L⊙, consistent with observational determinations. Gaia Data Release 3 provides a precise distance of 3.375 ± 0.001 pc (11.007 light-years), derived from a parallax of π=0.2964±0.0003\pi = 0.2964 \pm 0.0003 mas. The star's age is estimated at approximately 7 Gyr through gyrochronology, which relates its slow rotation period (∼121 days) to evolutionary models for M dwarfs; this makes Ross 128 older than the Sun (4.6 Gyr) and contributes to its relatively low magnetic activity.

Activity and variability

Ross 128 is characterized by low magnetic and chromospheric activity, making it a notably quiet red dwarf among M-type stars. Its chromospheric activity index, log RHK′≈−5.62R'_{HK} \approx -5.62, reflects minimal emission in the Ca II H and K lines relative to its bolometric luminosity, indicating subdued stellar activity processes. This index is defined by the formula RHK′=log⁡(LHKLbol),R'_{HK} = \log \left( \frac{L_{HK}}{L_{bol}} \right), where LHKL_{HK} is the luminosity emitted in the Ca II H and K lines and LbolL_{bol} is the star's total bolometric luminosity; the low value for Ross 128 places it well below the saturation threshold for M dwarfs, resulting in reduced X-ray and ultraviolet flaring compared to more active counterparts like Proxima Centauri, which exhibits significantly higher activity levels. The star's slow period of approximately 121 days, determined from long-term photometric monitoring, further contributes to its quiescence. This period is longer than the typical 20–50 days observed for other M4 dwarfs, leading to weaker dynamo-generated and diminished stellar winds. Measurements of Hα emission reveal only occasional weak activity, consistent with the overall inactive profile and a detected ~5.4-year activity cycle that modulates chromospheric emissions without producing strong flares. Photometric observations from the (TESS) between 2018 and 2020 show no significant variability, with an amplitude less than 0.01 magnitudes, underscoring the star's stability. This low level of radiative variability implies a relatively consistent energy output, beneficial for maintaining stable conditions around orbiting bodies.

Planetary system

Discovery of

The was discovered through observations conducted with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph mounted on the European Southern Observatory's (ESO) 3.6 m telescope at in . A team led by Xavier Bonfils announced the detection on November 15, 2017, based on data collected over 157 nights spanning from July 2005 to April 2016. The observations revealed a coherent periodic signal in the star's with an of 9.87 days and a semi-amplitude KK of 1.39±0.181.39 \pm 0.18 m/s. The signal's planetary origin was confirmed by modeling the HARPS time series with a Keplerian superimposed on a to account for residual stellar activity, yielding a best-fit minimum mass mpsin⁡i=1.40±0.21m_p \sin i = 1.40 \pm 0.21 masses. Stellar activity was ruled out as the cause through showing the star's period of approximately 123 days, which is distinct from the planet's , and the low level of chromospheric activity consistent with a quiet M dwarf. The derived orbital semi-major axis is 0.0496±0.00170.0496 \pm 0.0017 AU, positioning the planet near the inner edge of the system's where equilibrium temperatures could range from 213 to 301 depending on atmospheric properties. Follow-up photometric monitoring using data from NASA's mission (Campaign C01) covered 82 days and detected no transits, excluding non-grazing transits for planets larger than 0.190.19 radii at 99% confidence. This non-detection implies either a low or a small planetary radius. The semi-amplitude KK quantifies the detected signal and is derived from the standard formula for a (with eccentricity e≈0e \approx 0): K=(2πGP)1/3Mpsin⁡iM⋆2/3K = \left( \frac{2\pi G}{P} \right)^{1/3} \frac{M_p \sin i}{M_\star^{2/3}} where PP is the , GG is the , Mpsin⁡iM_p \sin i is the minimum , and M⋆M_\star is the . For , substituting P=9.87P = 9.87 days, Mpsin⁡i=1.40M_p \sin i = 1.40 Earth masses, and M⋆=0.17M_\star = 0.17 solar masses yields K≈1.39K \approx 1.39 m/s, consistent with the observed value from fitting of the HARPS data.

Characteristics of Ross 128 b

is a with a minimum mass of 1.40 ± 0.21 masses, determined through measurements. Its orbit has a period of 9.86 days and a semi-major axis of 0.0496 AU, placing it close to its host star and resulting in an of 0.21^{+0.09}_{-0.10}, as refined by a 2024 reanalysis of HARPS and CARMENES data that also confirms no additional s in the system. This eccentricity is higher than initial estimates and comparable to that of Mercury. The planet receives an insolation of approximately 1.38 times that of , adjusted for the M4V stellar spectrum, which positions it near the inner edge of the system's . The equilibrium temperature of Ross 128 b is estimated at around 270 , calculated assuming an Earth-like of 0.367 and efficient heat redistribution across the planetary surface. This value falls within the optimistic boundaries for its star, with a range from 213 (high albedo of 0.75, Venus-like) to 301 (zero ). Due to its short and proximity to the low-mass host star, is likely, potentially leading to a permanent day-night contrast on the surface. Models of the planet's interior suggest a likely composition, dominated by s and iron, consistent with super-Earths in this regime. The is estimated at approximately 1.1 radii, derived from mass- relations for solid planets; for a of 1.35 ⊕, theoretical models predict a of about 1.07 ⊕ for a pure-rock (MgSiO₃) composition or slightly less (∼0.95 ⊕) for a 30% iron core with a mantle. These relations follow the approximate form RpR⊕=f(MpM⊕),\frac{R_p}{R_\oplus} = f\left(\frac{M_p}{M_\oplus}\right), where ff incorporates interior structure equations of state for rocky materials, as detailed in Seager et al. (2007), yielding a dense, Earth-like interior without significant volatile envelopes. If an atmosphere is present, the planet's surface conditions could support liquid water within the habitable temperature range, though this depends on atmospheric composition and thickness.

Radio signals

2017 detection

In May , an unusual radio signal was detected from the direction of Ross 128 during observations of nearby stars using the 305-meter Arecibo radio telescope in . The emission was recorded on over a 10-minute session, spanning a frequency range of 4.6 to 4.8 GHz with a bandwidth of approximately 200 MHz. The signal consisted of unpolarized, broadband radiation featuring quasi-periodic pulses and strong dispersion-like characteristics, which are indicative of propagation effects through interstellar plasma; it persisted throughout the observation without interruption. Detected above the instrument's 1-σ sensitivity limit of 0.12 Jy, the flux density was notable for a source at Ross 128's distance of 3.4 parsecs. Unlike typical radio emissions from quiet M-dwarfs, which exhibit low activity levels, the signal's properties deviated from expected stellar phenomena. Initial analysis raised speculation of a non-natural origin, as the emission's stability and uniqueness—absent in contemporaneous observations of other stars like —suggested it was not conventional RFI or known astrophysical processes. This prompted targeted follow-up efforts, including additional sessions in July 2017, to characterize its intermittency and intensity variations.

Source identification

In July 2017, the team, led by Abel Méndez, conducted a detailed analysis of the detected earlier that year and attributed it to radio transmissions from one or more geostationary satellites operated by companies such as SES or . This conclusion was supported by the signal's origin in the direction of Ross 128, which lies near the at a of approximately +1°, aligning with the geostationary orbital arc visible from Arecibo's of 18°N. The signal's characteristics further corroborated a terrestrial origin, exhibiting broadband emission in the 4.6–4.8 GHz range—consistent with C-band satellite downlinks—along with unpolarized properties and apparent distortions resembling dispersion from multipath reflections off Earth's ionosphere or surface. Analysis of the frequency drifts revealed patterns matching the relative motions of Earth-orbiting satellites, where the fractional frequency shift follows the relativistic Doppler relation Δf/f=v/c\Delta f / f = v / c, with vv representing the line-of-sight velocity (on the order of kilometers per second for orbital dynamics) and cc the speed of light; these drifts aligned with expected geostationary satellite behaviors rather than astrophysical sources. Follow-up observations in July 2017 using the and detected no recurrence of the signal, reinforcing the interference hypothesis and ruling out a persistent astrophysical emitter associated with Ross 128. This incident highlighted the challenges of interference (RFI) in SETI searches, particularly from the growing constellation of geostationary satellites, and underscored the importance of multi-telescope, multi-wavelength confirmations to mitigate false positives in the quest for .

Scientific significance

Habitability potential

Ross 128, an inactive , exhibits a notably low flare rate compared to more active red dwarfs such as , which reduces the risk of atmospheric erosion on orbiting planets like . This relative quiescence, characterized by a slow rotation period of approximately 100 days and low magnetic activity (log R'_HK = -5.57), enhances the potential for long-term atmospheric retention, a critical factor for . The around Ross 128 spans approximately 0.04 to 0.10 AU, calculated using the scaling relation d=L⋆L⊙×d\Earthd = \sqrt{\frac{L_\star}{L_\odot}} \times d_\Earth
Add your contribution
Related Hubs
User Avatar
No comments yet.