Ross 128

Due to Ross 128's proximity to Sol, the star has been an object of high interest among astronomers. It has been selected as a "Tier 1" target star for NASA's optical Space Interferometry Mission (SIM) to detect a planet as small as three Earth-masses within two AUs of its host star (and so some summary system information and may still be available from the SIM Teams). The SIM project manager announced on November 8, 2010, however, that the mission was indefinitely postponed due to withdrawal of NASA funding.

Medialab, © ESA 2002



Larger illustration of
the Darwin Mission.



Astronomers have identified
Ross 128 as a prime target
for NASA's optical SIM and the
ESA's infrared Darwin missions,
now both indefinitely postponed.

The Star

This cool and dim, main sequence red dwarf (M4.1 Vn) has around 16 to 18 percent of Sol's mass (RECONS; and Jenkins et al, 2009), 21 percent of its diameter (NASA Star and Exoplanet Database, derived from the power law formula of Kenneth R. Lang, 1980), but only 33/100,000th of its visual luminosity and around 0.3 percent of its bolometric luminosity (NASA Star and Exoplanet Database, derived from the exponential formula of Kenneth R. Lang, 1980). Ross 128 would be only one of many unremarkable stars except that it appears to be a flare star as well as one of Sol's closest neighbors. In contrast to Proxima Centauri which is a "magnetically younger" flare star that is "activity saturated", however, Ross 128 is considered to be a more "evolved" flare star where its flare rate may have decreased somewhat with increased magnetic evolution (Andrew Skumanich, 1986). Although dust has been detected around the star, astronomers have failed to detect a cold debris disk from dust at 10 to 50 degrees Kelvin (Lestrade et al, 2009; and Chen et al, 2006, FI Vir in Table 1). It's variable star designation is FI Virginis, but other useful catalogue numbers include: FI Vir, Gl 447, Hip 57548, G 10-50, LHS 315, LTT 13240, and LFT 852.

Jeffrey L. Linsky, JILA, STScI, NASA




Larger image.




Like Gliese 752 B, Ross 128 is so small,
with less than 20 percent of Sol's mass,
that it can transport core heat only through
convection, unlike larger larger red dwarf
stars like Gliese 752 A (more).

Habitable Zone

According to one type of model calculations performed for the NASA Star and Exoplanet Database, their estimate of the HZ is centered around 0.083 AU, with inner edge of Ross 128's habitable zone at around 0.057 AU from the star, while the outer edge lies farther out at around 0.110 AU. At such a close in orbit, the rotation of the planet may become tidally locked with the star so that one side would have eternal daylight and the other would be in darkness.

Arnold O. Benz, Institute of Astronomy, ETH Zurich

High resolution and jumbo images (Benz et al, 1998).

Ross 128 is a flare star, like UV Ceti (Luyten 726-8 B)
shown flaring at left. UV Ceti is an extreme example
of a flare star that can boost its brightness by five times
in less than a minute, then fall somewhat slower back
down to normal luminosity within two or three minutes
before flaring suddenly again after several hours.

Life Around a Flare Star

Many dim, red (M) dwarf stars exhibit unusually violent flare activity for their size and brightness. These flare stars are actually common because red dwarfs make up more than half of all stars in the galaxy. Although flares do occur on our Sun every so often, the amount of energy released in a solar flare is small compared to the total amount of energy Sol produces. However, a flare the size of a solar flare occurring on a red dwarf star (such as Ross 128) that is more than ten thousand times dimmer than our Sun would emit about as much or more light as the red dwarf itself, doubling its brightness or more.

Flare stars erupt sporadically, with successive flares spaced anywhere from an hour to a few days apart. A flare only takes a a few minutes to reach peak brightness, and more than one flare can occur at a time. Moreover, in addition to bursts of light and radio waves, flares on dim red dwarfs may emit up to 10,000 times as many X-rays as a comparably-sized solar flare on our own Sun, and so flares would be lethal to Earth-type life on planets near the flare star. Hence, Earth-type life around flare stars may be unlikely because planets must be located very close to dim red dwarfs to be warmed sufficiently by infrared-rich star light to have liquid water (about 0.083 AU with an orbital period of less than 22 days for Ross 128), which makes flares even more dangerous around such stars. In any case, the light emitted by red dwarfs may be too red in color for Earth-type plant life to perform photosynthesis efficiently.

Hunt for Substellar Companions

A recent search for faint companions using the Hubble Space Telescope found no supporting evidence for a large Jupiter or brown dwarf sized object (Schroeder et al, 2000).

------------------------------------- [Guide] -- [Full Near Star Map] -------------------------------------