Ross 248

The Star

This cool and dim, main sequence red dwarf (M5.5 or 4.9 Ve) has around 12 of Sol's mass (RECONS), seven percent of its diameter, but only 11/100,000th of its luminosity. (Another reference, however, suggests seven percent of Sol's mass, 17 percent of its diameter, but the same luminosity). Ross 248 would be only one of many unremarkable stars except that it is one of Sol's closest neighbors. Classified as a "flare star," Ross w48 also has the variable designation HH Andromedae, and investigators have reported finding possible periods of variability at 4.2 years, 120 or 121 days, and five other periods between 60 and 291 days, which may be caused by an unresolved companion (Edward W. Weiss, 1993, page 1139). Useful catalogue numbers for Ross 248 include: HH And, Gl 905, G 171-10, G 190-42, LHS 549, LTT 16985, and LFT 1816.

Jeffrey L. Linsky, JILA, STScI, NASA




Larger image.




Like Gliese 752 B, Ross 248 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

With a spectral type of M5.5, Proxima Centauri can be used as a rough proxy for Ross 248 (M5.5 or 4.9 Ve). Accounting for infrared radiation, the distance from Proxima where an Earth-type planet could have liquid water on its surface is around 0.022 to 0.054 AU (Endl and Kürster, 2008; and Endl et al, 2003, in pdf) -- much closer than Mercury's orbital distance of about 0.4 AU from Sol -- with a corresponding orbital period of 3.6 to 13.8 days (Endl and Kürster, 2008), while the NASA Star and Exoplanet Database has calculated a slightly farther out habitable zone between 0.033 and 0.064 AUs around Proxima. In any case, the rotation of such a close-orbiting planet would probably be tidally locked so that one side would be in perpetual daylight and the other in darkness and be subject to relatively frequent, large flares (as Ross 248 is a known "flare star"). Moreover, 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

There may have been an unconfirmed detection of a substellar companion around Ross 248 with an orbital period of eight years. In the late 1980s, a search using multiple, precise Doppler shift measurements for weak gravitational perturbations by companion objects as small as 20 times Jupiter's mass that are located within 10 AUs of Ross 248 was negative (Butler and Benitz, 1989). Moreover, 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] -------------------------------------