Ross 248
A dim red dwarf predicted to become the nearest star to the Sun.
Ross 248, also known as HH Andromedae or Gliese 905, is a red dwarf star located about 10.30 light-years away in the constellation Andromeda. Though it is relatively close to Earth, it is far too faint to be seen without a telescope. Frank Elmore Ross first recorded it in 1926 while compiling his second catalog of stars with high proper motion. The star was too dim for the Hipparcos satellite to measure. In roughly 40,000 years, the Voyager 2 spacecraft will pass within 1.7 light-years of it. Over the next 80,000 years, Ross 248 is expected to become the Sun’s closest stellar neighbor for about 9,000 years, taking that title from the current record-holder, the triple star system Alpha Centauri.
The star has about 14% of the Sun’s mass and 19% of its radius, but only 0.2% of its luminosity. Its spectral type is M6 V, classifying it as a main-sequence red dwarf. It is chromospherically active and likely follows a long-term variability cycle lasting 4.2 years, which causes its visual magnitude to shift between 12.23 and 12.34. In 1950, Ross 248 became the first star known to vary in brightness due to spots on its rotating surface, a category now called BY Draconis variables. Searches for a brown dwarf or stellar companion have turned up nothing: no evidence exists for an object orbiting between 100 and 1,400 AU, and observations with the Hubble Space Telescope’s Wide Field Planetary Camera and near-infrared speckle interferometry have also been unsuccessful. Long-term monitoring at Sproul Observatory has detected no astrometric wobble from an unseen companion.
The star’s space velocity components in the galactic coordinate system are [U, V, W] = [−32.9±0.7, −74.3±1.3, 0.0±1.4] km/s, and its trajectory is bringing it closer to the Solar System. In 1993, Matthews calculated that in about 33,000 years it would begin a roughly 9,000-year period as the nearest star, reaching a minimum distance of 3.024 light-years around 36,000 years from now. A more refined 2022 estimate puts the closest approach at 3.048 light-years in about 36,500 years. Any future spacecraft leaving the Solar System at 25.4 km/s would reach the star 37,000 years from now, just as it passes its nearest point. For comparison, Voyager 1 is traveling at 16.6 km/s. Voyager 2 is not aimed at any particular star, but in roughly 42,000 years it will pass Ross 248 at a distance of 1.7 light-years.
- Distance from earth
- 10.30 light-years (3.16 parsecs)
- Constellation
- Andromeda
- Spectral class
- M6 V
- Mass
- 14% of the Sun's mass
- Radius
- 19% of the Sun's radius
- Luminosity
- 0.2% of the Sun's luminosity
- Visual magnitude range
- 12.23 to 12.34
Lore & Background
Ross 248 was first catalogued by Frank Elmore Ross in 1926 with his second list of proper-motion stars. It was too dim to be included in the Hipparcos survey. This star has about 14% of the Sun's mass and 19% of the Sun's radius, but only 0.2% of the Sun's luminosity. It has a stellar classification of M6 V, which indicates it is a type of main-sequence star known as a red dwarf. This is a chromospherically-active star. With high probability, there appears to be a long-term cycle of variability with a period of 4.2 years. This variability causes the star to range in visual magnitude from 12.23 to 12.34. In 1950, this became the first star to have a small variation in magnitude attributed to spots on its photosphere as it rotates, a class known as BY Draconis variables.
Examining the proper motion of Ross 248 has found no evidence of a brown dwarf or stellar companion orbiting between 100–1,400 AU, and other unsuccessful searches have been attempted using both the Hubble Space Telescope Wide Field Planetary Camera and by near-infrared speckle interferometry. Long-term observations by the Sproul Observatory show no astrometric perturbations by any unseen companion. The space velocity components of this star in the galactic coordinate system are [U, V, W] = [−32.9±0.7, −74.3±1.3, 0.0±1.4] km/s. The trajectory of Ross 248 will bring it closer to the Solar System.
Reader's Guide
Ross 248 is significant as a nearby red dwarf that exhibits variability due to starspots, making it the prototype of the BY Draconis variable class. Its predicted future approach to the Solar System—becoming the closest star for about 9,000 years within the next 80,000 years—highlights its dynamic role in the local stellar neighborhood. The star's proximity and chromospheric activity make it a target for studies of low-mass stellar evolution and magnetic activity. Searches for companions have been negative, suggesting it is a solitary star. Its legacy includes being one of the first stars where photospheric spots were detected via brightness variations, and its trajectory will bring Voyager 2 within 1.7 light-years in roughly 42,000 years. The star's closest stellar neighbors are the binary systems Groombridge 34, at 1.8 light-years away, and Kruger 60, at 4.5 light-years.
Did You Know?
- In 1950, it became the first star to have magnitude variation attributed to spots on its photosphere, defining the BY Draconis variable class.
- Within the next 80,000 years, Ross 248 is predicted to be the nearest star to the Sun for around 9,000 years.
- Voyager 2 will pass within 1.7 light-years of Ross 248 in roughly 42,000 years.
More in Variable Stars, Part 2 1-24
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