Wolf 1055 AB / Van Biesbroeck's Star

The high proper motion of Star A was first discovered in 1919 by Max (Maximilian Franz Joseph Cornelius) Wolf (1863-1932), a pioneer of astrophotography who discovered hundreds of variable stars and asteroids, and about 5,000 nebulae by analyzing photographic plates and developing the "dry plate" in 1880 and the "blink comparator" in 1900 with the Carl Zeiss optics company in Jena, Germany. Star A's high proper motion was later rediscovered by by Frank Elmore Ross (1874-1960), who reported on the star in April of 1927 with his "Fifth List of New Proper-Motion Stars," Astronomical Journal (37:886). However, many astronomers now refer to this system as Gliese 752, its designation in the famous Gliese Catalogue of Nearby Stars (CNS, now ARICNS database) of Wilhelm Gliese (1915-93). Gliese was a longtime astronomer at the Astronomiches Rechen-Institut at Heidelberg -- even when it was at Berlin.

Wolf 1055 A

This cool and dim, main sequence red dwarf (M3.5 Vne) may have about 48 percent of Sol's mass, 54.2 percent of its diameter, and less than 0.2 percent of its visual luminosity (Linsky et al, 1995). Wolf 1055 A and its companion Van Biesbroeck's Star have a combined mass of over half of Sol's but less than 11/100,000th of its brightness. In 1942, the two stars were separated by about 434 AUs -- 73.8", 151.5d, in 1942.3 (George van Biesbroeck, 1951; and 1944). As a flare star, Star A has been given the variable star designation V1428 Aquilae. Some useful star catalogue numbers are: V1428 Aql, Gl 752 A, Hip 94761, HD 180617, BD+04 4048, G 22-22, G 142-24, LHS 473, LFT 1466, LTT 15645, Vys/McC 65 A, and Ross 652.

Arnold O. Benz, Institute of Astronomy, ETH Zurich

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

Wolf 1055 AB are flare stars, like UV Ceti (L 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.

Van Biesbroeck's Star (Wolf 1055 B)

This often even dimmer, main sequence red dwarf star (M8 Ve) may have only around nine percent of Sol's mass, 10.2 percent of its diameter (around the size of Jupiter), and less than 11/10,000,00th of its visual luminosity (Linsky et al, 1995). This very cool M dwarf has an interior temperature of only about 2,700° K -- or 2,400° C or 4,400° F (Schweitzer et al, 1996). As a flare star, Star B has been given the variable star designations V1298 Aquilae and CSV 102917. Useful catalogue numbers include: V1298 Aql, Gl 752 B, BD+04 4048 B, LHS 474, LTT 15646, LFT 1467, Ross 652 B, Wolf 1055 B, Vys/McC 65 B, and VB 10.

On October 12, 1994, a team of astronomers used the Hubble Space Telescope's Goddard High Resolution Spectrograph to make a one-hour long exposure of Van Biesbroeck's Star (VB 10). In the last five minutes of the exposure, a flare with flared with bright far-ultraviolet emission was detected. Although the star's normal surface temperature is 4,500° F, the sudden burst heated VB 10's outer atmosphere to around 270,000° F. The astronomers attributed this rapid heating to the presence of an intense, but unstable, magnetic field (Linsky et al, 1995). Subsequently, an x-ray flare was detected from the star (Fleming et al, 2000).

Jeffrey L. Linsky, JILA, STScI, NASA


Larger image.


Van Biesbroeck's Star
(Gliese 752 B) has less
than 20 percent of Sol's
mass and so can
transport core heat
through convection only,
unlike its larger and
brighter companion
Gliese 752 A (more).

Powerful magnetic fields might exist around the lowest mass stars, which are near the ignition threshold for hydrogen burning at their cores. Stellar flares are caused by intense, twisted magnetic fields that accelerate and contain gases which are much hotter than a star's surface. Since VB 10 is nearly a brown dwarf, it is likely brown dwarfs also have strong magnetic fields (like LP 944-20).

Hunt for Substellar Companions

The distance from Wolf 1055 A where an Earth-type planet would be comfortable with liquid water is less than 0.084 AU (without accounting for infrared heating), with a "year" of less than 14 days. For Van Biesbroeck's Star, the orbital distance would be 0.0017 AUs (again, without accounting for infrared heating), and a planetary orbit around the star would be completed in a matter of hours. At that distance, the rotation of the planet would probably be tidally locked with the star so that one side would have perpetual daylight while the other would be in darkness. Astronomers would find it very difficult to detect using present methods.