BETA PIC (Beta Pictoris). Magnificent stars can come in obscure constellations, a fine case in point the Beta star of the small constellation of Pictor, the Easel, which lies just to the west of Canopus in Carina, the Keel of Argo. To the eye, it appears as a common class A (A5, though some put it as hot as A3) hydrogen-fusing dwarf. At a distance of 63 light years, it radiates at a modest rate of 8.6 times that of the Sun from its 8250 Kelvin surface. The combination of the two give a radius of just 1.4 times solar and a mass near 1.7 solar. Spinning rather quickly, with an equatorial velocity of 130 kilometers per second (65 times that of the Sun), the star completes a rotation every 0.54 days, its metal abundance close to solar. Beta Pic is among a small handful of seemingly ordinary class A stars that through satellite observation in the early 1980s were found to shine strongly, and anomalously, at infrared wavelengths (others being Vega and Fomalhaut), which indicates radiation coming to us from a circumstellar cloud of warm dust. Careful observations from the ground reveal that Beta Pic's cloud is in the form of a magnificent edge-on disk that stretches 400 Astronomical Units away from the star in each direction, 10 times the average distance of Pluto from the Sun. Though nowhere near as thick, our own Sun has such a dusty disk too, made up of comet debris, the remains of colliding broken asteroids, and the stuff in the "Kuiper Belt," a region of small bodies that includes Pluto and that extends to some 50 or more AU from Solar System's Center. The immediate implication is that Beta Pic may have planets of its own buried within the disk. While there is no direct evidence of such planets (as there is for some 100 other stars), indirect evidence is provided by the Hubble Space Telescope, which records a warping of the disk that might be caused by a giant planet's gravity. A central "hole" that is partially cleared of dust is equally intriguing. Still in its infancy, only 10 to 100 million years old, Beta Pic may still be building its family. Alas, such stars do not live very long lives, disallowing the development of the kind of life we have on our Earth -- providing that Beta Pic indeed has any real planets at all. Read more about Beta Pic in Jim Kaler's Hundred Greatest Stars.

A planet! A probable giant planet seems to have been imaged inside the dust disk at a separation of about 8 Astronomical Units from the star. From its infrared brightness, Beta Pic b should have a mass of around 8 times that of the Jupiter. Orbital motion has not yet been seen. There is a speculation that this planet may have caused a transit event in 1981. The planet still needs confirmation.
Written by Jim Kaler 3/26/04; addition 7/03/09. Return to STARS.