Beta Pictoris

Beta Pictoris (β Pic, β Pictoris) is a main sequence star in the constellation of Pictor.^[5] The star system is notable for possessing a large disk of material, in which planets might be located. A planet, named Beta Pictoris b, was observed in 2008 using ESO's NACO instrument on the Very Large Telescope (VLT).^[7] It is unusual as it is one of the few planets outside our Solar System that has been observed through direct imaging. It is also the planet closest to its star to have been seen with direct imaging and whose movement has seen over time.^[8] Being a fourth magnitude star, Beta Pictoris is fairly bright and can be seen with the unaided eye in the Southern hemisphere.

Properties and structure[edit]

Situated 63 light years away, the star is the second brightest in the constellation of Pictor, as seen from Earth.^[5] The star is thought to have a mass of 1.75 solar masses and a luminosity 8.7 times larger than that of the Sun.^[4] It is thought to be composed of 70% hydrogen, 28% helium and 2% elements heavier than helium.^[4] The surface temperature of Beta Picoris is estimated to be 8,200 kelvin. The spectra of the star is variable, with many transient features.

In the 1983 observations made by the IRAS satellite, it was noticed the star emitted strongly in the infrared portion of the electromagnetic spectrum.^[4] Optical images then showed a needle-like nebulosity around the star. It was later found through closer observations to be a huge disk a gas and dust surrounding the star, with a width of roughly 2,000 Astronomical Units (2,000 times the distance between the Earth and the Sun).^[5] The orientation of the disk is such that it is viewed edge-on from Earth. Observations performed by the Hubble Space Telescope have shown the disk is "warped" vertically near the star, at a radius of 50 AU.^[4] The outer parts show rings, possibly due to other, unseen planets.

Beta Pictoris b[edit]

In 2008, a member of the NACO team at ESO decided to re-analyze data produced since 2003, searching for anything that might indicate the presence of a planet.^[9] A planet, designated Beta Pictoris b, was found and early measurements suggested it had a mass 8 times that of Jupiter and orbited the star at a distance of 8 AU.^[9] The planet was found to lie in the same plane as the disk, suggesting the disk and star really are related, and don't just happen to lie along the same line of sight.

More recent observations place its mass at 11±2 that of Jupiter.^[10] Its thought to have an orbital period of 22 years.^[11] The planet is a gas giant and very hot, estimated at 1,200 kelvin (2,700 degrees Fahrenheit).^[7]

Beta Pictoris b is the only known planet orbiting Beta Pictoris. Since the plane of the system is edge on to Earth, is very suitable for making observations of transits, whereby objects pass in front of the star. As of April 2019, no more planets have been observed.^[12] It is hoped that Beta Pictoris b will transit the star at some point and allow its properties to be measured in more detail. There is a tantalizing hint that it will as there was an unexplained dip in the brightness of the star in 1991, now thought to have been a transit by Beta Pictoris b.^[7] If it does transit, it is though the so-called "Hill sphere" will also transit. The "Hill sphere" is the sphere of gravitational influence of an object and includes and gas, dust and debris that the planet might carry along with it. If this is the case, the transit could last for several months.

See also[edit]

• Exoplanets

External links[edit]

• Images of Beta Pictoris b being obscured by its star and reappearing

References[edit]