Christopher J. Burrows
← All work

Coronagraphy and exoplanet imaging · 1986–96

Beta Pictoris

First multicolour images of the disk, and the Hubble discovery of its warp, the first sign of a planet.

The β Pictoris disk with WFPC2, January 1995; the false-colour panel shows the inner disk tilted from the outer disk. Credit: Chris Burrows (STScI/ESA), J. Krist, the WFPC2 IDT and NASA.
The β Pictoris disk with WFPC2, January 1995; the false-colour panel shows the inner disk tilted from the outer disk. Credit: Chris Burrows (STScI/ESA), J. Krist, the WFPC2 IDT and NASA.
Ground
ESO 2.2 m, La Silla, with a coronagraph designed with Anatole Evzerov
Colour result
Paresce & Burrows 1987, ApJ 319, L23
Hubble
WFPC2 Planetary Camera, January 1995; four filters, four roll angles
Announced
AAS 187, San Antonio, 17 January 1996
Planet
β Pictoris b imaged by Lagrange et al. (VLT), announced 2008, confirmed 2010

The disk around β Pictoris was first imaged by Brad Smith and Richard Terrile in 1984. Chris and Francesco Paresce followed with the first multicolour images, using a coronagraph Chris designed with Anatole Evzerov, a former engineer on the main stellar spectrograph of the Soviet 6-metre BTA telescope, on the ESO 2.2-metre telescope at La Silla. Imaging between 5 and 15 arcseconds from the star in B, V, R and I, they found the disk has the same colour as the star. Interstellar-type dust would scatter blue light preferentially; a neutral colour means the scattering particles are much larger than a micron.

With Pawel Artymowicz they combined the coronagraph images with IRAS far-infrared data in a model where the same grains produce both the scattered light and the thermal emission, constraining the disk's tilt, optical depth, grain size and albedo, and inferring a central void within 10 to 20 AU.

Modelling the disk's scattered light and its absorption of starlight also led Chris to estimate the distance to β Pictoris at about 20 parsecs, rather than the 16 parsecs then commonly used. Hipparcos later measured 19.3 parsecs.

Chris then imaged the disk with Hubble's WFPC2 Planetary Camera in January 1995, as part of the WFPC2 Investigation Definition Team programme, at four roll angles in four filters. The images reached in to about 1.5 arcseconds from the star and showed a relatively clear zone inside 40 AU and, for the first time, a warp in the inner disk: the innermost part orbits in a plane tilted to the rest of the disk. Dynamical simulations showed such a warp would flatten within about a million years, far shorter than the age of the star, so something must be maintaining it. He concluded that at least one massive companion on an inclined orbit was responsible, and estimated it at one-twentieth to twenty Jupiter masses, orbiting within about 1 to 30 AU, inclined about three degrees to the outer disk; at Jupiter's distance it would have about Jupiter's mass.

He presented the result at the American Astronomical Society meeting in San Antonio on 17 January 1996, the same meeting at which Geoff Marcy and Paul Butler announced the planets of 70 Virginis and 47 Ursae Majoris, found by the radial-velocity method a few months after Michel Mayor and Didier Queloz reported 51 Pegasi b. In 1997 Mouillet and colleagues showed quantitatively that a planet on an inclined orbit explains the warp. The planet itself, β Pictoris b, was imaged directly by Anne-Marie Lagrange's team at the VLT, announced in 2008 and confirmed in 2010: a body of roughly nine Jupiter masses about 9 AU from the star, within the range the warp implied.

We were surprised to find that the innermost region of the disk is orbiting in a different plane from the rest of the disk. — Chris Burrows, NASA release, 17 January 1996

Press and media

From the archive

Papers

← HH 30 disk and jetESO coronagraph →