IN THE NEWS AMATEUR ASTRONOMER IMAGES EXTRASOLAR PLANETARY DISC Just when you thought that amateur astronomy could not compete with the pros, a fellow amateur astronomer Rolf Olsen in New Zealand has been able to catch glimpses of a exoplanet system debris around β– Pictoris. In the 1980s an Infrared orbiting observatory called IRAS discovered this disc orbiting β-Pictoris which was later thought to be a planet forming region. Now for the first time ,this disc has been captured in visible light. What Rolf did was pretty simple. He took a bunch of pictures of β-Pictoris (in the southern constellation Pictor), and then a bunch of pictures of α-Pictoris. Then using image processing software he subtracted the two images thus blocking out the overwhelming brightness of the star. It was important that the two stars that were subtracted have to be similar, or the subtraction will not be complete. This method is not what astronomers typically use for exoplanet detection. Typically
Photo © 2011 Rolf W. Olsen. Used with permission The picture above shows the protoplanetary disc around β-Pictoris. The glare from this star is subtracted to reveal the disc. For comparison see the IR image in the inset. (L. D Etangs et. al, 1993 )
exoplanets can be detected using photometry, where a eclipsing planet would cause a periodic dip in the star’s brightness. A second, but more direct approach is to use interferometry. Light from two telescopes can be combined optically to remove the bright starlight. This is what observatories like the W. M. Keck observatory in Hawaii do. The thing to keep in mind is that Rolf did not do this using sophisticated equipment. The picture you see here was produced using a 10 inch truss Dobsonian! On behalf of the AAAD, I would like to congratulate Rolf on this achievement!