Brown dwarfs, white dwarfs and other dark matters

My research interests are primarily concerned with very low luminosity degenerate stars: brown dwarfs and white dwarfs. It is only relatively recently that telescopes/instruments and observing techniques have become powerful enough to detect these objects. Ultimately, the goal of my research is to determine the contribution that such stars make to missing mass problems in astronomy.

Recently, I discovered a new very cool white dwarf in the constellation of Taurus. This object has been subsequently shown to be one of the coolest and therefore oldest white dwarfs ever found, and has been shown to be a member of a hitherto unobserved and possibly large population of faint stars in the Galactic Halo. The existence of such a population could partially explain the nature of dark matter in the halo our Galaxy.

The object, named WD0346+246, was serendipitously discovered as a faint, very fast moving star on a sequence of photographic plates. These plates, taken with the UK Schmidt Telescope in Australia and digitised with our local precision plate scanning machine SuperCOSMOS , showed that the object was traversing the sky at 1.3 arcseconds per year, which is much faster than the majority of the Sun's neighbours. This high apparent velocity is a characteristic of halo stars which are very old and are traveling on inclined elliptical orbits around the Galaxy.

These images are digitised scans of photographic plates showing the motion of WD0346+246 over 43 years. The epochs of the three images are (from left to right) 1951.91, 1987.92 and 1994.99. The first image uses the Red (0.7 microns) passband, while the last two are in the I (0.8 microns) passband.