Model (top) and observed (bottom) infrared images of the debris disk around HD 15115. From Rodigas+ (2012).

Great talk today in the astronomy seminar from our own Dr. Timothy Rodigas.

Dr. Rodigas talked about several topics related to debris disks around stars. The colors and shapes of these disks can tell us about the compositions of planet-forming materials around the host stars and about the possible presence of otherwise unseen planets.

Without any planets in the system, debris disks are thought to take on very simple shapes, so if an astronomer finds a disk that warped or asymmetric, that can be evidence for a planet gravitationally sculpting the disk.

Dr. Rodigas presented the results of theoretical calculations that showed how the width of a sculpted debris disk can be used to put an upper limit on the mass of a planetary companion — very useful if you’re an astronomer trying to decide where to look for planets.

Great talk today from Dr. Karl Gordon of the Space Telescope Science Institute (STScI) on mapping interstellar dust in the Milky Way and other galaxies.

Full sky images of dust in the Milky Way from the Pioneer 10/11 IPP data. From http://www.stsci.edu/~kgordon/pioneer_ipp/Pioneer_10_11_IPP.html.

Dr. Gordon spoke about using observations taken at infrared wavelengths to look for heat radiated by dust grains and then using those measurements to determine how hot the dust is and how much there is. The picture at right shows a map of dust in the Milky Way from one of Dr. Gordon’s papers.

Understanding the dust distributed throughout the Milky Way and other galaxies can tell us a lot about stellar evolution, the galaxies themselves, and about the conditions in those galaxies where the dust lives. And at the most fundamental level, it tells us about the planets and even life itself because the Earth and everything on it formed from this star dust.

Geometry of the mutual occultations of Sila and Nunam (called “mutual events”) over the last few years. From http://www2.lowell.edu/users/grundy/abstracts/figs/2012.Sila-Nunam.gif.

Interesting talk today in the DTM Astronomy Seminar from Dr. Anne Verbiscer of UVA Astronomy.

She spoke about the Kuiper Belt binary object Sila-Nunam, two enigmatic bodies orbiting 40 times farther from the Sun than the Earth. They have radii of about 100 km, comparable to some of Saturn’s small moons, and they orbit one another every 12 days, as they both go around the Sun together every 300 years.

In recent and coming years, Sila and Nunam will occult one another several times, allowing astronomers to measure their radii, which aren’t very well known, and learn about their densities, internal structures, and orbit.

Dr. Verbiscer presented several very interesting infrared spectra and observations in visible wavelengths, showing the small dips in light from the system, as one object blocked out the other object. These observations are very challenging because objects are so small and far away, but analysis of these data are ongoing and will tell us about these strange, distant, and cold objects.