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.
The images of many different kinds of galaxies were created using observations from the Spitzer SINGS survey and the Herschel KINGFISH survey. From http://www.astro.umd.edu/~rhc/bigbang/boxed/research_blog.html.
For today’s astronomy seminar, we had Rodrigo Herrera from University of Maryland Astronomy. Rodrigo spoke about using far infrared observations from the Herschel instrument to study star formation in nearby galaxies.
Rodrigo talked about using emission at 158 microns, created by ionized carbon atoms (CII), to probe the rates of star formation. The hottest and youngest stars in a stellar nursery, O and B stars, are thought to heat dust grains, charging them slightly. The resulting excess electrons then escape into the gas surrounding the stellar nursery, heating it. Some of that gas is ionized carbon, which cools by emitting photons at a very specific wavelength, 158 microns.
By observing how much 158-micron emission is coming from a galaxy (and applying some important corrections to account for the variation in the physical environments in each star-forming region), Rodrigo showed that astronomers could pretty accurately estimate the rate at which stars are forming throughout that galaxy.
Understanding the star formation rate is important for may aspects of astronomy, but in particular, the star formation rate is a key parameter for the Drake equation, which estimates the number of intelligent and communicating civilizations in the universe. Such civilizations probably grow up orbiting a star similar to the Sun, so knowing how often such stars form goes a long way to telling us how many extraterrestrial civilizations might be out there.
Relative strengths of known diffuse interstellar bands. From http://en.wikipedia.org/wiki/File:Diffuse_Interstellar_Bands.gif.
We had a great talk today from Dr. Gail Zasowski of Johns Hopkins University Astronomy. She talked about mysterious spectral features called diffuse interstellar bands (or DIBS).
Illustrated at left, DIBs are spectral absorption features that pop up when astronomers point their telescopes in almost any direction in the sky. The DIBs are probably created by some type of molecule (or molecules) that abounds throughout our galaxy, but astronomers and astrochemists haven’t figure out what it is yet, even after decades of work.
Dr. Zasowski described how the DIBs could be identified in the vast collection of spectra from the APOGEE project and then used to map structure in the Milky Way. It goes to show that, just because we don’t know what exactly we’re looking at, it doesn’t mean astronomers can’t use the information to learn about the universe.
NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, has captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light. Taken from wikipedia.
Dr. Daniel Wik visited DTM this morning to give a talk about NASA’s NuSTAR mission, an X-ray telescope in low-Earth orbit designed to study some of the most exotic and energetic phenomena in the universe.
For example, the image at left shows observations taken by NuSTAR of the center of our galaxy. In recent years, astronomers have learned that a supermassive blackhole looms at the center of our galaxy, gobbling up gas.
The images at left show a flare bursting from the galactic center, made of gas heated to 180 million degrees Fahrenheit (100 million degrees Celsius) as the black hole sucked material down into its deep, dark center.