Credit: D. Looper & M. Liu |
Brown Dwarfs: Filling the Mass Range between
Planets and Stars
by Dagny Looper
Brown dwarfs are substellar objects with masses between that of normal stars
and planets. They are too small (less than about 75 times the
mass of Jupiter) to fuse hydrogen in their cores, and because they do not have a
sustainable source of energy like stars do, over time they cool and contract to
a size slightly smaller than Jupiter. While the existence of brown dwarfs
was first proposed in 1965, the first bona-fide brown dwarf was not
identified until 30 years later despite many intensive searches by the
astronomical community. The coolest known brown dwarf has a surface
temperature of only about 920° C (about 1,700° F), nearly 100° C cooler than
the surface of Venus and more than 5,000° C cooler than our Sun's surface.
Since they are so difficult to detect, the solar neighborhood could be filled
with these cool objects, but we are unable to see most of them. I will give
an overview of brown dwarfs, summarize my research in expanding the local
census, and discuss what we can learn about the cooling sequence of these
objects based on studying them in binary systems.
more on Dagny
Credit: NASA / SkyWorks Digital |
Gamma-ray Bursts by Emily Levesque
Gamma-ray bursts are the signatures of extraordinarily high-energy events
occurring throughout our universe. Some of them are the signature of the
death throes of very massive and rapidly rotating stars. The final moments
in a star's life are thought to be determined mostly by properties they
acquired at birth, such as their mass and rotation rate, but can also be affected
by the surrounding environments as the stars evolve. The particular
properties and environments that must be present for gamma-ray bursts to
occur are still a mystery. By observing galaxies where gamma-ray bursts
have occurred, we can begin to understand the formation, evolution, and
details of these enigmatic objects.
more on Emily
NASA/JPL-Caltech/C. Lonsdale (Caltech/IPAC) and the SWIRE Team |Bridging Starbursts and AGN
in the Ultra-Luminous Infrared Galaxies
by Tiantian Yuan
If you had an eye that could see light at all wavelengths, and you looked at all the galaxies in the
you'd find that the most luminous ones are those whose energy peaks in the far-infrared part of the spectrum. These galaxies are known as ultra-luminous infrared galaxies (ULIRGs).
Their high infrared luminosity is caused by the merger of gas-rich galaxies. ULIRGs
have been thought to be a transition stage between
starburst galaxies, which emit most of their light from stars, and active
galactic nuclei (AGNs), whose light is created by gas being sucked into black holes. Using a new classification scheme from the Sloan Digital Sky Survey,
we have found a class of starburst-AGN composite galaxies within the ULIRG population.
more on Tiantian
went to college at Caltech and University College London,
receiving her BSc in Astrophysics in 2004. As an undergraduate, she studied transiting extrasolar planets
with David Charbonneau and brown dwarfs with Davy Kirkpatrick. She worked as an assistant researcher at Caltech's Infrared Processing and Analysis Center for a year before coming to the Institute for Astronomy as a graduate student in 2005. Dagny is a Caltech Presidential Scholar, Mellon Mays Fellow, and Research Science Institute alumna. She and her teammates won the English Women's College Football (soccer) Cup in 2004. She is also interested in kayaking and hiking.
grew up in southeastern Massachusetts and received her bachelor's degree in physics from MIT. She is currently in her second year of graduate school at the IfA and will begin work on her Ph.D. thesis this semester. Her past research and publications have covered topics such as active galactic nuclei, galaxy environments, light element abundances in
stars, radio-astronomy-based searches for deuterium (heavy hydrogen), the
physical properties of massive stars, and the environments of gamma-ray
burst host galaxies.In her spare time she enjoys any activities that get her outdoors, particularly backpacking, skiing, rock climbing, hiking, and biking. She also enjoys writing and is currently trying to get some of her work published.
Tiantian Yuan was born in Chongqing, a city in southwest China. She received her BS from the Department of Astronomy of Beijing Normal
University in 2006 and is now a second-year graduate student at IfA. When she is not studying astronomy, Tiantian enjoys jogging and hiking. She says,
"I'm fascinated by our physical universe, and want to share what I've learned with you."
Institute for Astronomy, 2680 Woodlawn Drive, Manoa