Prof. Alex Filippenko & Dr. Weidong Li


Supernova 1999bh

Supernova 1999bx

Supernova 1999ej

Supernova 1999gb

Supernova 2000fa

Supernova 2001L

Supernova 2001ae

Click on pictures for link to larger images and IAU CIRCULAR info at the KAIT website.

Undergraduate Senior Thesis (UC Berkeley, December 2001, Physics & Astrophysics)



Sn 2000cx

Since the Spring 1999 semester, I have been doing research in Astrophysics as a member of the Lick Observatory Supernova Search (LOSS) team under Professor Alex Filippenko. LOSS uses the multi-purpose 76 cm Katzman Automated Imaging Telescope (KAIT), to scan a sample of over 1000 galaxies per night, in search of nearby (low redshift) supernovae. As a member of the supernova search group, I use image processing software designed by Dr. Weidong Li, to analyze supernova candidates that the program draws from the sample of the previous night's images. Using various features of the software to separate the potential candidate from the light of the host galaxy, cosmic rays, asteroids, and other false alarms, undergraduates in the group such as myself determine whether a candidate should be thrown out or if it is good enough to receive a second look. If a certain image contains a good supernova candidate, we can send a request file to KAIT to re-observe the relevant host galaxy, and can sometimes even get same day confirmation. I am happy to say that I have been able to discover a total of seven Supernovae thus far. Every time we make a discovery, an e-mail called an IAU Circular is sent out to all members of the International Astronomical Union, so members of the astronomical community can be kept up to date as to the newest discoveries. Images of the supernovae I've discovered (1999bh, 1999bx, 1999ej, 1999gb, 2001fa, 2001L, and 2001ae) as well as the relevant IAU Circulars can be found by clicking on the images below or by going directly from the KAIT website http://astron.berkeley.edu/~bait/kait_lwd.html under the headings 1999, 2000, and 2001 Discoveries.

I've also recently started doing photometry, which for supernovae, is basically the idea of counting up all the photons from the erstwhile star, and seeing what you get. It is particularly useful to display what are called the supernova's light curves, which simply plot the brightness of a supernova as a function of time. We do this in several different filters U,B,V,R, and I (Ultraviolet, Blue, Red, Visible, and Infrared). The I filter, for example, lets only infrared photons through. In any case, the shapes of the light curves (along with spectra of the object) can often tell us what kind of supernova we're looking at, and as a set, the collection of light curves we have serves as a very useful tool for doing cosmology, especially in regard to using supernovae as cosmological distance indicators.

For those of you who might be interested, the big picture goal of LOSS, which is sometimes called the low Z (low redshift) supernova search, is to accumulate a sample of low redshift supernovae with which to compare to those found by the High Z supernova search, headed by Brian Schmidt. The High Z team's goal is to use Type Ia supernova as cosmological distance indicators and to probe various cosmological models. By comparing the high Z and low Z samples, we can test whether Type Ia supernovae can be used as reliabale standard candles with uniform intrinsic brightness, or whether their intrinsic brightness varies in time due to evolutionary effects. In particular, the team has endeavored to determine the expansion rate of the universe and place constraints on the value of the cosmological constant. So far the findings suggest that the universe is accelerating in its expansion and consistent with a nonzero cosmological constant, contrary to earlier cosmological models!


Undergraduate Infrared Astronomy Laboratory- Lab Reports
(Astronomy 122 - UC Berkeley, Fall 2001)

Berkeley Scientific Journal  Staff Writer/Graphic Designer (...links to articles coming soon)