Imagine Magazine - Johns Hopkins - September/October 2011 - (Page 26)

aMaTeUR aSTRonoMY in THe age oF aLL-SkY SURVeYS Not long ago, it was amateur astronomers who discovered all the transient events and variable stars. That has changed with the advent of large scale survey telescopes, but there is still room for young astronomers to contribute to the science of astronomy. One of the best ways to get involved is to contact astronomy faculty at your local university and see if they have any summer projects that students can work on. Finding new variable stars is a more di cult task now than 10 years ago, but many recently discovered variable stars still need to be characterized (as eclipsing binaries, for example, or pulsating variable stars). Amateur astronomers have also started to make interesting contributions through measuring stellar spectra. Spectra show the light from a star spread out by wavelength, and allow one to distinguish the temperature of, and individual elements in, a star’s atmosphere. For more information, see Sky & Telescope magazine (www.skyandtelescope. com) and the American Association of Variable Star Observers (www.aavso.org). Passing too close to a black hole, a star is torn apart by extreme tidal forces. In physics, the equations that describe, for example, the motion of a projectile through the air are easy to write down but often difficult or even impossible to solve exactly. A computer can approximate the solution by doing it in many small steps. It is relatively easy to write a program to solve an equation and then let the computer work through all the numbers. For me, writing such programs was a tool to understand solutions to real physical problems and to gain an intuition of the underlying physics. I could not only find out how far a projectile would land from where it was thrown, but also experiment with different values: How far would a tennis ball go? A basketball? What was it like to throw something through water, not air? The tools of computational physics essentially allow one to construct a virtual laboratory. And they are perfectly suited to studying astronomy, where they are the only laboratory we have to understand the physical processes that dictate the nature of stars, galaxies, and the universe as a whole. For my senior thesis, I studied the mergers of very close pairs of stellar remnants known as white dwarfs and neutron stars. Whether these mergers are gradual or rapid and violent depends on both the internal structure of the stars themselves and the ratio of their masses. Using computer simulations, I was able to recreate a variety of conditions and see which of the many possible factors were most important in determining the nature of these mergers. JAMES GUILLOCHON, UCSC Simulate, Observe, Compare I’m continuing my work in computational astrophysics as a graduate student at the University of California, Santa Cruz. Right now is an especially good time to be applying the methods of computational physics to astronomy. Observational astronomy is on the brink of a renaissance; several new allsky survey telescope facilities are either being built or starting to come on line—the Palomar Transient Factory and the Large Synoptic Survey Telescope are two examples. These telescopes will image large swaths of sky over time—and take our perception of the night sky from cartography to cinematography. With these new telescopes, I think we will see a dynamic, violent, and beautiful side to the lives of stars that we still very poorly understand. Stars live most of their lives in quiescent states, much like our sun, which can be counted on to be the same brightness day after day. But they end their lives in cataclysmic supernova explosions; in dense stellar clusters at the centers of galaxies, they can collide or be shredded by extreme tides raised by massive black holes. Merging binary stars like those I studied for my senior thesis unleash huge amounts of light. By performing computational simulations of these events, we hope to understand their frequency, observable signatures, and, most important, the interplay of physical processes that lead to, for example, the detonation of a massive star in a supernova explosion. Through an iterative process of simulating and observing new events, we can realistically hope to probe physics that is now only at the edge of our understanding—matter at extremely high temperatures and velocities, and under the influence of very strong gravitational fields. As a graduate student, my role in all of this exciting progress is a small one. Lately, I’ve been simulating close encounters between stars and black holes in the centers of galaxies. In the rare event where a star passes extremely close to the hole, it is ripped apart by tidal forces. The gas that falls back onto the black hole can glow bright enough to outshine the entire galaxy for a short time. Observers think they may have captured such a “tidal disruption flare” this past winter, but many uncertainties remain. I hope that my simulations will be able to provide some insight into such events. At the very least, I hope my work will show that the universe is a far more dynamic place than we ever realized. Morgan MacLeod grew up and went to college in Maine. He is now starting his second year as a grad student at UC Santa Cruz and has been enjoying exploring California in his spare time. 26 imagine Sept/Oct 2011 http://www.skyandtelescope.com http://www.skyandtelescope.com http://www.aavso.org

Table of Contents for the Digital Edition of Imagine Magazine - Johns Hopkins - September/October 2011

Imagine Magazine - Johns Hopkins - September/October 2011
Contents
Big Picture
In My Own Words
Physics Is…
Making the Team
Nuclear by Nature
Physics: The Next Generation
Telescopic Views
Exploring the Mysterious Lives of Stars
Around the Universe in Three Weeks
Selected Opportunities & Resources
Book Buddies
Meeting the (Economics) Challenge
Off the Shelf
Word Wise
Exploring Career Options
One Step Ahead
Planning Ahead for College
Students Review
Creative Minds Imagine
Mark Your Calendar
Knossos Games

Imagine Magazine - Johns Hopkins - September/October 2011