Dr. Brenda Frye

About Dr. Brenda Frye

Brenda L. Frye is an observational cosmologist at the Department of Astronomy/Steward Observatory, University of Arizona. She earned her Ph. D. in Astrophysics from the University of California at Berkeley, assisted by a National Science Foundation Graduate Research Fellowship.

Her thesis work involved measuring the concentration of the total mass of visible plus dark matter in the fields of massive galaxy clusters, a program requiring the use of some of the largest telescopes in the world.

Moving a mile from her Ph. D. institution, she assumed a postdoctoral position with the Supernova Cosmology Project at Lawrence Berkeley National Laboratory under the direction of Professor Saul Permutter.

She then treked across the country to take a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship and a Princeton Council on Sciences and Technology Fellowship both at Princeton University.

Moving further east, she became a Lecturer in Physics at Dublin City University in Dublin, Ireland, where a number of European collaborations were formed.

From there she crossed back across the pond to the west coast of the U. S. to become a tenure-track Assistant Professor of Physics at the University of San Francisco.

Her travels have now landed her at her Alma Mater in Tucson, where she teaches and does research. The aims of her research continue to be to use gravitational telescopes in space as 'lenses' to study the properties of dark matter and those of distant galaxies back to when the universe was <900 million years old.

Getting Baby Stars to “Dohsey-doh” Well with Others

One hundred billion stars whirl about each other and, collectively, around the Galaxy, yet rarely do they ever collide. This is because stars are much more likely to interact with each other the way people do in a square dance: namely, by approaching one’s partner, linking arms while skipping in a full circle ’dosey-doh,’ and then making a retreat. One tries to avoid the full-on collision to preserve the health of one’s partners. Stars interact similarly to well-trained square dancers, by exchanging momentum with the partner star. The two stars approach, describe a circular ‘dosey-doh,’ and then move away. Having said that, every so often two stars find themselves on a path to a direct collision. This event is so unlikely, and so short-lived, that astronomers do not often get the opportunity to see it. One of the best chances to look for such an unfortunate activity is in stellar nurseries called molecular clouds. This is because stars are born … Continue reading

Punting Black Holes

As summer approaches, we can see examples of punting in more than just local playing fields. In addition to balls being punted halfway across a field, it looks more and more like 6 billion solar mass black holes can also be punted to vast distances across a galaxy. Now black holes are, as the name implies, completely black. The good news is that they can be spotted anyway for the cases in which the surrounding gas or even stars get too close to the black hole and start funneling onto it. In such cases the black hole can become piercingly bright. In fact the black hole is so bright that there is too much glare to see the fainter galaxy underlying it. Recently, astronomers have found a way to block out this extra glare from the ultra-bright supermassive black hole. Somewhat surprisingly, in a couple of cases a considerable offset is measured in the center of the galaxy compared to … Continue reading

The Other Feynman

We have all heard of Rychard Feynman, who was famous for doing fundamental work in the areas of particle physics and in quantum mechanics which led to a Nobel Prize in physics. What is perhaps less well-known is that he also had a sister who was a reknowned physicist. According to an article in Popular Science this month, Dr. Joan Feynman started her career in 1932 when she was 5 years old. At that time she was set to turn switches to help her brother Rychard Feynman do physics experiments in their backyard. As a teenager, she recalls being inspired by reading about the work of Cecilia Payne-Gaposhkin in an Astronomy textbook. As Joan put it, “When I came to page 407 it changed my life.” For it was at this time that she realized almost as if in a revelation that women can do science! Joan Feynman graduated from Oberlin College with a B. S. in physics in 1948. … Continue reading

Spring cleaning in the Early Universe

This is yet another installment on dust. Thanks to observations with the mighty Atacama Large Millimeter/submillimeter Array, or ALMA, a radio telescope in Chile, we can now view this humble material at a distance of 13.2 billion light years away. This is interesting as we think the universe is only 13.7 billion years old. If we turn the clock all the way back to just before there were any stars, we would find a universe made up of hydrogen, helium, and the slightest amount of lithium. If we now fast-forward to the time when the stars turned on in the universe for the first time, we expect for many of them to make enormous amounts of carbon, silicon and aluminum which combine together with hydrogen to make dust. Yes, we think it is thanks to stars that we have any dust at all. What is missing is finding those (close to the) first stars in that (close to the) first … Continue reading

The Most Recent Chapter on the Hubble Constant

Astronomers agree that the universe is expanding in all directions, a notion now called the “Hubble expansion” to refer discoverer Mr. Edwin Hubble. A useful analogy to understand the Hubble expansion is to draw dots onto a balloon to represent galaxies in the universe. As you blow up the balloon the dots expand away from each other. While there seems to be no way around a universal Hubble expansion, now there is controversy brewing regarding the exact value for this rate of expansion. What is at stake may be a tiny misunderstanding in how we make the measurements, or may be a signal of new physics. Oh, we all agree now on the approximate answer, that the space between galaxies grows such that for every 3.3 million light years a galaxy moves in distance away from us, the velocity of that distant galaxy becomes 70 km/s faster. Equivalently, in astronomer’s jargon we say that the rate of expansion (H0) equals … Continue reading

Learning from a Flashlight in the Sky

While many of us are dazzled by the spectacular examples of galaxies each one with its own 10-100 billion stars, some of us choose instead to study the regions between the galaxies. There is a fair amount of hydrogen gas in this “intergalactic medium,” yet this gas typically is too faint to see directly in images. We are able to study this dim gas only by looking at how it affects the light coming from bright objects in the background called quasars. There are a great many bright quasars, or galaxies with extremely bright nuclei, in the universe. These quasars each produce a tremendous amount of light much like the welcome sight of a flashlight on an otherwise dark and deserted hiking trail. Indeed if you were to look at the flashlight of a distant hiker during an evening walk, you may see the flashlight seem to ‘flicker’ not because the battery was running out but rather as a result … Continue reading

Smile Black Hole – You’re on Camera (Part Two)

Who wouldn’t dream of seeing a black hole up close (but not too close)? In this second article we will take a look at the advances in technology that allow us to view the black hole at the center of the Milky Way. First, we should understand the obstacles. As we are situated in a disk galaxy, there are large numbers of stars situated exactly in between us and the Galaxy’s center. This introduces a kind of ‘light pollution’ in the form of starlight which interferes with our ability to see faint emission emanating from the accretion disk surrounding the black hole. This is analogous to watching a friend holding a piercingly-bright flash light on a dark path. You see the flashlight but not the physical features of your friend who you know must be holding the light. By choosing the color The Milky Way’s central supermassive black hole carefully, we are able to view the black hole at a … Continue reading

Smile Black Hole – You’re on Camera!

Black holes are notoriously difficult to catch on camera. They are completely dark objects that consume unsuspecting objects that get too close.. Just before stars and gas fall into black holes they spiral around and around as if caught in a whirlpool. They emit a great deal of light as a sort of “last hurrah” as they are torn apart en route within the black hole surface, or event horizon. This light is evidence that a star was recently there. It also means that when black holes are consuming stars they are not entirely black. The dark center is surrounded by a ring of light. That is how the story goes, anyway. We are quite (but not completely) sure that black holes exist. There is a great deal of circumstantial evidence to support this mathematical solution first proposed by Karl Schwarzschild in the early 20th century. One detail missing is that we have never actually seen one. We need verification. … Continue reading

Giant Elliptical Galaxies

Our own Milky Way is huge at 100,000 light years across, yet is dwarfed by the so-called giant elliptical galaxy which can be up to ten times its size. Giant ellipticals are the biggest galaxy type of them all. Curiously, giant ellipticals are always situated in the denser regions of space. They are framed by up to hundreds of other galaxies. Each one of these other galaxies has its own 10-100 billion stars replete also with star forming gas and a supermassive black hole. As the giant elliptical is so massive and thus has stronger gravity, these other smaller galaxies fall in toward the giant elliptical. Like some bad science fiction movie about a “blob,” the giant elliptical has a chance to grow by cannibalizing its smaller galaxy neighbors. The giant elliptical tears apart each nearby galaxy, separating out the stars from the gas, the dense nucleus, and the supermassive black hole. Interestingly, the supermassive black hole is thought to … Continue reading

A Milky Way “Seed” Discovered?

It is well known that our Milky Way galaxy has a spiral shape. Perhaps it is less well-known that the Milky Way is surrounded by about 150 dense star clusters. To picture this better, if we imagine that a beehive is the Milky Way galaxy, then the bees orbiting the beehive in all directions would be the dense star clusters. It was in the year 1919 that Harlow Shapley counted these star clusters, also known as globular clusters. Interestingly, he found that there were about twice as many stars in one direction compared to the anti-direction, from which he inferred that the Sun + Earth system lies about two-thirds of the way out from the center. This resulted in a shift in our philosophical outlook, for with this one exercise humans were humbled out of their assumed ‘central’ placement in our own galaxy. A new use for globular clusters is discussed in this week’s issue of Nature magazine. In this … Continue reading

Wimpy Gravity

One great unsolved question in physics is why gravity is so weak compared to the other three forces of nature? This fact is not intuitive at all to many of my students whose experience gravity is that it is ever present, unforgiving, and at times brutal. The Earth is huge, and acts unrelentlessly to pull us towards its center. This lack of an ability to jump even 3 feet in the air, or for the best athlete in the world to jump 8 feet in the air (Mr. Javier Sotomayor), makes us respect this downward-pulling force. What we perhaps take for granted is that we also do not actually sink towards the center of the Earth, as the Earth would have it. Instead, the electrons in our skin, or in the soles of our shoes, repulse the electrons in the ground. We triumphantly stand firmly on the surface of the Earth. In this same vein, we can also take a … Continue reading

How the Moon Was Sculpted (Part Two)

In the last entry we reviewed the debate currently swirling around the question of how the moon formed. Lunar soil samples brought back from Apollo astronauts show compositions extremely similar to that of Earth, making the standard lore less attractive that a single giant impact striking at a glancing blow produced the Moon. In the formation scenario presented last time, the Moon was formed as a result of series of smaller impacts. According to the simulations, such a series of events would take a long time to play out. In this case, the Moon’s birth certificate would state it to be about 100 million years younger than the Earth. We can test this hypothesis by going out and measuring the ages of each body. Unfortunately, such age-dating measurements do not help us, as some results show a difference in formation age of 100 million years while others put the Moon at a more contemporaneous difference of only tens of millions … Continue reading