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.

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

How the Moon Was Sculpted (Part One)

We all look up to the Moon as one of the greatest works of art in the night sky. It inspires thoughts that are greater than most of our day-to-day concerns. And the interest arises at all ages: from the 2 year old who squeals with glee at spotting the Moon to the grandparent whose sight of it may inspire somehow a hope for a better future. We have even been there, and walked on that alien land. So where did it come from? The origin of the Moon is a topic of active debate. We used to be taught that the Moon came about as a result of an impact with a large asteroid. The story goes that an impactor striking Earth at a glancing blow can drag off enough of its outer mantle to explain its size and stable orbit. The story goes on to say that if this all happened very early on in Earth’s history, when … Continue reading

The Venus Smiley Emoji

Images from the Japanese satellite Akatsuki show a spectacular arc-shaped cloud feature on Venus reminiscent of a giant (6000-mile long) sideways smiley face. Interestingly, this “smiley emoji” feature was stable for a full four days, so what was it? Let us start by reviewing what we know about Venus’ atmosphere. The inner atmosphere extends for about 12 miles above the surface and is extremely thick. If you were to try to walk through it, assuming you had a sturdy astronaut suit capable of sustaining acid rain, then you would face an atmospheric density equivalent to about one-sixth that of water. On the surface the winds would be fair, clocking in at 2-3 miles per hour. The winds would then rise up to a hurricane levels of about 200 miles per hour or even faster at higher altitudes. The winds move so fast that they typically circumnavigate the planet once every 4 days (compared to the more sluggish rotation period of … Continue reading

Dr. Dark Matter

We lost a luminary by the name of Professor Vera Rubin on December 25th, 2016. This gives us the motive to reflect on the many ways in which this person has enriched science as well as society. Dr. Rubin made the startling discovery that galaxies are put together such that the stars in the outskirts rotate with the same speeds as the stars closer to their centers. Translated, the implication is that there is a significant amount of matter that we cannot see in the outer parts of galaxies. The stars motion is changed by this unseen material, so we see its presence only by indirect methods. We call this mysterious material Dark Matter. This was one of the outstanding discoveries of the 20th century, one which many argue is sufficient to have merited a Nobel Prize in Physics. From all the information I have, she has handled her great scientific success with confidence and grace. This makes her a … Continue reading

Starshade (Part Two)

Here we are at the end of the year 2016, having discovered in total thousands of exosolar planets. The next question to ask is, “Which ones may contain life?” Will we one day detect a biomarker in the atmosphere of an exoplanet say in the form of oxygen or even ozone? Perhaps, yet the first step to finding life on other planets is to visualize the planets. This turns out to be quite hard. To date nearly all discoveries of exoplanets are indirect. That is to say, we see the effect of the orbiting exoplanet(s) on the star, and yet unfortunately we cannot point to the planet itself. There have been many recent breakthroughs in a field of astronomical imaging called “adaptive optics” that enable some of the first direct imaging of exoplanets. Even so, it is painstaking work. Astronomer Sara Seager at M. I. T. leads a new effort to make it easier to see the exoplanets named “starshade.” … Continue reading