A new theoretical study published in Physical Review Letters on January 24, 2018, finds that the dark matter which we famously can neither see nor touch may be so elusive owing to its slow speed. For decades astronomers have been faced with the puzzle of why the vast majority of stars in a spiral galaxy move faster than they should. The only explanation that makes sense to us is if in addition to the matter that we can see there is also a significant component of invisible matter. One good way to try to detect this so-called “dark matter” is by placing a large vat of dense material such as xenon deep below the Earth’s surface, where it is safely out of the way of terrestrial energy sources. Then, we set a “trap” which will send an alert whenever a particle consistent with a dark matter particle collides with the atoms in the vat. Unfortunately, despite careful efforts to build … Continue reading →
About Dr. Brenda Frye
Brenda L. Frye is an observational cosmologist with research interests in the area of the formation and evolution of galaxies. 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 physical properties of faint and distant galaxies which are boosted artificially in brightness by natural telescopes in space, an approach that enabled her to study galaxies when the universe was less than one billion years old.
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 Physics Nobel Prize winner Professor Saul Perlmutter. She then crossed the country to hold two consecutive postdoctoral fellowship positions at Princeton University.
She has taught physics and astronomy at the undergraduate and graduate levels at Dublin City University in Ireland, the University of San Francisco, and the University of Arizona where she is currently Associate Professor of Astronomy.
Is there gravity in space? An answer of “no” makes sense as astronauts on the International Space Station (ISS) float around within the spacecraft. At the same time, an answer of “yes” makes sense as this spaceship does orbit the Earth? What is the right way to think on this problem? To begin with, yes, there is gravity in space. The gravity we feel is caused by the attraction that all of us feel towards the center of the Earth. The relevant bit is that the gravitational force depends on the distance between the center of you and the center of the Earth. As the distance between you and the Earth increases, the gravitational force decreases. Here are some examples. If we go to the highest floor of a skyscraper, then do we feel lighter than when we are on the ground? Yes, technically we do, but the difference is too small to mention. How about the top of a … Continue reading →
Known to some as the name of the weekly lottery in Spain, “El Gordo” is synonymous to astronomers as the most massive object known in space. It has several hundred galaxies in it of 10 billion stars each plus ten times more matter in the form of dark matter, and is a prodigious producer of X-rays. Indeed it would not be safe for a galaxy to get too close to El Gordo. Not only would such a unsuspecting object suffer from the high energy radiation, but in addition there is such a powerful gravity spread out over such a large area that it will stretch incoming objects like taffy. Not to worry though – this object is about 6 billion lights years away, which equates to about half the age of the observable universe, so we are not going to encounter El Gordo anytime soon. To be fair, it is not really a single object anyway, but rather a pair … Continue reading →
When the universe was one billion years old (only 7 percent its current age), the first galaxies had already formed. These galaxies are sometimes called “building blocks” rather rather than actual full-fledged galaxies because they lacked any real recognizable organized forms. In other words, none of them took on the characteristic pinwheel or oval shapes that we see in galaxies today. It is thought that this was a wilder era in which the galaxies were so busy assembling themselves and rapidly forming stars that they were often literally bent out of shape as a result. Recently, it was reported in the January 11th, 2018 issue of Nature magazine that astronomers have found examples of galaxies in this “wild west” time period that have curiously well-behaved shapes. These newly-discovered objects take on a “pancake” morphology reminiscent of spiral galaxies. They also rotate peacefully about their centers like spiral galaxies today. At the same time, these mini-galaxies do not share all the … Continue reading →
Massive stars, by which we mean to say stars that are about thirty times the mass of the Sun or even more massive, are distinguished from their less massive brethren in several ways. These blue luminaries shine brighter, have shorter lives, create many different elements of the periodic table, end their lives famously as supernovae, and are extremely rare. A new study reported in this month’s issue of Science magazine asks us to revisit the notion that massive stars are such a minority. Massive stars, and in fact all stars, tend to form in large families in which there can be hundreds of “siblings.” In this study, 800 massive stars were observed in a large and nearby star forming nursery called the Tarantula Nebula. This is star forming region that got its name because some regions which correspond roughly to the stellar “incubation” centers trace out spindly shapes that resemble the legs of a spider. Stars in this nursery are … Continue reading →
There are wee objects called dwarf galaxies which get their names from their small numbers of visible stars. The dwarf galaxies are expected to have high amounts of dark matter compared to other types of galaxies. But therein also lies the problem: in order to measure the amount of dark matter one has to see the stars, but in dwarf galaxies stars are sparse. The scant few stars that we do see in dwarf galaxies give us the important indication that a huge mass underlies them. This is similar to the observation that seeing the tip of an iceberg indicates that a large mass underlies it. In the December issue of Nature magazine, astronomers managed to measure the dark matter content inside of a dwarf galaxy called the Sculpter. The Sculpter is the poster child for this measurement because at only four times the distance to the Andromeda galaxy (M31), it is not so far away. Sculpter is also important … Continue reading →
Astronomers have discovered that an enormous black hole occupies the center of our own galaxy, and the centers of many other galaxies too, extending all the way back to the first 1 billion years of the universe’s history. In the latest discovery reported in Nature magazine, such an object was found when the universe was only 690 million years old. These “supermassive” black holes act like the central fire in a winter home, eagerly growing by accreting any and all material that falls within its notoriously unforgiving boundries, even growing into a bonfire if the occupants would allow it. Similarly to fires, black holes also can “bulk up” to significant sizes if fed not by firewood but rather by entire stars, with the “bonfire” equivalent called a supermassive black hole. The puzzle in this field is not so much how to build a supermassive black hole, but rather where the black hole “seeds” come from in the first place. This … Continue reading →
Close to 50 years ago we humans graduated to what astronomers call a “civilization,” or a lifeform that can send and receive messages over interstellar distances and that has the ability to travel in space. This is wonderful. At the same time, while traveling to the Moon is one achievement, traveling to another star is a vastly different level of problem. Alpha Centauri is the nearest star system to us out of the approximately 300 billion stars in our Galaxy, yet it appears to be profoundly out of reach. Such a journey would take approximately 100,000 years and require an amount of energy equivalent to one-hundred times the world’s supply. It may be that this so-called “tyranny of distance” will preclude us from ever exploring our Galactic backyard. On the other hand, humans have insatiable curiosities and a seemingly-boundless sense of imagination. One such example of dreaming big is put forward by the “Breakthrough Initiative,” founded by Yuri and Julia … Continue reading →
Unless we stop to think about it, Earth appears to be standing still. We do not feel our true speed of motion around the Sun of about 67,000 miles per hour. In turn, it is not hard to imagine the Sun also to be motionless. That is how it looks in textbooks. Yet the Sun plus Earth move together more or less randomly with respect to hundreds of other neighboring stars. In turn, the Sun and another approximately 100 billion stars orbit the center of the Milky Way at a break-neck speed of roughly 550,000 miles per hour, given or take small perturbations to the motion caused by close interactions with other stars. The Milky Way, in turn, zips about the center of mass with respect to a few dozen other companion galaxies called the Local Group. In the final rung of this ladder of motion, we measure the Local Group to move with a velocity of 1.5 million miles … Continue reading →
Recently there was an interest lecture by Joe Silk at Johns Hopkins University and the Institute of Astrophysics at Paris on the topic of the nature of dark matter. In a nutshell, the idea was put out that dark matter may take the form of black holes. Let us recall what all the fuss about dark matter is about. The material that humans are made of, and that of the Earth and all that is on it, consists of protons and neutrons arranged into the form of atoms and molecules. This is called baryonic matter, and includes also the stuff that makes up the 100 billion stars in our galaxy, and all of the stars in the other 100 billion galaxies. There is a considerable amount of baryonic matter out there. Somewhat surprisingly, it turns out that this baryonic matter sums up to a meager 3 percent of the total amount of matter in the universe. About 30 percent of … Continue reading →
How a white dwarf forms may be of interest to us as the Sun will turn into one of these bizarre objects in another 5 billion years. But first of all, what is a white dwarf again? The story begins only long after the Sun uses up all of its available hydrogen and helium fuel. At this point the core of the Sun’s long-lived (10 billion year old) former nuclear fusion reactor will be exposed as a white-hot “coal” or possibly even a “diamond.” Its initial temperature will be high, 10,000 degrees Kelvin, Celsius, or Fahrenheit (at these temperatures, take your pick). Over time white dwarfs will cool and shrink ever so slowly similar to that of a lonely yule log. White dwarfs are quite bright as a result of being so hot, such that astronomers can readily find them. And some white dwarfs are at different temperatures, indicating that they formed over a range of ages. What astronomers have … Continue reading →
Should we consider putting telescopes on the Moon? Telescope observations suffer from light pollution in the optical colors and from radio noise at longer wavelengths. To tune to radio frequencies in particular, there are very few places on Earth that are still free of television and mobile phone signals. These signals interfere with the radio waves arriving from space, and in doing so prevent us from detecting faint signals from the distant universe. The high radio sensitivity is one approach to solve the problem of what is this mysterious energy that appears to exert a kind of negative pressure on matter all across the universe that we call ‘dark energy?’ To address this question that is of interest to all physicists and astronomers, large radio telescopes are being constructed in two locations: (1) in western Australia for a project called the Single Kilometer Array (SKA) and (2) in South Africa for a project called the Hydrogen Intensity and Real Time … Continue reading →