When we look out at the galaxies in the Universe, almost all of them have supermassive black holes at their centers: millions or even many billions of times more massive than our Sun is. Most of the time, these black holes are relatively quiet, but every so often, a black hole can be spotted emitting enormous amounts of radiation over a large range of the electromagnetic spectrum. These "active galaxies" come in many different flavors, from blazars to AGNs to quasars and many others, but they're...
Aug 14, 2020•1 hr 37 min
When it comes to gravitational waves, our terrestrial laser interferometers have provided us with unparalleled success in terms of direct detection. But they have some strong fundamental limits: their laser arms are short; their sensitivity is limited to low-mass, small-radius objects; the signals they detect last for mere seconds, at most. Most importantly, seismic noise, and even the fact that we live on a planet with tectonic plates, place restrictions on how sensitive we'll ever be able to g...
Jul 17, 2020•1 hr 20 min
Even today, the Universe is forming enormous numbers of new stars: from various nebulae throughout our galaxy to mighty starburst galaxies where the entire galaxy is an enormous star-forming region. A decade ago, we were still trying to figure out how, when, and where stars formed throughout the Universe; today, we have that nailed down, but a whole suite of new questions and puzzles have arisen as a result of what we learned. On this edition of the Starts With A Bang podcast, I'm pleased to wel...
Jun 12, 2020•1 hr 7 min
Dark matter is often thought of as the glue that holds the Universe together. With five times as much gravity due to this unseen form of matter as compared to normal, atom-based matter, it affects how galaxies and giant large-scale structures form in a tremendous, truly epic way. But depending on what the properties of dark matter actually are, we should get a very different Universe on smaller scales. Is dark matter cold? Warm? Hot? And does it interact with itself, or is it truly invisible? Th...
May 09, 2020•1 hr 10 min
When you look up at the sky, most of the points of light we see appear to be fixed. On night-to-night timescales, the distant stars and galaxies, with the exception of a few notable variables, appear to be relatively unchanged. But every once in a while, a spectacular event will occur, giving off a transient signal that outshines a typical star's brightness by factors of many billions. These events fall into many classes: supernovae, gamma ray bursts, and even more exotic events, and part of the...
Apr 10, 2020•1 hr 10 min
One of the great challenges for astronomy is to determine, in gory detail, how stars are formed from a mere cloud of molecular gas and dust. Although the general picture is simple, where gravitational collapse leads to protostars that ignite nuclear fusion in their cores, the actual environments where these stars are born have many competing factors at play. Gravitational collapse is only one of them, joined by thermal heating and radiative cooling, magnetic fields and hydrodynamics, as well as ...
Mar 04, 2020•1 hr 11 min
How many planets are out there in the Universe? How many stars have planets, and what kinds of planets do stars of various types have? How close are we to doing direct imaging, finding whether some of our Earth-like planets are potentially habitable or even inhabited? Are Super-Earths a real thing, or are all of the ones larger than our world more Neptune-like than we care to admit? We've answered a whole slew of questions about exoplanets that we didn't even know to ask a decade or two ago, and...
Feb 07, 2020•1 hr 4 min
The history of astronomy is a history of receding horizons. As we improve our optics, our instruments, and our observing techniques, we can reveal progressively more of the Universe than we've ever seen before. As the 2020s dawn on us, we're preparing to jump from 10 meter-class observatories, which are presently the largest in ground-based optical telescopes, to 30 meter-class ones, with approximately thrice the resolution and ten times the light-gathering power. There's a tremendous suite of c...
Jan 09, 2020•1 hr 21 min
Have you ever wondered what the first moments of our Universe were like? Not just going back towards the hot Big Bang, but at the very first fractions of a second that come after, during, and even before the Big Bang occurs? It was my pleasure to get to speak to Dan Hooper, astrophysicist, professor, and author of the new book At The Edge Of Time, which is my favorite popular science book of 2019. (Pick up a copy here: https://amzn.to/2XReiGG) In this fascinating hour+ conversation, we cover top...
Dec 14, 2019•1 hr 9 min
What lies out there, in the outer Solar System, beyond the orbit of the last known planet? Up until 1992, you would have said Pluto and its moon (maybe "moons" if you were willing to speculate), but even the existence of the Kuiper belt was doubted by many. Of course, all of that changed with the discovery of many different objects, including the more-massive-than-Pluto world discovered in 2003: Eris. We quickly realized that Pluto was not unique, but one member of a distinct class of objects th...
Nov 14, 2019•1 hr 18 min
The Large Hadron Collider, located at CERN, is the most powerful particle accelerator and collider in human history, and the detectors that observe the collisional debris are the most sensitive and comprehensive ever constructed. With this powerful new tools, physicists discovered the Higgs boson earlier this decade, and continue to probe the frontiers of the known Universe. Currently undergoing upgrades, the LHC has only collected, to date, 2% of the eventual data it will wind up collecting. Me...
Oct 12, 2019•1 hr 33 min
Earlier this year, 2019, the Event Horizon Telescope collaboration revealed the first image that directly showed the existence of an event horizon around a black hole. This image, constructed from many petabytes of data from telescopes observing the same target, simultaneously, from all across the Earth, provided a breathtaking confirmation of Einstein's relativity in a realm where it had never been tested before. But that's just one image of one black hole at one particular moment in time, and ...
Sep 12, 2019•1 hr 13 min
What do we really know, and what mysteries are left to solve, about the outer worlds of our Solar System, and about the gas giant and ice giant worlds found throughout the Universe? Remarkably, if you had asked this same question 30 years ago, we would have had a quaint story about how planets form and why our Solar System has the planets it does, and we assumed that these rules would be extended to all solar systems in the galaxy and Universe. But with the deluge of exoplanet data, accompanied ...
Aug 07, 2019•1 hr 27 min
We know that there's more to the Universe than we presently know. As successful as the Standard Model may be, it cannot describe everything we observe to be true about the Universe. Neutrinos oscillate from one flavor into another, and must have a non-zero mass, but we don't understand why or how. Dark matter has an overwhelming suite of astrophysical evidence that points towards its existence, but we have no direct evidence for the type of particle it might be. What do we do about these puzzles...
Jul 19, 2019•1 hr 31 min
With all the planets out there in the galaxy and Universe, it's only a matter of time and data until we find another one with life on it. (Probably.) But while most of the searches have focused on finding the next Earth, sometimes called Earth 2.0, that's very likely an overly restrictive way to look for life. Biosignatures, or more conservatively, bio-hints, might not only be plentiful on worlds very different from our own, but around Solar Systems other than our own. Earth-like worlds, in fact...
Jun 14, 2019•1 hr 15 min
One of the biggest conundrums in the Universe surrounds the question of how quickly the Universe is expanding. Questions like what is the Universe made of, how old is it, what is it's ultimate fate, etc., absolutely depend on this. For generations, we argued over the details of this, seeming to have finally reached a consensus in 2001 with the Hubble Key Project's results: 72 km/s/Mpc, with an uncertainty of about 10%. But the modern results, as of 2019, seem to depend on how you measure it. Som...
May 03, 2019•1 hr 2 min
When we think about finding planets in the Universe, we typically look for ways to detect them as they orbit their parents stars, either affecting their star's position or velocity, or blocking or reflecting a certain portion of their light. But what about the planets that are too small to be detected that way? What about the planets whose effects are imperceptible? And what about the rogue planets: the ones that no longer (or perhaps never did) orbit a star of their own? Well, they're not doome...
Apr 08, 2019•1 hr 9 min
So, you want to know about black holes, including how we're seeing them, what happens when you fall into them, what our future plans for direct and indirect detection are, and how scientists are answering some of the biggest questions about them today? It's a fascinating story about some of the most mind-blowing objects in the Universe. Please welcome Assistant Professor of Astronomy and Physics at the University of Mississippi, Dr. Leo C. Stein, to the show, and enjoy a 1 hour+ conversation whe...
Mar 25, 2019•1 hr 11 min
After the Big Bang, it took only a few hundred thousand years for the Universe to form neutral atoms. But it took tens or even hundreds of millions of years for the first stars to turn on, and a whopping 550 million years for those neutral atoms to all become reionized by that starlight once again. Believe it or not, we can measure not only the starlight coming from the stars that do form through the now-infrared light they emit, but also the neutral atoms themselves through the power of 21-cm a...
Feb 25, 2019•1 hr 1 min
One of the great goals in our study of the Universe is to see past the currently-known frontiers. That means going farther, to greater and greater distances. It means going fainter, to smaller and less-easy-to-see objects. It means going to earlier times and less-evolved conditions. And it means detecting more of the Universe than we've ever seen before. Our goal is the most ambitious one you can imagine: understanding what the Universe was like when it was born, how it grew to be the way it is ...
Jan 12, 2019•1 hr 2 min
Is there intelligent life out there in the Universe beyond planet Earth? If so, are they technologically advances, can they hear us, and are they broadcasting in ways that we could possibly detect them? In the absence of their arrival on Earth, you might think that there's no surefire way to know. But the scientists working hard on SETI, the Search for ExtraTerrestrial Intelligence, sure are trying their best. By listening to the Universe at large (and our galaxy in particular), they're hoping t...
Dec 20, 2018•58 min
In 2017, the incredible happened: for the first time in history, we were able to identify an object passing through our Solar System that originated from outside of it! Interstellar interloper 'Oumuamua was originally designated as a comet, then as an asteroid, and then as a new class of object: one of interstellar origin. It's a fascinating object that's the first of its kind, and much has been said about its composition, properties, and possible nature. But, unfortunately, the most famous of t...
Nov 21, 2018•55 min
Our Solar System formed some 4.6 billion years ago from a molecular cloud that collapsed. Our proto-Sun formed along with a protoplanetary disk that eventually evolved into the Solar System we have today, complete with the inner, rocky planets, an asteroid belt, the gas giants and their moons and ringed systems, and then the outer Solar System. Those outer regions sure are interesting, and it's only over the past 3 decades we've really started to learn about them in earnest. I had the opportunit...
Oct 23, 2018•1 hr 12 min
I'm so pleased to welcome Dr. Erin MacDonald to the Starts With A Bang podcast, as we discuss the future of Gravitational Wave astronomy. From pulsars to merging black holes, to kilonovae to hopes of observing gravitational wave signatures from the earliest moments of the Universe, we cover a whole lot of astrophysics, cosmology, and experimental hopes for the near future in this burgeoning new field of astronomy. The future of gravitational wave science is so bright, even without the collection...
Sep 28, 2018•51 min
There's been a lot of speculative ideas put forth about the Multiverse, and I dare say that a great many of them are nothing more than wishful thinking. But that doesn't mean the Multiverse itself is ill-motivated at all. Rather, if you take two of our best theories that have been well-confirmed in a wide variety of different ways, you're going to find that you arrive at a bizarre but unavoidable picture: one of an inflating spacetime, eternal to the future, where regions that look like our Univ...
Aug 31, 2018•20 min
The Universe, today, is expanding and cooling, as the volume of the Universe increases while the number of particles within it remains constant. If you extrapolate forwards in time, the Universe gets sparser, less dense, and closer to being completely empty. But if you extrapolate back in time instead, the Universe gets hotter, denser, and smaller in volume. Eventually, if you didn't stop yourself, you'd go all the way back to a state of infinite density, where all the matter was packed into a s...
Jul 27, 2018•25 min
Have you ever wondered what's out there in the Universe, on the largest scales, beyond what we can even observe? Or what lies down below the tiniest distance scales we've ever probed? Is there a smallest fundamental length scale in the Universe, like the Planck scale, or can we go down even farther? Is space discrete or continuous? And is the Universe fundamentally blurred; can we even distinguish? Thinking about the limits of space, on both small and large scales, is a mind-bending game to play...
Jun 29, 2018•28 min
There are three very different ways humanity is searching for alien life beyond Earth. We can directly search the various planets and moons in our Solar System for past or present biological signatures simply by sending decontaminated probes, and looking for the evidence in situ. We can indirectly look at distant worlds around other stars, searching for the characteristic changes to the atmosphere and surface that life would bring. And, most optimistically, we can search for intelligent signatur...
May 30, 2018•21 min
There are some incredibly big questions that humanity has been asking about the Universe since we first began looking upwards: what is the Universe like, how did it get to be this way, where did it all come from, and what is its eventual fate? There were huge advances that were needed in order to answer these questions, such as understanding what the Universe was made of, how fast it was expanding, and what the laws governing it were. But once we know that, not only can we answer these questions...
Apr 30, 2018•17 min
In memory of Stephen Hawking's life, I've decided to share the physics behind his greatest discovery: Hawking radiation. For a long time, in the context of relativity, we thought that black holes were static, unchanging objects defined only by their mass, charge, and angular momentum. A number of developments led us to understand that black holes needed to have entropy, temperature, and therefore, they needed to radiate. But Hawking was the one to put that puzzle together, and describe the physi...
Mar 29, 2018•22 min
