Starts With A Bang Podcast

Whenever a new star forms, several processes appear to be nearly universal. A cloud of cold molecular gas contracts, fragments, and rapidly collapses in certain places. The densest, coldest clumps of gas contract first, drawing in larger and larger amounts of matter onto them. A large, massive enough clump will heat up and have a random shape: collapsing along the shortest axis first, forming a protostar at the center surrounded by a disk of material. That's where the story of planet formation begins.Assuming the conditions in the disk are sufficient, clumps will begin to form, and over hundreds of thousands to millions of years, the first protoplanets and then full-fledged planets will arise: a relatively rapid cosmic process, that's usually all complete within a mere 10 million years: a blink of a cosmic eye in the history of our own 4.5 billion year old Solar System. However, by looking at the youngest stellar and planetary systems, we can uncover many details that are common to planetary systems i

When most of us were children, and we went to a rural area with clear skies overhead at night, we were all greeted by the same familiar sight: a dark night sky, glittering with many hundreds or even thousands of stars. Depending on how dark your sky was, you could spot up to 6000 stars at once, as well as deep-sky objects, the plane of the Milky Way, and only the rare, occasional satellite streak. As time went on, more and more satellites were launched, bringing us up to around 2000 active satellites as of 2019.And then we entered the era of satellite megaconstellations, beginning with the launch of the first Starlink satellites. Now, nearly 7 full years later, there are over 17,000 active and defunct satellite payloads in orbit, with approximately 100 times as many satellites proposed in the coming years. From satellite communications to direct-to-phone links to the proposition of AI data centers in space, the number of proposed use cases has exploded. However, as the environment around Earth becomes more cr

Out there in the Universe, we're most aware of what we see: of all the forms of light that arrive in our eyes, instruments, telescopes, and detectors. Much more difficult to see, as well as understand and make sense of, is the wide array of "stuff" that's present, but that isn't readily apparent to the apparatuses we normally use to reveal the Universe. From the dark bands of the Milky Way to the light-blocking materials in nebulae and clouds, all the way to lining the arms of spiral galaxies and the heavy, long-chained molecules found in protoplanetary disks, cosmic dust is perhaps our most enduring mystery.Sure, it gives absorption signatures that we can leverage, and at long enough infrared wavelengths, dust that gets heated has its own emission signatures, but we can generally only observe it in detail up close: within our own galaxy or in the nearest galaxies of all. That poses a huge challenge, because the origin of dust, including from a cosmic perspective, remains only very poorl

One of the most exciting developments in modern astrophysics isn't merely our standard "concordance cosmology" model, but rather the cracks that seem to be emerging in it. Sure, we've said for some 25 years now that our Universe is 13.8 billion years old, is made of mostly dark energy with a substantial amount of dark matter, and only 5% of all the normal stuff combined: stars, planets, black holes, plasmas, photons, and neutrinos. But more recently, a couple of cosmic conundrums have emerged, leading us to question whether this model is the best picture of reality that we can come up with.We don't merely have the Hubble tension to reckon with, or the fact that different methods yield different values for the expansion rate of the Universe today, but a puzzle over whether dark energy is truly a constant in our Universe, as most physicists have assumed since its discovery back in 1998. While "early relic" methods using CMB or baryon acoustic oscillation data favor a lower value

All across the Universe, stars are dying through a variety of means. They can directly collapse to a black hole, they can become core-collapse supernovae, they can be torn apart by tidal cataclysms, they can be subsumed by other, larger stars, or they can die gently, as our Sun will, by blowing off their outer layers in a planetary nebula while their cores contract down to form a degenerate white dwarf. All of the forms of stellar death help enrich the Universe, adding new atoms, isotopes, and even molecules to the interstellar medium: ingredients that will participate in subsequent generations of star-formation.For a long time, however, we'd made assumptions about where certain species of particles will and won't form, and what types of environments they could and couldn't exist in. Those assumptions were way ahead of where the observations were, however, and as our telescopic and technological capabilities catch up, sometimes what we find surprises us. Sometimes, we find elements in places that

One of the great discoveries to be made out there in the grand scheme of things is alien life: the first detection of life that originated, survives, and continues to live beyond our own home planet of Earth. An even grander goal that many of us have, including scientists and laypersons alike, is to find not just life, but an example of intelligent extraterrestrials: aliens that are capable of interstellar communication, interstellar travel, or even of meeting us, physically, on our own planet. It's a fascinating dream that has been with humanity since we first began contemplating the stars and planets beyond our own world.Most of us, including me, personally, have assumed that this latter type of alien would not only be more technologically advanced than we are, but would also be far more scientifically advanced as well. That not only would they understand everything we presently do about the fundamental laws of physics, but far more: that they'd be a potential source of new knowledge for us, having

It's no secret that the Universe and the objects present within it, as we see them all today, have changed over time as the Universe has grown up over the past 13.8 billion years. Galaxies are larger, more massive, more evolved, and are richer in stars but fewer in number than they were back in the early stages of cosmic history. By looking farther and farther away, we can see the Universe as it was at earlier times, but we're going to be limited in many ways: by how deep our telescopes can see, by what wavelengths they're capable of seeing, and by what small fraction of the sky they're capable of observing.That's why an observing program like COSMOS-Web, the largest, widest-field JWST observing program to date, is so important. It isn't just revealing galaxies as they are nearby (at late times), at a variety of intermediate distances (and earlier times), and at ultra-large distances (and the earliest times of all), but due to its wide-field nature, is revealing galaxy types of varying

It's hard to believe, but it was only back in the early 1990s that we discovered the very first planet orbiting a star other than our own Sun. Fast forward to the present day, here in 2025, and we're closing in on 6000 confirmed exoplanets, found and measured through multiple techinques: the transit method, the stellar wobble method, and even direct imaging. That last one is so profoundly exciting because it gives us hope that, someday soon, we might be able to take direct images of Earth-like worlds, some of which may even be inhabited.Although it may be a long time before we can get an exoplanet image as high-resolution as even the ultra-distant "pale blue dot" photo that Voyager took of Earth so many decades ago, the fact remains that science is advancing rapidly, and things that seemed impossible mere decades ago now reflect today's reality. And the people driving this fascinating field forward the most are the mostly unheralded workhorses of the fields of physics and astronomy: the

Out there in the Universe, somewhere, a second example of an inhabit world or planet likely awaits us. It could be some other planet or moon within our own Solar System; it could be a spacefaring, interstellar civilization, or it could be an exoplanet around a different parent star. Although the search for life beyond Earth generally focuses on worlds that have similar conditions to Earth, like rocky planets with thin atmospheres and liquid water on their surfaces, that's not necessarily the only possibility. The truth is that we don't know what else is going to be out there, not until we look for ourselves and determine the answers.And yet, if you've been paying attention to the news, you might think that super-Earth or mini-Neptune type worlds, such as the now-famous exoplanet K2-18b, might be excellent candidate planets for life. Some have even gone as far as to claim that this planet has surefire biosignatures on it, and that the evidence overwhelmingly favors the presence of life within this

Perhaps the strongest evidence we've ever acquired in support of the Big Bang has been the discovery of the leftover radiation from its early, hot, dense state: today's cosmic microwave background, or CMB. While there were many competing ideas for our cosmic origins, only the Big Bang predicted a uniform, omnidirectional bath of blackbody radiation: exactly what the CMB is.But it turns out the CMB encodes much more information than just our cosmic origins; it allows us to map the very early Universe from when it was just 380,000 years old, and gives us vital information about what has happened to light from that time over its 13.8 billion year journey to our eyes. It encodes information about our cosmic expansion history, about dark matter and dark energy, about intervening galaxy clusters, and about the material here in our own galaxy, along with much more. It is, arguably, the richest source of information from any one single observable in our entire Universe.Here to guide us through what CMB scient

When we search for life in the Universe, it makes sense to look for planets that are similar to Earth. To most of us, those signatures would look the same as the ones we'd see if we viewed our planet today: blue oceans, green-and-brown continents, polar icecaps, wispy white clouds, an atmosphere dominated by nitrogen and oxygen, and even the modern signs of human activity, such as increasing greenhouse gas emissions, planet modification, and electromagnetic signatures that belie our presence.But for most of our planet's history, Earth was just as "inhabited" as it is today, even though it looked very different. One fascinating period in Earth's history that lasted approximately 300 million years resulted in a planet that looked extremely different from modern Earth: a Snowball Earth period, where the entire surface, from the poles to the equator, was completely covered in snow and ice. This isn't just speculation, but is backed up by a remarkable, large suite of observational and geo

It might seem hard to fathom, but it hasn't even been ten full years since advanced LIGO, the gravitational wave observatories that brought us our very first successful direct detection, turned on for the very first time. In the time since, it's been joined by the Virgo and KAGRA detectors, and humanity is currently closing in on 300 confirmed gravitational wave detection events. What was an unconfirmed prediction of Einstein's General Relativity for a full century has now become one of the fastest-growing fields in all of astronomy and astrophysics.Here in 2025, we're now looking forward to the LISA era: where we're going to build our first gravitational wave detectors in space. They'll have far longer baselines (i.e., separations between the various spacecrafts/stations) than any terrestrial gravitational wave detector, enabling us to detect fundamentally different classes (and masses) of objects that emit gravitational waves. At the same time, the rise of artificial intelligence and

Out there in the Universe, each star represents an opportunity: a chance for a stellar system to develop that just might possess something remarkable. While we normally think about life, and intelligent life at that, as the grand prize the Universe has to offer, there are a wide variety of fascinating phenomena that are out there to consider. Whereas Mercury, for example, is the closest world to our Sun in our own Solar System, it still takes 88 days to make a complete revolution. In other systems, however, exoplanets can be so hot that they orbit their parent star in less than a single Earth day.In fact, we've discovered a few systems that are so extreme, the planets that orbit them are in the process of disintegrating: where the heat, winds, and radiation from the parent star actually blows part of the planet itself away. This doesn't just include a planet's atmosphere, which is what we see for giant worlds, but even the surfaces and interiors of rocky planets in the most extreme cases. At tempe

Sure, it's easy to look out at the Universe and take stock of what we find. Although spiral and elliptical galaxies house the majority of the Universe's stars, represented locally by galaxies like Andromeda and our own Milky Way, the overwhelming majority of galaxies are much smaller and lower in mass than we and our cousins are. These low-mass galaxies, the dwarf galaxies in the Universe, represent upwards of 97% of all the galaxies that exist.However, while most of the dwarf galaxies we know of are found as satellites around larger, more massive galaxies, they aren't good laboratories for helping us understand the Universe as it was long ago. Back during the first few billion years of cosmic history, it wasn't just dwarf galaxies that formed the majority of starlight in the cosmos, but isolated dwarf galaxies: dwarf galaxies that hadn't yet interacted with larger neighbors.We can best understand those early-stage galaxies by studying their late-time analogues: isolated dwarf galaxies in

Out there in the Universe, there are tremendous, uncountable numbers of planetary systems just waiting to be discovered. But stellar systems won't just consist of planets orbiting a parent star; there will be moons, asteroids, Kuiper belt-like objects, and many of them will be bound together into their own rich sets of systems, with both irregular and round bodies comprising these planetary systems.Here in our own Solar System, we have at least three notable large, terrestrial-sized bodies with impressive lunar systems of their own: the Earth-Moon system, the Mars-Phobos-Deimos system, and the Plutonian planetary system. Pluto, interestingly, is orbited by Charon, which is very large and massive compared to Pluto, an unusual and possibly unique, or most extreme, configuration of all known such bodies. But how did it get to be that way? That's the topic of this podcast, and the research focus of this month's guest: Dr. Adeene Denton.It's kind of amazing what variety can emerge in terms of survi

When it comes to stars, most of them, for most of their lives, behave in a very similar fashion to the Sun. In their cores, they undergo nuclear fusion, which provides energy and creates radiation, and that outward radiation pressure holds the star up, internally, against gravitational collapse. For most stars, this balance between the pressure from outward radiation and the inward force from gravitation is nearly perfect all throughout the star, leading to an equilibrium state. But some stars aren't in this kind of equilibrium at all. Instead, some internal process actually drives the star in a fashion that causes it to pulsate: overshooting equilibrium in both directions, as it alternatingly expands and cools, and then contracts and heat up in a cyclical fashion. These species of intrinsic variable stars, including Cepheids and RR Lyrae stars, are not only of profound importance when it comes to understanding stellar evolution, but for unlocking the secrets of the distant Universe. How do we understand thes

When we look out at our home galaxy, the Milky Way, we have to recognize that even though it's been growing and evolving for 13.8 billion years, we're only observing it as it is right now: a snapshot in time determined by the light that's arriving in our instruments right now. However, just like we're living "right now" in human history but can, through the science of archaeology, learn about historical events that happened many thousands of years ago (before recorded history) or even earlier, we can learn about the Milky Way's history through the astronomical equivalent: galactic archaeology. How do galactic archaeologists do it? They look at as much data as possible, across many wavelengths of light, including at many rare and obscure species of stars, in as many locations as possible and to the greatest precisions possible all at once. By combining these different lines of evidence, we can arrive at a coherent and compelling picture for how our little corner of the Universe grew up, including by reconstruc

In this Universe, there are a few objects that are just larger, and a few events that are just more powerful, than others. As far as size goes, the cosmic web creates some of the largest features ever discovered, with the largest galaxy filaments and the largest regions devoid of galaxies spanning as much as ~2 billion light-years. No robust, verified structure has ever been found that's larger. Meanwhile, as far as energy and power go, collisions of galaxy clusters are the most energetic events, outstripped only by the Big Bang itself. However, nearly rivaling galaxy cluster collisions are the strongest black hole jets ever seen, capable of emitting trillions of times the energy of a Sun-like star, but also capable of sustaining those energies over timescales of a billion years or more. Astronomers have just set a new record for the longest black hole jet with the discovery of Porphyrion, which spans a whopping 24 million light-years across! How did this jet and others like it come to be, and what effects do

It's hard to imagine, but it was only five years ago, in 2019, that humanity feasted our collective eyes on the first direct image of a black hole's event horizon. Thanks to the technique of very long baseline interferometry and the power of arrays of radio telescopes stitched together from all across the Earth, we were able to resolve the event horizon of the black hole M87*, despite the fact that it's an impressive 55 million light-years away.That was with radio interferometry, but historically, most telescopes have used optical light, not radio light. Does that mean that optical interferometry is possible? Not only is the answer a resounding "yes," but we've been performing it for decades. In fact, the most ambitious optical interferometry project of all-time is already under construction in New Mexico: the Magdalena Ridge Observatory Interferometer (MROI). With an array that will feature a total of ten separate telescopes all linked together, and with a maximum tunable distance of 340 meters between them

When you think of an active galaxy, what picture comes to mind? Do you think about a monstrous supermassive black hole feasting on tremendous stores of gas and other forms of matter? Do you picture an enormous disk of accreted matter, being accelerated, heated, and eventually shot out along two jets, each perpendicular to the disk itself? This common picture of active galaxies describes many of the most prominent ones, but isn't universal to them all. Some active galaxies aren't giant ellipticals, but just average-looking spiral galaxies. Some galaxies aren't in the process of a major merger, but seem to be powered by their own internal gas. And some of these black holes aren't ridiculously massive, with billions of solar masses inherent to them, but are rather much more modest. Some of these active galaxies actually show practically no signs of activity in visible light, but must be viewed in other wavelengths, such as with radio telescopes, to reveal their activity. Above, you can see galaxy