Starts With A Bang podcast

One of the most foundational questions we know how to ask in astronomy is simply this: given a cloud of gas of a given mass, what types of stars will form? How many stars of a given mass will you wind up with, and what factors does that depend on? The answer to this question, if we can give an answer, is known as the "initial mass function," and is generally very difficult to measure except in the most nearby of places: within our ...

We often think about the Solar System as being our own cosmic backyard, and in many ways, it is: these are the closest objects to us in all the Universe, and our only opportunity to study lunar and planetary systems in situ. However, when it comes to the objects beyond Saturn, including the Uranian and Neptunian systems, as well as everything that lies in the Kuiper belt and beyond, the only probes we've ever sent their way are Voy...

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...

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 sat...

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...

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....

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 ...

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, interstell...

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 goin...

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, som...

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 a...

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...

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 modific...

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 Gen...

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 ...

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 galaxi...

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 ...

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 throu...

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 th...