Starts With A Bang podcast

Since the advanced LIGO detectors first began operating in 2015, we've not only directly detected our first gravitational wave signals from merging objects in the Universe, we've observed close to 100 such systems that have emitted detectable gravitational wave signals. All of them to date, however, are the result of short-period, low-mass stellar remnants that have inspiraled and merged into one another. The most massive black holes, at least in gravitational waves, remain elusive. If all goes well, however, that won't be the case for long. At the centers of very massive galaxies, there's often not just one supermassive black holes, but multiples. Ultramassive binary black holes, in fact, send such energetic ripples through spacetime that they ought to distort, in measurable ways, the arriving radio signals from pulsars distributed all throughout the Milky Way. By monitoring these pulsars extensively through a series of timing arrays, we just might be able to extract information about the longest-wavelength gravitational waves that fill the Universe. Here to walk us through what we're looking for, how we're conducting this science, what we've seen so far, and what the prospects are for gravitational wave direct detection in an entirely new regime is Dr. Caitlin Witt, who I'm so pleased to welcome to the Starts With A Bang podcast. We've got a 100 minute spectacular for this episode, and you won't want to miss a single moment of it! Image: This illustration show how the Earth, itself embedded withing spacetime, sees the arriving signals from various pulsars delayed and distorted by the background of cosmic gravitational waves that propagate all throughout the Universe. The combined effects of these waves alters the timing of each and every pulsar, and a long-timescale, sufficiently sensitive monitoring of these pulsars can reveal the gravitational signals. (Credit: Tonia Klein/NANOGrav)

It's now been nearly a full six months since the JWST was launched, and we're on the cusp of getting our first science data and images back from some 1.5 million kilometers away. There are all sorts of things we're bound to learn, from discovering the farthest galaxies of all to examining details in faint, small objects to searching for black holes in dusty galaxies and a whole lot more. But what's perhaps most exciting are the things we're going to find that we aren't expecting, simply because we've never looked in this particular fashion before. I'm so pleased to welcome two guests to the show: Research Professors Dr. Stacey Alberts and Dr. Christina Williams both join me this month, and we have a far-ranging conversation about infrared astronomy and all that we're poised to learn from exploring the Universe in the infrared as never before. If you're already excited about JWST and what we're going to learn from it, wait until you listen to this episode! (Image: Although Spitzer (launched 2003) was earlier than WISE (launched 2009), it had a larger mirror and a narrower field-of-view. Even the very first JWST image at comparable wavelengths, shown alongside them, can resolve the same features in the same region to an unprecedented precision. This is a preview of the science we'll get. Credit: NASA and WISE/SSC/IRAC/STScI, compiled by Andras Gaspar)

When we look out at the Universe, what we see is typically what we think of: the points of light. Depending on the scales we're looking at, this can come in the form of stars, galaxies, or even clusters of galaxies, but it's almost always information that comes to us in some form of electromagnetic radiation, or light. But sometimes, light can be just as informative for what either isn't there or how it's been affected by the various media that it's passed through! In the case of our own cosmic backyard, a new study from earlier this year, 2022, revealed something spectacular and entirely unexpected: that the Sun sits at the center of a ~1000 light-year wide structure known as the Local Bubble, itself just about 15 million years old but containing all of the nearest young star clusters to us. In fact, the star Aldebaran, one of the brightest in the sky, helped "blow" this bubble in the interstellar medium! It's the very first episode of the Starts With A Bang podcast ever to feature multiple guests, and I'm so pleased to welcome Drs. Catherine Zucker, Alyssa Goodman, and João Alves to the podcast, all three of whom helped make this knowledge possible! I hope you enjoy the listen, and it's a 90 minute spectacular you won't regret spending your time on! Links: Discovery paper: https://www.nature.com/articles/s41586-021-04286-5 Press release: https://www.cfa.harvard.edu/news/1000-light-year-wide-bubble-surrounding-earth-source-all-nearby-young-stars Video: https://sites.google.com/cfa.harvard.edu/local-bubble-star-formation Interactive visualization: https://faun.rc.fas.harvard.edu/czucker/Paper_Figures/Interactive_Figure1.html (This visualization shows the Sun's location at the center of a structure about 1000 light-years across known as the Local Bubble. Recent episodes of star-formation have led to a series of new star clusters, shown in the illustration, which have formed a bubble and pushed it out. The Sun has only entered this region recently, and just happens to be at the center now, when we're looking. Credit: Leah Hustak/STScI)

Have you ever wondered how it is that we know all we do about galaxies? How they formed, what they're made of, how we can be certain they contain dark matter, and how they grew up in the context of the expanding Universe? In any scientific discipline, we have the things we know and can be quite confident in, the things that we think we've figured out but more data is required to be certain, and the things that remain undecided given the current evidence: things over the horizon of the present frontiers. Fortunately, we have the ability to scrupulously identify which aspects of galaxy formation and evolution fall into each category, and to walk right up to the edge of our knowledge and peer over that ever-expanding horizon. Joining me for this episode of the Starts With A Bang podcast is scientist Arianna Long, Ph.D. candidate at the University of California at Irvine and soon-to-be Hubble Fellow at the University of Texas at Austin. With the advent of ALMA and the James Webb Space Telescope, in particular, we're poised to seriously push back the frontiers of the unknown, and you can get the insider's view of exactly what we'll be looking for and how. This is one episode you certainly won't want to miss! Image: This view of a portion of the DREaM simulated galaxy catalog provides a snippet of sky that might correspond, statistically, with what James Webb expects to see. This particular snippet showcases an incredibly rich region of relative nearby galaxies clustered together, which could provide Webb with an unprecedented view of galaxies magnified by strong and weak gravitational lensing. (Credit: Nicole Drakos, Bruno Villasenor, Brant Robertson, Ryan Hausen, Mark Dickinson, Henry Ferguson, Steven Furlanetto, Jenny Greene, Piero Madau, Alice Shapley, Daniel Stark, Risa Wechsler)

Every time we've figured out a different way to look at the Universe, going beyond the capabilities of our own meagre senses, we've opened up an opportunity to learn something new about what's out there. Although optical astronomy and near-infrared astronomy are arguably the most popular ways to view the Universe, with James Webb soon to bring the mid-infrared Universe into view as never before, we shouldn't forget about the value of other, more distant wavelengths of light. One of the most fascinating sets of data that we can collect is in the far-infrared, where gas heated to just a few tens of Kelvin shines, but where much hotter, even ionized gas can emit very special hyperfine transitions. Mapping out these regions of space helps us understand what's going on beyond mere star-formation or other violent events, and a series of remarkably specific observational techinques are, quite arguably, how we're obtaining the most valuable information of all in this part of the electromagnetic spectrum. Joining the Starts With A Bang podcast to help guide us through the topic of far-infrared astronomy is Dr. Jessica Sutter, an astronomer at NASA Ames who's part of the USRA and who works with the SOFIA telescope, a one-of-a-kind far-infrared observatory that can do what no ground-based nor space-based observatory can. Have a listen, and I hope you wind up learning as much as I did! (The featured image shows galaxy NGC 7331 along with other members of its galactic group, including the prominent galaxies NGC 7335, 7336, 7337, and 7340. Credit: Vicent Peris/c.c.-by-2.0)

When you start looking at the Universe, you realize that there are more signals out there than are simply generated by stars. On the one hand, you have astrophysical objects like gas, dust, plasma, as well as stellar corpses and their remnants. But there are also failed stars that didn't quite make it to the nuclear fusion stage that defines our Sun and the other stars like it: brown dwarfs. Beyond that, there may also be signatures of planets like Earth out there: planets inhabited by an intelligent civilization. It's of paramount importance, when asking the biggest questions, to make sure that we aren't fooling ourselves, but that's where projects like SETI and Breakthrough Listen come in: to help us extract legitimate science where "wishful thinking" has the potential to lead us in precisely the most dangerous direction: the possibility of fooling ourselves. I'm so pleased to welcome Ph.D. Candidate Macy Huston to the podcast, as we explore the less commonly seen side of the Universe: from exoplanets to brown dwarfs to the search for extraterrestrial intelligence. With the advent of the James Webb Space Telescope, we really are going to see a tremendous change in what we know!

Some stars, as they go through their life cycles, will die of natural causes. They'll burn through their fuel until they can fuse elements no longer, and then will die, becoming a white dwarf below a certain mass threshold, or experiencing a core-collapse supernova that leaves behind a neutron star, a black hole, or perhaps something even more interesting above that mass threshold. But some stars, while just going about their lives, can suffer a wildly different fate: they can be murdered by other objects in the Universe. Stellar destruction can take many forms and can give off many different unique signals, and it's only by examining a wide range of the electromagnetic spectrum, as well as other types of sources, that we can decode what's actually going on across the Universe. I'm so pleased to welcome Dr. Yvette Cendes to the program, who specializes in radio astronomy and the behavior of exotic objects that change their behavior over time: transient signals. There's so much to explore and I hope you enjoy this fascinating 90 minute discussion right here on the Starts With A Bang podcast! (Credit: Alak Ray, Nature Astronomy, 2017; ACTA/ALMA/ESO/Hubble/Chandra composite)

When it comes to the black holes that populate the Universe, they range from the very tiny, of only ~3 solar masses or so and with event horizons that span only a few kilometers, all the way up to the incredibly supermassive, many billions of times as massive as our Sun, with event horizons on the scale of the entire Solar System. These black holes are fascinating not only for how they form and exist, but how they impact and shape the entire galaxies that they inhabit. At all different wavelengths, from X-ray to radio, as well as in gravitational waves, we're only starting to uncover the previously elusive science about these cosmic behemoths, and while we're all the richer for it today, it's fascinating to consider what questions we'll be answering decades down the line, too. Come have a listen to all of these topics and much, much more as we go on a fascinating journey concerning supermassive black holes with Dr. Adi Foord of Stanford, and expose the mysteries of the largest single structures in the entire Universe! (Image credit: NASA)

You know how it works, right? Point your telescopes at the sky, collect the data, and then send it off to the scientists for analysis and to compare with the predictions of your theories. Only, if that's what you do, you'll miss a crucial first step: you have to handle your data correctly. That means understanding the nuances of your telescope, the sensitivities of your instruments and optics across different filters and wavelengths, and so many other considerations before that data you've collected could ever be responsibly used for any scientific purposes at all. But this is not a hopeless task; there are entire careers in telescope and instrument support sciences that, in many ways, are the unsung heroes of the entire enterprise of astronomy. In this edition of the Starts With A Bang podcast, I'm so pleased to get to bring Dr. Heather Fleweling onto the show, where she talks about her experience and expertise doing precisely this for observatories such as Pan-STARRS, which she helped build herself, to the Canada-France-Hawaii Telescope (CFHT), where she currently works, specializing in the MegaPrime instrument. Get a behind-the-scenes peek at a corner of astronomy that most people don't even know exists!

In the science of astronomy, it's important to see both the forest and the trees. Galaxy clusters, in many ways, serve as both. They're rich environments with stars, gas, dust, dark matter, black holes and more. The diversity of stars and stellar populations found within them, as well as found within galaxies of different shapes, sizes, and properties within those clusters, are part of a remarkable and coherent cosmic story. But sometimes the cosmic story can help us understand what's going on in these environments, the converse of the way we normally think about it: where we use the environment to learn about the universe. Come take a fascinating journey into these cosmic behemoths that are the gathering grounds for the greatest collections of large galaxies in the universe, and enjoy a delightful conversation with Gourav Khullar as we go along on this wild ride! (Image credit: ESA/Hubble and NASA, H. Ebling)