The LIUniverse with Dr. Charles Liu

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A half-hour dose of cosmic conversation with scientists, educators and students about the cosmos, scientific frontiers, scifi, comics, and more. Hosted by Dr. Charles Liu, PhD, an astrophysicist at the American Museum of Natural History. Support us on Patreon.

  1. 3D AGO

    Serving Cosmic Brunch with Thresa Kelly

    How do supermassive black holes actually form in the early universe? Is the Cosmological Constant not so constant after all? And what would be on the astrophysical menu at a Cosmic Brunch? To find out, Dr. Charles Liu and co-host Allen Liu welcome astrophysicist Thresa Kelly, who is a second year grad student working on her PhD at the Rochester Institute of Technology. As always, though, we start off with the day’s joyfully cool cosmic thing, one of the recent studies made using the Dark Energy Spectroscopic Instrument, aka DESI, located at Kitt Peak National Observatory near Tucson, Arizona. According to the DESI team’s research, there is a about a 95% chance that the dark energy levels in the universe have changed over cosmic time. This “Dynamical Dark Energy model” offers the first, tiny hint that the Cosmological Constant may not be so constant after all. Thresa, who is using DESI and other sources for her work putting together a catalog of AGNs, or active galactic nuclei – the supermassive black holes found at the center of galaxies, tells us about what DESI is trying to do and why it’s so important. The end goal of Thresa’s project is to estimate the black hole masses of AGNs, and she’s gotten spectra data on over 2,000 objects that have been observed using DESI. Thresa can’t get into the details of her catalog, which hasn’t been published yet and includes about 14,000 objects, but Allen and Chuck join her in a discussion of what’s going on with black hole masses, accretion discs, Eddington Luminosity, black hole growth, galactic evolution, and more. Our first audience question comes from Kathryn, who asks, “When we look through a standard telescope looking at "past" versions of planets/stars/etc., how far back in the past are we observing?” Thresa explains how we use red shift to measure how long light from a galaxy takes to reach us to help us determine how far in the past the objects are. For instance, an AGN with a red shift of 7 can reach back to the period of “Cosmic Dawn” or, as Thresa puts it, “Cosmic Brunch” taking place 12 billion years ago. Thresa talks about her experience in an REU, or “Research Experiences for Undergraduates,” funded by the NSF, which enabled her to spend time studying at the University of Hawaii and cemented her desire to go to grad school, get a PhD, and become a “real scientist.” She explains how each step of her career brought her from Kansas to where she is today. Our next audience question comes from Walter: “If a quasar's jets are aimed directly away from Earth, would we then not be able to see the supermassive black hole?” Thresa says that depends on how you define “seeing” a black hole, and that even without visible light, you can discern black holes by looking at other wavelengths like x-rays and ultraviolet rays which are generated by different component areas of the black hole like the corona, accretion disk, or the torus. Chuck notices a shelf of games behind Thresa and asks her about them. She pulls out Stardew Valley, a farming simulator she plays with her fiancé and her fellow grad students. It’s not long until Chuck, Allen and Thresa are geeking out about Dungeons and Dragons. Finally, Chuck asks Thresa to speculate on a specific scientific discovery that may come out of her PhD thesis work. Her answer: figuring out how supermassive black holes actually form in the early universe. If you’d like to know more about Thresa Kelly, you can find her on LinkedIn. We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon. Credits for Images Used in this Episode: DESI - The Dark Energy Spectroscopic Instrument. – Credit: KPNO/NOIRLab/NSF/AURA/P. Marenfeld DESI data map of celestial objects from Earth to billions of light years away.. – Credit: Claire Lamman/DESI collaboration. Montage of dwarf active galactic nuclei candidates. – Credit: DESI collaboration. Map of galaxies based on redshift data. – Credit: Creative Commons / M. Blanton and Sloan Digital Sky Survey. Quasar PKS 1127-145, a luminous source of X-rays and visible light. – Credit: NASA/CXC/A.Siemiginowska(CfA)/J.Bechtold(U.Arizona). Model of AGN. – Credit: Creative Commons.

    39 min

  2. 12/27/2025

    2025 Year-End Special

    What were our joyfully cool cosmic things of 2025? To find out, Dr. Charles Liu and co-host Allen Liu welcome three members of The LIUniverse production team: Jon Barnes, our Editor and self-proclaimed “#1 LIUniverse Fan,” Stacey Severn, our Social Media Manager/Community Director, and physics student Eleanor Adams, the show’s first intern. Unlike nearly every episode so far, this time, rather than limit ourselves to one joyfully cool cosmic thing, the team is going to each share their individual joyfully cool cosmic things of 2025. Chuck’s saving his for later, so instead, we’re just going to jump right into everyone’s favorite “cosmic thing of the year”, starting with our co-host, Allen Liu. Allen picks the Vera C. Rubin Observatory and the Legacy Survey of Space and Time (LSST). Allen and Chuck, who is also on the Rubin’s Science Advisory Committee and has been involved in the development of the Observatory for over a quarter century, discuss how truly amazing the images are in terms of detail and resolution. Allen shares that he’s most excited to see images of transients like asteroids and gravitational lensing, since the Rubin will be taking images of the same areas twice with a gap of one week. Chuck talks about the citizen science aspect of the Rubin and encourages each of you in our audience to try and discover something on your own. We hear about some of Allen’s published papers, including one on using VR for scientific research. The group talks about VR (including Beat Saber) and Jon shares his experience using VR technology to record his senior project at the Harold Ramis Film School at Second City, and the difficulty he had with the audio. For Eleanor, this year’s cool cosmic thing was highly personal: her studies in modern physics this year, learning more than ever about what we don’t know, like the gap between classical and quantum physics! As she puts it, “the matter-antimatter asymmetry…broke my mind.” She also shares a little inspiration from Cal Sagan’s Cosmos. Stacey’s cosmically cool thing of the year is relatively current: Comet C/2025 K1 ATLAS, which recently broke into 3 parts. The team compares this with the breakup of all breakups: Comet Shoemaker-Levy 9, which broke up in 1994 on its way to a collision with Jupiter. Jon’s joyfully cool cosmic year end thingamabob is about the new science fiction show Pluribus created by Vince Gilligan (Breaking Bad, Better Call Saul), and he’s got a question for Chuck. How long would it take a signal like the one in Pluribus to travel from a star 600 light years away, like Betelgeuse or Antares? Without dropping any spoilers, the team ponders why an alien race would have reached out to Earth based on what they might have seen around the time of Charlemagne, and whether being subsumed in a hive mind would be good or bad. This is a bittersweet episode, though, because we officially bid farewell to the show’s long time editor, Jon Barnes, who is moving on to a gig as a full-time content creator for a meal prep company that will involve lots of Jon cooking and filming himself while he does. Finally, it’s time to wrap up the episode with Chuck’s Picture of the Year, which is related to the Vera C. Rubin Observatory, but not in a way you might expect. It’s a photo of Vera Rubin when she was 10 years old. As Chuck puts it, “Who would have known that 25 years later, she would change our understanding of the cosmos itself?” Happy New Year from The LIUniverse crew! If you’d like to know more about what Jon’s up to post-LIUniverse, you can check out his TikTok @iheartjonbarnes. We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon. Credits for Images and Music Used in this Episode: Galaxies imaged by the Vera Rubin Observatory. – Credit: NSF–DOE Vera C. Rubin Observatory Artist illustration of gravitational lensing. – Credit: Public Domain Comet C/2025 K1 ATLAS. – Credit: Creative Commons / Dimitrios Katevainis Comet Shoemaker-Levy 9. – Credit: NASA, ESA, and H. Weaver and E. Smith (STScI) Impacts on Jupiter from the broken-up comet Shoemaker-Levy 9. – Credit: Hubble Space Telescope Comet Team and NASA Image collage of Betelgeuse in the constellation Orion. – Credit: ESO, P.Kervella, Digitized Sky Survey 2 and A. Fujii Image of astronomer Vera Rubin, age 10. – Credit: Vera Rubin family, used with permission Music Used In This Episode: Goin' Home, derived from Dvorak's Symphony No. 9, performed by the United States Air Force Band. – Credit: Public Domain. #LIUniverse #AstronomyPodcast #CometC2025K1ATLAS #CometShoemakerLevy9 #VeraRubin

    35 min

  3. 12/14/2025

    Venus, Interstellar Visitors, and Auroras with Dr. David Grinspoon

    Are Coronal Mass Ejections dangerous to life on Earth? When are we finally going to plunge through the sulfuric acid clouds to measure the atmosphere of Venus. And what’s up with 'Oumuamua and 3I/Atlas? To find out, Dr. Charles Liu and co-host Allen Liu welcome astrobiologist Dr. David Grinspoon, aka Dr. FunkySpoon. As always, we start with the day’s joyfully cool cosmic thing: the arrival at Earth of two consecutive Coronal Mass Ejections on Nov. 11, 2025, creating an amazing display of Northern and Sothern Lights. In the US, aurora were seen as far south as Texas and even Central America, and yet Chuck, Alan and David were all frustrated by clouds in their own attempts to see them! Luckily, they’ve each already seen auroras with their own eyes, a viewing event David likens to seeing a total solar eclipse. David discusses how solar flares can impact human technology, but that while solar flares from other stars could be dangerous for life on their planets, at this point in our sun’s lifetime, they are unlikely to wipe out life on Earth. Chuck shares aurora images that were taken by our previous guest, astrophotographer Elliot Severn. For our audience questions this week, we’re answering questions given to Chuck while he was presenting at an event in Erie, PA. The first question Chuck asks David is, “When we have interstellar visitors like 'Oumuamua and 3I/Atlas, [1] why are they moving so fast in our space? They seem to defy gravity [2] How can they know what 3I/atlas is made of but not the density or materials?” David explains why the extreme speed at which they are moving is actually proof that they are interstellar objects and not something else. He also discusses how we use spectroscopy to determine what they’re made of the same way we determine what distant stars and exoplanets are made of. Our next question from Erie, PA is, “Is there a mathematical probability or formula to predict the likelihood of life existing int he universe? In other words, has someone developed a model to predict how many unique things need to happen for life to evolve?” David explains the Drake Equation, a series of questions that help astrobiologists assess the probability of intelligent life in the galaxy. Our last question from Erie is, “If humans find life on a different planet, would we actually understand how to coexist with the information, or will world leaders hide the truth from us?” David points out – as someone who has helped devise astrobiology policy – that the response depends in part on the specifics of the discovery, like how far away that life is. But would the government be able to hide it? David says that the scientists who discover it would be shouting it from the rooftops: “How long would it take to type it and hit send?” And as Chuck points out, the very act of the government trying to censor it would turbocharge the speed at which scientists would get the news out. The real problem, David says, is the potential of each discovery being overhyped by journalists, leading to public burnout. He brings up two examples of overhype: the discovery of possible biosignatures in iron nodules on the Martian rock Cheyava Falls in 2024 by the Perseverance Rover, and the presence of dimethyl sulphide in the atmospheric composition of exoplanet K2-18 b. Next, we turn to David’s “second favorite planet,” Venus, which he has studied and written about extensively. David shows us the first book he ever wrote, “Venus Revealed” and talks about upcoming missions to Venus: two from the US, DAVINCI and VERITAS; a European Space Agency mission named EnVision; a Venus Orbiter Mission by India’s ISRO, and a private Rocket Lab mission to Venus. David, who is involved with the DAVINCI mission, tells us about the plan to plunge through the sulfuric acid clouds to measure the Venusian atmosphere and surface with modern instruments for the first time. We end with a discussion of the anti-science cycle we’re going through, and David shares why he thinks this moment is so unusual and scary, but also why there is reason for hope. Chuck talks about why scientists take the long perspective, and David reminds us of the huge worldwide support for the exploration of space. If you’d like to know more about David, you can check out his YouTube channel @DrFunkySpoon, or @DrFunkySpoon on Blue Sky and Instagram. We hope you enjoy this episode, and, if you do, please support us on Patreon. Image Credits: Images of aurora over Connecticut. Credit: Elliot Severn Coronal Mass Ejection. Credit: NASA Orbit of ‘Oumuamua. Credit: CC Orbit of 3I ATLAS. Credit: NASA/JPL-Caltech Radar map of Venus made by NASA’s Magellan spacecraft. Credit: NASA/JPL-Caltech/USGS Nodules on Mars rock Cheyava Falls. Credit: NASA James Webb Space Telescope – Atmospheric composition of exoplanet K2-18 b. Credit: NASA, CSA, ESA, J. Olmstead, N. Madhusudhan Venus viewed from orbit. Credit: NASA/JPL-Caltech #LIUniverse #CharlesLiu #AllenLiu #SciencePodcast #AstronomyPodcast #DavidGrinspoon #DrFunkySpoon #Oumuamua #3IAtlas #InterstellarObjects #CoronalMassEjections #aurora #solarflares #DAVINCI #VERITAS #EnVision #antiscience #spaceexploration

    41 min

  4. 11/30/2025

    Rings, Orbits and Space Storms with Dr. Phil Nicholson

    How do planetary ring systems rings form, and what keeps them in line? What exactly is the Dragon Cloud of Saturn? And what’s up with quasi moon 2025 PN7? To find out, Dr. Charles Liu and co-host Allen Liu welcome Cornell University’s dynamical astronomer Dr. Phil Nicholson for a refresher course in orbital mechanics. As always, though, we start off with the day’s joyfully cool cosmic thing, which is right up Phil’s alley: the recent discovery of quasi moon 2025 PN7. Phil unpacks the orbital mechanics to explain the critical differences between quasi moons and regular moons, and also 2025 PN7’s strange relationship to Earth’s orbit. He also explains the dynamics of the sun’s tidal forces and Earth’s Hill Sphere. For our first question from the audience, Jameson asks, “Are meteorites smaller copies of planets. Are all of them the same?” Rather than discuss meteorites, which are the tiny survivors that have crashed on Earth, Phil pivots to where many of them come from in the first place: asteroids. Really big asteroids share some characteristics with planets, like being spherical in shape, whereas the smaller ones can be highly irregular, like the dumbbell-shaped asteroid 216 Kleopatra, or Arrokoth, previously known as Ultima Thule. Chuck asks Phil about the different shapes large asteroids can come in, and Phil points out 433 Eros, the second largest Near Earth Object, which is banana shaped. The ensuing brief discussion of the “is it a long, skinny asteroid or an interstellar starship?” debate, like the one sparked by Oumuamua, leads to a conversation about Arthur C. Clarke’s “Rendezvous with Rama”, which described just such a starship back in 1973. Somehow, we end up looking at the “face” on Mars and the “Death Star,” aka, Saturn’s moon Mimus as it was imaged by the Cassini spacecraft. Phil actually worked on the Cassini mission, and Chuck asks him to talk about his experience peering hundreds of miles deep into Saturn’s atmosphere with the spacecraft’s Visible and Infrared Mapping Spectrometer (VIMS). Along with other instruments run by other teams, the mission changed our perception of Saturn’s “boring” atmosphere, documenting aurora, lightning, and giant storms like the “Dragon Cloud of Saturn.” Our next student question comes from Marvin, who asks, “What exactly is a Shepherd moon?” To answer, Phil describes what Saturn’s rings are made of, how they form, and how they’re structured. He explains what happens when particles that make up the rings collide, why some rings spread over time, while others stay very narrow, and the role Shepherd satellites play in the process. We end with Chuck soliciting a few classic sci-fi recommendations from Phil, who suggests anything by Arthur C. Clarke, the Foundation Trilogy by Isaac Asimov, and almost anything by Larry Niven, including Ringworld, his most famous series. We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon at https://www.patreon.com/theliuniverse. Credits for Images Used in this Episode: Orbit of quasi moon 2025 PN7 – Credit: NASA/JPL Earth’s Hill Sphere extends between the Lagrange Points L1 and L2. – Credit: Creative Commons / Xander89 433 Eros, a banana-shaped asteroid.  – Credit: NASA/JPL/JHUAPL 216 Kleopatra, a dumbbell shaped asteroid – Credit: NSSDC, NASA Arrokoth, previously known as Ultima Thule  – Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko The “face” on Mars next to a higher resolution image of the same hill.  – Credit: NASA / JPL / University of Arizona Mimus as imaged by the Cassini spacecraft. – Credit: NASA / JPL-Caltech / Space Science Institute Visible and Infrared Mapping Spectrometer (VIMS) image of Saturn – Credit: NASA/JPL/Space Science Institute Dragon Cloud of Saturn – Credit: NASA/JPL/Space Science Institute Shepherd moon animation showing Prometheus (right) and Pandora (left) both orbit near Saturn's F ring. – Credit: NASA/JPL/Space Science Institute Uranus ring schematic, solid lines are rings; dashed lines are moon orbits. – Credit: Public Domain / Ruslik0   #LIUniverse #CharlesLiu #AllenLiu #SciencePodcast #AstronomyPodcast  #DynamicalAstronomy #PhilNicholson #OrbitalMechanics #Rings #SpaceStorms #QuasiMoons #2025PN7 #HillSphere #433Eros #Asteroid #216Kleopatra #Arrokoth #UltimaThule #Cassini #VisibleAndInfraredMappingSpectrometer #VIMS #DragonCloudOfSaturn #ShepherdMoon

    47 min

  5. 11/15/2025

    Tiny Galaxies and Massive Black Holes with Dr. Matt Taylor

    Can an ultra-compact dwarf galaxy have a supermassive black hole at its center? Are there galaxies with supermassive black holes that are offset from their galactic centers? To find out, Dr. Charles Liu and co-host Allen Liu welcome “the other” Dr. Matt Taylor, an Assistant Professor of Astronomy at the University of Calgary, who joins us from the control room of the largest astronomical telescope in Canada, at the Rothney Astrophysical Observatory (RAO) in Alberta, Canada. As always, though, we start off with the day’s joyfully cool cosmic thing, which starts with the discovery of a supermassive black hole in the middle of an ultra-compact dwarf galaxy M60-UCD1 located in the Virgo galaxy cluster. That led to the discovery of more 4 UCDs in the Virgo Galaxy Cluster and 1 in the Fornax galaxy clusters, but then the limits of technology prevented the discovery of any additional UCDs. But now, by using the James Webb Space Telescope, Matt and his fellow researchers (including Dr. Vivienne Baldassare, our former guest for Black Holes and Space Junk with Vivienne Baldassare) have just published a paper about their discovery that in the smallest, lowest mass UCD yet found, they found a roughly 2,000,000 solar mass black hole. Basically, that’s a tiny galaxy to hold a supermassive black hole, and Matt is sure there are many more of these waiting to be discovered. After that Matt tells us about his atypical journey to astronomy, including his first career – as a professional chef. When cooking stopped being fun, Matt enrolled at a local community college and “moved from gastronomy to astronomy” as Allen puts it. Our first audience question comes from our Patreon Patron Taylor L, who asks, “Is it possible dark energy and the acceleration of the universe's expansion could be explained by the idea that the black hole we live in is constantly devouring matter from outside?” Matt passes on determining whether or not we live inside a black hole. But, he explains that while at the galactic level expansion is happening on a really large scale, at a smaller scale like our local group of galaxies (Milky Way, Andromeda, and local dwarf galaxies), our mutual gravitation counteracts that expansion. Matt goes on to discuss how accretion disks are what makes it possible to “see” a black hole, but that ultra-compact dwarf galaxies don’t have gas and dust forming accretion disks. Instead, they use stellar velocities to find black holes in UCDs. Next up, Matt tells us about some of the research he’s doing into archetypal compact elliptical (cE) galaxies, which have the mass of a giant galaxy put into the volume of a dwarf galaxy, and how black holes appear in these systems. And Matt dangles another upcoming paper about galaxies with supermassive black holes that are offset from their galactic centers. For our next audience question, Pshemo asks: “We often say gravity is weak compared to other forces. But in the right regimes, like near black holes and neutron stars, or on large cosmic scales, it dominates every other interaction. Should we stop calling gravity a weak force?” It’s a thought-provoking question with an even better answer, so please watch or listen to the episode to hear it yourself from Matt. If you’d like to know more about Matt, you can check out his website, mataylor5128.github.io. (The 5128 comes from the famous and very cool galaxy NGC 5128, aka Centauras A) We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon.   Credits for Images Used in this Episode: Virgo and Fornax galaxy clusters. – Credit: Creative Commons / Atlas of the Universe/ Richard Powell Southern portion of the Virgo Cluster as imaged by the Vera C. Rubin Observatory in very high resolution, taken on June 5, 2025. – Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA Ultra-compact galaxy M60-UCD1. – Credit: NASA, ESA, CXC, and J. Strader (Michigan State University) Diagram of a black hole accretion disk. – Credit: NASA’s Goddard Space Flight Center/Jeremy Schnittman Hubble image of Messier 32, an archetypal compact elliptical (cE) galaxy. – Credit: NASA/ESA Centaurus A (NGC 5128) – Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)   #LIUniverse #CharlesLiu #AllenLiu #SciencePodcast #AstronomyPodcast #MattTaylor #UltraCompactDwarfGalaxy #UDC #SupermassiveBlackHole #BlackHole #AccretionDisk #M60UCD1 #ArchetypalCompactEllipticalGalaxy #UltraCompactGalaxy

    40 min

  6. 11/01/2025

    Black Holes Colliding with Dr. Charlotte Olsen

    How do very small galaxies form? What’s going on inside them? And what happens when black holes collide? To find out, Dr. Charles Liu and co-host Allen Liu welcome astrophysicist and “Galaxy Detective” Dr. Charlotte Olsen from New York City College of Technology – and you can call her Chuck, too! As always, though, we start off with the day’s joyfully cool cosmic thing, the latest announcement from LIGO about the detection of a gravitational wave event in 2023 from the loudest collision we’ve heard so far. In this case, the wave was caused by the collision of two black holes that created one new black hole about 60x the mass of our Sun and released an entire sun’s worth of energy. Charlotte explains why there are many black hole collisions going on, and how LIGO detections are now being combined with data from other gravitational wave detectors to give us more precise measurements. You’ll also hear about Active Galactic Nuclei (AGNs) and their negative impact on Charlotte’s research. Charlotte talks about what she looks for in her research, and why it all comes down to “wanting to see more photons” to better validate her modeling. Our first question from the audience comes from Joe, who asks, “What does it mean for the Milky Way to have a bar? Why does it have a bar? And how can such a long bar form?” It turns out that many spiral galaxies like ours have bars, and Charlotte explains a little about bar structure. She brings up the current debate about the stability of these bars, and points out that they actually come in slightly different configurations and that star formation at the ends of the bar has an impact, too. Unlike previous thinking, these bars can develop earlier in galactic evolution and can last a very long time. In other words, as Charlotte puts it, “The bar is always open.” Next, Chuck asks what got Charlotte into astronomy. She describes the inspiration she drew from both the dark skies of Northern California, where she grew up, and from the science fiction she read. She shares a few of her “million and one jobs” she did, including her stint as a bassist in a band. That tees up our next audience question, from Shivani, who asks, “How do you mix music and science? I can't decide if I want to be a scientist or a musician someday – can I be both?” Yes, Charlotte says, and explains why doing both might actually be better. She talks about the value of music, and passion, and hobbies that are more than just hobbies, as well as some of the live music she’s been seeing in Brooklyn, Long Island and Queens. Finally, Chuck asks Charlotte about the current passion project she’s working on. She tells us how she’s looking at a handful of galaxies in multiple wavelengths and comparing them to each other to figure out “what’s going on under the hood.” If you’d like to know more about Charlotte, you can connect with her on Bluesky at @charlotteeureka.bsky.social or on her GitHub page charlotteolsen.github.io. We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon.   Credits for Images Used in this Episode: Visualization of a binary black hole merger consistent with the gravitational-wave event called GW250114. (Note: this is to illustrate the collision of 2 black holes and the subsequent gravity waves generally, it is not specific to the GW230814 event Chuck mentions in the episode) – Credit: H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), K. Mitman (Cornell University) Animation of an active galactic nucleus. – Credit: NASA, ESA, and the Hubble SM4 ERO Team. Hubble Space Telescope image barred galaxy NGC 1300. – Credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA Data from NASA's Wide-field Infrared Survey Explorer (WISE) used to trace the shape of the Milky Way's spiral arms. – Credit: NASA/JPL-Caltech #liuniverse #charlesliu #allenliu #sciencepodcast #astronomypodcast #charlotteolsen #blackholes #ligo #gravitationalwave #blackholecollisions #activegalacticnuclei #agns #milkyway #spiralgalaxies #barredgalaxies

    42 min

  7. 10/18/2025

    Measuring the Stars with Astrostatistician Sabrina Berger

    How does a star form? How does the universe form? And how can we use every bit of astronomical data to answer those questions? To find out, Dr. Charles Liu and co-host Allen Liu welcome astrostatistician Sabrina Berger, all the way from Melbourne, Australia, where she’s currently pursuing her PhD. As always, though, we start off with the day’s joyfully cool cosmic thing, the new radioastronomy photographs of Callisto, one of the moons of Jupiter, taken by ALMA. Sabrina talks about her own low-frequency radio astronomy research looking for hydrogen in the very early reionization period of the universe when the first galaxies were forming. (Be warned: we dive into the difficulties ionization poses for trying to discern these early processes, including a side trip into quantum mechanics, the hyperfine transition of neutral hydrogen at 21cm depicted on the plaque attached to the Pioneer spacecraft, and even the Cosmic Background Radiation.) You’ll also hear how Sabrina is innovatively using GPS satellites to help calibrate large radioastronomy telescope arrays. For our first student question, Derek asks, “I heard that black holes can form right after the Big Bang, before stars do. How is that possible?” Sabrina describes these primordial black holes, and, although none have been confirmed yet, that there have been a number of papers published recently on the subject. In fact, one paper suggesting that the as-yet-undiscovered “Planet 9” could even be one of these primordial black holes. And then, finally, we get to the subject of astrostatistics, Sabrina’s area of expertise. She explains that it allows you to harness every piece of information that you’re observing in astronomy and to answer questions like “How does a star form?” or “How does the universe form?” You’ll hear about huge data sets, the use of artificial intelligence, field level inferences… and the MCMC, or the Markov chain Monte Carlo used in statistics. (If you don’t know what that is, you’re not alone, and our own resident mathematician Allen helps Sabrina untangle the complexity with a cotton ball analogy that blew Chuck and Sabrina’s collective minds!) For our next student question, Wally asks, “Why is redshift one like nine billion years ago, bur redshift two only two billion years before that, and redshift three only one billion years before that?” As Chuck says, “that’s a little complicated,” just before he, Allen and Sabrina proceed to explain how we measure universal expansion, the passage of time, and the “stretching” of light. Our next conversation is one of the most controversial we’ve ever had and revolves around who Sabrina thinks makes the best espresso, Australia, Italy or a “Third Wave Coffee Shop” like we have here in the US. You’ll hear about why there’s an ISSpresso machine on the ISS – and how the Italian Space Agency invented a way to make an espresso in zero-g! Plus, you’ll hear a little about the work-life balance in Australia and how wonderful astronomy down under is. (Check out our Patreon for the story behind the Australian Aboriginal "Emu-in-the-sky" constellation.) If you’d like to know more about Sabrina, you can find her on Twitter and Blue Sky @sabrinastronomy or check out her research on her website. We hope you enjoy this episode of The LIUniverse, and, if you do, please support us on Patreon. Credits for Images Used in this Episode: An image of Jupiter's icy moon Callisto, photographed by NASA’s Galileo spacecraft in 2001. – Credit: NASA/Galileo Photograph of Jupiter taken in 2019. The four fainter objects are four of its moons (left to right): Callisto, Ganymede, Io, and Europa. – Credit: Creative Commons / Rehman Abubakr ALMA images of Callisto – Credit: Maria Camarca et al 2025 Planet. Sci. J. 6 183. See the ALMA/Callisto paper: “A Multifrequency Global View of Callisto’s Thermal Properties from ALMA”: https://iopscience.iop.org/article/10.3847/PSJ/ade7ee Timeline of the universe. – Credit: NASA, ESA, CSA, STScI The Pioneer plaques, attached to the Pioneer 10 and 11 spacecraft. – Credit: NASA Sedna orbit with solar system (Sun, Jupiter, Saturn, Uranus, Neptune and Pluto visible) and positions on Jan 1, 2017 – Credit: Creative Commons / Tom Ruen Redshift and universe expansion. As light travels from great distances to Hubble's mirrors, it is stretched to longer and longer red wavelengths, or cosmologically redshifted, as the universe expands. – Credit: NASA, ESA, Leah Hustak (STScI) The ISSpresso machine on the International Space Station.– Credit: NASA Astronaut Samantha Cristoforetti drinking espresso out of the cup on ISS, 2015 – Credit: NASA #liuniverse #charlesliu #allenliu #sciencepodcast #astronomypodcast #sabrinaberger #astrostatistician #astrostatistics #redshift #blackholes #primordialblackholes #callisto #alma #planet9 #sedna #universeexpansion #isspresso

    44 min

  8. 09/27/2025

    Cosmic Raspberries and Life on Mars with Dr. Kelly Blumenthal

    Have we discovered life on Mars? What does the center of our galaxy taste like? To find out, and to kick off Season 5 of The LIUniverse, Dr. Charles Liu and co-host Allen Liu have reached out all the way to Tokyo to chat with Dr. Kelly Blumenthal, the Director of the International Astronomical Union Office for Astronomy Outreach. As always, though, we start off with the day’s joyfully cool cosmic thing, a rock found in Sapphire Canyon by the Mars Perseverance Rover containing potential biosignatures. Allen explains why this rock is different: iron and sulfur nodules that exhibit indications of layers which, on Earth, could only be formed by bacteria. Kelly points out that there needs to be more investigation before we can say anything for sure. Chuck asks Kelly, who when she was 12 told her dad that she wanted to study galaxy evolution, to describe the research she did at the start of her career. She talks about studying with pioneering astronomer Joshua Barnes in Hawaii during her Masters projects and PhD. For her first project, she studied star formation rates in Jellyfish Galaxies, which are being ram-stripped of their gases and so appear to have tendrils. She ended up looking at the history of merging galaxies through cosmic time using large cosmological simulations. Then it’s time for our first student question of Season 5, from Jeannie, who asks, “Now that we’ve found so many planets outside of our solar system, should Pluto be promoted as a planet again?” (Pluto’s “demotion” nearly 20 years ago was traumatic for some.) According to Kelly, though, the “demotion” was really a reclassification, and at least for the time being, Pluto is going to stay a dwarf planet, a new category of which it was the first of its kind. She contrasts Pluto to the moons of Jupiter and reminds us of the new rules about what’s a planet and what’s not. Kelly brings up Star Trek and therefore gives Chuck permission to geek out over “Devil in the Dark” from the Star Trek: The Original Series, and “Silicon Avatar” from Star Trek: The Next Generation. Kelly talks about bingeing sci-fi in high school including 2001: A Space Odyssey, and the Foundation series, and more recently, The Expanse series, which she’s listened to three times as audio books! Chuck and Kelly discuss communicating about science, and even the role science fiction can play. Kelly talks about the importance of understanding your audience. She uses the example of explaining what nebulas look like through the Chandra X-Ray Observatory to a blind and low-vision audience. Kelly also talks about how you can approach science through poetry, music, dance, theatre and art – even smell. She recalls a talk where someone working with incarcerated kids, who was limited in what props they could bring, made the universe come alive for them using the scent of raspberries, which have a similar chemical signature as the center of our galaxy. For our next audience question, Bridget asks, “So is that comet actually an interstellar spaceship?” Kelly debunks the notion that Comet 3I/ATLAS is anything other than a rock that’s come from outside our solar system and explains why extrasolar asteroids are amazing things. We end with a discussion of the IAU’s upcoming, worldwide “100 Hours of Astronomy” on Oct. 2-5, 2025, including a 24-hour live stream on Oct. 4 from the oldest functioning planetarium in Japan. Watch it live on YouTube via the IAU Office for Astronomy Outreach @IAUoutreach here.  You can also visit their website at https://iauoutreach.org/, follow IAU Office for Astronomy Outreach on Facebook and LinkedIn, and on Instagram @oao_iau. If you have any questions, email them at public@oao.iau.org. You can follow Kelly on LinkedIn.  We hope you enjoy the Season 5 premiere of The LIUniverse. Please support us on Patreon. Credits for Images Used in this Episode: Observatory History Museum at NAOJ in Mitaka – Credit: おむこさん志望, CC BY 3.0 “Sapphire Canyon” sample – Credit: NASA Perseverance Rover Iron Bacteria in Scotland – Credit: Roger Griffith Jellyfish Galaxy ESO 137-001 – Credit: NASA/ESA/CXC Jellyfish Galaxy JO201 – Credit: ESA/Hubble & NASA, M. Gullieuszik, CC BY 4.0 New Horizons probe before launch – Credit: NASA Pluto’s “Heart”, Tombaugh Regio – Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute Chandra X-ray Observatory (Illustration) – Credit: NASA/CXC/NGST Interstellar Comet 3I/Atlas – Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist, CC BY 4.0 Artist’s illustration of interstellar asteroid 1I/'Oumuamua – Credit: NASA, ESA, Joseph Olmsted (STScI), Frank Summers (STScI) Interstellar Comet 2I/Borisov – Credit: NASA, ESA, and D. Jewitt (UCLA) 100 hours of Astronomy! – Credit: IAU, CC BY 4.0 #liuniverse #sciencepodcast #astronomypodcast #kellyblumenthal #lifeonmars #bacteria #jellyfishgalaxy #pluto #interstellarasteroid #comet3iatlas #iau #officeforastronomyoutreach #startrek #theoriginalseries #thenextgeneration #theexpanse

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A half-hour dose of cosmic conversation with scientists, educators and students about the cosmos, scientific frontiers, scifi, comics, and more. Hosted by Dr. Charles Liu, PhD, an astrophysicist at the American Museum of Natural History. Support us on Patreon.

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