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