Barbie versus Oppenheimer the Prologue — NANOGrav versus IceCube
Just last week, on an unassuming Thursday, the astro(physics) community got served two humongous cakes at once. Both the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) and the IceCube Neutrino Observatory (IceCube) have ground-breaking scientific findings to share with the class!
As an astrophysicist 🤓, I did, indeed, catch both press releases (maybe procrastination is okay if it’s science-related?). At 1pm EST, NANOGrav announced that they have found evidence for low-frequency gravitational waves humming across our galaxy. NANOGrav releases their findings and a quick overview of how they achieve this with their pulsar-timing array in this beautiful article. Long story short: highly magnetized, rotating neutron stars, called pulsars, constantly emit radio-wave beams from their poles at highly regular intervals (some of them have periods more stable than atomic clocks!). By observing many of them at once, we can detect any anomaly in their periods. If this anomaly happens across the board – we got a gravitational wave on our hand! The cool thing about using pulsars is that we can detect an entirely different range of gravitational wave frequency to that of LIGO or the LISA space probe launched in the near future. Think electromagnetic waves: we have radio, microwave, infrared, …, up to X-Rays and gamma rays, all defined by their frequency and astronomers have different telescopes designed to observe one, or maybe two, specific ranges. The same thing applies for gravitational waves and their frequency! The waves detectable by NANOGrav have a period of years, which is too low-frequency for the mirrors of LIGO to catch. With this set up, we now have evidence that low-frequency gravitational waves just like this permeate our galaxy.
Now, let’s come down from space to the South Pole, where millennia after millennia, neutrinos and other cosmic particles have been silently showering down the ice, barely interacting with normal matter if only to light a bright blue CCherenkov shine. Nowadays, those lights do not go unnoticed, but instead are observed by the IceCube detectors, which comprise many modules of light-capturing Digital Optical Modules (DOMs). IceCube detects these blue beeps from the ice, then, using what we know about how different particles behave in the icy environment, pick out the beeps that are from neutrinos. The next step is to trace back their paths – and finally, construct a new image of the Galactic Plane: purely from neutrinos! Perhaps many are familiar with the image of the Galactic Plane in different light frequencies. Some sources are brighter at one frequency than another, thus each frequency range provides a different set of information about what is out there. All of those little images layered up into an incredibly complex, beautiful, and saturated portrait of the universe that we co-exist in. And now, we have just another image of it – another unique layer to our understanding of the universe – specifically to probe the astrophysical objects that beams neutrinos out into space, and what message they have to tell us.
“I don’t know about NANOGrav, but IceCube did got a cake, for real…”
This occasion is made even more personal – albeit I did not play any role in producing these results – from the fact that I am working with IceCube this summer, through the SURF program! It’s so much funnier knowing that the two announcements collided on the same day when the IceCube Slack – together with a niche group of astrophysicists on Twitter – started to meme about this being the Barbie versus Oppenheimer of astronomy. On Thursday, the Wisconsin IceCube Particle Astrophysics Collaboration (WIPAC) office sat together in our big meeting room, aptly named Supernova, to watch the press conference together through Zoom. Watching a big announcement like this with a group of people is definitely more fun than watching it in a quiet room all by yourself. It’s like movie night but for science! We cheered loudly when professor Albercht Karle, who is often seen at the office with a smile and many jokes, appeared on the screen. It’s a little insane to see how close I am to the frontiers of science, as I am able to work with the people that helped to bring these findings to a reality. I myself am interacting with an incredible well of knowledge in the form of the people I see and work with everyday. Earlier that week, I had the chance to talk with someone who handles the backend of many IceCube simulations. Everyday, I work with my mentor, Dr. Wendt, who overlooks the design of the instrumentations, and there are so many things to learn from him and all of the other students working under him.
It’s surreal, going back to work after witnessing two scientific findings that open up new ways to see the universe: gravitational waves and neutrinos. It’s these moments that remind me how important my work is, how close it is – despite being such a small part – to humanity’s endless effort to understand our universe. At once I am both encouraged and humbled, but most of all, I feel the love of research burrowing itself deeper into my heart and my drive. This experience reminded me of what I have originally wanted to study astrophysics for: to reach just a little further into space and bring it closer to home.
Here I am in my little cubicle, hunching my back over codes and diagrams to design a testing procedure for photomultiplier tubes (PMTs), which will be used in the design for IceCube-Upgrade and IceCube-Gen2, the next iterations of improvement upon IceCube in the South Pole. It is a small, but vital, part of the process, to make sure that everything goes smoothly and once in the ice, the detectors will be functional and capable of picking up neutrino signals. In the future, may these PMTs be a part of scientific history, too.
