Driving the field towards astrophysics of the early universe
Kary Mullis was driving his car up the Northern California coast late one Friday night in the spring of 1983. His girlfriend lay asleep in the seat next to him. As he drove on the dark highways he wrestled with a scientific problem. His lab was able to make small pieces of DNA but they couldn’t construct rare sections of DNA, such as specific genes. He dreamed up a sophisticated technique where he could use the natural ability of DNA to bind its complement in order to produce infinite copies of a piece of DNA. A scientist more advanced in the field would never suspect this would work. After all, the human genome is composed of 3 billion base pairs; surely such complexity would never allow specific binding in the way that Kary imagined it. Kary was a young scientist and able to invent what seemed impossible. Polymerase chain reaction or PCR was born. This one technique would radically change molecular biology and modern forensics.
Three decades later, another young scientist was driving down the Southern California coast late at night. Much like Kary, Jeff Cooke pondered an entirely new technique; one that lay far afield from current research in astronomy. On his 2-½ hour commute, driven late at night, Jeff imagined a new way to detect the death of distant stars.
A supernova, an exploding, dying star, is one of the brightest objects in the universe. It can be seen from billions of light years away. Astronomers search the sky, monitoring thousands of galaxies, in the hope of finding a single supernova. In the supernovae field, as soon as the telltale signs of intensity are confirmed, scientists drop everything and rush to publish. They know that their sighting will fade in a few weeks. Jeff dreamed up an entirely new way of detecting supernovae based on the fundamental properties of space and time.
His idea was to utilize the fact that space stretches with time to lengthen the search for ancient supernovae. To borrow a common metaphor, the universe is like a balloon, where the dots drawn on the plastic outer layer stretch further apart as the balloon fills with air. As the balloon fills, the gas molecules inside the balloon are also pushed further apart, similar to how time is expanding along with space. This means that the farther away we detect these supernovae, the farther they are separated from us not only in distance but also in time. This means that if we can search far enough, we can detect exploding stars that are not only billions of light years away but also those that make up the creation of our universe. Incredibly, the technique that Jeff has honed is capable of detecting the death of the first stars. That’s right, we’re talking about the Big Bang.
Jeff’s idea, that supernovae could be measured over long periods of time and space seemed outrageous to colleagues. In order to accomplish this, he had to develop a novel technique. Jeff and his colleagues stacked images taken over and over again from 4 spots in the sky over the course of 5 years. It was a radical move in a field that typically measures supernovae in weeks not years. Using this method, they have effectively bridged space and time, giving us a glimpse into the early events of our universe. This technique was first published in Nature in 2009.
The past few years have uncovered a new type of supernovae identified as superluminous. These supernovae are, as Jeff explains, “ridiculously bright.” They are up to 100x brighter than their normal supernovae counterparts. Physicists in the 1960s hypothesized that these giant supernovae could be formed when the core of a massive star is no longer producing enough energy to compensate for the inward pull of gravity, a theory called pair-instability (nice explanation here). Because of its vast size, the pressure is similarly immense; the star spectacularly collapses, becoming easier to see from great distances. This model remained a theory until earlier this month when Jeff and his collaborators’ published two examples of pair-instability superluminous supernovae in Nature. These two new supernovae exploded 10 and 12 billion years ago. Jeff has found the most distant, and therefore the oldest, supernovae known. Jeff’s data indicates that these massively bright supernovae may be common in the early universe.
When discussing the early development of his technique, Jeff worries about a lack of interaction in the field, saying there’s “not as much communication between disciplines as there should be.” This is certainly a common theme in many scientific fields. We all know it’s easy to become insulated in your own lab, much less your area of expertise. Stories like Jeff’s show why it’s so important we work across disciplines to make sure early career scientists are encouraged to follow what sometimes seem like crazy ideas.
Jeff, who is now a research fellow in Australia, no longer has such a long commute, except when he visits the observatory. He travels to Hawaii often, working at the CFHT telescope in Hilo that has provided him with such provocative data. Talking about the research he’s performing now, Jeff gets excited. Working with his students, Jeff has very preliminary hints that they may now be detecting the death of the first stars of the universe. Will these observations lead to our greater understanding of the creation of the universe? Only time will tell.