Every Thursday during the academic year, Harvard’s Institute for Theory & Computation (ITC) — for which I am privileged to serve as director, holds a luncheon that brings together about a hundred astronomers. This hour-long forum features four short presentations on the frontiers of astrophysics in front of an audience seated around a U-shaped table.
This Thursday, Mercedes Lopez-Morales described amazing early results from the Webb telescope which detected the spectral fingerprints of various molecules in the atmospheres of Jupiter-like planets as they transit their host star. The signals were far better than expected by the large team of astronomers who prepared for analyzing this data many years in advance of the launch of the Webb telescope. Their expectations were far more modest than the exceptional quality of the data that was ultimately delivered by the Webb telescope.
At the end of the fascinating presentation by Mercedes, I noted that these circumstances remind me of the LIGO team which prepared templates of gravitational-wave signals for many years, anticipating that these templates would be absolutely necessary in order to extract the signals out of the noise. To their surprise, the first gravitational wave signal detected on September 14, 2015, was booming far above the noise and did not require any template for verification. The signal was produced by the merger of two black holes with masses of roughly 35 and 30 times the mass of the Sun and resulted in a post-merger black hole of 62 solar masses. The energy associated with the missing 3 solar masses was radiated away in the form of a booming gravitational wave signal, easily detectable from a distance of a billion light-years.
There are two possible ways to interpret these circumstances: either astronomers are too conservative in their expectations or nature is kind to us. I tend to favor the latter, because many of the subsequent LIGO events were also associated with mergers of massive black holes that yield strong signals. This may be a hint for the unanticipated origin of booming signals from a natural process that selects massive black holes through their gravitational settling in the cores of star clusters, where they find each other and merge.
At the end of the ITC luncheon, the Nobel laureate Bob Wilson approached me and said: “You are absolutely right! In 1970, I led a team that made the first detection of a rotational spectral line of carbon monoxide (CO) in an astronomical source, including the Orion Nebula and other galactic sources. My team members were worried that the signal would be too weak for us to detect, but we discovered a huge signal instantly, as soon as we looked at the Orion Nebula. In retrospect, we could have used an antenna temperature of a million degrees and still detected this signal.” Subsequently, CO observations became the standard method of tracing cool molecular interstellar gas, and detection of CO was the foundational event for the fields of millimeter and submillimeter astronomy.
I rest my case. We should be grateful to nature for its many gifts. Here’s hoping that we are not missing too many of these gifts by refusing to search for the unknown through our telescopes.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021.