This morning, I received an email from Mia Holland, an editor of a German public broadcast outlet, which checks TikTok videos for their truthfulness and takes action against the spread of disinformation and fake news on social media.
Mia stated: “I’m currently working on a TikTok video concerning the exoplanet Proxima b. In the video, it is said that light-glow from Proxima b appears to pulsate regularly and might therefore indicate a technological civilization. We know that Proxima b is in the habitable zone and that the planet is exposed to flares from its host star, Proxima Centauri. But whether the explanation for the claimed “light pulses” made by the TikTok-Creator is true, remains unclear. As you have researched this planet, we are confident that you are the right person to contact with our set of questions.”
Below are Mia’s questions and my answers under each of them:
1. What kind of exoplanet is Proxima b and how Earth-like is it?
Proxima b is a rocky planet with a mass somewhat larger (by at least 7%) than that of Earth. It is located in the habitable zone of the nearest star to the Sun, Proximal Centauri. This implies that if Proxima b has an atmosphere, it could have liquid water on its surface, potentially enabling the chemistry of life-as-we-know-it. The star is fainter than the Sun by a factor of 640 and the planet is 20 times closer than the Earth is to the Sun, having an orbital period of 11.2 days instead of a year. If there are intelligent beings on Proxima b, then they celebrate their birthdays every 1.6 weeks. Proxima Centauri is a red dwarf star with 12% of the mass of the Sun. Its frequent flares and its wind could have stripped the atmosphere of Proxima b and sterilized the planet. It is unclear whether dwarf stars, which are much more abundant than the Sun, can nurture life on planets near them. We live next to a rarer quiescent star like the Sun, possibly for a good reason.
2. Is it correct that a “constant, faint glow” can be seen on Proxima b, which “pulsates regularly”, as the creator claims in the video?
Proxima Centauri is known to flare frequently. A recent study with the Atacama Large Millimeter Array (ALMA) found Proxima Centauri to brighten on time intervals as short as seconds and as long as years.
Just as with the Sun, these flares are likely accompanied by plumes of hot gas that could collide with the planet, Proxima b, and brighten it periodically. In addition, surface topography and spatial variations in geological composition could also modulate the reflectance of starlight from the planet’s surface and introduce short-term variability. Better spectral data from the Webb telescope and ground-based telescope could clarify the origin of the observed variability of glow of Proxima b.
3. Could stellar flares explain the Creator’s claim of pulsating light on Proxima b?
It is most likely that the pulsations are of natural origin as the flares from Proxima Centauri modulate the stellar wind which impacts the planet on timescales as short as seconds. The interaction would depend on whether the planet has a magnetosphere like the Earth. We do not know if Proxima b has an atmosphere or a magnetic field.
About five years ago, I wrote a paper with my summer intern, Elisa Tabor, on the detectability of city lights from Proxima b. However, possible natural interpretations for the detected variability must be considered first.
4. Proxima b is located in the habitable zone. How likely is it that complex life like on Earth exists there?
We do not know whether Proxima b hosts complex life at this time. We should seek better evidence to find out. Science is work in progress. We acquire new knowledge by collecting evidence from our telescopes, not based on opinions or conjectures.
5. Is it safe to say that complex life on Proxima b is impossible?
Complex life on Proxima b is possible. We could potentially send a probe that will land on Proxima b to find out. With existing chemical propulsion, the probe could reach Proxima b in 50,000 years and inform us whether there is life there. The mission requires patience as the timescale is comparable to the time elapsed since humans left Africa. If we develop faster propulsion in the next 50 millennia, we could send probes that would overtake older ones and get there earlier. The information about the findings of the probes will take 4.25 years to reach us at the speed of light. The probe will need to be equipped with artificial intelligence and act autonomously since it takes 8.5 years for a round-trip dialog with it at the speed limit of light.
The lack of evidence for complex life is not evidence for the absence of complex life on Proxima b. Complex forms of life may come and go episodically, punctuated by catastrophes, like a giant flare from the host star, an asteroid impact or a nearby stellar explosion.
The notion of fluctuations around a zero signal extends more broadly. In another email I was asked: “Is the concept of zero an adequate representation of “nothingness,” or does zero carry more significance than simply the absence of quantity? Is it possible to meaningfully quantify “nothing” without inadvertently introducing a form of existence?”
I explained that in quantum mechanics or statistical physics, zero could define the typical state of a quantity which is fluctuating. For example, the vacuum in quantum mechanics could have zero energy density but it fluctuates and makes virtual particles that appear and disappear. These particles could materialize in the presence of an electric field, leading to the phenomena of vacuum polarization, electron-positron pair creation, or the Casimir effect between conducting plates.
In the same way, complex life could have materialized episodically multiple times on each exoplanet, with the most common state being a rock devoid of technological signals.
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 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. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
