Within a billion years, NASA’s Voyager 1 probe will have reached the opposite side of the Milky Way disk from the Sun. By the time it arrives, the Sun will have boiled all of Earth’s oceans, making it habitable. As a result, NASA might not be there to celebrate this remarkable milestone in the journey of one of its most iconic spacecraft.
Last month, I asked my brilliant Harvard undergraduate, Shokhruz Kakharov, where the Voyager 1 spacecraft would be a billion years from now. Using a detailed model of the Milky Way’s mass distribution, Shokhruz was able to plot Voyager’s future orbit relative to the Sun over billions of years. The results will be presented in an upcoming peer-reviewed article.
All this may seem academic and not grounded “on earth”, as the adults in the room often claim. But the reason for my question was down to earth. I actually asked myself this question because most stars formed billions of years before the Sun. Therefore, if Voyager-type rockets had been used on exoplanets more than a billion years ago, the corresponding space probes could have reached the solar system from anywhere in the Milky Way disk. We can observe these interstellar objects with our telescopes as they pass near Earth.
In particular, combining a ground-based telescope with the Webb Space Telescope, located a million kilometers away, will allow us to precisely locate the trajectory of objects and detect any non-gravitational acceleration they exhibit. It would also be extremely sensitive to detecting trailing gases resulting from cometary evaporation of natural ices or engine exhaust. But even without surrounding gas, the Webb telescope can measure the surface temperature and size of objects based on the infrared flux they emit. This would allow us to determine their reflectance of sunlight in the Earth-Sun separation, provided they are much larger than Voyager.
However, on the scale of Voyager’s size, there is not enough reflected sunlight for our telescopes to detect these objects unless they arrive close to Earth. Better yet: if they were to collide with Earth, they would appear as interstellar meteors of unusual strength and material composition. Our next expedition to the site of the interstellar meteor IM1, which collided with Earth on January 8, 2014 and showed unusual strength and material composition, aims to find large pieces of this object and deduce its origin.
Shokhruz and I calculated the galactic orbits of the 5 probes launched so far by NASA into interstellar space, namely: Voyager 1, Voyager 2, Pioneer 10, Pioneer 11 and New Horizons. We also calculated the past trajectories of the two interstellar meteors, IM1 and IM2, as well as the interstellar object `Oumuamua and the interstellar comet Borisov.
The fundamental question of whether any of the interstellar objects detected near Earth are of artificial origin will be better answered as more objects are discovered. The most promising way to increase the current sample of interstellar objects is that of the Rubin Observatory in Chile which, within a year, will study the southern sky every 4 days with a 3.2 billion camera. pixels arrived a week ago at the observatory. With its unprecedented sensitivity, the Rubin Observatory could find an interstellar object every few months. With my postdoc, Richard Cloete, we are developing the software necessary to analyze the Rubin data. By tracing the orbits of interstellar objects and observing them with other telescopes, we hope to identify their likely origin and understand the nature of the environment that gave rise to them.
For the same reasons that humans might not be present on Earth when Voyager arrives on the other side of the Milky Way, interstellar probe transmitters might not be present on their exoplanet due to the evolution of their older star when we receive these packages. in our mailbox near Earth. Even if these technological objects stopped functioning long ago, their existence would imply that there were other intelligent inhabitants of the Milky Way. Their waste is our treasure. Knowing their state of mind from what they left behind is equivalent to studying ancient civilizations on Earth that no longer exist from the relics we recover from archaeological sites.
At a recent public appearance, I was asked what I envision for the future of humanity. I explained that humans arrogantly believe that they are important players on the cosmic stage. But the truth is that even on the provincial scale of Earth, life has survived enormous catastrophes long before humans arrived, including global warming 252 million years ago that wiped out 96% of all marine species.
This gives hope that, overall, life on Earth will also survive human-triggered environmental disasters. In other words, microbes are more resistant than humans. In a billion years, human existence may be nothing more than a minor footnote in the cosmic playbook. To have a more balanced perspective, we must seek out other players on the cosmic stage and learn from them. And if none of them survived, we can study their history from the artifacts they left behind.
We are not able to claim a major role in cosmic history. But the good news is that we can understand what happened on the cosmic stage and appreciate the fact that our own Voyager will reach the other side of the Milky Way from the Sun in a billion years. Isn’t this achievement breathtaking?
Yes, we are ephemeral meter-scale creatures with major physical limitations, but we are so ambitious and fearless that we can send our message in a bottle to the other side of the Milky Way, 50,000 away. light years, in less time. a billion years.
Avi Loeb is the leader of the Galileo project, founding director of the Black Hole Initiative at Harvard University, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and former chair of the Department of Astronomy at the Harvard University (2011). -2020). He is a former member of the President’s Council of Advisors on Science and Technology and former chairman of the Council on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and co-author of the textbook “Life in the Cosmos,” both published in 2021. His new book, titled “ Interstellar,” was released in 2021. August 2023.