Within a billion years, NASA’s Voyager 1 probe will have reached the opposite side of the Milky Way disk to the Sun. By the time it arrives, the sun will have evaporated all of Earth’s oceans, making it habitable. As a result, NASA may not be on hand to celebrate this remarkable milestone in the journey of one of its most iconic spacecraft.
Last month I asked my brilliant student at Harvard, Shokhruz Kakharov, where the Voyager 1 spacecraft will be in a billion years. Using a detailed model of the Milky Way’s mass distribution, Shokhruz was able to map Voyager’s future orbit relative to the Sun over billions of years. The results will be included in a forthcoming peer-reviewed article.
This may all sound academic and not ‘down to earth’ anchored, as the adults in the room often pretend. But the reason for my question was down to earth. I even wondered this question because most stars formed billions of years before the sun. If the Voyager-like rockets had been used on exoplanets more than a billion years ago, the corresponding space probes could have reached the solar system anywhere in the Milky Way disk by now. We can observe these interstellar objects with our telescopes as they approach Earth.
In particular, linking an Earth-based telescope to the space-based Webb Telescope, a million kilometers away, will allow us to accurately locate the objects’ trajectory and detect any non-gravitational acceleration they exhibit. It would also be extremely sensitive to the detection of residual gases, either due to cometary evaporation of natural ice or engine exhaust. But even without surrounding gas, the Webb telescope can measure the surface temperature and size of the objects based on the infrared flux they emit. This would allow us to determine their reflection of sunlight within the Earth-Sun divide, as long as they are much larger than Voyager.
However, at Voyager’s scale, there is not enough sunlight reflected for our telescopes to detect these objects unless they arrive near Earth. In fact, if they were to collide with Earth, they would appear as interstellar meteors of unusual material strength and composition. Our next expedition to the location of the interstellar meteor IM1, which collided with Earth on January 8, 2014 and showed unusual material strength and composition, aims to find large pieces of that object and deduce its origin.
Shokhruz and I calculated the galactic orbits of all five probes launched into interstellar space by NASA to date, namely: Voyager 1, Voyager 2, Pioneer 10, Pioneer 11 and New Horizons. We also calculated the previous 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 have an artificial origin will be better answered as more of them are discovered. The most promising way to increase the current number of interstellar objects is with the Rubin Observatory in Chile, which will survey the southern sky every four days within a year with a 3.2 billion-pixel camera that arrived at the observatory just a week ago arrived. 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 needed to analyze the Rubin data. By following the orbits of interstellar objects and observing them with other telescopes, we hope to identify their likely origins and discover the nature of the environment from which they emerged.
For the same reasons that humans may not be present on Earth when Voyager arrives at the far side of the Milky Way, the senders of interstellar probes may not be present on their exoplanet due to the evolution of their older star when we receive these packets. in our mailbox near Earth. Even if these technological objects ceased functioning long ago, their existence would imply that there used to be other intelligent inhabitants of the Galaxy. Their waste is our treasure. Learning about their state of mind based on what they left behind is akin to studying ancient civilizations on Earth that no longer exist based on the relics we find at archaeological sites.
During a recent public appearance I was asked what I envision for the future of humanity. I explained that people arrogantly believe that they are important players on the cosmic stage. But the truth is that even at the provincial level of the Earth, life survived major catastrophes long before humans arrived on the scene, including global warming 252 million years ago that wiped out 96% of all marine species.
This gives hope that in the grand scheme of things, life on Earth will also survive human-induced environmental disasters. Another way of putting it is that microbes are more resilient than humans. In a billion years, human existence could be just a minor footnote in the cosmic playbook. To gain a more balanced perspective, we must seek out other actors on the cosmic stage and learn from them. And if none of them survived, we can study their history based on the artifacts they left behind.
We are not in a position to claim an important role in cosmic history. But the good news is that we can find out what happened on the cosmic stage and take pleasure in the fact that in a billion years our own Voyager will reach the far side of the Milky Way relative to the Sun. Isn’t this performance breathtaking?
Yes, we are short-lived, meter-scale creatures with major physical limitations, but we are so ambitious and fearless that we could send our message in a bottle to the other side of the Milky Way, 50,000 light years away, within a billion years.
Avi Loeb is the head of the Galileo Project, founder and director of Harvard University’s Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and former chairman 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 past chairman 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 co-author of the textbook ‘Life in the Cosmos’, both published in 2021. His new book, entitled ‘Interstellar’, was published in August 2023 .