Within a billion years, NASA’s Voyager 1 probe will have reached the opposite side of the Milky Way’s disk from the Sun. By the time it arrives, the Sun will have boiled off all the oceans on Earth, making it habitable. As a result, NASA may not be around to celebrate this incredible milestone in the journey of one of its most iconic spacecraft.
Last month, I asked my brilliant undergraduate student at Harvard, Shokhruz Kakharov, where the Voyager 1 spacecraft will be in a billion years. Using a detailed model for the mass distribution of the Milky Way galaxy, 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 paper.
All this may sound academic and not anchored “to the ground” as the adults in the room often claim. But the reason for my question was down to Earth. Actually, I wondered this question because most stars formed billions of years before the Sun. Therefore, if Voyager-like rockets were used on exoplanets more than a billion years ago, then relevant space probes could have reached the solar system by now from anywhere within the Milky Way’s disk. We can observe these interstellar objects with our telescopes as they pass by Earth.
In particular, pairing an Earth-based telescope with the space-based Webb telescope a million miles 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 the detection of trace gases either as a result of cometary evaporation of natural ice or exhaust gases from an engine. 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 reflection of sunlight within the Earth-Sun separation as long as 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 get close to Earth. Better yet – if they collided with Earth, they would appear as interstellar meteors of unusual strength and material composition. Our next expedition to the site of the interstellar meteorite, IM1, which collided with Earth on January 8, 2014 and displayed unusual strength and material composition, aims to find large parts of that object and ascertain its origin.
Shokhruz and I calculated the galactic orbits of all 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 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 discovered near Earth are of artificial origin will be better answered once more of them are discovered. The most promising way to increase the current sample of interstellar objects is with the Rubin Observatory in Chile, which within a year will survey the southern sky every 4 days with a 3.2 billion pixel camera that just arrived a week ago at the observatory. With its unprecedented sensitivity, the Rubin Observatory can find an interstellar object every few months. With my postdoc, Richard Cloete, we are developing the software needed to analyze Rubin’s data. By tracking the orbits of interstellar objects and observing them with other telescopes, we hope to identify their possible origins and understand the nature of the environment that gave birth to them.
For the same reasons that humans may not be around on Earth when Voyager reaches the far side of the Milky Way, the senders of any interstellar probes may not be around on their exoplanet due to the evolution of their star. older when we receive these packages. to our mailbox near Earth. Even if these technological objects ceased to function long ago, their existence would imply that there were once other intelligent inhabitants of the Milky Way. Their trash is our treasure. Learning about their state of mind from what they left behind is equivalent to studying ancient civilizations on Earth that no longer exist, based on the relics we find at archaeological sites.
In a recent public appearance, I was asked what I foresee for the future of humanity. I explained that humans arrogantly believe that they are important actors on the cosmic stage. But the truth is that even on Earth’s provincial stage, life survived major catastrophes long before humans came onto the scene, including a global warming event 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-caused environmental catastrophes. Another way of saying it is that microbes are more resilient than humans. In a billion years, human existence may be a minor footnote in the cosmic playbook. To have a more balanced perspective, we need to look for 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 unable to claim a major role in cosmic history. But the good news is that we can understand what happened on the cosmic stage and find satisfaction in the fact that our Voyager will reach the other side of the Milky Way from the Sun in a billion years. Doesn’t this achievement take your breath away?
Yes, we are short-lived creatures with great 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 thousand light years away, within a billion years.
Avi Loeb is 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 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 former chairman of the Board of Physics and Astronomy of the National Academies. He is the best-selling 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. His new book, titled “Interstellar,” was published in August 2023.