Free Astronomy Magazine November-December 2026

NOVEMBER-DECEMBER 2026 ASTRO PUBLISHING cating, Lazio divides their possible presence into four categories: pas- sive probes, passive surface arti- facts, active probes, and active surface artifacts. Our five wander- ing probes fall into the first cate- gory because, when they reach other planetary systems, they will inevitably be inactive but still rec- ognizable (to potential aliens) as objects of non-natural origin. It’s not easy to predict how long they will remain recognizable, as numer- ous variables come into play, not all of which are well understood; much depends on the probes’ speed and the non-uniform density of inter- stellar dust. Nonetheless, reason- able simulations (which include the gravitational potential of the Milky Way) of the two Voyagers’ future suggest that 4-5 billion years will pass before they become indistin- guishable from interstellar matter. This is equivalent to saying that when the Sun, as a red giant, anni- hilates the Earth, a human artifact may still be able to provide infor- mation about its cre- ator. [Any reference to “V’ger” in Star Trek: The Motion Picture is purely coincidental!] Considering that Voy- ager 1 is traveling at 17 km/s (the fastest of the five probes), it could cross the galaxy twice from one end to the other before dis- appearing completely. If the “expiration date” of 4-5 billion years is universally valid for artifacts of the same type, one or more sol- id bodies in our Solar System could still host the vestiges of ancient alien technologies. Or those artifacts could A bove, a rendering of the dark comet 1I/ ʻ Oumua- mua, the first interstellar ob- ject discovered in our Solar System. The book that hy- pothesized its nature as an alien spaceship sold many copies! The author is a fa- mous astrophysicist from Harvard. [AI artwork] On the left, the interstellar comet 2I/Borisov imaged by the Hubble Space Telescope on October 12, 2019. [NASA/ESA] Below, the best-character- ized interstellar object, comet 3I/ATLAS, imaged by Hubble on November 30, 2025. [NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Ob- servatory). Image Process- ing: J. DePasquale (STScI)]