In 1895, Italian inventor and electrical engineer Guglielmo Marconi (1874-1937) produced the first human-made radio waves capable of traveling beyond the Earth, so radio evidence of the existence of human civilization has now traveled 128 light years from Earth. Assuming a stellar number density in the solar neighborhood of (7.99 ± 0.11) × 10−2 stars per cubic parsec1, Earth’s radio emissions have already reached about 20,000 star systems.
The most distant physical human-made object, however, is the Voyager 1 spacecraft, now over 160 AU from the solar system barycenter (SSB), a distance of almost 15 billion miles. That certainly sounds impressive by human standards, but that is only 0.0025 light years. As the distance of Voyager 1 from the solar system barycenter is constantly increasing, you’ll want to visit JPL Horizons to get up-to-date information using the settings below for your date range of interest. Delta gives the distance from the SSB to the Voyager 1 spacecraft in astronomical units (AU).
This still-functioning spacecraft that was launched on September 5, 1977, flew by Jupiter on March 5, 1979, and flew by Saturn on November 12, 1980, is now heading into interstellar space in the direction of the constellation Ophiuchus, the Serpent Bearer, near the Ophiuchus/Hercules border.
Given Voyager 1’s current distance (from Earth), a radio signal from Earth traveling at the speed of light would take 22 hours and 8 minutes to reach Voyager 1, and the response from Voyager 1 back to Earth another 22 hours and 8 minutes. So, when engineers send a command to Voyager 1, they won’t know for another 44 hours and 16 minutes (almost 2 days) whether Voyager 1 successfully executed the command. Patience is indeed a virtue!
Thanks to three onboard radioisotope thermoelectric generators (RTGs)2, Voyager 1 should be able to continue to operate in the bone-chilling cold of deep space until at least 2025.
In about 50,000 years, Voyager 1 will be at a distance comparable to the nearest stars.
1The Fifth Catalogue of Nearby Stars (CNS5)
Alex Golovin, Sabine Reffert, Andreas Just, Stefan Jordan, Akash Vani, Hartmut Jahreiß, A&A 670 A19 (2023), DOI: 10.1051/0004-6361/202244250
2At launch, the Voyager 1 RTGs contained a total of about 4.5 kg of plutonium-238, generating 390W of electricity.
It’s fun to see that even after 40 years, we are finally getting slightly closer to 1 light day away from Earth. Then see the distance to the nearest stars on the chart, we still have a LONG way to go!
I always find it fascinating that evidence of humanity has at gone at least 128 light years out – if there is a way to pick up the ‘noise’ from Earth from out there, that’s an interesting thought.
One of my favorite sci-fi movie openings (other than original Star Wars!) is the scene in Contact with the radio signals going way out into space.
Really cool chart of Voyager/star distance you shared, I haven’t seen that one before!
Clear skies!
-Tom
Thanks for your comments, Tom! I, too, was delighted by the chart showing Voyager 1’s distance and the nearest star distances in increments of 10,000 years. It was created in 2017 by Stern Fuchs. Here’s the link to the Wikimedia Commons page:
https://commons.wikimedia.org/wiki/File:NearSunStarsSimple.jpg
The better we know the parallax, radial velocity, and proper motion of each nearby star, the more accurate will be our predictions of where those stars will be in future decamillennia. I hope that Stern will be updating this graphic based on a later release of Gaia data when it becomes available. Right now, it looks like Alpha Centauri will lose its place as the nearest star system to Ross 248 in about 35,000 years or so.
On a more serious note, I think Earth needs to launch (soon!) a spacecraft into interstellar space that contains as much literature, music, art, etc. as can be carried on permanent digital media aboard the spacecraft, like a vastly scaled-up version of the Voyager Golden Record. A celestial time capsule. I am not optimistic that human civilization as we know it is going to be able to survive much longer without a world government with the wisest, most intelligent and compassionate people, in charge. Our current political systems do a really lousy job of electing lawmakers and leaders who are capable of effectively dealing with the many challenges we face. And for each of us as individuals, with freedom must come responsibility. Irresponsible, disrespectful behavior must have consequences. Much more to say on this topic, so a posting for another day.
Dave
P.S. Yes, Contact, what a great movie!
I totally agree on your “message in a bottle” (or rather a time capsule tossed over the side of our planet). Just watching the news this morning and hearing that John Kerry is talking with China and they refuse to clean up their act with pollution. Wonderful. Just another indication that we are working on putting ourselves on an endangered species list – along with all the other life on the planet that will go down with us.
The message idea reminds me of that Star Trek: Next Generation episode “The Inner Light” which was a similar situation with a civilization around a star that went nova. Put on you watch list if you haven’t seen that one. One of the best STNG episodes I think.
https://en.wikipedia.org/wiki/The_Inner_Light_(Star_Trek:_The_Next_Generation)
Then see what is going on with temperatures this summer, our on and off again smoke here in Wisconsin, and will anyone take notice?
Definitely some good ideas for another blog essay! — Tom
Ah, yes, The Inner Light is one of Star Trek’s finest hours (in all of Star Trek, not just STTNG). Glad you mentioned it, Tom!