How long would it take to travel to the nearest star?
That depends on how much of a hurry you're in.
The nearest star to the Sun is a dim red star called Proxima Centauri. Only visible from the southern hemisphere, it's too faint to see without a telescope.
Proxima Centauri is 25 trillion miles from Earth. Traveling at the speed of light – roughly 670 million miles per hour – would get you there in a little over four years. If you left right now, you would arrive in early spring 2017.
Unfortunately, traveling at the speed of light isn't really an option yet. Warp drive – the faster–than–light engine seen in Star Trek – still only exists on paper. NASA physicists are just beginning to experiment with ideas on how to warp the fabric of space in such a way that could propel a ship faster than the speed of light. Until we figure out some exotic approach to spacecraft propulsion, which could take centuries, we're stuck going much, much, slower.
Sadly, hitching a ride on one of our current space probes wouldn't make the journey very practical. The fastest manmade object to leave the solar system is the Voyager 1 probe, launched in 1977. It's hurtling into interstellar space at 38,400 mph! If Voyager 1 were traveling to Proxima Centauri, it would take 70,000 years to arrive.
Flying in a jet would require a six million year flight. And if you were to drive to Proxima Centauri, at 70 mph, your trip would take more than 40 million years!
Let's try asking the question a slightly different way. How fast would we need to be moving to get to Proxima Centauri within a typical human lifetime? To get there in 80 years, we would need a spacecraft capable of traveling at over 37 million miles per hour! For a human to have any chance of visiting another star, she would have to be moving at seven percent of the speed of light.
But consider this: even if we did manage to solve the problem of getting to Proxima Centauri within a reasonable amount of time, we would have traveled only to the star next door. A beam of light needs 100,000 years to cross our galaxy. Traipsing around the stars is clearly going to take an astronomical effort. And an infinite amount of patience.
What is the most distant object visible to the naked eye?
It's the Triangulum Galaxy, nearly three million light-years away.
Triangulum is the second closest large galaxy to our own Milky Way. Pictures of Triangulum taken through very large telescopes reveal grand spiral arms twisting around like a pinwheel. The light in those photographs comes from nearly 40 billion stars. Forty billion may sound like a lot, but keep in mind that the Milky Way has almost five times that number!
Triangulum is one of only a couple of galaxies that can be seen without a telescope (on a moonless night far from city lights). In addition to timing and location, viewers must know exactly where to look. At this time of year, Triangulum is almost directly overhead, shortly after sunset. Named after the constellation in which it sits, this island universe looks no different than a very faint star.
If you do find the Triangulum Galaxy, here's something to think about: the light you're seeing took three million years to get here. When we look out into space, we are looking into the past. We don't see what's happening in Triangulum now. We're seeing what was going on before humans figured out how to use stone tools.
The Andromeda Galaxy is also visible without using any fancy equipment. Two-and-a-half million light-years away, it is the closest spiral galaxy to our Milky Way. Spiral galaxies get their name from bands of stars that twist around a central core. Appearing eight times brighter than Triangulum, Andromeda is also considerably easier to find, in a reasonably dark sky. It looks like a fuzzy star, and is directly over Telluride in early winter evenings.
But for a brief time on March 19, 2008, the naked eye could see even farther into the past. An exploding star – called a "gamma ray burst" – flickered into view for all of 30 seconds. Named GRB 080319B, the explosion became the most luminous object ever observed; it also grabbed the record as the most distant object ever seen by human eyes.
Shining with more energy than all the stars in Milky Way combined, the light from GRB 080319B took seven-and-a-half billion years to reach Earth. Coincidentally, the light arrived just hours after the death of the iconic science fiction author, Arthur C. Clarke. The lucky few who happened to be looking in the right direction at the right time could see a dying star halfway across the universe!
Because Andromeda and Triangulum sit high in winter skies of the northern hemisphere, this is a great time of year to go out and test your eyes – and the darkness of your sky – and see if you can find our galactic neighbors. So be sure to go out tonight and look up. You never know how far you'll be able to see!
Dr. Christopher Crockett is a science writer and astronomer at the U.S. Naval Observatory in Flagstaff, Ariz. He has spent the past several years looking for planets around young stars in our Galaxy. He is a frequent guest speaker with the Pinhead Institute.