In our galaxy of hundreds of billions of stars, this pushes the number of planets potentially into the trillions. Many of these are small, rocky worlds that might be at the right temperature for liquid water to pool on their surfaces. The nearest-known exoplanet is a small, probably rocky planet orbiting Proxima Centauri — the next star over from Earth.
A little more than four light-years away, or 24 trillion miles. If an airline offered a flight there by jet, it would take 5 million years. Not much is known about this world; its close orbit and the periodic flaring of its star lower its chances of being habitable. And computer modeling shows some have a good chance of being watery — or icy — worlds.
In the next few years, we might learn whether they have atmospheres or oceans, or even signs of habitability. One of the most distant exoplanets known to us in the Milky Way is Keplerb. Traveling at light speed, it would take 3, years to get there. Or 28 billion years, going 60 mph.
Unlike the speed of your car when running errands, the speed of light is constant throughout the universe and is known to high precision.
To find the distance of a light-year, you multiply this speed by the number of hours in a year 8, The result: One light-year equals 5,,,, miles 9. At first glance, this may seem like an extreme distance, but the enormous scale of the universe dwarfs this length.
Measuring in miles or kilometers at an astronomical scale would be extremely cumbersome and impractical. Starting in our cosmic neighborhood, the closest star-forming region to us, the Orion Nebula, is a short 7,,,,, miles away, or more simply, 1, light-years away.
The center of our galaxy is about 27, light-years away. The nearest spiral galaxy to ours, the Andromeda galaxy, is 2. Some of the most distant galaxies we can see are billions of light-years from us. Get Word of the Day daily email!
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