Light year how many years

Earth is about eight light minutes from the Sun. A trip at light-speed to the very edge of our solar system — the farthest reaches of the Oort Cloud, a collection of dormant comets way, way out there — would take about 1. Keep going to Proxima Centauri, our nearest neighboring star, and plan on arriving in 4. To get a better sense, for instance, of the true distances to exoplanets — planets around other stars — we might start with the theater in which we find them, the Milky Way galaxy.

Our galaxy is a gravitationally bound collection of stars, swirling in a spiral through space. Groups of them are bound into clusters of galaxies, and these into superclusters; the superclusters are arranged in immense sheets stretching across the universe, interspersed with dark voids and lending the whole a kind of spiderweb structure. Our galaxy probably contains to billion stars, and is about , light-years across.

That sounds huge, and it is, at least until we start comparing it to other galaxies. Our neighboring Andromeda galaxy, for example, is some , light-years wide.

Another galaxy, IC , spans as much as 4 million light-years. In our galaxy of hundreds of billions of stars, this pushes the number of planets potentially into the trillions. A light-year is a measurement of distance and not time as the name might suggest.

A light-year is the distance a beam of light travels in a single Earth year, or 6 trillion miles 9. On the scale of the universe, measuring distances in miles or kilometers doesn't cut it. In the same way that you may measure the distance to the grocery store in the time it takes to drive there "The grocery store is a minute drive away" , astronomers measure the distances of stars in the time it takes for light to travel to us.

For example, the nearest star to our sun, Proxima Centauri , is 4. 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. How can this be? Light travels at a speed of , miles or , km per second. This seems really fast, but objects in space are so far away that it takes a lot of time for their light to reach us. The farther an object is, the farther in the past we see it. Our Sun is the closest star to us. It is about 93 million miles away. So, the Sun's light takes about 8.

This means that we always see the Sun as it was about 8. The next closest star to us is about 4. All of the other stars we can see with our eyes are farther, some even thousands of light-years away. Stars are found in large groups called galaxies. A galaxy can have millions or billions of stars. The nearest large galaxy to us, Andromeda, is 2.