Saturday, May 3, 2014

How Far Is A Light Year in Miles Or Kilometers?

How Far Is A Light Year in Miles Or Kilometers?:

The NASA/ESA Hubble Space Telescope has captured this vivid image of spiral galaxy Messier 77 — a galaxy in the constellation of Cetus, some 45 million light-years away from us. The streaks of red and blue in the image highlight pockets of star formation along the pinwheeling arms, with dark dust lanes stretching across the galaxy’s starry centre. The galaxy belongs to a class of galaxies known as Seyfert galaxies, which have highly ionised gas surrounding an intensely active centre. Credit: NASA, ESA & A. van der Hoeven

The NASA/ESA Hubble Space Telescope has captured this vivid image of spiral galaxy Messier 77 — a galaxy in the constellation of Cetus, some 45 million light-years away from us. The streaks of red and blue in the image highlight pockets of star formation along the pinwheeling arms, with dark dust lanes stretching across the galaxy’s starry centre. The galaxy belongs to a class of galaxies known as Seyfert galaxies, which have highly ionised gas surrounding an intensely active centre. Credit: NASA, ESA & A. van der Hoeven
We hope you have a big suitcase if you’re planning a trip across the cosmos. At the speed of light — a speed that no technology yet can achieve — it would take you about four years to get to the Alpha Centauri star system, the nearest group to our own. Zipping to the nearest galaxy, the Canis Major Dwarf Galaxy, would take you about 25,000 light-years.

As the phrase “light year” implies, that’s the distance that light travels in a year. It’s as fast as anything can travel, at least as best as we can understand it. Sometimes referred to as a “cosmic speed limit“, going as fast as light (or even faster) is impossible for a physical object, according to Albert Einstein’s measurements a century ago. As you get faster and faster, he showed, your mass increases to infinity. But there’s still discussion around that.

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