The picture on the preceding web page was developed to show that Alpha Centauri is not a star, however really a star system. The the three stars in the system, the dimmest - called Proxima Centauri - is actually the nearest star to the Sun. The two bright stars, dubbed Alpha Centauri A and also B type a near binary system; they are separated by only 23 times the planet - sun distance. This is slightly better than the distance in between Uranus and the Sun.

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The Alpha Centauri device is not visible from lot of the north hemisphere. The below image shows this star system and also other objects close to it in the sky.

### Distance Information

Proxima Centauri, the the next star to our own, is tho 40,208,000,000,000 km away. (Or around 268,770 AU.) once we talk around the ranges to the stars, we no much longer use the AU, or astronomical Unit; commonly, the light year is used. A light year is the distance light travels in one year - it is equal to 9.461 x 1012 km. Alpha Centauri A & B are approximately 4.35 light years far from us. Proxima Centauri is contempt closer in ~ 4.25 irradiate years.

### How do We Calculate distances of This Magnitude?

The techniques astronomers usage to measure distances to the stars are pieces of fundamental and active work in astronomy with important implications for just how we know the Universe approximately us.

among the many accurate methods astronomers usage to measure ranges to stars is called parallax. If you organize your finger in prior of her face and close one eye and look v the other, then switch eyes, you"ll check out your finger seem to "shift " v respect to more distant objects behind it. This is due to the fact that your eyes space separated from each various other by a couple of inches - so every eye sees the finger in front of you from a slightly various angle. The amount your finger seems to change is referred to as its "parallax".

Astronomers deserve to measure parallax by measure up the position of a surrounding star an extremely carefully with respect to an ext distant stars behind it, climate measuring those positions again 6 months later on when the earth is on the opposite side of the orbit. If the star is close enough to us, a measurable parallax will certainly be seen: the position of the star family member to the more distant background stars will have actually shifted. The change is small - much less than an arcsecond even for the nearest star. (An arcsecond is 1/60 of an arcminute, which is 1/60 that a degree.) (londonchinatown.org the universe has an ext information on calculating parallax.)

Image Credit: londonchinatown.org the Universe, NASA/londonchinatown.org

### Why are These distances Important to Astronomers?

Stars room not in reality stationary objects! The Galaxy is rotating, and also the stars room in orbit roughly its center. No every star moves at the same price - how rapid they orbit have the right to depend on where the star is located within the Galaxy. Our Sun, being reasonably far native the Galactic Center, takes end 200 million years to circle the Galaxy once. Some of the stars close to us room moving faster than us, and some slower. As Phil Plaitt, from poor Astronomy says, "...like cars on a highway, stars continually happen each other as castle orbit the Galaxy. They readjust positions, slowly, but measurably."

This animation by Frog rock Observatory reflects the motion of Barnard"s Star throughout the sky from 1985 come 2005. Barnard"s Star is approaching the sun so swiftly that around 11,700 AD, it will be 3.8 light years from the sun - and thus the closestly star come our own! (Garcia-Sanchez, et al, 2001)

### Travel Time

The Voyager 1 spacecraft is on an interstellar mission. That is traveling away from the sun at a rate of 17.3 km/s. If Voyager were to travel to Proxima Centauri, at this rate, it would take over 73,000 years to arrive. If we could travel in ~ the rate of light, one impossibility due to Special Relativity, it would still take 4.22 years to arrive!

### Why Can"t we Travel much faster Than the rate Of Light?

According to unique Relativity the mass of an object increases together its rate increases, and also approaches infinity as the object"s speed ideologies the rate of light. This means that it would take an unlimited amount of energy to accelerate an item to the speed of light.

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There"s no basic reason why us can"t acquire as close to the rate of light as we like, listed we have sufficient energy. But this is probably much in the future.