Stars in the universe

STARS

When we look at stars in the night sky, we are looking back in time. Many stars formed millions, if not billions, of years ago. furthermore , the starlight that reaches our eyes left those faraway stars sometime ago-ranging from a few minutes ago(the sun) to four years ago(Alpha Centauri, the suns nearest star neighbor) to a much longer time ago (objects at the edges of our galaxy).

We measure these distance in light years. one light year is equivalent to approximately 6 trillion miles, or the distance light travels in 365-day Earth year. Alpha Centauri, at 25 trillion miles from earth , is about 4 light years away. the light we see today from the Andromeda Galaxy lest it two and a half millions year ago: Andromeda is 2.5 million times 24 trillion miles away. Stars, which are balls of gas(mostly the gases hydrogen and helium), emit radiation. They create energy by fusing hydrogen and turning it an helium in their cores . We see resulting energy as starlight.

FAST FACTS

A neutron star ten miles in diameter could have more mass than three stars comparable in size to our sun.