Interesting Facts About Stars & Galaxies

Distant Stars

• The stars that can be seen in the night sky are so distant that light takes a long time to move between them. To put this into perspective, the speed of light is 186,000 miles per second. The closest star to Earth, apart from the sun, is Proxima Centauri. This star is 4.2 light-years away, and light from Proxima Centauri takes more than four years to reach the Earth.

Number of Stars

• The number of stars in the universe is simply unknown. It is estimated that the Milky Way galaxy alone has more than 300 billion stars. Astronomers estimate that the universe is home to more than 100 billion other galaxies. It would be difficult to imagine the number of grains of sand on a single beach; however, there are more stars in the universe than all of the grains of sand on Earth.

Age of Stars

• Stars are generally between 1 billion and 10 billion years old. The universe itself is believed to be 13.7 billion years old. The oldest star yet recorded, HE 1523-0901, is thought to be 13.2 billion years old, almost as old as the universe itself. All stars have different lifespans, largely dependent upon the star's size. Large stars burn energy at a greater rate than smaller stars such as red dwarfs. Smaller stars, therefore, have a significantly longer lifespan than their bigger brothers.

Movement

• Each star, and each galaxy, is moving through space and therefore through the universe. Because of the "Big Bang's" effect---the supposed birth of the universe---everything is moving outward from a central point. Each spiral arm of our galaxy, the Milky Way, rotates at approximately 140 miles per second. The Milky Way is itself moving through space at more than 190 miles per second. Therefore, the Earth is sometimes traveling through the universe at approximately 330 miles per second. That means that each human being on the Earth is also traveling at this speed.

Galactic Distance

• Although the nearest star to Earth is a little more than four light-years away, the nearest galaxy to the Milky Way is 2 million light-years away. When humans look up into the night sky, the stars that can be seen are generally stars that are located within the Milky Way galaxy. The distances involved for intergalactic travel are so vast that humans cannot possibly hope to travel between galaxies unless, of course, a new discovery radically changes the way in which humans understand, and exist within, the universe.