What is a light-year and how is it used?? - NASA
A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 …
Just How Big is this Place - NASA
A light year is equal to 9,500,000,000,000 km and is the distance that light travels in one year. A light year can be expressed as 9.5 trillion km or in scientific notation as 9.5 x 10 12 km.
Does the Sun move around the Milky Way?? - NASA
Yes, the Sun - in fact, our whole solar system - orbits around the center of the Milky Way Galaxy. We are moving at an average velocity of 828,000 km/hr. But even at that high rate, it still takes …
Cepheids - NASA
Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. This behavior allows them to be used as cosmic yardsticks out to distances of a few tens of millions …
Supernovae - NASA
Supernovae At large distances (up to about 1 billion light-years), astronomers can no longer use methods such as parallax or Cepheid variables. At such large distances, the parallax shift …
Parallax - NASA
Astronomers derive distances to the nearest stars (closer than about 100 light-years) by a method called stellar parallax. This method that relies on no assumptions other than the geometry of …
StarChild: The Milky Way - NASA
Our Sun is a star in the Milky Way Galaxy. If you were looking down on the Milky Way, it would look like a large pinwheel rotating in space. Our Galaxy is a spiral galaxy that formed …
StarChild: Galaxies - NASA
Galaxies A light-year is the distance light travels in one year. It is 9.5 trillion (9,500,000,000,000) kilometers. The size of a galaxy may be as little as a thousand light-years across or as much …
StarChild: Glossary - NASA
L LIGHT YEAR The distance light can travel in one year, which is 9,500,000,000,000 kilometers. LUNAR MODULE The section of the Apollo spacecraft designed to land on the Moon. LUNAR …
StarChild: The Universe - NASA
The universe is a vast expanse of space which contains all of the matter and energy in existence. The universe contains all of the galaxies, stars, and planets. The exact size of the universe is …