The closest star to Earth is called Proxima Centauri. It’s 4.243 light years from Earth. A light year is the distance light travels in a year. Light travels at 299800000 metres per second, so in a year it travels 299800000 x 365 x 24 x 60 x 60 = 9460000000000000 m. Therefore Proxima Centauri is about 40000000000000000 metres away! That’s 4 followed by 16 zeroes or 40 million billion.
Francesca’s right. In fact, astronomers have just finished using a space telescope called WISE to search for any even fainter stars that are even closer, but didn’t find any in the whole sky! So Proxima Centauri definitely is the closest.
The closest star to Earth is Proxima Centauri, which is about 4 light years from Earth. This gives you a really good idea of how big space is, because even though its the closest star to Earth it takes light (which is the fastest thing we know of) 4 years to get there!