One of the fascinating things about looking skyward at night is realizing that every time you look at a star, you're really seeing how it looked in the past. Light from celestial objects travels great distances before it reaches us.
Proxima Centauri is the nearest star to the Sun and seven times smaller than it. Even though light travels 300,000 kilometres in one second (or 186,000 miles in one second), light from Proxima Centauri still takes slightly more than four years to reach us. When you look at this star, you really see it as it was four years ago.
The vast distances between objects in the universe create unwieldy numbers when trying to describe them with kilometres or miles. Instead, we refer to a light year, which is the distance light travels in one year—9,460,800,000,000 kilometres (5,865,696,000,000 miles). It is much easier to say Proxima Centauri is 4.3 light-years away.
The Milky Way Galaxy is roughly 100,000 light years wide. Light from its distant parts can take tens of thousands of years or even longer to reach us. More than two million light-years away, the Andromeda Galaxy is the farthest object we can see with without a telescope.
Regulus, the brightest star in the constellation Leo, is much closer at 77 light years away. The name Regulus means “little king.” At a width of about three and a half times our Sun’s width, Regulus emits around 140 times more light.
When you search the sky for Regulus and the other stars of Leo, remember the story of Hercules and his famous quest to become immortal. One of his tasks was to fight a gigantic monster known as the Nemean lion.
The lion came to Earth as a falling star. It landed in
Corinth, ravaging the countryside and terrorizing everyone it saw. Hercules gathered his weapons and went to Corinth, hoping to discover the lion’s lair. He was searching an animal trail when a tremendous roar startled him from behind. Although he bravely fired arrows at the beast, they did not penetrate the lion’s thick hide. Hercules realized his weapons were not powerful enough to save him. The story of Hercules’ fight against the beast reveals how Leo came to be placed in the sky.
Leo is between Virgo and Cancer. You can also reach Leo by starting at the Big Dipper and following the pointer stars away from Polaris, the North Star, to the Lion.
-Leo is easy to find. The Lion’s head and forelegs make up an asterism called The Sickle, which looks like a backwards question mark. The star, Regulus, marks the Lion’s heart, while the bright star, Denebola, shows its tail.
-Watch for the Leonid meteor shower November 15-20. You can usually expect to see about 15 meteors per hour. In 1833, more than 100,000 meteors per hour were seen and in 1966, more than 100 per second were spotted in short bursts. The Leonid meteor shower becomes more intense every 33 years when the comet Tempel-Tuttle passes near Earth.