The light you see from your computer is nanoseconds old. The light reflected from the surface of the Moon takes only a second to reach Earth. The Sun is more than 8 light-minutes away. For example, the galaxy M is located about If aliens lived in those galaxies, and had strong enough telescopes, they would see the Earth as it looked in the past.
They might even see dinosaurs walking on the surface. We have written many articles about the Sun for Universe Today. Source: NASA. When astronauts orbited the Moon and later walked on its surface in the 's, television viewers noticed that they were slow to answer questions transmitted from Earth. That was because it took 1. Those 2. Not much changes about the Sun in so short a time, but it still means that when you look at the Sun, you see it as it was 8 minutes ago.
Photo Photo of the Sun in hydrogen-alpha light. The giant planet Jupiter , whose large moons Galileo discovered with his "trouble-making" telescope, is more than 5 times farther from the Sun than the Earth is. We see a planet like Jupiter because its light—which like the other planets and the Moon originates on the Sun—takes about 43 minutes to reach Jupiter.
The return trip to the Earth can take from 35 to 52 minutes, depending on whether we are on the same side of the Sun as Jupiter or on the other side.
Little Pluto is so small and remote it was not discovered until , orbits 40 times farther from the Sun than we do.
By the time the light reaches us, it has spread out so much that the planet looks very dim, and requires a good telescope to spot. Moving beyond the Solar System, our scale of distances and travel times needs to change.
Now light will require years , not hours, to make its way to us. The star that is nearest to the Sun happens to be part of a system of three stars. Unlike the Sun, which is a loner, many stars are found in groups of two, three, four or more. The brightest star in our neighbor system is called Alpha Centauri pronounced Al' fa Sen' to ree , and it is a virtual twin of the Sun.
Light from Alpha Centauri takes more than 4 years to reach the Sun. Astronomers use a special term for this way of measuring distance—they say the star is 4 light years away. The brightest star in our skies is the "dog star", Sirius pronounced Sea' ree us. It's the primary star in the constellation of the big dog, Canis Major. Sirius is roughly 9 light years away.
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