How long does it take for the Sun's light to reach us?
My questions are. How long does it take for the light from the sun to reach the Earth, and other planets in the Milky Way? How far does the sun's light travel beyond our solar system? How much larger is the sun compared to the planets in our solar system? Thank you for your time.
The sun's light takes about 8 minutes to reach the Earth after it has been emitted from the sun's surface. The time it takes for light to reach planets in our Solar System (not the Milky Way, which is our galaxy) varies from about 3 minutes for Mercury, to about 5.3 hours for Pluto. There is nothing out in space to prevent the sun's light from going infinitely far, in principle. In practice, the sun is only 4.5 billion years old, so its light can only extend 4.5 billion light years away from us right now. But there's nothing to stop that light from expanding outwards forever, as time goes on. The sun's radius is about 100 times that of the Earth, meaning that about 1.12 million Earths could fit inside it, as could about 930 Jupiter's.
If it takes just over 8 minutes for the Sun's light to reach Earth, then if the sun were to suddenly extinguish, would we not know it until just over 8 minutes later?
This is correct. There's no reason for the Sun to suddenly turn off, but more generally, the light from flares or other stellar "weather" also takes 8 minutes to reach us.
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
- Why is looking out into space the same as looking back in time?
- Why can we see the sun's image before sunrise and after sunset?
- Do we really observe the edges of galaxies at different epochs?
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist
This page has been accessed 369419 times since September 6, 2002.
Last modified: June 18, 2010 10:01:47 AM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)