**What is the exact measurement of a light-year?** In a vacuum, light travels at 670,616,629 mph (1,079,252,849 km/h). To find the distance of a light-year, you multiply this speed by the number of hours in a year (8,766). The result: One light-year equals **5,878,625,370,000 miles** (9.5 trillion km).

**What is 1 light-year equal to in Earth years?** Coe et al. For most space objects, we use light-years to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about **6 trillion miles** (9 trillion km).

**Is a light-year is a measurement of time?** **The light-year is a measure of distance, not time**. It is the total distance that a beam of light, moving in a straight line, travels in one year.

**Are light years in the past?** **Yes, you are correct**. Since Alpha Centauri is four light years away, you see it as it was four years ago. For example, if the sun was to suddenly disappear it would take eight minutes for us to see it disappear. The reason is that light takes eight minutes to travel from the sun to us.

## What is the exact measurement of a light-year? – Additional Questions

### How long would it take to travel 1000 light years?

To do so, you will need a speed of almost the speed of light, so in the reference frame of Earth, you will have spent just a tad more that 1000 yr to travel 1000 ly. i.e. **1000 years, 4 hours, and 23 minutes** in Earth’s reference frame.

### Is there a black hole 1000 light years away?

Back in 2020, researchers based at the European Southern Observatory (ESO) made an exciting announcement – they had found the closest ever black hole to Earth. **It was, according to the team led by Thomas Rivinius, lurking just 1,000 light-years away in a triple system dubbed HR 6819.**

### How many planets are in the Universe?

With 400 billion Milky Way stars, we estimate they contain **1-to-10 trillion** orbiting planets, total.

### How long would it take a rocket to travel 1 light year?

Saying we were a space shuttle that travelled five miles per second, given that the speed of light travels at 186,282 miles per second, it would take about **37,200 human years** to travel one light year.

### How many miles is 1000 light years away?

Astronomers say they have discovered a black hole that is closest to Earth, roughly 1,000 light years from our planet. A light year is the distance light travels in a year which is **5.9 trillion miles** (9.5 trillion km). Until now, the closest-known black hole was one perhaps three times further away, reports Reuters.

### What is 1000 light years away from Earth?

Astronomers have a new candidate in their search for the nearest black hole to Earth. It’s about 1,000 light-years away, or roughly **9.5 thousand, million, million km**, in the Constellation Telescopium.

### How long will it take to travel 1 light year at the speed of light?

A light year is the distance that light travels in vacuum in one year, about 6 trillion miles or 10 trillion kilometers. One might therefore conclude that in order to travel one light year at one tenth the speed of light, this trip would take **10 years**.

### How long is 500 light years away?

The planet is about 500 light-years away, or **2,939,249,910,000,000 miles**. The farthest we’ve ever sent humans is about 240,000 miles away (the moon), and the farthest we’ve ever sent an unmanned spacecraft is about 11,805,000,000 miles away (the Voyager 1 probe).

### How long would it take us to travel 100 light years?

If you wanted to travel 100 trillion light years away, you could make the journey in **62 years**. By the time you arrived, the Universe would be vastly different. Most of the stars would have died a long time ago, the Universe would be out of usable hydrogen.

### What is the closest Earth like planet to us?

**Proxima Centauri b** is the closest exoplanet to Earth, at a distance of about 4.2 ly.

### How many miles is the universe?

It’s about **238,855 miles** on average, and I say on average, because the distance does change.