Extremely far. If you could travel at the speed of light, it would still take you 1,000 years to go that distance. (1000 light years = 5.87849981 × 1015 miles).
For shorter distances, out to a few hundred light years or so, we can measure the distance with trigonometry and parallax. Look at the object today, and compare the background stars. Look at it again...
They really are not comparable. Light travels 186,000 miles per second, and one AU is about 8.3 light-MINUTES. You can probably do the math, from minutes to hours to days to years as well as I can....
A light year is a measure of distance, not velocity. It is the distance light travels in one year's time in the vacuum of space. This equates to 5,865,696,000,000 miles. This means that an object...