Question

1. calculate what is the distance in kilometers from earth to a star that is 30 light - years away?

how do scientists measure distance to a star?
the distance between earth and the stars is too large to be measured in miles or kilometers. instead, scientists use a unit called a light - year. one light - year is the distance that light can travel in one year. one light - year equals 9.46 trillion kilometers.
as earth revolves around the sun, a large distance seems to move, but far - off stars do not. this is called parallax. scientists use parallax and math to find the distance between earth and stars. to understand parallax, think about riding in a car past a large mountain. as you drive past the mountain, it seems to move. however, the mountain is not actually moving. it is your motion compared to the mountain that makes the mountain seem to move.
stars, galaxies, and the universe
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Explanation:

Step1: Recall light - year conversion

One light - year is the distance light travels in one year, and it is equal to 9.46 trillion kilometers.

Step2: Calculate the distance

The star is 30 light - years away. Multiply the number of light - years by the distance of one light - year. So the distance $d = 30\times9.46\times10^{12}$ kilometers.
$d=283.8\times10^{12}$ kilometers $ = 2.838\times 10^{14}$ kilometers.

Answer:

$2.838\times 10^{14}$ kilometers