Given that the Andromeda galaxy is about $163000$ $163000$ light years across and subtends about ${4.1}^{\circ}$ $4.1^@$ , approximately how many light years away is it?

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Answer 1 · 2017-03-28T22:05:58

Approximately $2.3$ $2.3$ million light years.

${4.1}^{\circ} = 4.1 \cdot \frac{π}{180} \approx \frac{1}{14}$ $4.1^@ = 4.1*pi/180 ~~ 1/14$ radians

So the approximate distance to Andromeda is:

$163000 \cdot 14 \approx 2300000$ $163000*14 ~~ 2300000$ light years

Given that the Andromeda galaxy is about 163000163000 light years across and subtends about 4.1∘4.1^@, approximately how many light years away is it?