# Physics Astronomy 問題!10點!

吾識做!!幫幫忙!!^^

1.

SN1987A was a supernova in the Large Magellanic Cloud,which is a nearby galaxy.The exploded star was surrounded by rins of gases.The angular radius of the inner ring was measured to be 0.834".Energetic radiation and particles were seen coming out from the core at the speed of light,lightening the inner ring.

a)

it took about 248 days for radiation to travel from the core to the inner ring. Find the radius of the ring in light years.

b)

Hence find the distance to the supernova in light years.

寫詳細D呀!!^^

tks soooooooooooooooooo much!!!^^

### 1 Answer

- 天同Lv 77 years agoFavorite Answer
(a) Since the radiation and particles coming out from the core are travelling at the speed of light, i.e. 3 x 10^8 m/s, distance travelled in 248 days

= (248 x 24 x 3600) x (3x10^8) m

= 6.418 x 10^15 m

Because 1 light-year = 9.461 x 10^15 m

Hence, radius of the inner ring = 6.418x10^15/9.461x10^15 light year = 0.6784 light year

(b) Given radius of inner ring = 0.834"

tan(0.834") = 0.6784/d

where d is the distance of the supernova

hence, d = 0.6784/tan(0.834") light-years = 1.68 x 10^5 light-years