The Ring Nebula in the constellation Lyra has an angular size of 1.2 arcmin x 1.2 arcmin.?

It is expanding at the rate of about 20 km/s. Approximately how long ago did the central star shed its outer layers? Assume that the nebula is 2,700 ly from Earth.The Ring Nebula in the constellation Lyra has an angular size of 1.2 arcmin x 1.2 arcmin.?未= angular diameter

d= linear diameter

D=distance

for large D:



未 = d/D in radians or 未 = (d/D) 57.3 for degrees, let's see, you're in arcmins so mult. that by 60 or 未 = (d/D)3438.



you're solving for current linear diameter: 未/3438 = d/D or D未梅3438 = d, subst. given values and it looks like d = .9424 l.y. multiply by 9.4605284 脳 10鹿虏 gets you to current kilometers: 8915601964160 km! Assuming 10 x sun's diameter for the star's orig. diam. that's still only 13 million kilometers original diameter, you may as well calculate from zero. Divide 8,914,655,911,320 by 20km/s and you get it happened 445,780,098,208 seconds ago. 31,557,600 seconds in a 365.25 day year so divide by that for about 14,125 years ago - about the Stone Age.