Starship Asterisk*

Your math is correct, and although the idea and thought process is simple, I think the error lies in resolution.

First off, I thought NGC 5005 was 5.8' x 2.8'.
This arc angle is probably measured by a much more finer detail image, therefore making the one we see not as accurate. I.e, blur/glow can be misinterpreted as actual arc length of the galaxy.
Then, the bigger thing is what you are considering to be the comet. The seemingly 6-8 arc minute image must be a reflection of ice and dust and distortion well outside the radius of the actual comet body.


Comet tails can be quite long.

Hi,

Can someone who understands basic trig help me please?

For kicks, I thought I'd try to calculate the sizes of the comet & galaxy in APOD 10/19/06 based on apparent diameters and distances. But I'm clearly doing someting wrong:

I thought the tangent of half the apparent diameter (angle) would be qual to half of the true diameter divided by the distance.

I was thinking: right triangle ABC with the Earth at A and the right angle and center of the comet at C. tan = opposite over adjacent.

If the galaxy is 6.5' in diameter, then the comet (not including tail) is maybe 8', right?

So I did: tan(8/(60*2)) = (x / 2) / 9 light minutes

I used excel so converting the angle to radians:

Tan(Radians(1/15)) = x / 9*2

x = 0.001164 * 18 = 0.020944 light minutes

and then

0.020944 * 60sec/min * 186,000mi/sec = 234,735 miles!

... which seems way too big.

Thanks,
B