The New Sun Heading Our Way, How Do They Calculate It's Size?

[greg_68]

For all you boffins out there in the Galaxy world.......no pun intended....ok it was then.

 

There is a new Sun that is reported to be heading our way. :D hurrah warmer summers...for a short while anyway....then very warm summers......mmmmmm Ebay......choc ice sales......millionaire Rodney :D

 

It say's in the paper it is 6 million/billion whatever times bigger than our own Sun.

 

Question for you boffins out there cuz it's giving me a headache now. ;)

 

How can you tell how big something is that is so far away.

 

I understand how to measure the diameter of a distant object as long as you know the distance to it using angles and all that.

 

But if you don't know how far away it is how is this possible. :D

 

I assume that we must be able to measure how far away this new sun is from Earth.

 

Can anyone explain how any of this is done...in simple terms.

[mumof4]

magnification???i dunno!!lol.......maybe if they know what the magnification is they can tell how big an object is.to early!!!

 

 

ah here is nik..he can tell you!!

 

 

 

 

wow..gonna be a biggie!!

[NikpV]

I assume that we must be able to measure how far away this new sun is from Earth

 

For distances less than 500 light years we can use a parallax method, eg angle measured to stellar object against the backgroud of more distant stars from either side of the earths orbit

 

try this for the principle - Hold your right forefinger out an arm's length in front of you; keep it in that position. Close your left eye and look at your finger against a distant background. Now open your left eye but close your right and look at your finger. The finger appears to jump to the right. That's parallax.

If we know the distance between your two eyes and the angle between the two lines of sight to your finger, we can calculate the distance to your finger.

 

I understand how to measure the diameter of a distant object as long as you know the distance to it using angles and all that.

there you go then.

 

This might not be the method used to find its size. The size of a star and its place in its life cycle determin how hot the star is, and so by looking at its spectra we can see how far along its life cycle it is and it will also tell us its temperature - we can then look it up on a hertzsprung - russel diagram. Incidentally looking at at how far its spectral lines are shifted from the expected position (eg. known lines of hydrogen) we can tell its relative speed to us. (Stand on pavement and listen to how the tone of a siren on a police car changes as it approaches and recedes.)

 

oops forgot to say - larger stars are more blue/hotter ;)

 

thanx mo4

[greg_68]

Cheers Nik, I just knew there would be an easy explanation to it all ;)

 

p.s may regret asking but how do you know if it is more than 500 light years away

[NikpV]

ahh I was hoping you'd ask that ;) for that we rely on my second method to calculate the stars intrinsic brightness, we can observe its apparent brightness and use the formula below to calculate distance

 

 

apparent brightness = intrinsic brightness / (distance)

[mumble_bee]

I love how you hid redshift in the "apparent"

 

man you're a good teacher

[NikpV]

I love how you hid redshift in the "apparent"

 

man you're a good teacher

:P :P :16:

[Guest pepi]

I love how you hid redshift in the "apparent"

 

man you're a good teacher

:P :16: :D

 

funny how these boffins at nasa know all this si fi stuff but when it comes to the easy stuff they struggle. e.g they spent 10 million dollars making a pen that would right upside down in zero gravity and the russians used a pencil :P

[Bigjeeze]

Can you not measure the distance by reflection light or radiation? Or am I thinking of something else.

 

ALso I though the Poice siren coming & going was the doppler effect?

 

Maybe I need to go back to school!!! :P

[NikpV]

Can you not measure the distance by reflection light or radiation? Or am I thinking of something else.

 

ALso I though the Poice siren coming & going was the doppler effect?

 

Maybe I need to go back to school!!! :P

 

 

depends on how far away - eg 5 light years would take 10years to get a reply and the attenuation would be extreme - would have to be an extremly 'bright' radiation source to get a reflection - in the case of a luminous body (emitting its own radiation) the chances of getting the return signal is zero

 

ALso I though the Poice siren coming & going was the doppler effect?

 

yes the redshift is to light what the doppler effect is to sound

[El Dingo]

Oh Poo!

 

I go away for a few days and Nik beats me to an answer that contains the word 'Parallax'.

 

:P