Orion Explosion?

[britnik]

I tried every half hour or so but the clouds never lifted

I doubt though that, from my garden in Wokingham, I would have counted any more than 7 or eight.

Lesson learned though
1) Keep an eye on WAB astronomy forum for news of events like this.
2) Counting naked eye visible stars in known constellations is a simple but excellent method to determine conditions that I will use more often
3) Looking at the sky more interesting than Wild at Heart

[wizzo]

Wow! I can't wait!

[Wagstaff]

Originally Posted by artdemole

Star is 600 light years away.

According to "The Sky At Night", Betelgeuse is 400 light years away. So we are seeing it now as it was in 1611. This was the year when the word "telescope" was first used.

Wagstaff

[nytecam]

Originally Posted by Wagstaff

According to "The Sky At Night", Betelgeuse is 400 light years away. So we are seeing it now as it was in 1611. This was the year when the word "telescope" was first used.Wagstaff

The telescope was invented in 1608 and pointed skywards by Gallileo the following year. 400 is a rather 'round' number and the distance of 'nearby' stars isn't know to that accuracy - Wikipedia states distance as 643LY ± 146LY so put the champagne on ice

[Wagstaff]

Originally Posted by nytecam

Wikipedia states distance as 643LY ± 146LY so put the champagne on ice

So, according to Wikipedia, the distance to Betelgeuse could be anything between 497LY and 789LY. That's a huge difference. So how accurate are all the other measurements to "nearby stars"? Indeed, how are the measurements taken in the first place?

Wagstaff

[pressld2]

Originally Posted by Wagstaff

Indeed, how are the measurements taken in the first place?

Parallax, using the width of Earth's orbit as a baseline. You observe the star on two dates six months apart and note the shift in its relative position compared to the very distant background stars. This tells you by what angle (how many degrees or, more liklely, fractions of a degree) it has appeared to move when the Earth is on opposite sides of the sun. Then it's a simple matter of geometry. This method only works for close stars as anything beyond a certain distance the angle is too small to measure. It also relies on having an accurate measurement of the size of Earth's orbit around the sun.

The distance of the further stars and galaxies is measured using the red-shift caused by the expansion of the usniverse. The further away they are the more their light is shifted towards the red end of the spectrum.

Neither method is an exact science, hence the ± error bars.

Dave P.

[Wagstaff]

Originally Posted by pressld2

Parallax, using the width of Earth's orbit as a baseline. You observe the star on two dates six months apart and note the shift in its relative position compared to the very distant background stars. This tells you by what angle (how many degrees or, more liklely, fractions of a degree) it has appeared to move when the Earth is on opposite sides of the sun. Then it's a simple matter of geometry. This method only works for close stars as anything beyond a certain distance the angle is too small to measure. It also relies on having an accurate measurement of the size of Earth's orbit around the sun.

Hmmm, thank you for the explanation, Dave - I think !!
I hadn't realised that there was such a margin of error in these measurements. Are we likely to see more accurate methods developed in the future?

Wagstaff

[artdemole]

The future changes every day. Tomorrow We may know more.It takes an age to find these things out and even then it will be reputed.

[nytecam]

Originally Posted by Wagstaff

So, according to Wikipedia, the distance to Betelgeuse could be anything between 497LY and 789LY. That's a huge difference. So how accurate are all the other measurements to "nearby stars"? Indeed, how are the measurements taken in the first place?
Wagstaff

That sounds disappointing - you'd better do more Goggling