A General Astronomy Thread

[Slim]

Went outside on a clear night during the week, and noticed Orion was very clear. It looked exactly the same as it did when I was 9, which was actually a bit of a melancholy thought. It made me think of my own impermanence.

So anyway I did a bit of googling and ChatGPT research and it turns out that all of the Orion stars are, in cosmic terms, very short lived.

Our own local star's total lifespan is roughly 10 billion years. The Sun is a bit less than half way through its expected life. By contrast the longest total lifespan from birth to death of the Orion stars is that of Bellatrix, which will have lived about 40 million years when it dies. Animals on Earth with the ability to see stars in the night sky existed before any of the Orion stars was born. Fingers crossed some will exist when it dies, as well.

Highslide Image Viewer

Rigel is the brightest Orion star. Its total birth-death lifespan is 8-10 million years and it's had most of them already. By contrast the Sun's lifespan is 1000 times longer. Rigel is about 420,000 times the size of the Sun by volume and it gives out approximately as much light energy in a second as the Sun does in a day and a half.

Of course over a few thousand years, because the stars are moving, Orion will look a bit different. But since I was 8 or 9, the difference in the shape is imperceptible.

Imagine that 56 years ago, I drew an exact, 5 metre drawing of Orion on a huge piece of paper. If I wanted to update it today, I'd need to move Betelgeuse (the most "mobile" star in the constellation in 2D terms) by about a tenth of a millimetre.

[Fishy]

Can anyone recommend a decent telescope  for home use ? I was at a dark skies place near Hexham a couple of years ago and I asked the guy but I cannot remember the make he said...

[Thenop]

We have a not so expensive table model Celestron. Hardly used, come to think of it I should really take it out more. Works fine for me and didn't break the bank.

[Nickslikk2112]

Can anyone recommend a decent telescope  for home use ? I was at a dark skies place near Hexham a couple of years ago and I asked the guy but I cannot remember the make he said...

I've got a 4.5" Bresser Optic refractor.

Barely use it these days, in Summer it doesn't get dark until too late and it's not an exciting time astronomically.

We hardly ever seem to get clear skies in Winter these days and that's the most exciting time astronomically. Of course clear Winter skies mean cold and frosty.

[Nickslikk2112]

I'd need to move Betelgeuse (the most "mobile" star in the constellation in 2D terms) by about a tenth of a millimetre.

Betelgeuse is a likely candidate to go Supernova and hence disappear to the naked eye, although the recent discovery of a companion star - Siwarha - has pushed the date of explosion back.

https://starwalk.space/en/news/betelgeuse-star-will-be-supernova#siwarha-and-betelgeuse-why-the-supernova-will-have-to-wait

[Slim]

I looked up possible Supernova candidates:

Highslide Image Viewer

So it's possible that Eta Carinae has already "gone off", but we won't know for a few thousand years. Or tomorrow! Either is unlikely, especially tomorrow.

[The Picnic Wasp]

Went outside on a clear night during the week, and noticed Orion was very clear. It looked exactly the same as it did when I was 9, which was actually a bit of a melancholy thought. It made me think of my own impermanence.

So anyway I did a bit of googling and ChatGPT research and it turns out that all of the Orion stars are, in cosmic terms, very short lived.

Our own local star's total lifespan is roughly 10 billion years. The Sun is a bit less than half way through its expected life. By contrast the longest total lifespan from birth to death of the Orion stars is that of Bellatrix, which will have lived about 40 million years when it dies. Animals on Earth with the ability to see stars in the night sky existed before any of the Orion stars was born. Fingers crossed some will exist when it dies, as well.

Highslide Image Viewer

Rigel is the brightest Orion star. Its total birth-death lifespan is 8-10 million years and it's had most of them already. By contrast the Sun's lifespan is 1000 times longer. Rigel is about 420,000 times the size of the Sun by volume and it gives out approximately as much light energy in a second as the Sun does in a day and a half.

Of course over a few thousand years, because the stars are moving, Orion will look a bit different. But since I was 8 or 9, the difference in the shape is imperceptible.

Imagine that 56 years ago, I drew an exact, 5 metre drawing of Orion on a huge piece of paper. If I wanted to update it today, I'd need to move Betelgeuse (the most "mobile" star in the constellation in 2D terms) by about a tenth of a millimetre.

I love the name Betelgeuse. I'd never heard of the size of Rigel. The size of our Sun is unimaginable to me. 420,000 times larger is mind blowing. Strange the our star is only known as the Sun and doesn't have another astronomical title.

[Thenop]

Strange the our star is only known as the Sun and doesn't have another astronomical title.

Then again we can pronounce it in about 7100 languages, so it has many names. Whereas Betelgeuse and Rigel are most likely designated as such because of their given name.

[Slim]

I love the name Betelgeuse. I'd never heard of the size of Rigel. The size of our Sun is unimaginable to me. 420,000 times larger is mind blowing. Strange the our star is only known as the Sun and doesn't have another astronomical title.

Possibly a bit of a misleading figure that because (as any fule kno) a sphere's volume scales with the cube of the diameter. So it's only about 75x larger by diameter.

I love thinking about astronomical scales. So if the Sun were a football, Rigel would be a sphere the height of a 5-storey building. The Earth would be a tiny ball bearing, 2mm high and about 23.5 metres from the football Sun. The 5-storey Rigel wouldn't even be in the same country! 1300km away.

[The Picnic Wasp]

I love the name Betelgeuse. I'd never heard of the size of Rigel. The size of our Sun is unimaginable to me. 420,000 times larger is mind blowing. Strange the our star is only known as the Sun and doesn't have another astronomical title.

Possibly a bit of a misleading figure that because (as any fule kno) a sphere's volume scales with the cube of the diameter. So it's only about 75x larger by diameter.

I love thinking about astronomical scales. So if the Sun were a football, Rigel would be a sphere the height of a 5-storey building. The Earth would be a tiny ball bearing, 2mm high and about 23.5 metres from the football Sun. The 5-storey Rigel wouldn't even be in the same country! 1300km away.

So, if the Sun was the size of an average car petrol tank (remember those?) and it takes approximately two minutes to fill, then Rigel would take 583 days. I think. Wow!

[Matt2112]

"Space," it says, "is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space".

[Slim]

Just been outside, surprisingly it's a very clear night in NW Leics at the moment. Just had the best view of Orion I think I've ever had! Belt and scabbard very visible.

Also - Jupiter is very bright tonight. As I was looking up I saw what I thought must be the ISS glide overhead - but it blinked out after a couple of seconds. Checked, wasn't the ISS. Must have been some other satellite.

[Fishy]

ISS is due overhead tomorrow 5.25 in the morning..

[David L]

ISS is due overhead tomorrow 5.25 in the morning..

I'll probably give that a miss 

[Fishy]

Six planets on show in celestial 'parade'  https://www.bbc.co.uk/news/articles/c4g3l0yzyxdo