When we look at the night sky, are *any *stars we see dead? Are there any 1000-light year distant stars that astronomers think died 500 years ago? We’d still be seeing their light, and will do so for another 500 years.
It’s certainly true that the vast majority are still around, but are there any at all that probably no longer exist?
I mean stars that are visible as single points of light with the naked eye, or a low-powered telescope. Distant galaxies that can be seen with the Hubble telescope don’t count.
INAA but believe we don’t have “will explode in X years” down to sufficient resolution yet for that. And of course it depends on what you mean by dead. No star remnants are so inactive there’d be nothing to observe in that time frame.
Here’s a list that should have included your dead star if it existed, if I interpreted your meaning correctly:
If you allow telescopes like Hubble, then the answer is likely yes as we can see individual blue supergiant stars in nearby galaxies where the stars have shorter expected life-spans than the distance to that galaxy.
This pageshows how many stars you can see with various power telescopes.
So it depends on your definition of ‘low-powered’.
As an example an 8-inch telescope will see stars down to 13.3 magnitude, or around 20 million stars. There are 400 billion stars in the Milky Way galaxy.
The supernova rate is 1 per 50 years (although we haven’t spotted one for 400 years). So 20 supernovas in the last 1000 years.
How many of these supernovas are among the 20 million stars you can see with an 8-inch telescope. 20 x 20 million / 400 billion = 0.001
White dwarf stars are considered dead by what the OP is saying. Sirius B is the brightest in our night sky but at an apparent magnitude of 8.4, you’ll need something a little bigger than binoculars or a small toy refractor. So say a 6" homebuilt or definitely an 8" commercial unit, although we may not be able to resolve it from Sirius A, she’s pretty bright.
40 Eridani B is the next brightest and her companion stars are all small M-class stars, so it should be easily resolved at 9.5 magnitude.
A star goes nova, and the light from the event doesn’t reach us for hundreds of years. During that time we see the star as normal, even though it no longer exists in reality.
I want to know if any naked-eye visible stars where this is known, or speculated possible, for it to have happened.
Ah, you’re looking for stars that experience a cataclysmic death. Eta Carinae (Wiki Article) would be the best candidate AFAIK. A smallish telescope would resolve it in a clear stable sky, although it is a Southern Hemisphere object.
No way to tell if she’s gone off yet, we just have to wait until the light of the supernova reaches us. It was only back in 2008 that we actually caught a supernova exploding (“Supernova caught exploding on camera”), so perhaps the day will come when we can predict when these events happen. For now we have to wait.
Our own Sun will never [del]nova or[/del] supernova, she just doesn’t have enough mass. She’ll just slowly peter out all calm and collected without whimper or whining, what a good girl she is !!!
Huh. 7,500 light years away. Unusual behavior observed over the last 150 years, so hard to predict, but pretty likely to undergo a supernova (or perhaps “supernova imposter”) event rather soon (in the next century or so, I guess).
When they use the future tense in that Wiki article, really they’re talking about the past, right? More accurate to say “In the next century or so, we’ll find out what happened to the Eta Carinae system back in the fifth or sixth millennium BC, when humans were just starting the build the first villages in and around the Anatolian Peninsula, and the first slow experiments wth the domestication of a few edible grains was starting to happen in a handful of scatters locations on Earth.”
The quote from Wikipedia is “… and is expected to explode as a supernova in the astronomically near future.” I read this to mean “within a hundred million years”.
So, to sum, is it fair to say that there it’s very likely that all the stars we can see with the naked eye or a low-powered telescope – let’s say binoculars – are are really still there (although a few of them have varied in magnitude, something we’ll observe in the future)?
Here’s an interesting piece from NASA “Evidence for Supernovas Near Earth”. This is within the distance specified in the OP, although it is fair say we’ve moved into the local bubble since the explosions occurred.
Maybe, or maybe not … Eta Car. is our best candidate but there could well be other things going on there that we don’t understand. We’ll have to wait to find out. Strictly speaking, any star with mass greater than 8 solar masses will be subject to a supernova explosion, whether that happens tomorrow or in 10,000 years we just don’t know for sure. Research continues …
He excluded powerful telescopes “I mean stars that are visible as single points of light with the naked eye or a low powered telescope”. If you’re going to nitpick the wording of someones OP, at least get it right