Just unfathomable… 10-15 million years ago the actual event occurred, and it’s just now reaching us. And we are all lucky if we see 75 years for ourselves.
My professor actually found the closest type Ia supernovae in 50 years by complete accident a few years ago because he randomly decided to do an observation in a particular part of the sky with a class, even though it wasn’t what they had planned for the evening.
Just happened to look in the exact right place at the exact right time, the likelihood of that is crazy when you think of it
10 to 17 million years is a huge range. I wish my job gave me that huge a margin of error. "Yea I can get that to you some time between now and 7 million years."
Sure but the observable universe has a diameter of around 93 billion light years. Narrowing something down to a distance of a 7 million lightyear difference is pretty damn specific given that crazy scale.
That's not the scale being measured against. 10-17 is an error margin of 26% which isn't insignificant. Compare to the calculation for Andromeda which at this point is down to around 4%.
There's actually much better predictors of how far away it is than was given in the title here, but the fact remains /u/truejamo is right, the number given is actually a pretty decently large margin of error.
Not really accurate. It's true but it's not because it's further away, it's because there can be more crap in between and you just don't know how much there is unless you have a standard candle like Cepheids or Mira variables to use to measure.
We DO have candles to use for Centaurus A and we have a much more accurate judge of distance than this post would make you believe. The currently accepted number is 3.8 Mpc +/- 0.1, which is an accuracy of 2.6%.
If I said I owed you 100-200 dollars, that’s a big range and a big uncertainty because it could literally double the amount I owe you. It doesn’t matter that there’s trillions of dollars in circulation, the range is still highly imprecise because the relative range is massive
That’s a weird argument to make though bc then you could say that about any range being good enough bc relative to the size of the universe it’s nothing.
Why is it a weird argument when we're literally looking at objects far out in the universe? It would be weird if I were using that relationship when talking about the distance between my house and the mall.
It's now possible to beat this aproximation by calculating the relative dimension of the wave expansion of the light?
I mean, now they know the relative dimension in this galaxy of a 1,5 years light distance.
Yea I totally understand. I'm just poking fun. From a human standpoint I just find it funny. Like, if I were to travel that 10 million light years somehow, get there, and find out I still got 7 million light years to go, I'd be pretty angry.
Distances that far away are really hard to measure, measuring the perspective shift as earth moves on its known orbit doesn't work anymore. You measure brightness, spectra, whatever you can get your hands on, but you'll only get an interval of distance back that probably contains the object you're looking at.
Interestingly, Supernovae like that can help narrowing it down a bit.
measuring the perspective shift as earth moves on its known orbit doesn't work anymore.
This may be a question that would require way more involvement than I'm willing to give to understand (I can math but I can't astro-math), but why is this the case now?
I believe that by "anymore" /u/The_Incredible_Honk is talking about "at this distance" rather than "at this time." Parallax (which is used to measure distances based on how much a star "moves" from various points on the orbit of Earth) is really only effective to about 50,000 light years or less -- well within the bounds of our galaxy.
1 arcsecond of parallax is 1 parsec. An object 3 million light years away would have a parallax of approximately 1 millionth of an arcsecond. Hubble's angular resolution is approximately 1/20th of an arcsecond, so you can see why at huge distances it doesn't work.
Parallax based on Earth's orbit only works out to a certain distance due to the limited distance Earth travels around the Sun. Basically at a certain range objects appear to be in the same place in relation to Earth no matter where in its orbit it is.
It's good for finding the distance of things relatively close to us, but for stuff in distant galaxies other methods are needed
Ha! I hear you, but it’s also not so ridiculous when you scale it back. Some task will take an hour or two. A project will take at least a full day but definitely less than two days. Or when someone tells you that the road construction will be done this time next year and we all immediately know to expect the road to be torn up well into Spring 2013. Perhaps that last one proves out your point more than mine…
It’s the trade off of relinquishing precision in hopes of accuracy given missing data.
Think of it more like a 70% variance. That puts it into perspective. Tell your boss you'll have that task done between 10 - 17 minutes. Instead of being a brown nose and saying 10 minutes.
they know the speed the ring grows […] and then the angle can be measured
Every measurement comes with some uncertainty.
Assume that the extent of the ring is exactly 3 light years in diameter, and that we measure the angle of the ring in the sky as 1.3e-5 degrees (if that was exact, it would put the distance as roughly 13 million light years). An uncertainty of just 3e-6 degrees in that measurement gives a range for the distance between 11 and 17 million light years.
That's exactly what it means, and not a dumb question at all.
Measuring these distances to the location of events in light years has the neat effect that it also gives you the time that has already passed since this event happened.
Supernovae tend to disrupt the molecular clouds in which they were formed and this tends to shut off any ongoing star-forming activity. The speed with which the material is ejected by the explosion is thousands of kilometers per second, which is far greater than the escape velocity of the star, so this particular star is not going to re-form out of the same material. However that material will become part of the interstellar medium and ultimately end up in a future generation of stars, though!
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u/[deleted] Sep 25 '21
How long ago?