100D Limit and Mass of Object

[CordwainerFish]

Even if that works out to be as rare as once in a century (and I'm thinking there's a pretty good chance of once in a decade or less...)

We know that supernovæ are not a once per decade event in our galaxy.

 

[rinku]

Unless they are adapted to it...

The odds are very small, but not zero...

 

[rinku]

We know that supernovæ are not a once per decade event in our galaxy.

Fair. Although there may be a healthy dose of sample bias there, since we can't SEE the light of any core stars and observations have to be done via X-Rays, which limits to how far back we have astronomical data for core supernovas. There's no equivalent to ancient Chinese supernova observations for the galactic core.

Rocket and balloon borne observations were limited in both duration and scope. 1970 was the first x-ray observation satellite, but things didn't really kick into high gear until Chandra was launched in 1999.

And... there's the Fermi bubbles and the GCE confirming that whatever is going on in there, it's certainly generating a heck of a lot of hard radiation.

 

[CordwainerFish]

Although there may be a healthy dose of sample bias there, since we can't SEE the light of any core stars and observations have to be done via X-Rays

X-rays, infrared, radio, neutrinos...

 

[rinku]

Huh. I thought IR was blocked, but no, just UV, visible and soft X-Rays. There you go. I was probably conflating the problems that occur making IR observations in many wavelengths from inside the atmosphere, but satellites (and high altitude observatories) also get around that.

Neutrino observatories have a pretty young history too. But yes, those are in the mix. As are gravity wave ones, although they're the youngest of the observatories and so have the least historical data to draw from. They are quite good at picking up massive objects in a death spiral, though.

The point remains that there is an observational history bias for all of these, even radio astronomy. There are likely to have been many unobserved supernovae whose visible light emissions predate the 1950's; the estimates for frequency within the galactic core would have a healthy margin of error. But look to fall somewhere between per decade and per century, which would make little difference for the neighbourhood.

 

[CordwainerFish]

Incidentally, they taught us way back when in ASTR 2xxx (hell if I remember the full course number) that most galaxies have a supernova about once a century. Some - the so-called starburst galaxies - have ten times that rate, but if ours were one of those we'd know it by now.

 

[rinku]

Sort of. The trouble is that the observation window is brief, and it's easy to miss them unless we stare at the same distant galaxy for decades on end. We can tell from supernova remnants in our own galaxy that there SHOULD be a rate of about one every 61 years, but the last directly observed one was 1604. The problem as usual being distance and absorption and blockage of the signal by intervening objects, dust and gas.

 

[CordwainerFish]

The trouble is that the observation window is brief, and it's easy to miss them unless we stare at the same distant galaxy for decades on end.

When I was astronomizing, once every year or two there'd be a news flash of a supernova in Messier This or NGC That (and if they were in the night sky where I lived and I could be bothered, I'd pack up my scope, drive to my dark sky site, and look at it). Nearby galaxies have a lot of eyes on them...

The problem as usual being distance and absorption and blockage of the signal by intervening objects, dust and gas.

And the recentness of sensing modalities other than Eyeball, either MkI or with optical assistance.