A Glimpse into the Heart of a Quasar | Hacker News Reader

A Glimpse into the Heart of a Quasar

nature.com

60 pointsPharmakon9 comments

It's a great article. But it's odd that it didn't mention work on our local (fortunately quiet) quasar, Sagittarius A*. Although there's too much dust for visible observations, it's just so damn close. And there's been some great imaging work at gamma, x-ray and radio wavelengths. Although I don't believe that there's a substantial accretion disk, we can actually observe stuff that's orbiting the black hole.

Sag A* is not a quasar. If it were, it would be the brightest thing in the sky by several orders or magnitude.

It's a potential quasar. It's just that there's not much accretion happening right "now". And it does occasionally flare.[0] Also, I don't believe that we have the data to exclude the possibility that something big is heading inward. We only see stuff that's close enough to get hot enough.

But of course, given that we're near the galactic plane, neither jet points at us. And although, as I recall, the jets are somewhat off-axis, they're not off in our direction.

0) https://arxiv.org/abs/1709.09896

It might become a full-blown quasar when the Andromeda Galaxy collides with the Milky Way ~4.5 billion years from now. We'd better take that into consideration when we start planning for the death of our Sun ;)

Based on what we've observed, one could likely estimate the amount of accretion needed to make Sag A* visible from Earth. Or bright enough to fry us. It'd be a huge stretch for me to do that. But I bet that it's a lot less than Andromeda. I mean, there could be a substantial black hole, maybe 50-100 years out, and I doubt that we could detect it now :)

Just today I read some comment about „Science is slowing down“, but honestly, there is so much astonishing progress (like this one) purely motivated by curiosity - it’s truly motivating and inspiring!

I'm personally convinced that the "science is slowing down" perception is a consequence of actual progress speeding up while the time taken for new discoveries to percolate into the common consciousness is increasing. You look back on discoveries that have had time to percolate, and you see a rapid ramp up. Then you look at the past few years, and you see less going on because it's all still in labs and obscure research papers and the like.

Also, it's hard to know which discoveries are hugely important when they're still drowned out in dross. It's like the way '70s music is "the best music", because we've forgotten the tons and tons of crud '70s music.

There is an effect where the progress of science can stay the same, but the progress is in expanding details.

So instead of Einstein reshaping our understanding of spacetime, we gain a more detailed understanding of the consequences of that discovery. The average cosmologist these days probably has a superior understanding of relativity than even Einstein did.

Consider the map of human knowledge to be an ever expanding tree. If you have growth happening at the same rate, it can seem slower, because it's hard to grasp the full breadth of the growth now. I don't know if I'm explaining it that well.

Our understanding of the universe is extremely detailed compared to even 50 years ago, and we continue to advance rapidly. It's just that advancement is spread out much more, and is much, much more detailed and nuanced.

Awesome article!

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