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Not long ago, the center of the Milky Way exploded

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Re: Not long ago, the center of the Milky Way exploded

#101

Post by mirimir »

FrameworkFred wrote: post #35

Given that we're able to aim telescopes at things that are billions of light years away, I wonder how close we are to being able to see the reflection of such a thing when it actually happens on some celestial body 3.5 million light years away.

We already have: Clavel et al. (2013) Echoes of multiple outbursts of Sagittarius A[star] revealed by Chandra.[0] Here's the abstract:

> The relatively rapid spatial and temporal variability of the X-ray radiation from some molecular clouds near the Galactic center shows that this emission component is due to the reflection of X-rays generated by a source that was luminous in the past, most likely the central supermassive black hole, Sagittarius A[star]. Studying the evolution of the molecular cloud reflection features is therefore a key element to reconstruct Sgr A[star]'s past activity. The aim of the present work is to study this emission on small angular scales in order to characterize the source outburst on short time scales. We use Chandra high-resolution data collected from 1999 to 2011 to study the most rapid variations detected so far, those of clouds between 5' and 20' from Sgr A[star] towards positive longitudes. Our systematic spectral-imaging analysis of the reflection emission, notably of the Fe Kalpha line at 6.4 keV and its associated 4-8 keV continuum, allows us to characterize the variations down to 15" angular scale and 1-year time scale. We reveal for the first time abrupt variations of few years only and in particular a short peaked emission, with a factor of 10 increase followed by a comparable decrease, that propagates along the dense filaments of the Bridge cloud. This 2-year peaked feature contrasts with the slower 10-year linear variations we reveal in all the other molecular structures of the region. Based on column density constraints, we argue that these two different behaviors are unlikely to be due to the same illuminating event. The variations are likely due to a highly variable active phase of Sgr A[star] sometime within the past few hundred years, characterized by at least two luminous outbursts of a few-year time scale and during which the Sgr A[star] luminosity went up to at least 10^39 erg/s.

0) https://arxiv.org/abs/1307.3954

Edit: Older image: https://www.chandra.harvard.edu/photo/2007/gcle/

Re: Not long ago, the center of the Milky Way exploded

#102

Post by blacksmith_tb »

jjoske wrote: post #99
frogpelt wrote: post #67

Earlier quoted context omitted.

And yet few have ever heard this Larry while Millard Fillmore maintains the distinction of being the president with the coolest name. If only Spiro T. Agnew would have made it.

I've never heard of Millard Fillmore before.

Likely more people (inside the US and outside too) are more familiar with Fillmore St. in San Francisco[1], which is named for President Fillmore, and its famous theater / music venue of the same name.

1: https://en.wikipedia.org/wiki/Fillmore_District,_San_Francis...

Re: Not long ago, the center of the Milky Way exploded

#103

Post by teslaberry »

Having been an expert layperson reader of astronomy reserach for 2 decades....i would venture to speculate that the long lost connection between eliptical galaxies and spiral galaxies is not only an initial set of imabalnces in the inertia of the gas cloud but the distinct lack of a single galactic central black hole to clear the galaxy polar direction with massive polar vortex blast streams persistently over time.

Re: Not long ago, the center of the Milky Way exploded

#104

Post by fmihaila »

klank wrote: post #98
jerf wrote: post #87

Earlier quoted context omitted.

You need natural mirrors, because as others have pointed out, they have to already be there, you can't get ahead of the light to put them there. It has been suggested that black holes could provide this mirror, but it requires resolving not just something the size of Earth, but something much smaller , at a distance of 30 million light years +. Unfortunately you actually start hitting up against the limits of spaceti…

What are these "limits of spacetime's resolution" you speak of? Beyond speculation, I'm not aware of anything showing spacetime to be discrete.

> What are these "limits of spacetime's resolution" you speak of?

> Beyond speculation, I'm not aware of anything showing spacetime to be discrete.

It is a prediction of loop quantum gravity [1]:

In 1988, Carlo Rovelli, Lee Smolin, and Abhay Ashtekar introduced a theory of quantum gravity called loop quantum gravity. In 1995, Rovelli and Smolin obtained a basis of states of quantum gravity, labelled by Penrose's spin networks, and using this basis they were able to show that the theory predicts that area and volume are quantized. This result indicates the existence of a discrete structure of space at very small scale.

[1] https://en.wikipedia.org/wiki/Carlo_Rovelli#Loop_quantum_gra...

Re: Not long ago, the center of the Milky Way exploded

#105

Post by monomyth »

eloff wrote: post #66
ekianjo wrote: post #42

Earlier quoted context omitted.

A Mars base would do a lot to prevent extinction of human life because of an "unlikely" but "it's just a matter of when, not if" situation where we get hit by a massive rock.

Actually there's only a period in time where we're vulnerable to such things. Eventually we'll know of all the potential threats with enough advanced warning and have the capabilities to deflect them. Maybe we're vulnerable for another hundred years, but not likely still vulnerable in a thousand. Given the rarity of such events, we should be fine.

> Eventually we'll know of all the potential threats with enough advanced warning

We have no idea what Type II or III adversarial civilization will be able to do to us, and how fast.

Re: Not long ago, the center of the Milky Way exploded

#106

Post by ianai »

mannykannot wrote: post #15

When this was first noticed (2013) I recall statements (possibly speculative) that the irradiated part of the Magellanic Stream might have glowed brightly enough to be visible in the night sky. If so, it would have subtended about half a degree, about the same width as the moon and the sun.

And here we are stuck with just a sun and moon!

Re: Not long ago, the center of the Milky Way exploded

#107

Post by dwoozle »

Negitivefrags wrote: post #88
frogpelt wrote: post #67

Earlier quoted context omitted.

And yet few have ever heard this Larry while Millard Fillmore maintains the distinction of being the president with the coolest name. If only Spiro T. Agnew would have made it.

I have heard of Larry Niven and never heard of Millard Fillmore. Being outside the US I never covered past US presidents in school.

Probably fewer than 10% of Harvard graduates could tell you anything substantive about Millard Fillmore’s presidency. He isn’t covered here either.

Re: Not long ago, the center of the Milky Way exploded

#108

Post by glandium »

lifeisstillgood wrote: post #18
hanoz wrote: post #13

Earlier quoted context omitted.

It's very nearly 3.5 days in terms of a middle aged person's lifetime, which is an interesting rule of thumb I think I've just discovered.

so ... wild guess 37 years * 365 days = 13,500 days universe has existed for 13.5 billion years So each day in a middle aged life is 1 million of the universe's years. I like it ! :-) * This flare: Last Friday * Dinosaur extinction: 3rd of August * Pangea breaks apart: about Valentines day * Earth formed: June 2007 * Universe Born: 1982 Of course this means the Universe would have listened to Flock Of Seagulls as a k…

* The Great Pyramids: 6 minutes and 37 seconds ago.

* 1982: 3.2 seconds ago.

Re: Not long ago, the center of the Milky Way exploded

#109

Post by jerf »

fmihaila wrote: post #104
klank wrote: post #98

Earlier quoted context omitted.

What are these "limits of spacetime's resolution" you speak of? Beyond speculation, I'm not aware of anything showing spacetime to be discrete.

> What are these "limits of spacetime's resolution" you speak of? > Beyond speculation, I'm not aware of anything showing spacetime to be discrete. It is a prediction of loop quantum gravity [1]: In 1988, Carlo Rovelli, Lee Smolin, and Abhay Ashtekar introduced a theory of quantum gravity called loop quantum gravity. In 1995, Rovelli and Smolin obtained a basis of states of quantum gravity, labelled by Penrose's spin…

It's a prediction of other things, too. Even just sheer every-day quantum mechanics sets a limit, too; eventually you're asking to nail down a photon's origin with so much precision that you lose the frequency or something, things you don't normally think about even in the most extreme astronomy today, but become relevant when discussing bouncing photons around a black hole 30 million light years away.

Re: Not long ago, the center of the Milky Way exploded

#110

Post by sliken »

jwr wrote: post #28

For those of us who read Larry Niven's sci-fi novels, this headline is… both amusing and somewhat scary.

There another short story by Niven where someone gazing at the moon sees it get as bright as the sun. They quickly come to the conclusion that some horrific event will end life on earth as soon as the earth rotates towards whatever made the moon so bright.

It's a fun little romp.

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