Slashdot Mirror
About That Monstrous Black Hole We're All Orbiting (theatlantic.com)
Astronomers on Wednesday reported new telescope observations of the environment around the Milky Way's supermassive black hole, named Sagittarius A*, pronounced "a-star," and they transformed the data into a lively animation. From a report: The video is positively ghostly. Clumps of gas swirl around the black hole, traveling at about 30 percent of the speed of light. Astronomers collected the data for the visualization using an instrument on the European Southern Observatory's Very Large Telescope, located in the deserts of northern Chile. The instrument, appropriately named GRAVITY, detected flares of infrared radiation coming from the disk surrounding Sagittarius A*. The researchers believe the bursts originated very close to the black hole, in an incredibly tumultuous region known as the innermost stable orbit. Here, cosmic material is slung around violently, but it remains far away enough that it can circle the black hole safely without getting sucked into the darkness.
If the thought of orbiting a monstrous, star-gobbling black hole spooks you, don't worry. Earth, located about two-thirds out from the center of the Milky Way, is at a very safe distance. The planet is in no danger of being consumed and wiped off the face of the universe. But, like everything else in the galaxy, it has long been subject to the black hole's whims. When black holes belch radiation out into space, the outflow can heat surrounding gas so much that it prevents it from cooling. If cosmic dust can't cool, it can't condense to form individual, brand-new stars, including ones like our sun. Scientists suspect that the fates of galaxies -- whether they produce new stars or stop altogether -- rests with the supermassive black holes at their centers.
If the thought of orbiting a monstrous, star-gobbling black hole spooks you, don't worry. Earth, located about two-thirds out from the center of the Milky Way, is at a very safe distance. The planet is in no danger of being consumed and wiped off the face of the universe. But, like everything else in the galaxy, it has long been subject to the black hole's whims. When black holes belch radiation out into space, the outflow can heat surrounding gas so much that it prevents it from cooling. If cosmic dust can't cool, it can't condense to form individual, brand-new stars, including ones like our sun. Scientists suspect that the fates of galaxies -- whether they produce new stars or stop altogether -- rests with the supermassive black holes at their centers.
If you need instructions on how to pronounce something you've named, you're doing it wrong. That's about as offensive as pronouncing GIF with a j.
What an amazing coincidence! I bet that doesn't happen often!
It's not governed by one force, but at least four: Strong, Weak, Electromagnetic and Gravity. Possibly five, if we ever figure out what dark energy is.
um: "... and they transformed the data into a lively animation. "
Read much?
The sun will expand into a red giant, burning away the inner planets and Jupiter will become the new Mercury in 4B years. From 4B to 8B years, the Milky Way Galaxy and the Andromeda Galaxy will merge together. All the fun astronomical stuff will take place after we die.
If you're referring to radiation coming from the accretion disk around the black hole, then it's not within the event horizon, so it can escape. If you're referring to Hawking radiation, then good luck understanding that.
All the fun astronomical stuff will take place after we die.
I hope so! The alternative is it happens when we die.
But are Pak Protectors on the way here?
Even before the sun's red giant phase it will have doubled in luminosity. Assuming no feedback effects, that would increase Earth's equilibrium temperature by 19% on an absolute temperature scale. So if you assume that feedback mechanisms remain the same, you're talking at least 50 degrees celsius temperature increase.
Of course, that's far too simplistic of an approach to take; feedback levels will change, and the details of that are a complex modeling task. Runaway greenhouse effects are quite possible (such as: loss of crustal water = reduce crustal viscosity = reduced / eliminated large-scale plate tectonics = Venus-like geology).
Of course, the biggest question is whether any sort of sentient life would exist in the system at that point in time. If so, it would likely be so far advanced (billions of years of technological development) that building an orbital solar reflector would be a laughably trivial task, and even relocating the planet might be within their reach. The ultimate achievement would be if they were to develop technology to siphon off matter from the sun over billions of years, ultimately reducing its mass to under 0,3Msol. Then it would not only burn slower, but also be fully convective - greatly extending its lifespan. Very low mass main sequence stars can potentially burn for trillions of years.
Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
Some have argued with me that an expanding sun would just push the planetary orbits outward. I haven't seen a definitive answer either way.
Its like a big drain the closer you get to the drain, the faster you go. And black hole drains is what causes time to exist.
Through what mechanism? Reverse gravity?
The only way I can think of for an expanding sun to push the planetary orbits out would be a shock wave, which isn't so much going to push out your orbit, as simply scatter things in random directions that may or may not end up in stable orbits -- in fact, they may or may not still be in one piece.
The orbits aren't simply going to get bigger with the sun, because any force acting to push the planet outwards would be catastrophic.
What kind of 'definitive answer' to an incredibly stupid idea not founded in physics would you require?
Wouldn't it more accurately be described as an A-hole?
True. Still, Betelgeuse might explode in our lifetimes, so there's that to look forward to.
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
Pretty sure that's wrong.
Orbits only depend on mass, not density. So assuming the actual mass of the Sun doesn't change when it goes supernova then our orbit won't change.
Likewise, if the Sun were replaced tomorrow with a black hole with the same mass, it would be the size of a small town but none of the planets' orbits would change. Although we would freeze to death.
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
Surprisingly enough, it doesn't really matter what you siphon off. In a star the mass of our sun, there's relatively little inflow of new fuel into the core. Smaller stars are fully convective, in that everything can cycle through the core. So just by simply "lightening" the star by any means, down to a red dwarf (note: not a brown dwarf!), you let all of that new fuel get in. Also, the higher mass of the sun increases the reaction rate in the core, so reducing the mass slows that down significantly. And red dwarfs are strictly hydrogen-burning; there's never a helium flash, no triple alpha process.
Red dwarfs never turn into giants. Instead, they're predicted to evolve into blue dwarfs. Although since it takes orders of magnitude longer than the age of the universe for this to happen, there are no blue dwarfs in the universe yet to observe!
Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
the size of a small town
Black holes continue to be described as singularities with zero volume.
Perhaps you mean that the volume enclosed by the event horizon is the size of a small town?
That that is is that that that that is not is not.
Not to nitpick...
Okay, to nitpick - "revolve", not "rotate"....
"I do not agree with what you say, but I will defend to the death your right to say it"
Lay off the weed. Realistic theories:
1. We gauge time by memorable events.
As William James hypothesized, we may be measuring past intervals of time by the number of events that can be recalled in that period. Imagine a 40-something mom experiencing the repetitive, stressful daily grind work and family life. The abundant memories of her high school years (homecoming football games, prom, first car, first kiss, graduation) may, compared to now, seem like much longer than the mere four years that they were.
2. The amount of time passed relative to one's age varies.
For a 5-year-old, one year is 20% of their entire life. For a 50-year-old, however, one year is only 2% of their life. This "ratio theory," proposed by Janet in 1877, suggests that we are constantly comparing time intervals with the total amount of time we've already lived.
3. Our biological clock slows as we age.
With aging may come the slowing of some sort of internal pacemaker. Relative to the unstoppable clocks and calendars, external time suddenly appears to pass more quickly.
4. As we age, we pay less attention to time.
When you're a kid on December 1, you're faithfully counting down the days until Santa brings your favorite Hot Wheels down the chimney. When you're an adult on December 1, you're a little more focused on work, bills, family life, scheduling, deadlines, travel plans, Christmas shopping, and all of that other boring adult stuff. The more attention one focuses on tasks such as these, the less one will notice the passage of time.
5. Stress, stress, and more stress.
As concluded by Wittmann and Lehnhoff (and replicated by Friedman and Janssen), the feeling that there is not enough time to get things done may be reinterpreted as the feeling that time is passing too quickly. Even older individuals (who are, more often than not, retired from work) may continue to feel similarly due to physical handicaps or diminished cognitive ability.