Thursday, March 15, 2012
In related news...
I referenced a song in that last post- I know, but I couldn't resist. Just thought I'd link it here; it's amusing.
Wednesday, March 14, 2012
The Sun (Is a Miasma of Incandescent Plasma)
Welcome back, hypothetical reader! Had enough of black holes? Yes? Good. No? Too bad, we're talking about the sun now. Why the sun? Because the sun is interesting. We've discussed stars, their fusion processes, and soon we'll be discussing their deaths. But why not discuss stars on a different level, looking at their physical structure, and their layers. That's what we'll be doing today.
First, the basics. The sun has a mass of 1.9891*10^30 kilograms, 333000 times that of the Earth (5.9736*10^24 kg) and a radius of 6.955*10^5 kilometers, 109 times that of the Earth (6731 km). That's pretty huge, but relative to other stars, it is only average. As we discussed in class today, the stars that go supernova can be ten or even one hundred times larger than the sun, while white dwarfs can have the sun's mass but be no larger than the earth.
Of course, today, we're not discussing types of stars, we're talking about that one, very important star in the middle of our solar system. More specifically, I'll now be talking about the parts of the sun. You see, the sun is split up into several layers- the core, the radiation zone, the convection zone, the photosphere, the chromosphere, the transition region, and the corona.
First, the core. The core is the extremely dense region at the center of the star, where nuclear fusion occurs, powering the sun. The core, which is fifteen thousand degrees kelvin on average, is so intensely hot that the hydrogen and helium atoms in it are completely stripped of their electrons. The result is a state of matter referred to as plasma, which is the most energetic state of matter, and is separate from the other three states of matter. Hence, "The Sun is a Miasma of Incandescent Plasma," as opposed to being a "Mass of incandescent gas," as was previously believed.
The layer above the core, who's thickness takes up most of the sun's radius, is the radiation zone. This zone contains much of the star's unfused hydrogen, and it's only real purpose is, as it's name suggests, to radiate the sun's energy. As we've discussed, it takes huge amounts of time for light released by the sun's core to radiate outward, and much of that process takes place in this layer. In this stage, photons are rapidly released, absorbed by hydrogen atoms, and released again. Eventually, these photons work their way to the surface.
Next is the convection zone. We've discussed previously that in medium and larger stars, hot hydrogen "bubbles" can rise from the lower layers to the surface of the sun, acting as an alternate way for the sun to radiate energy.
"Photosphere" is really just a fancy thing to call the surface of the sun. Once light reaches the photosphere, it is able to radiate away, without being interrupted by being absorbed and redirected again. The temperature at this layer is around six thousand kelvin.
Above the surface of the sun is a thin layer called the chromosphere. This area contains scattered gasses, which cause the absorbtion lines visible in sunlight.
The outermost layer of the sun is the corona, literally "halo" in Latin. This layer is by far the hottest layer of the sun, with temperatures ranging in the millions of kelvin. The gasses in this layer are carried by solar wind throughout the solar system, barraging planets in radiation- the result of which on our planet is the auroras.
Here is an image that may clear up the orientation and relative sizes of the layers.
Hopefully this gives some interesting detail and a good look into the interior of the sun. I felt that this would be of interest, as we discussed how stars work, form, and die, but spent relatively little time looking closely at the stars themselves.
Until next time, happy astronomy!
Sources-
http://www.spacestationinfo.com/layers-sun.htm
http://www.universetoday.com/wp-content/uploads/2008/09/solarinterior.jpg
http://en.wikipedia.org/wiki/The_sun
First, the basics. The sun has a mass of 1.9891*10^30 kilograms, 333000 times that of the Earth (5.9736*10^24 kg) and a radius of 6.955*10^5 kilometers, 109 times that of the Earth (6731 km). That's pretty huge, but relative to other stars, it is only average. As we discussed in class today, the stars that go supernova can be ten or even one hundred times larger than the sun, while white dwarfs can have the sun's mass but be no larger than the earth.
Of course, today, we're not discussing types of stars, we're talking about that one, very important star in the middle of our solar system. More specifically, I'll now be talking about the parts of the sun. You see, the sun is split up into several layers- the core, the radiation zone, the convection zone, the photosphere, the chromosphere, the transition region, and the corona.
First, the core. The core is the extremely dense region at the center of the star, where nuclear fusion occurs, powering the sun. The core, which is fifteen thousand degrees kelvin on average, is so intensely hot that the hydrogen and helium atoms in it are completely stripped of their electrons. The result is a state of matter referred to as plasma, which is the most energetic state of matter, and is separate from the other three states of matter. Hence, "The Sun is a Miasma of Incandescent Plasma," as opposed to being a "Mass of incandescent gas," as was previously believed.
The layer above the core, who's thickness takes up most of the sun's radius, is the radiation zone. This zone contains much of the star's unfused hydrogen, and it's only real purpose is, as it's name suggests, to radiate the sun's energy. As we've discussed, it takes huge amounts of time for light released by the sun's core to radiate outward, and much of that process takes place in this layer. In this stage, photons are rapidly released, absorbed by hydrogen atoms, and released again. Eventually, these photons work their way to the surface.
Next is the convection zone. We've discussed previously that in medium and larger stars, hot hydrogen "bubbles" can rise from the lower layers to the surface of the sun, acting as an alternate way for the sun to radiate energy.
"Photosphere" is really just a fancy thing to call the surface of the sun. Once light reaches the photosphere, it is able to radiate away, without being interrupted by being absorbed and redirected again. The temperature at this layer is around six thousand kelvin.
Above the surface of the sun is a thin layer called the chromosphere. This area contains scattered gasses, which cause the absorbtion lines visible in sunlight.
The outermost layer of the sun is the corona, literally "halo" in Latin. This layer is by far the hottest layer of the sun, with temperatures ranging in the millions of kelvin. The gasses in this layer are carried by solar wind throughout the solar system, barraging planets in radiation- the result of which on our planet is the auroras.
Here is an image that may clear up the orientation and relative sizes of the layers.
Hopefully this gives some interesting detail and a good look into the interior of the sun. I felt that this would be of interest, as we discussed how stars work, form, and die, but spent relatively little time looking closely at the stars themselves.
Until next time, happy astronomy!
Sources-
http://www.spacestationinfo.com/layers-sun.htm
http://www.universetoday.com/wp-content/uploads/2008/09/solarinterior.jpg
http://en.wikipedia.org/wiki/The_sun
Monday, March 12, 2012
Black Holes- Sucking Us Back In
Next day, two weeks later, same thing. Got pretty sick there for a while, so it'll take some doing to get caught up, but what can you do.
As I said last time, I'll be continuing on the topic of black holes- Namely, how we detect them. So, how do you detect something that is quite literally invisible? Ordniarily, we see things that reflect or refract light, but black holes, as we discussed, pull light in and don't let it back out. So how do we find them?
There are actually more ways to detect a black hole than you would think. One way was what I discussed previously- quasars. As I mentioned previously, quasars are superheated disks for gas and particulate quickly circling a black hole. Their extreme heat causes them to radiate significantly, so these are actually relatively easy to locate by testing the spectrum given by a radiator, looking for large amounts of x-ray and radio waves. The process in which the quasars is referred to as "accretion," and releases huge amounts of energy relative to the amounts of matter involved- as much as fourty percent of the mass' equivalent in energy is released. Along with quasars are frequently another phenomenon, referred to as "jets." These jets are massive releases of x-rays, which are released in pulses at a right angle to the plane of the quasar. Not much is known about the process by which jets are created, but they are easily observed, and are a good way to find large black holes.
Bear with the video, the quasar and jets show up about halfway through.
Well, finding black holes because they have visible formations around them is well and good, but there are plenty of black holes that don't have quasars. How do we spot those? Well, one solution is to look for gravitational lensing. You remember that, right? Of course you do. It stands to reason, since high-mass objects such as large stars and galaxies can gravitationally lens light around them, black holes, being so massive, can do the same. By searching for instances of gravitational lensing that don't appear to have an object to lens around, you can find black holes.
A third method, and the last I'll discuss, is probably the simplest. This method consists of simply observing stars in an area where it is believed a black hole may exist, and watching the movement of these stars. Their motion can often act as a clue to an invisible large mass, which it is probably orbiting. This is an especially useful method for detecting smaller black holes, those without quasars and jets, and those black holes that are scattered throughout the galaxy instead of occupying its center. This case can also apply in the rare cases where black holes form binaries with stars.
Hopefully this expands your knowledge of black holes, as this is my second post on the topic. Until my next post, happy astronomy!
As I said last time, I'll be continuing on the topic of black holes- Namely, how we detect them. So, how do you detect something that is quite literally invisible? Ordniarily, we see things that reflect or refract light, but black holes, as we discussed, pull light in and don't let it back out. So how do we find them?
There are actually more ways to detect a black hole than you would think. One way was what I discussed previously- quasars. As I mentioned previously, quasars are superheated disks for gas and particulate quickly circling a black hole. Their extreme heat causes them to radiate significantly, so these are actually relatively easy to locate by testing the spectrum given by a radiator, looking for large amounts of x-ray and radio waves. The process in which the quasars is referred to as "accretion," and releases huge amounts of energy relative to the amounts of matter involved- as much as fourty percent of the mass' equivalent in energy is released. Along with quasars are frequently another phenomenon, referred to as "jets." These jets are massive releases of x-rays, which are released in pulses at a right angle to the plane of the quasar. Not much is known about the process by which jets are created, but they are easily observed, and are a good way to find large black holes.
Well, finding black holes because they have visible formations around them is well and good, but there are plenty of black holes that don't have quasars. How do we spot those? Well, one solution is to look for gravitational lensing. You remember that, right? Of course you do. It stands to reason, since high-mass objects such as large stars and galaxies can gravitationally lens light around them, black holes, being so massive, can do the same. By searching for instances of gravitational lensing that don't appear to have an object to lens around, you can find black holes.
A third method, and the last I'll discuss, is probably the simplest. This method consists of simply observing stars in an area where it is believed a black hole may exist, and watching the movement of these stars. Their motion can often act as a clue to an invisible large mass, which it is probably orbiting. This is an especially useful method for detecting smaller black holes, those without quasars and jets, and those black holes that are scattered throughout the galaxy instead of occupying its center. This case can also apply in the rare cases where black holes form binaries with stars.
Hopefully this expands your knowledge of black holes, as this is my second post on the topic. Until my next post, happy astronomy!
Sunday, February 26, 2012
Black Holes- Really Kind of Suckish
Another bad pun.
Welcome back, hypothetical reader. Its been a while.
Well, last time you were here, I discussed quasars, their properties, and how they interact with objects around them. In addition, I briefly mentioned black holes, namely that quasars form around them in young galaxies. I also said that I'd go further into depth about the qualities of black holes. Were you looking forward to this? Of course you were!
"What is a black hole?"
A black hole could be called either a region or an object, depending on how you look at it- yes, technically it is a super-massive object, but we are ultimately more interested in the region around this object than the object itself. If you're reading this blog, it's pretty safe to assume you're in my astronomy class, but I'll start at the beginning anyway.
Isn't gravity great? It makes so many things possible- baseball, pouring drinks, not hurtling off into space, being able to exist in general- little things. We take it for granted, but when it gets strong enough, weird things start to happen. Our Earth is pretty massive, at 5.9736*10^24 kg. The escape velocity for earth is 11.2 km/s. Black holes, on the other, are so absurdly massive that their escape velocity exceeds the speed of light, making it impossible for anything to escape their gravity an object comes close enough.
You could also look at this another way. Instead of looking at the gravity of this object, you can instead look at the distortion of space-time, which is, in essence, what gravity is anyway. Either way you look at it, there comes a point where something comes so close the the center of the black hole, or "singularity," that it can't possibly get further away again. This can be viewed as a ring (or sphere, if you prefer to think in three dimensions) with the singularity at the center. This ring is referred to as the "event horizon" or "Schwarzschild radius," and is defined as the distance from the singularity where the escape velocity is equal to the speed of light.Once this radius is crossed, the escape velocity is greater than the speed of light and is, as far as we know, inescapable. Here's why:
Take the equation
1/2mv^2=GmM/r^2
Where m is the mass of an escaping object, and v is the velocity required to escape. When you solve for v, you get
v=(2GM/r)^1/2
From this, you can see that if an object is massive enough, and you are close enough to it, it is entirely possible for v, the escape velocity, to exceed the speed of light.
That's all for today, I will continue talking about black holes in tomorrow's post, including a look at the process for discovering black holes, and probably an example of a black hole in our or a neighboring galaxy.
Until next time, happy astronomy.
Sources-
Wikipedia articles for Black holes, the earth, and escape velocities
The black holes faq on the Berkley.edu site by Ted Bunn- http://cosmology.berkeley.edu/Education/BHfaq.html#q1
Welcome back, hypothetical reader. Its been a while.
Well, last time you were here, I discussed quasars, their properties, and how they interact with objects around them. In addition, I briefly mentioned black holes, namely that quasars form around them in young galaxies. I also said that I'd go further into depth about the qualities of black holes. Were you looking forward to this? Of course you were!
"What is a black hole?"
A black hole could be called either a region or an object, depending on how you look at it- yes, technically it is a super-massive object, but we are ultimately more interested in the region around this object than the object itself. If you're reading this blog, it's pretty safe to assume you're in my astronomy class, but I'll start at the beginning anyway.
Isn't gravity great? It makes so many things possible- baseball, pouring drinks, not hurtling off into space, being able to exist in general- little things. We take it for granted, but when it gets strong enough, weird things start to happen. Our Earth is pretty massive, at 5.9736*10^24 kg. The escape velocity for earth is 11.2 km/s. Black holes, on the other, are so absurdly massive that their escape velocity exceeds the speed of light, making it impossible for anything to escape their gravity an object comes close enough.
You could also look at this another way. Instead of looking at the gravity of this object, you can instead look at the distortion of space-time, which is, in essence, what gravity is anyway. Either way you look at it, there comes a point where something comes so close the the center of the black hole, or "singularity," that it can't possibly get further away again. This can be viewed as a ring (or sphere, if you prefer to think in three dimensions) with the singularity at the center. This ring is referred to as the "event horizon" or "Schwarzschild radius," and is defined as the distance from the singularity where the escape velocity is equal to the speed of light.Once this radius is crossed, the escape velocity is greater than the speed of light and is, as far as we know, inescapable. Here's why:
Take the equation
1/2mv^2=GmM/r^2
Where m is the mass of an escaping object, and v is the velocity required to escape. When you solve for v, you get
v=(2GM/r)^1/2
From this, you can see that if an object is massive enough, and you are close enough to it, it is entirely possible for v, the escape velocity, to exceed the speed of light.
That's all for today, I will continue talking about black holes in tomorrow's post, including a look at the process for discovering black holes, and probably an example of a black hole in our or a neighboring galaxy.
Until next time, happy astronomy.
Sources-
Wikipedia articles for Black holes, the earth, and escape velocities
The black holes faq on the Berkley.edu site by Ted Bunn- http://cosmology.berkeley.edu/Education/BHfaq.html#q1
Wednesday, February 1, 2012
Quasar Sources
Sorry, I forgot to post my sources in my quasar research post.
I got most of my information from either the quasars article on Wikipedia, or a quasar faq on the Virginia Tech website, which was compiled by a Dr. John Simonetti. The included image is credited to the European Southern Observatory for the image, thought the artist for the image was unlisted.
I got most of my information from either the quasars article on Wikipedia, or a quasar faq on the Virginia Tech website, which was compiled by a Dr. John Simonetti. The included image is credited to the European Southern Observatory for the image, thought the artist for the image was unlisted.
Tuesday, January 31, 2012
Quasars- A Hot Topic
Okay, terrible pun. We're off to a bad start.
I find celestial objects such as stars, black holes, and quasars to be very fascinating, so I will be doing a series of posts relating to them, one at a time. I find the observation of phenomena to be preferable to long calculations, sot it all works out. Anyway, Quasars.
"What is a quasar?"
Thanks for asking, hypothetical reader. Quasars are extremely bright objects seen in other galaxies, far brighter than anything around them. In fact, the brightest quasars have luminosities exceeding that of entire galaxies. Like most super-hot objects, such as stars and active galaxies, they give off radiation. In particular, quasars give off large amounts of X-rays and radio waves. Like blackbody radiators, older quasars have absorption ranges due to surrounding dust and gas. Newer quasars, however, do not.
"That's what quasars do, I asked what they are."
Sorry, I got a little off track. Long story short, quasars are a side-effect of a black hole. When a black hole pulls in huge amounts of gas and dust, that material can begin orbiting the black hole at extreme speeds, sometimes approaching the speed of light. In the process, this material can give off large amounts of radiation. This is because in the presence of magnetic fields, these fast-moving particles will radiate radio waves in a process called "Synchotron Radiation." These quasi-stellar radio sources, of "quasars," are usually at center of a galaxy, having formed around a super-massive black hole. Super-massive black holes are usually hundreds of thousands or even millions of solar masses in mass.
"What does that look like?"
Here you go.
In this image, you can see the superheated gas spiraling into a black hole, which, obviously, can't be seen, but is at the center. The white line coming from the center at about 100 degrees is called a jet, and, as I intend to talk about them in another post, I won't say anything now.
This particular image illustrates a particularly bright quasar discovered by the European Southern Observatory, or ESO. The mass of this quasar is around two billion solar masses, and is the brightest early-universe object yet discovered.
Quasars are generally so bright that they entirely obscure the galaxy around them. This is rather impressive, given that they are actually much, much smaller than their host galaxy. This is due to a number of factors. First, even the nearest quasars are quite distant, between 600 million and 28 billion lightyears away. This distance makes it difficult to resolve these objects. The other reason is simply because they are so absurdly bright compared to their surroundings. The brightest readily apparent quasar is "3C 273," which is located in the Virgo constellation, as well as having a catchy name. It has an apparent magnitude of 12.8, which is bright enough to be seen through a common telescope. Combining the extreme distance of some quasars with their great brightness makes it quite difficult to resolve the galaxy around them from the quasar itself.
"Where do quasars come from?"
Good question, hypothetical reader. So good, in fact, that nobody knows the answer. You see, existing quasars are very old, as they are only seen in developing galaxies. It is entirely possible that many of the quasars we observe no longer exist, and we're only seeing their light trail.
"No longer exist? Where do they go?"
Well, since quasars are gas and dust spiraling into black holes, eventually they simply run out of material. When this happens, there isn't any dust left to radiate, so the quasar goes quiet, and all that is left is a super-massive black hole. Quasars are certainly capable of taking a lot of material with them. The brightest ones can consume 1000 solar masses annually, and the largest can consume 600 earth masses per minute. I'm just glad we're not near one.
All in all, quasars are interesting structures, very different from the stars and planets we're used to observing. Being so old, they give a glimpse into the early universe. Perhaps I'll do a follow-up post describing exactly what they tell us about way-back-when sometime.
Until then, thanks for ready, and later.
I find celestial objects such as stars, black holes, and quasars to be very fascinating, so I will be doing a series of posts relating to them, one at a time. I find the observation of phenomena to be preferable to long calculations, sot it all works out. Anyway, Quasars.
"What is a quasar?"
Thanks for asking, hypothetical reader. Quasars are extremely bright objects seen in other galaxies, far brighter than anything around them. In fact, the brightest quasars have luminosities exceeding that of entire galaxies. Like most super-hot objects, such as stars and active galaxies, they give off radiation. In particular, quasars give off large amounts of X-rays and radio waves. Like blackbody radiators, older quasars have absorption ranges due to surrounding dust and gas. Newer quasars, however, do not.
"That's what quasars do, I asked what they are."
Sorry, I got a little off track. Long story short, quasars are a side-effect of a black hole. When a black hole pulls in huge amounts of gas and dust, that material can begin orbiting the black hole at extreme speeds, sometimes approaching the speed of light. In the process, this material can give off large amounts of radiation. This is because in the presence of magnetic fields, these fast-moving particles will radiate radio waves in a process called "Synchotron Radiation." These quasi-stellar radio sources, of "quasars," are usually at center of a galaxy, having formed around a super-massive black hole. Super-massive black holes are usually hundreds of thousands or even millions of solar masses in mass.
"What does that look like?"
Here you go.
This particular image illustrates a particularly bright quasar discovered by the European Southern Observatory, or ESO. The mass of this quasar is around two billion solar masses, and is the brightest early-universe object yet discovered.
Quasars are generally so bright that they entirely obscure the galaxy around them. This is rather impressive, given that they are actually much, much smaller than their host galaxy. This is due to a number of factors. First, even the nearest quasars are quite distant, between 600 million and 28 billion lightyears away. This distance makes it difficult to resolve these objects. The other reason is simply because they are so absurdly bright compared to their surroundings. The brightest readily apparent quasar is "3C 273," which is located in the Virgo constellation, as well as having a catchy name. It has an apparent magnitude of 12.8, which is bright enough to be seen through a common telescope. Combining the extreme distance of some quasars with their great brightness makes it quite difficult to resolve the galaxy around them from the quasar itself.
"Where do quasars come from?"
Good question, hypothetical reader. So good, in fact, that nobody knows the answer. You see, existing quasars are very old, as they are only seen in developing galaxies. It is entirely possible that many of the quasars we observe no longer exist, and we're only seeing their light trail.
"No longer exist? Where do they go?"
Well, since quasars are gas and dust spiraling into black holes, eventually they simply run out of material. When this happens, there isn't any dust left to radiate, so the quasar goes quiet, and all that is left is a super-massive black hole. Quasars are certainly capable of taking a lot of material with them. The brightest ones can consume 1000 solar masses annually, and the largest can consume 600 earth masses per minute. I'm just glad we're not near one.
All in all, quasars are interesting structures, very different from the stars and planets we're used to observing. Being so old, they give a glimpse into the early universe. Perhaps I'll do a follow-up post describing exactly what they tell us about way-back-when sometime.
Until then, thanks for ready, and later.
Monday, January 23, 2012
Astronomy? Why?
It's a fair question. To many, the importance of astronomy isn't readily apparent. However, upon closer inspection, it becomes clearer as to exactly why astronomy is valuable, and how varied the jobs of astronomers can be.
Without prior knowledge, its easy to dismiss astronomy as "stargazing." However, when you realize just how valuable this field of study can be, you may change your opinion. Studying nearby celestial objects can give insights into how our solar system works, and studying our moon can give hints as to how our own planet formed. By understanding the reactions within our own sun, we can better harness the sun's rays for our own use. In the past, studying nearby planets such as mars has given us insight into how life may evolve on other planets.
Beyond our own solar system, we can also study distant planets and stars. By studying distant planets we can search for other inhabitable places. We can also gain an understanding of types of stars other than our own, black holes, and other distant objects.
The Job of an astronomer is varied, and there are actually quite a few unique jobs that could be called astronomy. There are the obvious jobs, such as searching for celestial objects using either earth-bound or orbiting telescopes. However, other astronomers study information returned by long-range ships sent out to investigate nearby planets, such as the Mars rovers or the planetary probes to Jupiter, Saturn, and the other outlying planets. There are even some astronomers who never so much as touch a telescope, as, because astronomy is a physics-based field, there are many computations that need to be done. Some astronomers are simply mathematicians who crunch astronomy-related numbers.
All in all, I look forward to seeing what other sort of purposes astronomy can serve.
Without prior knowledge, its easy to dismiss astronomy as "stargazing." However, when you realize just how valuable this field of study can be, you may change your opinion. Studying nearby celestial objects can give insights into how our solar system works, and studying our moon can give hints as to how our own planet formed. By understanding the reactions within our own sun, we can better harness the sun's rays for our own use. In the past, studying nearby planets such as mars has given us insight into how life may evolve on other planets.
Beyond our own solar system, we can also study distant planets and stars. By studying distant planets we can search for other inhabitable places. We can also gain an understanding of types of stars other than our own, black holes, and other distant objects.
The Job of an astronomer is varied, and there are actually quite a few unique jobs that could be called astronomy. There are the obvious jobs, such as searching for celestial objects using either earth-bound or orbiting telescopes. However, other astronomers study information returned by long-range ships sent out to investigate nearby planets, such as the Mars rovers or the planetary probes to Jupiter, Saturn, and the other outlying planets. There are even some astronomers who never so much as touch a telescope, as, because astronomy is a physics-based field, there are many computations that need to be done. Some astronomers are simply mathematicians who crunch astronomy-related numbers.
All in all, I look forward to seeing what other sort of purposes astronomy can serve.
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