I do lots of scientific computing (radio astronomy signal processing) on consumer-level NVIDIA cards and it is *all* FP32. These kinds of cards (and the 12GB of mem) could be very useful for my work, and others who do DSP-type of *scientific* computing.
I've read slashdot daily since it started -- it has been a fantastic source of information, ideas, and laughs. Good luck with all your future endeavors.
All of the energy that we see (as well as the energy we don't see, which is the vast majority of it and which comes out in a relativistic particle wind) comes from the rotation of the neutron star. That means that pulsars are flywheels. And amazingly (even to me, and I study them daily), the most energetic pulsars give off tens of thousands of times more power than the total power output of the Sun. And all from rotation. That's crazy.
Actually, they aren't using the GBT's spectrometer. They are using an instrument that I helped to develop for pulsar research called GUPPI, which uses FPGAs and GPUs to real-time process 800MHz of radio bandwidth.
However, in this case they are using GUPPI's GPU nodes to record 800MHz of Nyquist-sampled band centered at 1.5GHz. Each sample is 2-bits, and with 2 polarizations, that is how they get 800MB/s (or almost a GB/s as it says in the article).
If you want some basic info about GUPPI, you can find it here:
The good thing is that the pulsars which glitch are the young ones (hundreds to millions of years old). The pulsars that we are using for NANOGrav are millisecond pulsars which are hundreds of millions or billions of years old, have much smaller magnetic fields than young pulsars, and basically never glitch. They are extremely stable rotators -- much better than normal pulsars.
LaTeX is certainly the standard in physics and astronomy. Of course your point about Unix workstations is correct, as most physics, CS-types, and astronomers use Unix/Linux all the time.
There is no compelling science case for Arecibo that can't be pursued with other telescopes, especially since the frontier of radio astronomy has mostly moved from sensitivity (requiring big apertures) to resolution (requiring long-baseline arrays), or to shorter mm/submm wavelengths that Arecibo can't handle.
Sorry, but that is not true. Radio astronomy needs improvement in a wide variety of areas in order to tackle the tremendously wide variety of science that is done at radio bands. Examples include sensitivity, field-of-view, dynamic range, image fidelity, resolution, and wavelength coverage. But sensitivity is one of the most important. That is why the SKA is on the table to be the world's next generation decameter/centimeter wave radio telescope. The most important thing it provides is sensitivity (i.e. SK = square km = sensitivity). And Arecibo is already a 5-10% SKA.
For my own research (pulsars), Arecibo's sensitivity is what sets it apart. Although, truthfully, the fact that it can't observe any of the southern sky (where most of the pulsars are) is a definite downside.
Finally, you mention surveys and imply that because Arecibo is doing a larger percent of them now that that means it is washed up. However, that also isn't true. Modern astronomy is driven by large surveys (including several of the instruments that you mention, for example, Sloan, PANSTARRS, LSST) as they dramatically increase our discovery space.
I am a scientist and so work with Kelvin all the time. However, I think that Fahrenheit is actually a more useful temperature scale for humans than Celsius. Basically, 0F is wicked cold and 100F is wicked hot. It makes sense for how _we_ relate to temperature rather than how water relates to temperature.
For the triple scenario you never have to capture a pulsar. You only have to have the triple stellar system survive the supernova that created the neutron star (i.e. pulsars are neutron stars) and then subsequently, one of the other stars has to "recycle" the neutron star into a millisecond pulsar via accretion. The recycling process happens when a "normal" main-sequence star evolves into a red giant and dumps its outer envelope into a disk around a companion neutron star. When recycling is finished, you are left with a pulsar-white dwarf "binary" in a close-in orbit, and a main-sequence star orbiting both of those in a much larger orbit.
Scott
PS: Note that there is a another slightly different triple scenario that we mention in the paper where, continuing from above, the pulsar ablates away its white dwarf companion with a relativistic wind over a billion years or so and we are left with the pulsar main-sequence binary that we apparently see now.
You are correct that you need a dissipation mechanism to capture a pulsar into a new orbit.
For this system, assuming it started out in the dense stellar environment in a globular cluster, exchange encounters between multiple stars (3 or 4, i.e. single-binary or binary-binary) can provide the dissipation since the lowest mass stars (i.e. not the pulsar) tend to get energy boosts and are then ejected from the encounter. Alternatively, as you suggest, tides during a very close encounter can lead to a capture.
However, for this system, we have reasons for thinking that a triple system origin is a better explanation than an exchange encounter and subsequent ejection from a globular cluster (all this is described in the paper which will be available on the arXiv tomorrow night and which is on the Science website now).
Maybe, but can government really afford to be as independent of science as possible? Of course. This is necessarily true. There's always more than one way to do things. Federal funding of science allows the funding of basic research. Corporations and private organizations almost never want to fund basic research because practical results (which equal money) are not guaranteed, and if they do come, they can be a long time in coming. However, basic research is how major breakthroughs in science happen and also how many students get interested in science in the first place. It is a long term investment.
Only if you think the government should have such complete control over society, if you believe that this is necessary or wise because people cannot be trusted on their own to make decisions in their own best interest over the long term. I reject such notions. Just because the government funds science doesn't mean that corporations and private organizations can't fund it. They do, just at much lower levels.
And it is why we have a Tenth Amendment to limit the power of the federal government, which most funding of science violates. Hmmm. I'm certainly not an expert in Constitutional Law (actually, I'm a scientist funded by the NSF!), but Article 1, Section 8 seems to fit nicely: "The Congress shall have power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States;" Science definitely provides for the "general Welfare of the U.S.".
I served in the US Army for 10 years and your post is complete crap, and in fact actually offends me.
I firmly believe that the Bill of Rights expresses the rights that _every_ person _should_ have. These are _human_ rights that the Constitution speaks of, not just US Citizen's rights. I would have been completely happy going to war to defend those rights of non-US citizens in the case of a serious injustice (think first gulf war).
The fact the that US is (supposedly) for upholding those rights is one of the great things about this nation. However, the way that we've done things recently makes my stomach turn.
Actually, this is not the smallest planet yet found. The first extrasolar planets are still the smallest known: the planets around the millisecond pulsar B1257+12: http://en.wikipedia.org/wiki/PSR_B1257+12
The optical planet hunters often conveniently forgot this system (or dismiss it for various reasons).
I might sound like I'm trying to protect the boss given where I work, but that is not the case. The fact is, your view that NRAO tried to get earmarks is not correct. Did we (actually our managing organization AUI) lobby congress for funds? Yes. But ask for earmarks? No. The fact is, there are two very influential senators (one in WV and the other in NM, where our main telescopes are) that _really_ want to bring money to their districts. When they hear that "their" observatories have a problem (like the GBT's track problems), they want to fix it. This is how earmarks come about.
Do you honestly think that we like to take a heap of flak from the rest of the astronomical community and endanger our future funding?
...in the 90's when I was an exchange cadet at the US Air Force Academy. They gave us a tour of the place -- it really was quite amazing.
The coolest thing was seeing all the "buildings" in there (yes, it is like a big open cave with buildings inside) mounted on massive steel springs. Also cool was seeing that the main access shaft goes (IIRC) completely through the mountain. The internal rooms are built behind a massive blast door or two (i.e. huge bank-vault-style doors) off to the side of the tunnel. That is to let a blast wave pass right through the mountain supposedly and not just bash against the blast doors.
The most disappointing thing was finding out that the War Room was nothing like in the movies -- it is a tiny room about the size of a normal living room stuffed with computers (no "big board" or giant screens). There are only about 6-10 people working in there at any one time (lead by a one-star general/admiral).
While you are right that most radio telescopes do not transmit, there are some that most certainly do. The world's largest radio telescope, Arecibo, houses 2 very powerful radar transmitters -- one of which is capable of a megawatt of transmission power! It uses these (either by itself or with other huge telescopes like the GBT receiving) for making radar measurements of planets, moons, asteroids, comets etc.
The reason why they are called failed suns is because they are. Gravity pulls the matter in towards the center of the planet. This makes the center hot and dense (think ideal gas law). If there is enough mass in the planet, the gravitational attraction is strong enough that it forces the pressure and temperature at the planets core to exceed the thresholds required for nuclear fusion (hydrogen to hydrogen) to occur. If the body is massive enough to do this it is a bona-fide star. Stars slightly less massive are known as brown dwarfs (there are technical reasons why they are not called planets), and bodies even less massive are planets.
Jupiter is giving off heat because the gravitational attraction is causing the temperature and pressure inside the star to be relatively high -- just not high enough for fusion.
Nice post. You beat me to it. I am, in fact, one of those astronomers studying binary pulsars and even PSR J0737-3039 in particular. You are very correct when you state that these things will collide -- we can easily measure the decay of the orbital period over a time-span of a couple years.
One small nit-pick, though: J0737-3039 is not the first binary pulsar known (that was PSR B1913+16 which eventually led to the Nobel prize). J0737 is the first double pulsar known (i.e. where both neutron stars are active radio pulsars instead of just one as in B1913+16's case).
Slashdot Mirror
I do lots of scientific computing (radio astronomy signal processing) on consumer-level NVIDIA cards and it is *all* FP32. These kinds of cards (and the 12GB of mem) could be very useful for my work, and others who do DSP-type of *scientific* computing.
Yet another /. meme? And not even a very funny one at that....
* back to lurking *
I've read slashdot daily since it started -- it has been a fantastic source of information, ideas, and laughs. Good luck with all your future endeavors.
Scott
All of the energy that we see (as well as the energy we don't see, which is the vast majority of it and which comes out in a relativistic particle wind) comes from the rotation of the neutron star. That means that pulsars are flywheels. And amazingly (even to me, and I study them daily), the most energetic pulsars give off tens of thousands of times more power than the total power output of the Sun. And all from rotation. That's crazy.
Damn the Universe is cool.
Actually, they aren't using the GBT's spectrometer. They are using an instrument that I helped to develop for pulsar research called GUPPI, which uses FPGAs and GPUs to real-time process 800MHz of radio bandwidth.
However, in this case they are using GUPPI's GPU nodes to record 800MHz of Nyquist-sampled band centered at 1.5GHz. Each sample is 2-bits, and with 2 polarizations, that is how they get 800MB/s (or almost a GB/s as it says in the article).
If you want some basic info about GUPPI, you can find it here:
https://safe.nrao.edu/wiki/bin/view/CICADA/NGNPP
I'm certainly one of them (thanked him for Cosmos in my PhD thesis specifically).
And I agree with you about Demon-Haunted World. I think that should be required reading for all high school students.
The good thing is that the pulsars which glitch are the young ones (hundreds to millions of years old). The pulsars that we are using for NANOGrav are millisecond pulsars which are hundreds of millions or billions of years old, have much smaller magnetic fields than young pulsars, and basically never glitch. They are extremely stable rotators -- much better than normal pulsars.
LaTeX is certainly the standard in physics and astronomy. Of course your point about Unix workstations is correct, as most physics, CS-types, and astronomers use Unix/Linux all the time.
There is no compelling science case for Arecibo that can't be pursued with other telescopes, especially since the frontier of radio astronomy has mostly moved from sensitivity (requiring big apertures) to resolution (requiring long-baseline arrays), or to shorter mm/submm wavelengths that Arecibo can't handle.
Sorry, but that is not true. Radio astronomy needs improvement in a wide variety of areas in order to tackle the tremendously wide variety of science that is done at radio bands. Examples include sensitivity, field-of-view, dynamic range, image fidelity, resolution, and wavelength coverage. But sensitivity is one of the most important. That is why the SKA is on the table to be the world's next generation decameter/centimeter wave radio telescope. The most important thing it provides is sensitivity (i.e. SK = square km = sensitivity). And Arecibo is already a 5-10% SKA.
For my own research (pulsars), Arecibo's sensitivity is what sets it apart. Although, truthfully, the fact that it can't observe any of the southern sky (where most of the pulsars are) is a definite downside.
Finally, you mention surveys and imply that because Arecibo is doing a larger percent of them now that that means it is washed up. However, that also isn't true. Modern astronomy is driven by large surveys (including several of the instruments that you mention, for example, Sloan, PANSTARRS, LSST) as they dramatically increase our discovery space.
As an honest question, what useful things has Aricebo produced?
How about a Nobel prize? (Amongst a bunch of other excellent bits of radio astronomy, aeronomy, and planetary science).
http://en.wikipedia.org/wiki/PSR_B1913+16
I am a scientist and so work with Kelvin all the time. However, I think that Fahrenheit is actually a more useful temperature scale for humans than Celsius. Basically, 0F is wicked cold and 100F is wicked hot. It makes sense for how _we_ relate to temperature rather than how water relates to temperature.
For the triple scenario you never have to capture a pulsar. You only have to have the triple stellar system survive the supernova that created the neutron star (i.e. pulsars are neutron stars) and then subsequently, one of the other stars has to "recycle" the neutron star into a millisecond pulsar via accretion. The recycling process happens when a "normal" main-sequence star evolves into a red giant and dumps its outer envelope into a disk around a companion neutron star. When recycling is finished, you are left with a pulsar-white dwarf "binary" in a close-in orbit, and a main-sequence star orbiting both of those in a much larger orbit.
Scott
PS: Note that there is a another slightly different triple scenario that we mention in the paper where, continuing from above, the pulsar ablates away its white dwarf companion with a relativistic wind over a billion years or so and we are left with the pulsar main-sequence binary that we apparently see now.
You are correct that you need a dissipation mechanism to capture a pulsar into a new orbit.
For this system, assuming it started out in the dense stellar environment in a globular cluster, exchange encounters between multiple stars (3 or 4, i.e. single-binary or binary-binary) can provide the dissipation since the lowest mass stars (i.e. not the pulsar) tend to get energy boosts and are then ejected from the encounter. Alternatively, as you suggest, tides during a very close encounter can lead to a capture.
However, for this system, we have reasons for thinking that a triple system origin is a better explanation than an exchange encounter and subsequent ejection from a globular cluster (all this is described in the paper which will be available on the arXiv tomorrow night and which is on the Science website now).
Scott
I served in the US Army for 10 years and your post is complete crap, and in fact actually offends me.
I firmly believe that the Bill of Rights expresses the rights that _every_ person _should_ have. These are _human_ rights that the Constitution speaks of, not just US Citizen's rights. I would have been completely happy going to war to defend those rights of non-US citizens in the case of a serious injustice (think first gulf war).
The fact the that US is (supposedly) for upholding those rights is one of the great things about this nation. However, the way that we've done things recently makes my stomach turn.
Hey Derek: What telescope did you use?
BTW: why "renard'?
Actually, this is not the smallest planet yet found. The first extrasolar planets are still the smallest known: the planets around the millisecond pulsar B1257+12: http://en.wikipedia.org/wiki/PSR_B1257+12
The optical planet hunters often conveniently forgot this system (or dismiss it for various reasons).
Hey Miguel,
Nice summary.
Scott
Arecibo remains the world's most sensitive radio telescope.
That is very true -- if your source happens to be in the ~30% of the sky that Arecibo can observe....
Scott
I might sound like I'm trying to protect the boss given where I work, but that is not the case. The fact is, your view that NRAO tried to get earmarks is not correct. Did we (actually our managing organization AUI) lobby congress for funds? Yes. But ask for earmarks? No. The fact is, there are two very influential senators (one in WV and the other in NM, where our main telescopes are) that _really_ want to bring money to their districts. When they hear that "their" observatories have a problem (like the GBT's track problems), they want to fix it. This is how earmarks come about.
Do you honestly think that we like to take a heap of flak from the rest of the astronomical community and endanger our future funding?
Scott
...in the 90's when I was an exchange cadet at the US Air Force Academy. They gave us a tour of the place -- it really was quite amazing.
The coolest thing was seeing all the "buildings" in there (yes, it is like a big open cave with buildings inside) mounted on massive steel springs. Also cool was seeing that the main access shaft goes (IIRC) completely through the mountain. The internal rooms are built behind a massive blast door or two (i.e. huge bank-vault-style doors) off to the side of the tunnel. That is to let a blast wave pass right through the mountain supposedly and not just bash against the blast doors.
The most disappointing thing was finding out that the War Room was nothing like in the movies -- it is a tiny room about the size of a normal living room stuffed with computers (no "big board" or giant screens). There are only about 6-10 people working in there at any one time (lead by a one-star general/admiral).
While you are right that most radio telescopes do not transmit, there are some that most certainly do. The world's largest radio telescope, Arecibo, houses 2 very powerful radar transmitters -- one of which is capable of a megawatt of transmission power! It uses these (either by itself or with other huge telescopes like the GBT receiving) for making radar measurements of planets, moons, asteroids, comets etc.
You can read more about it here:
http://www.naic.edu/~pradar/pradar.htm
And yes, IAARA.
My guess would be that by "bigger" they actually mean more massive.
Yes. And IIRC, the threshold is something like 15-20 Jupiter masses. So that is why this one is "definitively" a planet.
Note: IAAA
The reason why they are called failed suns is because they are. Gravity pulls the matter in towards the center of the planet. This makes the center hot and dense (think ideal gas law). If there is enough mass in the planet, the gravitational attraction is strong enough that it forces the pressure and temperature at the planets core to exceed the thresholds required for nuclear fusion (hydrogen to hydrogen) to occur. If the body is massive enough to do this it is a bona-fide star. Stars slightly less massive are known as brown dwarfs (there are technical reasons why they are not called planets), and bodies even less massive are planets.
Jupiter is giving off heat because the gravitational attraction is causing the temperature and pressure inside the star to be relatively high -- just not high enough for fusion.
Nice post. You beat me to it. I am, in fact, one of those astronomers studying binary pulsars and even PSR J0737-3039 in particular. You are very correct when you state that these things will collide -- we can easily measure the decay of the orbital period over a time-span of a couple years.
One small nit-pick, though: J0737-3039 is not the first binary pulsar known (that was PSR B1913+16 which eventually led to the Nobel prize). J0737 is the first double pulsar known (i.e. where both neutron stars are active radio pulsars instead of just one as in B1913+16's case).