There is no danger in the planet impacting on the star. For this you would have to invoke some mechanism that is able to get rid of the planet's orbital angular momentum, which is very difficult to acheive. So, while the planet is close to its star, it is in no danger of falling in - only very much in the future once the star leaves the main sequence and becomes a red giant. But that's some billion years in the future... (as an aside, a similar misconception is that if a star suddenly turns supernova and becomes a black hole, many people believe that planets surrounding that star would get "sucked in". For the same reason, that's not a problem either). Note that Mercury in our solar system has an 88d orbit, and has happily lived there for 4.5 billion years.
What is more worrisome is that the planet gets heated up due to its proximity to the star and is evaporated. But again, planets have an awful amount of mass, so this shouldn't be too much of a problem either. For example, there is a 4.4 jupiter masses planet around Tau Bootis, in a 3.3d orbit (http://www.exoplaneten.de/tauboo/english.html), but the general estimate for objects of this kind (dubbed "hot jupiters") is that they will survive for billions of years. The reason for this is that the mass loss rate caused by the proximity of the star is still negligible compared to the mass of the planet. Take a look at the article by Ferlet et al., on p. 226 of a recent conference on explanets, the proceedings of which are at http://www.obs-hp.fr/www/pubs/Coll51Peg/proceeding s.html.
You ask a few good questions that merit a longer answer.
First of all, it is important to note that Einstein, in his theory of general relativity, showed that space can be curved. It is only because of this that one can even talk about something like the "diameter" of the universe. In simple GR, and using some fairly broad assumptions about the properties of the universe, there are three principal "shapes" for the universe: the universe can have a "positive curvature" and a finite volume, it can have an infinite volume and be "flat", or it can have a "negative curvature" and an infinite volume.
In three dimensions, these spaces are very difficult to imagine for us humans, but a 2d analogy might make things clearer: The analogy in 2d for a positively curved space is the surface of a sphere, for a flat space it is a plane, and for a negatively curved space a hyperboloid, and the "volume" would be the respective surface area. Note that locally, e.g., for small ants living on a huge sphere (or humans living on the Earth), it is very difficult to distinguish between these three possibilities. For example, it took 1000s of years for humans to realize that the Earth was not a flat disk, just because our Earth is so tremendously big that in our everyday life, its curvature just does not matter to us (unless you are an airline pilot that is...).
In the past 20-30 years, we were able to develop methods that allowed us to infer in what type of universe we live. Essentially, these methods boil down to measuring the amount of gravitating stuff in the universe, which is summarized in a parameter we astronomers call "Omega". If Omega<1, the universe is infinite and open (has an infinite volume), for Omega equals 1 it is flat and open, and for Omega>1 it has a finite volume.
Several measurements, using the Hubble Space Telescope, the Wilkinson Microwave Anisotropy Probe, X-ray data from galaxy clusters measured with ROSAT, XMM-Newton, and Chandra, data taken with balloon experiments etc. have allowed us to build what is called the so-called concordance model of cosmology, i.e. the baseline model that most of the astronomicical community agrees with. This model has an age of around 14 billion years and has Omega=1. This means that in this model the universe is flat and infinite in size. Therefore, giving the "diameter" of the universe for the concordance model, as quoted by the original poster, does not make sense in this model.
Now, astronomers often are sloppy people, and this is especially true for the people who write press releases for NASA, because they have the incredibly difficult job to summarize a piece of very complicated physics in a 1-2 minute sound bite. What is often meant when you read something like "the universe is 100billion light years across" is a statement about that part of the universe that is visible to us. So, consider a photon that was emitted shortly after the big bang. This photon happily moves through space for about 14 billion years, and is eventually detected by us. So, the distance traveled by the photon was 14 billion light years. However, while the photon traveled, the Universe expanded, i.e., it increased in volume. This means that the distance that the source of light has from us now is much larger. It is this distance which is often quoted as the "size of the universe". How far it is depends on the model assumptions one makes, i.e., the expansion history of the universe, but one can get values which are much larger than cT, where c is the speed of light and T the age of the universe.
So much for my very simplified answer of what proves to be far more complicated questions than one might think. I hope it clarified matters a little bit, if you want a little bit more detail, a good WWW page to check out is Ned Wright's cosmology tutorial (http://www.astro.ucla.edu/~wright/cosmo_03.htm).
Although Astrophysics and Space Science is peer reviewed, you should be aware that this journal is not held in very high esteem by the astronomy and astrophysics community (contrary to, e.g., the Astrophysical Journal, Astronomy and Astrophysics, or the Monthly Notices of the Royal Astronomical Society). If you don't believe me, take a look at the impact factor of the journal , which is 0.2, while it is greater than 4 for the renowed astronomical journals (the 2.1 for Astronomy and Astrophysics in the list cited is wrong, but the remaining impact factors for astronomical journals more or less scale with the journal's image in the community).
To understand how this article could be published, you should be aware that for all scientific journals the editor has the last responsibility for accepting a paper, not the peer reviewers. In the case of Astrophysics and Space Science, the editorial board contains N.C. Wickramasinghe, who is one of the inventors of the panspermia theory. So, even although peer reviews might have been dodgy, it could have been an editorial decision to accept this paper.
I happen to know that Astrophysics and Space Science operates this way, as a manuscript I co-reviewed with a PhD student of mine several years ago appeared in the journal without taking any of our recommendations into account. This has not happened to me with any of the 30odd manuscripts I have refereed since and is even more astonishing since the journal decided to print the original manuscript, without even addressing the large number of grammatical mistakes and spelling errors pointed out by us (which were so bad that we, as referees, could not understand what the authors were trying to say). I have declined to referee for Astrophysics and Space Science since and consider the journal a "scientific tabloid" as opposed to a "scientific broadsheet". And you wouldn't believe the "Sun" and the "News of the World" either, right?
So, to conclude, "peer refereed" does not always mean what you might think it does, and although I am not a microbiology specialist, as long as a report on the "red rain" is not accepted by a mainstream journal, would doubt any claims made in the article.
This depends really on where you're working. In many universities the cost of operating the computers COMES out of the budget of the scientists. It is called the "overhead", which is normally between 50-80% of the total value of a typical research grant in the US.
In the UK, where I work, the research councils have just switched over to "full economic costing", and again often the biggest item in research applications is due to FEC. For example, for a typical application for a postdoctoral position, the annual salary will be on the order of 20-25kGBP, while the FEC for office space, secretarial and other janitorial support, computing etc., is about the same per year. So, no, when applying for research grants, we do have to take this into account, and it is usually the most dreaded part of a research application and takes up similar amounts of time than writing the scientific justification of a proposal.
Now, if you find a way to hire, e.g., a graduate student, operating the computers might come cheaper than a full blown sysadmin, but even a graduate student will cost you about 25-30k$ per year in the US if you figure in the tuition fees.
So, from this point of view, one can argue that Sun's offer is still expensive, but the operating costs of a research group are not negligible and I think that overall Sun might only be a factor 3 or so more expensive than operating your own computing center.
The real reason why scientists won't jump on Sun's offer is that we have the right to get computing time for free from the national supercomputing centers. If you have a computing intensive project,
getting time there is not too difficult, so there is no need to go to commercial providers.
Of course, this all assumes that this new model using relativity is correct... It probably is, but I think it does need to under go the usual scrutiny just to be sure.
The model has already gone under scrutiny. And, if one believes Mikolaj Korzynski (http://arxiv.org/abs/astro-ph/0508377) been shown to be unphysical. His major criticisms are that the asymptotic behavior of the equations used in the original paper is not correct (in other words, if you remove all matter from the universe, you'd expect to get a flat universe, which you don't) and that there is a thin disk implicitly assumed in the model at the center of the galaxy, which is not physical either.
Even though this is disappointing from a philosophical point of view, the result that the model is unphysical is good because it saves astronomy a lot of trouble.
I think that it is really important to stress here that the evidence for dark matter does not come only from flat rotation curves alone, but that there are many independent methods to determine the presence of gravitational mass, many of which do not depend on any Newtonian assumptions. Had the original result been true, the non-existence of dark matter halos of galaxies would have implied that most of these other independent experiments showing the presence of dark matter, e.g., in galaxy clusters, are be wrong as well. And that would have shaken the foundations of most of modern cosmology.
Well, I have for sure not been living under a rock and am well aware of soft gamma-ray repeaters!
The outburst you refer to (and the earlier ones, seen, e.g., by the Rossi X-ray Timing Explorer), however, was immediately recognized as a SGR outburst, and not as a "short gamma-ray burst". As you correctly say, there is currently a lot of debate in the community whether a fraction of short gamma-ray bursts are in fact due to SGR outbursts in nearby galaxies, however, how large that percentage is is not clear. One of the most careful studies of short gamma-ray bursts available has recently set an upper limit of 4 per cent of all short gamma-ray bursts as being caused by SGR outbursts (Lazzati et al., MNRAS 362, L8, preprint available at http://arxiv.org/abs/astro-ph/?0504308). I think we could argue whether this is a "significant percentage". To be fair, in the original Nature paper on the December outburst, Hurley et al. argue that SGR outbursts could explain a much larger fraction of short gamma-ray bursts.
Overall, however, the debate in the community is still ongoing and therefore I think that at the moment the jury is still out and would still distinguish between SGR flares and short gamma-ray bursts. It is because of this that I stated that I am not aware of any GRB, short or long, that was ever seen from in object in our Galaxy.
(and, yes, I indeed find anomalous X-ray pulsars (which might be magnetars) and other neutron stars with high magnetic fields very exciting objects and have published on them...)
I do research in X-ray and Gamma-Ray astronomy and just wanted to confirm that so far no gamma-ray bursts have ever been observed to come from our own galaxy.
I am sorry, but your explanation is completely wrong. I am an X-ray astronomer working mainly in the area of black hole radiation processes, so I claim some credibility here...
First of all, accretion disks produce what is called thermal radiation ("black body radiation"). That radiation is produced by all material in thermal equilibrium (for example, our Sun's spectrum looks like a black body). In the inner regions of accretion disks around black holes, the typical temperatures are such that soft X-rays with energies of about 1keV are produced, i.e., temperatures of a few million kelvins. At these temperatures the radiating material is almost fully ionized. A large fraction of the primary radiation is produced by a process called bremsstrahlung, where electrons are accelerated in the electric fields of nuclei.
In addition to this primary radiation, harder X-rays are produced by secondary processes. The most important process for accreting black holes is most likely the process called Comptonization. The general picture is that the strong turbulence in the inner region of the accretion disk will result in magnetic reconnection, which is a very efficient process to convert magnetic field energy into kinetic energy. As a result there is a thin plasma of VERY hot electrons surrounding the inner region of the accretion disk. The emission of that plasma itself is negligible, however, X-rays entering the plasma from the accretion disk can be Compton scattered to energies up to those corresponding to the electron temperature, which is a few billion degrees. We can observe these photons with satellites such as NASA's Rossi X-ray Timing Explorer or ESA's INTEGRAL observatory.
So, no, "ripping apart nuclei" is not the process producing the observed X-rays at all, good old atomic physics is all that is required (and, yes, one can compute model spectra for the radiation emitted in such a system and these explain the observations extremely well).
Slashdot Mirror
What is more worrisome is that the planet gets heated up due to its proximity to the star and is evaporated. But again, planets have an awful amount of mass, so this shouldn't be too much of a problem either. For example, there is a 4.4 jupiter masses planet around Tau Bootis, in a 3.3d orbit (http://www.exoplaneten.de/tauboo/english.html), but the general estimate for objects of this kind (dubbed "hot jupiters") is that they will survive for billions of years. The reason for this is that the mass loss rate caused by the proximity of the star is still negligible compared to the mass of the planet. Take a look at the article by Ferlet et al., on p. 226 of a recent conference on explanets, the proceedings of which are at http://www.obs-hp.fr/www/pubs/Coll51Peg/proceeding s.html.
You ask a few good questions that merit a longer answer.
First of all, it is important to note that Einstein, in his theory of general relativity, showed that space can be curved. It is only because of this that one can even talk about something like the "diameter" of the universe. In simple GR, and using some fairly broad assumptions about the properties of the universe, there are three principal "shapes" for the universe: the universe can have a "positive curvature" and a finite volume, it can have an infinite volume and be "flat", or it can have a "negative curvature" and an infinite volume.
In three dimensions, these spaces are very difficult to imagine for us humans, but a 2d analogy might make things clearer: The analogy in 2d for a positively curved space is the surface of a sphere, for a flat space it is a plane, and for a negatively curved space a hyperboloid, and the "volume" would be the respective surface area. Note that locally, e.g., for small ants living on a huge sphere (or humans living on the Earth), it is very difficult to distinguish between these three possibilities. For example, it took 1000s of years for humans to realize that the Earth was not a flat disk, just because our Earth is so tremendously big that in our everyday life, its curvature just does not matter to us (unless you are an airline pilot that is...).
In the past 20-30 years, we were able to develop methods that allowed us to infer in what type of universe we live. Essentially, these methods boil down to measuring the amount of gravitating stuff in the universe, which is summarized in a parameter we astronomers call "Omega". If Omega<1, the universe is infinite and open (has an infinite volume), for Omega equals 1 it is flat and open, and for Omega>1 it has a finite volume.
Several measurements, using the Hubble Space Telescope, the Wilkinson Microwave Anisotropy Probe, X-ray data from galaxy clusters measured with ROSAT, XMM-Newton, and Chandra, data taken with balloon experiments etc. have allowed us to build what is called the so-called concordance model of cosmology, i.e. the baseline model that most of the astronomicical community agrees with. This model has an age of around 14 billion years and has Omega=1. This means that in this model the universe is flat and infinite in size. Therefore, giving the "diameter" of the universe for the concordance model, as quoted by the original poster, does not make sense in this model.
Now, astronomers often are sloppy people, and this is especially true for the people who write press releases for NASA, because they have the incredibly difficult job to summarize a piece of very complicated physics in a 1-2 minute sound bite. What is often meant when you read something like "the universe is 100billion light years across" is a statement about that part of the universe that is visible to us. So, consider a photon that was emitted shortly after the big bang. This photon happily moves through space for about 14 billion years, and is eventually detected by us. So, the distance traveled by the photon was 14 billion light years. However, while the photon traveled, the Universe expanded, i.e., it increased in volume. This means that the distance that the source of light has from us now is much larger. It is this distance which is often quoted as the "size of the universe". How far it is depends on the model assumptions one makes, i.e., the expansion history of the universe, but one can get values which are much larger than cT, where c is the speed of light and T the age of the universe.
So much for my very simplified answer of what proves to be far more complicated questions than one might think. I hope it clarified matters a little bit, if you want a little bit more detail, a good WWW page to check out is Ned Wright's cosmology tutorial (http://www.astro.ucla.edu/~wright/cosmo_03.htm).
To understand how this article could be published, you should be aware that for all scientific journals the editor has the last responsibility for accepting a paper, not the peer reviewers. In the case of Astrophysics and Space Science, the editorial board contains N.C. Wickramasinghe, who is one of the inventors of the panspermia theory. So, even although peer reviews might have been dodgy, it could have been an editorial decision to accept this paper.
I happen to know that Astrophysics and Space Science operates this way, as a manuscript I co-reviewed with a PhD student of mine several years ago appeared in the journal without taking any of our recommendations into account. This has not happened to me with any of the 30odd manuscripts I have refereed since and is even more astonishing since the journal decided to print the original manuscript, without even addressing the large number of grammatical mistakes and spelling errors pointed out by us (which were so bad that we, as referees, could not understand what the authors were trying to say). I have declined to referee for Astrophysics and Space Science since and consider the journal a "scientific tabloid" as opposed to a "scientific broadsheet". And you wouldn't believe the "Sun" and the "News of the World" either, right?
So, to conclude, "peer refereed" does not always mean what you might think it does, and although I am not a microbiology specialist, as long as a report on the "red rain" is not accepted by a mainstream journal, would doubt any claims made in the article.
In the UK, where I work, the research councils have just switched over to "full economic costing", and again often the biggest item in research applications is due to FEC. For example, for a typical application for a postdoctoral position, the annual salary will be on the order of 20-25kGBP, while the FEC for office space, secretarial and other janitorial support, computing etc., is about the same per year. So, no, when applying for research grants, we do have to take this into account, and it is usually the most dreaded part of a research application and takes up similar amounts of time than writing the scientific justification of a proposal.
Now, if you find a way to hire, e.g., a graduate student, operating the computers might come cheaper than a full blown sysadmin, but even a graduate student will cost you about 25-30k$ per year in the US if you figure in the tuition fees.
So, from this point of view, one can argue that Sun's offer is still expensive, but the operating costs of a research group are not negligible and I think that overall Sun might only be a factor 3 or so more expensive than operating your own computing center.
The real reason why scientists won't jump on Sun's offer is that we have the right to get computing time for free from the national supercomputing centers. If you have a computing intensive project, getting time there is not too difficult, so there is no need to go to commercial providers.
Even though this is disappointing from a philosophical point of view, the result that the model is unphysical is good because it saves astronomy a lot of trouble. I think that it is really important to stress here that the evidence for dark matter does not come only from flat rotation curves alone, but that there are many independent methods to determine the presence of gravitational mass, many of which do not depend on any Newtonian assumptions. Had the original result been true, the non-existence of dark matter halos of galaxies would have implied that most of these other independent experiments showing the presence of dark matter, e.g., in galaxy clusters, are be wrong as well. And that would have shaken the foundations of most of modern cosmology.
The outburst you refer to (and the earlier ones, seen, e.g., by the Rossi X-ray Timing Explorer), however, was immediately recognized as a SGR outburst, and not as a "short gamma-ray burst". As you correctly say, there is currently a lot of debate in the community whether a fraction of short gamma-ray bursts are in fact due to SGR outbursts in nearby galaxies, however, how large that percentage is is not clear. One of the most careful studies of short gamma-ray bursts available has recently set an upper limit of 4 per cent of all short gamma-ray bursts as being caused by SGR outbursts (Lazzati et al., MNRAS 362, L8, preprint available at http://arxiv.org/abs/astro-ph/?0504308). I think we could argue whether this is a "significant percentage". To be fair, in the original Nature paper on the December outburst, Hurley et al. argue that SGR outbursts could explain a much larger fraction of short gamma-ray bursts.
Overall, however, the debate in the community is still ongoing and therefore I think that at the moment the jury is still out and would still distinguish between SGR flares and short gamma-ray bursts. It is because of this that I stated that I am not aware of any GRB, short or long, that was ever seen from in object in our Galaxy.
(and, yes, I indeed find anomalous X-ray pulsars (which might be magnetars) and other neutron stars with high magnetic fields very exciting objects and have published on them...)
I do research in X-ray and Gamma-Ray astronomy and just wanted to confirm that so far no gamma-ray bursts have ever been observed to come from our own galaxy.
I am sorry, but your explanation is completely wrong. I am an X-ray astronomer working mainly in the area of black hole radiation processes, so I claim some credibility here...
First of all, accretion disks produce what is called thermal radiation ("black body radiation"). That radiation is produced by all material in thermal equilibrium (for example, our Sun's spectrum looks like a black body). In the inner regions of accretion disks around black holes, the typical temperatures are such that soft X-rays with energies of about 1keV are produced, i.e., temperatures of a few million kelvins. At these temperatures the radiating material is almost fully ionized. A large fraction of the primary radiation is produced by a process called bremsstrahlung, where electrons are accelerated in the electric fields of nuclei.
In addition to this primary radiation, harder X-rays are produced by secondary processes. The most important process for accreting black holes is most likely the process called Comptonization. The general picture is that the strong turbulence in the inner region of the accretion disk will result in magnetic reconnection, which is a very efficient process to convert magnetic field energy into kinetic energy. As a result there is a thin plasma of VERY hot electrons surrounding the inner region of the accretion disk. The emission of that plasma itself is negligible, however, X-rays entering the plasma from the accretion disk can be Compton scattered to energies up to those corresponding to the electron temperature, which is a few billion degrees. We can observe these photons with satellites such as NASA's Rossi X-ray Timing Explorer or ESA's INTEGRAL observatory.
So, no, "ripping apart nuclei" is not the process producing the observed X-rays at all, good old atomic physics is all that is required (and, yes, one can compute model spectra for the radiation emitted in such a system and these explain the observations extremely well).