Posted on 04/10/2002 5:40:58 PM PDT by PatrickHenry
WASHINGTON (Reuters) - Two weird stars -- one too cold, the other too small to fit known astronomical models -- show evidence for a completely new form of matter, astronomers said on Wednesday.
Scientists believe these stars could be made not of atoms, or even of the sub-atomic particles called neutrons, but of free-floating sub-sub-atomic particles called quarks, and strange quarks at that.
NASA (news - web sites)'s Chandra X-ray Observatory considered the oddball objects by looking at the high level of X-rays they emit. At first, astronomers thought these might be neutron stars, which before this discovery (news - web sites) were the most extreme form of matter known.
Neutron stars are left after big stars explode in blasts called supernovae, and their cores collapse in on themselves. Neutron stars are almost unimaginably dense: a teaspoon of neutron star material weighs a billion tons (1.016 billion tonnes), or as much as all cars, trucks and buses on Earth.
That is because they are composed only of neutrons crammed together, unlike every bit of earthly matter, which is made up of atoms containing neutrons, protons and electrons with lots of space in between.
Astronomers believe the two stars they studied could be even denser that that. Instead of being made of neutrons, they could be made of quarks. Neutrons in a neutron star are made of quarks, but bundled together in relatively roomy groups of so-called confined quarks.
The two stars under observation could be made up of free quarks huddled together, which take up even less space than confined quarks. If that proves true, they would be what astronomers call strange quark stars, objects which have existed so far only in theory.
SMALL, COLD AND EXOTIC
One piece of evidence for this is one of the stars' extremely small size, Jeremy Drake said at a National Aeronautics and Space Administration briefing.
"Until now we've sought to understand nature on the tiniest of scales, involving experiments to look at matter in finer and finer detail," said Drake, of the Harvard-Smithsonian Center for Astrophysics. He said these current observations "might provide a new window on the nature of matter on the tiniest of scales."
His team studied an object known as RXJ 1856, in the constellation Corona Australis, about 400 light-years from Earth. A light-year is the distance light travels in a year, about 6 trillion miles.
Astronomers figured this was a neutron star, but then used the Chandra observatory and the Hubble Space Telescope (news - web sites) to determine its size, which was 10 miles or less in diameter -- below the lower size limit for neutron stars, which range from 12 miles to 20 miles across.
One way to produce such a tiny star, Drake said, would be to squeeze a neutron star down to its constituent quarks, creating a strange quark star.
In the case of the second odd star, astronomer David Helfand of Columbia University studied an object known as 3C58, which is located in the constellation Cassiopeia and is about 10,000 light-years from Earth.
Astronomers in Asia became aware of this object in 1181 when it flamed out as a supernova, Helfand said. Going on this historical record, present-day astronomers calculated that the remnant star should have cooled down to about 35.6 million degrees Fahrenheit by now. In fact, Helfand said, it is only about 1 million degrees C., making it too cool for a neutron star.
Even a neutron star's density would not be enough to squeeze particles out of this object fast enough to cool it down to this temperature, Helfand said. 3C58 would have to be as much as five times as dense for this to happen.
"Our observation suggests that the core of this object is made of a new kind of exotic material," Helfand said.
Populated by jumbo shrimp.
Would a "strange quark" star have the same upper limit on it's mass as does a neutron star, beyond which the self-gravitation becomes so strong that NO force of nature can prevent complete gravitational collapse, i.e., it forms a Black Hole?
One thing I find most interesting about the new objects is that they are so relatively close, and thus, existing in our present time.
Truly exotic objects like these would seem more at home in the far distance (and distant past).
That is the difference between a wormhole and a black hole.
Someday, we may be able to use wormholes to travel through
folded space and get past the speed limit set by light going
from point to point. Don't try that in a black hole, as there
remains, at the very least, a collapsed star down there, ie, matter.
A wormhole is supposedly an unimpeded tunnel.
They probably had to recall an employee who was pre-Jschool to write this up.
The only radius you can talk about on a black hole is the event horizon, which is not the diameter of the massive part but the region from which no light can escape. The strange quark star has some finite (but incredibly high) density. A black hole seems to have infinite density for all anyone can tell; there is nothing so far known to stop the collapse.
The thing is, the laws of physics we have don't really work at the singularity. And there is no way to sneak a look at what's going on beyond the event horizon. So it's hard to say when or if we'll ever understand what's going on inside black holes.
Actually, I was thinking he was really old and hadn't been keeping up with science since Captain Video was on the air.
It's getting to where they're finding new kinds of objects before I hear they're even looking for them.
Now you've started me thinking. If such stars are common, is it concievable that at a larger level they form their own kind of atoms? The distances between such particles may be analogous to those in "conventional" atoms. Stellar clusters may be considered to be atoms, with lots of trivial debris (of which we are made). Galaxies may be molecules, etc. (Or, on the other hand, perhaps my mind has come unhinged due to the recent transition to daylight saving time.)
I think this was discussed in Donald Sutherland's bathroom in "Animal House".
Nah. It's just the Bohr model coming full-circle. If you can think of electrons as travelling around in little orbits like heavenly bodies, then why not the other way around? It's a question of whether it's useful to think of it that way.
Politics. Congress wanted to give the appearance of fiscal restraint while it shovelled everything it could into the redistribution trough.
This strange quark star is not being called a black hole.
It's not a black hole.
That makes one wonder what a black hole would be composed of.
It's made of whatever fell into it.
It's really a very old concept in SF. Almost as soon as the "solar system like" model of the atom was discovered, the stories began to appear. But actually discovering stars which can be considered subatomic particals revives and refreshes the hoary old idea.
But for it to be viable, there would have to be forces that would act as analogs for the Strong and Weak atomic Forces. You'd also need something to act as the Humongus Atom equivalent of the Heisenburg Uncertainty and Pauli Excusion Principles, and find some way for QM effects to be dominant at the size of an object that is as big as a star.
In short, it going to take alot of razzle-dazzle to float this boat.
Is RX J185635-375 a Quark Star?
New Constraints on Neutron Star Cooling from Chandra Observations of 3C58
They are kind of readable. Sort of. Give it a shot...
"If it's a quark star it's spectacular, but there's absolutely no evidence for that," Walter says. There is an alternative explanation: that variation in the star's temperature makes it hard to estimate its diameter. The probability of this is less than 10%, as it would require the hottest part of the star to be pointing straight at Earth. "These results are not definitive," agrees Michael Turner, an astrophysicist at the University of Chicago. Studies of other bodies are needed to confirm whether quark stars really exist, he says.Chandra's observations do show how the extreme regions of space can be used to test physical theories, adds Turner. "We can use the Universe as a heavenly laboratory."
Neutron stars are the collapsed cores of some massive stars. They pack roughly the mass of our Sun into a region the size of a cityAt these incredibly high densities, you could cram all of humanity into a volume the size of a sugar cube. Naturally, the people thus crammed wouldn't survive in their current form, and neither does the matter that forms the neutron star.
This matter, which starts out in the original star as a normal, well-adjusted combination of electrons, protons, and neutrons, finds its peace (aka a lower energy state) as almost all neutrons in the neutron star. These stars also have the strongest magnetic fields in the known universe. The strongest inferred neutron star fields are nearly a hundred trillion times stronger than Earth's fields, and even the feeblest neutron star magnetic fields are a hundred million times Earth's, which is a hundred times stronger that any steady field we can generate in a laboratory. Neutron stars are extreme in many other ways, too. For example, maybe you get a warm feeling when you contemplate high-temperature superconductors, with critical temperatures around 100 K? Hah! The protons in the center of neutron stars are believed to become superconducting at 100 million K, so these are the real high-T_c champs of the universe.
All in all, these extremes mean that the study of neutron stars affords us some unique glimpses into areas of physics that we couldn't study otherwise.
So, like, how do we get neutron stars? Neutron stars are believed to form in supernovae such as the one that formed the Crab Nebula, and the stars that eventually become neutron stars are thought to start out with about 15 to 30 times the mass of our sun. These numbers are probably going to change as supernova simulations become more precise, but it appears that for initial masses much less than 15 solar masses the star becomes a white dwarf, whereas for initial masses a lot higher than 30 solar masses you get a black hole instead. In any case, the basic idea is that when the central part of the star fuses its way to iron, it can't go any farther because at low pressures iron 56 has the highest binding energy per nucleon of any element, so fusion or fission of iron 56 requires an energy input. Thus, the iron core just accumulates until it gets to about 1.4 solar masses (the "Chandrasekhar mass"), at which point the electron degeneracy pressure that had been supporting it against gravity gives up the ghost and collapses inward.
At the very high pressures involved in this collapse, it is energetically favorable to combine protons and electrons to form neutrons plus neutrinos. The neutrinos escape after scattering a bit and helping the supernova happen, and the neutrons settle down to become a neutron star, with neutron degeneracy managing to oppose gravity. Since the supernova rate is around 1 per 30 years, and because most supernovae probably make neutron stars instead of black holes, in the 10 billion year lifetime of the galaxy there have probably been 10^8 to 10^9 neutron stars formed. One other way, maybe, of forming neutron stars is to have a white dwarf accrete enough mass to push over the Chandrasekhar mass, causing a collapse. This is speculative, though, so I won't talk about it further.
The guts of a neutron star We'll talk about neutron star evolution in a bit, but let's say you take your run of the mill mature neutron star, which has recovered from its birth trauma. What is its structure like? First, the typical mass of a neutron star is about 1.4 solar masses, and the radius is probably about 10 km. By the way, the "mass" here is the gravitational mass (i.e., what you'd put into Kepler's laws for a satellite orbiting far away). This is distinct from the baryonic mass, which is what you'd get if you took every particle from a neutron star and weighed it on a distant scale. Because the gravitational redshift of a neutron star is so great, the gravitational mass is about 20% lower than the baryonic mass.
Anyway, imagine starting at the surface of a neutron star and burrowing your way down. The surface gravity is about 10^11 times Earth's, and the magnetic field is about 10^12 Gauss, which is enough to completely mess up atomic structure: for example, the ground state binding energy of hydrogen rises to 160 eV in a 10^12 Gauss field, versus 13.6 eV in no field. In the atmosphere and upper crust, you have lots of nuclei, so it isn't primarily neutrons yet. At the top of the crust, the nuclei are mostly iron 56 and lighter elements, but deeper down the pressure is high enough that the equilibrium atomic weights rise, so you might find Z=40, A=120 elements eventually. At densities of 10^6 g/cm^3 the electrons become degenerate, meaning that electrical and thermal conductivities are huge because the electrons can travel great distances before interacting.
Deeper yet, at a density around 4x10^11 g/cm^3, you reach the "neutron drip" layer. At this layer, it becomes energetically favorable for neutrons to float out of the nuclei and move freely around, so the neutrons "drip" out. Even further down, you mainly have free neutrons, with a 5%-10% sprinkling of protons and electrons. As the density increases, you find what has been dubbed the "pasta-antipasta" sequence. At relatively low (about 10^12 g/cm^3) densities, the nucleons are spread out like meatballs that are relatively far from each other. At higher densities, the nucleons merge to form spaghetti-like strands, and at even higher densities the nucleons look like sheets (such as lasagna). Increasing the density further brings a reversal of the above sequence, where you mainly have nucleons but the holes form (in order of increasing density) anti-lasagna, anti-spaghetti, and anti-meatballs (also called Swiss cheese).
When the density exceeds the nuclear density 2.8x10^14 g/cm^3 by a factor of 2 or 3, really exotic stuff might be able to form, like pion condensates, lambda hyperons, delta isobars, and quark-gluon plasmas. Yes, you say, that's all very well for keeping nuclear theorists employed, but how can we possibly tell if it works out in reality? Well, believe it or not, these things may actually have an effect on the cooling history of the star and their spin behavior!
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