The feeling I have when deciding what to discuss next about this year’s American Astronomical Society meeting is like what I get in a good used bookstore. Where to turn next? We’ve already looked at several stories with exoplanetary significance, but the arrival of a new type of star entirely seems to vault past even these in significance. If, of course, the so-called ‘quark star’ is real, a question sure to remain controversial as the study of extremely bright supernovae continues.
When I say bright, I’m talking about three events in particular, each of which produced one hundred times more light energy than normal supernovae. The events, designated SN2006gy, SN2005gj and SN2005ap, have been under intense scrutiny, among the researchers a team from the University of Calgary, who point to the lack of a satisfactory explanation of these events. The hypothesis they defended at AAS is that neutron stars are not the most compact solid objects known to exist. That honor belongs to still denser quark stars.
Take an average neutron star, maybe sixteen miles across but 1.5 times as massive as the Sun. Produced by the catastrophic collapse of a massive star (and thus associated with the accompanying supernova explosion), neutron stars could theoretically be packed tighter still, the same mass being squeezed to an object just twelve miles across. At this point, the neutrons dissolve into quarks and vast amounts of energy are unlocked, causing the aforementioned super-luminous events. The researchers — Denis Leahy and Rachid Ouyed — are quick to point out that competing explanations of these supernovae cannot be ruled out without further observations of these exotic phenomena.
All of which is highly speculative but a stunning possibility just the same. What’s happening to the Milky Way itself is also a bit of a surprise, for at the same AAS meeting, a team led by Robert Benjamin (University of Wisconsin, Whitewater) used new imagery from the Spitzer Space Telescope to re-examine the galaxy’s structure. The result: There appear to be not four but just two major arms to our galaxy, a possibility neatly captured in the image below. Benjamin notes how tricky studying a galaxy from within can be:
“For years, people created maps of the whole galaxy based on studying just one section of it, or using only one method. Unfortunately, when the models from various groups were compared, they didn’t always agree. It’s a bit like studying an elephant blind-folded.”
Image (click to enlarge): Like early explorers mapping the continents of our globe, astronomers are busy charting the spiral structure of our galaxy, the Milky Way. Using infrared images from NASA’s Spitzer Space Telescope, scientists have discovered that the Milky Way’s elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms. Credit: NASA/JPL-Caltech.
Earlier radio surveys and the infrared surveys that followed them had revised the initial model of a spiral with four major star-forming arms, but Benjamin’s software has gone to work counting stars and measuring stellar densities, employing a vast Spitzer mosaic that takes in some 110 million stars. The Milky Way now appears to be like other galaxies we have observed with a central bar of stars (the latter a discovery made in the 1990s). The two major arms are now seen to be the Scutum-Centaurus and Perseus arms (although the Perseus arm is not visible in the field of view covered by the new Spitzer images).
The Sagittarius and Norma arms are now considered to be minor, with the Perseus and Scutum-Centaurus arms showing the greatest density of both young, bright stars and older red giants. Bear in mind that our own small star is currently found near the partial arm known as the Orion Spur, located between the Sagittarius and Perseus arms. But as this JPL news release points out, stars tend to move in and out of arms as they orbit the galaxy’s center. In fact, our Sun would have made sixteen circuits of the Milky Way since its formation four billion years ago.
I’m a little puzzled by this, since my understanding was that galactic arms were defined by their concentration of gas and dust and star-formation regions, rather than by their number of stars. I recall being informed that the star density within spiral arms is only about 10% greater than between them.
But I guess most of that increase would consist of the biggest, brightest blue supergiants, the kind that are short-lived and don’t stray too far from their birthplaces in the arms before dying. So maybe the arms that have the most of those would be much brighter and somewhat more massive, even if their numerical density isn’t that much greater? Is that it?
Anyway, I’m wondering about the astrobiological implications of this. The “Rare Earth” people often point out that passing through spiral arms is dangerous for life due to the radiation and such. I don’t entirely buy that, since we’re in a spiral arm and a major star-formation wave passed through our region within the past 10 million years, probably promoting our own evolution by driving climate change. The astrophysicists who claim that catastrophe inhibits evolution have it backwards; in fact, the paleontological record suggests that catastrophe promotes faster evolution by opening new niches and encouraging innovation. But I could accept that what might be an overstated risk for a small arm like ours could be more legitimate for one of the major arms: whereas a moderate rate of catastrophe promotes evolution, too high a rate would probably be a detriment.
So if the galaxy only has two major arms rather than four, does that mean that the danger to inhabited planets would be less, and the probability of higher life arising would be greater?
Catastrophe doesn’t promote faster evolution if the catastrophe is big enough to sterilize the planet. One explanation for Rare Earth would be that wipeout catastrophes are actually common, and Earth is a lucky planet that has avoided near supernovae and successfully snowballing or greenhousing itself to death.
I’m skeptical that it promotes faster evolution at all, except in the post-catastrophe period when the survivors are radiating into empty niches, and they’re kind of re-inventing the wheel, e.g. evolving new large herbivores and predators to replace the old set of large herbivores and predators. The catastrophe might give you something you wouldn’t have gotten otherwise, but then so might not having a catastrophe, and letting large species evolve without such disturbance.
Hi Paul and Christopher L. Bennett;
The idea of a quark star is fascinating. The average density of the quark star would be (16/12) EXP 3 times greater than that for the neutron star.
The transition from neutron star density material to that of a quark star seems to liberate 100 times more energy than a typical supernova. Thus. for bulk matter, the dissolution of neutrons into quarks and the resulting release of energy might be roughly 100 times that of nuclear energy release within ordinary nuclear reactions. If we could determine how to duplicate this energy release for macroscopic quantities of matter of rest mass on the order of that for fuel supplies for manned interstellar spacecraft, we might have a fuel supply that approaches in mass specific energy density that of matter/antimatter fuel.
A proposed similar idea that has occasionally circulated is that of a so-called quark bomb which would have a yield 1,200 times greater than that possible for an atomic bomb of the same mass. The point is that such quark bombs, if they could be made in low yield, stable for storage versions, they might be utilized for an Orion style space craft on steroids. A quark bomb pellet runway would allow potentially even higher gamma factors than a spacecraft that carried its quark bombs on board for propulsion.
Perhaps, if there is a sub-structure to quarks, even denser stars exist, perhaps with a mass of about 1.5 solar masses and diameter of about 9 or 10 miles.
We will have to see what the folks at the LHC in CERN come up with. If they are able to produce stable strangelets, which are theoretically stable forms of matter composed of roughly equal numbers of up, down, and strange quarks, perhaps they can produce a top and/or bottom quark analogue. Since the linear width of the apparent cross section of a fundamental particle is inversely related to its mass, top and/or bottom matter might be several times denser to several orders of magnitude denser than any possible ordinary macroscopic mass quantities of artificially manufactured strangelet material.
Thanks;
Jim
Hi Jim
Preons are a possible sub-stratum for quarks, but preon star models are typically a lot smaller. I think one problem is that compact stars are getting very close to becoming black-holes. A two solar mass blackhole is 12 km across, and its photon sphere is just 18 km across – very close to proposed quark star sizes.
Hi Adam;
Thanks for the info on preons. Perhaps preons, if they exist, could be fashioned into continuous macroscopic lumps of mass in a manner analogous to quark nuggets.
Since the radius of a black hole is proportional to its mass, and preon matter could be several orders of magnitude denser than quarkonium, perhaps Earth massed preon nuggets could be as small as 10 cm to 100 cm in diameter. Such matter might be an awesome way to store mattergy in incredibly dense form wherein the density would still be below the threshold for the formation of a black hole. All this assumes that preon matter would be stable against decay and that the preons would not bind themselves in a manner such that quark matter would form via the arrangement of the preons into the less dense form of matter of quarkonium.
Either way, the concept of preons is fascinating. It will be interesting to see what the folks at the LHC cook up.
Thanks;
Jim
Damien R. S. wrote:
“One explanation for Rare Earth would be that wipeout catastrophes are actually common, and Earth is a lucky planet that has avoided near supernovae and successfully snowballing or greenhousing itself to death.”
Every time humans have ever formulated a cosmological or evolutionary theory that postulated that we or our world is somehow unique or special or central in the cosmos, it’s been wrong. I’m therefore skeptical of any idea that requires Earth to be a statistical outlier.
As for the link between catastrophes and evolution, the biggest burst of new evolution in Earth’s history, the Cambrian Explosion, came in the wake of a string of periods of “Snowball Earth” glaciation. So it’s not true to say that Earth avoided “snowballing.” We were repeatedly “snowballed,” and in the wake of it came a great burst of biodiversity. Life is not as fragile as the Rare Earthers think.
For that matter, there are species of microbes right here on Earth that can survive intense radiation, heat, pressure, even vacuum. So I’m not convinced that complex life would be impossible in zones of intense irradiation. Rather, I think that most life on Earth hasn’t evolved radiation resistance simply because it hasn’t needed to, whereas on a world that was more heavily irradiated, life would evolve such resistance. After all, evolution is simply adaptation to the demands of one’s environment. A harsher environment wouldn’t make life impossible, it would just force it to become hardier and more adaptable in ways that most terrestrial life hasn’t needed to.
@Christopher L. Bennett: couldn’t agree more!
Although, of course, every grain of sand is, strictly speaking, unique, this “unique or special or central in the cosmos” way of thinking is a remnant of deterministic and dogmatic geocentrism and anthopocentrism. And circular reasoning too: everything has to be exactly the way we know it, because this is the way we know it.
This ignores the cosmological principle (the laws of physics apply everywhere, similar matter is present throughout the universe).
Besides it ignores the fact that our own planet and sun have not exactly been constant throughout their histories. E.g. right now we are approaching the inner edge of our habitable zone (or rather: the habitable zone of our sun is slowly moving outward).
I have a question about that galactic map: how accurate is it in detail? Do the variously colored blobs and points of light represent actual plotted positions of HII regions, dust clouds, OB associations, etc., or are they just placed at random for the visual impression? The formations close to the Sun do resemble the placements of major Orion Spur structures I’ve seen in other maps, but not enough to be certain. I’m wondering if this same Spitzer data can be used to create more detailed maps of specific regions of the galaxy, especially the Orion Spur and neighboring arms. As an SF writer, I’d find that an invaluable resource. (I’m thinking of something like the old Guide to the Galaxy by Henbest and Couper, a great book which is long overdue for an update.)
Stable quarks of the 4th family?
Authors: K. Belotsky, M. Khlopov, K. Shibaev
(Submitted on 5 Jun 2008)
Abstract: Existence of metastable quarks of new generation can be embedded into phenomenology of heterotic string together with new long range interaction, which only this new generation possesses. We discuss primordial quark production in the early Universe, their successive cosmological evolution and astrophysical effects, as well as possible production in present or future accelerators.
In case of a charge symmetry of 4th generation quarks in Universe, they can be stored in neutral mesons, doubly positively charged baryons, while all the doubly negatively charged “baryons” are combined with He-4 into neutral nucleus-size atom-like states. The existence of all these anomalous stable particles may escape present experimental limits, being close to present and future experimental test. Due to the nuclear binding with He-4 primordial lightest baryons of the 4th generation with charge +1 can also escape the experimental upper limits on anomalous isotopes of hydrogen, being compatible with upper limits on anomalous lithium.
While 4th quark hadrons are rare, their presence may be nearly detectable in cosmic rays, muon and neutrino fluxes and cosmic electromagnetic spectra. In case of charge asymmetry, a nontrivial solution for the problem of dark matter (DM) can be provided by excessive (meta)stable anti-up quarks of 4th generation, bound with He-4 in specific nuclear-interacting form of dark matter.
Such candidate to DM is surprisingly close to Warm Dark Matter by its role in large scale structure formation. It catalyzes primordial heavy element production in Big Bang Nucleosynthesis and new types of nuclear transformations around us.
Comments: 28 pages, 3 figures; Invited contribution to the book “The Physics of Quarks: New Research”, Nova Science Publishers, 2008
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0806.1067v1 [astro-ph]
Submission history
From: Konstantin Belotsky M. [view email]
[v1] Thu, 5 Jun 2008 22:23:34 GMT (96kb)
http://arxiv.org/abs/0806.1067
Hi ljk;
Very interesting paper on stable fourth generation quarks! If we assume the possibility of 4th generation quarks, perhaps still other generations of stable or meta-stable quarks may exist.
Perhaps the same could be said for additional generations of leptons. Additional heavy electrons and associated neutrinos would be awesome.
With all of the currently known, predicted, and yet more speculative conjectured particles, we just might end up having a “particle zoo” like we had during the 1960s. A further substructure to some or all of the above particles may yet exist. It will be interesting to see what the folks at the LHC come up with.
Thanks;
Jim
Astrophysics of Strange Matter
Authors: Sanjay K. Ghosh
(Submitted on 4 Jul 2008)
Abstract: The QCD phase transition has important consequences in the context of both the early universe as well as compact stars. Such transitions are being studied for high temperature and small chemical potential scenario in the laboratory. There are also plans to study systems with large chemical potential and small temperatures. Here we have reviewed the role of strange quark matter and the phase transition in all the above scenarios.
Comments: Plenary talk at Quark Matter 2008, Jaipur, India
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0807.0684v1 [astro-ph]
Submission history
From: Sanjay K. Ghosh [view email]
[v1] Fri, 4 Jul 2008 07:32:18 GMT (115kb)
http://arxiv.org/abs/0807.0684
Hi Folks;
I have just read an interesting article on the Physics Today website about the very recent discovery of the lowest-energy state of bottomonium, the heaviest family of mesons, which are bound states of pairs of bottom and anti-bottom quarks. This is an interesting development. Perhaps the existence of bottomonium has relavence to the processess occuring in neutron stars and quark stars. The ever growing number of known composite particles points to the richness of the strong nuclear force and the complexity of QCD.
I have often wondered if, given all of the decay sequences known to mankind for the entire set of known fundamental particles and known composite particles, whether or not there is anyway that such sub-sequences can be combined or any of the various short lived particles, composite and/or simple, be colocated in spacetime in such a manner that useful exothermic reactions can be facilitated, perhaps for energy production, novel spatial-temporal effects, or yet to be discovered particles produced without the need for extremely high particle energies such as the 14 TeV of the LHC at CERN.
Any such reactions not involving traditional and known nuclear fusion or nuclear fission, nor bulk antimatter production, might offer humanity a new window on power generation.
There are now so many known decay sequences and there are becoming so many known composite particles that the mind becomes boggled by the complexity of the thermodynamic degrees of freedom that exist in particle physics interactions.
In a way, I am pleased by all of this richness and complexity and feel like a kid in a candy shop every time a new particle or element/isotope is discovered. I get the feeling that there will always be new ground for particle physics to cover.
With the growing complexity of the known family of baryonic, mesonic, and other forms of matter composed at least in part of quarks and gluons, there remains more degrees of freedom in which baryonic matter might exist within our universe such as the so-called missing baryonic matter.
Thanks;
Jim
ASTRONOMERS DESCRIBE THE BAR SCENE AT THE BEGINNING OF THE UNIVERSE
(ASTRONOMY)
Bars abound in spiral galaxies today, but this was not always the
case. A group of 16 astronomers, led by Kartik Sheth of NASA’s
Spitzer Science Center at Caltech, has found that bars tripled in
number over the past seven billion years, indicating that spiral
galaxies evolve in shape.
Details: http://mr.caltech.edu/media/Press_Releases/PR13170.html
The Behavior of Matter under Extreme Conditions
Authors: F. Paerels (1), M. Mendez (2), M. Agueros (1), M. Baring (3), D.Barret (4), S. Bhattacharyya (5), E. Cackett (6), J. Cottam (7), M. Diaz Trigo (8), D. Fox (9), M. Garcia (10), E. Gotthelf (1), W. Hermsen (11), W. Ho (12), K. Hurley (13), P. Jonker (11), A. Juett (7), P. Kaaret (14), O. Kargaltsev (9), J. Lattimer (15), G. Matt (16), F. Ozel (17), G. Pavlov (9), R. Rutledge (18), R. Smith (10), L. Stella (19), T. Strohmayer (7), H. Tananbaum (10), P. Uttley (12), M. van Kerkwijk (20), M. Weisskopf (21), S. Zane (22) ((1) Columbia University, (2) University of Groningen, (3) Rice University, (4) CESR Toulouse, (5) Tata Institute of Fundamental Research, Mumbai, (6) University of Michigan, (7) NASA Goddard Space Flight Center, (8) European Space Astronomy Centre, ESA, (9) Penn State University, (10) Harvard-Smithsonian Center for Astrophysics, (11) SRON Netherlands Institute for Space Research, (12) University of Southampton, (13) University of California at Berkeley, (14) University of Iowa, (15) SUNY Stony Brook, (16) Universita degli Studi Roma Tre, (17) University of Arizona, (18) McGill University, (19) Osservatorio Astronomico di Roma, (20) University of Toronto, (21) NASA Marshall Space Flight Center, (22) Mullard Space Science Laboratory)
(Submitted on 2 Apr 2009)
Abstract: The cores of neutron stars harbor the highest matter densities known to occur in nature, up to several times the densities in atomic nuclei. Similarly, magnetic field strengths can exceed the strongest fields generated in terrestrial laboratories by ten orders of magnitude.
Hyperon-dominated matter, deconfined quark matter, superfluidity, even superconductivity are predicted in neutron stars. Similarly, quantum electrodynamics predicts that in strong magnetic fields the vacuum becomes birefringent.
The properties of matter under such conditions is governed by Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED), and the close study of the properties of neutron stars offers the unique opportunity to test and explore the richness of QCD and QED in a regime that is utterly beyond the reach of terrestrial experiments. Experimentally, this is almost virgin territory.
Comments: 8 pages, 4 figures. White paper submitted to the Astro2010 Decadal survey of Astronomy and Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:0904.0435v1 [astro-ph.HE]
Submission history
From: Frits Paerels [view email]
[v1] Thu, 2 Apr 2009 18:00:17 GMT (618kb)
http://arxiv.org/abs/0904.0435
Can stellar mass black holes be quark stars?
Authors: Z. Kovacs, K. S. Cheng, T. Harko
(Submitted on 19 Aug 2009)
Abstract: We investigate the possibility that stellar mass black holes, with masses in the range of $3.8M_{\odot}$ and $6M_{\odot}$, respectively, could be in fact quark stars in the Color-Flavor-Locked (CFL) phase. Depending on the value of the gap parameter, rapidly rotating CFL quark stars can achieve much higher masses than standard neutron stars, thus making them possible stellar mass black hole candidates.
Moreover, quark stars have a very low luminosity and a completely absorbing surface – the infalling matter on the surface of the quark star is converted into quark matter.
A possibility of distinguishing CFL quark stars from stellar mass black holes could be through the study of thin accretion disks around rapidly rotating quark stars and Kerr type black holes, respectively. Furthermore, we show that the radiation properties of accretion disks around black holes and CFL quark stars are also very similar.
However, strange stars exhibit a low luminosity, but high temperature bremsstrahlung spectrum, which, in combination with the emission properties of the accretion disk, may be the key signature to differentiate massive strange stars from black hole.
Comments: 27 pages, 5 figures, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
Cite as: arXiv:0908.2672v1 [astro-ph.HE]
Submission history
From: Tiberiu Harko [view email]
[v1] Wed, 19 Aug 2009 03:26:00 GMT (600kb)
http://arxiv.org/abs/0908.2672