Transcript Quark Stars - University of Minnesota

Quark Stars
NASA/Dane Berry
Kyle Dolan
Astronomy 4001
10 December 2007
Outline
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Introduction to Quark Stars (QS)
Significance of QS
Characteristics of QS
Possible examples of QS
Controversy over the existence of QS
Possible future observations
Overview of Neutron Stars
• Core of a massive star that
remains after a supernova
explosion
• Average Density: ~1014
g/cm3
• Rotational frequency may
range up to 1122 Hz (XTE
J1739-285)
• Magnetic field strength can
be ~108-1014 times that of
Earth
• Exotic Physics!
http://science.nasa.gov/
Quark Stars (QS)
• Stellar core composed of
free quarks (strange
matter)
• Would form through
neutron deconfinement
• Neutron Star (NS)
collapses inward after
spinning down, losing
centrifugal force
• Strange matter would be
“softer”, more compressible
than neutrons
• Smaller, denser than a NS
• NS massing from 1.51.8MSun are likely
candidates
http://chandra.harvard.edu
Significance of Quark Stars
• Opportunity to
study strange
matter in nature,
and its unique
behavior
• Quark novae may
explain gamma ray
bursts.
NASA/CXC/M Weiss
Quark Star Characteristics
• Smaller Size, indicating densities significantly
greater than an atomic nucleus
• High Rotational Frequency
– Conservation of angular momentum allows more
compact star to spin faster
• Faster Cooling
– Higher-density matter allows production of more
cooling particles (neutrinos) to carry energy away
RXJ1856.5-3754: Possible QS
• Discovered in 1996
• Diameter of ≤10km.
• Data suggests that
the star is too small
to be made of
normal neutrons,
and could be made
of strange matter.
ESO/VLT
XTE J1739-285:
Record-Setting Pulsar
• Previously known as a normal
neutron star, accreting matter
from a companion star
• Brightness variations of
frequency 1122 Hz observed
• Previous record for rotational
frequency was ~700Hz
• High frequency indicates a more
compact star, possibly made of
strange matter
• May contradict theories of
gravitational waves braking
rotational speeds
NASA/Dana Berry
3C58 – Possible Quark Nova
Remnant
• Pulsar, possibly the remnant
core of SN 1181
• First observed by Chinese and
Japanese Astronomers
• Remnant cools by internal
collisions that release neutrinos
to carry away thermal energy
• Cooling rate is too fast for
matter made only of neutrons
• 3C58 would have to be ~5
times as dense as a normal
neutron star for this cooling rate
to make sense
Chandra X-Ray Observatory
SN 2006gy: Possible Quark Nova
• First Observed: 18
September 2006
• 100 times brighter than
typical Type II novae
• Neutron deconfinement
would blow the outer
layers of the NS away at
near light speed, to
collide with the original
supernova debris.
• Observation of elements
with A>130 in the debris
could confirm 2006gy as
a quark nova
NASA/CXC/M Weiss
Controversy
• Possible contradiction of the QS theory:
– EXO 0748-676, neutron star with possible mass ~2.1MSun,
indicates too much rigidity for strange matter
– Strange matter is too compressible not to collapse in a mass this
large
– Mass could be as low as 1.8 MSun, however, which would still fit
QS models
• More observations of XTE are needed to confirm its
frequency
• 3C58 may be older than the SN 1181 remnant, due to
the lack of variation in its radio emissions
Conclusions
• Quark Stars still theoretical, but evidence
continues to accumulate to support them
• Quark Stars would offer unique opportunities to
study exotic matter
• Helpful Observations for the Future:
– Search for exotic elements in nova remnants
– Precise determinations of NS radii and rotational
frequency
– Close observations of new Supernovae/Quark Novae
Sources
“3C58: Pulsar Gives Insight on Ultra Dense Matter and Magnetic Fields.” chandra.harvard.edu. 30 August 2006.
http://chandra.harvard.edu/photo/2004/3c58/
Blaschke, D.B. et al. “Color superconducting quark matter in compact stars.”. arXiv:0712.0117v1. 2 December 2007
Drake, J. J. et al. “Is RX J185635-375 a Quark Star?” arXiv:astro-ph/0204159v1 9 Apr 2002.
“Quark Stars Could Produce Biggest Bang .” spacedaily.com. 7 June, 2006.
http://www.spacedaily.com/reports/Quark_Stars_Could_Produce_Biggest_Bang.html
Shiga, David. “Fastest spinning star may have exotic heart.” newscientist.com. 20 February 2007.
http://space.newscientist.com/article/dn11221?DCMP=NLC-nletter&nsref=dn11221
Shiga, David. “Massive neutron star rules out exotic matter.” newscientist.com. 28 June 2006.
http://space.newscientist.com/article/dn9428-massive-neutron-star-rules-out-exotic-matter.html
Shiga, David. “Was the brightest supernova the birth of a quark star?” newscientist.com. August 2007.
http://space.newscientist.com/article/dn12514-was-the-brightest-supernova-the-birth-of-a-quark-star.html
“The leader of the celestial ‘Magnificent Seven.’” scientificblogging.com. 9 March 2007.
http://www.scientificblogging.com/news/the_leader_of_the_celestial_magnificent_seven
Xia et al. “Thermal Evolution of Strange Stars.” arXiv:0709.0214v1. 3 September 2007.
Zhang, C.M. et al. “Does Sub-millisecond Pulsar XTE J1739-285 Contain a Low Magnetic Neutron Star or Quark Star?”
arXiv:0708.3566v2. 11 September 2007.
Wilford, John Noble. “Stars Suggest a Quark Twist And a New Kind of Matter.” nytimes.com. 11 April, 2002.
http://query.nytimes.com/gst/fullpage.html?res=9D04E7DB1F3DF932A25757C0A9649C8B63&sec=&spon=&pagewant
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