Exploded Star Reveals Strange New Matter

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Exploded Star Reveals Strange New Matter


Pulsar Astronomy

http://www.space.com/10931
-
neutron
-
star
-
bizarre
-
superfluid
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core.html


Page
1


SPACE.com Staff

Date: 23 February 2011 Time: 05:46 PM ET


The ultradense core of an exploded star contains a bizarre form of superconducting matter called
a superfluid, new studies suggest.

Two teams of researchers using NASA's
Chandra X
-
ray Observatory

detected a rapid dip in the
temperature of Cassiopeia A (Cas A), which is a neutron star


the remnant left behind when a
massive star ends its life in a supern
ova explosion. The huge temperature drop is solid evidence
for the presence of a strange state of matter in the core of Cas A, researchers said.

"The rapid cooling in Cas A’s neutron star, seen with Chandra, is the first direct evidence that the
cores of t
hese
neutron stars

are, in fact, made of superfluid and superconducting material," Peter
Shternin of the Ioffe Institute in St. Petersburg, Russia, said in a statement
. He is leader of one of
the teams.

Superfluids made of charged particles are also superconductors, which allow electric current to
flow with no resistance.

A neutron star cools off

Cas A is the remnant of a
huge star that exploded

about 330 years ago. The neutron star is about
11,000 light
-
years away, in the constellation Cassiopeia.

Researchers in both of the new studies

found that it has cooled by about 4 percent over a 10
-
year
period.

"This drop in temperature, although it sounds small, was really dramatic and surprising to see,"
said Dany Page of the National Autonomous University in Mexico, leader of the other researc
h
team. "This means that something unusual is happening within this neutron star."

Neutron stars are some of the densest known objects. One teaspoon of neutron star stuff has a
mass of 6 billion tons.

The pressure in the star’s core is so immense that mos
t of the electrons there merge with protons,
producing neutrons, researchers said.

Physicists have developed detailed models to predict how matter should behave at such high
densities, including the possibility that superfluids may form.

Superfluidity is a

friction
-
free state of matter, and superfluids created in labs here on Earth
exhibit remarkable properties. It can climb upward, for example, and escape airtight containers,
researchers said.

Exploded Star Reveals Strange New Matter


Pulsar Astronomy

http://www.space.com/10931
-
neutron
-
star
-
bizarre
-
superfluid
-
core.html


Page
2


Superfluids in dead star's core

In their studies, both research

groups found evidence that Cas A's rapid cooling is due to the
formation of a neutron superfluid in the neutron star's core, and that this happened within the last
100 years or so.

The details of Shternin's study will appear in the journal Monthly Notices

of the Royal
Astronomical Society Letters. The reseach by Page and his team will appear in the journal
Physical Review Letters.

Cas A's dropping temperatures are consistent with theory, which predicts that a neutron star
should undergo a distinct cool
-
dow
n during the transition to the superfluid state, researchers said.

During this time, nearly massless, weakly interacting
particles called neutrinos

form i
n huge
numbers and then escape, taking energy with them. The cooling is expected to continue for
another few decades before slowing down, researchers said.

On Earth, the appearance of superfluidity in materials occurs at extremely low temperatures, near
ab
solute zero, about minus 273 degrees Celsius (minus 459.6 degrees Fahrenheit). But in neutron
stars, it can take place at temperatures near 1 billion degrees F because interactions of particles
occur via the strong nuclear force


the force that binds quar
ks together to make protons and
neutrons, and protons and neutrons together to form atomic nuclei.

Until now, there was a very large uncertainty in estimates of this critical temperature. But the
new research pins it down to between 900 million and 1.8 bil
lion degrees F (500 million to 1
billion degrees C), researchers said.


"It turns out that Cas A may be a gift from the universe because we would have to catch a very
young neutron star at just the right point in time," said Page’s co
-
author Madappa Prakas
h, from
Ohio University.

"Sometimes a little good fortune can go a long way in science."

Helping shed light on neutron stars


The researchers said their findings suggest that the Cas A supernova remnant can serve as a good
test bed for studying how ultrade
nse matter behaves at the atomic level.

These results are also important for understanding the diversity among neutron stars, including
pulsation, magnetar outbursts and the evolution of powerful neutron star magnetic fields,
researchers said. The new stud
ies could also help scientists better understand small, sudden
changes in highly magnetized, rotating neutron stars known as pulsars.

Past studies of the pulsar changes, known as glitches, have yielded evidence of superfluid
neutrons in the crust of a neut
ron star, where densities are lower than in the core.

Exploded Star Reveals Strange New Matter


Pulsar Astronomy

http://www.space.com/10931
-
neutron
-
star
-
bizarre
-
superfluid
-
core.html


Page
3


The new research on Cas A, however, provides the first direct evidence for superfluid neutrons
and protons in the core of a neutron star, researchers said.

Questions:

1.

Describe the material Peter Shtemin

believes could be in the inner core of a neutron star.






2.

What evidence suggests this?





3.

The author states Superfluids made of charged particles are also superconductors. What
does this indicate about the ability of the electrons contained within the

neutron star to
flow?
(This will be very important when we discuss the magnetic fields of pulsars)







4.

State the unique behaviors of Superfluids on Earth.





5.

What did both research groups conclude was the reason CasA was cooling down so
quickly?



6.

The
critical temperature for the matter in neutron star to become superfluids has been
narrowed down to a temperature range. What is this range?




7.

What additional evidence has been observed to support neutron and proton superfluidity
in neutron stars?



Exploded Star Reveals Strange New Matter


Pulsar Astronomy

http://www.space.com/10931
-
neutron
-
star
-
bizarre
-
superfluid
-
core.html


Page
4


Use

this page for notes or a draft model of your neutron star.