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Scientists discover surprising importance of
'I Love Q' for understanding neutron stars
25 July 2013
Scientists can learn a tremendous amount about
neutron stars and quark stars without
understanding their internal structure in detail,
according to two Montana State University
scientists who published their findings in the July
26 issue of "Science."
"It doesn't matter if the star is made of different
proportions of neutrons, quarks and other particles.
In the end, how much the star can be squeezed will
be a direct function of its moment of inertia," Yagi
said.
Yunes and Yagi used mathematical equations and
computer models to discover that I, Love and Q
"The stars could be the softest or the hardest in
satisfy these universal relations.
their kind, and it wouldn't matter," said Nicolas
Yunes, assistant professor in MSU's Department of
This is the first time that Yunes and Yagi have
Physics.
published their work in "Science," the world's
leading journal of scientific research, global news
The reason – discovered by Yunes and
postdoctoral scholar Kent Yagi—is almost universal and commentary. The weekly publication is read by
relations among three intrinsic properties of these an estimated 1 million readers. It is the academic
highly compressed stars. These relations will allow journal of the American Association for the
Advancement of Science.
astrophysicists to learn about the shape and
degree of deformation of these stars without
"Getting a paper accepted into 'Science' is very
knowing the details of their internal structure.
difficult," Yunes said. "It's a great honor to be
accepted. This encourages us to continue working
These relations – described in Yunes and Yagi's
hard to make new, important discoveries."
paper titled "I Love Q" – are realized among the
moment of inertia ("I"), the "Love number" and the
Neutron stars and quark stars are extremely
quadrupole moment ("Q").
compact. They contain an enormous amount of
mass in a tiny radius. Because of that, they are so
The first quantity describes how fast a star can
rotate. The larger the number, the slower the spin dense that they exert an insanely strong
gravitational pull, Yunes said.
rate.
"Think of twirling ice skaters," Yagi said. "If they
bring their arms close to their bodies, the skaters'
moment of inertia decreases, and so they spin
faster."
"Just imagine a ball the size of the sun being
squeezed until it's the size of Bozeman," he said.
"All the gravity of the sun, but amplified by factors
of thousands."
The Love number relates to the deformability of a
star when squished. The larger the number, the
more deformed the star is. The third quantity, "Q,"
refers to the changing shape of a star.
Astrophysicists believe that these stars produce
waves that vibrate through the universe, as the
stars spiral into each other and collide. The
scientists predict that they will be able to detect
these "gravitational waves" by the end of this
decade. If they are successful, they will have a
whole new way of understanding the universe.
A measurement of any one of these three
quantities would allow astrophysicist to infer the
other two to amazing precision without actually
measuring them, according to the MSU
researchers.
"To make a simple analogy, these waves are like
the soundtrack to the universe, and their detection
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will be like transitioning from mute pictures to
modern cinema," Yunes has said in the past.
Yunes and Yagi believe that these I-Love-Q
relations they have found will aid in the gravitational
wave effort.
"For instance, this universal relation could be used
to test Einstein's Theory of General Relativity
without contamination due to our ignorance of their
internal structure," Yunes said. "You could also use
these relations to tell whether what you have
observed is a neutron star or a strange quark star."
Not understanding the internal structure of neutron
stars has presented a major challenge to certain
astrophysical studies, but the "I Love Q relations
show that you can proceed without that
knowledge," Yunes said.
More information: "I-Love-Q: Unexpected
Universal Relations for Neutron Stars and Quark
Stars" Science vol 341 26 July 2013
Provided by Montana State University
APA citation: Scientists discover surprising importance of 'I Love Q' for understanding neutron stars
(2013, July 25) retrieved 15 June 2017 from https://phys.org/news/2013-07-scientists-importanceneutron-stars.html
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