Transcript Binary Stars - Mid-Pacific Institute

Binary Stars
Sin’Kira Khan
What is a binary star?
 a star system made up of usually two stars
that orbit around one center of mass, where
the mass is most concentrated
 A binary star is not to be confused with two
stars that appear close together to the
naked eye from Earth, but in reality are very
far apart
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 Planet's revolve around stars because
of gravity
 gravity is not restricted to between
large and small bodies, stars can
revolve around stars as well
 Binary stars obey Kepler's Laws of
Planetary Motion
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Kepler’s Law
 1st law (law of elliptic orbits): Each
star or planet moves in an elliptical
orbit with the center of mass at one
focus
Several Categories

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eclipsing binaries
visual binaries
spectroscopic binaries
astrometric binaries
Eclipsing binaries
 Eclipsing binary stars are those whose
orbits form a horizontal line from the
point of observation
 what the viewer sees is a double
eclipse along a single plane
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Algol
 The most famous eclipsing binary star
is visible to the naked eye and has a
rich mythology associated with it
demonstration
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Visual binaries
 A visual binary system is a system in
which two separate stars are visible
through a telescope that has an
appropriate resolving power
 These can be difficult to detect if one
of the stars’ brightness is much greater
 in effect blotting out the second star
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Alpha Centauri A & B
 They orbit each other with a period of
80 years
Spectroscopic binaries
 the stars are very close and orbiting very
quickly
 These systems are determined by the
presence of spectral lines: lines of color that
are anomalies in an otherwise continuous
spectrum and are one of the only ways of
determining whether a second star is present
 It is possible for a binary star system to be
both a visual and a spectroscopic binary if
the stars are far enough apart and the
telescope being used is of a high enough
resolution
Mizar or ζ Ursae Majoris in
1889
 Mizar was already known as a visual
binary but spectroscopic analysis of the
brighter of the two stars, Mizar A,
showed that it was in fact a
spectroscopic binary
Astrometric binaries
 systems in which only one star can be
observed, and the other’s presence is
inferred by the noticeable wobble of
the first star
 This wobble happens as a result of the
smaller star’s slight gravitational
influence on the larger star
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Sirius A & B
 n 1844 Friedrich Bessell pointed out
that it had a wobble in its proper
motion
Finding of mass
 Astrophysicists find binary systems to be
quite useful in determining the mass of the
individual stars involved
 When two objects orbit one another, their
mass can be calculated very precisely by
using Newton’s calculations for gravity
 The data collected from binary stars allows
astrophysicists to extrapolate the relative
mass of similar single stars
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Work Cited
 "What Is a Binary Star?" Universe Today. Web. 07 Feb. 2011.
<http://www.universetoday.com/24203/what-is-a-binary-star/>.
 "Binary Star." The Worlds of David Darling. Web. 07 Feb.
2011.
<http://www.daviddarling.info/encyclopedia/B/binarystar.html
>.
 Binary Stars." Mac OS X Server. Web. 07 Feb. 2011.
<http://abyss.uoregon.edu/~js/ast222/lectures/lec05.html>.
 "Binary Stars." Cornell Astronomy. Web. 07 Feb. 2011.
<http://www.astro.cornell.edu/academics/courses/astro201/bins
tar.htm>.