•
Stellar Parallax(heliocentric)
Stellar parallax is measure of
distance
• The diameter of earth’s orbit
around sun is basic line for such
measurement
• Trigonometric parallax is defined as
the angle p (in seconds)subtended
at the star by the mean radius a of
earth’s orbit around the sun
• A nearby star is photographed from
the position E and after six months
by the position E’
• From this the angle subtended by
the diametr EE’ is measured and it
half gives th annular parallax of the
star
, Astronomical unit of distance
prad= a/d d-distance of the star
1 rad= 206265” (1 rad= π /180 degree=
π*60*60/180) p”/206265 = a/d
d= 206265 a/p”
d = 1/p”
2026265 a is unit of distance is called 1 parsec(1pc)
Parsec is distance at which the radius of the earth’s
orbit(1 au) subtend angle
of one second of arc
1 parsec = 206265 au = 3.26 light year = 3*1016 m
1 au = 1.49 *1014 m
1 ly = 9.46 *1015 m
pc>ly>au
Stellar Parallax(heliocentric)
Stellar parallax is measure of
distance
• The diameter of earth’s orbit
around sun is basic line for such
measurement
• Trigonometric parallax is defined as
the angle p (in seconds)subtended
at the star by the mean radius a of
earth’s orbit around the sun
• A nearby star is photographed from
the position E and after six months
by the position E’
• From this the angle subtended by
the diametr EE’ is measured and it
half gives th annular parallax of the
star
, Astronomical unit of distance
prad= a/d d-distance of the star
1 rad= 206265” (1 rad= π /180 degree=
π*60*60/180) p”/206265 = a/d
d= 206265 a/p”
d = 1/p”
2026265 a is unit of distance is called 1 parsec(1pc)
Parsec is distance at which the radius of the earth’s
orbit(1 au) subtend angle
of one second of arc
1 parsec = 206265 au = 3.26 light year = 3*1016 m
1 au = 1.49 *1014 m
1 ly = 9.46 *1015 m
pc>ly>au
