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The Sun(diam 1 392 000 km or 109 Earth diameters,
distance 150 000 000 km or 1 astronomical unit - 1 AU)
Eclipse of the Sun by the Moon as seen from Antarctica(both subtend almost exactly the same angle
of half a degree at the Earth)
Pluto and Charon - double planet(0.18 and 0.09 Earth diam
1.54 Earth diam apartat 29.7 to 49.4 AU from Sun)
Comet Hale-Bopp in March 1997
A comet tail can be over 1 AU long,but its nucleus measures only a few km across
Hubble Deep Field showing galaxies over 10 billion light years away (looking back in time to near the
beginning of the universe)
The constellation of Orionand the Milky Way
(The bright stars we see here are no more than a few hundred light years away)
Betelgeuse
Rigel
OrionNebula
New stars forming in pillars of molecular hydrogen and dust that are light years in length (in Eagle Nebula)
Life Cyclesof Stars in Outline
The Life Cycles of Stars in Outline
Cloud of dust and gas
Main Sequence star
Low mass star High mass star Very high mass star< 4 solar masses 4 to 25(?) solar masses > 25 (?) solar masses
Red giant Red supergiant Red supergiant
White dwarf and
planetary nebula
Neutron star and
supernova remnant
Black hole and
supernova remnant
< 1.4 solar masses > 3 to 5 (?) solar masses
Contracts under gravity andheats up until eventually
thermonuclear reactions start
Expands Expands
Explodes as asupernova
Explodes as asupernova
Loses outer layers
Expands
(Most of a star's life)
Helix Planetary Nebula (1.5 light years across)
White dwarf star(remains of core of star and about size of the Earth)
Planetary nebula(remains of outer layers of star)
Cat’s Eye Planetary Nebula and white dwarf(A solar mass white dwarf would be only as big as the Earth)
Crab Nebula a supernova remnant - remains of a star that exploded
10 light years across
neutron star about 10 kmacross is at centre (not visible)
A black hole a few million times the mass of the Sun lurks at the centre of our galaxy and causes nearby stars to orbit very
rapidly
Gravitational lensing by a galaxy cluster 2 billion light years away bends light from a galaxy so far away that its light has been travelling for 95% of the age of the Universe