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Figure 2. i

Gaiaxy Spectra, Astronomers take the Fight from a galaxy and spread it into a rainbow Then they construct a graph as shown at the cop arn) the bottom,The gaJaxy spectra at the cop of this rainbow have absorption lines, those near the bottom have emission lines that come from gas clouds whose atoms are excited by the ultraviolet light from stars. Courtesy of Barbara Carter. Harvard-Smithsonian Center for Astrophysics

Figure 2.2

Th« Globular Cluster NGC 6093, A globular duster contains many thousands of stars that formed at the same time, early in our galaxy's history. By measuring the properties of stars that have recently become red giants (visible in this color im^ge as reddish, bright stars in the duster) the age of the duster car be pnferned.The oldest ¿lobular clusters have ages of 12 ± I billion years Courtesy of NASA and the Hubble Heritage Team {STSd/AURA).

Figure 1.3

Planetary nebula NGC 6751. After about a billion years as a red giant,a scar like the sun vvill puff off its outer envelope while the core shrinks to become a white dwarf, A planetary nebula is the beautiful transition from a gaseous star with nuclear fusion to a solid star with no energy source Courtesy. NASA and the Hubble Heritage Team (STSd/AURA)

Figure 1.3

Planetary nebula NGC 6751. After about a billion years as a red giant,a scar like the sun vvill puff off its outer envelope while the core shrinks to become a white dwarf, A planetary nebula is the beautiful transition from a gaseous star with nuclear fusion to a solid star with no energy source Courtesy. NASA and the Hubble Heritage Team (STSd/AURA)

Figure 2.4

Supernova l994D.This type la supernova (bright spot ac lower left) is in a galaxy at a distance of about 50 million light years in the Virgo duster of galaxies For a month, the light from a single exploding white dwarf is as brigjit as 4 billion stars ike the sun Courtesy of R Challis, Harvard-Smithsonian Center for Astrophysio/STSd/NASA.

Figure 3.2

Supernova 1987A. Space telescope irnj^e of the site of SN 1987A. seen 10 years later.The exploded star itself is the dot in the center of the bright inner ring, heated by the decay of radioactive elements produced in the explosion The inner ring is gas lost from the pre-supemova star, excited and still glowing from the light of the outburstTlils ring was the source of the emission seen by the International Ultraviolet Explorer satellite in 1987-88. Courtesy of R Challis and the SINS collaboration. Harvard-Smithsonian Center for Astnophysics/NASA/STSd.

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