Chapter Introduction
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The Orion Nebula, 1350 ly away, as imaged by the Hubble Space Telescope. Part of the much larger Orion Molecular Cloud, the Orion Nebula contains more than 3000 stars and many more in the process of forming. The bright central region is the home of the Trapezium, four young, bright stars that cause the surrounding gas and dust to glow. The bright region in the upper left, denoted M43, is glowing due to the radiation from one young, massive star.Exoplanets
WHAT DO YOU THINK?
Have any planets been observed orbiting other stars?
Have any Earthlike planets been discovered orbiting in the habitable zones around other stars?
Have astronomers discovered evidence for life on any planets orbiting other stars?
Answers to these questions appear in the text beside the corresponding numbers in the margins and at the end of the chapter.
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In this chapter you will discover
how astronomers detect exoplanets
that newly forming stars and planetary systems are being discovered every year
that disks of gas and dust, as well as planets, are being observed around a growing number of stars
planets orbiting other stars have sizes ranging at least from 0.2 to 25 Earth radii
information about exoplanet atmospheres is beginning to emerge
that most stars have planets orbiting them
where astronomers are looking for extraterrestrial life