Science lifts the curtain on a tiny piece of night and finds ten thousand galaxies hidden there. How many stories, how many ways of being in the universe are contained therein? All residing in what, to us, had been just a little patch of empty sky.
Figure 1. Eagle Nebula
A stellar nursery located about 6,500 light-years away from us. Through a window in a dark enveloping shell of interstellar dust, we see a cluster of brilliant newborn stars. Their intense blue light has sculpted filaments and walls of gas and dust, clearing and illuminating a cavity in a cloud about 20 light-years across.
Figure 2. Crab Nebula
This is the remnant of the same exploded star, or supernova, that Chinese and Native American Anasazi astronomers observed in the constellation Taurus in A.D. 1054. They recorded the sudden appearance of a brilliant new star that then slowly faded from view. The filaments are the unraveling debris of the star, enriched in heavy elements produced by the explosion.
Figure 3. Sun and Planets
Here in their order and relative sizes are the Sun (at left), the four terrestrial planets (Mercury, Venus, Earth, Mars), the four gas giant planets (Jupiter, Saturn, Uranus, Neptune), and Pluto (far right).
Figure 4. Wright Solar System and Sirius
The top shows to scale the Sun (left) and the orbit of Mercury (right). The middle shows the entire solar system with the orbit of Saturn (S) and several elliptical comet orbits (left) and the system of the bright star Sirius (right). The bottom shows from left to right the orbits of Saturn, Jupiter, Mars, Earth, Venus, Mercury, and the Sun.
Figure 5. Solar System Scales
Upper left The orbits of the inner planets Mercury, Venus, Earth, and Mars, the asteroid belt, and the orbit of Jupiter.
Upper right: The scale increases tenfold to encompass the larger orbits of all the gas giant planets Jupiter, Saturn, Uranus, and Neptune, and the elliptical orbit of Pluto.
Lower right: A further scale change compresses the orbits of all the planets into the box at one end of the highly elliptical orbit of a comet.
Lower left: The scale increases again so that the cometary orbit is now in the tiny box at the center and we see the inner portion of the Oort Cloud of comets.
Figure 6. Oort Cloud
Schematic view shows the vast spherical cloud of perhaps a trillion comets, weakly bound by the gravity of the Sun (center). It was named after the Dutch astronomer Jan Oort, who correctly hypothesized its existence in 1950.
Figure 7. Wright: Other Systems
Wright imagined that our own solar system was but one of a countless number of similar systems in the Milky Way, each perhaps containing a star surrounded by its own retinue of planets and comets.
Figure 8. The Pleiades Star Cluster
The bright stars in this cluster illuminate the faint remnants of the interstellar cloud from which they formed. This star cluster, a naked eye object in the constellation Taurus, is about 15 light-years across.
Figure 9. Orion Nebula
A vast cloud of glowing interstellar gas and opaque dust, which is giving birth to dozens of new stars. The nebula is about 40 light-years across and 1,500 light-years away. If you look up at the constellation Orion on a winter night, this stellar nursery appears as the hazy central "star" in his sword.
Figure 10. Eskimo Nebula
Ten thousand years ago this halo of gas and dust was part of the central star. The aging star then expelled its outer layers into space in successive bursts, forming what astronomers call a planetary nebula. All ordinary stars like the Sun will eventually meet a similar fate.
Figure 11. Veil Nebula
These glowing filaments trace a portion of the expanding remnants of a supernova, a star that exploded about five thousand years ago in the constellation Cygnus.
Figure 12. Sagittarius Star Cloud
A relatively crowded region of old stars in the direction of the center of the Milky Way Galaxy.
Figure 13. Andromeda Galaxy, M31
This large spiral galaxy is only about 2 million light-years away, making it the closest one to our own Milky Way. The flattened rotating disk of stars and clouds of gas and dust is about 200,000 light-years across and contains several hundred billion solar systems.
Figure 14. Hercules Cluster
Most of the objects in this image are entire galaxies, like our own Milky Way, each containing many billions of stars. Many of the galaxies of the Hercules Cluster are interacting, with some of them actually colliding and merging. This rich cluster is about 650 million light-years away.
Figure 15. Saturn Wide Shot
A stunning array of orbiting rings encircles the gas giant planet Saturn, which casts its shadow on them. The Cassini Division is the most prominent of many gaps in the ring system. It is named after the seventeenth-century Italian-French astronomer Giovanni Domenico Cassini who made many important discoveries about our solar system. His namesake spacecraft, the one that took this picture, has now done the same.
Figure 16. Close-up of Saturn's Rings
In this back-lit image from the Cassini spacecraft, the Sun illuminates Saturn's rings from behind, revealing the fine structure of multiple thin rings.
Figure 17. Solar Nebula
A chaotic cloud of interstellar gas and dust collapses under its own gravity (A). Most of the mass falls to the center to form and ignite the Sun, but the residual spin of the cloud prevents it from collapsing in one direction, resulting in a flat rotating disk (B). The particles in the disk coagulate to form larger objects, and the largest ones sweep out clear lanes from the debris disk (C). This process continues as the colliding particles become larger and fewer (D), eventually leaving the solar system in its present form (E).
Figure 18. Planetesimals
In this stage of formation of a planetary system, colliding asteroid-size bodies orbit around the central star.
Figure 19. BETA PlCTORIS
This 1997 false-color image shows a debris disk seen edge on in orbit around the star Beta Pictoris, which some twenty years earlier had provided the first evidence of planetary formation around a star outside our solar system. The telescope has blocked out the direct light from the star to reveal the fainter light reflected from the disk. The inner gap in the disk suggests that planets are forming there. Most young stars have such orbiting disks.
Figure 20. Comet Machholz
The extended atmosphere, or coma, of the comet blows away from the Sun to form faint tails of dust and ionized gas.
Figure 21. Olive Oil and Comets
English astronomer William Huggins compared the spectra of vaporized olive oil and ethylene (olefiant gas) with the spectra of two comets, which he observed in 1868. He correctly deduced that comets contain carbon-bearing substances.
Figure 22. Comet NEAT Spectrum
The light of Comet NEAT (shown on the jacket of this book) is spread out into its constituent rainbow of colors (bottom), revealing the presence of different molecules at particular wavelengths (middle).
Figure 23. End of the World
An illustration by R. Jerome Hill, published in Harper's Weekly, May 14, 1910, depicting the romantic fatalism inspired by the coming of the "cyanide laden" Halley's Comet.
Figure 24. Iapetus
The surface of this mysterious satellite of Saturn has two distinct zones, one icy and very bright, the other covered by a very dark red material of unknown composition. This bimodal distribution of brightness is unique in the solar system, as is the ridge around the satellite's equator.