2.10: Accessible Description

Figure 2.1.1 Earth

A composite satellite image of Earth's Western Hemisphere.

Image Elements

• Earth appears as a blue and green sphere against the black background of space.
• North America is visible at the upper left, with South America extending below it.
• The Atlantic Ocean lies to the right of the continents, and the Pacific Ocean lies to the left.
• White swirling cloud formations are scattered across the oceans and land, including a large spiral storm system off the west coast of North America.
• Green and tan land areas mark forests and drier regions, while deep blue marks the oceans.

Credit: modification of work by R. Stockli, A. Nelson, F. Hasler, NASA/GSFC/NOAA/USGS

Figure 2.1.2 Earth and Moon

An illustration of Earth and the Moon drawn to scale for both size and distance.

Image Elements

• Earth, a blue and white sphere, is shown at the far left of the image.
• The Moon, a small gray sphere, is shown at the far right of the image, separated from Earth by a wide expanse of black space.
• The Moon's diameter appears about one fourth the size of Earth's, and the distance between them is roughly 30 times Earth's diameter.

Credit: modification of work by NASA

Figure 2.1.3 Solar System

A diagram of the Sun, the eight planets, and five dwarf planets, all drawn to scale by size.

Diagram Elements

• At the far left is a small portion of the Sun's disk, far larger than any of the planets.
• The eight major planets are arranged in a row in order of increasing distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
• Mercury, Venus, Earth, and Mars are small rocky planets, much smaller than the gas giants Jupiter and Saturn, shown with Saturn's rings, and the ice giants Uranus and Neptune.
• Below the main row, five dwarf planets are shown: Ceres, positioned below Mars near the asteroid belt, and Pluto, Haumea, Makemake, and Eris, positioned below and to the right of Neptune.
• All dwarf planets appear much smaller than any of the eight major planets.
• The image notes that the true distances between the planets are far greater than shown; only relative sizes are to scale.

Credit: modification of work by NASA

Figure 2.1.4 Spiral Galaxy

A Hubble Space Telescope image of the barred spiral galaxy NGC 1073, thought to be similar to our own Milky Way Galaxy.

Image Elements

• An elongated, bright central bar of stars runs diagonally through the middle of the galaxy, tilted about 45 degrees from the bottom of the frame.
• Spiral arms extend from each end of the bar, curving clockwise and wrapping around the galaxy's center.
• The spiral arms are traced by clusters of blue stars, marking regions of active star formation, against a background of fainter, older yellow stars.
• Dark dust lanes are woven through the arms, tracing the galaxy's spiral structure.

Credit: NASA, ESA

Figure 2.1.5 Milky Way Galaxy

A nighttime photograph of the Milky Way seen edge-on from Earth, rising above a rock formation in the California desert.

Image Elements

• A dense, glowing band of stars stretches vertically from the horizon to the top of the frame, representing the disk of the Milky Way Galaxy seen edge-on from within it.
• Dark, wispy lanes of interstellar dust cut through the bright band, blocking the light of stars behind them.
• The dark silhouette of a standing person appears at the bottom of the image, looking up at the sky, providing a sense of scale.
• Jagged rock spires of the Trona Pinnacles are silhouetted along the horizon, lit by a warm orange glow from the setting or rising sun.

Credit: Ian Norman

Figure 2.1.6 Star Cluster

A Hubble Space Telescope image of the globular star cluster M9.

Image Elements

• Thousands of stars are packed tightly together in a roughly circular, ball-shaped grouping that fills the center of the image.
• The density of stars is greatest near the center of the cluster and drops off gradually toward the edges of the image.
• Most stars appear white or pale blue, with a scattering of orange and red stars visible throughout the cluster.

Credit: NASA, ESA

Figure 2.2.1 Zenith and Horizon

A diagram of an observer standing beneath the dome of the sky, showing the zenith and horizon.

Diagram Elements

• A human figure stands at the center of a series of concentric red rings representing the ground extending outward in all directions.
• A dark dome, representing the sky, arches overhead and meets the ground at the outermost ring, labeled Horizon.
• A vertical yellow line rises from directly above the figure's head to the top of the dome, labeled Zenith, marking the point directly overhead the observer.

Figure 2.2.2 Celestial Sphere

A diagram of Earth surrounded by the imaginary celestial sphere, showing how key reference lines and points project outward from Earth onto the sky.

Diagram Elements

• Earth sits at the center of a large transparent sphere representing the sky, tilted so that the North Pole, labeled N, points toward the upper right.
• A line extended from Earth's North Pole meets the sphere at a point labeled North celestial pole; a gray circular arrow around this point shows the apparent counterclockwise motion of the stars.
• Earth's equator is projected outward onto the sphere as a ring labeled Celestial equator, lying halfway between the poles.
• An oversized human figure stands on Earth's surface in North America. A vertical orange line rises from the figure to a point on the sphere labeled Your zenith, the point directly overhead the observer.
• A ring labeled Your horizon circles the sphere at the level of the observer, representing the boundary between the visible and hidden halves of the sky from that location.

Figure 2.2.3 South Celestial Pole

A long-exposure night sky photograph showing star trails circling the south celestial pole above an astronomical observatory.

Image Elements

• Instead of appearing as points of light, the stars are stretched into curved, concentric arcs because the camera's shutter stayed open while Earth rotated during the exposure.
• The arcs form nearly complete circles around a common center point near the top of the frame, marking the location of the south celestial pole.
• The domes of several telescopes are silhouetted along the bottom of the image, anchoring the scene at an observatory on the ground.

Credit: ESO/Iztok Bončina

Figure 2.3.1 Latitude and Longitude

A globe of Earth marked with lines of latitude and longitude, used to locate Washington, DC.

Diagram Elements

• The globe is centered on the North Atlantic Ocean, with North America on the left and Europe and Africa on the right.
• White curved lines of longitude run from pole to pole, and white curved lines of latitude run parallel to the equator, forming a grid over the surface.
• The equator is labeled at the lower right of the globe.
• The Prime Meridian of longitude, the reference line for measuring longitude, is labeled at the upper right.
• An orange arrow labeled Latitude runs northward from the equator in South America.
• An orange arrow labeled Longitude runs westward from the Prime Meridian.
• The two arrows meet at a point in North America labeled Washington, DC, showing how latitude and longitude together specify one location.

Figure 2.3.2 Sidereal Day and Solar Day

A diagram comparing Earth's rotation relative to a distant star with its rotation relative to the Sun.

Diagram Elements

• The Sun is drawn as a yellow disk on the left side of the diagram.
• Earth is shown at two positions on the right, labeled Earth, day 1 (lower) and Earth, day 2 (upper).
• At day 1, a white arrow labeled To remote point on celestial sphere points left from Earth, passing near the Sun toward a distant star, aligned with the observer's line of sight.
• A curved arrow around each Earth position shows the direction of Earth's rotation.
• By day 2, Earth has completed one full rotation relative to the distant star, so its arrow to the remote point on the celestial sphere again points in the same direction, parallel to the day 1 arrow.
• A dashed line connects the day 2 position to the Sun as seen on day 1, showing where the Sun would appear if Earth had not moved along its orbit.
• The angle between the dashed line and the new direction to the Sun is labeled 1°, representing the extra rotation Earth must complete for the Sun to return overhead.

Figure 2.3.3 Foucault's Pendulum

A photograph of a Foucault pendulum swinging above a circular wooden platform ringed with targets.

Image Elements

• A silver pendulum bob hangs from a long wire at the center of a circular wooden platform divided into radiating wedge-shaped sections.
• Small pegs, the targets, are arranged in a ring around the outer edge of the platform.
• Several viewers stand at the railing around the platform, watching the pendulum swing.
• As Earth rotates beneath the pendulum, its plane of swing gradually shifts direction, so that over about 12 hours it knocks down each target around the ring in turn.

Credit: Manuel M. Vicente

Figure 2.4.1 Star Paths at Different Latitudes

Three panels showing how the apparent daily motion of stars differs depending on an observer's latitude on Earth.

Panel (a): At the North Pole

• An observer stands at the North Pole, where the zenith directly overhead coincides with the North celestial pole.
• The observer's horizon, drawn in red, is projected onto the surrounding sky as a circle.
• White curved arrows circle counterclockwise around the zenith, showing that stars trace circles around this point and never rise or set.

Panel (b): At the Equator

• An observer stands on the equator, where the zenith is directly overhead.
• The North celestial pole lies on the observer's horizon rather than overhead.
• White curved arrows circle counterclockwise around the North celestial pole, showing that stars rise straight up in the east and set straight down in the west.

Panel (c): At an Intermediate Latitude

• An observer stands in the Northern Hemisphere partway between the pole and the equator.
• The North celestial pole appears partway between the zenith and the horizon, at an angle above the horizon equal to the observer's latitude.
• White curved arrows circle counterclockwise around the North celestial pole, showing that stars near the pole do not set, while stars farther from the pole rise in the east and set in the west at an angle to the horizon.

Figure 2.4.2 Constellations on the Ecliptic

A diagram of the Sun and Earth's orbit surrounded by the zodiac constellations that lie along the ecliptic.

Diagram Elements

• The Sun is drawn at the center, surrounded by a blue arrow marking Earth's orbital path.
• Earth is shown at two points along its orbit, labeled June and August.
• Fourteen constellations are arranged around the outer edge of the diagram along the path of the ecliptic: moving counterclockwise from the top, Cancer, Gemini, Taurus, Aries, Pisces, Aquarius, Capricornus, Sagittarius, Ophiuchus, Scorpius, Libra, Virgo, Leo, and back to Cancer.
• A line from the June position of Earth through the Sun points to Taurus, showing that the Sun appears to be in front of Taurus in June.
• A line from the August position of Earth through the Sun points to Cancer, showing that the Sun appears to be in front of Cancer in August.

Figure 2.4.3 The Celestial Tilt

A diagram of Earth surrounded by the celestial sphere, showing the 23.5° tilt between the celestial equator and the ecliptic.

Diagram Elements

• Earth is drawn at the center, with the North pole labeled N and South pole labeled S.
• A vertical line labeled "Line perpendicular to ecliptic" extends upward from Earth.
• A second line extends from Earth's North pole outward to the celestial sphere, forming a 23.5° angle with the perpendicular line.
• A white dashed circle labeled "Celestial equator" represents Earth's equator projected onto the sky.
• A red circle labeled "Ecliptic" represents the Sun's apparent yearly path, tilted 23.5° from the celestial equator.
• The Sun is marked at four points on the ecliptic, labeled December, March, June, and September, corresponding to the solstices and equinoxes.

Figure 2.4.4 Seasons

An illustration of Earth's axis and orbit around the Sun, shown at the two solstices and two equinoxes.

Diagram Elements

• The Sun is at the center, with Earth shown at four positions along its orbit, connected by a blue arrow indicating the direction of motion.
• At left, Earth is at the Summer Solstice, June 21, with its axis tilted 23.5° so the Northern Hemisphere points toward the Sun.
• At bottom, Earth is at the Autumnal Equinox, September 21, with its axis tilted to the side, so neither hemisphere points toward the Sun.
• At right, Earth is at the Winter Solstice, December 21, with its axis tilted so the Northern Hemisphere points away from the Sun.
• At top, Earth is at the Vernal Equinox, March 21, with its axis again tilted to the side.
• Earth's axis maintains the same 23.5° tilt and points in the same direction in space throughout the orbit.

Figure 2.4.5 Direct Sunlight

Two panels comparing how sunlight strikes Earth's surface in summer and winter.

Panel (a): Summer

• Five parallel arrows representing 1 square meter of sunlight strike the ground at a steep angle of 73°.
• Where the light hits the ground, it covers an area of 1.04 square meters, concentrating the sunlight.

Panel (b): Winter

• The same five arrows representing 1 square meter of sunlight strike the ground at a shallow angle of 26°.
• Where the light hits the ground, it spreads over an area of 2.24 square meters, more than twice the area covered in summer, so the same amount of sunlight heats the ground less effectively.

Figure 2.4.6 Seasonal Paths of the Sun

Three diagrams comparing the Sun's daily path across the sky at the June solstice, the equinoxes, and the December solstice.

Left: Sun's Path June 21

• The Sun's path is drawn as a faint yellow ellipse that rises north of east, arcs above the celestial equator, and sets north of west.

Center: Sun's Path March 21 and September 21

• The Sun's path lies directly along the celestial equator, rising due east and setting due west.

Right: Sun's Path December 21

• The Sun's path is drawn as a faint yellow ellipse that rises south of east, arcs below the celestial equator, and sets south of west.

In each panel, the observer stands at the center of a horizon plane, with north to the left and west at the bottom of the horizon, and a dashed ellipse marks the celestial equator running through east and west.

Figure 2.4.7 Earth on June 21

A diagram of Earth illuminated by sunlight on the date of the summer solstice in the Northern Hemisphere.

Diagram Elements

• Earth's axis of rotation is labeled and tilted toward the upper left, toward the incoming sunlight.
• Three red arrows represent sunlight striking Earth's surface from the left.
• Five circles of latitude are labeled from bottom to top: Antarctic Circle, Tropic of Capricorn, Equator, Tropic of Cancer, and Arctic Circle.
• The region within the Arctic Circle receives continuous sunlight, while the region within the Antarctic Circle remains in darkness.

Figure 2.4.8 Earth on December 21

A diagram of Earth illuminated by sunlight on the date of the winter solstice in the Northern Hemisphere.

Diagram Elements

• Earth's axis of rotation is labeled and tilted toward the upper right, away from the incoming sunlight.
• Three red arrows represent sunlight striking Earth's surface from the left.
• Five circles of latitude are labeled from bottom to top: Antarctic Circle, Tropic of Capricorn, Equator, Tropic of Cancer, and Arctic Circle.
• The region within the Antarctic Circle receives continuous sunlight, while the region within the Arctic Circle remains in darkness.

Figure 2.5.1 Phases of the Moon

A diagram of the Moon's orbit around Earth showing its eight phases and how each appears from Earth.

Diagram Elements

• Earth is drawn at the center, with sunlight arriving from the right, shown as parallel yellow arrows.
• The Moon is shown at eight labeled positions, A through H, spaced evenly around its orbit.
• Small inset images next to each position show how the Moon appears to an observer on Earth at that point in the cycle.

Moon Positions

• Position A, at far right, nearest the Sun: New — the Moon's dark side faces Earth and it is invisible in the sky.
• Position B, upper right: Waxing crescent — a thin sliver of the Moon is illuminated.
• Position C, top: First quarter — half of the visible disk is illuminated.
• Position D, upper left: Waxing gibbous — more than half the disk is illuminated.
• Position E, at far left, farthest from the Sun: Full — the entire visible disk is illuminated.
• Position F, lower left: Waning gibbous — illumination begins to shrink from more than half.
• Position G, bottom: Third quarter — again half of the visible disk is illuminated.
• Position H, lower right: Waning crescent — only a thin sliver remains illuminated before returning to new.

Credit: modification of work by NASA

Figure 2.5.2 Synchronous Rotation

Two panels comparing the Moon's motion if it did not rotate with its actual synchronous rotation.

Panel (a): Without Rotation

• Earth is at the center of the Moon's blue elliptical orbit.
• The Moon is shown at four positions around the orbit, each marked with a white arrow pointing straight up in the same direction.
• Because the arrow always points the same way in space, if the Moon did not rotate, a fixed point on its surface would face Earth only at the bottom position.

Panel (b): With Rotation

• Earth is again at the center of the Moon's orbit, with the Moon shown at the same four positions.
• A small curved arrow at each position shows the Moon completing one rotation on its axis during the orbit.
• Because of this rotation, the white arrow marking the same fixed point on the Moon points toward Earth at every position, showing that the same side always faces Earth.

Figure 2.5.3 Solar Eclipse

A two-part diagram showing the geometry of a solar eclipse shadow and the resulting views of the Sun.

Panel (a): Shadow Geometry

• The Sun is drawn as a large yellow disk at the left.
• A smaller blue disk, representing an eclipsing body such as the Moon, sits to the right of the Sun.
• Lines from the top and bottom edges of the Sun cross at the eclipsing body and continue outward, forming a dark, narrowing umbra and a lighter, widening penumbra that extend to the right.
• Four numbered points mark locations within the shadow: point 1 lies within the umbra closest to the eclipsing body, points 2 and 3 lie in the penumbra, and point 4 lies farther out where the umbra has narrowed to a point and diverges again.

Panel (b): Views from Each Point

• At point 1, the Sun is completely blocked, a total eclipse.
• At points 2 and 3, part of the Sun remains visible beside the dark disk, a partial eclipse.
• At point 4, the eclipsing body appears smaller than the Sun, leaving a bright ring of light around it, an annular eclipse.

Figure 2.5.4 Total Solar Eclipse

A diagram of the geometry of a total solar eclipse, showing the Sun, Moon, and Earth aligned.

Diagram Elements

• The Sun is drawn at the lower left.
• Earth is drawn at the upper right, with the Moon's blue orbital path shown as a ring around it.
• The Moon is positioned directly between the Sun and Earth, at new moon phase.
• A dark, narrowing shadow extends from the Moon's night side across a small area on Earth's surface, labeled Eclipse path, marking the region where the total eclipse is visible.

Figure 2.5.5 The Sun's Corona

A photograph of the Sun's corona during a total solar eclipse.

Image Elements

• The Moon appears as a solid black disk at the center of the image, completely covering the Sun.
• Around the edge of the Moon's disk, faint white streamers and tendrils of light extend outward in irregular patterns, fading into the dark sky.

Credit: modification of work by Lutfar Rahman Nirjhar

Figure 2.5.6 Lunar Eclipse

A diagram of the geometry of a lunar eclipse, showing the Moon passing through Earth's shadow.

Diagram Elements

• The Sun is drawn at the lower left, and Earth is drawn at the upper right with the Moon's blue orbital path shown around it.
• Earth's shadow extends as a dark cone from its night side toward the upper right, away from the Sun.
• The Moon is shown at three positions along its orbit: at position A, to the right of Earth, the Moon has not yet entered the shadow and appears as a full moon as seen from Earth.
• At position B, above and to the left of A, the Moon has begun entering Earth's shadow, marking the start of the eclipse.
• At position C, above and to the left of B, the Moon is partway through exiting the shadow on the opposite side.

Figure 2.5.7 Solar and Lunar Eclipse

Two photographs showing a total solar eclipse and a total lunar eclipse.

Image (a)

• On the left.
• A composite photograph of the 2017 total solar eclipse, showing the Moon's black disk surrounded by the pale, wispy streamers of the Sun's corona extending outward against a dark blue sky.

Image (b)

• On the right.
• Three views of the Moon during a 2018 total lunar eclipse are shown side by side.
• At center, the fully eclipsed Moon glows a dull reddish-orange from sunlight bent through Earth's atmosphere.
• On either side, partially eclipsed crescents of the Moon show Earth's curved shadow beginning to cover, and later uncovering, the lunar disk.

Credit a: modification of work by Rick Fienberg, American Astronomical Society/TravelQuest International; Credit b: modification of work by Brian Day

Figure 2.6.1 Astronauts on the Moon

A photograph of the Apollo 15 lunar lander, rover, and an astronaut on the Moon's surface.

Image Elements

• At center is the lunar landing module, standing on four legs on the gray lunar surface.
• To the right of the lander is the lunar rover, a small open vehicle used by the astronauts to travel across the Moon.
• At left, an astronaut in a white spacesuit stands saluting near an American flag planted in the ground.
• Numerous footprints from the astronauts are scattered across the foreground in the fine lunar soil.

Credit: modification of work by David R. Scott, NASA

Figure 2.6.2 Orbits of the Planets

A diagram of the Solar System showing the orbits of the eight planets and five dwarf planets.

Diagram Elements

• The Sun sits at the center, surrounded by the blue, nearly circular orbits of Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, and Neptune, all lying close to the same flat plane.
• Four additional orbits, drawn in red, belong to the dwarf planets Pluto, Haumea, Makemake, and Eris.
• The red orbits are noticeably more elongated and tilted than the blue orbits, crossing above and below the plane of the main planets rather than lying flat within it.
• Labels identify each object at the point along its orbit shown in the diagram.

Figure 2.6.3 Mercury

A black-and-white image of Mercury's cratered surface taken by the Mariner 10 spacecraft.

Image Elements

• The image shows a roughly 400-kilometer-wide region of Mercury's surface, tilted at an angle within the frame.
• Craters of many sizes cover the entire surface, with numerous large craters overlapping one another, especially in the upper portion of the image.
• Smaller craters and pockmarks are scattered throughout, giving the surface a heavily worn, ancient appearance.

Credit: modification of work by NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Figure 2.6.4 Outer Planets

A montage comparing the sizes of the four giant outer planets to Earth.

Image Elements

• From left to right, the four giant planets are shown to scale: Jupiter, a large banded orange and white sphere; Saturn, a golden sphere encircled by a wide, tilted ring system; Uranus, a pale blue sphere; and Neptune, a slightly smaller deep blue sphere.
• Earth is shown below and between Jupiter and Saturn, appearing tiny in comparison to any of the four giant planets.

Credit: modification of work by NASA, Solar System Exploration

Figure 2.6.5 Pluto

A close-up image of part of Pluto's surface taken by the New Horizons spacecraft.

Image Elements

• A smooth, pale, icy region called the Sputnik Plain covers most of the upper right portion of the image.
• Rugged, heavily cratered, reddish-brown terrain covers the lower center and upper left of the image, contrasting sharply with the smooth plain.
• The curved limb of Pluto is visible at the upper left, showing the dwarf planet's rounded shape against the black background of space.

Credit: modification of work by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Figure 2.6.6 Saturn with Rings

A Cassini spacecraft image of Saturn and its rings, taken nearly overhead one of its poles.

Image Elements

• Saturn's rings are seen nearly face-on, forming a wide, tilted oval that completely encircles the planet.
• Sunlight arrives from the lower left, casting a thin, dark shadow of the rings onto Saturn's cloud tops.
• In the upper right, Saturn itself casts a dark shadow across a portion of the rings, partially interrupting their bright band.
• Saturn's cloud tops appear pale gold and white, with faint horizontal banding.

Credit: modification of work by NASA/JPL/Space Science Institute

Figure 2.6.7 Asteroid Eros

An image of the asteroid Eros taken by the NEAR-Shoemaker spacecraft.

Image Elements

• Eros is shown as an irregular, elongated gray object, roughly potato-shaped rather than spherical.
• The surface is covered with craters of many sizes, including several large, deep craters near the upper right and lower left of the object.
• The asteroid is set against the black background of space, with sunlight illuminating it from the upper right.

Credit: modification of work by NASA/JHUAPL

Figure 2.6.8 Comet Churyumov-Gerasimenko

A Rosetta spacecraft image of Comet 67P/Churyumov-Gerasimenko near its closest approach to the Sun.

Image Elements

• The comet's nucleus has two irregular, rocky lobes connected by a narrower neck, giving it a shape sometimes compared to a rubber duck.
• Sunlight illuminates the nucleus from the upper left, brightly lighting the two lobes against the black background of space.
• Faint, bright streaks of escaping gas and dust radiate outward from the sunlit surfaces of both lobes.
• No jets or streaks are visible coming from the shaded, unlit portions of the nucleus.

Credit: modification of work by ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0

Figure 2.7.1 Orion

Two panels comparing a historical star atlas illustration of Orion with a modern photograph of the same constellation.

Image (a)

• On the left.
• A seventeenth-century engraving by Johannes Hevelius showing the mythical hunter Orion, fully rendered with helmet, shield, and sword, with the stars of the constellation superimposed on his figure.
• The three stars of Orion's belt are circled in red.
• An arrow points from the circled belt stars to the corresponding stars in Image (b).

Image (b)

• On the right.
• A photograph of the Orion region of the night sky, showing the same star pattern as Image (a).
• Three blue stars in a short diagonal row form the hunter's belt, matching the stars circled in Image (a).
• A bright reddish-orange star above and to the left of the belt marks Betelgeuse, the hunter's armpit.
• A bright blue star below the belt marks Rigel, the hunter's foot.

Credit a: modification of work by Johannes Hevelius; Credit b: modification of work by Matthew Spinelli

Figure 2.8.1 Constellations

An all-sky map comparing Chinese and Western European seasonal constellation groupings.

Map Elements

• The map shows the whole sky in an oval (Mollweide) projection, densely scattered with white dots representing stars.
• Dozens of small groups of stars are connected by thin yellow lines, representing the traditional Chinese constellations, which are much smaller and more numerous than Western constellations.
• A horizontal blue line marks the celestial equator, and a curving orange line marks the ecliptic, the Sun's apparent yearly path.

Chinese Seasonal Groupings

• Four large, irregularly shaped regions are shaded and labeled near the bottom half of the map: gray for Winter, blue for Spring, red for Summer, and an unlabeled dark green overlap area near the boundary of Winter and Spring.
• Each shaded region groups together the small Chinese constellations that were traditionally associated with that season.

Western European Seasonal Groupings

• Four teal-outlined diamond and square shapes are labeled near the top of the map: Autumn, Summer, Spring, and Winter, from left to right.
• These shapes are much larger and simpler than the Chinese groupings, each representing a single Western asterism used to mark a season.

Figure 2.8.2 Constellations of Different Cultures

An all-sky map of the 88 IAU-recognized constellations, color-coded by their historical and cultural origin.

Map Elements

• The map shows the whole sky in an oval projection, with the boundaries of all 88 modern constellations outlined in gray and their star patterns connected by thin cyan lines.
• Bright stars are labeled by name, including Vega, Deneb, Altair, Arcturus, Capella, Pollux, Aldebaran, Betelgeuse, Rigel, Procyon, Sirius, Canopus, and Fomalhaut.
• A horizontal blue line marks the celestial equator, and a curving orange line marks the ecliptic.

Color Key for Constellation Origin

• Light brownish shading, covering most of the map, marks constellations of Babylonian origin.
• Blue shading marks constellations of Greek origin.
• Light green shading marks constellations created by Dutch sailors in the late 1500s and early 1600s.
• Dark green shading marks an English asterism later formalized into a constellation by Hevelius in 1687.
• Dark red shading marks constellations introduced by the Polish astronomer Hevelius in 1687.
• Pink shading marks constellations introduced by the French astronomer Lacaille in 1756.
• Yellow shading marks a small number of constellations with Christian origins.

Credit: Susanne M Hoffmann (2021)