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Text, Viewspace. The show will continue in 15 seconds. Coming up: See how shadows reveal mysteries in space. 
The timer at top right counts down from 15 seconds. 
The text appears on a background of stars which move slowly towards and past us. 

The northern atlantic ocean seen from high above. Text, In the spring of 1919 a team of astronomers organized an expedition from england to south america and africa. As the map pans south, a dotted line travels from the United Kingdom down to Africa, branching towards Sobral, Brazil in south america and Principe in the cape of africa. Text, Their goal, to observe a total solar eclipse, test albert einstein's general theory of relativity. The a line representing the eclipse path extends from the left side of the map to the right, crossing through both Sobral Brazil and Principe in Africa.
An animation of a dark moon moving over a white sun. Text, Shadow of the moon.
August 21, 2017, Oregon, United States. A halo of bright sunlight shines around the dark circle of the moon. Text, a solar eclipse occurs when the moon passes directly between earth and the sun. Light speeding from the sun is halted by the giant mass of rock blocking its path. Stars that are invisible during the day appear in the sky beside the darkened sun . May 29, 1919, sobral, brazil, 9 A M local time. Stars in the sky next to the eclipsed sun. Text, It was these background stars, not the eclipse itself, that the astronomers had traveled so far to see.
An animation of the earth and sun in space, with a star behind the sun. Text, Actual location of star. According to Einstein, light traveling through space past massive objects like the sun should curve more than previously calculated. A line moves from the star past the sun and towards earth, bending as it passes the sun.
A straight dotted line straight from earth to a point near the star. Text, apparent location of star. As a result, stars should look like they are in slightly different locations when the sun is close to them in the sky than at other times of year, when the sun is in a different part of the sky. View from earth, 1919 eclipse, months leading up to eclipse. A chart of Stars in the sky. Solid dots representing observed light and hollow dots representing the actual location. Text, but usually we cannot see the shifted stars next to the sun. during the day, the sun is too bright. The only time to record this shift and test einstein's theory is during a total solar eclipse.
By chance, the apparent sizes of the sun and moon in the sky are almost the same. A diagram of the small moon casting a shadow on earth as it passes in front of the sun. Lines appear showing a partial eclipse covering a large area on the earth and a total eclipse covering a very small area. Text, The Moon can mask the Sun completely.
January 27, 2012, coronal mass ejection, sun eclipsed by coronagraph, nasa's solar and heliospheric observatory. Some investigations of the sun, moon, earth and space itself are possible only when the sun is blocked completely. Plumes of pale cloud-like flames erupting from the edge of the sun, which is blocked by a circle. An animation of the moon orbiting the sun. Text, Eclipse occurs. Shadow passes through orbital plane. Scientists were eager to test Einstein's theory, but total solar eclipses occur only once every 18 months or so. The moon orbits earth on a plane that is tilted relative to earth's orbital plane. Eclipse does not occur, shadow does not pass through orbital plane. Most months, the moon's shadow passes above or below earth.
An antique map of south america and africa showing the path of totality, may 29, 1919. The path of the total eclipse. Text, As they made plans to test Einstein's theory, the scientists knew when and where the next suitable eclipse would occur. Sobral Brazil, 12:01 U T, Principe Africa, 14:16 U T. Years of observations and careful calculations make it possible to predict the motion of objects in the sky and the exact date, time, and path of the eclipse. As predicted, the moon's shadow fell over Sobral first and then sped eastward, reaching Principe 2 hours later. A photo of a black circular moon passing in front of the sun. Text, May 29, 1919, Sobral Brazil. In both locations, the astronomers took advantage of the five minutes of totality to photograph the eclipsed sun and surrounding sky. On returning to England several months later, the scientists analyzed their results. A blurry image of a white dot, apparent location of star. They carefully compared the apparent positions of the stars during the eclipse to the stars' actual positions, as photographed in the night sky at other times of year. Actual location of star near apparent location, a barely visible dot. Text, the observations of the 1919 eclipse, particularly those from Sobral, provided compelling evidence for Einstein's theory.
Since 1919 the investigation has been repeated many times with similar results. Photos of astronomers with telescopes at the 1922 eclipse australia, 1936 eclipse europe and asia, 1952 eclipse sudan. Text, The warped fabric of space that Einstein described is revealed by the shadow of the moon.
The dark circle of the Moon's shadow passes across the face of the earth. Text, Our universe is further illuminated with the shadow of each passing eclipse.(SPEECH)
at-a-GLANCE. Transits.
Photos showing the evolution of a solar eclipse
Once every 18 months or so, Earth is treated to a spectacular celestial event: a total eclipse of the Sun.
As the Moon passes in front of the Sun, its shadow falls over Earth's surface and the sky grows dark.
Photo of Earth from space, showing the shadow of the Moon.
An eclipse is a special type of event known as a transit.
animation of the Moon orbiting the Earth
A transit occurs when one celestial body passes in front of another.
Telescopic images of a small planet passing in front of the Sun
In 2012, Venus passed directly between Earth and the Sun. Although a transit of Venus does not cast a visible shadow on Earth's surface, it does block some of the Sun's light.
Transits can reveal characteristics of the transiting body that are otherwise difficult to observe.
It was during a transit in 1761 that the hazy atmospheric halo surrounding Venus was first discovered.
Telescopic photo showing Venus's hazy halo
More recently, astronomers have been able to determine the composition and structure of Venus's atmosphere by analyzing sunlight that passes through it.
illustration of light passing through Venus's atmosphere
There are other transits that can be detected with sophisticated space telescopes.
A star will appear to dim slightly if a planet moves in front of it.
A repeating pattern of change in brightness reveals the existence of a planet -- or many planets -- orbiting a distant star.
Scientists can also use transits to study exoplanet atmospheres by analyzing the starlight that passes through them.
NASA's current and next generation of space telescopes will continue to analyze the shadows of transiting exoplanets and their atmospheres.
From the awe-inspiring darkness of a total solar eclipse, to the rare sight of Venus silhouetted against the Sun, to the barely detectable dimming of a distant star transited by an exoplanet...
Transitory shadows reveal secrets of the planets, moons, and star systems.
A black sphere in the center of a grey white background. Text, coronagraph. Eclipse on demand.
Overhead view of moon orbiting earth.
Text, During a total solar eclipse, the moon blocks the blinding light of the sun. Illustration not to scale.
Stars, planets, and features of the sun's corona that are otherwise invisible during the day appear in the darkened sky.
Image of moon in front of sun. Whiskey Mountain, Wyoming, August 21, 2017. Labels, the moon, star, solar corona.
Text, In 1930, French astronomer Bernand Lyot invented the coronagraph, a tool designed to mimic this rare natural event, creating an eclipse on demand. Solar prominence viewed using coronagraph. Sun eclipse by Lyot's coronagraph.
A basic coronagraph consists of a disk that blocks more than 99.99% of the sunlight passing through the telescope.
Though complex in detail, a coronagraph works essentially the same way your hand does when blocking the glare of high beam headlights.
Labelled diagram. Sunlight, lens, coronagraph, image of the corona.
Today, coronagraphs allow us to map streamers, monitor solar eruptions, and track comets as they round the sun.
Video of comet neat, solar and heliospheric observatory.
Coronagraphs can also be used to eclipse the light of objects outside the solar system, allowing us to see faint details in the space around them.
Image, HD g-1-0-0-5 star system, Hubble space telescope.
We can use coronagraphs to study disks of dust, rock, and ice surrounding individual stars within the Milky Way.
Image, HD 1-3-9-6-6-4 star system.
Debris disks like this, shining in the reflected light of their stars, contain the building blocks of planets. AU micro scopii star system.
Animation of zooming out from a planet in space. Text, Artist Conception.
By blocking the light emitted by a star, we can also detect the much dimmer light of a planet.
A black sphere over the star light.
Text, This animation of four exoplanets orbiting their star was made using data collected over the course of seven years.
Exoplanets orbiting star HR 8-7-9-9, Keck Observatory.
Direct imaging, collecting light directly from an object to create actual photographs, helps us determine important characteristics of exoplanets, such as mass, orbit, and atmospheric composition.
Combined with more powerful telescopes and advances in computer data processing, future coronagraphs will give us the opportunity to study exoplanets in even greater detail. and better understand the variety of worlds that exist in the universe. Five planets in the sky.
Text, In A Different Light, The Eagle Nebula, Electromagnetic Spectrum. The Eagle Nebula, M 16, Quick Facts. Distance, 6,500 light-years. Constellation, Serpens Cauda. Location, Sagittarius-Carina spiral arm of the Milky Way Galaxy. A bar across the bottom of the screen reads, Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma Ray.
Text, In the mid-1700s French astronomer Charles Messier peered deep into the constellation Serpens and spotted, quote, a cluster of small stars, enmeshed in a faint glow, unquote. the object is now known as M 16, number 16 in Messier's famous Catalog of Nebulae and Star Clusters.
M 16 consists of an open star cluster, a group of around 8,000 stars that formed roughly 5 and a half million years ago, and a nebula, a glowing cloud of gas and dust.
Infrared and Visible are highlighted.
Text, Seen here in a combination of visible and infrared light, M 16 resembles a bird of prey in mid-flight, and is commonly known as the Eagle Nebula.
The eagle shape is highlighted in a thin white line.
Infrared is highlighted.
Text, An infrared light image from the Herschel Space Telescope highlights the glowing body of the Eagle Nebula.
A large area surrounded by dust, illuminated by the central cluster of bright, newly-formed stars.
An infrared photo of the nebula.
Text, The high-energy electromagnetic radiation emitted by the hot stars has carved a cavity into the cold shadowy dust of this star-forming region.
The word Visible is highlighted.
A closer look at the cavity.
Text, Protruding from the cavity walls are the iconic Pillars of Creation, photographed in visible light by NASA's Hubble Space Telescope.
These immense towers of cold dust and gas block visible light, concealing the stars behind them and forming within them.
An infrared version of the pillars. The word infrared is highlighted.
Text, The infrared light detected by Hubble reveals thousands of stars beyond the pillars as well as a few stars forming within.
Unlike visible light,. infrared light can pass straight through the dense clouds of dust.
An X-ray version of the nebula. The word X-ray is highlighted.
Text, In the X-ray light detected by NASA's Chandra X-ray Observatory, the pillars disappear.
Invisible because they do not reflect the X-rays of nearby stars or give off X-rays of their own.
A thin white line highlights where the pillars would be.
The words Visible and X-ray are highlighted.
Text, Hot stars, however, shine brightly with X-ray light. From low-energy X-rays shown in red to high-energy blue, the light passes straight through the pillars of gas and dust.
The words infrared, visible, and X-ray are highlighted.
Text, A multi-wavelength image shows the infrared, visible, and X-ray light of the stars, dust, and gas of the Eagle Nebula, and the stars that lie beyond it.
The image reveals that most of the stars glowing with X-rays lie outside the pillars, not within them, a sign that the star formation in this region may be past its prime.
Viewing the cosmos in different types of light allows us to look into the shadows and better understand the structure, composition, and history of cosmic objects like the Eagle Nebula.


 Red square against starry sky. Icons, star, galaxy, constellation, asteroid, solar system. Text, What in the universe? 

Image, the sky with stars and luminous clouds. 

Text, Far outside our solar system, more than 1,000 light years from Earth, is a star-forming region known as the Serpens Nebula. 

Part of the nebula is illuminated by the bright young star HBC 672. Dark wing-like shapes project out from either side of the star. 

Text, What are these dark wings? 

A., jets of superheated gas, B., regions of empty space, C., soot billowing from a planet, D., shadows cast by rock and ice. 

D is highlighted. 

This exotic structure is nicknamed the Bat Shadow. 

Shadows of a circumstellar disk, Serpens Nebula, Milky Way galaxy. Like many young stars, HBC 672 is embedded in a cloud of dust and gas. The star illuminates the cloud, which looks bright and foggy because of the way it reflects and scatters the starlight. 

Wide field camera 3, Hubble Space Telescope near infrared light. 

But some of the light from HBC 672 is blocked by a circumstellar disk, a wide ring of rocky and icy material orbiting the star. 

The disk casts a shadow deep into the cloud. 

Given its distance, the disk is too small to see directly. But we can infer that it exists and figure out how it is oriented based on its shadow. 

By studying the shadow in detail, astronomers can even estimate the shape and mass of the disk and the sizes of the particles within it. 

It is likely that this disk contains everything from microscopic dust grains to fully grown planets. 

Text, Did you Know? Dark Matter.
Did you know? Dark Matter does not cast shadows. Map of dark matter in galaxy cluster C.I 0024 plus 17, 5 billion light-years away. Hubble Space Telescope.
Did you know? Dark matter makes up more than 80% of the matter in the universe.
These bluish clouds representing dark matter look shadowy and ghost-like.
But in reality, dark matter is completely transparent.
A blotchy blue background with bright spots of light.
Text, This image is not an actual photograph of dark matter.
It is a map that shows where dark matter is located.
A space scene with a black background and many dots of light in different sizes.
Text, Photograph of galaxy cluster C.I 0024 plus 17, with light distorted by invisible dark matter. Hubble Space Telescope.
Dark matter is invisible because it does not absorb, reflect, or emit any type of light.
We know that it exists and can map it because of the gravitational effects it has on normal matter and on light.
Some of the light distorted by dark matter. Three circles appear around bluish oblong shapes in the space image.
Text, Dark matter affects the orbits of stars in the galaxies and the paths that light takes through space.


 Image of the Milky Way with silhouettes of rock formations in front. 

Text, dark constellations. 

Globe with a point at Utah, United States. Text, Panorama of the Milky Way Utah, United States. 

For millennia, people have been captivated by the broad river of light, the milky way, and the patterns of stars that light up the night sky. 

The galaxy. Greek figures mapped onto the constellations. 

Text, From these patterns arose constellations and stories of heroes and tricksters, gods and goddesses, creation and destruction. 

Text, Modern Western constellations based on ancient Greek and Islamic astronomy. 

Hawaiian starlines used by Polynesian navigators. Different patterns map onto stars. 

Traditional Dakota, or Lakota, star knowledge, north central United States and Canada. 

Different figures. 

Point on globe at Utah, United States, 44 degrees north. 

Point at Cusco, Peru, 13 degrees south. 

Five hundred years ago, from the peaks of the Andes Mountains in south america, the Inca civilization had its own view of the night sky. 

The Inca constellations were assembled not only from bright points of light, but also from diffuse glowing regions and dark patches in between. 

A figure in the sky. Text, painting of the inca view of the night sky,, Cusco, Peru. 

For the incas, the band of the Milky Way was the celestial river, Mayu, the source of earth's water. 

The dark clouds, or yana phuyu, were animals that came to drink from the life-giving river. 

Mach acuay, the serpent. 

Hanp atu, the toad. Yutu tinamou, the partridge. Llamacnawin, eyes of the mother llama, unallamach, baby llama, atoq, the fox, micheq, the shepherd, 

Telescopes on the ground and in space provide yet another view of the figures in the night sky. 

With telescopes we can see that each of the mother llama's bright eyes is composed of a small group of stars. 

Zooms in on two stars in the constellation. Alpha centauri system, riger kentaurus, visible light. Beta centauri system, hadar. Infrared light. 

The fox's red eyes are clouds of glowing gas and starlit dust known as nebulae. 

Zooms in on the constellation. Lobster nebula, x ray visible, and infrared light. Cat's paw nebula, visible light. 

And the dark bodies of the animals are not just empty voids. 

Zooms in on Milky Way. Central Milky Way, visible light. 

They are dust clouds so dense that they block the visible light of more distant stars almost completely. It is within and from these dense clouds of dust that new stars, and new planetary systems, are born. 

Although it is dark to our unaided eyes and to the sensors in a visible light telescope, the shadowy dust of the milky way emits a bright infrared glow. Lobster Nebula and Cat's Paw nebula, infrared light. 

While our eyes allow us to see the energy of hot stars and gas of the animal's eyes, the infrared telescope reveals the energy emitted by their warm dusty bodies. 

Panorama of the milky way, Cerro Paranal, Chile. Buildings in a deserted area. 

Whether viewed through the lens of human culture or the optics of a telescope, stories of the cosmos are written in the light and silhouettes of the night sky.