Exploring the Universe in our Collections
Sep 08, 2023
What is the universe? How big is it? How old is it? How did it begin? Since people first gazed at the stars, we have searched for the answers to questions such as these. When our view was limited to what our eyes could see, the sky was our universe. Then telescopes deepened our view, photography enhanced it, and spectroscopy broadened it. Astronomers’ use of new technologies and techniques helped them understand the universe to be more than a sky of stars. It is a realm of galaxies, expanding over billions of years.
Instruments in the Smithsonian collection trace the story of how humans have explored the universe for thousands of years. Join us in taking a look at just a few examples!
Exploring the Universe with the Naked Eye
From the dawn of human history until less than 400 years ago, what we’ve known of the universe was limited by what we could see with our eyes: a sky filled with objects in constant motion. The Earth seemed to rest at the center of a starry sphere, and the Sun, Moon, planets, and stars appeared to move around the Earth. People used measuring instruments to map the stars and to plot the changing positions of the Sun, Moon, and planets in order to understand and predict their motions, an important and practical ability for activities in those days, such as time keeping, astrological forecasting, navigation and agriculture.
Tycho Armillary Sphere (Replica)
Armillary spheres large and small were used for centuries to study the sky and to refine the celestial coordinate system, which astronomers used to locate objects in the sky. In the image below is a full-scale replica of an armillary sphere built and used by Danish astronomer Tycho Brahe in the late 1500s. An observer could use its moveable rings and sighting devices to measure the position of a celestial object or differences between the positions of two objects.
Indeed, observing was Tycho's passion, and precision was his obsession. Supported by the King of Denmark, he built two major observatories and filled them with the finest instruments, many of which he designed himself. He cataloged the positions of a thousand stars and tracked the motions of the Sun, Moon, and planets. His assistant, Johannes Kepler showed, for example, that Mars did not travel in a perfectly circular orbit. The accuracy of his measurements remained unsurpassed until the invention of the telescope. (National Museum of American History)
Looking Further: Exploring the Universe with Telescopes
In 1609 Galileo began using a new kind of instrument that magnified distant objects: a telescope. When he pointed it on the heavens, he saw countless stars and other faint objects never before seen. Suddenly, the universe was no longer limited to what the naked eye could see. As telescopes improved, astronomers continued to push back the boundaries of the known universe, peering ever deeper into the surrounding sea of stars known as the Milky Way.
Galilean Telescope (Replica)
Galileo did not invent the telescope, but he did design and build telescopes with increasingly higher magnifying power for his own use and to present to his patrons. He was a skilled instrument maker, and his telescopes were known for their high quality. Discoveries by Galileo and others suggested that the Earth and the planets circled the Sun and are physical objects rather than an ethereal universe. Multitudes of stars never before seen extended outward to a great and unknown distance. The universe was not small and confined within a starry sphere; it was vast, perhaps even infinite.
To improve the telescope’s performance, telescope makers experimented with different optical arrangements and lens-making techniques and the use of mirrors in place of lenses. From Galileo’s simple optic tube, telescopes evolved into complex precision instruments. To see ever deeper into space, astronomers used increasingly bigger telescopes. Astronomers increasingly relied upon skilled artisans capable of crafting such sophisticated devices. With these advanced telescopes, astronomers discovered moons around Jupiter and Saturn, the planets Uranus and Neptune, and mapped the shape of the Milky Way galaxy.
Seeing Fainter: Exploring the Universe with Photography
Before photography, the only way an astronomer could record an object seen through a telescope was by drawing it. Photography eliminated hours of painstaking sketching and produced more objective and detailed images. An astronomer could focus the light from a celestial object onto a photographic plate and guide the telescope to expose the plate for minutes or hours. The longer the plate remained exposed, the more light it collected, and the more detailed the resulting photograph was.
By the late 1800s, photography was changing the way astronomers studied the universe. The telescope became a high-powered camera that recorded images of objects on photographic plates. These images were less subjective than hand drawings and revealed objects and details far too faint for the eye to detect. Astronomers would soon discover that the Milky Way was only one of countless galaxies, each one a vast swirl of stars.
Ritchey 24-inch Reflecting Telescope
George Willis Ritchey designed and built a 24-inch reflecting telescope at Yerkes Observatory. He used it to take unprecedented images of nebulae, novae and other astronomical objects. Ritchey later made similar but much larger telescopes for the Mount Wilson Observatory in California. The 24-inch became the model for large, multi-functional telescopes. Edwin Hubble used it for his PhD thesis at the Yerkes Observatory, exploring the distribution of “spiral nebulae.”
Aided by photography and the ability to take photographs with the Mount Wilson 100-inch telescope, the world’s largest telescope at the time, in 1924 Edwin Hubble was able to show that the universe is composed of many galaxies, of which the Milky Way is just one, and five years later, that the universe itself is expanding, correlating the distances of these galaxies with their recessional speeds, observed spectroscopically.
Looking Even Further: Exploring the Universe with Spectroscopy
While astronomers were starting to use photography to capture light from celestial objects, they were also learning how to analyze light itself. They found that an object's spectrum, the rainbow of colors that forms when light passes through a prism, could tell them what the object was made of and how it moved. By the late 1920s the use of spectroscopy, creating and studying spectra, revolutionized our understanding of that the universe is made of and, as we mentioned before, produced an amazing discovery: the Universe of galaxies was expanding.
Prime Focus Spectrograph, 1950
In the late 1940s, a powerful new astronomical eye opened at the Palomar Observatory in southern California. The 200-inch Hale Telescope was twice as large as Mount Wilson's 100-inch telescope and could collect four times as much light. It remained the most powerful telescope in the world for over 30 years. With the 200-inch telescope, astronomers could peer deeper into the universe than ever before and refine their estimates from the 100-inch telescope of how fast the universe is expanding.
One of the most productive instruments on the new telescope was a spectrograph. Spectrographs combine the elements of a spectroscope and a camera: it spreads the light from a planet, star, or galaxy into a spectrum and records an image of that spectrum photographically on a glass plate. It was custom-made for mounting in the 200-inch telescope's prime focus cage, one of several points on the telescope where observing instruments can be attached. At the time, it was the most sensitive spectrograph in the world, mounted on the largest telescope in the world. This spectrograph was used for over 25 years and among many discoveries, examined the cores of galaxies confirming the nature of super energetic objects discovered by radio telescopes, called quasars. These are now known to be the home of supermassive black holes.
Beyond Earth: Exploring our Universe from Space
The Space Age has transformed how we explore the universe. Telescopes, photography, and spectroscopy remain our basic tools, but rockets and digital light detectors have enhanced their power. Observatories in space have broadened the range of light we can gather. Our view of the universe now extends from radio waves to gamma rays. And new technologies are revolutionizing astronomy, enabling us to create larger and more powerful telescopes than ever before.
X-rays either pass through or are absorbed by most substances and they can't be focused with lenses or ordinary mirrors. However, they will glance off a solid surface if they strike at a very shallow angle.
The orbiting x-ray observatory Chandra (named for the Indian-American astrophysicist Subrahmanyan Chandrasekhar) collected x-rays by using large cylinders of highly polished interior glass surface to collect the x-rays and then wire grids and tiny cylindrical collecting tubes to amplify and record the radiation.
Hubble Space Telescope Wide Field Planetary Camera, Flown
The Hubble was designed for long-term use and to be serviced in orbit every few years by Space Shuttle astronauts. The light gathered by its single large mirror is directed to several cameras and spectrographs that can record visible, ultraviolet, and infrared light. The servicing capability proved to be critical. After it was launched in 1990, its mirror was found to be defective. The first servicing mission in 1993 inserted new instruments and devices that corrected the defects. This camera was installed on that servicing mission and produced the first generation of spectacular images Hubble is famous for.
Beyond Light: Exploring the Universe with Cosmic Rays and Neutrinos
Cosmic rays (despite their name) and neutrinos are not forms of light, but high-energy particles traveling at high speeds. Some originate in our Sun, but most come from exploding stars and other sources beyond our solar system. They provide one of the few ways we have of directly studying matter from elsewhere in the Universe. In 1911, Austrian scientist Victor Hess was able to successfully determine that the intensity of charged particles increased with height in the atmosphere, our first clue that this energy was cosmic, hence now called cosmic rays.
Hess set out to solve a puzzling question: Why did radiation detectors register charged particles when no apparent source of radiation was present? On manned balloon flights to the upper atmosphere, he discovered that the frequency and intensity of these charged particles increased with altitude. Hess concluded they were either produced high in the atmosphere or came from space. They were later named cosmic rays, because they were thought to be a form of high-energy light. They are actually high-energy particles of matter.
Kamiokande II Neutrino Observatory Detector
Nearly mass-less particles traveling close to the speed of light, neutrinos are so energetic they can pass right through the Earth itself. To detect these elusive particles, astronomers go not to great heights, but to great depths.
This glass bulb is a single light detector from the Kamiokande II neutrino observatory in Japan. The observatory was built in an abandoned zinc cadmium mine deep underground, so the overlying rock would filter out less-energetic particles. It consists of a huge tank filled with ultra-pure water and lined with 10,000 of these tubes, which detect bursts of light caused by neutrinos piercing the water. In 1987 Kamiokande II detected neutrinos from an exploding star in a nearby galaxy, the first detection of neutrinos from an object other than our Sun.
What is the universe? How big is it? How old is it? How did it begin? Our understanding of the universe continues to evolve as new tools and techniques are employed in astronomers. But we still have no final answers. Our exploration continues.
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