In the 1800s, scientists discovered the realm of light beyond what is visible. Electromagnetic radiation, often simply called radiation, extends on either end of the spectrum from visible light. Much of the story of the universe past, present and future written in these wavelengths of the electromagnetic spectrum, which are not ble on Earth’s surface. Even as in visible light, radio waves, and some infrared waves, Earth’s atmosphere blocks many other waves.
The 20th century saw dramatic improvements in observation technologies. Today’s scientists observe stars galaxies, and other celestial objects in the full electromagnetic spectrum by sending up planes, balloons, rockets, spacecraft, and satellites carrying equipment that can capture the more elusive wavelengths such as gamma rays, x-rays, and ultraviolet rays. Orbiting observatories have truly expanded our astronomical senses. Space-based observatories can see into radiation wavelengths that Earth-based instruments find difficult to image. These include far-infrared wavelengths, which reveal the secrets of relatively cool objects such as planets, comets, and infant stars. Space-based observatories also can examine high-energy processes in the nuclei of galaxies or near black holes.
Our atmosphere interferes with light coming from distant astronomical objects, so most observatories sit on carefully selected mountaintops. High altitude helps eliminate atmospheric distortions, the air here is thinner and more transparent, and these mountaintop experience smooth airflow, creating stable skies for steady view ing. Because of the exacting criteria and expense of establishing ground based observatories, international astronomical communities cooperate in their administration. Hawaii’s Mauna Kea Observatory, for example, contains more than a dozen telescopes operated by more than ten countries.
THE HUBBLE SPACE TELESCOPE orbits 375 miles above Earth. huge mirrors, cameras, and spectrographs seek and sometimes distant glimmers from the big bang. Computer-controlled adap o optics help prevent distortions. Spectrographs taken from the ble can also distinguish different gases by color
THE JAMES WEBB SPACE TELESCOPE will replace the Hubble A longer instrument (72 feet, while Hubble is 43), it will explore both the visible and infrared spectra of the universe from a vantage point a million miles from Earth. It is named for NASA’s second administrator, a key leader of the space program in the 1960s
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