Though many cosmic phenomena are visible to us, much of the universe is hidden from view, obscured by gas and dust. After the serendipitous discovery of radio waves coming from the Milky Way’s center in the 1930s, scientists realized radio waves, which have a longer wavelength than visible light, could reveal many aspects of cosmic phenomena not visible in other wavelengths.
For more than 60 years, the National Science Foundation (NSF) has invested in state-of-the-art facilities to advance the field of radio astronomy, starting with the nation’s first astronomical observatory—the National Radio Astronomy Observatory (NRAO). Today, NSF supports radio telescopes from West Virginia to the Chilean Andes.
The following images offer a virtual tour of some of those telescopes and their discoveries.
Pictured: The Karl G. Jansky Very Large Array in New Mexico.
This image of the center of the Milky Way was created from multiple VLA observations. The circular rings in the center-left of the image are supernova remnants caught in the strong magnetic field of the galaxy’s core.
With the help of supercomputers that process large amounts of spectral data—a first for radio astronomy—the VLA is able to produce images of cosmic objects and events.
Radio waves from cosmic sources are much fainter than noisier radio waves closer to home. Hence, radio telescopes are typically located in more remote areas to minimize the homegrown noise.
Astronomers often observe microscopic dust grains—which can coalesce to form rocky planets—around protostars, or very young stars gathering mass from their parent molecular cloud. However, the interstellar particles found in this filament were 100 to 1,000 times larger than particles typically found in star-forming regions, leading astronomers to theorize the larger-than-expected particles could help spur planet formation.
ALMA’s array of 66 high-precision antennas act as a single telescope. Its sensitivity and high resolution—10 times sharper than the Hubble Space Telescope—are ideal for observing the “cool” universe, or the regions of gas and dust around stars. In this way, observations by ALMA and other radio telescopes complement those of optical telescopes.
Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) to observe NGC 1068 discovered clouds of gas and dust being expelled from the black hole’s accretion disk, where dense material spins furiously around a black hole, sometimes reaching speeds of 400 to 800 kilometers per second. Eventually the black hole pulls material from the accretion disk into it, raising temperatures which emits a glow. While some material is pulled into the body, however, other material is expelled and, in some cases, forms a doughnut-shaped cloud of gas and dust, called a torus, around the entire system, concealing it.
The observatory’s long history is punctuated with discoveries, from the detection of millisecond pulsars—neutron stars that rotate several hundred times a second—to the presence of hydrocarbon lakes on Saturn’s moon Titan.
To see what lay beneath the Venusian clouds, astronomers at Arecibo sent radar signals to Venus. The signals passed through the atmospheres of both Earth and Venus, hit upon Venus’ surface and bounced back to the Green Bank Telescope. This transmitter-receiver technique revealed a planet characterized by mountains, ridges, craters and other surface features.