Featured Image: A stately spiral galaxy called M106. Hubble Space Telescope/ NASA.
By Wes O’Donnell, Managing Editor, In Space News.
The Big Bang, the prevailing cosmological model for the beginning of our universe, is a relatively recent explanation for why the galaxies seem to be running away from each other.
Imagine you’re standing on a sidewalk as an ambulance passes with its sirens on. As the ambulance approaches you, its sirens have a higher pitch in sound. But when the ambulance passes, the siren’s pitch becomes lower. If you’re riding inside the ambulance, the pitch sounds constant and unchanging. This is because you are moving along with the source of the sound.
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This familiar change in pitch happens because, as an object approaches, its sound waves are compressed. As it moves away, its sound waves are stretched apart. In other words: higher frequency as it approaches, lower frequency as it moves away.
This phenomenon is known as the Doppler Effect and it applies to light waves as well as sound. Color is to light what pitch is to sound. Compressed light waves, perhaps from an object coming toward us, are blue or “blue-shifted.” Stretched out light waves, from objects moving away from us, appear red, or “red-shifted.”
This phenomenon is precisely what Vesto Slipher, Milton L. Humason and Edwin Hubble discovered when they looked at distant galaxies in the late 1920s. Curiously, they noted that nearly all of the observed galaxies were red-shifted, indicating that they all seemed to be receding from Earth with velocities that increased in proportion to their distance from our planet. That relationship is now known as Hubble’s Law.
Their insight led to the idea that the universe is expanding and the modern Big Bang model that we have today.
Space Shuttle Discovery Launches a Telescope Named Hubble
Launched on April 24, 1990, from the space shuttle Discovery (STS-31), the Hubble Space Telescope boasts a 94.5-inch mirror, almost as big as the mirror on the telescope that Hubble used at Mount Wilson in Los Angeles County, California, in the 1920s.
In its 29 years of operation, the Hubble telescope has made more than 1.3 million observations and transmits about 150 gigabits of raw science data every week.
The telescope still has the power to inspire awe with its images. Below is a sampling of some of InSpaceNews staff favorite images:
Above: This breathtaking picture is the star Eta Carinae. These blue streaks are created when the star’s light rays poke through the dust clumps scattered along the bubble’s surface. The star, the largest member of a double-star system, has been prone to violent outbursts, including an episode in the 1840s during which ejected material formed the bipolar bubbles seen here. Courtesy Hubble Space Telescope/ NASA
Above: This barred-spiral galaxy is named NGC 1015 and is about 67,000 light-years across. Courtesy Hubble Space Telescope/ NASA
Above: This Hubble image is “the Ghost of Cassiopeia,” officially known as IC 63, located 550 lightyears away in the constellation Cassiopeia the Queen. The ghostly glow is hydrogen that is being bombarded with ultraviolet radiation from the nearby, blue-giant star Gamma Cassiopeiae (not visible here). Courtesy Hubble Space Telescope/ NASA
Above: In 1054 A.D., Chinese astronomers recorded a bright explosion in the sky. What they were seeing was the Crab supernova and this image is a closeup of its remnants, now called the Crab Nebula. Courtesy Hubble Space Telescope/ NASA
Above: The iconic Horsehead Nebula is a favorite for amateur astronomers. In this magnificent close-up, Hubble captures incredibly fine detail of the hydrogen, helium, and dust that make up the structure. Courtesy Hubble Space Telescope/ NASA
Above: A stately spiral galaxy called M106, this single picture contains billions of stars and perhaps countless planets. Large amounts of gas from the galaxy are thought to be falling into and fueling a supermassive black hole in the nucleus. Courtesy Hubble Space Telescope/ NASA