Friday Jan. 1, 2021’s Smile of the Day: Edwin Hubble
On this Day:
Astronomer Edwin Hubble formally announced the existence of other galactic systems at a meeting of the American Astronomical Society in 1924.
Edwin Hubble, for whom the Hubble Space Telescope is named, was one of the leading astronomers of the twentieth century. His discovery in the 1920s that countless galaxies exist beyond our own Milky Way galaxy revolutionized our understanding of the universe and our place within it.
Hubble, a tall and athletic man who excelled at sports and even coached high school basketball for a short while, started his professional science career during one of the most exciting eras of astronomy. It was 1919, just a few years after Albert Einstein published his theory of general relativity, and bold, new ideas about the universe were fermenting. Hubble was offered a staff position at the Mount Wilson Observatory, which housed the newly commissioned 100-inch Hooker telescope, then the largest telescope in the world. Hubble, it seemed, had the universe placed in his lap.
Most astronomers of Hubble’s day thought that all of the universe — the planets, the stars seen with the naked eye and with powerful telescopes, and fuzzy objects called nebulae — was contained within the Milky Way galaxy. Our galaxy, it was thought, was synonymous with the universe.
In 1923 Hubble trained the Hooker telescope on a hazy patch of sky called the Andromeda Nebula. He found that it contained stars just like the ones in our galaxy, only dimmer. One star he saw was a Cepheid variable, a type of star with a known, varying brightness that can be used to measure distances. From this Hubble deduced that the Andromeda Nebula was not a nearby star cluster but rather an entire other galaxy, now called the Andromeda galaxy.
In the following years he made similar discoveries with other nebulae. By the end of the 1920s, most astronomers were convinced that our Milky Way galaxy was but one of millions in the universe. This was a shift in thought as profound as understanding the world was round and that it revolved around the sun.
Hubble then went one step further. By the end of that decade he had discovered enough galaxies to compare to each other. He created a system for classifying galaxies into ellipticals, spirals and barred spirals — a system called the Hubble tuning fork diagram, used today in an evolved form.
But the most astonishing discovery Hubble made resulted from his study of the spectra of 46 galaxies, and in particular of the Doppler velocities of those galaxies relative to our own Milky Way galaxy. What Hubble found was that the farther apart galaxies are from each other, the faster they move away from each other. Based on this observation, Hubble concluded that the universe expands uniformly. Several scientists had also posed this theory based on Einstein’s General Relativity, but Hubble’s data, published in 1929, helped convince the scientific community.
Hubble and his colleague at Mt. Wilson, Milton Humason (who started as a mule driver during the construction of the observatory, then janitor, then night assistant), estimated the expansion rate of the universe to be 500 kilometers per second per megaparsec. (A megaparsec, or a million parsecs, is a distance equal to about 3.26 million light-years; so a galaxy two megaparsecs away is receding from us twice as fast as a galaxy only one megaparsec away.) This estimate is called the Hubble Constant, and scientists have been fine-tuning it ever since.
The Hubble Space Telescope was launched in 1990, one of its major goals being to pin down the Hubble Constant. In 2001, a team studying supernovae with Hubble, along with ground-based optical telescopes, established a rate of 72 ± 8 km/sec/Mpc. In 2006, a team studying the cosmic microwave background with NASA’s WMAP satellite tweaked this measurement to 70 km/sec/Mpc. Hubble, the telescope, also helped discover that not only is the universe expanding, the expansion is accelerating. The mysterious force causing this acceleration is dubbed dark energy.
Hubble was born on November 20, 1889, in Marshfield, Missouri, and moved to Wheaton, Illinois, before his first birthday. He studied mathematics and astronomy at the University of Chicago and earned a bachelor of science degree in 1910. He was one of the first Rhodes Scholars at Oxford University, where he studied law. After serving briefly in World War I, he returned to the University of Chicago and earned his doctorate degree in 1917. After a long career entirely at Mt. Wilson Observatory, he died of a heart attack on September 28, 1953, in San Marino, California. As with the telescope that bears his name, Edwin Hubble transformed our understanding of the universe. His spirit of discovery lives on today in the Hubble Space Telescope (per Nasa.gov).
First, a Story:
My daughter asked me how to spell “Hubble,” like the Hubble Space telescope. I wasn’t listening, so I said “Sorry, what was the question?” She said: “Two Bs or not two Bs, that is the question.”
Second, a Song:
The Hubble Space Telescope has been staring out into deep space since 1990.
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, well known both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA’s Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.
Hubble features a 2.4-meter (7.9 ft) mirror, and its four main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble’s orbit outside the distortion of Earth’s atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of the most detailed visible light images, allowing a deep view into space. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe.
The Hubble telescope was built by the United States space agency NASA with contributions from the European Space Agency. The Space Telescope Science Institute (STScI) selects Hubble’s targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft. Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the 1986 Challenger disaster. It was finally launched by Space Shuttle Discovery in 1990, but its main mirror had been ground incorrectly, resulting in spherical aberration that compromised the telescope’s capabilities. The optics were corrected to their intended quality by a servicing mission in 1993.
Hubble is the only telescope designed to be maintained in space by astronauts. Five Space Shuttle missions have repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments. The fifth mission was initially canceled on safety grounds following the Columbia disaster (2003), but NASA administrator Michael D. Griffin approved the fifth servicing mission which was completed in 2009. The telescope was still operating as of April 24, 2020, its 30th anniversary, and could last until 2030–2040. One successor to the Hubble telescope is the James Webb Space Telescope (JWST) which is scheduled to be launched in late 2021 (per Wikipedia).
In celebration of its 25th Anniversary, NPR’s Skunk Bear wrote a parody of Iggy Azalea’s song “Trouble.” and named it “Hubble: The Song”. I hope you enjoy it!
Thought for the Day:
“Equipped with his five senses, man explores the universe around him and calls the adventure Science.” – Edwin Powell Hubble
Have a great day!
© 2021 David J. Bilinsky and Colleen E. Bilinsky