HD1 (galaxy)
HD1 is a newly proposed galaxy candidate located approximately 13.5 billion light years from Earth, making it one of the farthest celestial objects detected to date. Announced in April 2022 by a team of astronomers from the University of Tokyo and the Center for Astrophysics—Harvard & Smithsonian, HD1 is believed to have formed just 300 million years after the Big Bang. Its distinctive red appearance indicates a significant redshift, suggesting that it is moving away from Earth. Notably active, HD1 is thought to produce over 100 stars per year, a rate much higher than typical galaxies, which raises the possibility that it may harbor Population III stars—the first stars in the universe.
Some scientists speculate that HD1 could actually be a supermassive black hole, emitting significant ultraviolet radiation rather than a traditional galaxy. The findings were made possible through data collected from various telescopes, including the Subaru and VISTA telescopes, as well as the Spitzer Space Telescope. Located in the Sextans constellation, HD1 exemplifies the ongoing efforts to understand the early universe and the conditions that led to the formation of galaxies and stars. Future observations, particularly with the James Webb Space Telescope, may further illuminate the characteristics of HD1 and enhance our understanding of cosmic evolution.
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HD1 Galaxy
HD1 is a newly discovered proposed galaxy approximately 13.5 billion light years from Earth. The finding was announced in April 2022 by astronomers at the University of Tokyo and researchers at the Center for Astrophysics—Harvard & Smithsonian. Using data from telescopes in various global locations and in space, scientists concluded that HD1 formed just three hundred million years after the Big Bang. The red, glowing body is believed to be the farthest galaxy candidate ever detected. The red color denotes “redshift,” which is defined light waves moving toward the red end of the spectrum, and occurs when a celestial object, such as a galaxy, moves farther away from Earth. Yuichi Harikane, a famous astronomer and one of the discoverers of the HD1 galaxy candidate, said that HD1 was found after combing through seven hundred thousand other astronomical objects over twelve hundred hours of observation time.
Background
To the surprise of astronomers, HD1 is quite active, with researchers pointing to calculations indicating that it can produce an astounding one hundred stars per year. Astronomers theorize that in HD1 are Population III Stars, which are the very first stars to be formed in the universe. Some astronomers theorize that HD1 is not a galaxy but a place where a supermassive black hole is emitting ultraviolet radiation. Astronomers hope that the James Webb Space Telescope, launched in 2021, will enable them to further discern the characteristics of HD1 as well as the birth and materialization of the universe itself.
Overview
The HD1 galaxy candidate was announced by a team of international astronomers in April 2022. It is in the Sextans constellation—one of the eighty-eight constellations acknowledged by the International Astronomical Union (IAU). The Sextans constellation is found between the constellations Crater, Hydra, and Leo and is part of the Hercules constellation group. It is one of fifteen equatorial constellations and the forty-seventh largest. The Sextans was conceived in 1687 by Polish astronomer Johannes Hevelius, who named the constellation after the tool he utilized to measure the position of the stars. Hevelius invented several constellations, many of which are still recognized by the IAU such as Lacerta, Lynx, and Scutum. Scientists have confirmed that at least five stars with exoplanets are in the Sextans constellation, and a red dwarf star found there is only 14.8 light years from Earth.
HD1 was discovered using the Subaru and UK Infrared Telescopes in Hawaii; the VISTA Telescope in Chile; and the Spitzer Space Telescope. At the time, a galaxy by the name of GN-z11 was thought to be the farthest observed by humans. However, upon closer inspection, astronomers discovered that HD1 was even farther away by one hundred million light years. Scientists confirmed their findings using the Atacama Large Millimeter/submillimeter Array (ALMA) located in Chile’s Atacama Desert.
Initially, researchers thought HD1 was a starburst galaxy. These galaxies are those that create an enormous number of star formations along with an immense amount of infrared light. Astronomers believe that starburst galaxies formed when galaxies either collided or nearly collided. Some extremely active starburst galaxies can create thousands of stars every year, as contrasted with our own Milky Way galaxy that creates only about seven stars per year. Scientists have pointed out that our early universe was rife with starburst galaxies. They believe that, in the first billion years of its existence, the universe was in a growth-spurt phase and generated from 60 to 90 percent of its stars in these galaxies. Such phases can last for about ten million to one hundred million years. Other known starburst galaxies include Messier 82 (M82), the Antennae Galaxies, and the Sculptor Galaxy.
However, scientific calculations put the number of stars created by the HD1 galaxy candidate at more than one hundred per year, which is more than ten times what is expected from a typical starburst galaxy. Researchers theorize that HD1 may very well be the home of Population III stars, which are supermassive, radiant, and extremely hot stars composed of mainly helium and hydrogen but also contain trace amounts of lithium or beryllium. These supermassive stars are likely the very first stars of the universe. Team scientists also theorize that HD1 might be a supermassive black hole that has roughly one-hundred million times the mass of the sun. Since a supermassive black hole pulls in incalculable amounts of gas and emits plumes of extremely hot plasma that are visible using space telescopes, scientists wondered if what they were seeing was a super massive black hole, and not a galaxy. If HD1 is a supermassive black hole, it would be the oldest ever discovered, having most likely formed several hundred million years after the Big Bang. It is important to understand that when astronomers study celestial objects such as stars and galaxies that lie hundreds of millions or even tens of billions of light years away, they are looking back in time. HD1 is 13.5 billion light years away from Earth, which means that scientists are studying the galaxy as it appeared at that time, only three hundred million years after the Big Bang; therefore, it is possible that researchers are studying an object that no longer exists.
Bibliography
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Bryner, Jeanna. “Astronomers Just Discovered the Farthest Object in the Known Universe—But What Is It?” Live Science, 7 Apr. 2022, www.livescience.com/farthest-astronomical-object-ever-seen. Accessed 17 Aug. 2022.
Byrd, Deborah. “Starburst Galaxies Flourished in Early Universe.” EarthSky, 4 Apr. 2022, earthsky.org/space/starburst-galaxies-flourished-in-the-early-universe/. Accessed 17 Aug. 2022.
Carter, Jamie. “Meet HD1, the New Most Distant Galaxy Found 13.5 Billion Years Back in Time and Close to the ‘Big Bang.’” Forbes, 7 Apr. 2022, www.forbes.com/sites/jamiecartereurope/2022/04/07/meet-hd1-the-new-most-distant-galaxy-found-135-billion-years-back-in-time-and-close-to-the-big-bang/?sh=afe31f834f8e. Accessed 17 Aug. 2022.
Whitt, Kelly Kizer. “Most Distant Galaxy Yet Discovered.” EarthSky, 10 Apr. 2022, earthsky.org/space/most-distant-galaxy-discovered-hd1/. Accessed 17 Aug. 2022.