Unlike the dragon-filled House of the Dragon show, the bright heat from this celestial monster spotted by the Hubble Space Telescope is nothing to fear. In fact, it is a very useful tool to help measure the expansion of the universe.
Spiral galaxy UGC 9391 is located in the constellation Draco (dragon), a long serpentine patch of sky that never appears in the southern sky due to its location near the north pole. Astronomers looked into this patch of sky between Ursa Major and Ursa Minor because the light from some of the stars in the galaxy UGC 9391 is a special beacon. A recently released image from the Hubble Space Telescope shows UGC 9391 against a backdrop of ultra-distant galaxies and a description of the image from September 30th. (will open in a new tab) calls it “lonely”.
What he lacks in society, he makes up for in character. According to the description of the European Space Agency (ESA), which operates the famous observatory with NASA, the galaxy UGC 9391 is filled with two amazing light sources: Cepheid variable stars and a Type IA supernova. They help astronomers determine distances in space.
(Image credit: ESA/Hubble and NASA, A. Riess et al.)
“This image is from a set of Hubble observations that astronomers used to build the Cosmic Distance Ladder, a set of related measurements that allow astronomers to determine how far away the most distant astronomical objects are,” the ESA wrote in the description.
Variable stars are stars with varying brightness. Cepheids are of a type called intrinsic, which means it’s not like, say, an object orbiting a star and blocking its light from time to time. Rather, these strange stars themselves change size and brightness, and this is a well-studied phenomenon. As such, their brightness is a reliable tool for determining how far away a galaxy is.
The galaxy UGC 9391 also showed a peculiar supernova called Type Ia, where a stellar corpse called a white dwarf is feeding like a zombie on its living partner star. The binary continues to be stressed by the consuming white star until the undead accumulate a mass of about one and a half suns. These situations go supernova almost equally across the board, so again astronomers can use the event’s brightness as a reliable guide to the distance to the galaxy.
UGC 9391 is clearly visible from 130 million light-years away using the Hubble Wide Field Camera 3. Hubble did not launch it in 1990. Rather, the STS-125 service mission of NASA’s Atlantis spacecraft added it to space. observatory in 2009. The wide-angle camera 3 can study celestial objects in the electromagnetic spectrum from ultraviolet to visible light and near infrared.
Thanks to the Hubble Space Telescope, astronomers can study a phenomenon that also bears the name of astronomer Edwin Hubble: the outward expansion rate of the universe, also called the Hubble constant. And this galaxy in the northern sky dragon helped light the way.
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