Bright, blue-white stars of the open cluster BSDL 2757 pierce through the rusty-red tones of gas and dust clouds in this
Hubble Space Telescope image. Hubble captured the scene as part of a study looking at how dust in the Large Magellanic Cloud obscures ultraviolet light in four different star-forming regions of this nearby, irregular galaxy. The researchers studied growing, early-stage stars that are still accumulating mass from the clouds that envelop them. As gas and dust spirals toward a budding, young star, it releases ultraviolet light. By analyzing how this light interacts with dust, astronomers can better understand the dust’s properties in different environments.
The colors blue, green, and orange in this image represent their respective colors in the visible light spectrum. The color red represents light in the near-infrared part of the spectrum.
Image credit: NASA, ESA, and L. Bianchi (Johns Hopkins University); Processing: G. Kober (NASA/Catholic University of America)
For Hubble’s Star Clusters page, visit: www.nasa.gov/content/discoveries-hubbles-star-clusters
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The Hubble Space Telescope has provided strong evidence that white dwarfs, the burned-out relics of stars, are given a "kick" when they form. The idea that young white dwarfs are born with a kick was suggested decades ago to explain why there were so few of them in open star clusters.
Hubble's sharp vision uncovered speedy white dwarfs in the ancient globular star cluster NGC 6397, a dense swarm of hundreds of thousands of stars.
Before the stars burned out to become white dwarfs, they were among the most massive stars in NGC 6397. Because massive stars are thought to gather at a globular cluster's core, astronomers assumed that most newly minted white dwarfs dwelled near the center. Hubble, however, discovered young white dwarfs residing at the edge of NGC 6397, which is about 11.5 billion years old.
To explain this, some researchers suggested that white dwarfs propel themselves by ejecting mass, like rockets do. Before stars evolve into white dwarfs, they swell up and become red giants. Red giant stars lose about half their mass by shedding it into space. If more of this mass is ejected in one direction, it could propel the emerging white dwarf through space, just as exhaust from a rocket engine thrusts the rocket from the launch pad.
Globular clusters continue to sort out member stars according to their mass. Heavier stars slow down and sink to the cluster's core, while lighter stars pick up speed and move across the cluster to its outskirts.
For more information, and to see where astronomers found white dwarfs in this Hubble image, visit: hubblesite.org/contents/news-releases/2007/news-2007-42.html
Credit: NASA, ESA, and H. Richer (University of British Columbia)
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This glittering gathering of stars is Pismis 26, a globular star cluster located about 23,000 light-years away. Many thousands of stars gleam brightly against the black backdrop of the image, with some brighter red and blue stars located along the outskirts of the cluster. The Armenian astronomer Paris Pismis first discovered the cluster in 1959 at the Tonantzintla Observatory in Mexico, granting it the dual name Tonantzintla 2 (Ton2).
Pismis 26 is located in the constellation Scorpius near the galactic bulge, which is an area near the center of our galaxy that holds a dense, spheroidal grouping of stars that surrounds a black hole. Due to its location within the dust-heavy bulge, a process called “reddening” occurs, where dust scatters shorter wavelength blue light while longer wavelength red light passes through. Reddening distorts the apparent color of cosmic objects. Globular clusters are groups of stars held together by mutual gravitational attraction. They contain thousands of tightly packed stars and appear almost spherical in shape. Astronomers used the Hubble Space Telescope to study visible and infrared light from Pismis 26 to determine the cluster’s reddening, age, and metallicity.
The stars of Pismis 26 have high metallicity, meaning they contain a high fraction of elements heavier than hydrogen and helium, the most abundant elements in the universe. Specifically, the stars are rich in the element nitrogen, which is typical of stars in bulge clusters and has led scientists to believe that populations of differently-aged stars are present in the cluster. Pismis 26 has also likely lost a sizable portion of its mass over time due to a gravitational force called the strong inner galaxy tidal field, which the inner galaxy exerts on star clusters in the galactic bulge, causing their outer layers to pull away. Researchers estimate the age of the cluster to be 12 billion years old.
Credit: NASA, ESA and R. Cohen (Rutgers the State University of New Jersey); Processing: Gladys Kober (NASA/Catholic University of America)
For Hubble’s Star Clusters page, visit: www.nasa.gov/content/discoveries-hubbles-star-clusters
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French astronomer Charles Messier discovered the globular cluster M3 in 1764, mistaking it for a nebula without any stars. This misunderstanding of M3’s nature was corrected in 1784 when William Herschel was able to resolve the cluster’s individual stars. Today it is known to contain over 500,000 stars.
M3 is notable for containing more variable stars than any other known cluster. As their name implies, the brightness of a variable star fluctuates with time. For some variable stars, their period relates to their intrinsic luminosity, so astronomers can use those stars’ brightness fluctuations to estimate their distances. This makes them extremely useful for measuring the general distances to the clusters or even galaxies in which they reside. M3 contains at least 274 variable stars.
For more information, visit: www.nasa.gov/feature/goddard/2017/messier-3
Credit: NASA, ESA, STScI, and A. Sarajedini (University of Florida)
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Open star cluster NGC 330 lies around 180,000 light-years away inside the Small Magellanic Cloud. The cluster — which is in the constellation Tucana (The Toucan) — contains a multitude of stars, many of which are scattered across this striking Hubble Space Telescope image. One interesting object in this image is the very small star cluster in the lower left corner of the image, surrounded by a nebula of ionized hydrogen (red) and dust (blue). Named GALFOR 1, the cluster was discovered in 2018 in Hubble's archival data, which was used to produce this image. Scientists are curious whether the nebula around this star cluster contains a bow shock, a crescent-shaped shock wave created when streams of gas collide.
Hubble observations of this cluster have been used to investigate why stars in star clusters appear to evolve differently from stars elsewhere, and to determine how large stars can be before they become doomed to end their lives in cataclysmic supernova explosions.
Credit: ESA/Hubble & NASA, J. Kalirai, A. Milone
For more information, visit: esahubble.org/images/potw2126a/
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