2.01.2023
NGC 6956 isn't just pretty to look at, it is an important measure of the universe's expansion.
This new Hubble Space Telescope photo of the spiral galaxy NGC 6956 was released on Dec. 15, 2022.(Image credit: NASA, ESA, and D. Jones (University of California – Santa Cruz); Processing: Gladys Kober (NASA/Catholic University of America))
While the James Webb Space Telescope is getting a lot of press lately, its predecessor the Hubble Space Telescope continues to impress; this time of the galaxy NGC 6956, a near-perfect example of a barred galaxy located about 214 million light-years away from Earth.
Barred galaxies, which get their name from the very prominent "bar" of starsthat cut across the galactic nucleus, are among the most common type of galaxies in the known universe, making up an estimated 70% of all galaxies(opens in new tab). Bar structures are also far more common in galaxies with active galactic nuclei, as gas and other material is fed in toward the galactic core along these bars.
This process helps to eventually destabilize the bar(opens in new tab), however, as the more mass that is funneled to the galactic core, the more unstable the bar becomes, eventually softening the bar into the more traditional spiral formation — like that of NGC 2985(opens in new tab) — that most people think of when thinking of a spiral galaxy.
The full new view of the barred spiral galaxy NGC 6956 unveiled on Dec. 15, 2022 by NASA's Hubble Space Telescope team. The galaxy is 214 million light-years from Earth in the constellation Delphinus. (Image credit: NASA, ESA, and D. Jones (University of California – Santa Cruz); Processing: Gladys Kober (NASA/Catholic University of America))
According to a image description by NASA(opens in new tab), this most recent photo of NGC 6956 was to look at Cepheid variable stars, which are stars whose luminosity cycles between bright and dim at regular intervals. This periods of brightening and dimming are directly related to a star's actual brightness, we are able to calculate these variations in apparent brightness to the stars actual brightness, which allows us to determine their distance from us.
This is a crucial way for astronomers to determine the distance of extragalactic objects like NGC 6956, since there are few other ways to do so that we currently know of. There are other interesting features of NGC 6956, like a visible Type Ia supernova, which is the product of a white dwarf star exploding as a result of accreting matter from a companion star.
This type of supernova is another key method for determining the distance of far-away galaxies, since astronomers are able to measure how quickly a supernova dims to help measure its distance from Earth. And while filling in the galactic map in an accurate manner is useful in itself, repeated measurements of the distance of these extragalactic objects is an important tool for understanding the current rate of expansion in the universe.
Quelle: SC
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Hubble Space Telescope delivers holiday sparkle in new image
The red backdrop represents interstellar dust from a nearby dwarf galaxy.
This Hubble Space Telescope image shows open cluster BSDL 2757, located in the dwarf galaxy the Large Magellanic Cloud. (Image credit: NASA, ESA, and L. Bianchi (Johns Hopkins University); Processing: G. Kober (NASA/Catholic University of America))
Images from the Hubble Space Telescope can deliver New Year cheer with science.
One such case is a new image from the 32-year old observatory, published on Dec. 1. Here, the Hubble Space Telescope sees the quintessential colors of the holiday season, as bright blue-white stars shine against dusty swaths shaded red.
These stars are located outside the Milky Way, in a patch of sky located within a nearby galaxy called the Large Magellanic Cloud (LMC). As the name suggests, it looks like a round smudge in the southern sky. But in fact, this celestial smear is an irregularly-shaped, small satellite galaxy of the Milky Way. It is located roughly 150,000 light years(opens in new tab) away from Earth. But despite this distance, Hubble is able to make out fantastic details.
This image is the full view of the open star cluster BSDL 2757 in the dwarf galaxy Large Magellanic Cloud near our own Milky Way as seen by the Hubble Space Telescope. (Image credit: NASA, ESA, and L. Bianchi (Johns Hopkins University); Processing: G. Kober (NASA/Catholic University of America))
Take for instance, the glittering stars Hubble can see there. They belong to a particular region within LMC, called BSDL 2757. It is an open cluster, a group of stars loosely held together by their mutual gravity. Astronomers like to study star clusters because they hold information about how stars – the most basic units of the cosmos – come to exist. Open clusters are particularly interesting because the hundreds of stars within one cluster likely share the same origin(opens in new tab). That is to say, they evolved from the same molecular cloud of star stuff.
The blue, green and orange colors seen here are optical light, according to Hubble Space Telescope officials in the image description(opens in new tab) published last week. Dozens of bright stars shine in these shades against what looks like a rust-colored canvas.
But the red regions are not optical light. Rather, they represent information that Hubble gathered in infrared wavelengths of light. These are just beyond what human eyes can see. Their value is that they showcase sources of heat. In this case, the red represents interstellar dust wafting around in the open cluster.
Astronomers are studying open cluster BSDL 2757 to investigate stellar evolution.
"The researchers studied growing, early-stage stars that are still accumulating mass from the clouds that envelop them," NASA officials write in the Hubble image description.
"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."
Hubble's successor is the James Webb Space Telescope (JWST or Webb). The observatory launched Christmas Day last year, and its team released its first official science data this past summer. JWST is specially designed to study the universe's infrared wavelengths, and can offer scientists more data on the material that appears here as the red backdrop.
Quelle: SC