September 18, 2021

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Hubble discovered galactic fossils.  These are ultra-light dwarf galaxies

Hubble discovered galactic fossils. These are ultra-light dwarf galaxies

The Hubble Space Telescope has tracked the so-called UFD, or ultra-faint dwarf galaxies. Because of their low brightness and presumably high dark matter content, astronomers refer to them as candidates for fossils of the early universe.

Scientists once again used the (almost) reliable Hubble Space Telescope, allowing them to find it Three previously unknown ultra-faint dwarf galaxies. Located near a spiral galaxy The band is called NGC 253. It is located about 11.6 million light-years from Earth.

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The UFDs observed by astronomers are among the faintest systems so far observed outside the Local Group of Galaxies. This group consists of dozens of galaxies that span about 10 million light-years. As you can easily guess, this group also includes our own Milky Way.

The PISCeS (Panoramic Photogrammetry Survey of Centaurs and Sculptor), whose main objective is the search for UFDs, played a major role in finding galactic fossils. These so-called ultra-light dwarf galaxies will form at the beginning of the universe. Five galaxies were named primary UFD candidates, but two were eventually eliminated. In this way, three galaxies remained “on the battlefield”.

Extremely faint dwarf galaxies are remnants of the early universe

Among its distinguishing features, three elements can be mentioned: low brightness, slight chemical contrast and high dark matter content. According to astronomers, they formed about 12 billion years ago, which is why almost 100 percent of their stars were born in the early stages of the universe’s existence.

The trio was named: Scl-MM-dw3And Scl-MM-dw4 And Scl-MMdw5. The first is the smallest of the three, located about 11.34 million light-years from Earth and 264,000 light-years from NGC 253. Its stellar mass is estimated at 110,000 solar masses. Scl-MM-dw4 has a similar size, but a larger radius (613 light-years compared to 362 light-years). It is 13.37 million light years from Earth and 280,000 light years from NGC 253.

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On the other hand, Scl-MM-dw5 is the largest and most massive. It is located 12.7 million light-years from our planet, has a radius of 1,167 light-years and a mass of 140,000 solar masses. This ultra-light dwarf galaxy is located about 313,000 light-years from NGC 253. Scientists estimate that the brightness of the three ranges from -75 to -7.24, making them the darkest galaxies found outside the Local Group.

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