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Hubble randomly discovers a new galaxy in the cosmic neighborhood

January 31, 2019

(Nanower News) Astronomers who use the NASA / ESA Hubble Space Telescope to study some of the oldest and weakest stars of the globular cluster NGC 6752 have made an unexpected finding. They discovered a dwarf galaxy in our cosmic backyard, just 30 million light years away. The finding was reported in the magazine Monthly announcements from the Royal Astronomical Society: Letters ("The great HST program on NGC 6752. I. Serendipito discovery of a dwarf galaxy in the background").

An international team of astronomers recently used the NASA / ESA Hubble Space Telescope to study white dwarf stars within the globular cluster NGC 6752. The purpose of their observations was to use these stars to measure the age of the globular group, but in the process it made an unexpected discovery .Accidentally discovered Galaxy Bedin IThis image, taken with the advanced Hubble aging camera, shows a component of the globular cluster NGC 6752. Behind the bright stars of the group there is a dense collection of weaker stars, a previously unknown dwarf sphere galaxy. This galaxy, nicknamed Bedin 1, is about 30 million light years away from Earth. (Image: ESA / Hubble, NASA, Bedin et al.)

In the outer fringes of the area observed with the Hubble advanced camera for surveys, a compact star collection was visible. After a careful analysis of its brightness and temperature, astronomers concluded that these stars did not belong to the cluster, which is part of the Milky Way, but are far more distant millions of light years away.

Our recently discovered cosmic neighbor, called Bedin 1 by astronomers, is a modest and elongated galaxy. Measure only around 3000 light years in its greatest extent – a fraction of the size of the Milky Way. Not only is it small, but it is also very weak. These properties led astronomers to classify it as a dwarf sphere galaxy.

The spherical pineapple galaxies are defined by their small size, low luminosity, lack of dust and ancient star populations. [1]. It is already known that there are 36 galaxies of this type in the Local Group of Galaxies, of which 22 are satellite galaxies of the Milky Way.

While pineapple spheroid galaxies are not uncommon, Bedin 1 has some remarkable characteristics. Not only is it one of the few dwarf spheroids that have a well-established distance, but it is also very isolated. It is about 30 million light years from the Milky Way and 2 million light-years away from the nearest plausible host of NGC 6744. This makes it possible for the smallest dwarf galaxy discovered to date.

From the properties of their stars, astronomers could infer that the galaxy has about 13 billion years, almost as old as the Universe. Due to its isolation – which resulted in almost no interaction with other galaxies – and its age, Bedin 1 is the astronomical equivalent of a living fossil of the early Universe.

The discovery of Bedin 1 was a real serendipite encounter. Very few Hubble images allow you to see such weak objects and that only cover a small area of ​​the sky. Future telescopes with a large field of vision, such as the WFIRST telescope, will have cameras that cover a much larger area of ​​the sky and can find many more of these galactic neighbors. Notes [1] While they are similar to the elliptical galaxies in terms of pineapple appearance and properties, the spherical dwarf galaxies are generally approximately spherical and have a lower luminosity.

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