Hubble observes a small galaxy with a big heart

ESO 495-21, a tiny galaxy with a big heart, is nestled in this field of bright stars in the foreground. ESO 495-21 may only be 3,000 light-years away, but this does not prevent the galaxy from furiously forming a large number of stars. It can also host a supermassive black hole; this is unusual for a galaxy of this size and can provide intriguing insights into galaxy formation and evolution.

Located about 30 million light-years away from the constellation Pyxis (The Compass), ESO 495-21 is a star-shaped dwarf galaxy, which means that it is small in size, but in flames with a rapid formation of stars. Star-shaped galaxies form stars at an exceptionally high rate, creating stellate newborns up to 1000 times faster than the Milky Way.

Hubble has studied several times the activity of ESO 495-21. The space telescope has explored the multiple clusters of super stars in the galaxy, very dense regions dating back only a few million years and full of massive stars. These spectacular areas can have a huge impact on host galaxies. Their study allows astronomers to investigate the early stages of their evolution, with the goal of understanding how massive stars form and change across the Universe.

In addition to hosting cosmic fireworks that are star clusters, ESO 495-21 can also house a supermassive black hole in its center. Astronomers know that almost all large galaxies harbor such an object at its center and that, in general, the larger the galaxy, the bigger the black hole. Our home galaxy, the Milky Way, is home to a supermassive black hole, Sagittarius A *, which is over four million times more massive than the Sun. ESO 495-21, also known as Henize 2-10) is a dwarf galaxy, representing only 3% of the size of the Milky Way, and yet there is some evidence to suggest that the black hole in its heart is more than a million times more gigantic than the Sun -An extremely unusual scenario.

This black hole can offer clues as to how black holes and galaxies have evolved early in the universe. The origin of central supermassive black holes in galaxies is still debated: galaxies are formed first and then crush material in their center in black holes or pre-existing black holes do they gather galaxies around them? Have they evolved together – or could the answer be something else?

With its small size, indistinct shape and fast star activity, astronomers believe that ESO 495-21 could be an analogue for some of the first galaxies to form in the cosmos. The discovery of a black hole in the heart of the galaxy is therefore a strong indication that black holes first formed, the galaxies developing and then evolving around them.

The data constituting this image was collected by two of the instruments aboard the NASA / ESA Hubble Space Telescope: the advanced survey camera and the already decommissioned wide-field planetary camera 2 /.

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