NASA's Hubble, world's first space-based optical telescope, has marked another phenomenal discovery of a tiny dwarf galaxy as ancient as the universe itself.

The astronomers accidentally found it while they were using the observatory to take an image of the vast stellar population within the NGC 6752, the globular cluster in the constellation Pavo.

The unexpected finding was published in the journal Monthly Notices of the Royal Astronomical Society: Letters.

 A Serendipitous Astronomical Discovery

The international team of astronomers who have been using NASA's Hubble Space Telescope investigates the existence of oldest and faintest white dwarf stars in NGC 6752. The main purpose of their study is to find out the age of the globular cluster.

However, in the process, the team serendipitously uncovered the never-before-seen diminutive galaxy in the cosmic backyard thanks to Hubble's sharp vision. All this time, the loner galaxy has remained hidden far behind the compact collection of stars within NGC 6752, 30 million light-years away or around 2,300 times more distant than the foreground cluster.

Bedin 1 As Fossil Of The Early Universe

Nicknamed by its discoverers as Bedin 1, the hidden dwarf galaxy measures around 3,000 light-years, which is only a fraction of the size of the Milky Way. The astronomers estimate that it is nearly 13 billion years old or about the same age of the universe, making it the "astronomical equivalent of a living fossil from the early Universe."

Because it is tiny and extremely faint, astronomers classify it as a dwarf spheroidal galaxy. By definition, dwarf spheroidal galaxies are characterized by their common features such as small size, low luminosity, lack of dust, and old stellar populations.

Prior to Bedin 1's accidental discovery, it is already known that 36 dwarf spheroidal galaxies exist in the Local Group of Galaxies. The Milky Way constitutes 22 of these as its satellite galaxies.

While dwarf spheroidal galaxies are not quite rare, Bedin 1 is distinctively unique. To date, it is the farthest tiny dwarf galaxy ever found, as it lies about 2 million light-years from the closest galaxy host, NGC 6744.

Since its launch in April 1990, Hubble Space Telescope has been used to observe the farthest stars and galaxies, including planets in the solar system.