Ghostly space cities: new galaxies discovered that defy explanation (photos).

Scientists have discovered three new extremely faint dwarf galaxies that have never been seen before. These galaxies are very small and located far from larger galaxies. They contain only a few hundred thousand old stars and lack the interstellar gas necessary for forming new stars. This suggests that some event in the early Universe suppressed the star formation process in these dwarf galaxies. The study has been published in The Astrophysical Journal Letters, as reported by IFLScience.

While the Milky Way and similar large galaxies host hundreds of billions of stars of various ages, the three newly discovered faint dwarf galaxies contain only a few hundred thousand old stars. This indicates that a long time ago in the early Universe, something obscured the process of new star formation and removed the interstellar gas required for their creation.

The three new dwarf galaxies, classified as among the faintest and thus poorly detectable, are located in the Sculptor constellation and have been named Sculptor A, Sculptor B, and Sculptor C.

All three galaxies are millions of light-years away from us, but no larger neighbors have been found nearby. This poses a challenge when trying to explain why these galaxies ceased forming new stars long ago in the early Universe.

Such small galaxies cannot retain the interstellar gas necessary for star formation if a large galaxy is nearby, meaning they are satellites of the larger galaxy. The gravity of the large galaxy would continuously pull this valuable gas away from the dwarf galaxies, halting the process of new star formation. However, the discovered galaxies, as mentioned earlier, are located in an isolated region of space.

Astronomers have referred to these galaxies as ghost cities in space, which are difficult to explain, although there are some hypotheses regarding the absence of new stars in them.

Scientists suggest that the cause may be an era in the early Universe's history known as the reionization epoch. A few hundred million years after the Big Bang, intense radiation from the very first stars filled the cosmos and caused the hydrogen gas in the smallest galaxies to evaporate. This hydrogen was supposed to be the main ingredient for forming new stars.

Another hypothesis posits that some of the earliest stars in the dwarf galaxies exploded as extremely powerful supernovae. The radiation from these explosions could have expelled interstellar gas from the galaxies.

To better understand what happened to these three galaxies, scientists say it is necessary to discover similar objects in greater numbers that are located in isolated regions of space. Previously, extremely faint dwarf galaxies have only been found near the Milky Way.