Milky Way-like

Most distant disk galaxy discovered

This image shows the galaxy REBELS-25 from the perspective of the ALMA telescope network, overlaid with an infrared image of other stars and galaxies.

(Bild:  ALMA (ESO/NAOJ/NRAO)/L. Rowlan et al., Krone KREATIV)

With the help of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope network, in which the European Southern Observatory (ESO) is also involved, astronomers have discovered the most distant Milky Way-like galaxy observed to date. Its light was emitted when the universe was only 700 million years old ...

The disk galaxy called REBELS-25, whose rotation and structure was determined using ALMA, appears to be as ordered as today's galaxies. This is surprising because, according to previous knowledge, the formation of such early galaxies should appear more chaotic.

Ancient galaxy resembles our Milky Way
"Seeing a galaxy that is so similar to our own Milky Way and that rotates strongly challenges our understanding of how quickly galaxies in the early universe evolve into the orderly galaxies of today's cosmos," explains Lucie Rowland from Leiden University in the Netherlands.

"According to our understanding of galaxy formation, we expect most early galaxies to be small and chaotic," explains Jacqueline Hodge, astronomer at Leiden University and co-author of the study. Until now, it was assumed that the chaotic early galaxies evolved at an incredibly slow pace into more uniform forms.

Discovery calls previous theories into question
Current theories suggest that a galaxy that is roughly as ordered as our Milky Way - a rotating disk with clear structures such as spiral arms - must have undergone billions of years of evolution. However, the discovery of REBELS-25 calls this chronological sequence into question.

Surprisingly, the data collected using ALMA also point to more evolved features of the REBELS-25 galaxy that resemble those of the Milky Way, such as a central elongated bar and even spiral arms - although further observations are needed to confirm this, the researchers say.

Future observations of REBELS-25, as well as other discoveries of early rotating galaxies, would potentially change our understanding of early galaxy formation and the evolution of the universe as a whole, according to the ESO website.

The ALMA observatory of the European Southern Observatory ESO in Chile

(Bild: ESO/L. Calçada, NAOJ/NRAO)

Unique location on a high plateau in Chile
The ALMA telescope network (pictured above) observes radio waves from the universe in the lower energy range of the electromagnetic spectrum. The super telescope, which opened in 2013, is located more than 5,000 meters above sea level on the Chajnantor Plateau in the Atacama Desert in Chile. It is operated by the ESO, of which Austria is also a member, as well as partners from North America, East Asia and Chile.