An international team of astronomers recently made a major discovery using the James Webb Space Telescope (JWST). They identified a giant grand-design spiral galaxy, named Zhúlóng, which could well be the most distant ever observed.
This galaxy, located at a photometric redshift of about 5.2, has a mass comparable to that of the Milky Way. Zhúlóng stands out for its well-defined spiral arms, extending over 62,000 light-years, and a classic nucleus. This discovery, published in
arXiv, opens new perspectives on galaxy formation in the young Universe.
Spectral analyses reveal that the nucleus of Zhúlóng is in a quiescent phase, while its disk continues to form stars. This configuration suggests a growth of the galaxy from the inside out, a process still poorly understood in the first few billion years of the Universe.
The star formation rate of Zhúlóng is relatively low, estimated at 66 solar masses per year. However, the efficiency of converting baryons into stars is remarkably high, indicating a transition phase between an active galaxy and a quiescent one.
This discovery raises questions about how quickly mature galaxies could have formed after the Big Bang. Zhúlóng, with its unique characteristics, offers a valuable window into the processes of galaxy formation and evolution in the young Universe.
The researchers, led by Mengyuan Xiao from the University of Geneva, continue to analyze the data to better understand the mechanisms at work in this distant galaxy. Their work could well revolutionize our understanding of the primordial Universe.
What is a grand-design spiral galaxy?
Grand-design spiral galaxies are characterized by their well-defined and symmetrical spiral arms, which extend from a clear central nucleus. These arms are regions of high density where star formation is triggered by the compression of matter.
These galaxies are relatively rare in the young Universe, making the discovery of Zhúlóng particularly significant. Astronomers estimate that grand-design spiral galaxies represent an important stage in galaxy evolution.
The spiral structure is often associated with complex internal dynamics, influenced by gravitational interactions and density waves. These processes play a crucial role in the formation and evolution of galaxies.
How is the redshift of galaxies measured?
Redshift, or redshift, is a key measure in astronomy for determining the distance and age of galaxies. It is calculated by observing the stretching of the wavelengths of light emitted by celestial objects.
For Zhúlóng, the photometric redshift was estimated at about 5.2, corresponding to a time when the Universe was less than a billion years old. This measurement is crucial for understanding galaxy evolution in the young Universe.
Spectroscopy and photometry techniques are used to measure redshift accurately. These methods allow astronomers to reconstruct the history of the Universe and better understand the processes of galaxy formation.