A radio signal has been detected from abundant cosmic dust in MACS0416_Y1, but the standard models cannot explain the amount of dust. Researchers have had to rethink the history of star formation.
The death of stars
Yoichi Tamura, an associate professor at Nagoya University, Japan, and the lead author of the research paper, explained: “Dust and relatively heavy elements such as oxygen are disseminated by the deaths of stars. Therefore, a detection of dust at some point in time indicates that a number of stars have already formed and died well before that point.”
Tamura and the team used the ALMA (Atacama Large Millimeter/submillimeter Array) to observe the distant galaxy MACS0416_Y1.
Due to the finite speed of light, the radiowaves observed from this galaxy today travelled 13.2 billion years. Thus, they provide an image of the galaxy only 600 million years after the Big Bang.
Because of the finite speed of light, the radio waves we observe from this galaxy today had to travel for 13.2 billion years to reach us. In other words they provide an image of what the galaxy looked like 13.2 billion years ago, which is only 600 million years after the Big Bang.
The astronomers detected a weak signal of radio emissions from dust particles, and from the colour estimated the stellar age at 4 million years old.
Explaining cosmic dust
Ken Mawatari, a researcher at the University of Tokyo, Japan, said: “There have been several ideas proposed to overcome this ‘dust budget crisis’. However, no one is conclusive. We made a new model which doesn’t need any extreme assumptions diverging far from our knowledge of the life of stars in today’s Universe. The model well explains both the color of the galaxy and the amount of dust.”
Researchers now think that MCS0416_Y1 experienced staggered star formation with two intense starburst periods 300 million and 600 million years after the Big Bang, with a quiet phase in between.
Understanding the early history of the Universe
Tamura concluded: “Dust is a crucial material for planets like Earth. Our result is an important step forward for understanding the early history of the Universe and the origin of dust.”