A team of astronomers used the ALMA telescope to find a slowly rotating galaxy in the early stages of the universe’s life, and they discovered a galaxy that is the youngest among the galaxies they have found before, and it has a weighted rotation rate, which is much slower than the current galaxies.
It is worth noting that all galaxies usually rotate at incredible speeds. For example, the Milky Way has a speed of more than 200 kilometers per second. But astronomers do not yet understand how the speed of galaxies grows to reach these limits. The only way to find out is by measuring the speed of galaxies over cosmic time, and building a map of galactic growth.
More recently, a team of astronomers at Waseda University in Tokyo used the ALMA telescope in Chile to observe a galaxy far, far away. This galaxy, MACS1149-JD1, is so far away that it is usually too dark to be observed. But the light from that galaxy passes through a giant group of galaxies, and the lensing effect caused by the group’s gravity enlarges the image of MACS1149-JD1. Astronomers can use this enlarged image to see the galaxy.
Age of MACS1149-JD1 galaxy and measurement of its rotation
MACS1149-JD1 was born when the universe was only 500 million years old, making it among the youngest known. The team used the ALMA telescope to study the double ionized oxygen in the galactic disk. Then they developed a model of the size of the galactic disk and its rotation speed to compare with the observations. They report their findings in a paper recently published in Astrophysical Journal Letters.
The team found that MACS1149-JD1 is only 3,000 light-years across. This is much smaller than the expanse of the Milky Way, which is more than 100,000 light-years in diameter. They also found that MACS1149-JD1 is spinning at just 50 kilometers per second, which is less than a quarter of the Milky Way’s rotation speed.
“The rotation speed of MACS1149-JD1 is much slower than the speed of the galaxies that followed it in later ages and the speed of our own galaxy,” said Akio Inoh, one of the astronomers co-authoring the paper and working at Waseda University. [درب التبانة]It is possible that JD1 is in an initial stage of rotational development.”
These results indicate that galaxies start out small and rotate slowly. Then, over billions of years, it accumulates more matter and increases its rotation rate. The team hopes to use the James Webb Space Telescope to conduct further studies on the rotation rates of galaxies over cosmic time.
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