(ORDO NEWS) — A team of astronomers used the ALMA telescope to find a slowly rotating galaxy in the early universe. This galaxy is the youngest ever discovered with a measured rotation and is much slower than modern galaxies.
All galaxies rotate, as a rule, at an incredible speed. For example, the Milky Way galaxy has a rotation speed of over 200 kilometers per second.
But astronomers do not yet understand how galaxies accelerate to such speeds. The only way to know this is to measure galaxies throughout cosmic time and build a map of galactic evolution.
Recently, a group of astronomers from Waseda University in Tokyo used ALMA (Atacama Large Millimeter/Submillimeter Array). ) in Chile to observe a very distant galaxy. This galaxy, MACS1149-JD1, is so far away that it is usually too dim to be observed.
But the light from this galaxy is passing through a giant cluster of galaxies, and the gravitational lensing from that cluster magnifies MACS1149. -JD1. Astronomers can use this magnification to see the galaxy.
Measuring the rotation of a galaxy
MACS1149-JD1 existed when the universe was only 500 million years old. , making it one of the youngest known galaxies. The team used ALMA to study O III, or doubly ionized oxygen, in the galaxy’s disk.
They then developed a model for the size and rotational speed of the galaxy’s disk to compare with observations. .
They reported their results in a paper recently published in The Astrophysical Journal Letters.
The team found that MACS1149-JD1 is only 3,000 light-years across. This is much smaller than the Milky Way galaxy, which is over 100,000 light-years across. They also found that MACS1149-JD1 is spinning at just 50 kilometers per second, less than a quarter of the Milky Way’s rotational speed.
“The rotation rate of JD1 is much slower than that of later era galaxies and our [Milky Way] galaxy, and it is likely that JD1 is in its early stages of rotational development,” says Akio K. Inoue, co-author of the paper, also from Waseda University.
These results show that galaxies are initially small and rotate slowly. Then, over billions of years, they accumulate more matter and increase their rate of rotation.
The team hopes to use the James Webb Space Telescope to conduct further research into the rotational speed of galaxies in space time.
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