How do galaxies like the Milky Way form? To trace this question back, we must understand the origin of the mechanics of the rotational motion of galaxies. Astronomers have recently discovered galaxies that have begun to exhibit rotational motion, as early as MACS1149-JD1, which appeared within 500 million years of the Big Bang.
All galaxies in the universe are rotating, often at incredible speeds, such as the Milky Way, which rotates at more than 200 kilometers per second, but astronomers don’t yet understand why galaxies can rotate so fast. The only way to tell is to measure the entire universe galaxies within, build a galaxy evolution map to infer.
Recently, a team from Waseda University in Japan used the Atacama Large Millimeter and Submillimeter Array (ALMA) to observe an extremely distant galaxy, MACS1149-JD1, one of the most distant galaxies in the universe, appearing only 550 million after the Big Bang. year. Usually these types of galaxies are too dim to observe, but the light from MACS1149-JD1 happens to pass through a massive galaxy cluster and is magnified by the gravitational lensing effect, allowing astronomers to observe it.
The team analyzed the galaxy’s doubly ionized oxygen, then developed models to compare with observations and found that the MACS1149-JD1 galaxy is just 3,000 light-years across. Much smaller than the Milky Way, which is over 100,000 light-years in diameter. In addition, the team also found that the MACS1149-JD1 galaxy’s rotation speed is only 50 kilometers per second, less than a quarter of the rotation speed of the Milky Way.
However, MACS1149-JD1 may be the most distant galaxy known to date that has developed rotational motion, suggesting that the galaxy was small and spinning slowly when it first formed, but accumulated more matter over the next billions of years and increase the rotation speed.
The James Webb Space Telescope will observe the galaxy MACS1149-JD1 next year, revealing more clues about how it and other galaxies formed. The new paper is published in Astrophysical Journal Letters.
(Source of the first image: European Southern Observatory)
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