Galaxies are the largest single structures in the universe we know, and stars, planets, asteroids, and black holes are all included. But in early 2020, a galaxy observed by astronomers refreshed our understanding of the universe.
Like all other celestial bodies, individual galaxies vary greatly in size. One of the smallest galaxies is called Segue 2, which "just" has just over 1,000 stars. On the other hand, a galaxy called ESO 146-IG 005 is 10 times larger than our Milky Way. The largest galaxy observed today is Malin 1, which is over 500,000 light-years in diameter and is 5 times wider than our Milky Way. But scientists still haven't listed Malin 1 or ESO 146-IG 005 as very large galaxies. In the classification of galaxies, "extreme mass" is still a fairly new term.
The term was originally used to describe a black hole 10 billion times more massive than the Sun, thus coining the term "extreme mass," a grade higher than "supermassive." After all, the gap between a black hole with only 100 times the mass of the Sun and a black hole with 66 billion times the mass of the Sun (the largest black hole discovered) is still very large. However, "extreme mass" as an adjective for celestial objects is only just beginning to be popularized. Other scientists have been reluctant to use the term to describe galaxies. Nevertheless, the XMM-2599 galaxy is already considered a very massive galaxy, and its story is even more amazing than what has just been said.
"It's really super big". The XMM-2599 galaxy was discovered by astronomers at the Keck Observatory in Hawaii. This galaxy is about 12 billion light-years away. It's big enough to be labeled "Monster Galaxy." What makes it special is not the size of it and the number of stars it has now, but the speed at which it conceives stars is particularly fast and then quickly stops. In its first 800 million years, XMM-2599 gave birth to nearly 300 billion stars. Relatively speaking, the Milky Way, which has the same number of stars (optimistic estimates) and is one of the oldest galaxies in the universe, would take 13.5 billion years to conceive so many stars.
Thus, over a fraction of the time, this ancient galaxy succeeded in creating many stars, just as the Milky Way created stars throughout the course of its existence. Even in the infinite space, it is amazing! So, if the whole galaxy is so huge and bright, why are we just learning about it? Of course, with all of our advancing technologies, have we uncovered this vast universe a long time ago? That's why we barely rely on XMM-2599 in another unusual way: it stopped star-birth in the universe even 2 billion years ago—more than 11 billion years ago.
This galaxy didn't produce new stars billions of years ago — although its size and mass produced a very faint light. In the astronomical community, this is described as "dimming", which is why we took so long to discover it. Ultimately, this discovery required a highly specialized and special instrument, the more appealing instrument named MOSFIRE. Among other things, MOSFIRE or multi-celestial spectrographs for infrared exploration can see beyond the familiar visible spectrum.
So how does a galaxy "dim" and stop giving birth to new stars? It's not something that the Milky Way hasn't happened yet, it's still creating new stars. Scientists don't yet have a reliable answer to this mystery. For us, "galaxy dimming" is a new phenomenon, but the basic assumption explains that it is simply running out of fuel. Importantly, XMM-2599 hasn't lost any mass —everything inside is still inside—only that all of its brightest stars have perished. The largest stars are often the brightest, but they also tend to have the shortest lifetimes.
Perhaps it's invisible, oversized entities that once powered these types of stars by a higher than average number. Conversely, long-lived stars like red dwarfs may still exist because they often exist within the parameters of the XMM-2599 galaxy. However, from our particular point of view, these galaxies are so dim that they are extremely difficult to detect, so this is a compliment to MOSFIRE. This discovery and the explanation of "what does it mean" are just beginning to take shape... But there are some conclusions that must be drawn. First, just because the galaxy is currently dim doesn't mean it's going to be permanently dark. Some of the brightest galaxies in our night sky formed as a result of collisions in the Milky Way — an experience that the Milky Way and Andromeda also plan to have in about 4.5 billion years.
Like all matter, XMM-2599 is always moving through space, so one day it could also devour another galaxy to regain energy and light up the entire galaxy. The galaxy is so large that if a galaxy annexation does occur, astronomers say it could create a galactic city in the night sky. Elsewhere, the discovery has more profound implications for current early astronomical models. Scientists don't understand how XMM-2599 made so many stars so quickly, or how it achieved such a massive mass when the universe was born and everything was smaller and lighter.
In general, large galaxies in particular can only do so by merging with other galaxies, but, based on most contemporary ideas about how the universe works, this galaxy should not have had enough time to merge to get its scale. And, it seems like because it's "dark" as we know it, and it's not growing in the billions of years since it dimmed, so it's something that scratches its head at its highest degree. This is not to say that it destroyed everything we thought we knew about early astronomy, but simply changed it.
We now know that this ancient galaxy does exist, and we might predict that there are other galaxies that we haven't detected but are the same as it. Yes, it's a problem, but in reality it only shows us what we already know, and when it comes to the universe, we still have a lot to learn. And, in fact, the XMMM-2599 is not completely self-contained. There are other strange and unusual galaxies far away, some of which share characteristics with it. For example, a galaxy known as Dragonfly 44 is shaped like a traditional galaxy, but it is made up of dark matter rather than typical stars. At the same time, there are galaxies like Messier 82, like XMM-2599 at the beginning of the universe, producing stars at incredible speeds.
Nevertheless, the discovery of XMM-2599 has once again opened the door to possibilities. Because, if something as massive as this can go unnoticed for billions of years, what about the rest? Of the at least 100 billion galaxies in the observable universe, we still have a lot to know about what they look like and how they work... But it's always exciting when the "newfound" threat focuses on everything we thought we knew!
fy: Masaru Takeshima, Little Prince, OldKid, Lord Moe