Data from three large-scale cosmic surveys confirm that the Milky Way, the galaxy to which Earth belongs, is quite distinct from its counterparts.
The Milky Way galaxy, known as Ngân Hà in Vietnamese, is the realm that includes Earth and everything else in our solar system, and it is perceived as a giant in the galaxy world.
It is among a select few of the largest galaxies today and has consumed at least 20 smaller galaxies to achieve its current size and mass.
Recently, scientists have embarked on a quest across the universe to identify 101 galaxies with a mass similar to that of the Milky Way, which were initially predicted to share comparable characteristics.
However, the research results revealed a contrasting scenario.
The Milky Way as seen from Chile, actually a spiral galaxy. Our Earth resides at the edge of its brilliant star disk – (Photo: ESO).
According to Universe Today, three large-scale cosmic surveys: SAGA III, SAGA IV, and SAGA V systematically cataloged the satellite systems surrounding the aforementioned 101 galaxies, examined the star formation characteristics of these 101 satellite systems, and ultimately modeled these satellite systems.
The comparison between the Milky Way and the 101 seemingly similar galaxies indicated several significant differences.
A total of 378 satellite galaxies of the Milky Way and the 101 galaxies of comparable mass were analyzed in detail. Among these, four belong to the Milky Way, including the famous Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC).
Some galaxies have fewer or no satellites, but those with oversized satellites like the LMC often possess many satellites, sometimes up to 13. This is because the mass of the largest satellite is directly proportional to the number of satellites of that galaxy.
Only the Milky Way possesses a sparsely populated surrounding space with just 4 satellites. This is the first peculiar point.
The second study based on this dataset indicated that the closer the satellites are to their parent galaxy, the slower their star formation rate, likely due to the strong gravitational pull from the dark matter halo of the parent galaxy.
The second anomaly emerges: Both the LMC and SMC satellites of the Milky Way are undergoing vigorous star formation despite being very close to their “parent”, while those farther away have ceased star formation.
Scientists suggest that this paradox may be because the LMC and SMC have only recently entered the dark matter halo of the Milky Way, but they cannot explain why the other smaller satellites have stopped forming stars.
Professor Risa Wechsler from the SLAC National Accelerator Laboratory in the U.S., co-founder of the SAGA project, stated that the results indicate the Milky Way is a unique type of galaxy in the universe.
To gain further understanding of the unusual place where Earth resides, we can only continue to search the universe for worlds of similar mass that – if lucky – are as peculiar as it is.
