It was unexpected: near the Andromeda galaxy, which had been studied for centuries, amateur astronomers discovered a huge cloud of gas. It is unlike any known astronomical body!
The first known written mention of it dates back to 964, more than a thousand years ago: Andromeda galaxy, also referred to as M31, was one of the first deep-sky objects to be studied in detail. Visible to the naked eye, especially on clear nightsNorthern HemisphereNorthern HemisphereThis galaxy can be classified as a “neighbor” of our universe spiral galaxyspiral galaxy closest to Milky WayMilky Way. So much so that it has been the subject of several publications, scrutinizing it and detailing its composition. But a new study published in RNAAS He tells of a startling discovery, and above all a very unexpected one: a stranger cloudsclouds from GasGas Never before has he been on the outskirts of this galaxy. He’s never seen anything like it!
Late detection of its composition
It all started when Astronomy scientistsAstronomy scientists Amateurs conducted various visual surveys in the direction of Andromeda galaxylocated at 2.55 millionlight yearslight years from U.S. Through the use of various imaging systems, they targeted several linesemissionemissionof which Hα, is a characteristichydrogenhydrogen Ionized gas, the main constituent of most gas clouds, and others to a lesser extent are present in nebulae. With 22 nights of observations between August and October 2022 Various Observation Sites in Lorraine, France. They obtained the Hα and O III emission spectra, characteristic ofoxygenoxygen Double ionization, denoted by O2+.
And that’s where they saw a large O III emission haze, located one degree southeast galaxy Andromeda. To confirm their discovery, the astronomers took new images centered at another location. The cloud itself appeared, thus revealing that it wasn’t an equipment artifact or wasn’t from starstar Or the M31 itself. Finally, new confirmations came from various places in the United States, obtained thanks to other astronomers.
We do not know its origin
As the study shows, this cloudy There is no apparent emission equivalent in the readings at X rayX rayAnd UVUVOptical, infrared and radioradio » And It has not been previously reported in the literature. Then an unanswered question remains: Why was this strange cloud not detected before? Astronomers say this is because of its low brightness and wide angular size, which makes it difficult to detect with most imaging systems.
The authors then discuss the possible origin of the cloud, without coming up with a preferred scenario. Maybe Planetary nebula, because the filamentous structures of the nebula resemble it. But the ratio of the abundance of double ionized oxygen to ionized hydrogen means a temperature above 60,000 KelvinsKelvinswhich cannot be generated by any surrounding astronomical body.
Then hypothesis A remains the restthe rest from SupernovaSupernova which, this time, might create the right proportion of abundance. But such a scenario does not explain the lack of coincidence of radio or ultraviolet emissions. Finally, there is an interaction between Andromeda galaxyAndromeda galaxy And the Milky Way can create clouds similar to those observed. But here again, there’s a problem: the cloud is very close to M31, in its range astral halo same ! The study concluded the need to know the cloud’s radial velocity that would make it possible to learn more about its interactions with M31 and its halo, which is currently in the process of being obtained.
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