There’s extra to galaxies than meets the attention, and now astronomers have mapped out an enormous invisible area of the galaxy subsequent door. Observations by the Hubble House Telescope have detailed the dimensions and construction of the fuel halo of Andromeda – and located that it’s already bumping up in opposition to that of the Milky Manner, upfront of a cosmic collision.
Galaxies are normally seen as flat disks of stars, however that’s not the complete story. Surrounding most galaxies is a large spherical envelope of fuel and plasma that extends for 1000’s and even tens of millions of light-years. The difficulty is that these constructions are very onerous to see, as a result of the molecules making it up are so diffuse and don’t give off a lot radiation.
To review these halos, astronomers as a substitute analyze the way in which mild filters via from rather more distant objects. Quasars make supply since they’re so vibrant, however for many galaxies just one or two fall in the best line of sight.
However for Andromeda, which is way nearer to us than different galaxies, astronomers have been ready to make use of 43 quasars scattered across the halo. The workforce used Hubble’s Cosmic Origins Spectrograph (COS) to check the ultraviolet mild of those quasars, and the way it’s absorbed by the fuel in Andromeda’s halo.
The workforce discovered that the halo has a layered construction, with one “shell” of fuel nested inside one other. The signatures of enormous quantities of heavy components have been additionally discovered floating round on the market – a smoking gun for supernova explosions.
“We discover the internal shell that extends to a couple of half million light-years is way extra advanced and dynamic,” says Nicolas Lehner, lead researcher on the examine. “The outer shell is smoother and warmer. This distinction is a possible outcome from the affect of supernova exercise within the galaxy’s disk extra immediately affecting the internal halo.”
The workforce additionally discovered that the outer layers attain a lot additional than beforehand recognized. The halo extends 1.3 million light-years from Andromeda, and in some instructions it stretches so far as 2 million light-years.
The intriguing factor about that determine is that it means Andromeda’s halo is already starting to press up in opposition to that of the Milky Manner. The 2 galaxies are anticipated to collide and merge in about 4 billion years’ time, and it appears like that course of is already within the (very, very) early levels.
Since Andromeda is similar to the Milky Manner, this type of work may assist us higher perceive our dwelling galaxy – in spite of everything, it’s difficult to check the Milky Manner’s halo from our place inside it.