The Andromeda Galaxy, our nearest large neighbour, has 36 identified dwarf galaxies. The Hubble telescope took images of Andromeda and its dwarfs during more than 1,000 orbits, creating a precise 3D map. Astronomers used these observations to reconstruct the dwarf galaxies\u2019 star formation histories. <\/p>\n
The results show that their environment plays a critical role in their star formation and their quenching.<\/p>\n
<\/p>\n When galaxies are quenched, they no longer form stars. It happens because the supply of star-forming gas is diminished or somehow made unavailable. This typically happens because of black hole feedback or when a galaxy moves through a dense galaxy cluster, and its gas is stripped away. <\/p>\n However, the dwarf galaxies around Andromeda (M31) seem to follow an unusual pattern of star formation and quenching. New research shows that the rambunctious environment around M31 is responsible. <\/p>\n The research is \u201cThe Hubble Space Telescope Survey of M31 Satellite Galaxies. IV. Survey Overview and Lifetime Star Formation Histories,\u201d published in The Astrophysical Journal. Alessandro Savino from the Department of Astronomy at UC Berkeley is the lead author.<\/p>\n Astronomers aren\u2019t certain how many dwarf galaxies the Milky Way has, but it looks like Andromeda, with its dozens of dwarf galaxies, has had a more active history of mergers and absorptions. M 31 may have merged with another massive galaxy a few billion years ago, and its abundant dwarf galaxies could be from its eventful past and its sheer mass. <\/p>\n \u201cOur knowledge of low-mass galaxy formation has long been anchored by Milky Way (MW) satellite galaxies,\u201d the authors write. \u201cIt remains unclear if the insights learned from MW satellites, and their particular formation pathways, are applicable to other satellite systems and low-mass galaxies in general.\u201d<\/p>\n \u201cThere\u2019s always been concerns about whether what we are learning in the Milky Way applies more broadly to other galaxies.\u201d<\/p>\n Daniel Weisz, UC Berkeley. <\/cite><\/p><\/blockquote>\n<\/figure>\n Studying dwarf galaxies is challenging. We\u2019re inside the Milky Way, which makes observing its outskirts difficult. Dwarf galaxies are also dim, adding to their detection difficulty. Detecting them in distant galaxies is likewise difficult. Comparing the MW low-mass dwarf galaxies with those in other galaxies means contending with multiple layers of difficulty. Fortunately, the Andromeda galaxy is wide open to observations. <\/p>\n \u201cFrom >1000 orbits of HST imaging, we present deep homogeneous resolved star colour-magnitude diagrams that reach the oldest main-sequence turnoff and uniformly measured star formation histories (SFHs) of 36 dwarf galaxies associated with the M31 halo,\u201d the authors write. They did the same for 10 additional fields in M31, M33, and the Giant Stellar Stream. M33 is the Triangulum Galaxy, the third largest member of the Local Group after M31 and the Milky Way. M33 is also one of M31\u2019s satellites. The Giant Stellar Stream is a long ribbon of stars that are the remnants of a galaxy absorbed by M31. <\/p>\n The observations reveal a tight correlation between a dwarf\u2019s star formation history, its mass, and its proximity to M31.<\/p>\n \u201cWe see that the duration for which the satellites can continue forming new stars really depends on how massive they are and on how close they are to the Andromeda galaxy,\u201d said lead author Savino in a press release. \u201cIt is a clear indication of how small-galaxy growth is disturbed by the influence of a massive galaxy like Andromeda.\u201d<\/p>\n Astronomers are in a difficult spot when it comes to studying galaxies in detail. Our own Milky Way is the only galaxy that\u2019s open to detailed investigation. The temptation is to draw parallels between our knowledge of the MW and other galaxies. <\/p>\n \u201cThere\u2019s always a tendency to use what we understand in our own galaxy to extrapolate more generally to the other galaxies in the universe,\u201d said principal investigator Daniel Weisz of the University of California at Berkeley. \u201cThere\u2019s always been concerns about whether what we are learning in the Milky Way applies more broadly to other galaxies. Or is there more diversity among external galaxies? Do they have similar properties? Our work has shown that low-mass galaxies in other ecosystems have followed different evolutionary paths than what we know from the Milky Way satellite galaxies.\u201d<\/p>\n These detailed, 1,000-orbit observations of Andromeda are helping change this. They reveal a more chaotic environment than in the Milky Way. <\/p>\n \u201cEverything scattered in the Andromeda system is very asymmetric and perturbed. It does appear that something significant happened not too long ago,\u201d said Weisz. <\/p>\n \n\n
![\"For](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2025\/02\/Andromeda-Halo-labelled.jpg\")