satellite town
/ˈsæt.əl.aɪt ˌtaʊn/noun
a smaller town near a large city, where many people who work in the city live
город-спутник
Русский аналог: «город-спутник»
Это скорее устойчивое сочетание, чем идиома.
“They live in a satellite town outside Manchester.”
“Satellite towns grew quickly after the war.”
“Many satellite towns have their own shopping centres now.”