A Halo for Andromeda
Digital Illustration Credit: NASA, ESA, J. DePasquale and E. Wheatley (STScI) and Z. Levay
Explanation: M31, the Andromeda Galaxy, is the closest large spiral galaxy to our Milky Way. Some 2.5 million light-years distant it shines in Earth's night sky as a small, faint, elongated cloud just visible to the unaided eye. Invisible to the eye though, its enormous halo of hot ionized gas is represented in purplish hues for this digital illustration of our neighboring galaxy above rocky terrain. Mapped by Hubble Space Telescope observations of the absorption of ultraviolet light against distant quasars, the extent and make-up of Andromeda's gaseous halo has been recently determined by the AMIGA project. A reservoir of material for future star formation, Andromeda's halo of diffuse plasma was measured to extend around 1.3 million light-years or more from the galaxy. That's about half way to the Milky Way, likely putting it in contact with the diffuse gaseous halo of our own galaxy.
仙女座大星系的氣暈
數位圖示提供: NASA, ESA, J. DePasquale and E. Wheatley (STScI) and Z. Levay
說明: 仙女座大星系(M31)是離我們銀河系最近的大螺旋星系。約2百50萬光年遠的M31,在地球的夜空中,是一個肉眼勉強可見的暗淡條形雲狀天體。不過,懸在這道嵯峨巖脈上方的這個鄰近星系,還有個肉眼不得見,在這幅數位圖示中以粉紅色澤標示,由熾熱電離氣體構成的龐大氣暈。以前,哈伯太空望遠鏡經由觀測背景類星體發出的紫外光受到的吸收,從而繪測出這個氣暈。不過,這個瀰漫電漿暈的範圍和組成最近才剛由AMIGA計畫測定,並發現它是未來可形成恆星的物質庫,而且從仙女座大星系向外綿延超過1百30萬光年。這個距離約是銀河系與仙女座星系間距之半,因此,這個氣暈可能和我們銀河系的瀰漫氣暈相接。