Where is the Milky Way’s sibling now?

Once upon a time there were three siblings who roamed the universe together. Two of their names are still known today: the Milky Way and the Andromeda Galaxy are still the dominant galaxies of the Local Group. But the third sibling went missing two billion years ago – today, astronomers call it “M32p.” At the time, M32p was the third largest galaxy of the Local Group and twenty times larger than any galaxy that has ever merged with the Milky Way.

As it turns out, Andromeda might know a thing or two about M32p’s fate. Astronomers have found telltale signs in Andromeda’s halo, which is dominated by metal-rich, middle-aged stars. Computer simulations have shown that this would be possible only by a merger with another, very large galaxy. Today, its core is located in Andro-Beta, M32, an elliptical dwarf galaxy that is one of Andromeda’s companions.

In 3.75 billion years, Andromeda and the Milky Way will merge. This is what it might look like from Earth. (Picture: NASA, ESA, Z. Levay and R. van der Marel (STScI) and A. Mellinger)
Today, the compact core of the dwarf galaxy M32 is no longer very impressive (Picture: Tod R. Lauer/NASA)

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BrandonQMorris
  • BrandonQMorris
  • Brandon Q. Morris es físico y especialista en el espacio. Lleva mucho tiempo preocupado por las cuestiones espaciales, tanto a nivel profesional como privado, y aunque quería ser astronauta, tuvo que quedarse en la Tierra por diversas razones. Le fascina especialmente el "qué pasaría si" y a través de sus libros pretende compartir historias convincentes de ciencia ficción dura que podrían suceder realmente, y que algún día podrían suceder. Morris es autor de varias novelas de ciencia ficción de gran éxito de ventas, como la serie Enceladus.

    Brandon es un orgulloso miembro de la Science Fiction and Fantasy Writers of America y de la Mars Society.