HOME-GROWN dwarf galaxies keep a low profile, while recent arrivals show off. This claim, if true, could explain the long-standing puzzle of why we have spotted so few dwarf galaxies near the Milky Way.
Around 20 dwarf galaxies have so far been found near our galaxy 鈥� far fewer than expected based on simulations of how galactic matter clumps together.
Elena D鈥橭nghia of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and George Lake of the University of Zurich, Switzerland, propose that many go uncounted because they have trouble holding on to the gas needed to form stars in the crowded Milky Way. This would make them practically invisible.
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The few dwarfs that we can see, they say, may have migrated from elsewhere relatively recently. Nine of the brightest dwarf galaxies around the Milky Way are in the same plane, which would suggest they have a common origin.
鈥淚t鈥檚 a plausible hypothesis, but it鈥檚 fairly hard to prove,鈥� says Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Maryland.
