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Stellar Motions of Halo Stars in Milky Way

Stellar Motions of Halo Stars in Milky Way
This illustration shows the disk of our Milky Way galaxy, surrounded by a faint, extended halo of old stars. Astronomers using the Hubble Space Telescope to observe the nearby Andromeda galaxy serendipitously identified a dozen foreground stars in the Milky Way halo. They measured the first sideways motions (represented by the arrows) for such distant halo stars. The motions indicate the possible presence of a shell in the halo, which may have formed from the accretion of a dwarf galaxy. This observation supports the view that the Milky Way has undergone continuing growth and evolution over its lifetime by consuming smaller galaxies.

About the Data

  • Data Description
    Data DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
    Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.
    The Hubble data used in this science finding are from proposals 9453 and 10265, PI: T. Brown (STScI), and 11684, PI: R. van der Marel (STScI). The science team consists of: A. Deason and P. Guhathakurta (University of California, Santa Cruz), and R. van der Marel, T. Sohn, and T. Brown (STScI).
  • Instrument
    InstrumentThe science instrument used to produce the data.
    HST>ACS/WFC and HST>WFC3/UVIS
  • Exposure Dates
    Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
    December 2002 - January 2003, August 2004 - January 2005, January - August 2010
  • Filters
    FiltersThe camera filters that were used in the science observations.
    F606W (V) and F814W (I)
  • Object Name
    Object NameA name or catalog number that astronomers use to identify an astronomical object.
    Milky Way Halo
  • Object Description
    Object DescriptionThe type of astronomical object.
    Milky Way Shell Structure
  • Release Date
    February 21, 2013
  • Science Release
    Stellar Motions in Outer Halo Shed New Light on Milky Way Evolution
    Read the release
  • Credit
    Illustration: NASA, ESA, and A. Feild (STScI); Science: NASA, ESA, A. Deason and P. Guhathakurta (University of California, Santa Cruz), and R. van der Marel, T. Sohn, and T. Brown (STScI)

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Details

Last Updated
Mar 28, 2025
Contact
Media

Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov

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