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Halo of Andromeda Galaxy Used to Measure Its Drift Across Space
This composite image shows a region in the halo in the neighboring Andromeda galaxy that astronomers used to precisely measure the galaxy's sideways motion on the sky. This has allowed them to predict a direct collision between Andromeda and the Milky Way about 4 billion years from now.
The inset image on the left is from a 2002 Hubble Space Telescope deep exposure that captured the light from 300,000 stars in Andromeda's halo, a vast spherical cloud of stars surrounding the galaxy's bright disk. Embedded in the image are numerous background galaxies that are much father away than Andromeda.
Astronomers compared this region to pictures of the same area taken seven years later. They measured the tiny amount of sideways drift in the halo stars relative to the stationary background galaxy field. The same measurements were done for two other fields in the galaxy as well. This is similar to measuring the drift of a boat relative to a background shoreline.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.00h 42m 44s
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.+41° 16' 9"
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Andromeda
- DistanceDistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.About 2.5 million light-years (770 kiloparsecs)
About the Data
- Data DescriptionData 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 were taken from the HST proposals 9453 and 10265, PI: T. Brown (STScI); and 11684, PI: R. van der Marel (STScI). The science team comprises: R. van der Marel, S.T. Sohn, J. Anderson, and T. Brown (STScI), M. Fardal (University of Massachusetts, Amherst), G. Besla (Columbia University), R. Beaton (University of Virginia), P. Guhathakurta (UCO/Lick Observatory/UCSC), and T.J. Cox (Carnegie Observatories). - InstrumentInstrumentThe science instrument used to produce the data.HST>ACS/WFC and HST>WFC3/UVIS
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.December 2002 and January 2005; January 2010 and August 2010
- FiltersFiltersThe camera filters that were used in the science observations.ACS/WFC: F606W (V) and F814W (I) WFC3/UVIS: F606W (V)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.M31, NGC 224, Andromeda Galaxy
- Object DescriptionObject DescriptionThe type of astronomical object.Starfield in M31
- Release DateMay 31, 2012
- Science ReleaseNASA’s Hubble Shows Milky Way is Destined for Head-on Collision with Andromeda Galaxy
- Credits
This image is a composite of separate exposures acquired by the ACS instrument on HST. Several filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Blue: F606W (V) Red: F814W (I)
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
