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Hubble Finds Mature Galaxy Masquerading as Toddler
NASA's Hubble Space Telescope quashed the possibility that what was previously believed to be a toddler galaxy in the nearby universe may actually be considered an adult. Called I Zwicky 18, this galaxy has a youthful appearance that resembles galaxies typically found only in the early universe. Hubble has now found faint, older stars within this galaxy, suggesting that the galaxy may have formed at the same time as most other galaxies.
I Zwicky 18 is classified as a dwarf irregular galaxy and is much smaller than our Milky Way Galaxy. The concentrated bluish-white knots embedded in the heart of the galaxy are two major starburst regions where stars are forming at a furious rate. The wispy blue filaments surrounding the central starburst regions are bubbles of gas that have been blown away by stellar winds and supernovae explosions from a previous generation of hot, young stars. This gas is now heated by intense ultraviolet radiation unleashed by a new generation of hot, young stars.
A companion galaxy lies just above and to the left of I Zwicky 18. The companion may be interacting with I Zwicky 18 by gravitationally tugging on the galaxy. The interaction may have triggered the galaxy's recent star formation that is responsible for the youthful appearance. Besides the bluish-white young stars, white-reddish stars also are visible in both I Zwicky 18 and its companion. These stars may be as old as 10 billion years. The reddish extended objects surrounding I Zwicky 18 and its companion are ancient, fully formed galaxies of different shapes that are much farther away.
Hubble data also allowed astronomers for the first time to identify Cepheid variable stars in I Zwicky 18. These flashing stellar mile-markers were used to determine that I Zwicky 18 is 59 million light-years from Earth, almost 10 million light-years more distant than previously believed.
The observations of I Zwicky 18 were taken in 2005 and 2006 with Hubble's Advanced Camera for Surveys. Astronomers made this image by combining observations taken with blue and red filters.
The science team consists of Alessandra Aloisi and Marco Sirianni of the Space Telescope Science Institute and the European Space Agency; Francesca Annibali, Jennifer Mack, and Roeland van der Marel of the Space Telescope Science Institute; Abhijit Saha of the National Optical Astronomy Observatories; and Gisella Clementini, Rodrigo Contreras, Giuliana Fiorentino, Marcella Marconi, Ilaria Musella, and Monica Tosi of the Italian National Astrophysics Institutes in Bologna and Naples.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.19h 34m 1.89s
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.55° 14' 25.99"
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Ursa Major
- 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.Approximately 60 million light-years (18 Megaparsecs) away.
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.This image is roughly 1.7 arcminutes (29,000 light-years or 9 kiloparsecs) wide.
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 image was created from HST data from proposal 10586: A. Aloisi (STScI/ESA), G. Clementini (Astronomical Observatory of Bologna), M. Marconi and I. Musella (Astronomical Observatory of Capodimonte, Italy), A. Saha (National Optical Astronomy Observatories/AURA), M. Sirianni (STScI/ESA), M. Tosi (Astronomical Observatory of Bologna), and R. van der Marel (STScI). The science team comprises: A. Aloisi and M. Sirianni (STScI/ESA), F. Annibali, J. Mack, and R. van der Marel (STScI), A. Saha (National Optical Astronomy Observatories/AURA), and G. Clementini, R. Contreras, G. Fiorentino, M. Marconi, I. Musella, and M. Tosi (Italian National Astrophysics Institutes in Bologna and Naples). - InstrumentInstrumentThe science instrument used to produce the data.HST>ACS/WFC
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.October 2005 - January 2006, Exposure Time: 15 hours
- FiltersFiltersThe camera filters that were used in the science observations.F660W (V) and F814W (I)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.I Zwicky 18, I Zw 18
- Object DescriptionObject DescriptionThe type of astronomical object.Galaxy
- Release DateOctober 16, 2007
- Science ReleaseHubble Finds ‘Dorian Gray’ Galaxy
- CreditNASA, ESA, and A. Aloisi (Space Telescope Science Institute, Baltimore, Md., and European Space Agency)
This image is a composite of many separate exposures made by the ACS instrument on the Hubble Space Telescope. Two filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Cyan: F660W (V) Orange: F814W (I)
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Youthful-looking Galaxy May Be an Adult
NASA's Hubble Space Telescope quashed the possibility that what was previously believed to be a toddler galaxy in the nearby universe may actually be considered an adult. Called I Zwicky 18, this galaxy has a youthful appearance that resembles galaxies typically found only in...
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
