Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)

Hubble and Spitzer Uncover Smallest Galaxy Building Blocks

In this image of the Hubble Ultra Deep Field, several objects are identified as the faintest, most compact galaxies ever observed in the distant universe. They are so far away that we see them as they looked less than one billion years after the Big Bang. Blazing with the brilliance of millions of stars, each of the newly discovered galaxies is a hundred to a thousand times smaller than our Milky Way Galaxy.

The bottom row of pictures shows several of these clumps (distance expressed in redshift value). Three of the galaxies appear to be slightly disrupted. Rather than being shaped like rounded blobs, they appear stretched into tadpole-like shapes. This is a sign that they may be interacting and merging with neighboring galaxies to form larger structures.

The detection required joint observations between Hubble and NASA's Spitzer Space Telescope. Blue light seen by Hubble shows the presence of young stars. The absence of infrared light from Spitzer observations conclusively shows that these are truly young galaxies without an earlier generation of stars.

About the Object	Object Name: Galaxies in the Hubble Ultra Deep Field (HUDF) Position (J2000): RA: 03h 32m 40.0s Dec: -27° 48' 00" Constellation: Fornax
About the Data	Image Credit: NASA, ESA, and N. Pirzkal (STScI/ESA) Instrument: Hubble ACS/WFC Filters: F435W (B), F606W (V), F775W (i), F850LP (z) Exposure Date: September 24, 2003 - January 16, 2004 Exposure Time: 11.3 days Field of View: The full HUDF image is 3 arcminutes square. Orientation: North is 48 degreed CCW from up Release Date: September 6, 2007
Observers	N. Pirzkal (STSCI/ESA) S. Malhotra (Arizona State University) J. Rhoads (Arizona State University) C. Xu (Shanghai Institute of Technical Physics) S. Beckwith (STScI) S. Malhotra (STScI) M. Giavalisco (STScI) N. Panagia (STScI) J. Rhoads (STScI) M. Stiavelli (STScI) R. Somerville (STScI) S. Casertano (STScI) B. Margon (STScI) C. Blades (STScI) J. Caldwell (STScI) M. Clampin (STScI) M. Corbin (STScI/CSC) M. Dickinson (STScI) H. Ferguson (STScI) A. Fruchter (STScI) R. Hook (STScI/ECF) S. Jogee (STScI) A. Koekemoer (STScI) R. Lucas (STScI) M. Sosey (STScI) L. Bergeron (STScI) R. Thompson (University of Arizona) G. Illingworth (university of California, Santa Cruz) R. Bouwens (university of California, Santa Cruz) M. Dickinson (STScI) D. Eisenstein (University of Arizona) X. Fan (University of Arizona) M. Franx (University of Leiden) M. Rieke (University of Arizona) A. Riess (STScI) P. van Dokkum (Yale University) H. Yan (Caltech) M Dickinson (NOAO) D. Stern (Jet Propulsion Lab) P. Eisenhardt (Jet Propulsion Lab) R.-R. Chary (Caltech) M. Giavalisco (STScI) H. Ferguson (STScI) S. Casertano (STScI) C. Conselice (Caltech) C. Papovich (Steward Observatory) W. Reach (Caltech) N. Grogin (STScI) L. Moustakas (Jet Propulsion Lab) M. Ouchi (STScI)

Individual Images

	Hubble Ultra Deep Field Screen-Resolution (450x405): JPEG High-Resolution (3000x2700): JPEG | Mac TIFF | PC TIFF Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)
	First Callout Box High-Resolution (335x335): JPEG | Mac TIFF | PC TIFF Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)
	Second Callout Box High-Resolution (335x335): JPEG | Mac TIFF | PC TIFF Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)
	Third Callout Box High-Resolution (335x335): JPEG | Mac TIFF | PC TIFF Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)
	Fourth Callout Box High-Resolution (335x335): JPEG | Mac TIFF | PC TIFF Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)
	Fifth Callout Box High-Resolution (335x335): JPEG | Mac TIFF | PC TIFF Credit: NASA, ESA, and N. Pirzkal (STScI/ESA)

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