Simulated Dwarf Galaxies with Star Formation Shut of by Reionization

Ultra-Faint Dwarf Galaxy Leo IV

Astronomers used the Hubble Space Telescope to unmask the dim, star-starved dwarf galaxy Leo IV. These Hubble images demonstrate why astronomers had a tough time spotting this small-fry galaxy. The image at left shows part of the galaxy, outlined by the white rectangular box....

Leo IV HST/ACS

Background Galaxies in Leo IV Field

Leo IV Stars

Location of Ultra-Faint Dwarf Galaxy Leo IV

These images reveal the small and faint star-starved dwarf galaxy Leo IV, a close neighbor of our Milky Way galaxy. Leo IV is one of more than a dozen ultra-faint dwarf galaxies found lurking around the Milky Way. These galaxies are dominated by dark matter, an invisible...

Leo IV HST/ACS

Leo IV Field SDSS

Dark Matter Simulation in Milky Way Halo

These illustrations, taken from computer simulations, show a swarm of dark matter clumps around our Milky Way galaxy. Some of the dark-matter concentrations are massive enough to spark star formation. Dark matter is an invisible substance that accounts for most of the universe's...

Simulated Dark Matter in Milky Way Halo

Simulated Dwarf Galaxies with Ongoing Star Formation

UFD Galaxy Leo IV Compass and Scale Image

The Evolution of the Stars in the Leo IV Galaxy

This movie shows the evolution of the stars in Leo IV, a dim dwarf galaxy in the halo of our Milky Way galaxy. The Hubble Space Telescope measured the ages of these faint stars in Leo IV and two other similar galaxies, dubbed ultra-faint dwarf galaxies. The Hubble observations...