Farther out, at 3.4 million light-years, you spy the dim Sagittarius Dwarf Irregular
Galaxy patrolling the Local Group's lonely frontier.
Further out are a number of similarly sized and slightly misshaped dwarf irregular
galaxies, which are not gravitationally bound to the Milky Way and may be relative newcomers to our galactic neighborhood.
Not only are these conditions typical for dwarf irregular
galaxies like the SMC, they also mimic ones that would have existed in the early universe.
Hodge, "Oxygen abundances in nearby dwarf irregular
galaxies," The Astrophysical Journal, vol.347, pp.875-882, 1989.
Wrapping up this part of the survey is the tiny dwarf irregular
1C 10 in Cassiopeia.
The dwarfs we've visited so far have been satellites of the Andromeda Galaxy, but the status of the Pegasus Dwarf Irregular
(UGC 12613) is less certain.
It's a dwarf irregular
galaxy and is heavily obscured because we see it through the dusty plane of our galaxy.
The brighter one is IC 1613, a dwarf irregular
galaxy about 2.4 million light-years away, just a little closer than the Andromeda Galaxy.
More than a ripple in the preexisting halo, this arc or stream seems to be the actual remains of a dwarf irregular
galaxy consumed by NGC 5128 some 200 to 400 million years ago, the astronomers write in the December 2002 Astronomical Journal.
Finally, among the brightest of the dwarf irregular
galaxies in Virgo is 13th-magnitude IC 3475, a half degree northwest of M87.
Scientists from the International Centre for Radio Astronomy Research have found all galaxies, from small dwarf irregulars
to the largest spirals, behave like clocks and take about a billion years to complete a single spin.
Gallagher (University of Wisconsin), their search for these objects in the local supercluster revealed not only spirals and dwarf irregulars
, but also some possibly interacting systems as well as rare miniature spirals.