NGC 1569: Starburst in a Dwarf Irregular Galaxy
Grand spiral galaxies often seem to get all the glory, flaunting their young, bright, blue star clusters in beautiful, symmetric spiral arms. But small, irregular galaxies form stars too. In fact, as pictured here, dwarf galaxy NGC 1569 is apparently undergoing a burst of star forming activity, thought to have begun over 25 million years ago.
Acknowledgement: A. Aloisi (STScI/ESA) et al.
Hidden Galaxy IC 342
Image Credit & Copyright: Ed Henry (Hay Creek Observatory)
NGC 6302: Bug Nebula
Distance: 3,500 Light Years Away From The Sun
NGC 6302 is a high excitation multi-polar planetary nebula first studied by Emerson Barnard in 1907. The complex planetary nebula is approximately 1900 years old and is expanding at 600 KM/sec.
Summary & Copyright: Robert Gendler
Thor’s Helmet: NGC 2359 in Canis Major
Distance 15,000 light years
In astrophotographs NGC 2359 has an ethereal quality. Surprisingly the outward appearance strongly contradicts the violent events which gave rise to the peculiar nebula. NGC 2359 is a prototypical wind blown bubble powered by the extremely massive and unstable Wolf-Rayet star HD 56925.
These types of stars (only about 300 are known presently) represent a late evolutionary phase of massive O-type blue giants which have become unstable in the late stages of their short stellar life. WR stars heavily influence the surrounding interstellar medium.
There are several basic types of nebulae associated with WR stars which run the gamut from concentric rings (NGC 6888), wind blown bubbles (NGC 7635), to filamentary type nebulae (NGC 2359). NGC 2359 consists of two distinct components.
—Credit Copyright: Robert Gendler
Dark matter: now officially more confusing than ever
Astronomers have one more reason to scratch their heads over the unseen material known as dark matter. Observations of two dwarf galaxies, Fornax and Sculptor, show the dark matter within them is spread out smoothly rather than heaped into a central bulge, contradicting cosmological models.
Researchers know dark matter comprises a far greater percentage of the universe than the ordinary matter making up things like people and stars. Because of this, the distribution of dark matter determines the structure of the cosmos. Galaxies form when they are attracted to and anchored by large clumps of dark matter.
The dwarf galaxies Fornax and Sculptor are themselves made of 99 percent dark matter and only 1 percent normal matter. It is impossible to directly see the dark matter but, by observing the rotation of stars around each galactic center, researchers can detect its influence and map out its distribution.
While simulations suggest that the dark-matter density should increase sharply near the galactic centers, the recent observations found the dark matter spread relatively uniform throughout. Yet if these dwarf galaxies have no “clump” in their center, then what is pinning them in place?