OC Astronomy

IC 2574: Coddington's Nebula

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, dwarf galaxy IC 2574 shows clear evidence of intense star forming activity in its telltale reddish regions of glowing hydrogen gas. Just as in spiral galaxies, the turbulent star-forming regions in IC 2574 are churned by stellar winds and supernova explosions spewing material into the galaxy's interstellar medium and triggering further star formation. A mere 12 million light-years distant, IC 2574 is part of the M81 group of galaxies, seen toward the northern constellation Ursa Major. Also known as Coddington's Nebula, the faint but intriguing island universe is about 50,000 light-years across, discovered by American astronomer Edwin Coddington in 1898.

Image Credit & Copyright: Dane Vetter

W5: The Soul Nebula

Stars are forming in the Soul of the Queen of Aethopia. More specifically, a large star forming region called the Soul Nebula can be found in the direction of the constellation Cassiopeia, whom Greek mythology credits as the vain wife of a King who long ago ruled lands surrounding the upper Nile river. Also known as Westerhout 5 (W5), the Soul Nebula houses several open clusters of stars, ridges and pillars darkened by cosmic dust, and huge evacuated bubbles formed by the winds of young massive stars. Located about 6,500 light years away, the Soul Nebula spans about 100 light years and is usually imaged next to its celestial neighbor the Heart Nebula (IC 1805). The featured image, taken from near Nashville, Tennessee, USA, is a composite of 234 hours of exposures made in different colors: red as emitted by hydrogen gas, yellow as emitted by sulfur, and blue as emitted by oxygen.

Image Credit & Copyright: Jeffrey Horne

NGC 6888: The Crescent Nebula

NGC 6888, also known as the Crescent Nebula, is a about 25 light-years across, a cosmic bubble blown by winds from its central, massive star. This deep telescopic image includes narrowband image data, to isolate light from hydrogen and oxygen atoms. The oxygen atoms produce the blue-green hue that seems to enshroud the nebula's detailed folds and filaments. Visible within the nebula, NGC 6888's central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years. In fact, the Crescent Nebula's complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life, this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

Image Credit & Copyright: Greg Bass

Spiral Galaxy NGC 3370 from Hubble

Is this what our own Milky Way Galaxy looks like from far away? Similar in size and grand design to our home Galaxy (although without the central bar), spiral galaxy NGC 3370 lies about 100 million light-years away toward the constellation of the Lion (Leo). Recorded here in exquisite detail by the Hubble Space Telescope, the big, beautiful face-on spiral is not only photogenic, but has proven sharp enough to study individual stars known as Cepheids. These pulsating stars have been used to accurately determine NGC 3370's distance. NGC 3370 was chosen for this study because in 1994 the spiral galaxy was also home to a well studied stellar explosion -- a Type Ia supernova. Combining the known distance to this standard candle supernova, based on the Cepheid measurements, with observations of supernovas at even greater distances has helped to reveal the size and expansion rate of the entire Universe itself.

Image Credit: ESA/Hubble & NASA, A. Riess, K. Noll