In the left corner, wearing a red nucleus surrounded by blue
spiral arms, is M81. In the right corner, sporting light stars and dark dust
lanes, is M82. These two mammoth galaxies have been locked in gravitational
combat for the past billion years. The gravity from each galaxy dramatically
affects the other during each hundred million-year pass. Last go-round,
M82's gravity likely raised circulating density waves rippling around M81
resulting in the richness of M81's spiral arms. M81, though, left M82 a
messy pulp of exploded stars and colliding gas so violent it emits bright
X-rays. In both galaxies, colliding gas has created a recent abundance of
bright new stars. In a few billion years only one galaxy will remain.
The Pinwheel Galaxy M101 - NGC5457 Dist. 15 millions l.y. A giant pinwheel of stars resembling the Milky Way galaxy in shape and size, the spiral appears almost face-on our view; the dark filaments in its arms are dust lanes. (Kitt Peak National Observatory).
Cat's Eye Nebula NGC 6543 Planetary Nebula Magn. 8.8 - Dist. 3.600 l.y. 11.4 magnitude central star
The image shows one of the most complex planetary nebulae ever seen. It reveals intricate structures including concentric gas shells, jets of high-speed gas and unusual shock-induced knots of gas. This nebula is estimated to be 1,000 years old and is a visual record of the dynamics and late evolution of a dying star. Although the center point of light in this Hubble image appears to be one star, a first interpretation suggests that the star might be a double-star system. The effects of two stars orbiting one another would explain the intricate structures which are more complex than what is usually seen in most planetary nebulae. By looking at this image it is noted that a fast stellar wind of gas was blown off the central star creating the elongated shell of dense glowing gas. This structure is embedded inside two larger lobes of gas which were blown off the star at an earlier phase. These lobes are pinched by a ring of denser gas assumed to have been ejected along the orbital plane of the binary companion. (The suspected companion star also might be responsible for a pair of high-speed jets of gas that lie at right angles to the equatorial ring. If the companion were pulling material in a neighboring star, jets escaping along the companion's rotation axis could be produced.) These jets would explain several puzzling features along the periphery of the gas lobes. Much like a stream of water hitting a pile of sand, the jets compress gas ahead of them, creating the curlicue features and bright arcs near the outer edge of the lobes. The twin jets are pointing in different directions than these features. This suggests that the jets are wobbling and turning on and off periodically.
The image of the Cat's Eye Nebula was taken on September 18, 1994 by the NASA Hubble Space Telescope with the Wide Field Planetary Camera-2. It is a composite of three color images taken at different wavelengths.