✣ Cosmic Butterflies - bipolar planetary nebulae ✣ Astronomers have used the NASA/ESA Hubble Space Telescope and ESOs New Technology Telescope to explore more than 100 planetary nebulae in the central bulge of our galaxy. They have found that butterfly-shaped members of this cosmic family tend to be mysteriously aligned — a surprising result given their different histories and varied properties. The final stages of life for a star like our Sun result in the star puffing its outer layers out into the surrounding space, forming objects known as planetary nebulae in a wide range of beautiful and striking shapes. One type of such nebulae, known as bipolar planetary nebulae, create ghostly hourglass or butterfly shapes around their parent stars. All these nebulae formed in different places and have different characteristics. Neither the individual nebulae, nor the stars that formed them, interact with other planetary nebulae. However, a new study by astronomers from the University of Manchester, UK, now shows surprising similarities between some of these nebulae: many of them line up in the sky in the same way! This really is a surprising find and, if it holds true, a very important one, explains Bryan Rees of the University of Manchester... Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy. By using images from both Hubble and the NTT we could get a really good view of these objects, so we could study them in great detail. While two of these populations were completely randomly aligned in the sky, as expected, we found that the third — the bipolar nebulae — showed a surprising preference for a particular alignment,...While any alignment at all is a surprise, to have it in the crowded central region of the galaxy is even more unexpected. The alignment were seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge, explains Rees. For them to line up in the way we see, the star systems that formed these nebulae would have to be rotating perpendicular to the interstellar clouds from which they formed, which is very strange. While the properties of their progenitor stars do shape these nebulae, this new finding hints at another more mysterious factor. Along with these complex stellar characteristics are those of our Milky Way; the whole central bulge rotates around the galactic centre. This bulge may have a greater influence than previously thought over our entire galaxy — via its magnetic fields. The astronomers suggest that the orderly behaviour of the planetary nebulae could have been caused by the presence of strong magnetic fields as the bulge formed. Source; spacetelescope.org/news/heic1316/ sci.esa.int/hubble/52821-a-selection-of-hubbles-planetary-nebulae/ Image; Row 1 (from upper left): NGC 6302, NGC 6881, NGC 5189 Row 2 (from lower left) : M2-9, Hen 3-1475, Hubble 5 ESA/Hubble & NASA NGC 6302: NASA
Posted on: Mon, 10 Mar 2014 06:10:11 +0000
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