Dying stars that are among the most beautiful objects in the universe tend to line up across the night sky, and astronomers aren't sure why.
These "cosmic butterflies" - actually a certain type of planetary nebula - all have their own formation histories, and they don't interact with each other. But something is apparently making them dance in step, scientists using NASA's Hubble Space Telescope and the European Southern Observatory's New Technology Telescope (NTT) have discovered.
"This really is a surprising find and, if it holds true, a very important one,"study lead author Bryan Rees, of the University of Manchester in the United Kingdom, said in a statement. "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."
© ESA/Hubble & NASA; NGC 6302: NASA, ESA and the Hubble SM4 ERO Team; NGC 6881: ESA/Hubble & NASA; NGC 5189: NASA, ESA and the Hubble Heritage Team (STScI/AURA);M2-9: Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands)
This mosaic shows a selection of stunning images of bipolar planetary nebulae taken by Hubble. Row 1 (from upper left): NGC 6302, NGC 6881, NGC 5189 Row 2 (from lower left) : M2-9, Hen 3-1475, Hubble 5. Image released Sept. 4, 2013.
In the final stages of their lives, stars like our own sun puff their outer layers into space, creating strange and striking objects known as planetary nebulas. (No planets are necessarily involved. The term was coined by famed astronomer Sir William Herschel to describe celestial bodies that appeared to have circular, planet-like shapes when viewed through early telescopes.)
They found most of these objects to be scattered more or less randomly across the sky, but one type - the bipolar nebulae, which have distinctive butterfly or hourglass shapes that are thought to result when jets blast material away from a dying star perpendicular to its orbit - showed a surprising alignment ( via livescience.com ).
"The alignment we're seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge,"Rees said. "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."