New data from the Hubble Space Telescope and the Herschel Space Observatory have provided new insights into the shape and structure of the far-off Ring Nebula—whose fate has important ramifications for the future of our own Sun—and may have begun the process of explaining how large galaxies grew in size over three billion years ago.
The Ring Nebula, which lies about 2,000 light-years from Earth and measures about 1 light-year in diameter, is a popular target for amateur astronomers, as it was for Hubble scientists. Located in the constellation of Lyra (“the Lyre”), the nebula now appears not to be bagel-shaped, but something akin in appearance to “a jelly doughnut,” according to investigator C. Robert O’Dell of Vanderbilt University in Nashville, Tenn. Images acquired by Hubble’s Wide Field Camera-3 have enabled his team to develop the most comprehensive three-dimensional model of the Ring Nebula ever assembled.
The nebula is tilted toward us, thereby enabling astronomers to view the ring face-on, and a knotty blue mixture of gaseous material, not dissimilar in shape to a football, is clearly visible in the center. The “ends” of the football protrude from opposite sides of the ring, and O’Dell’s team have seen tentacles of gas, formed by expanding hot gas pushed into cold gas previously ejected by its dying progenitor star. And upon this star there hangs a lesson for the future of our own Sun. Now little more than a white dwarf, it has long since exhausted its hydrogen supply, shed its outer gaseous layers, and gravitationally collapsed … all of which took place more than 4,000 years ago.
It is believed that after its “main stage” of evolution, the Ring’s star ballooned into a red giant, then began the process of gravitational collapse. At the peak of its evolution, it was probably several times more massive than our Sun, but would seem to have followed a similar old age profile to that which our Solar System’s progenitor is expected to follow in about 6 billion years’ time. However, the less-massive nature of our Sun suggests that it will not suffer such a dramatic death. “When the sun becomes a white dwarf, it will heat more slowly after it ejects its outer gaseous layers,” O’Dell said. “The material will be farther away once it becomes hot enough to illuminate the gas. This larger distance means the sun’s nebula will be fainter because it is more extended.”
Looking still further back in time—and far into the cosmos—the Herschel data focuses upon a rare and massive merger between two galaxies and would seem to offer evidence to settle a long-held mystery about how quickly they developed around 3-4 billion years ago. Opposing points of view were that they built up over time, via the acquisition of smaller galaxies, or that they formed more rapidly through powerful collisions between two large galaxies. The Herschel results—reinforced by Hubble and Spitzer Space Telescope observations—seem to suggest that massive mergers are responsible for giant elliptical galaxies. “We’re looking at a younger phase in the life of these galaxies—an adolescent burst of activity that won’t last very long,” said Hai Fu of the University of California at Irvine, who is lead author of a new study describing the results.
The galaxies under observation are known as HXMM01 and reside about 11 billion light-years from Earth, during a time when the Universe was about 3 billion years old. Unlike our Milky Way, which generates the equivalent of 2-3 stars each year, HXMM01 churns out around 2,000 new stars per day, with the total across both colliding galaxies of about 400 billion stars. The results go against the more popular model explaining how the biggest galaxies arise: through minor acquisitions of small galaxies. “Instead,” noted NASA, “mega smash-ups may be doing the job.”
Want to keep up-to-date with all things space? Be sure to “Like” AmericaSpace on Facebook and follow us on Twitter:@AmericaSpace