Our sun will not explode as a powerful supernova when it eventually runs out of fuel, but that doesn't mean there won't be fireworks.
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When our sun runs out of hydrogen fuel in its core, the star will puff up into a huge red giant and torment itself with powerful stellar winds, eventually stripping its self bare, creating a vast planetary nebula with a small yet dense white dwarf in its core.
Until now, this progression from dying star to nebula has been assumed to be a slow and fairly ‘gentle' process - when compared with the sheer violence of a massive star's supernova at least. A new study published in The Astrophysical Journal, however, suggests that the death of low to intermediate mass stars (like the sun) is anything but subdued.
"In a few thousand million years, the sun will exhaust its nuclear fuel, expand into a red giant and eject a major part of its mass," said lead researcher José Francisco Gómez, of the Institute of Astrophysics of Andalusia (IAA-CSIC) in Granada, Spain. "The final result will be a white dwarf surrounded by a glowing planetary nebula. Even though every star with a mass below ten solar masses goes through this short but important final transition, many details of the process still evade us."
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Gómez's team's research focused on IRAS 15103-5754, an object that is currently transitioning from a red giant into a planetary nebula. Nicknamed "water fountains," objects like IRAS 15103-5754 generate powerful emissions produced by water vapor molecules (known as water maser emission). Jets of ejected material can therefore be detected and their outflow speeds measured.
As a part of a wider survey of 16 dying stars, IRAS 15103-5754 stands out as the velocity of its jets increases with distance from the central star. And this provides an interesting clue as to the dynamics of planetary nebulae and how stars like our sun die.
"Water molecules are generally destroyed soon after the planetary nebula is formed, and in the rare cases where a maser emission has been detected, the velocity has always been very low," said collaborator Luis F. Miranda, of the IAA-CSIC and University of Vigo, Spain. "In IRAS 15103-5754 we are seeing for the first time a water maser emission at velocities of hundreds of kilometers (miles) per second. We are witnessing the transition of a star into a planetary nebula in real time."
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"The high velocity can only be explained by the occurrence of an explosion," said Gómez. "Our results show that, contrary to the most widespread theories, when a star turns into a planetary nebula an enormous explosion is produced - short-lived but highly energetic - which will determine the evolution of the star in its last phases of life."
As we look deep into our galaxy, an array of planetary nebulae of a variety of morphologies have been observed, a fact that isn't easily explained by current theories. Now that astronomers are revealing the formation of these nebulae may be more violent than previously thought, perhaps we'll have a better grasp on what dynamics drive the death of stars like our sun and why planetary nebulae are so varied.
Source: Institute of Astrophysics of Andalusia