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Astronomers using the NASA\/ESA\/CSA James Webb Space Telescope have identified two stars responsible for generating carbon-rich dust a mere 5000 light-years away in our own Milky Way galaxy. As the massive stars in Wolf-Rayet 140 swing past one another on their elongated orbits, their winds collide and produce the carbon-rich dust. For a few months every eight years, the stars form a new shell of dust that expands outward \u2014 and may eventually go on to become part of stars that form elsewhere in our galaxy.<\/p>\n
Astronomers have long tried to track down how elements like carbon, which is essential for life, become widely distributed across the Universe. Now, the James Webb Space Telescope has examined one ongoing source of carbon-rich dust in our own Milky Way galaxy in greater detail: Wolf-Rayet 140\u00a0[1], a system of two massive stars that follow a tight, elongated orbit.<\/p>\n
As they swing past one another (within the central white dot in the Webb images), the stellar winds from each star slam together, the material compresses, and carbon-rich dust forms. Webb\u2019s latest observations show 17 dust shells shining in mid-infrared light that are expanding at regular intervals into the surrounding space.<\/p>\n
\u201cThe telescope confirmed that these dust shells are real, and its data also showed that the dust shells are moving outward at consistent velocities, revealing visible changes over incredibly short periods of time,\u201d<\/i>\u00a0said Emma Lieb, the lead author of the new paper and a doctoral student at the University of Denver in Colorado.<\/p>\n
Every shell is racing away from the stars at more than 2600 kilometres per second, almost 1% the speed of light.\u00a0\u201cWe are used to thinking about events in space taking place slowly, over millions or billions of years,\u201d<\/i>\u00a0added Jennifer Hoffman, a co-author and a professor at the University of Denver.\u00a0\u201cIn this system, the observatory is showing that the dust shells are expanding from one year to the next.\u201d<\/i><\/p>\n
\u201cSeeing the real-time movement of these shells between Webb\u2019s observations that were taken only 13 months apart is truly remarkable,\u201d<\/i>\u00a0said Olivia Jones, a co-author at the UK Astronomy Technology Centre, Edinburgh.\u00a0\u201cThese new results are giving us a first glimpse of the potential role of such massive binaries as factories of dust in the Universe.\u201d<\/i><\/p>\n
Like clockwork, the stars\u2019 winds generate dust for several months every eight years, as the pair make their closest approach during a wide, elongated orbit. Webb also shows where dust formation stops \u2014 look for the darker region at top left in both images.<\/p>\n
The telescope\u2019s mid-infrared images detected shells that have persisted for more than 130 years (older shells have dissipated enough that they are now too dim to detect). The researchers speculate that the stars will ultimately generate tens of thousands of dust shells over hundreds of thousands of years.<\/p>\n
\u201cMid-infrared observations are absolutely crucial for this analysis, since the dust in this system is fairly cool. Near-infrared and visible-light observations would only show the shells that are closest to the star,\u201d\u00a0<\/i>explained Ryan Lau, a co-author and astronomer at NSF NOIRLab in Tucson, Arizona, who led the\u00a0initial research\u00a0about this system.\u00a0\u201cWith these incredible new details, the telescope is also allowing us to study exactly when the stars are forming dust \u2014 almost to the day.\u201d<\/i><\/p>\n
The distribution of the dust isn\u2019t uniform. Though these differences aren\u2019t obvious in Webb\u2019s images, the team found that some of the dust has \u2018piled up\u2019, forming amorphous, delicate clouds that are as large as our entire Solar System. Many other individual dust particles float freely. Every speck is as small as one-hundredth the width of a human hair. Clumpy or not, all of the dust moves at the same speed and is carbon rich.<\/p>\n
The future of this system<\/p>\n
What will happen to these stars over millions or billions of years, after they have finished \u2018spraying\u2019 their surroundings with dust? The\u00a0Wolf-Rayet star\u00a0in this system is 10 times more massive than the Sun and nearing the end of its life. In its final \u2018act\u2019, this star will either explode as a\u00a0supernova\u00a0\u2014 possibly blasting away some or all of the dust shells \u2014 or collapse into a\u00a0black hole, which would leave the dust shells intact.<\/p>\n
Though no one can predict with any certainty what will happen, researchers are rooting for the black hole scenario.\u00a0\u201cA major question in astronomy is, where does all the dust in the universe come from?\u201d<\/i>\u00a0Lau said.\u00a0\u201cIf carbon-rich dust like this survives, it could help us begin to answer that question.\u201d<\/i><\/p>\n
\u201cWe know carbon is necessary for the formation of rocky planets and solar systems like ours,\u201d\u00a0<\/i>Hoffman added. \u201cIt\u2019s exciting to get a glimpse into how binary star systems not only create carbon-rich dust, but also propel it into our galactic neighborhood<\/i>.\u201d<\/p>\n
These results have been published in the\u00a0Astrophysical Journal Letters<\/i>\u00a0and were presented in a press conference at the 245th meeting of the American Astronomical Society in National Harbor, Maryland.<\/p>\nNotes<\/h4>\n
[1]\u00a0A Wolf-Rayet star is born with at least 25 times more mass than our Sun and is nearing the end of its life, when it will likely collapse directly to black hole, or explode as a supernova. Burning hotter than in its youth, a Wolf-Rayet star generates powerful winds that push huge amounts of gas into space. The Wolf-Rayet star in this particular pair may have shed more than half its original mass via this process.<\/p>\n
Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope\u2019s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.<\/p>\n
Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).<\/p>\n<\/p><\/div>\n