Electronic Resource
A close halo of large transparent grains around extreme red giant stars
| العنوان: | A close halo of large transparent grains around extreme red giant stars |
|---|---|
| المؤلفون: | Norris, Barnaby R M, Tuthill, Peter G, Ireland, Michael, Lacour, Sylvestre, Zijlstra, Albert A, Lykou, Foteini, Evans, Thomas M, Stewart, Paul, Bedding, Timothy Russell |
| المصدر: | Nature |
| بيانات النشر: | Macmillan Publishers Ltd 2012 |
| نوع الوثيقة: | Electronic Resource |
| مستخلص: | An intermediate-mass star ends its life by ejecting the bulk of its envelope in a slow, dense wind. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure, entraining the gas and driving the wind. Explaining the amount of mass loss, however, has been a problem because of the difficulty of observing tenuous gas and dust only tens of milliarcseconds from the star. For this reason, there is no consensus on the way sufficient momentum is transferred from the light from the star to the outflow. Here we report spatially resolved, multiwavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the Hertzsprung-Russell diagram. When imaged in scattered light, dust shells were found at remarkably small radii (less than about two stellar radii) and with unexpectedly large grains (about 300 nanometres in radius). This proximity to the photosphere argues for dust species that are transparent to the light from the star and, therefore, resistant to sublimation by the intense radiation field. Although transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains through photon scattering rather than absorption-a plausible mass loss mechanism for lower-amplitude pulsating stars. |
| مصطلحات الفهرس: | Keywords: absorption; acceleration; amplitude; atmospheric gas; condensation; cool water; dust; pressure effect; radiation balance; transparency; wavelength; altitude; article; astronomy; dust; environmental radioactivity; light scattering; priority journal; radiat, Journal article |
| URL: | |
| الاتاحة: | Open access content. Open access content |
| Other Numbers: | AUANP oai:openresearch-repository.anu.edu.au:1885/66081 0028-0836 1291792865 |
| المصدر المساهم: | AUSTRALIAN NAT UNIV - PRINT REPOSITORY From OAIster®, provided by the OCLC Cooperative. |
| رقم الانضمام: | edsoai.on1291792865 |
| قاعدة البيانات: | OAIster |
| الوصف غير متاح. |