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천문우주과학 연구동향

천문우주과학과 관련된 국내외 상위 학술논문 및 특허 정보를 제공해 드립니다.

백만년 이상의 태양 유사항성을 형성하는 구름 핵

H2D+ observations give an age of at least one million years for a cloud core forming Sun-like stars
  • 작성자 : KASI
  • 작성일 : 2014-12-15
  • 조회수 : 3522
  • 저자andra Brünken, Olli Sipilä, Edward T. Chambers et. al
  • Absract


    The age of dense interstellar cloud cores, where stars and planets form, is a crucial parameter in star formation and difficult to measure. Some models predict rapid collapse whereas others predict timescales of more than one million years . One possible approach to determining the age is through chemical changes as cloud contraction occurs, in particular through indirect measurements of the ratio of the two spin isomers (ortho/para) of molecular hydrogen, H2, which decreases monotonically with age. This has been done for the dense cloud core L183, for which the deuterium fractionation of diazenylium (N2H+) was used as a chemical clock to infer that the core has contracted rapidly (on a timescale of less than 700,000 years). Among astronomically observable molecules, the spin isomers of the deuterated trihydrogen cation, ortho-H2D+ and para-H2D+, have the most direct chemical connections to H2 and their abundance ratio provides a chemical clock that is sensitive to greater cloud core ages. So far this ratio has not been determined because para-H2D+ is very difficult to observe. The detection of its rotational ground-state line has only now become possible thanks to accurate measurements of its transition frequency in the laboratory, and recent progress in instrumentation technology. Here we report observations of ortho- and para-H2D+ emission and absorption, respectively, from the dense cloud core hosting IRAS 16293-2422 A/B, a group of nascent solar-type stars (with ages of less than 100,000 years). Using the ortho/para ratio in conjunction with chemical models, we find that the dense core has been chemically processed for at least one million years. The apparent discrepancy with the earlier N2H+ work arises because that chemical clock turns off sooner than the H2D+ clock, but both results imply that star-forming dense cores have ages of about one million years, rather than 100,000 years.


  • 게재정보NATURE(2014.12.06)에 게재된 논문임
  • 첨부파일
  • 원 문http://www.nature.com/nature/journal/v516/n7530/full/nature13924.html
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