Identification of phosphorus monoxide (x2iir) in vy canis majoris: Detection of the first pio bond in space

E. D. Tenenbaum, N. J. Woolf, L. M. Ziurys

Research output: Contribution to journalArticlepeer-review

110 Scopus citations


A new interstellar molecule, PO (X 2IIr), has been detected toward the envelope of the oxygen-rich supergiant star VY Canis Majoris (VY CMa) using the Submillimeter Telescope of the Arizona Radio Observatory. The J p 5.5 → 4.5 and J = 6.5 → 5.5 rotational transitions of PO at 240 and 284 GHz were observed, each of which consisted of well-defined lambda-doublets. The line profiles are roughly parabolic in shape, analogous to PN, and suggest that this species arises from the spherical wind in VY CMa, as opposed to the collimated blue- and redshifted outflows. Comparison of line intensities indicates that PO arises from a confined source roughly 1″ in extent, with a column density of Ntot ≈ 2.8 # 1015 cm-2, which corresponds to a fractional abundance of/∼ 9 × 10-8, relative to H2. Consequently, PO and PN have similar concentrations in VY CMa, a result not predicted by either LTE or kinetic models of circumstellar chemistry. These phosphorus compounds may arise from shock-induced reactions in this active envelope. Phosphorus monoxide is the first interstellar molecule detected that contains a P - O bond, a moiety essential in biochemical compounds. It is also the first new species to be identified in an oxygen-rich, as opposed to a carbon-rich, circumstellar envelope.

Original languageEnglish (US)
Pages (from-to)L29-L32
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - 2007


  • Astrobiology
  • Astrochemistry
  • Circumstellar matter
  • ISM: Molecules
  • Radio lines: Stars
  • Stars: Individual (VY Canis Majoris)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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