Titanium Carbide Nanocrystals in Circumstellar Environments
G. von Helden,
12*
A.
G. G. M. ,
Tielens,
3
D. van Heijnsbergen,
12
M.
A. Duncan,
4
S. Hony,
5
L. B. F. M. Waters,
56
G. Meijer
12
Meteorites contain micrometer-sized graphite grains with
embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there
is no direct observational identification of these grains in
astronomical sources. We report that infrared wavelength spectra of
gas-phase titanium carbide nanocrystals derived in the laboratory show
a prominent feature at a wavelength of 20.1 micrometers, which compares
well to a similar feature in observed spectra of postasymptotic giant
branch stars. It is concluded that titanium carbide forms during a
short (approximately 100 years) phase of catastrophic mass loss
(>0.001 solar masses per year) in dying, low-mass stars.
1 FOM Institute for Plasma Physics Rijnhuizen,
Edisonbaan 14, NL-3430 BE Nieuwegein, Netherlands.
2 Department of Molecular and Laser Physics,
University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen,
Netherlands.
3 SRON/Kapteyn Institute, University of
Groningen, Landleven 12, NL-9700 AV Groningen, Netherlands.
4 Department of Chemistry, University of Georgia,
Athens, GA 30602, USA.
5 Astronomical Institute,
University of Amsterdam, Kruislaan 403, NL-1098 SJ Amsterdam,
Netherlands.
6 Instituut voor Sterrenkunde,
Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 B-Heverlee,
Belgium.
*
To whom correspondence should be addressed. E-mail:
gertvh{at}rijnh.nl
