Molecules can only exist in the atmospheres of very cool stars or in the cooler regions of stars higher in the main sequence, such as in sunspots in our own sun. Most of the observed species are diatomics and are often transitory. Brown dwarfs, on the other hand, can be cool enough to support complex molecules such as methane. Two spectral classes, L (~1300 to ~2000 K) and T (below ~1300 K), have been created for them.

NOTE: Molecule identifications in the table below are intended to be representative, not exhaustive. As with any identification, certainties will vary; a molecule in italic font is a tentative detection. Sources indicate that about 25 species have been identified in the Sun.

See also: The Classification of Stellar Spectra (an informative discussion on star type) and the Wikipedia article on spectral classes.


OBJECT/TYPE MOLECULES
(click for citation)
DISCOVERY/GENERAL CITATION
Sun ("Sol")
(G2V star)
AlH   CaH   CH   CH+
CN   CrH   CuH   H2
H2O   HCl   NH   OH
ScO   SiH   TiH   TiO
ZrO   CO   SH   AlF
On Molecules in Sunspots
H. Wöhl. Solar Phys 16:362 (1971).
DENIS J08173001- 6155158
(T6 brown dwarf)
CH4   H2O   NH3   H2
H2S  
DENIS J081730.0-615520: An Overlooked Mid-T Dwarf in the Solar Neighborhood
É. Artigau, J. Radigan, S. Folkes, R. Jayawardhana, R. Kurtev, D. Lafrenière, R. Doyon, and J. Borissova. ApJL 718:L38 (2010).
ε Indi Ba
(T brown dwarf)
CH4   H2O   CO ε Indi B: A New Benchmark T Dwarf
R. D. Scholz, M. J. McCaughrean, N. Lodieu, and B. Kuhlbrodt. A&A 398:L29 (2003).
IK Tauri
(Mira variable star)
CO   HCN   SiO   SiS
SO   SO2   H2S   NaCl
NS   NO   PO   HCO+
PN   H2O   H2CO   AlOH
AlO   AlCl   (Al2O3)n
AlF
Observations of Extremely Cool Stars
G. Neugebauer, D. E. Martz, and R. B. Leighton. ApJ 142:399 (1965).
IRAS 12311-3509
(N star)
SiC2 IRAS 12311-3509: A Carbon Star with SiC2 Emission
T. Lloyd Evans, M. E. Hurst, and P. J. Sarre. MNRAS 319:111 (2000).
GD 165B
(L brown dwarf)
CrH   FeH The Unique Spectrum of the Brown Dwarf Candidate GD 165B and Comparison to the Spectra of Other Low-Luminosity Objects
J. D. Kirkpatrick, T. J. Henry, and J. Liebert. ApJ 406:701 (1993).
Gliese 229B
(T brown dwarf)
CH4   H2O   CO Discovery of a Cool Brown Dwarf
T. Nakajima, B. R. Oppenheimer, S. R. Kulkarni, D. A. Golimowski, K. Matthews, and S. T. Durrance. Nature 378:463 (1995).
Gliese 570D
(T7.5 brown dwarf)
CH4   H2O   NH3 Discovery of a Brown Dwarf Companion to Gliese 570ABC: A 2MASS T Dwarf Significantly Cooler than Gliese 229B
A. J. Burgasser, J. D. Kirkpatrick, R. M. Cutri, H. McCallon, G. Kopan, J. E. Gizis, J. Liebert, I. N. Reid, M. E. Brown, D. G. Monet, C. C. Dahn, C. A. Beichman, and M. F. Skrutskie. ApJ 531:L57 (2000).
Mira (ο Ceti)
(M star)
TiO   VO   AlF Maxima of ο Ceti and Other Variables
R. O'Halloran. Publ Astron Soc Pac 11:246 (1899).
Proxima Centauri
(M5.5Ve red dwarf)
AlH   A Faint Star of Large Proper Motion
R. T. A. Innes. Circular of the Union Observatory Johannesburg. 30:235 (1915).
R Andromedae
(S star)
CeO   SH Über helle Linien im Spectrum von R Andromedae
T. E. Espin. Astronomische Nachrichten 123:31 (1890).
VY Canis Majoris
(M star, red hypergiant)
AlO   ScO   TiO   VO
NaCl
Cataloged by Lalande 7 March 1801.


Maintained by DE Woon
Updated 21 November 2022