Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Molecules in stars
open-in-new
<h2 id="background">Background</h2> <p><a href="/facts/Matter/osyc04UN">Matter</a> is made up by <a href="/facts/Atom/FoQ4kGN5">atoms</a> (formed by <a href="/facts/Proton/clCjepXP">protons</a> and other <a href="/facts/Subatomic_particle/tMEzcTWQ">subatomic particles</a>). When the environment is right, atoms can join together and form <a href="/facts/Molecules/N9ljSfFq">molecules</a>, which give rise to most materials studied in <a href="/facts/Materials_science/N5HrXRYW">materials science</a>. But certain environments, such as high temperatures, don't allow atoms to form molecules, as the environmental energy exceeds that of the dissociation energy of the bonds within the molecule. Stars have very high temperatures, primarily in their interior, and therefore there are few molecules formed in stars.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p><p>By the mid-18th century, scientists surmised that the source of the Sun's light was <a href="/facts/Incandescence/8Tng7IuE">incandescence</a>, rather than <a href="/facts/Combustion/ohQoWj8z">combustion</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p> <h2 id="evidence-and-research">Evidence and research</h2> <p>Although the <a href="/facts/Sun/CadPCVHh">Sun</a> is a star, its <a href="/facts/Photosphere/32a139LB">photosphere</a> has a low enough temperature of 6,000 K (5,730 °C; 10,340 °F), and therefore molecules can form. <a href="/facts/Water/0lkXnJPK">Water</a> has been found on the Sun, and there is evidence of <a href="/facts/Molecular_hydrogen/BoYHjl0J">H2</a> in <a href="/facts/White_dwarf/gIYlTtrC">white dwarf</a> stellar atmospheres.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>Cooler stars include <a href="/facts/Absorption_band/PgVaAI6j">absorption band</a> spectra that are characteristic of molecules. Similar absorption bands can be found through observation of solar <a href="/facts/Sun_spot/7E8cWSGl">sun spots</a>, which are cool enough to allow persistence of stellar molecules. Molecules found in the Sun include <a href="/facts/Magnesium_monohydride/105ctr2q">MgH</a>, <a href="/facts/Calcium_monohydride/nNTdvFTA">CaH</a>, <a href="/facts/Iron_monohydride/MmRrJG8S">FeH</a>, <a href="/facts/Chromium_monohydride/HqzN6ARY">CrH</a>, <a href="/facts/NaH/Pnsh2T64">NaH</a>, <a href="/facts/Hydroxyl_radical/XafpvqK5">OH</a>, <a href="/facts/Silicon_monohydride/8po80Lxv">SiH</a>, <a href="/facts/Vanadium_monoxide/5b9whSBm">VO</a>, and <a href="/facts/Titanium_monoxide/5ek4Vasd">TiO</a>. Others include <a href="/facts/Cyano_radical/KqvS6uLI">CN</a>, <a href="/facts/Methylidyne/4ExL1FTq">CH</a>, MgF, <a href="/facts/Imidogen/1htMhoq9">NH</a>, <a href="/facts/Dicarbon/T5UcMAev">C2</a>, SrF, <a href="/facts/Zirconium_monoxide/y7gsoQFz">ZrO</a>, <a href="/facts/Yttrium_monoxide/IhTFgFke">YO</a>, ScO, and <a href="/facts/Boron_monohydride/9RMQKgxQ">BH</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>Stars of most types can contain molecules, even the Ap category of <a href="/facts/A-type_main-sequence_star/j859nTAv">A-type stars</a>. Only the hottest O-, B-, and A-type stars have no detectable molecules. Carbon-rich white dwarfs, even though very hot, have spectral lines of <a href="/facts/Dicarbon/T5UcMAev">C2</a> and <a href="/facts/Methylidyne/4ExL1FTq">CH</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h3>Laboratory measurements</h3> <p>Measurements of simple molecules that may be found in stars are performed in laboratories to determine the wavelengths of the spectra lines. Also, it is important to measure the <a href="/facts/Dissociation_energy/wdDb5yHN">dissociation energy</a> and <a href="/facts/Oscillator_strength/78cq9Sff">oscillator strengths</a> (how strongly the molecule interacts with electromagnetic radiation). These measurements are inserted into formula that can calculate the spectrum under different conditions of pressure and temperature. However, man-made conditions are often different from those in stars, because it is hard to achieve the temperatures, and also local thermal equilibrium, as found in stars, is unlikely. Accuracy of oscillator strengths and actual measurement of dissociation energy is usually only approximate.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h3>Model atmosphere</h3> <p>A numerical model of a star's atmosphere will calculate pressures and temperatures at different depths, and can predict the spectrum for different elemental concentrations. </p> <h2 id="application">Application</h2> <p>The molecules in stars can be used to determine some characteristics of the star. The isotopic composition can be determined if the lines in the molecular spectrum are observed. The different masses of different isotopes cause vibration and rotation frequencies to significantly vary. Secondly the temperature can be determined, as the temperature will change the numbers of molecules in the different vibrational and rotational states. Some molecules are sensitive to the ratio of elements, and so indicate elemental composition of the star.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> Different molecules are characteristic of different kinds of stars, and are used to classify them.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Because there can be numerous spectral lines of different strength, conditions at different depths in the star can be determined. These conditions include temperature and speed towards or away from the observer.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>The spectrum of molecules has advantages over atomic spectral lines, as atomic lines are often very strong, and therefore only come from high in the atmosphere. Also the profile of the atomic spectral line can be distorted due to isotopes or overlaying of other spectral lines.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> The molecular spectrum is much more sensitive to temperature than atomic lines.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <h2 id="detection">Detection</h2> <p>The following molecules have been detected in the atmospheres of stars: </p> Two-atom molecules found in stars<table><tbody><tr><th scope="col">Molecule</th><th scope="col">Designation</th></tr><tr><td>AlH<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a></td><td>Aluminium monohydride</td></tr><tr><td>AlO<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a></td><td><a href="/facts/Aluminium_monoxide/JK0YNwcG">Aluminium monoxide</a></td></tr><tr><td>C2<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></td><td><a href="/facts/Diatomic_carbon/T5UcMAev">Diatomic carbon</a></td></tr><tr><td>CH<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a></td><td><a href="/facts/Carbyne/rxFKkHCM">Carbyne</a></td></tr><tr><td>CN<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a></td><td><a href="/facts/Cyanide/t0o8FMKI">Cyanide</a></td></tr><tr><td>CO<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a></td><td><a href="/facts/Carbon_monoxide/CKuLtEMJ">Carbon monoxide</a></td></tr><tr><td>CaCl<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></td><td><a href="/facts/Calcium_chloride/e1EwNPGF">Calcium chloride</a></td></tr><tr><td>CaH<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></td><td><a href="/facts/Calcium_monohydride/nNTdvFTA">Calcium monohydride</a></td></tr><tr><td>CeH<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></td><td>Cerium monohydride</td></tr><tr><td>CeO<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a></td><td>Cerium monoxide</td></tr><tr><td>CoH<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></td><td>Cobalt hydride</td></tr><tr><td>CrH<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a></td><td><a href="/facts/Chromium_hydride/csLDXvV9">Chromium hydride</a></td></tr><tr><td>CuH<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a></td><td><a href="/facts/Copper_hydride/d2S1BQ1M">Copper hydride</a></td></tr><tr><td>FeH<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a></td><td><a href="/facts/Iron_hydride/USA4qHWK">Iron hydride</a></td></tr><tr><td>HCl<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a></td><td><a href="/facts/Hydrogen_chloride/7Wzkhomd">Hydrogen chloride</a></td></tr><tr><td>HF<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a></td><td><a href="/facts/Hydrogen_fluoride/XfQxlqR6">Hydrogen fluoride</a></td></tr><tr><td>H2<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a></td><td><a href="/facts/Molecular_hydrogen/BoYHjl0J">Molecular hydrogen</a></td></tr><tr><td>LaO<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a><a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a></td><td><a href="/facts/Lanthanum_oxide/zUdsqgAx">Lanthanum oxide</a></td></tr><tr><td>MgH<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a></td><td><a href="/facts/Magnesium_monohydride/105ctr2q">Magnesium monohydride</a></td></tr><tr><td>MgO<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a></td><td><a href="/facts/Magnesium_oxide/0GfLn47t">Magnesium oxide</a></td></tr><tr><td>NH<a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a></td><td><a href="/facts/Imidogen/1htMhoq9">Imidogen</a></td></tr><tr><td>NiH<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a></td><td><a href="/facts/Nickel_hydride/CXvq3rjW">Nickel hydride</a></td></tr><tr><td>OH<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a></td><td><a href="/facts/Hydroxide/zW0wxpWD">Hydroxide</a></td></tr><tr><td>ScO<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a></td><td>Scandium oxide</td></tr><tr><td>SiH<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a></td><td><a href="/facts/Silicon_monohydride/8po80Lxv">Silicon monohydride</a></td></tr><tr><td>SiO<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a></td><td><a href="/facts/Silicon_monoxide/Nxr2Q9om">Silicon monoxide</a></td></tr><tr><td>TiO<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a><a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a></td><td><a href="/facts/Titanium_oxide/omkqBeTS">Titanium oxide</a></td></tr><tr><td>VO<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a></td><td><a href="/facts/Vanadium_oxide/eEert9a5">Vanadium oxide</a></td></tr><tr><td>YO<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a><a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a></td><td><a href="/facts/Yttrium_oxide/A7VMIG2D">Yttrium oxide</a></td></tr><tr><td>ZnH<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a></td><td><a href="/facts/Zinc_hydride/WGbfpslo">Zinc hydride</a></td></tr><tr><td>ZrO<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a><a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a></td><td>Zirconium oxide</td></tr></tbody></table> Three-atom molecules found in stars<table><tbody><tr><th scope="col">Molecule</th><th scope="col">Designation</th></tr><tr><td>C3<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a></td><td><a href="/facts/Tricarbon/ow0SCPuE">Tricarbon</a></td></tr><tr><td>HCN<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a><a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a></td><td><a href="/facts/Hydrogen_cyanide/vNtA0Mxe">Hydrogen cyanide</a></td></tr><tr><td>C2H<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a></td><td><a href="/facts/Ethynyl_radical/GSGGV44z">Ethynyl radical</a></td></tr><tr><td>CO2<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a></td><td><a href="/facts/Carbon_dioxide/xGzpppEp">Carbon dioxide</a></td></tr><tr><td>SiC2<a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a></td><td>Silicon dicarbide</td></tr><tr><td>CaNC<a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a></td><td>Calcium isocyanide</td></tr><tr><td>CaOH<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a></td><td><a href="/facts/Calcium_hydroxide/Kz2KzRd8">Calcium hydroxide</a></td></tr><tr><td>H2O<a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a></td><td>Water</td></tr></tbody></table> Four-atom molecules found in stars<table><tbody><tr><th scope="col">Molecule</th><th scope="col">Designation</th></tr><tr><td>C2H2<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a><a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a></td><td><a href="/facts/Acetylene/yaDh6cmJ">Acetylene</a></td></tr></tbody></table> Five-atom molecules found in stars<table><tbody><tr><th scope="col">Molecule</th><th scope="col">Designation</th></tr><tr><td>CH4<a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a></td><td><a href="/facts/Methane/kBHneYnh">Methane</a></td></tr></tbody></table> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Stellar_chemistry/QMkSR5UE">Stellar chemistry</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Masseron, T. (December 2015), "Molecules in stellar atmospheres", in Martins, F.; Boissier, S.; Buat, V.; Cambrésy, L.; Petit, P. (eds.), SF2A-2015: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics, pp. 303–305, Bibcode:2015sf2a.conf..303M <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Stellar Molecules » American Scientist". American Scientist. doi:10.1511/2013.105.403. Archived from the original on 13 August 2016. Retrieved 24 October 2013. {{cite journal}}: Cite journal requires |journal= (help) <a href="https://web.archive.org/web/20160813095727/http://www.americanscientist.org/issues/pub/stellar-molecules" target="_blank">https://web.archive.org/web/20160813095727/http://www.americanscientist.org/issues/pub/stellar-molecules</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Experts Doubt the Sun Is Actually Burning Coal". Scientific American. 1863. Retrieved May 4, 2020. <a href="https://www.scientificamerican.com/article/experts-doubt-the-sun-is-actually-burning-coal/" target="_blank">https://www.scientificamerican.com/article/experts-doubt-the-sun-is-actually-burning-coal/</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Stellar Molecules » American Scientist". American Scientist. doi:10.1511/2013.105.403. Archived from the original on 13 August 2016. Retrieved 24 October 2013. {{cite journal}}: Cite journal requires |journal= (help) <a href="https://web.archive.org/web/20160813095727/http://www.americanscientist.org/issues/pub/stellar-molecules" target="_blank">https://web.archive.org/web/20160813095727/http://www.americanscientist.org/issues/pub/stellar-molecules</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Xu, S.; et al. (2013). "Discovery of Molecular Hydrogen in White Dwarf Atmospheres". The Astrophysical Journal. 766 (2): L18. arXiv:1302.6619. Bibcode:2013ApJ...766L..18X. doi:10.1088/2041-8205/766/2/L18. ISSN 2041-8205. S2CID 119248244. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>McKellar, Andrew (1951). "Molecules in Stellar Atmospheres". Astronomical Society of the Pacific Leaflets. 6 (265): 114. Bibcode:1951ASPL....6..114M. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Symposium, International Astronomical Union; Union, International Astronomical (1987). Astrochemistry. Springer Science & Business Media. p. 852. ISBN 9789027723604. <a href="9789027723604" target="_blank">9789027723604</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Symposium, International Astronomical Union; Union, International Astronomical (1987). Astrochemistry. Springer Science & Business Media. p. 852. ISBN 9789027723604. <a href="9789027723604" target="_blank">9789027723604</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Symposium, International Astronomical Union; Union, International Astronomical (1987). Astrochemistry. Springer Science & Business Media. p. 852. ISBN 9789027723604. <a href="9789027723604" target="_blank">9789027723604</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>McKellar, Andrew (1951). "Molecules in Stellar Atmospheres". Astronomical Society of the Pacific Leaflets. 6 (265): 114. Bibcode:1951ASPL....6..114M. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Symposium, International Astronomical Union; Union, International Astronomical (1987). Astrochemistry. Springer Science & Business Media. p. 852. ISBN 9789027723604. <a href="9789027723604" target="_blank">9789027723604</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Symposium, International Astronomical Union; Union, International Astronomical (1987). Astrochemistry. Springer Science & Business Media. p. 852. ISBN 9789027723604. <a href="9789027723604" target="_blank">9789027723604</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Symposium, International Astronomical Union; Union, International Astronomical (1987). Astrochemistry. Springer Science & Business Media. p. 852. ISBN 9789027723604. <a href="9789027723604" target="_blank">9789027723604</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Briley, Michael M.; Smith, Graeme H. (November 1993). "NH-, CH-, and CN-band strengths in M5 and M13 bright red giants". Astronomical Society of the Pacific. 105 (693): 1260–1268. Bibcode:1993PASP..105.1260B. doi:10.1086/133305. <a href="https://doi.org/10.1086%2F133305" target="_blank">https://doi.org/10.1086%2F133305</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Briley, Michael M.; Smith, Graeme H. (November 1993). "NH-, CH-, and CN-band strengths in M5 and M13 bright red giants". Astronomical Society of the Pacific. 105 (693): 1260–1268. Bibcode:1993PASP..105.1260B. doi:10.1086/133305. <a href="https://doi.org/10.1086%2F133305" target="_blank">https://doi.org/10.1086%2F133305</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Wyckoff, S.; Clegg, R. E. S. (July 1978). "Molecular spectra of pure S stars". Monthly Notices of the Royal Astronomical Society. 184: 127–143. Bibcode:1978MNRAS.184..127W. doi:10.1093/mnras/184.1.127. <a href="https://doi.org/10.1093%2Fmnras%2F184.1.127" target="_blank">https://doi.org/10.1093%2Fmnras%2F184.1.127</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Ayres, T. R.; et al. (March 1981). "Far-Ultraviolet Fluorescence of Carbon Monoxide in the Red Giant Arcturus". Bulletin of the American Astronomical Society. 13: 515. Bibcode:1981BAAS...13..515A. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Jao, W.-C. (December 2011). Johns-Krull, Christopher M.; Browning, Matthew K.; West, Andrew A. (eds.). There is Something About CaH. 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun. Proceedings of a conference held August 28- September 2, 2010 at the University of Washington, Seattle, Washington. ASP Conference Series. Vol. 448. San Francisco: Astronomical Society of the Pacific. p. 907. Bibcode:2011ASPC..448..907J. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Clegg, R. E. S.; Lambert, D. L. (December 1978). "On the identification of FeH and CeO in S stars". Astrophysical Journal, Part 1. 226: 931–936. Bibcode:1978ApJ...226..931C. doi:10.1086/156674. <a href="https://doi.org/10.1086%2F156674" target="_blank">https://doi.org/10.1086%2F156674</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Wyckoff, S.; Clegg, R. E. S. (July 1978). "Molecular spectra of pure S stars". Monthly Notices of the Royal Astronomical Society. 184: 127–143. Bibcode:1978MNRAS.184..127W. doi:10.1093/mnras/184.1.127. <a href="https://doi.org/10.1093%2Fmnras%2F184.1.127" target="_blank">https://doi.org/10.1093%2Fmnras%2F184.1.127</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Clegg, R. E. S.; Lambert, D. L. (December 1978). "On the identification of FeH and CeO in S stars". Astrophysical Journal, Part 1. 226: 931–936. Bibcode:1978ApJ...226..931C. doi:10.1086/156674. <a href="https://doi.org/10.1086%2F156674" target="_blank">https://doi.org/10.1086%2F156674</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Xu, S.; et al. (2013). "Discovery of Molecular Hydrogen in White Dwarf Atmospheres". The Astrophysical Journal. 766 (2): L18. arXiv:1302.6619. Bibcode:2013ApJ...766L..18X. doi:10.1088/2041-8205/766/2/L18. ISSN 2041-8205. S2CID 119248244. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Wyckoff, S.; Clegg, R. E. S. (July 1978). "Molecular spectra of pure S stars". Monthly Notices of the Royal Astronomical Society. 184: 127–143. Bibcode:1978MNRAS.184..127W. doi:10.1093/mnras/184.1.127. <a href="https://doi.org/10.1093%2Fmnras%2F184.1.127" target="_blank">https://doi.org/10.1093%2Fmnras%2F184.1.127</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Bonnell, J. T.; Bell, R. A. (September 1993). "Further Determinations of the Gravities of Cool Giant Stars Using MGI and MGH Features". Monthly Notices of the Royal Astronomical Society. 264 (2): 334. Bibcode:1993MNRAS.264..334B. doi:10.1093/mnras/264.2.334. <a href="https://doi.org/10.1093%2Fmnras%2F264.2.334" target="_blank">https://doi.org/10.1093%2Fmnras%2F264.2.334</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>Wyckoff, S.; Clegg, R. E. S. (July 1978). "Molecular spectra of pure S stars". Monthly Notices of the Royal Astronomical Society. 184: 127–143. Bibcode:1978MNRAS.184..127W. doi:10.1093/mnras/184.1.127. <a href="https://doi.org/10.1093%2Fmnras%2F184.1.127" target="_blank">https://doi.org/10.1093%2Fmnras%2F184.1.127</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>Briley, Michael M.; Smith, Graeme H. (November 1993). "NH-, CH-, and CN-band strengths in M5 and M13 bright red giants". Astronomical Society of the Pacific. 105 (693): 1260–1268. Bibcode:1993PASP..105.1260B. doi:10.1086/133305. <a href="https://doi.org/10.1086%2F133305" target="_blank">https://doi.org/10.1086%2F133305</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> <li id="fn:38"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:38" class="footnote-back-ref">↩</a></p></li> <li id="fn:39"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:39" class="footnote-back-ref">↩</a></p></li> <li id="fn:40"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:40" class="footnote-back-ref">↩</a></p></li> <li id="fn:41"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:41" class="footnote-back-ref">↩</a></p></li> <li id="fn:42"><p>Jorgensen, Uffe G. (April 1994). "Effects of TiO in stellar atmospheres". Astronomy and Astrophysics. 284 (1): 179–186. Bibcode:1994A&A...284..179J. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:42" class="footnote-back-ref">↩</a></p></li> <li id="fn:43"><p>Hauschildt, P.; et al. (2001). Woodward, Charles E.; Bicay, Michael D.; Shull, J. Michael (eds.). Cool Stellar Atmospheres. Tetons 4: Galactic Structure, Stars and the Interstellar Medium. ASP Conference Series. Vol. 231. San Francisco: Astronomical Society of the Pacific. p. 427. Bibcode:2001ASPC..231..427H. ISBN 1-58381-064-1. <a href="1-58381-064-1" target="_blank">1-58381-064-1</a> <a href="#fnref:43" class="footnote-back-ref">↩</a></p></li> <li id="fn:44"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:44" class="footnote-back-ref">↩</a></p></li> <li id="fn:45"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:45" class="footnote-back-ref">↩</a></p></li> <li id="fn:46"><p>Wyckoff, S.; Clegg, R. E. S. (July 1978). "Molecular spectra of pure S stars". Monthly Notices of the Royal Astronomical Society. 184: 127–143. Bibcode:1978MNRAS.184..127W. doi:10.1093/mnras/184.1.127. <a href="https://doi.org/10.1093%2Fmnras%2F184.1.127" target="_blank">https://doi.org/10.1093%2Fmnras%2F184.1.127</a> <a href="#fnref:46" class="footnote-back-ref">↩</a></p></li> <li id="fn:47"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:47" class="footnote-back-ref">↩</a></p></li> <li id="fn:48"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:48" class="footnote-back-ref">↩</a></p></li> <li id="fn:49"><p>Wyckoff, S.; Clegg, R. E. S. (July 1978). "Molecular spectra of pure S stars". Monthly Notices of the Royal Astronomical Society. 184: 127–143. Bibcode:1978MNRAS.184..127W. doi:10.1093/mnras/184.1.127. <a href="https://doi.org/10.1093%2Fmnras%2F184.1.127" target="_blank">https://doi.org/10.1093%2Fmnras%2F184.1.127</a> <a href="#fnref:49" class="footnote-back-ref">↩</a></p></li> <li id="fn:50"><p>Jørgensen, U. G. (January 2003). Hubeny, Ivan; Mihalas, Dimitri; Werner, Klaus (eds.). Molecules in Stellar and Star-Like Atmospheres. Stellar Atmosphere Modeling; Abstracts from a conference held 8-12 April 2002 in Tuebingen, Germany. ASP Conference Proceedings. Vol. 288. San Francisco: Astronomical Society of the Pacific. p. 303. Bibcode:2003ASPC..288..303J. ISBN 1-58381-131-1. <a href="1-58381-131-1" target="_blank">1-58381-131-1</a> <a href="#fnref:50" class="footnote-back-ref">↩</a></p></li> <li id="fn:51"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:51" class="footnote-back-ref">↩</a></p></li> <li id="fn:52"><p>Jørgensen, U. G. (January 2003). Hubeny, Ivan; Mihalas, Dimitri; Werner, Klaus (eds.). Molecules in Stellar and Star-Like Atmospheres. Stellar Atmosphere Modeling; Abstracts from a conference held 8-12 April 2002 in Tuebingen, Germany. ASP Conference Proceedings. Vol. 288. San Francisco: Astronomical Society of the Pacific. p. 303. Bibcode:2003ASPC..288..303J. ISBN 1-58381-131-1. <a href="1-58381-131-1" target="_blank">1-58381-131-1</a> <a href="#fnref:52" class="footnote-back-ref">↩</a></p></li> <li id="fn:53"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:53" class="footnote-back-ref">↩</a></p></li> <li id="fn:54"><p>Cami, J.; et al. (August 2000). "CO2 emission in EP Aqr: Probing the extended atmosphere". Astronomy and Astrophysics. 360: 562–574. Bibcode:2000A&A...360..562C. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:54" class="footnote-back-ref">↩</a></p></li> <li id="fn:55"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:55" class="footnote-back-ref">↩</a></p></li> <li id="fn:56"><p>Cernicharo, J.; et al. (July 2019). "Discovery of the first Ca-bearing molecule in space: CaNC". Astronomy & Astrophysics. 627: 5. arXiv:1906.09352. Bibcode:2019A&A...627L...4C. doi:10.1051/0004-6361/201936040. PMC 6640036. PMID 31327871. L4. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6640036" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6640036</a> <a href="#fnref:56" class="footnote-back-ref">↩</a></p></li> <li id="fn:57"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:57" class="footnote-back-ref">↩</a></p></li> <li id="fn:58"><p>Allard, F.; et al. (May 1994). "The influence of H2O line blanketing on the spectra of cool dwarf stars". The Astrophysical Journal. 426 (1): L39 – L41. Bibcode:1994ApJ...426L..39A. doi:10.1086/187334. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:58" class="footnote-back-ref">↩</a></p></li> <li id="fn:59"><p>Tsuji, T. (1986). "Molecules in stars". Annual Review of Astronomy and Astrophysics. 24: 89–125. Bibcode:1986ARA&A..24...89T. doi:10.1146/annurev.aa.24.090186.000513. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:59" class="footnote-back-ref">↩</a></p></li> <li id="fn:60"><p>Jørgensen, U. G. (January 2003). Hubeny, Ivan; Mihalas, Dimitri; Werner, Klaus (eds.). Molecules in Stellar and Star-Like Atmospheres. Stellar Atmosphere Modeling; Abstracts from a conference held 8-12 April 2002 in Tuebingen, Germany. ASP Conference Proceedings. Vol. 288. San Francisco: Astronomical Society of the Pacific. p. 303. Bibcode:2003ASPC..288..303J. ISBN 1-58381-131-1. <a href="1-58381-131-1" target="_blank">1-58381-131-1</a> <a href="#fnref:60" class="footnote-back-ref">↩</a></p></li> <li id="fn:61"><p>Jørgensen, U. G. (January 2003). Hubeny, Ivan; Mihalas, Dimitri; Werner, Klaus (eds.). Molecules in Stellar and Star-Like Atmospheres. Stellar Atmosphere Modeling; Abstracts from a conference held 8-12 April 2002 in Tuebingen, Germany. ASP Conference Proceedings. Vol. 288. San Francisco: Astronomical Society of the Pacific. p. 303. Bibcode:2003ASPC..288..303J. ISBN 1-58381-131-1. <a href="1-58381-131-1" target="_blank">1-58381-131-1</a> <a href="#fnref:61" class="footnote-back-ref">↩</a></p></li> </ol>