Marcetta Y. Darensbourg

Last updated
Marcetta Y. Darensbourg
Born
Marcetta Bernice York
Alma mater Union College B.S. (1963)
University of Illinois Ph.D. (1967)
Spouse Donald J. Darensbourg
Scientific career
Institutions Vassar College (1967–1969)

Tulane University (1971–1982)

Texas A&M University (1982–present)
Thesis Kinetic studies of some organolithium reactions  (1967)
Doctoral advisor Theodore L. Brown

Marcetta York Darensbourg is an American inorganic chemist. She is a Distinguished Professor of Chemistry at Texas A&M University. Her current work focuses on iron hydrogenases and iron nitrosyl complexes.

Contents

Early life

Marcetta Bernice (York) Darensbourg was born May 4, 1942, in Artemus, Kentucky. She is daughter to school teachers, Atlas H. York, and Elsie Walton York. She has an older sister named Mary Lucille York, and a younger brother named Larry Hercules York. Darensbourg attended a local high school named Knox Central High School in Barbourville, Kentucky. In high school, she was a studious pupil and was a member of the band, choir, and cheerleading team. This is where Darensbourg met her role model, Mrs. Bolton. Mrs. Bolton taught biology, physics, and chemistry which interested Darensbourg. One of the reasons Darensbourg wanted to go into science and teach was from the great influence that Mrs. Bolton left on her. [1]

Education

Darensbourg received a B.S. in Chemistry from Union College in 1963, and a Ph.D. in inorganic chemistry from the University of Illinois under the guidance of Theodore L. Brown in 1967. [1] Her doctoral work focused on the kinetic studies of organolithium reactions. [2]

Career

Darensbourg was an assistant professor at Vassar College from 1967to 1969. From 1971 to 1982, she taught at Tulane University, attaining the rank of professor. In 1982, Marcetta Darensbourg was appointed professor at Texas A&M University together with Donald J. Darensbourg. She was subsequently awarded the title of Distinguished Professor in 2010. [3] Her research interests include bimetallic hydrogenase enzymes containing CO and CN ligands.

Darensbourg is a member of the board of Inorganic Syntheses , [4] where she also served as the editor-in-chief of volume 32. [5] In 2011, she was elected fellow of the American Academy of Arts and Sciences. [6]

Research projects

Organolithium chemistry

Darensbourg investigated certain kinetic aspects of organolithium compounds. During the course of these studies, the kinetics of the rate-determining step of tert-butyllithium dissociation from tetramer to a dimer were analyzed. [7] Using 7Li nuclear magnetic resonance (NMR), the study delineates the rate-determining step of the equilibrium of the tert-butyllithium mixture, revealing that the dissociation from tetramer to dimer is key. Notably, the dissociation rate was found to be significantly affected by the solvent used, and the dissociation rate of toluene was significantly faster than cyclopentane. The findings also highlight the role of stereoconfiguration in these reactions, where tert-butyllithium exhibits a uniquely slow intermolecular exchange rate compared to other alkyl lithium compounds due to its larger size. It has been observed that the presence of even a small number of bases like triethylamine greatly accelerates the exchange rate. [7] Using mass spectroscopy, the existence of cross-association with other organolithium species in the vapor phase could also be observed. [7]

Example of Iron Dithiolates Ligand Formation Iron dithiolate ligand formation.jpg
Example of Iron Dithiolates Ligand Formation

Metal carbonyl chemistry

Darensbourg's interest in charge distribution molecules that could be probed with reactivity led to her work on mapping nucleophilic attack on metal carbonyls. Infrared, nuclear magnetic resonance and electronic spectroscopy of some carbene pentacarbonyl complexes of chromium(0) and tungsten(0) indicated that carbene ligands are better sigma donors than a carbonyl ligand, while simultaneously behaving as strong pi acceptors. [8] Substitutions of iron and cobalt sites were made to see how the CO strength force constants affected the nucleophilic attacks. The substitutions illustrated that the nucleophilic attacks always occurred at the CO group with the greater force constant when there is a choice of carbonyl groups present in a molecule. [9]

Hydrogenase mimics

Darensbourg has pioneered the development of synthetic mimics of hydrogenase enzymes. These include synthetic complexes featuring Fe-based organometallics species, which serve as precursor for producing iron only Hydrogenase enzyme active site. These enzymes are capable of carry out reaction even in the absence of the protein-based active site organization [10] or carry out the proton production with high efficiencies. However, these hydrogenase enzymes were found to be highly sensitive with oxygen (O2), which can over oxidize and inactivate them. Even after the oxygen was removed, they do not regain catalytic activity immediately, requiring multiple steps to do so. [11]

In 2020, Darensbourg et al. reported a variety of characterizations of Ni-Fe based hydrogenase species, which eventually encounter oxygen damage during their lifetime. Although some hydrogenase catalysts remain tolerant to oxygen damage, a majority of such catalysts typically undergo irreversible damage upon exposure. Darensbourg et al. reported an overview of sustainable water splitting technologies in which the hydrogenase species can be reductively repaired. Modifications of single atoms within hydrogenase active sites allowed for customizable activities, oxygen tolerance, and structures of the catalysts, permitting practical applications of enzymes and fragile biomimetrics of the active sites. Studies of a [NiFeSe]-H2ase active site presented new applications for selenium in hydrogenase enzymes, as the complex exhibited a high hydrogen-processing catalytic ability and a relatively quick recovery from oxygen damage. [12]

Metallodithiolates chemistry

Examples of Nickel and Palladium Dithiolates Ligands Wiki Figure-2.jpg
Examples of Nickel and Palladium Dithiolates Ligands

In the beginning of 2017, Darensbourg shifted her focus to studying the metallodithiolates ligands, which act as building blocks for the synthesis of various bimetallic enzyme active sites. The ligands can act as a catalyst to carry out different reactions, depending on which transition metal being at the center. [13]

Darensbourg et al. reported that metallodithiolates ligands with nickel centers can increase the electron density of bonds such as Fe-S, allowing them to be cleaved easily. [14] Darensbourg et al. also determined that this nickel center complex associated with a lead atom also plays an important role in the addition of CO and ethylene in the Suzuki-Miyaura reaction, which couples the organic compounds of boron and the halides, along alkyl halides and alkylboranes. [15] Furthermore, with the cCobalt center, the metallodithiolates ligands can catalyze the transfer of NO and nitrosylate moieties, which allows the glycosidase conjugation of dinitrosyl iron complexes. With this conjugation, other carbohydrates can achieve higher potential in attaching for drug delivery. [7]

Molecular Magnetism

In 2023, Darensbourg began exploring metallodithiolates in the field of molecular magnetism. Seeing that few publications had reported analyses of metal-based linkers with sulfur bridge ligands, Darensbourg et al. characterized a paramagnetic nitrosylated iron complex with N2S2 ligands. [16]

In the complex, the [Fe(NO)]2+ unit lies centered above the N2S2 field, exhibiting strong antiferromagnetic coupling to triplet NO-. Density Functional Theory (DFT) computations indicate that the Fe spin stabilizes by delocalizing onto the surrounding dithiolate sulfurs. [17] In expectation of spin delocalization of bimetallic derivatives upon interactions with sulfur, Darensbourg et al. performed syntheses of various sulfur-bridged multimetallic complexes. [16]

Darensbourg et al. reported that reactions of the paramagnetic (NO)Fe(N2S2) with [M(CH3CNn][BF4]2 salts forms a stairstep bond arrangement with square planar MS4 conformations. Reactions of the nitrosylated iron complex were conducted with metal salts composed of NiII, PdII, and PtII. Darensbourg et al. reported that each tri-metallic complex demonstrated similar nitrosyl stretching values in IR spectroscopy despite differences in magnetic properties. Magnetic susceptibility and DFT calculations additionally showed that each of the {Fe(NO)}7 units exhibited antiferromatic coupling and that each N2S2 ligand engaged in a superexchange interaction with the bimetallic derivatives. The interactions presented by each metal ion displayed a trend of increasing covalency in the order of NiII << PdII << PtII. Upon comparisons of the coupling strengths of each Nickel-sulfur-bridged multimetallic complex, Darensbourg et al. concluded that the antiferromatic coupling of each Fe(NO) spin center was facilitated by an intricate d-orbital overlap with the NI2S2 plane. [16]

Darensbourg et al. explained that the antiferromatic coupling of Fe(NO) presented new strategies for obtaining strong magnetic exchange within metallodithiolate complex through 4d and 5d orbital interactions. In place of steric effects, differences in the metal ion identity play roles in the electronic effects of each metal-sulfur magnetic interaction. Through combinations of various paramagnetic metallodithiolate donors and metal receivers, a vast collection of thiolate-bridged multimetallic complexes can be prepared with different magnetic communication strengths. [16]

The wide variety of possible sulfur-bridged multimetallic complexes presents many opportunities for bioinorganic chemistry. Darensbourg et al. indicated potential for the development of nd-4f complexes, of which some can be used as single-molecule magnets. Interactions between orbitals with even higher energies allows for the customization of modern biocatalysts in evolutionary biology. [16] The improved tunability of such biocatalysts enables the synthesis of catalysts exhbiting long-term sustainability. [17]

Awards

Most recently, Darensbourg has been awarded with the American Chemical Society Willard Gibbs Medal Award, a highly prestigious award recognizing the contributions of a chemist to the field. [18] In 2018, Darensbourg was recognized as the SEC professor of the year. [19] Darensbourg was also awarded the American Chemical Society Award in Organometallic Chemistry in 2017 for her application of organometallic chemistry to hydrogenase enzyme active sites and synthetic analogues. [20] In 2016, Darensbourg received awards for her teaching and mentoring abilities at both Texas A&M University and UCLA. [21]

Voices of Inorganic Chemistry Interview - Donald J. Darensbourg and Marcetta Y. Darensbourg (YouTube link)

Related Research Articles

<span class="mw-page-title-main">Inorganic chemistry</span> Field of chemistry

Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the chemical industry, including catalysis, materials science, pigments, surfactants, coatings, medications, fuels, and agriculture.

<span class="mw-page-title-main">Organometallic chemistry</span> Study of organic compounds containing metal(s)

Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide, cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry.

Ferrocene is an organometallic compound with the formula Fe(C5H5)2. The molecule is a complex consisting of two cyclopentadienyl rings sandwiching a central iron atom. It is an orange solid with a camphor-like odor that sublimes above room temperature, and is soluble in most organic solvents. It is remarkable for its stability: it is unaffected by air, water, strong bases, and can be heated to 400 °C without decomposition. In oxidizing conditions it can reversibly react with strong acids to form the ferrocenium cation Fe(C5H5)+2. Ferrocene and the ferrocenium cation are sometimes abbreviated as Fc and Fc+ respectively.

<span class="mw-page-title-main">Organolithium reagent</span> Chemical compounds containing C–Li bonds

In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.

In organometallic chemistry, acetylide refers to chemical compounds with the chemical formulas MC≡CH and MC≡CM, where M is a metal. The term is used loosely and can refer to substituted acetylides having the general structure RC≡CM. Acetylides are reagents in organic synthesis. The calcium acetylide commonly called calcium carbide is a major compound of commerce.

<span class="mw-page-title-main">Metal carbonyl</span> Coordination complexes of transition metals with carbon monoxide ligands

Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel tetracarbonyl is used to produce pure nickel. In organometallic chemistry, metal carbonyls serve as precursors for the preparation of other organometallic complexes.

<i>tert</i>-Butyllithium Chemical compound

tert-Butyllithium is a chemical compound with the formula (CH3)3CLi. As an organolithium compound, it has applications in organic synthesis since it is a strong base, capable of deprotonating many carbon molecules, including benzene. tert-Butyllithium is available commercially as solutions in hydrocarbons (such as pentane); it is not usually prepared in the laboratory.

<span class="mw-page-title-main">1,1'-Bis(diphenylphosphino)ferrocene</span> Chemical compound

1,1′-Bis(diphenylphosphino)ferrocene, commonly abbreviated dppf, is an organophosphorus compound commonly used as a ligand in homogeneous catalysis. It contains a ferrocene moiety in its backbone, and is related to other bridged diphosphines such as 1,2-bis(diphenylphosphino)ethane (dppe).

A hydrogenase mimic or bio-mimetic is an enzyme mimic of hydrogenases.

Organoiron chemistry is the chemistry of iron compounds containing a carbon-to-iron chemical bond. Organoiron compounds are relevant in organic synthesis as reagents such as iron pentacarbonyl, diiron nonacarbonyl and disodium tetracarbonylferrate. Although iron is generally less active in many catalytic applications, it is less expensive and "greener" than other metals. Organoiron compounds feature a wide range of ligands that support the Fe-C bond; as with other organometals, these supporting ligands prominently include phosphines, carbon monoxide, and cyclopentadienyl, but hard ligands such as amines are employed as well.

<span class="mw-page-title-main">Iron–nickel clusters</span>

Iron–nickel (Fe–Ni) clusters are metal clusters consisting of iron and nickel, i.e. Fe–Ni structures displaying polyhedral frameworks held together by two or more metal–metal bonds per metal atom, where the metal atoms are located at the vertices of closed, triangulated polyhedra.

Transition metal carbyne complexes are organometallic compounds with a triple bond between carbon and the transition metal. This triple bond consists of a σ-bond and two π-bonds. The HOMO of the carbyne ligand interacts with the LUMO of the metal to create the σ-bond. The two π-bonds are formed when the two HOMO orbitals of the metal back-donate to the LUMO of the carbyne. They are also called metal alkylidynes—the carbon is a carbyne ligand. Such compounds are useful in organic synthesis of alkynes and nitriles. They have been the focus on much fundamental research.

<span class="mw-page-title-main">Metal salen complex</span> Coordination complex

A metal salen complex is a coordination compound between a metal cation and a ligand derived from N,N′-bis(salicylidene)ethylenediamine, commonly called salen. The classical example is salcomine, the complex with divalent cobalt Co2+, usually denoted as Co(salen). These complexes are widely investigated as catalysts and enzyme mimics.

<span class="mw-page-title-main">Metal-phosphine complex</span>

A metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh(PPh3)3Cl), Grubbs' catalyst, and tetrakis(triphenylphosphine)palladium(0).

<span class="mw-page-title-main">Half sandwich compound</span> Class of coordination compounds

Half sandwich compounds, also known as piano stool complexes, are organometallic complexes that feature a cyclic polyhapto ligand bound to an MLn center, where L is a unidentate ligand. Thousands of such complexes are known. Well-known examples include cyclobutadieneiron tricarbonyl and (C5H5)TiCl3. Commercially useful examples include (C5H5)Co(CO)2, which is used in the synthesis of substituted pyridines, and methylcyclopentadienyl manganese tricarbonyl, an antiknock agent in petrol.

<span class="mw-page-title-main">Transition-metal allyl complex</span>

Transition-metal allyl complexes are coordination complexes with allyl and its derivatives as ligands. Allyl is the radical with the connectivity CH2CHCH2, although as a ligand it is usually viewed as an allyl anion CH2=CH−CH2−, which is usually described as two equivalent resonance structures.

<i>ortho</i>-Carborane Chemical compound

ortho-Carborane is the organoboron compound with the formula C2B10H12. The prefix ortho is derived from ortho. It is the most prominent carborane. This derivative has been considered for a wide range of applications from heat-resistant polymers to medical applications. It is a colorless solid that melts, without decomposition, at 320 °C.

<span class="mw-page-title-main">Transition metal isocyanide complexes</span> Class of chemical compounds

Transition metal isocyanide complexes are coordination compounds containing isocyanide ligands. Because isocyanides are relatively basic, but also good pi-acceptors, a wide range of complexes are known. Some isocyanide complexes are used in medical imaging.

<span class="mw-page-title-main">Transition metal porphyrin complexes</span>

Transition metal porphyrin complexes are a family of coordination complexes of the conjugate base of porphyrins. Iron porphyrin complexes occur widely in Nature, which has stimulated extensive studies on related synthetic complexes. The metal-porphyrin interaction is a strong one such that metalloporphyrins are thermally robust. They are catalysts and exhibit rich optical properties, although these complexes remain mainly of academic interest.

<span class="mw-page-title-main">Disulfidobis(tricarbonyliron)</span> Chemical compound

Disulfidobis(tricarbonyliron), or Fe2(μ-S2)(CO)6, is an organometallic molecule used as a precursor in the synthesis of iron-sulfur compounds. Popularized as a synthetic building block by Dietmar Seyferth, Fe2(μ-S2)(CO)6 is commonly used to make mimics of the H-cluster in [FeFe]-hydrogenase. Much of the reactivity of Fe2(μ-S2)(CO)6 proceeds through its sulfur-centered dianion, [Fe2(μ-S)2(CO)2]2-.

References

  1. 1 2 "Marcetta Y. Darensbourg". Texas A&M University.
  2. ↑ York, Marcetta Bernice (1967). Kinetic studies of some organolithium reactions (Thesis). OCLC   498417447.
  3. ↑ "Five Science Faculty Honored as Distinguished Professors" (Press release). Texas A&M University. 6 Sep 2010. Archived from the original on 28 September 2011. Retrieved 18 July 2011.
  4. ↑ "The Inorganic Syntheses Organization". Inorganic Syntheses. Archived from the original on 2011-07-13.
  5. ↑ "Recent Volumes". Inorganic Syntheses. Archived from the original on 2011-07-13.
  6. ↑ "Darensbourg Elected Fellow of American Academy of Arts and Sciences" (Press release). Texas A&M University. 19 Apr 2011.
  7. 1 2 3 4 Kimura, Bert Y.; Hartwell, George E.; Lawrence, Theodore; Darensbourg, Marcetta Y. (1970). "Organometallic Exchange Reactions. X. Cross-association of Tert Butyllithium. Kinetics of Tert Butyllithium Dissociation". Journal of the American Chemical Society. 92 (5): 1236–242. doi:10.1021/ja00708a022.
  8. ↑ Darensbourg, Marcetta Y.; Darensbourg, Donald J. (1970). "Spectroscopic Studies of Some Carbene Pentacarbonyl Complexes of Chromium(0) and Tungsten(0)". Inorganic Chemistry. 9 (1): 32–39. doi:10.1021/ic50083a007.
  9. ↑ Darensbourg, Donald J.; Darensbourg, Marcetta Y. (1970). "Reactions of Transition Metal Carbonyls with Organolithium Compounds. II. Prediction of Nucleophilic Attack at Carbon and Resultant Stereochemistry". Inorganic Chemistry. 9 (7): 1691–694. doi:10.1021/ic50089a016.
  10. ↑ Lyon, Erica J; Zhao, Xuan; Georgakaki, Irene P.; Darensbourg, Marcetta Y. (2003). "The Organometallic Active Site of [Fe]hydrogenase: Models and Entatic States". Proceedings of the National Academy of Sciences of the United States of America. 100 (7): 3683–3688. Bibcode:2003PNAS..100.3683D. doi: 10.1073/pnas.0536955100 . PMC   152982 . PMID   12642671.
  11. ↑ Tye, Jesse W.; Hall, Michael B.; Darensbourg, Marcetta Y. (2005). "Better than Platinum? Fuel Cells Energized by Enzymes". Proceedings of the National Academy of Sciences of the United States of America. 102 (47): 16911–16912. Bibcode:2005PNAS..10216911T. doi: 10.1073/pnas.0508740102 . PMC   1288019 . PMID   16286638.
  12. ↑ Yang, Xuemei; Darensbourg, Marcetta Y. (2020). "The roles of chalcogenides in O 2 protection of H 2 ase active sites". Chemical Science. 11 (35): 9366–9377. doi:10.1039/D0SC02584D. ISSN   2041-6520. PMC   8161538 . PMID   34094202.
  13. ↑ Pulukkody, Randara; Chupik, Rachel B.; Montalvo, Steven K.; Khan, Sarosh; Bhuvanesh, Nattamai; Lim, Soon-Mi; Darensbourg, Marcetta Y. (2017). "Toward Biocompatible Dinitrosyl Iron Complexes: Sugar-Appended Thiolates". Chemical Communications. 53 (6): 1180–1183. doi:10.1039/c6cc08659d. PMID   28058431.
  14. ↑ Tiankun, Zhao; Ghosh, Pokhraj; Martinez, Zachary; Liu, Xufeng; Meng, Xianggao; Darensbourg, Marcetta Y. (2017). "Discrete Air-Stable Nickel(II)-Palladium(II) Complexes as Catalysts for Suzuki-Miyaura Reaction". Organometallics. 36 (9): 1822–1827. doi:10.1021/acs.organomet.7b00176.
  15. ↑ Ghosh, Pokhraj; Quiroz, Manuel; Wang, Ning; Bhuvanesh, Nattamai; Darensbourg, Marcetta Y. (2017). "Complex of as platform for exploring cooperative heterobimetallic effects in HER electro catalysis". Dalton Transactions. 46 (17): 5617–5624. doi:10.1039/c6dt04666e. PMID   28174781.
  16. 1 2 3 4 5 Quiroz, Manuel; Lockart, Molly M.; Xue, Shan; Jones, Dakota; Guo, Yisong; Pierce, Brad S.; Dunbar, Kim R.; Hall, Michael B.; Darensbourg, Marcetta Y. (2023). "Magnetic coupling between Fe(NO) spin probe ligands through diamagnetic Ni II , Pd II and Pt II tetrathiolate bridges". Chemical Science. 14 (34): 9167–9174. doi:10.1039/D3SC01546G. ISSN   2041-6520. PMC   10466285 . PMID   37655023.
  17. 1 2 Sun, Ning; Liu, Lei V.; Dey, Abhishek; Villar-Acevedo, Gloria; Kovacs, Julie A.; Darensbourg, Marcetta Y.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I. (2011-01-17). "S K-Edge X-Ray Absorption Spectroscopy and Density Functional Theory Studies of High and Low Spin {FeNO} 7 Thiolate Complexes: Exchange Stabilization of Electron Delocalization in {FeNO} 7 and {FeO 2 } 8". Inorganic Chemistry. 50 (2): 427–436. doi:10.1021/ic1006378. ISSN   0020-1669. PMC   3130116 . PMID   21158471.
  18. ↑ "Willard Gibbs Award". chicagoacs.org. Retrieved 2024-04-12.
  19. ↑ "SEC Faculty Achievement Awards | SEC Academics | SEC". SECU. Retrieved 2024-04-12.
  20. ↑ "2017 Recipients". American Chemical Society. Retrieved 2024-04-12.
  21. ↑ "College of Science Honors 2016 Award Winners – TAMU Physics & Astronomy". physics.tamu.edu. Retrieved 2024-04-12.
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