Lihat sumber Astrofisika

{{Kosmologi}}{{Ilmu}}
'''Astrofisika''' adalah bidang ilmu yang mempelajari sifat-sifat [[fisika]] fenomena dan objek [[astronomi]] di [[Jagad raya|jagat raya]]. Astrofisika membahas objek-objek di luar angkasa dan juga [[Bumi]]. Terkadang, penamaannya dapat berganti dengan [[astronomi]] karena lingkup studinya yang mirip pada masa modern.{{Sfn|Maoz|2016|p=1}}

== Sejarah ==
Astronomi adalah ilmu kuno, lama terpisah dari studi fisika [[terestrial]]. Dalam pandangan dunia [[Aristoteles]], benda-benda di langit tampak seperti bola yang tidak berubah dan gerakan satu-satunya adalah gerakan seragam dalam lingkaran. Sementara itu, dunia teresterial adalah alam yang mengalami pertumbuhan dan pembusukan, dan gerakannya berada dalam garis lurus yang berakhir ketika benda tersebut mencapai tujuannya. Terdapat anggapan bahwa luar angkasa terbuat dari jenis materi yang berbeda dari materi yang ditemukan di dunia terestrial; diyakini oleh Aristoteles sebagai [[Aether (elemen klasik)|Aether]],<ref>{{Cite book|last=Lloyd|first=G. E. R. (Geoffrey Ernest Richard)|date=1968|url=http://archive.org/details/aristotlegrowths0000lloy|title=Aristotle : the growth and structure of his thought|location=|publisher=London : Cambridge University Press|isbn=978-0-521-07049-2|pages=134|others=Internet Archive|quote=But the region of the heavenly bodies, from the moon to the outermost circle of the fixed stars, is constituted not by any of these four elements singly or in any combination, but by a fifth element, aither, which has the property of moving naturally in a circle.|url-status=live}}</ref> atau sebagai [[Api (unsur klasik)|Api]] oleh [[Plato]].<ref>{{Cite book|last=Plato|first=|last2=Cornford|first2=Francis M.|date=1997|url=https://books.google.co.id/books?id=KQsmLW8v0WwC&lpg=PP1&pg=PA118#v=onepage&q&f=false|title=Plato's Cosmology: The Timaeus of Plato|location=|publisher=Hackett Publishing|isbn=978-0-87220-386-0|pages=118|language=en|url-status=live}}</ref> Selama abad ke-17, filsuf alam seperti [[Galileo Galilei|Galileo]],<ref>{{Cite book|last=Galilei|first=Galileo|date=1610|url=http://people.reed.edu/~wieting/mathematics537/SideriusNuncius.pdf|title=Sidereus Nuncius|location=Venice|publisher=|isbn=|pages=13|translator-last=Helden|translator-first=Albert Van|trans-title=Sidereal Messenger|quote=By oft-repeated observations of them we have been led to the conclusion that we certainly see the surface of the Moon to be not smooth, even, and perfectly spherical, as the great crowd of philosophers have believed about this and other heavenly bodies, but, on the contrary, to be uneven, rough, and crowded with depressions and bulges. And it is like the face of the Earth itself, which is marked here and there with chains of mountains and depths of valleys.|author-link=Galileo Galilei|url-status=live|access-date=2020-10-31|archive-date=2021-05-13|archive-url=https://web.archive.org/web/20210513224028/https://people.reed.edu/~wieting/mathematics537/SideriusNuncius.pdf|dead-url=yes}}</ref> [[René Descartes|Descartes]],<ref>Slowik, Edward (2017). Zalta, Edward N., ed. ''[https://plato.stanford.edu/entries/descartes-physics/ The Stanford Encyclopedia of Philosophy]'' (Fall 2017 Edition). Metaphysics Research Lab, Stanford University. "It is obvious that when God first created the world, He not only moved its parts in various ways, but also simultaneously caused some of the parts to push others and to transfer their motion to these others. So in now maintaining the world by the same action and with the same laws with which He created it, He conserves motion; not always contained in the same parts of matter, but transferred from some parts to others depending on the ways in which they come in contact."</ref> dan Newton<ref>{{Cite book|last=Bricker|first=Phillip|last2=Hughes|first2=Professor of Philosophy R. I. G.|last3=Hughes|first3=R. I. G.|last4=Hughes|first4=R. I.|date=1990|url=https://books.google.co.id/books?id=oKaQkyCp1toC&lpg=PP1&pg=PA140#v=onepage&q&f=false|title=Philosophical Perspectives on Newtonian Science|location=|publisher=MIT Press|isbn=978-0-262-02301-6|pages=140|language=en|url-status=live}}</ref> mulai berpendapat bahwa daerah angkasa dan terestrial terbuat dari jenis bahan yang serupa dan tunduk pada hukum alam yang sama. Tantangan mereka adalah saat itu belum ditemukan alat untuk membuktikan pernyataan ini.

Selama abad kesembilan belas, penelitian astronomi berfokus pada pengukuran dan perhitungan rutin posisi dan gerakan [[objek astronomi]].<ref>{{Cite journal|last=Case|first=Stephen|date=2015-10-02|title=‘Land-marks of the universe’: John Herschel against the background of positional astronomy|url=https://doi.org/10.1080/00033790.2015.1034588|journal=Annals of Science|volume=72|issue=4|pages=417–434|doi=10.1080/00033790.2015.1034588|issn=0003-3790|pmid=26221834|quote=The great majority of astronomers working in the early nineteenth century were not interested in stars as physical objects. Far from being bodies with physical properties to be investigated, the stars were seen as markers measured in order to construct an accurate, detailed and precise background against which solar, lunar and planetary motions could be charted, primarily for terrestrial applications.}}</ref> Cabang astronomi baru, yang kemudian disebut astrofisika,<ref>{{Cite web|last=Kolesnikova Tasha|first=|date=2023-07-17|title=The Difference Between Astronomy and Astrophysics|url=https://studybay.com/blog/difference-between-astronomy-and-astrophysics/|website=studybay.com}}</ref> baru muncul ketika [[William Hyde Wollaston]] dan [[Joseph von Fraunhofer]] secara terpisah mendapati bahwa banyak [[Garis-garis Fraunhofer|garis gelap]] (daerah yang terdapat sedikit atau tidak ada cahaya) yang diamati dalam [[Spektrum kasatmata|spektrum]] ketika cahaya Matahari diuraikan.<ref>{{Cite book|last=Hearnshaw|first=J. B.|date=1990-04-19|url=https://books.google.co.id/books?id=iCs4AAAAIAAJ&lpg=PP1&pg=PA23#v=onepage&q&f=false|title=The Analysis of Starlight: One Hundred and Fifty Years of Astronomical Spectroscopy|location=|publisher=CUP Archive|isbn=978-0-521-39916-6|pages=23, 27|language=en|url-status=live}}</ref> Pada tahun 1860, fisikawan [[Gustav Robert Kirchhoff|Gustav Kirchhoff]] dan ahli kimia, [[Robert Bunsen]], mengamati bahwa garis-garis gelap pada spektrum Matahari berhubungan dengan garis-garis terang pada spektrum gas yang diketahui, berhubungan dengan [[unsur kimia]] yang unik.<ref>{{Cite web|last=|first=|date=1 Mei 2016|title=Robert Bunsen and Gustav Kirchhoff|url=https://www.sciencehistory.org/historical-profile/robert-bunsen-and-gustav-kirchhoff|website=Science History Institute|language=en|access-date=31 Oktober 2020}}</ref> Kirchhoff menyimpulkan bahwa garis-garis gelap pada spektrum Matahari disebabkan oleh penyerapan unsur kimiawi di atmosfer Matahari. Dengan cara ini terbukti bahwa unsur kimia yang ditemukan di Matahari dan bintang juga ditemukan di Bumi.<ref name=":0">{{Cite web|last=|first=|date=|title=Spectroscopy and the Birth of Astrophysics (Cosmology: Tools)|url=https://history.aip.org/exhibits/cosmology/tools/tools-spectroscopy.htm|website=history.aip.org|access-date=31 Oktober 2020|quote=}}</ref>

Pada tahun 1868, [[Norman Lockyer]] mempelajari garis-garis terang dan gelap dalam spektrum Matahari. Dia bekerja dengan ahli kimia [[Edward Frankland]] untuk menyelidiki spektrum unsur-unsur pada berbagai suhu dan tekanan tetapi tidak dapat menghubungkan garis kuning dalam spektrum Matahari dengan unsur-unsur yang telah diketahui saat itu.<ref>{{Cite journal|last=Cortie|first=A. L.|date=1921-05-01|title=Sir Norman Lockyer, 1836-1920|url=http://adsabs.harvard.edu/abs/1921ApJ....53..233C|journal=The Astrophysical Journal|volume=53|issue=|pages=237|doi=10.1086/142602}}</ref> Dia kemudian menyatakan garis tersebut mewakili elemen baru, disebut [[helium]], dari [[bahasa Yunani]] [[Helios]], dewa Matahari.<ref>{{Cite journal|last=Jensen|first=William B.|date=2004-07-01|title=Why Helium Ends in "-ium"|url=https://doi.org/10.1021/ed081p944|journal=Journal of Chemical Education|volume=81|issue=7|pages=944|doi=10.1021/ed081p944|issn=0021-9584|quote=As a result, Lockyer concluded that it belonged to a unknown element for which the name “helium” (from the Greek, helios, meaning “sun”) was contrived.}}</ref>

Pada tahun 1885, [[Edward C. Pickering]] menjalankan program klasifikasi spektrum bintang di [[Observatorium Harvard|Harvard College Observatory]],<ref name=":0" /> di mana tim [[Komputer Harvard|komputer wanita]], terutama [[Williamina Fleming]], [[Antonia Maury]], dan [[Annie Jump Cannon]], mengklasifikasikan spektrum yang terekam pada pelat fotografi.<ref>{{Cite web|last=November 2016|first=Elizabeth Howell 12|title=Annie Jump Cannon: 'Computer' Who Classified the Stars|url=https://www.space.com/34707-annie-jump-cannon-biography.html|website=Space.com|language=en|access-date=2020-10-31}}</ref> Pada tahun 1890, tersusun katalog lebih dari 10.000 bintang yang dikelompokkan ke dalam tiga belas jenis spektral. Pada 1924, Cannon memperluas katalog menjadi sembilan volume dengan lebih dari 250 ribu bintang, mengembangkan [[Klasifikasi bintang#Klasifikasi Harvard (kelas spektrum)|Skema Klasifikasi Harvard]] yang digunakan di seluruh dunia pada tahun 1922.<ref name=":0" />

Pada tahun 1895, [[George Ellery Hale]] dan [[James Edward Keeler|James E. Keeler]], bersama dengan sepuluh rekan editor dari Eropa dan [[Amerika Serikat]], mendirikan [[The Astrophysical Journal]]. Jurnal tersebut dimaksudkan untuk mengisi kekosongan dalam jurnal dalam astronomi dan fisika, menyediakan tempat untuk publikasi artikel tentang aplikasi [[Spektroskopi|spektroskop]] dalam astronomi; penelitian laboratorium yang terkait erat dengan fisika astronomi; eksperimen pada radiasi dan absorpsi Matahari; teori Matahari, Bulan, planet, komet, meteor, dan [[nebula]]; dan instrumentasi untuk teleskop dan laboratorium.<ref>{{Cite journal|last=Hale|first=George E.|date=1895-01-01|title=The Astrophysical Journal.|url=http://adsabs.harvard.edu/abs/1895ApJ.....1...80H|journal=The Astrophysical Journal|volume=1|issue=1|pages=81-82|doi=10.1086/140011}}</ref>

Sekitar 1920, saat [[diagram Hertzsprung-Russell]] masih digunakan sebagai dasar untuk mengklasifikasikan bintang dan evolusinya, [[Arthur Eddington]] mengantisipasi penemuan dan mekanisme proses [[fusi nuklir]] pada bintang dalam makalahnya ''The Internal Constitution of the Stars''.<ref>{{Cite journal|last=Eddington|first=A. S.|date=1920-09-10|title=The Internal Constitution of the Stars|url=https://science.sciencemag.org/content/52/1341/233|journal=Science|language=en|volume=52|issue=1341|pages=233–240|doi=10.1126/science.52.1341.233|issn=0036-8075|pmid=17747682|quote=This remarkable condition has been made known through the researches of H. N. Russell and E. Hertzsprung; the way in which their conclusions, which ran counter to the prevailing thought of the time, have been substantiated on all sides by overwhelming evidence, is the outstanding feature of recent progress in stellar astronomy. (...) As this diffuse mass of gas contracts its temperature must rise, a conclusion long ago pointed out by Homer Lane. The rise continues until the star becomes too dense, and ceases to behave as a perfect gas. A maximum temperature is attained, depending on the mass, after which the star, which has now become a dwarf, cools and further contracts. Thus each temperature-level is passed through twice, once in an ascending and once in a descending stage-once as a giant, once as a dwarf. Temperature plays so predominant a part in the usual spectral classification that the ascending and descending stars were not originally discriminated, and the customary classification led to some perplexities. The separation of the two series was discovered through their great difference in luminosity, particularly striking in the case of the red and yellow stars, where the two stages fall widely apart in the star's history.}}</ref> Pada saat itu, sumber energi bintang masih belum diketahui. Eddington dengan tepat berspekulasi bahwa sumbernya adalah fusi [[hidrogen]] menjadi helium, melepaskan energi yang sangat besar memenuhi persamaan [[Albert Einstein|Einstein]] [[Ekuivalensi massa–energi|'''<math> E = mc^2 \!</math>''']]. Ini adalah sebuah terobosan baru karena pada saat itu [[reaksi nuklir]] belum sepenuhnya diketahui.<ref>{{Cite book|last=McCracken|first=Garry|last2=Stott|first2=Peter|date=2013-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780123846563000027|title=Fusion (Second Edition)|location=Boston|publisher=Academic Press|isbn=978-0-12-384656-3|editor-last=McCracken|editor-first=Garry|pages=13|language=en|doi=10.1016/b978-0-12-384656-3.00002-7|quote=Eddington had realized that there would be a mass loss if four hydrogen atoms combined to form a single helium atom. Einstein’s equivalence of mass and energy led directly to the suggestion that this could be the long-sought process that produces the energy in the stars! It was an inspired guess, all the more remarkable because the structure of the nucleus and the mechanisms of these reactions were not fully understood.|editor-last2=Stott|editor-first2=Peter|url-status=live}}</ref>

Pada tahun 1925, [[Cecilia Payne-Gaposchkin]] menulis disertasi doktoral di [[Radcliffe College]]. Dia menerapkan teori [[ionisasi]] pada atmosfer bintang untuk menghubungkan kelas spektral dengan suhu bintang.<ref>{{Cite thesis|last=Payne, C. H.|first=|title=Stellar Atmospheres; a Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars|date=1925|degree=PhD|publisher=|url=http://articles.adsabs.harvard.edu//full/1925PhDT.........1P/0000001,009.html|doi=|halaman=|page=iv}}</ref> Dia mendapati bahwa hidrogen dan helium adalah penyusun utama sebuah bintang. Namun, pada saat tesisnya diterbitkan, [[Henry Norris Russell]] dari [[Universitas Princeton]] meyakinkan Payne bahwa kesimpulannya pasti salah. Russell kemudian mempelajari temuan Payne selama empat tahun, dan dalam [[The Astrophysical Journal|Astrophysical Journal]] edisi Juli 1929 menyatakan bahwa penemuan Payne tidak dapat diragukan.<ref>{{Cite web|last=Glorfeld|first=Jeff|date=9 Mei 2018|title=This week in science history: The woman who found hydrogen in the stars is born|url=https://cosmosmagazine.com/physics/this-week-in-science-history-the-woman-who-found-hydrogen-in-the-stars-is-born/|website=Cosmos Magazine|language=en-AU|access-date=31 Oktober 2020}}</ref>

Pada akhir abad ke-20, studi tentang spektrum astronomi telah meluas hingga mencakup [[panjang gelombang]] yang membentang dari [[Radio|gelombang radio]] hingga panjang gelombang optik, [[Sinar-X|x-ray]], dan [[Sinar gama|gamma]].<ref>{{Cite journal|last=Biermann|first=Peter L.|last2=Falcke|first2=Heino|date=1998-02-05|title=Frontiers of Astrophysics—Workshop summary|url=https://aip.scitation.org/doi/abs/10.1063/1.55085|journal=AIP Conference Proceedings|volume=423|issue=1|pages=236–248|doi=10.1063/1.55085|issn=0094-243X|quote=Since the highlights of early 1997 were the first detection of a redshift and the optical and X-ray afterglows of gamma-ray bursts, as well as the first well-documented flares of TeV-Blazars across a large fraction of the electromagnetic spectrum, we will concentrate on these topics.}}</ref> Pada abad ke-21, teori ini diperluas dengan memasukkan pengamatan berdasarkan [[gelombang gravitasi]].<ref>{{Cite journal|last=Sathyaprakash|first=B. S.|last2=Schutz|first2=Bernard F.|date=2009-12-01|title=Physics, Astrophysics and Cosmology with Gravitational Waves|url=https://doi.org/10.12942/lrr-2009-2|journal=Living Reviews in Relativity|language=en|volume=12|issue=1|pages=110|doi=10.12942/lrr-2009-2|issn=1433-8351|pmc=PMC5255530|pmid=28163611}}</ref>

== Metode studi ==

=== Astrofisika teoretis ===
{{see also|Astronomi teoretis}}Astrofisika teoretis mencakup [[Model matematika|model analitis]] dan [[Analisis numerik|simulasi numerik]] komputasi. Model analitis umumnya lebih baik untuk memberikan wawasan inti tentang objek yang sedang diamati sementara model numerik dapat mengungkapkan keberadaan fenomena dan efek yang tidak terlihat.<ref>{{Cite book|last=|first=|date=2006|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/0471743984.vse8722|title=Van Nostrand's Scientific Encyclopedia|location=|publisher=American Cancer Society|isbn=978-0-471-74398-9|pages=5|language=en|doi=10.1002/0471743984.vse8722|quote=Theoretical astrophysicists use a wide variety of tools which include analytical models (for example, polytropes to approximate the behaviors of a star) and computational numerical simulations. Each has some advantages. Analytical models of a process are generally better for giving insight into the heart of what is going on. Numerical models can reveal the existence of phenomena and effects that would otherwise not be seen.|url-status=live}}</ref>

=== Astrofisika observasional ===
{{see also|Astronomi observasional}}Pengamatan jarak jauh mengakibatkan penelitian Astrofisika tidak dapat dilakukan dalam lingkungan terkendali dan bergantung pada fenomena yang terjadi di alam. Informasi didapat dari [[radiasi elektromagnetik]] yang dikumpulkan oleh instrumen astronomi.<ref>{{Cite book|last=Lena|first=Pierre|last2=Lebrun|first2=Francois|last3=Mignard|first3=Francois|date=2013-03-09|url=https://books.google.co.id/books?id=wS7wCAAAQBAJ&lpg=PA9&dq=Observational%20astrophysics&pg=PA1#v=onepage&q&f=false|title=Observational Astrophysics|location=|publisher=Springer Science & Business Media|isbn=978-3-662-03685-3|pages=1-2|language=en|url-status=live}}</ref>

== Rujukan ==
<references />

== Daftar Pustaka ==

* {{Cite book|last=Maoz|first=Dan|date=2016-02-23|url=https://books.google.com/books?id=bmBeCwAAQBAJ&newbks=0&printsec=frontcover&hl=en|title=Astrophysics in a Nutshell: Second Edition|location=|publisher=Princeton University Press|isbn=978-1-4008-8117-8|pages=|language=en|ref={{Sfnref|Maoz|2016}}|url-status=live}}
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