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master's thesis
Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom
Zagreb: University of Zagreb, Faculty of Science, 2020. urn:nbn:hr:217:668223
Novaković, Miljenko
University of Zagreb
Faculty of Science
Department of Physics

Institutional repository: Repository of the Faculty of Science

Cite this document

Novaković, M. (2020). Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom (Master's thesis). Zagreb: University of Zagreb, Faculty of Science. Retrieved from https://urn.nsk.hr/urn:nbn:hr:217:668223

Novaković, Miljenko. "Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom." Master's thesis, University of Zagreb, Faculty of Science, 2020. https://urn.nsk.hr/urn:nbn:hr:217:668223

Novaković, Miljenko. "Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom." Master's thesis, University of Zagreb, Faculty of Science, 2020. https://urn.nsk.hr/urn:nbn:hr:217:668223

Novaković, M. (2020). 'Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom', Master's thesis, University of Zagreb, Faculty of Science, accessed 20 May 2024, https://urn.nsk.hr/urn:nbn:hr:217:668223

Novaković M. Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom [Master's thesis]. Zagreb: University of Zagreb, Faculty of Science; 2020 [cited 2024 May 20] Available at: https://urn.nsk.hr/urn:nbn:hr:217:668223

M. Novaković, "Analiza pouzdanosti paralaksi cefeida opažanih Gaia satelitom", Master's thesis, University of Zagreb, Faculty of Science, Zagreb, 2020. Available at: https://urn.nsk.hr/urn:nbn:hr:217:668223

Metadata
TitleAnaliza pouzdanosti paralaksi cefeida opažanih Gaia satelitom
Title (english)An analysis of the uncertainty of the parallaxes obtained with the Gaia satellite
AuthorMiljenko Novaković
MentorLovro Palaversa (mentor)
MentorMatko Milin (komentor)
Committee memberMatko Milin (predsjednik povjerenstva)
Committee memberLovro Palaversa (član povjerenstva)
Committee memberKatarina Jeličić (član povjerenstva)
Committee memberNikola Poljak (član povjerenstva)
Committee memberMaja Planinić (član povjerenstva)
GranterUniversity of Zagreb
Faculty of Science
(Department of Physics)
Zagreb
Defense date and country2020-11-20, Croatia
Scientific / art field,
discipline and subdiscipline		NATURAL SCIENCES
Physics
Abstract
Hubbleova konstanta (H_0) je mjera trenutnog širenja svemira. Kako bi se odredila vrijednost H_0, potrebno je razviti i koristiti niz metoda određivanja udaljenosti na međuzvjezdanim, međugalaktičkim i kozmološkim skalama. Često korišten skup metoda, čija osnova su metode bazirane na sjaju opažanih astrofizičkih objekata, je "ljestvica udaljenosti". Važnu stepenicu u ljestvici udaljenosti predstavljaju cefeide, periodički promjenjive zvijezde čiji sjaj je povezan s periodom pulsacija. Kako bi se točno odredio luminozitet cefeida i kalibrirala period-luminozitet relacija, potrebno je točno odrediti udaljenosti cefeida. Jedina čisto geometrijska metoda pomoću koje se mogu odrediti udaljenosti zvijezda u Mliječnom putu je metoda paralakse. Paralakse zvijezda (osim Sunca) su vrlo male, manje od 785 kutnih milisekundi, a mjerljive su do reda veličine kutne mikrosekunde. Mjerenja su podložna raznim sistematskim pogreškama. Jedan od izvora pogrešaka mogu biti i promjene sjaja opažanih zvijezda. U ovom diplomskom radu provjerena je pouzdanost paralaksi cefeida određenih Gaia satelitom Europske svemirske agencije (ESA) usporedbom s paralaksama zvijezda konstantnog sjaja u blizini cefeida. S tim ciljem izvršena je potraga za cefeidama u otvorenim skupovima – gravitacijski povezanim skupinama zvijezda relativno malih prostornih dimenzija s obzirom na njihovu udaljenost od Zemlje. Usporedbom paralaksi otvorenih skupova (određenih kao medijan paralakse zvijezda konstantnog sjaja pojedinog skupa) i cefeida ne može se odbaciti hipoteza da su paralakse cefeida i otvorenih skupova jednake. No, u promatranom uzorku je vidljiv trend većih vrijednosti paralaksi otvorenih skupova. U kontekstu određivanja Hubbleove konstante, ovakav rezultat bi dodatno povećao neslaganje među vrijednostima dobivenim izravnim mjerenjem H_0 i vrijednostima predviđenim ΛCDM modelom na temelju mikrovalnog pozadinskog zračenja opaženog Planck satelitom ESA-e
Abstract (english)
Hubble constant (H_0) is the present rate of Universe expansion. H_0 estimation methods critically rely upon distance estimation on interstellar, intergalactic, and cosmological scales. A particularly common suite of distance measuring methods is the "distance ladder". Cepheid variable stars are a crucial rung in the distance ladder as they exhibit well-understood periodluminosity relations. However, to determine the luminosity of the cepheids, precise distances to them must be acquired. The only method free of astrophysical assumptions to determine distances to the stars (except to our Sun) is the stellar parallax method. As parallaxes are typically very small: 785 miliarcseconds in case of Proxima Centauri and typically below miliarcsecond for stars in the Milky Way, their estimation can be affected by a number of systematic effects. One of the key effects may be the variability of the observed source. With this in mind, in this work the Cepheid parallax reported by the European Space Agency’s (ESA) Gaia spacecraft is compared to the parallaxes of the stars nearby the said Cepheids. In order to identify the nearby stars, Cepheids that are members of open clusters (gravitationally bound groups of stars) are identified. Then, the reported Cepheid parallax is compared to the median parallax of the constant stars in the corresponding open cluster. Based on the analysis, the hypothesis that the Cepheid parallaxes and the median open cluster parallaxes are the same cannot be rejected. We do note that there exists an offset between the two samples indicating the open cluster parallaxes are larger. In the context of the Hubble constant tension, this result would further increase the discrepancy between the results reported by the methods measuring the local H_0 and the predictions of the H_0 based on the ΛCDM and the ESA’s Planck spacecraft.
Keywords
Keywords (english)
Languagecroatian
URN:NBNurn:nbn:hr:217:668223
Study programmeTitle: Physics and Computer Science; specializations in: Education
Course: Education
Study programme type: university
Study level: integrated undergraduate and graduate
Academic / professional title: magistar/magistra fizike i informatike (magistar/magistra fizike i informatike)
Type of resourceText
File originBorn digital
Access conditionsOpen access
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Created on2021-01-08 10:17:58