Blazhko effect

---

title: "Blazhko effect" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["stellar-phenomena", "rr-lyrae-variables", "concepts-in-stellar-astronomy"] description: "Variation in period and amplitude in RR Lyrae type variable stars" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Blazhko_effect" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Variation in period and amplitude in RR Lyrae type variable stars ::

The Blazhko effect, also known as the Tseraskaya–Blazhko effect, and which is sometimes called long-period modulation, is a variation in period and amplitude in RR Lyrae type variable stars. Sergey Blazhko first reported its observation by Lidiya Tseraskaya in 1907, in the star RW Draconis. |title=RR Lyrae Stars |author=Horace A. Smith |page=103 |url= https://books.google.com/books?id=dMv_r82moCQC&pg=PA104 |isbn=0-521-54817-9 |publisher=Cambridge University Press |year=2004

The physics behind the Blazhko effect is currently still a matter of debate, with there being three primary hypotheses. In the first, referred to as the resonance model, the cause of the modulation is a non-linear resonance among either the fundamental or the first overtone pulsation mode of the star and a higher mode. The second, known as the magnetic model, assumes the variation to be caused by the magnetic field being inclined to the rotational axis, deforming the main radial mode. The magnetic model was ruled out in 2004 by high resolution spectro-polarimetric observations. The third model assumes that cycles in the convection cause the alternations and the modulations.

Observational evidence based on Kepler space telescope observations indicates much of the Blazhko effect's two-cycle light curve modulation is due to simple period-doubling. Many RR Lyrae stars have a variability period of approximately 12 hours and ground-based astronomers typically make nightly observations about 24 hours apart; thus period-doubling results in brightness maximums during nightly observations that are significantly different from the daytime maximum. | url = http://www.univie.ac.at/tops/blazhko/Background.html | title =Explanations for the Blazhko effect in RR Lyrae stars | accessdate = 2008-12-17 | author = Katrien Kolenberg | year = 2008 | work =The Blazhko Project

References

References

1. (April 8, 2022). "Asteroseismology Across the Hertzsprung–Russell Diagram". Annual Review of Astronomy and Astrophysics.
2. (1907). "Mitteilung über veränderliche Sterne". Astronomische Nachrichten.
3. (2011). "Period-doubling bifurcation and high-order resonances in RR Lyrae hydrodynamical models". MNRAS.
4. (2004). "No evidence of a strong magnetic field in the Blazhko star RR Lyrae". Astronomy & Astrophysics.
5. (2010). "Observational Evidence of Convective Cycles as the Cause of the Blazhko Effect in RR Lyrae Stars". Publications of the Astronomical Society of the Pacific.
6. (2010). "Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars". MNRAS.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::