Starspot
spot on a star - on the Sun these are sunspots
Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in general much larger than those on the Sun: up to about 30% of the stellar surface may be covered, corresponding to starspots 100 times larger than those on the Sun.
Detection and measurements
To detect and measure the extent of starspots one uses several types of methods.
For rapidly rotating stars – Doppler imaging and Zeeman-Doppler imaging. With the Zeeman-Doppler imaging technique the direction of the magnetic field on stars can be determined since spectral lines are split according to the Zeeman effect, revealing the direction and magnitude of the field.
For slowly rotating stars – Line Depth Ratio (LDR). Here one measures two different spectral lines, one sensitive to temperature and one which is not. Since starspots have a lower temperature than their surroundings the temperature-sensitive line changes its depth. From the difference between these two lines the temperature and size of the spot can be calculated, with a temperature accuracy of 10K.
For eclipsing binary stars – Eclipse mapping produces images and maps of spots on both stars.
Begin with the source’s own compact description: “Starspot” is spot on a star - on the Sun these are sunspots. The dossier treats that line as a proposition to test through Starspot, spot and star, not as a finished interpretation.
Why this record matters
The phrase “spot on a star - on the Sun these are sunspots” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 17, 2026. The linked authority identifier is Q1893536. The Library of Congress control number is sh92000971. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
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This entry incorporates text from “Starspot” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.