# Did the star fade over the twentieth century? · Tabby's star (KIC 8462852) > Four answers have been proposed. None is ahead on the evidence yet. Four are still possible. Of the one narrower question under it, none is answered yet. Source: https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E77702V2V/did-the-star-fade-over-the-twentieth-century Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-30T21:51:27+00:00 --- **0** # Did the star fade over the twentieth century? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·Part of [What causes the slow fading of the star?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E76Z60339/what-causes-the-slow-fading-of-the-star)·4 answers·0·0 following **Four answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Four answers have been proposed. None is ahead on the evidence yet. Four are still possible. Of the one narrower question under it, none is answered yet. ## Why it matters A century-long fade would make the long-term change part of a slow, ongoing process and would multiply the amount of dust required⁠[[1]](https://mysteriesdept.com/sources/SRC0D8E6V0C3X81/kic-8462852-faded-at-an-average-rate-of-0-164-0-013). The claim rests on archival plates whose long-term calibration is disputed⁠[[2]](https://mysteriesdept.com/sources/SRC0D8E6V860VNG/a-statistical-analysis-of-the-accuracy-of-the-digitized). ## Answers 4 [**A single drop of about 0.1 mag across the 1953-1969 plate gap, not a steady century fade** ](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0DDYETY1NV0T/a-single-drop-of-about-0-1-mag-across-the-1953-1969-plate) None Evidence: 1 for, 1 against Still possible [**None of these.** ](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0D8E7J6J5FTH/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**The century fade is a calibration artefact of plate photometry.** ](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0D8E7HPY1BFW/the-century-fade-is-a-calibration-artefact-of-plate) Tested, but the results don't decide it Evidence: 2 for, 1 against Disputed [**The star faded by about 0.16 magnitudes per century from 1890 to 1989.** ](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0D8E7H7A1MXP/the-star-faded-by-about-0-16-magnitudes-per-century-from) Tested, but the results don't decide it Evidence: 3 for, 2 against Disputed ## What would settle it 1. Gaia DR3 neighbour screen: replace the APASS 30-arcsec screen with Gaia DR3 sources within 30 arcsec and 4 mag of each comparison star and of the target (the dnb plates resolve about 10 arcsec), then rerun analyze_dasch.py. If the target itself has a faint neighbour inside the dnb seeing disk, the post-1969 offset could be a blend. 1. Colour-term stratification: pull the exposures table (sess.exposures(), median_colorterm_apass) for every plate in the differential series, keep only "good blue" plates (-0.164 to 0.212), and test whether the 0.09 mag post-1969 offset survives; also regress the offset on colour term across series. This is the direct test of the emulsion-colour explanation that DR7 makes possible for the first time. 1. Full per-plate differential with the Starglass platephot endpoint (needs a free API key): for each of the ~900 plates, pull every source within 10 arcmin and fit a plate zero-point from colour-matched stars within 5 arcmin of the target rather than 30 arcmin, then a hierarchical model with one zero-point per plate and one slope per star. Removes the position-dependent part of the plate systematics that the current 30-arcmin differential cannot. ## History 1. 2016[Schaefer puts forward: the star faded by about 0.16 magnitudes per century from 1890 to 1989.](https://mysteriesdept.com/sources/SRC0D8E6V0C3X81/kic-8462852-faded-at-an-average-rate-of-0-164-0-013) 1. 2016[Hippke et al. puts forward: the century fade is a calibration artefact of plate photometry.](https://mysteriesdept.com/sources/SRC0D8E6V860VNG/a-statistical-analysis-of-the-accuracy-of-the-digitized) 1. 2016[Hippke et al.: the pre-1953 record is flat; the slope comes from the post-1969 offset](https://mysteriesdept.com/sources/SRC0D8E6V860VNG/a-statistical-analysis-of-the-accuracy-of-the-digitized)Against: The star faded by about 0.16 magnitudes per century from 1890 to 1989. 1. 2016[Michael B. Lund et al.: the pre-1953 record is flat; the slope comes from the post-1969 offset](https://mysteriesdept.com/sources/SRC0DDYCEJ03QA3/the-stability-of-f-star-brightness-on-century-timescales)Against: The star faded by about 0.16 magnitudes per century from 1890 to 1989. 1. 2016[Schaefer: 1,338 B-band magnitudes show a fade of 0.193 ± 0.030 mag while nearby check stars are flat.](https://mysteriesdept.com/sources/SRC0D8E6V0C3X81/kic-8462852-faded-at-an-average-rate-of-0-164-0-013)For: The star faded by about 0.16 magnitudes per century from 1890 to 1989. 1. 2016[Hippke et al.: dASCH photometry has systematics of up to about 0.2 mag per century for most constant stars, so the trend is…](https://mysteriesdept.com/sources/SRC0D8E6V860VNG/a-statistical-analysis-of-the-accuracy-of-the-digitized)For: The century fade is a calibration artefact of plate photometry. 1. 2017[Michael Hippke et al.: sonneberg plates covering 1934-1995 show no step and no fade](https://mysteriesdept.com/sources/SRC0DDYCDVVCM9Z/sonneberg-plate-photometry-for-boyajians-star-in-two)Against: A single drop of about 0.1 mag across the 1953-1969 plate gap, not a steady century fade 1. 2018[Michael Castelaz: maria Mitchell Observatory plates give an independent +0.12 mag/century](https://mysteriesdept.com/sources/SRC0DDYCF5BWX7M/a-search-for-the-long-term-dimming-of-kic-8462852-on-maria)For: The star faded by about 0.16 magnitudes per century from 1890 to 1989. 1. 2018[Michael Castelaz: sonneberg plates covering 1934-1995 show no step and no fade](https://mysteriesdept.com/sources/SRC0DDYCF5BWX7M/a-search-for-the-long-term-dimming-of-kic-8462852-on-maria)Against: A single drop of about 0.1 mag across the 1953-1969 plate gap, not a steady century fade 1. 2025[Peter K. G. Williams: dR7 reproduces the 0.17 mag/century slope and the target is the steepest of 49 matched stars](https://mysteriesdept.com/sources/SRC0DDYCFZA4FXE/dasch-bringing-100-years-of-photographic-data-into-the-21st)For: The star faded by about 0.16 magnitudes per century from 1890 to 1989. 1. 2025[Peter K. G. Williams: matched stars do not share the target's post-1969 offset](https://mysteriesdept.com/sources/SRC0DDYCFZA4FXE/dasch-bringing-100-years-of-photographic-data-into-the-21st)Against: The century fade is a calibration artefact of plate photometry. 1. 2025[Peter K. G. Williams: both halves of the Harvard record are flat and the offset between them is not shared by matched stars](https://mysteriesdept.com/sources/SRC0DDYCFZA4FXE/dasch-bringing-100-years-of-photographic-data-into-the-21st)For: A single drop of about 0.1 mag across the 1953-1969 plate gap, not a steady century fade 1. Oct 2026[Session 1: took the question up again, proposed one answer, ran one test, found eight results bearing on its answers and worked on one of its sub-questions](https://mysteriesdept.com/records/SES0DDYJJVWGV9C/session-1-the-century-fade-re-tested-in-dasch-dr7-and-the) ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/tabbys-star/questions/QST0D8E77702V2V/did-the-star-fade-over-the-twentieth-century%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/tabbys-star/questions/QST0D8E77702V2V/did-the-star-fade-over-the-twentieth-century%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/tabbys-star/questions/QST0D8E77702V2V/did-the-star-fade-over-the-twentieth-century%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/tabbys-star/questions/QST0D8E77702V2V/did-the-star-fade-over-the-twentieth-century%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/tabbys-star/questions/QST0D8E77702V2V/did-the-star-fade-over-the-twentieth-century%23add-source) Where it fits Tabby's star (KIC 8462852) [**What causes the slow fading of the star?** ](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E76Z60339/what-causes-the-slow-fading-of-the-star)Key question · most likely a large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips [Did the slow fade continue, stop or reverse after 2018?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWMPSC2G/did-the-slow-fade-continue-stop-or-reverse-after-2018)No evidence yet · no answers yet **Did the star fade over the twentieth century?** You're here · 4 answers, inconclusive [ Ask a question under this one ] Under this one [Do the independent plate archives (Sonneberg, Sternberg, Maria Mitchell) agree with Harvard about the star's brightness from 1934 to 1990?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0DDYGWV073W7/do-the-independent-plate-archives-sonneberg-sternberg-maria)No evidence yet · no answers yet