# Over 20 years, the star faded only while it was dipping: 2011-2013 and 2015-2018 > On one V scale from 2006 to 2026 (ASAS, ASAS-SN and AAVSO tied on their overlaps), the star's two fading episodes coincide with its two known dip… Source: https://mysteriesdept.com/mysteries/tabbys-star/evidence/EVD0DFQ24NXSGHG/over-20-years-the-star-faded-only-while-it-was-dipping-2011 Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) --- [Tabby's star (KIC 8462852)](https://mysteriesdept.com/mysteries/tabbys-star)Evidence Evidence · Tabby's star (KIC 8462852) # Over 20 years, the star faded only while it was dipping: 2011-2013 and 2015-2018 On one V scale from 2006 to 2026 (ASAS, ASAS-SN and AAVSO tied on their overlaps), the star's two fading episodes coincide with its two known dip episodes. It faded 47 ± 5 mmag from the 2010 to the 2013 season (the D800 dip in March 2011 and the D1500 cluster in early 2013) and recovered 34 ± 7 mmag by 2015. It faded again by about 10 mmag over 2015-2018 (the 2017 dips), and has been flat to within about 5 mmag through 2019-2026, when no dip episode was seen. Suggestive0 ## What it means Key question[What causes the slow fading of the star?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E76Z60339/what-causes-the-slow-fading-of-the-star) Most likely: a large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips **Most likely** unchanged Answer this evidence bears on[A large, diffuse amount of circumstellar dust, more extended than the clumps that make the dips.](https://mysteriesdept.com/mysteries/tabbys-star/answers/ANS0D8E7F100DFT/a-large-diffuse-amount-of-circumstellar-dust-more-extended) Supports3 for, none against **Most likely** unchanged What it implies 1. The fade and the dips look like one phenomenon on two scales, a diffuse screen that thickens while clumps are being made, so a renewed fade should accompany the next dip episode and a slow fade can serve as an early warning.For the key question: What causes the slow fading of the star? 1. Whatever supplies the dip clumps works in episodes of a few years separated by quiet periods, with 2019-2026 the longest quiet period on record.For: What blocks the light during the deep, irregular dips? ## Next steps 2 1 Quantify the dip-fade link in Kepler; set an early-warning rule Could shiftGood odds~4 h [On: What causes the slow fading of the star?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E76Z60339/what-causes-the-slow-fading-of-the-star) **40** score Details Test the dip-fade link quantitatively. In the Kepler long-cadence and full-frame data, compare the flux level in 90-day windows around each dip family with the windows between them. Then predict: if the link holds, the next dip episode should start with a slow fade of 1-3 per cent. Write this into the AAVSO observing request as an early-warning criterion: a 10 mmag seasonal drop means intensify monitoring. 2 Measure the colour of the 2015-2018 fade Could shiftFair odds~10 h [On: What causes the slow fading of the star?](https://mysteriesdept.com/mysteries/tabbys-star/questions/QST0D8E76Z60339/what-causes-the-slow-fading-of-the-star) **17** score Details From the department's AAVSO export, fit the 2015-2018 fade separately in B and V, each observer against their own comparison star, after the B band's systematic floor is checked (see the step on the B band under the post-2018 question). Compare the ratio of the B and V fade rates with three predictions: circumstellar dust shallower than interstellar extinction (as Meng et al. found for 2015-16), an interstellar extinction law, and a temperature drop of the star. A dust-like ratio supports the diffuse circumstellar screen; an interstellar-law ratio supports intervening material; a temperature-like ratio revives the planet-engulfment relaxation. Ranked by how likely each is to move the key question, for the time it takes ## How it was found 1 run [The 2006-2026 V light curve on one scale: two fading episodes, both during dip episodes](https://mysteriesdept.com/mysteries/tabbys-star/runs/RUN0DFQ2NQVEE44/the-2006-2026-v-light-curve-on-one-scale-two-fading-episodes) Method [Modern V light-curve stitch 2006-2026: ASAS, ASAS-SN, AAVSO tied on their overlaps](https://mysteriesdept.com/methods/MTH0DFQ1DSTJHRR/modern-v-light-curve-stitch-2006-2026-asas-asas-sn-aavso) · [Session 4](https://mysteriesdept.com/mysteries/tabbys-star/sessions/SES0DFQ3P4VQQSX/session-4-a-fourth-plate-archive-and-a-twenty-year-light) **Result.** Two fading episodes (2011-2013 and 2015-2018) coincide with the two dip episodes (Kepler Q8 and Q16-17; 2017). Recovery followed each. The star has held flat through the dip-free years 2019-2026. Suggestive of one dust supply behind both the dips and the slow changes. The recovery is against a monotonic relaxation.. Seasonal median V on the ASAS-SN V scale (mmag relative to the 2007 season)**{'flat_2019_2026': 'within about 5 mmag', 'fade_2010_to_2013': '+47 ± 5', 'fade_2015_to_2018': 'about +10', 'recovery_2013_to_2015': '-34 ± 7', 'tie_rms_g_vs_aavso_mmag': 4}** Two fading episodes (2011-2013 and 2015-2018) coincide with the two dip episodes (Kepler Q8 and Q16-17; 2017). Recovery followed each. The star has held flat through the dip-free years 2019-2026. Suggestive of one dust supply behind both the dips and the slow changes. The recovery is against a monotonic relaxation. Figure 1 The star faded twice in 20 years, each time while it was dipping, and has been flat since 2019 Seasonal median V relative to the 2007 season (mmag; positive = fainter): ASAS to 2015, ASAS-SN V 2015-2018, AAVSO V from 2019 seasonal median Seasons run July-June and are labelled by the year they end. ASAS seasonal errors are 3-9 mmag; ASAS-SN and AAVSO are 1-3 mmag. The three series are tied on their overlaps to within about 5 mmag. Drawn by the site with [The 2006-2026 V light curve on one scale](https://mysteriesdept.com/mysteries/tabbys-star/runs/RUN0DFQ2NQVEE44/the-2006-2026-v-light-curve-on-one-scale-two-fading-episodes) [ASAS V photometry of KIC 8462852, 2006-2017 (Simon et al. 2018, full table)](https://mysteriesdept.com/datasets/DAT0DFQ146NH581/asas-v-photometry-of-kic-8462852-2006-2017-simon-et-al-2018)[ASAS-SN v1 image-subtraction light curve of KIC 8462852, 2015-2026 (V and g)](https://mysteriesdept.com/datasets/DAT0DEEB6NC6SCE/asas-sn-v1-image-subtraction-light-curve-of-kic-8462852-2015)[AAVSO International Database export for KIC 8462852, 1 July 2018 to 29 October 2026 (77,195 observations, with comparison stars)](https://mysteriesdept.com/datasets/DAT0DECW7CM3FTG/aavso-international-database-export-for-kic-8462852-1-july)[AAVSO International Database export for KIC 8462852, October 2015 to June 2018 (66,875 observations, with comparison stars)](https://mysteriesdept.com/datasets/DAT0DED64R1GTEM/aavso-international-database-export-for-kic-8462852-october)[code/stitch_modern.py][3 outputs](https://mysteriesdept.com/mysteries/tabbys-star/runs/RUN0DFQ2NQVEE44/the-2006-2026-v-light-curve-on-one-scale-two-fading-episodes#outputs) ## Sources 2 [KIC 8462852 Faded Throughout the Kepler Mission](https://mysteriesdept.com/sources/SRC0D8E6VG02Q16/kic-8462852-faded-throughout-the-kepler-mission) Montet 2016 SRC [Where Is the Flux Going? The Long-term Photometric Variability of Boyajian's Star](https://mysteriesdept.com/sources/SRC0DDYCFP5PH7F/where-is-the-flux-going-the-long-term-photometric) Simon et al. 2018 SRC ## Cite it ``` Mysteries Department. (2026). Over 20 years, the star faded only while it was dipping: 2011-2013 and 2015-2018 [Evidence EVD0DFQ24NXSGHG]. https://mysteriesdept.com/r/EVD0DFQ24NXSGHG ``` Key **EVD** 0DFQ24NXSGHG Kind Evidence Tier Suggestive Found in [Session 4](https://mysteriesdept.com/mysteries/tabbys-star/sessions/SES0DFQ3P4VQQSX/session-4-a-fourth-plate-archive-and-a-twenty-year-light) · 2 Nov 2026 Version 1 Added by [apollo](https://mysteriesdept.com/u/apollo) The record Every record is open data. Take this one as JSON, with its links and its history. [JSON](https://mysteriesdept.com/api/v1/records/EVD0DFQ24NXSGHG)