# If the dips are real, what causes them? · HD 139139, the "Random Transiter" > Seven answers have been proposed. None is ahead on the evidence yet. Seven are still possible. Of the one narrower question under it, none is answered yet. Source: https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:57:35+00:00 --- **0** # If the dips are real, what causes them? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·7 answers·0·0 following **Seven answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Seven answers have been proposed. None is ahead on the evidence yet. Seven are still possible. Of the one narrower question under it, none is answered yet. ## Why it matters Every scenario the discoverers tried failed or needed special assumptions⁠[[1]](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139). A shallow, random transiter would be either a new kind of planetary system or a new kind of stellar variability. ## Answers 7 [**A disintegrating ultra-short-period planet whose dust tail is only sometimes thick enough to be seen.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S3HE78QH/a-disintegrating-ultra-short-period-planet-whose-dust-tail) Failed a test; not refuted outright Evidence: 2 against Disputed [**A planet in a close binary (S-type, eccentric and precessing) or around a binary (P-type), whose transits are…** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S2T07JV5/a-planet-in-a-close-binary-s-type-eccentric-and-precessing) Failed a test; not refuted outright Evidence: 2 against Disputed [**Dipper-star behaviour of the kind seen in young stars with disks, on star B and diluted by star A.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S4RG7PHD/dipper-star-behaviour-of-the-kind-seen-in-young-stars-with) Not tested enough to call either way Evidence: 1 for, 1 against Still possible [**Many dust-emitting asteroids or planetesimals on different orbits.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S48W44R1/many-dust-emitting-asteroids-or-planetesimals-on-different) Failed a test; not refuted outright Evidence: 1 against Disputed [**None of these.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S5ZJ6TCZ/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**Several planets, possibly with large transit-timing variations, around one or both stars.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S2AC0ZDR/several-planets-possibly-with-large-transit-timing) Failed a test; not refuted outright Evidence: 1 against Disputed [**Short-lived dark spots that appear within half an hour, last a few hours and vanish.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S5FY6FRB/short-lived-dark-spots-that-appear-within-half-an-hour-last) Not tested enough to call either way Evidence: 1 for Still possible [Show 2 more answers] ## History 1. 2019[Rappaport et al. puts forward: several planets, possibly with large transit-timing variations, around one or both stars.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al. puts forward: a planet in a close binary (S-type, eccentric and precessing) or around a binary (P-type), whose transits are…](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al. puts forward: a disintegrating ultra-short-period planet whose dust tail is only sometimes thick enough to be seen.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al. puts forward: many dust-emitting asteroids or planetesimals on different orbits.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al. puts forward: dipper-star behaviour of the kind seen in young stars with disks, on star B and diluted by star A.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al. puts forward: short-lived dark spots that appear within half an hour, last a few hours and vanish.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al.: simulations of an eccentric S-type planet always left a detectable periodicity.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)Against: A planet in a close binary (S-type, eccentric and precessing) or around a binary (P-type), whose transits are… 1. 2019[Rappaport et al.: only 7 per cent of more than 400 transits would show; simulations put this near the limit of detectability.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)Against: A disintegrating ultra-short-period planet whose dust tail is only sometimes thick enough to be seen. 1. 2019[Rappaport et al.: almost all dips have similar depths, which many independent bodies are unlikely to produce.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)Against: Many dust-emitting asteroids or planetesimals on different orbits. 1. 2019[Rappaport et al.: ten known dippers diluted by a factor of 15 do not resemble this light curve.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)Against: Dipper-star behaviour of the kind seen in young stars with disks, on star B and diluted by star A. 1. 2019[Rappaport et al.: star B's possible infrared excess would be hidden by the dilution.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)For: Dipper-star behaviour of the kind seen in young stars with disks, on star B and diluted by star A. 1. 2019[Rappaport et al.: the authors find no physical law violated and note such events could have gone unnoticed in other stars.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139)For: Short-lived dark spots that appear within half an hour, last a few hours and vanish. 1. Oct 2026[Session 1: worked on one of its sub-questions](https://mysteriesdept.com/records/SES0DD2HD6KQY7P/session-1-the-2025-tess-data-searched-and-the-k2-dips-put) ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them%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/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them%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/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them%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/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them%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/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them%23add-source) Where it fits HD 139139, the "Random Transiter" **If the dips are real, what causes them?** Key question · you're here [Which of the two stars dips?](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79S0BW0FXC/which-of-the-two-stars-dips)No evidence yet · 3 answers, untested [ Ask a question under this one ]