# Which of the two stars dips? · HD 139139, the "Random Transiter" > Three answers have been proposed. None is ahead on the evidence yet. Three are still possible. Source: https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79S0BW0FXC/which-of-the-two-stars-dips Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-29T13:14:08+00:00 --- **0** # Which of the two stars dips? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·Part of [If the dips are real, what causes them?](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them)·3 answers·0·0 following **Three answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Three answers have been proposed. None is ahead on the evidence yet. Three are still possible. ## Why it matters Both stars fall in the same K2 aperture; the size of the occulters, and so the class of explanation, changes by a factor of about ten depending on the host⁠[[1]](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139). ## Answers 3 [**None of these.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S6Q04MXH/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**Star A, HD 139139, with occulters about twice Earth's radius.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S67C1PGW/star-a-hd-139139-with-occulters-about-twice-earths-radius) Not tested enough to call either way Evidence: none yet Still possible [**Star B, the fainter K star, with occulters of one to two Jupiter radii or deep intrinsic dips.** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/answers/ANS0D79S6F66ZK9/star-b-the-fainter-k-star-with-occulters-of-one-to-two) Not tested enough to call either way Evidence: none yet Still possible ## What would settle it 1. If new dips are caught, take simultaneous resolved two-colour photometry: on star A the dips stay about 200 ppm; on star B the same light loss is about 3 % of B's own light and redder. ## History 1. 2019[Rappaport et al. puts forward: star A, HD 139139, with occulters about twice Earth's radius.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. 2019[Rappaport et al. puts forward: star B, the fainter K star, with occulters of one to two Jupiter radii or deep intrinsic dips.](https://mysteriesdept.com/sources/SRC0D79RTR64N25/the-random-transiter-epic-249706694-hd-139139) 1. Oct 2026[Session 1: took the question up again and ran one test](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/QST0D79S0BW0FXC/which-of-the-two-stars-dips%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/QST0D79S0BW0FXC/which-of-the-two-stars-dips%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/QST0D79S0BW0FXC/which-of-the-two-stars-dips%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/QST0D79S0BW0FXC/which-of-the-two-stars-dips%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/QST0D79S0BW0FXC/which-of-the-two-stars-dips%23add-source) Where it fits HD 139139, the "Random Transiter" [**If the dips are real, what causes them?** ](https://mysteriesdept.com/mysteries/hd-139139-random-transiter/questions/QST0D79S04202NJ/if-the-dips-are-real-what-causes-them)Key question · 7 answers, inconclusive **Which of the two stars dips?** You're here · 3 answers, untested [ Ask a question under this one ]