Exoplanetology: Exoplanets & Exomoons

An Earth-Mass Planet and a Brown Dwarf in Orbit Around a White Dwarf

By Keith Cowing

Status Report

astro-ph.EP

September 6, 2024

Filed under astro-ph.EP, astronomy, exoplanet, Keck Adaptive Optics, KMT-2020-BLG-0414, microlensing, red-giant phase, Stellar Cartography, white dwarf

An Earth-Mass Planet and a Brown Dwarf in Orbit Around a White Dwarf — llustration of possible system evolutionary histories under the Close-NE (a– c) and Wide-NE (d–f) models. Objects and orbits are not drawn to scale. Separations are representative values. (a) Initial configuration: close-in brown dwarf and wide-orbit planet. (b) Orbits expand due to host-star mass loss. AGB host star overflows Roche Lobe. Brown dwarf enters common envelope. (c) Common envelope ejected as brown dwarf orbit reduces to 0.2 au. Planetary orbit further expands. (d) Initial configuration: close-in planet and wide-orbit brown dwarf. (e) Orbits expand due to host-star mass loss. Brown dwarf and planet avoid interacting with the AGB host star. (f) Orbits continue to expand. — astro-ph.EP

Terrestrial planets born beyond 1-3 AU have been theorized to avoid being engulfed during the red-giant phases of their host stars.

Nevertheless, only a few gas-giant planets have been observed around white dwarfs (WDs) — the end product left behind by a red giant. Here we report on evidence that the lens system that produced the microlensing event KMT-2020-BLG-0414 is composed of a WD orbited by an Earth-mass planet and a brown dwarf (BD) companion, as shown by the non-detection of the lens flux using Keck Adaptive Optics (AO).

From microlensing orbital motion constraints, we determine the planet to be a 1.9±0.2 Earth-mass (M_⊕) planet at a physical separation of 2.1±0.2 au from the WD during the event. By considering the system evolutionary history, we determine the BD companion to have a projected separation of 22 au from the WD, and reject an alternative model that places the BD at 0.2 au.

Given planetary orbital expansion during the final evolutionary stages of the host star, this Earth-mass planet may have existed in an initial orbit close to 1 au, thereby offering a glimpse into the possible survival of planet Earth in the distant future.

OGLE-III, CFHT, and Keck-II imaging of KMT-2020-BLG-0414 taken before, during, and after the event. a, OGLE-III I-band image taken over 2002–2009. The event location is centered on the cross-hair. The OGLE-III baseline (catalog) object is 0.18′′ west and 0.01′′ south of the event location, as indicated by the white dot. b, CFHT/MegaCam i-band image taken 2.2 days after the peak of the event. c, Keck AO Ks-band imaging reveals that the blend flux associated with the OGLE-III baseline object is predominantly attributed to field stars to the west/north-west within 0.5″. — astro-ph.EP

Keming Zhang, Weicheng Zang, Kareem El-Badry, Jessica R. Lu, Joshua S. Bloom, Eric Agol, B. Scott Gaudi, Quinn Konopacky, Natalie LeBaron, Shude Mao, Sean Terry

Comments: Accepted. 25 pages, 7 figures, 4 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2409.02157 [astro-ph.EP] (or arXiv:2409.02157v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.02157
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Submission history
From: Keming Zhang
[v1] Tue, 3 Sep 2024 18:00:00 UTC (397 KB)
https://arxiv.org/abs/2409.02157

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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