Astronomy & Telescopes

The Search For The Inbetweeners: How Packed Are TESS Planetary Systems?

By Keith Cowing
Status Report
astro-ph.EP
November 7, 2024
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The Search For The Inbetweeners: How Packed Are TESS Planetary Systems?
Schematic view of the seven planetary systems studied in this work. In the upper panel, the location on the x-axis shows the orbital semi-major axis of the planets in question, on a linear scale, with the horizontal lines reaching out from the planet showing the range of its orbit from pericentre to apocentre. The size of the marker for each planet gives the observed radius, as presented in the discovery work, whilst the colour of the marker gives the measured mass for the planet. In the case of the planets orbiting HD 63433, no measured mass has been obtained to date, and we therefore plot an estimated mass for the two planets in that system, based on Figure 3 of Chen & Kipping (2017). In the case of TOI 1670 b, the mass given is an upper limit. The lower panel presents most of the same information (mass, radius, etc.), but shows the separation of the planetary systems in terms of their orbital periods, with the period of the inner planet in each system set to unity. The parent stars are shown sized relative to one another, but not to scale with their planets, and their colour in the plot denotes their effective temperatures, Teff. — astro-ph.EP

In this work, we examine seven systems discovered by TESS, to see whether there is any room in those systems for an additional planet (or several) to lurk unseen between the two planets already confirmed therein.

In five of those systems (namely HD 15337; HD 21749; HD 63433; HD 73583 and LTT 3780) we find that there is ample room for an undiscovered planet to move between those that have already been discovered. In other words, as they currently stand, those systems are not tightly packed. In stark contrast, the perturbative influence of the two known TOI-1670 planets is such that additional planets in between are ruled out. The final system, TOI 421, is more challenging.

In the vast majority of cases, adding an Earth-mass planet to that system between the orbits of the known planets caused catastrophic instability. Just ~1.1% of our simulations of the modified system proved dynamically stable on a timescale of one million years.

As a result, it seems that there is very little room between the two known planets in the TOI 421 system for an addition unseen world to exist, but the existence of such a planet can not be definitely ruled out on dynamical grounds alone.

Jonathan Horner, Robert A. Wittenmyer, Stephen R. Kane, Timothy R. Holt

Comments: 21 pages; 8 figures; accepted for publication in AJ on 31st October 2024
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2411.00245 [astro-ph.EP] (or arXiv:2411.00245v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2411.00245
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Submission history
From: Jonathan Horner
[v1] Thu, 31 Oct 2024 22:49:26 UTC (785 KB)
https://arxiv.org/abs/2411.00245
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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