A real planet has two suns
DOI: 10.1063/PT.5.010144
Among the press releases that arrived in my in box earlier this week were three touting a paper in today’s issue of Science. The paper’s title is precise and scientific: “Kepler-16: A transiting circumbinary planet.” The abstract begins as follows:
We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies.
What other planet has two suns? Tatooine! Even if I’d forgotten, the three press releases reminded me of the answer by evoking the home planet of Luke and Anakin Skywalker, the protagonist and antagonist, respectively, of the Star Wars saga.
In the Star Wars universe, Tatooine’s larger star, Tatoo I, is a yellowish white G1-type star of roughly 1 solar mass. Sources disagree on the spectral type of Tatoo II. Wikipedia says K; Wookieepedia says G2. Given that K stars are less massive than G stars, Tatoo II is at least 0.45 solar masses.
The two suns of Kepler-16, Star A and Star B, aren’t very different from Tatoo I and Tatoo II. The authors of the Science paper estimate Star A’s and Star B’s masses to be 0.69 and 0.20 solar masses, respectively. Although Kepler-16 is more like Saturn than Tatooine, Hoth , Earth, or any other habitable planet, the press releases’ comparison of Kepler-16 with Tatooine is not especially fanciful.
The comparison is also shrewd. Habitable planets were once the exclusive domain of science fiction. Now that humans have the technology to potentially discover them, the public, whose appetite for Star Wars, Star Trek, and other science fiction movies remains strong, is inspired by each milestone in the quest to find an Earth-like planet.
I received another planet-themed press release this week, from the American Astronomical Society’s division of planetary sciences. The release contained a statement from the DPS leadership entitled “DPS Statement on Budget Activities.” Its opening sentences read as follows:
The Division for Planetary Sciences of the American Astronomical Society, the world’s largest professional organization of planetary scientists, is following with close attention the on-going discussions within Congress, the Office of Management and Budget, and NASA over future funding for science, and for the James Webb Space Telescope. As budgetary priorities are set, it is important to consider the scientific bounty reaped by planetary missions in the last decade.
Besides summarizing the past scientific triumphs of planetary science and its future prospects, the statement explicitly mentions the public’s interest in things planetary. In the budget battles to come, that interest could prove influential, if not decisive.