The New Yorker recently started “Elements”, a science and technology blog. Their most recent contributor is…me! I covered a strange little controversy begun when the International Astronomical Union (IAU), a professional society with over 10 thousand members, decided to pick a fight with a company offering a contest to name exoplanets. That company, Uwingu, decided to fight back, and the exchange highlighted a set of philosophical questions about who gets to name new worlds.
However, the International Astronomical Union, a society of professional astronomers, strongly disapproves of the entire concept, and published a statement to that effect (though without mentioning Uwingu by name). According to its Web site, the I.A.U.’s tasks include serving “as the internationally recognized authority for assigning designations to celestial bodies and surface features on them.” The process of naming new objects is complicated (the Web précis of the document is itself formidable), and the I.A.U. press release claims exclusive rights to decide what a planet is called—even over the wishes of the scientist or scientists who discovered it. [Read more…]
Now, can I get a picture of Eustace Tilley wearing a bowler hat?
Imagine a planet 7 times the mass of Jupiter, hot enough to glow slightly, and containing dusty clouds of carbon monoxide and water. That planet is HR 8799c, one of the few worlds outside our Solar System which astronomers have been able to image directly. Part of the reason for its weirdness is its youth: the planet is only about 30 million years old, compared to the Solar System’s 4.5 billion-year age. In fact, up until an observation published this week, astronomers couldn’t be sure HR 8799c was even a planet: many of its properties make it look more like a brown dwarf, the star-like objects not quite massive enough to shine via nuclear fusion. Despite its strange aspects, the planet could help astronomers understand how the HR 8799 system formed—and reveal information about the origins of our own Solar System.
Quinn Konopacky, Travis Barman, Bruce Macintosh, and Christian Marois performed a detailed spectral analysis of the atmosphere of the possible exoplanet. They compared their findings to the known properties of a brown dwarf and concluded that they don’t match—it is indeed a young planet. Chemical differences between HR 8799c and its host star led the researchers to conclude the system likely formed in the same way the Solar System did. [Read more…]
We often focus on the search for Earth-like planets (whatever that means) when we talk about exoplanets: planets orbiting other stars. However, another important goal is to categorize as many planetary systems as possible, determining what kind of planets orbit what sort of stars. That catalog is gradually revealing the way planets form, and how the detailed history of each system leads to what we observe today. For example, Mercury is the smallest planet in the Solar System, but it’s far from being the smallest spherical body—and nobody expects it to be the smallest planet of any star system. Now a new observation has found an exoplanet noticeably smaller than Mercury, which will help us fill in the catalog a little more.
Now researchers may have found the smallest exoplanet yet, a world with a diameter about 80 percent of Mercury’s. This planet candidate, named Kepler-37b, orbits very close to its star: its orbital radius is about 1/4 the size of Mercury’s, so it takes only about 13 days to zip around. Thomas Barclay and collaborators also identified two other planets in the same system—labeled Kepler-37c and Kepler-37d—one of which is slightly larger than Mars, and the other which has twice Earth’s diameter. [Read more…]
The orbiting Kepler observatory has been a remarkably successful project since its inception. By watching one small patch of the sky continuously, Kepler has enabled astronomers to discover upward of 2300 possible exoplanets—planets orbiting other stars. While many of those candidates likely are not actually planets, follow-up observations have confirmed 854 exoplanets as of December 28, 2012. The American Astronomical Society meeting, happening as I type this post, is devoting about 30% of its sessions to discussing recent exoplanet discoveries. This is an astoundingly rich field of study!
However, it’s also one that is remarkably accessible. Through the citizen science program Planet Hunters, non-scientists helped discover 42 planet candidates, 15 of which may lie in their system’s habitable zone—the region at which liquid water may exist on the surface.
The Planet Hunters identified 42 exoplanet candidates, including 33 with at least three transits—the more transits we can observe, the more reliable the identification as a planet, and the better the estimates of orbital characteristics. Forty of the potential exoplanets have orbits longer than 100 days, and 9 may have orbital periods greater than 400 days, placing them farther out than most previously identified worlds. [Read more…]
How quickly things can change in science: just a few years ago, we were barely able to talk about the diversity of planetary systems. Now, we are able to distinguish between planets orbiting in tight binary systems from those in wide binaries. Additionally, exoplanets in tight binaries can orbit either both stars together (circumbinary, or Tatooine-like systems) or one of two stars, where the second might be like a Jupiter in the system. In wide binaries, the second star is so far away that it’s barely attached to the system, but a new set of simulations may show that may actually lead to greater instability than experienced by planets in tight binaries.
Nathan A. Kaib, Sean N. Raymond, and Martin Duncan ran extensive computer simulations to model exoplanets residing in wide binary systems. They found that perturbations from other stars outside the binary system had a profound effect on the shape of the system’s orbits. In some cases, planets were ejected from the system entirely or ended up in larger or highly eccentric (elongated) orbits. Based on these results, the researchers argued that some of the observed exoplanet systems with eccentric orbits may actually reside in wide binary systems where we haven’t yet detected the companion stars. [Read more, and watch the video!]
Many star systems seem to resemble our own Solar System: the planets orbit their host star in the same direction that the star spins. Admittedly, the data is still sparse: it’s not always possible to get that measurement. The brief version: you need the planet to transit or briefly eclipse its host star, and you need to be able to measure the small change in the star’s spectrum. This is most easily done when the planet is close in and relatively large—a class of exoplanets known as hot Jupiters, since they are big and close enough to experience extreme temperatures. Surprisingly, some of these hot Jupiters orbit their stars the wrong way, and this misalignment is difficult to explain within the standard theory of planet formation. However, a new model suggests that if the original star system had two stars, it would mess up the protoplanetary disk, leaving orbits askew.
In this revised model, strongly misaligned orbits are the result of another factor that influenced planet formation: a second star in the system. The gravitational influence of the companion star twisted the orbit of the exoplanet, pulling it out of alignment. And, in many cases, the star would leave little trace beyond the altered orbits: Sun-like stars often form in pairs or larger assemblies, but some of them evaporate over time. [Read more….]