We'd like to know a lot more than we do about how planets create magnetic fields. After all, a major motivation for exoplanet research (though hardly the only one) is to find out whether there is other life in the universe. A magnetic field can protect planetary atmospheres from the effects of the host star's stellar wind, a stream of charged particles that could disrupt life's formation. Planets in close orbits of a central star are going to be particularly vulnerable. But if protecting a planetary surface as well as keeping its atmosphere intact are powerful factors in understanding its evolution, learning more about planetary magnetic fields isn't going to be easy. Consider a new paper from François Soubiran (École Normale Supérieure, Lyon) and Burkhard Militzer (UC-Berkeley). They're digging into the question of magnetic fields on super-Earths, in this case planets up to three times the mass of our own world. The scientists believe that magnetic fields could emerge here,...

As the exoplanet hunt deepens, we're seeing how research efforts build upon each other, and how the findings of one investigation play into the planning for another. Kepler candidate planets, for example, have been confirmed using ground-based telescopes in radial velocity investigations, giving an independent check that the putative world is really there. TESS (Transiting Exoplanet Survey Satellite) will find planets that refine the target list for the James Webb Space Telescope, with extremely large telescope technology already in the wings. What we sometimes forget is that this collaborative effort has already built up a healthy momentum. Having maxed out Kepler (and K2 was an outstanding rehabilitation of a damaged spacecraft), the operations of TESS will focus on bright, nearby stars. The momentum of TESS and its contributions to the upcoming JWST should remind us that we then have the European Space Agency's CHEOPS (CHaracterising ExOPlanet Satellite) mission queuing up for...

It's a long name, but with the successful arrival of the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander on Mars, we now go to work on the planet's deep interior. With Centauri Dreams' deep space perspective, my thoughts quickly turn to other stellar systems. We've all seen how hard it is to land on Mars, and have looked up into the night sky to find the ruddy pinprick that marks its naked eye presence. Given our Solar System's scale, the task of getting humans to Mars looms as a major challenge. Image: Who can resist the first clear photo from a Mars mission? Not me. Credit: NASA. But suppose we were on a planet in the TRAPPIST-1 system. Here we have roughly Earth-sized planets packed into tight proximity around the parent red dwarf. TRAPPIST-1b is at 0.011 AU, while TRAPPIST-1c is at 0.015 AU. Even the most distant from the star, TRAPPIST-1h, orbits at 0.062 AU, so that these seven worlds are all closer to the host than Mercury in our...

Some relatives of a friend recently made me realize how routine exoplanet discoveries have become to the public. These are anything but astronomy buffs, but they know that planets can be found without ever being seen. My acquaintances may not understand radial velocity or transits to any high degree, but they accept that the methods are there and have proven reliable. "Someday," said one, "I guess we'll actually see one of these planets." The image below came as a surprise when I showed it to them. Here we do see a planetary system, four actual planets around the star HR 8799 and not just jiggles in Doppler signals or dips in a lightcurve. For me, what's astonishing here is not only that we can see planets despite their proximity to the host, but that we've accomplished this with telescopes on the ground. Adaptive optics -- correcting for turbulence in the atmosphere that would distort an astronomical image, using a guide star as a reference -- is the tool that is opening a new era...

Even today, I can well understand the reaction that Dennis Conti had when confronted with the prospect of finding a planet around another star with nothing more than an amateur instrument. Conti, who founded and now chairs the Exoplanet Section of the American Association of Variable Star Observers, was a newcomer to the transit method just a few years ago. "I thought, there's no way for someone with a backyard telescope to detect a planet going around a distant star," he says, looking back from the vantage of one now immersed in such observations. My boyhood 3-inch reflector was not a backyard instrument -- too many trees back there. So it became a front-yard telescope. Absent the technological innovations of the past five decades, I could only imagine vast instruments for studying objects around other stars. The transit method in exoplanet detection was a long way off, but the idea of seeing not a planet itself but a change in starlight as the planet crossed the face of its host...

The detection of a planet around Barnard’s Star really hits home for me. No, this isn’t a habitable world, but the whole topic of planets around this star has resonance for those of us who remember the earliest days of exoplanet study, which could be extended back to Peter van de Kamp’s work at Swarthmore’s Sproul Observatory in Pennsylvania. The astronomer thought he had found evidence for a 1.6 Jupiter mass planet in a 4.4 AU orbit there, based on what he interpreted as telltale wobbles in photographic plates of the star taken between 1916 and 1962. This work, ending in the early 1970s, turned out to be the result of errors in the instrument van de Kamp was using, but the buzz about possible planets around Barnard’s Star had been sufficient to create a small crest of enthusiasm for exoplanet studies in general. The British Interplanetary Society saw in Barnard’s Star a target worth investigating, and designed their Daedalus star probe around a mission there. In any case, van de...

When astronomers talk about metals, they're using the term in a specific sense. A metal in stellar terms is any element heavier than helium. Thus iron, silicon, magnesium and carbon qualify, all elements that are components of small, rocky planets. It was iron that John Michael Brewer (Yale University), Debra Fischer and colleagues singled out as a proxy in their recent work on the metal content of exoplanet systems. The work focuses specifically on compact, multi-planet systems as one of several system architectures found in close orbit of a host star. What's interesting here is that these domains seem mutually exclusive, or almost so. Unlike our Solar System, a system with multiple planets on tight orbits can squeeze its worlds into a region as close as Mercury. Likewise near the host star, we sometimes find massive planets in close orbits, known as 'hot Jupiters.' Few of these have close planetary neighbors, and few compact multi-planet systems have massive planets. And there is...

We’ve long been interested in how the Earth got its oceans, with possible purveyors being comets and asteroids. The idea trades on the numerous impacts that occurred particularly during the Late Heavy Bombardment some 4.1 to 3.8 billion years ago. Tuning up our understanding of water delivery is important not only for our view of our planet’s development but for its implications in exoplanet systems with a variety of different initial conditions. Image: This view of Earth’s horizon was taken by an Expedition 7 crewmember onboard the International Space Station, using a wide-angle lens while the Station was over the Pacific Ocean. Credit: NASA. But the picture becomes more complex when we compare regular hydrogen atoms (one proton, one electron) with ‘heavy hydrogen,’ or deuterium atoms. The latter have a neutron in addition to a proton in the nucleus. A recent paper in the Journal of Geophysical Research digs into isotope ratios, the ratio of deuterium to ordinary hydrogen atoms,...