Although many of the nearby stars we will study for signs of life are older than the Sun, we do not know how long it takes life to emerge or, for that matter, how likely it is to emerge at all. As we saw yesterday, that means plugging values into Drake-like equations to estimate the possibility of detecting an alien civilization. We can't rule out the possibility that we are surrounded by planets teeming with non-sentient life, fecund worlds that have no heat-producing technologies to observe. Fortunately, we are developing the tools for detecting life of the simplest kinds, so that while a telescope of Colossus class can be used to detect technology-based heat signatures, it can also be put to work looking for simpler biomarkers. Svetlana Berdyugina (Kiepenheuer Institut für Sonnenphysik and the University of Freiburg), now a visiting scientist at the University of Hawaii, has been leading a team on such detections and spoke about surface imaging of Earth-like planets at the recent...

Let me call your attention to the PLANETS telescope, now seeking a funding boost through an ongoing Kickstarter campaign. Currently about halfway built, the PLANETS (Polarized Light from Atmospheres of Nearby ExtraTerrestrial Systems) instrument is located on the 10,000 foot Haleakala volcano on the island of Maui. When completed, it will be the world's largest off-axis telescope (at 1.85 meters) for night-time planetary and exoplanetary science. And it's part of a much larger, scalable effort to find life around nearby stars in as little as a decade. https://www.youtube.com/watch?v=Y3f-q-hKff0&w=500&h=416 An off-axis design removes obstructions to the light path like the secondary mirror supports that can cause diffraction effects and lower image quality in axially symmetric reflective telescopes. Here light from the primary mirror is deflected slightly out of the incoming lightpath, limiting diffraction and scattered light. The PLANETS Foundation, the international collaboration of...

The boundary between brown dwarf and planet is poorly defined, although objects over about 13 Jupiter masses (and up to 75 Jupiter masses) are generally considered brown dwarfs. Brown dwarfs do not reside, like most stars, on the main sequence, being not massive enough to sustain nuclear fusion of hydrogen in their cores, although deuterium and lithium fusion is a possibility. But new work on a brown dwarf called SIMP J013656.5+093347 (mercifully shortened to SIMP0136) is giving us fresh insights into the planet/dwarf frontier. The intriguing object is found in the constellation Pisces, the subject of previous studies that focused on its variability, which has been interpreted as a signature of weather patterns moving into and out of view during its rotation period of 2.4 hours. Now Jonathan Gagné (Carnegie Institution for Science) and an international team of researchers have put new constraints on SIMP0136, finding it to be an object of planetary mass. Image: Lead author...

Nine years ago in a piece titled Asteroid Belts, Possible Planets Around Epsilon Eridani, I discussed work that Massimo Marengo was doing on the nearby star, examining rings of material around Epsilon Eridani and considering the possibilities with regard to planets. Marengo (now at Iowa State University) has recently been working with Kate Su (University of Arizona) and other colleagues, using the SOFIA telescope (Stratospheric Observatory for Infrared Astronomy) to help us refine our understanding of the evolving planetary system. Image: Astronomers (left to right) Massimo Marengo, Andrew Helton and Kate Su study images of epsilon Eridani during their SOFIA mission. Credit: Massimo Marengo. The researchers used the 2.5-meter telescope aboard the Boeing 747SP jetliner to collect data about the star, working at 45,000 feet in a region above most of the atmospheric water vapor that absorbs the infrared light being studied. Epsilon Eridani is a bit over 10 light years from the Sun, and...

I have a special enthusiasm for microlensing as a means of exoplanet discovery. With microlensing, you never know what you’re going to come up with. Transits are easier to detect when the planet is close to its star, and hence transits more frequently. Radial velocity likewise sends its loudest signal when a planet is large and close. Microlensing, detecting the ‘bending’ of light from a background object as it is affected by a nearer star’s gravitational field, can turn up a planet whether near to its star or far, and in a wide range of masses. It can also be used to study planetary populations as distant as the galactic bulge and beyond. Now we have news of a cold planet about the size of the Earth orbiting what may turn out to be a brown dwarf, and is in any case no more than 7.8 percent the mass of our Sun. Is this an object like TRAPPIST-1, the ultra-cool dwarf star we’ve had so much to say about in recent days as investigations of its 7 planets continue? If so, the planet...

What to make of Fergus Simpson’s new paper on waterworlds, suggesting that most habitable zone planets are of this type? If such worlds are common, we may find that most planets in the habitable zones of their stars are capable of evolving life, but unlikely to host technological civilizations. An explanation for the so-called ‘Fermi Paradox’? Possibly, but there are all kinds of things that could account for our inability to see other civilizations, most of them covered by Stephen Webb in his If the Universe Is Teeming with Aliens … Where Is Everybody? (2nd ed., Springer 2015), which offers 75 solutions to the problem. Simpson (University of Barcelona) makes his case in the pages of Monthly Notices of the Royal Astronomical Society, arguing that the balance maintained by a planetary surface with large amounts of both land and water is delicate. The author’s Bayesian statistical analysis suggests that most planets are dominated either by water or land, most likely water. Earth may,...

A closely packed planetary system like the one we’ve found at TRAPPIST-1 offers intriguing SETI possibilities. Here a SETI search for directed radio transmissions aimed at the Earth gives way to an attempt to overhear ongoing activity within another stellar system. For it’s hard to conceive of any civilization developing technological skills that would turn away from the chance to make the comparatively short crossing from one of the TRAPPIST-1 worlds to another. Our more spread out system is challenging for a species at our level of technological development, but a colony on Mars or an outpost on Titan would surely produce intense radio traffic as it went about daily operations and reported back to Earth. Could TRAPPIST-1 be home to similar activities? The SETI Institute has continued to investigate the prospect, starting with ‘eavesdropping’ observations at 2.84 and 8.2 GHz in early April. Image: A size comparison of the planets of the TRAPPIST-1 system, lined up in order of...