The Egyptian monarch Khufu was the second pharaoh of the Fourth Dynasty, which dates him back to the earlier years of the Old Kingdom period around the 26th century BC. I mention this figure, about which all too little is known, because his name is a link between the great monuments of an early culture (Khufu seems to have commissioned the Great Pyramid of Giza) and present-day engineering. Imagine how wondrous the Great Pyramid would have been to the average passerby of the time, and then realize that Khufu's Hellenized name was Cheops, a monicker reflected in the acronym of our recently launched CHEOPS exoplanet observatory. I always enjoy untangling acronyms, some of which are more labored than others. Did you know, for example, that the name of the Japanese IKAROS solar sail is actually an acronym standing for Interplanetary Kite-craft Accelerated by Radiation Of the Sun? Then there's OSIRIS-REx (also satisfyingly Egyptian), which weighs in as Origins, Spectral Interpretation,...

An Australian amateur astronomer named Thiam-Guan Tan has made a name for himself in the realm of exoplanets. Tan participated in the discovery of an exoplanet that may orbit within its star's habitable zone. LHS 1140 b is a super-Earth some 41 light years from Earth that orbits a red dwarf star. Back in September of 2016, with a number of professional observatories looking at the host star, Tan provided key data to help verify the existence of LHS 1140b. "It was fortunate that I was able to catch a transit," said Tan, a retired engineer with a 12-inch telescope who has also discovered several supernovae. He is quoted in a newspaper called The West Australian as saying "That night, the Centre for Astrophysics had lined up five other telescopes across Australia and Hawaii to observe but they were all clouded out." Tan's work with exoplanet transits continues, an illustration of the role that talented amateurs with affordable equipment (Tan's telescope cost $15,000) can play. Image:...

Calling it a ‘chance discovery,’ the University of Warwick’s Boris Gänsicke recently presented the results of his team’s study of some 7,000 white dwarf stars, all of them cataloged by the Sloan Digital Sky Survey. One drew particular interest because chemical elements turned up in spectroscopic studies indicating something unusual. Says Gänsicke, “We knew that there had to be something exceptional going on in this system, and speculated that it may be related to some type of planetary remnant.” And that makes the star WDJ0914+1914 an example of what a stellar system that survived, at least partially, the red giant phase of its host star might look like as a planet orbits the Earth-sized white dwarf. This work, which draws on data from the European Southern Observatory’s X-shooter spectrograph at the Very Large Telescope in Chile, confirms hydrogen, oxygen and sulphur associated with the white dwarf, all found in a disk of gas around the star rather than being present in the white...

The interest in 'Oumuamua and comet 2I/Borisov makes it clear that interstellar neighbors wandering into our system generate loads of media coverage. And why not: Here is a way to study material from another stellar system while remaining within our own. 2I/Borisov, for example, reaches its closest approach to Earth in early December, closing to within roughly 300 million kilometers. Whatever pushed an object like this out of the parent system cannot be known, but we're likely dealing with gravitational disruption related to planets in the birth system. But more about that in a moment. For thanks to Yale University astronomers Pieter van Dokkum, Cheng-Han Hsieh, Shany Danieli, and Gregory Laughlin, we have a fine new image of 2I/Borisov. This was taken on November 24 using the W.M. Keck Observatory's Low-Resolution Imaging Spectrometer in Hawaii. The tail of the comet, according to van Dokkum, is about 160,000 kilometers long. Note the size comparison below to be reminded, as always,...

Our fascination with Alpha Centauri doubtless propels at least some of the recent interest in binary star systems, as we ponder the chances for habitable worlds around the nearest stars. But given that the population of binary or multiple star systems in our galaxy is as high as it is (multiple systems are common, and about 50 percent of stars have binary companions), determining the factors that influence habitability in this environment has much broader significance. A new study out of the Georgia Institute of Technology has been looking at the issue by modeling an Earth twin in various binary scenarios. So how does Alpha Centauri fare? We can find habitable zones in the Centauri A/B system, and into these the researchers introduced a simulated Earth around Centauri B to examine its axis dynamics. They also investigate the dynamical evolution of planets within the habitable zone of either star, generalizing from these results to the larger binary star population. The issue to be...

While the majority of exoplanet-hosting stars discovered so far are single, we do have multiple star systems in various configurations with planetary companions. This is fertile ground for study, and not just because the nearest stellar system, Alpha Centauri, contains a tight binary pair that is being closely investigated for planets. The third star here is, of course, Proxima Centauri, around which we already know of the existence of a planet in the habitable zone. The much broader question is, how likely are multiple star systems to host planets? Tackling this question in a new study is Markus Mugrauer (Friedrich Schiller University, Jena), who has been investigating how the existence of multiple stars in a system affects the formation and development of planets. Mugrauer has been working with the second data release from the European Space Agency’s Gaia mission (made available in April of last year). This release contains data collected by Gaia during the first 22 months of its...

The question of habitability on planets around M-dwarfs is compelling, and has been a preoccupation of mine ever since I began working on Centauri Dreams. After all, these dim red stars make up perhaps 75 percent of the stars in the galaxy (percentages vary, but the preponderance of M-dwarfs is clear). The problems of tidal lock, keeping one side of a planet always facing its star, and the potentially extreme radiation environment around young, flaring M-dwarfs have fueled an active debate about whether life could ever emerge here. At Northwestern University, a team led by Howard Chen, in collaboration with researchers at the University of Colorado Boulder, NASA's Virtual Planet Laboratory and the Massachusetts Institute of Technology, is tackling the problem by combining 3D climate modeling with atmospheric chemistry. The paper on this work, in press at the Astrophysical Journal, examines how general circulation models (GCM) have been able to simulate the large-scale circulation and...

It's good to see the European Space Agency's ARIEL mission getting a bit more attention in the media. The Atmospheric Remote-sensing Infrared Exoplanet Large-survey was selected earlier this year as an ESA science mission, scheduled for launch in 2028. Here the goal is to cull a statistically large sample of exoplanets to examine their evolution in the context of their parent stars. Giovanna Tinetti (University College London) is principal investigator. I would urge seeing ARIEL in the context of a different kind of evolution, that being the gradual growth in our technologies as we continue getting closer to studying the atmospheres of terrestrial-class worlds. For while ARIEL cannot achieve this feat -- its focus is on exoplanets of Jupiter-mass down to super-Earths, all on close orbits, with temperatures greater than 320 Celsius -- it leverages the fact that high temperature atmospheres keep their various interesting molecules in continual circulation, rather than letting them sink...

We often think of Jupiter as a mitigating influence on asteroid or comet strikes in the inner system, its gravity changing the trajectories of potential impactors. That would make gas giants a powerful determinant of the survivability of Earth analogues, at least in terms of habitability. While we continue to investigate the question, it's interesting to consider the damage a gas giant on an elliptical orbit might do to habitable zone planets. Stephen Kane (UC-Riverside), working with Caltech astronomer Sarah Blunt, decided to find out what would happen if, in their modeling, they introduced an elliptical gas giant into the system of an Earth twin. You may remember Kane's work earlier this year combining radial velocity with direct imaging methods to find three gas giants that had been previously unobserved (citation below). The monitoring of ten target stars continues even as this new work is published. We're beginning to find more planets at ever larger distances from their stars...