I want to send along best wishes for the season to all of you. Centauri Dreams started as a book and became a study guide for me as I tried to keep up with ongoing developments in deep space research. But turning the site into a community, which I did in 2005 by adding comments, has been what really made it go, as I've continued to learn from the discussions between readers, finding new resources and different insights I would never have achieved on my own. So thank all of you for this continuing gift, and may this holiday season be the prelude to great discoveries ahead.

Seeing oceans, continents and seasonal changes on an exoplanet pushes conventional optical instruments well beyond their limits, which is why NASA is exploring the Sun's gravitational lens as a mission target in what is now the third phase of a study at NIAC (NASA Innovative Advanced Concepts). All of this builds upon the impressive achievements of Claudio Maccone that we've recently discussed. Led by Slava Turyshev, the NIAC effort takes advantage of light amplification of 1011 and angular resolutions that dwarf what the largest instruments in our catalog can deliver, showing what the right kind of space mission can do. We're going to track the Phase III work with great interest, but let's look back at what the earlier studies have accomplished along the way. Specifically, I'm interested in mission architectures, even as the NASA effort at the Jet Propulsion Laboratory continues to consider the issues surrounding untangling an optical image from the Einstein ring around the Sun....

Red dwarf stars have fascinated me for decades, ever since I learned that a potentially habitable planet around one might well be tidally locked. Trying to imagine a living world with a sun that didn’t move in the sky was the kind of exercise that I love about science fiction, where playing with ideas always includes a vivid visual element. What kind of landscapes would a place like this offer to the view? What kind of weather would tidal lock conjure? Stephen Baxter’s novel Proxima (Ace, 2014) is a wonderful exercise in such world-building. Thus my continuing interest in the splendid work being done by RedDots, which takes as its charter the detection of terrestrial planets orbiting red dwarfs near the Sun. You’ll recall that this is the team that discovered Proxima Centauri b, a star under increased scrutiny of late as other potential planetary signals are examined. RedDots also gave us Barnard’s Star b and has found three planets around the red dwarf GJ 1061. Now we learn about a...

Somehow it feels as if the Hubble Space Telescope has been with us longer than the 30 years now being celebrated. But it was, in fact, on April 24, 1990 that the instrument was launched aboard the space shuttle Discovery, being deployed the following day. 1.4 million observations have followed, with data used to write more than 17,000 peer-reviewed papers. It's safe to say that Hubble's legacy will involve decades of research going forward as its archives are tapped by future researchers. That's good reason to celebrate with a 30th anniversary image. I'm reminded that the recent work we looked at on the interstellar comet 2I/Borisov involved Hubble as part of the effort that detected the highest levels of carbon monoxide ever seen in a comet so close to the Sun. Using Hubble data is simply a given wherever feasible. And given yesterday's article on star formation and conditions in the Sun's birth cluster that may have produced leftover material from other stellar systems still...

Learning about the orbital tilt of a distant exoplanet may help us understand how young planets evolve, and especially how they interact with both their star and other nearby planets. Thus the question of ‘hot Neptunes’ and the mechanisms that put them in place.The issue has been under study since 2004. Are we looking at planets laden with frozen ices that have somehow migrated to the inner system, or are these worlds that formed in place, so that their heavy elements are highly refractory materials that can withstand high disk temperatures? Among the exoplanets that can give us guidance here is DS Tuc Ab, discovered in 2019 in data from the TESS mission (Transiting Exoplanet Survey Satellite). Here we have a young world whose host is conveniently part of the 45 million year old Tucana-Horologium moving group (allowing us to establish its age), a planet within a binary system in the constellation Tucana. The binary stars are a G-class and K-class star, with DS Tuc Ab orbiting the...

Keith Cooper is a familiar face on Centauri Dreams, both through his own essays and the dialogues he and I have engaged in on interstellar topics. Keith is the editor of Astronomy Now and the author of both The Contact Paradox: Challenging Assumptions in the Search for Extraterrestrial Intelligence (Bloomsbury Sigma), and Origins of the Universe: The Cosmic Microwave Background and the Search for Quantum Gravity (Icon Books) to be published later this year. The Contact Paradox is a richly detailed examination of the history and core concepts of SETI, inspiring a new set of conversations, of which this is the first. With the recent expansion of the search through Breakthrough Listen, where does SETI stand both in terms of its likelihood of success and its perception among the general public? Paul Gilster Keith, we're 60 years into SETI and no contact yet, though there are a few tantalizing things like the WOW! signal to hold our attention. Given that you have just given us an...

Mention red dwarf habitable zones and tidal lock invariably comes up. If a planet is close enough to a dim red star to maintain temperatures suitable for life, wouldn't it keep one face turned toward it in perpetuity? But tidal lock, as Ashley Baldwin explains in the essay below, is more complex than we sometimes realize. And while there are ways to produce temperate climate models for such planets, tidal lock itself is a factor in not just M-dwarfs, but K- and even G-class stars like the Sun. Flip a few starting conditions and Earth itself might have been in tidal lock. The indefatigable Dr. Baldwin keeps a close eye on the latest exoplanet research, somehow balancing his astronomical scholarship with a career as consultant psychiatrist at the 5 Boroughs Partnership NHS Trust (Warrington, UK). Read on to learn a great deal about where current thinking stands on a subject critical to the question of red dwarf habitability. by Ashley Baldwin "Tidal locking", "captured rotation" or...

Our Sun is a G2V type star, or to use less formidable parlance, a yellow dwarf. It was inevitable that as we began considering planets around other stars (well before the first of these were discovered), we would imagine solar-class stars as the best place to look for life, but attention has swung to other possibilities in recent years, especially toward red dwarfs, which comprise a high percentage of all the stars in the galaxy. Now it seems that the problems of M-dwarfs are causing a reconsideration of the class in between, the K-class orange dwarfs. Alpha Centauri B is such a star, although its proximity to Centauri A may raise problems in planet formation that we have yet to observe. Fortunately, our long-distance exploration of the Centauri stars is well underway, and we should have new information about what orbits the two primary stars here within a few short years. If we were to find a habitable zone rocky world around Centauri B, one thing that makes it interesting is the...

Remembering how I felt 50 years ago when Apollo 11 launched, I fully understand those whose sense of let-down at the abrupt end of the moon landings has never gone away. And yes, I was one of those who assumed we would be on Mars by 1990 or earlier, with missions to the Jovian moons gearing up about now. Events in the interim have proven these expectations unrealistic, but last night as I was reminiscing I also thought about what we had done in those 50 years. 50 years ago, for example, the idea of Europa as an ocean world was still a few years out, only entering into serious speculation after Voyager 1 showed us what Jupiter’s immense tidal forces, aided by the gravitational effects of Europa and Ganymede, could do to Io. That flyby was in March of 1979, and if Io’s volcanoes told a tale, they also implicated Europa’s abundant ice. The Galileo mission, despite its problems, then showed us a Europan surface wracked by movement, with ‘chaos’ features, raft-like ice blocks evidently...

Centauri Dreams' resident film critic Larry Klaes continues his in-depth look at science fiction movies with 1972's Silent Running, whose protagonist is faced with a stark choice far from home. The film rode the era's surging interest in environmentalism, and while overshadowed in the memory of many of us by 1968's 2001: A Space Odyssey (and what SF film isn't?), it has interesting connections with that film. Douglas Trumbull, who handled special effects for 2001, was the force behind Silent Running, and concepts originally envisioned for the former turned up in the latter, especially in the depiction of Saturn. How Saturn might have played into the earlier film -- and why Jupiter took its place there -- is just one of the historical avenues Larry explores in this wide-ranging essay. By Larry Klaes "On this first day of a new century, we humbly beg forgiveness and dedicate these last forests of our once beautiful nation to the hope that they will one day return and grace our foul...

The advantages of neutral particle beam propulsion seem clear: Whereas a laser's photon beams can exchange momentum with the sail, neutral particle beams transfer energy and are considerably more efficient. In fact, as we saw in the first part of this essay, that efficiency can approach 100 percent. A mission concept emerges, one that reaches a nearby star in a matter of decades. But what about the particle beam generators themselves, and the hard engineering issues that demand solution? For that matter, how does the concept compare with Breakthrough Starshot? Read on as James Benford, working in collaboration with Alan Mole, describes the salient issues involved in building an interstellar infrastructure. By James Benford and Alan Mole We discuss the concept for a 1 kg probe that can be sent to a nearby star in about seventy years using neutral beam propulsion and a magnetic sail. We describe key elements of neutral particle beam generators, their engineering issues, cost structure...

The right kind of atmosphere may keep a planet habitable even if it crowds the inner region of the habitable zone. But atmospheric evolution involves many things, including the kind of geological activity our own planet has experienced, leading to sudden, deep extinctions. Centauri Dreams regular Alex Tolley today takes a look at a new paper that examines the terrestrial extinction of marine species in the Permian event some 252 million years ago. As we examine exoplanet habitability, it will be good to keep the factors driving such extinctions in mind. Tolley is a lecturer in biology at the University of California and author, with Brian McConnell, of A Design for a Reusable Water-Based Spacecraft Known as the Spacecoach (Springer, 2016). A key question in his essay today: Is our definition of the habitable zone simply too broad? by Alex Tolley In the search for life on exoplanets, questions about whether the planet is within the HZ given a plausible atmosphere is based on...

Usually when we talk about outer planet moons with oceans, we're looking at Jupiter's Europa, and Saturn's Enceladus. But evidence continues to mount for oceans elsewhere. In the Jupiter system alone, Callisto and Ganymede are likewise strong candidates, while Saturn's Titan probably has a layer of liquid water. Pluto's moon Charon may possess an ocean of water and ammonia, to judge from what appears to be cryovolcanic activity there. At Neptune, Triton's high-inclination orbit should produce plenty of tidal heating that may support a subsurface ocean. Let's pause, though, on another of Saturn's moons, Dione. Here we have evidence from Cassini that this world, some 1120 kilometers in diameter and composed largely of water ice, has a dense core with an internal liquid water ocean, joining Enceladus in that interesting system. But what engages us this morning is not liquid water but a set of straight, bright stripes discovered on the surface and discussed in a new paper from Alex...

The Sagittarius Dwarf Galaxy is a satellite of the Milky Way, about 70,000 light years from Earth and in a trajectory that has it currently passing over the Milky Way's galactic poles; i.e., perpendicular to the galactic plane. What's intriguing about this satellite is that its path takes it through the plane of our galaxy multiple times in the past, a passage whose effects may still be traceable today. A team of scientists led by Teresa Antoja (Universitat de Barcelona) is now using Gaia data to trace evidence of its effects between 300 and 900 million years ago. Image: The Sagittarius dwarf galaxy, a small satellite of the Milky Way that is leaving a stream of stars behind as an effect of our Galaxy's gravitational tug, is visible as an elongated feature below the Galactic centre and pointing in the downwards direction in the all-sky map of the density of stars observed by ESA's Gaia mission between July 2014 to May 2016. Credit: ESA/Gaia/DPAC. This story gets my attention because...

When I was a boy, I used to scan shortwave frequencies with an old Lafayette receiver in search of distant stations. When I learned that Jupiter was a radio source, my passion for radio DXing took a new turn, merging with my interest in astronomy. When I tried to log the planet's violent outbursts, I learned with a little digging in the library that Jupiter could be detected from about 15 MHz up to 40 MHz, with the best window somewhere between 18 MHz and 28 MHz. Called 'decametric noise storms,' the Jovian bursts sometimes sounded like ocean waves hitting a shore, but there were also short bursts that could be confused with local lightning, and to this day I'm not really sure whether I really heard Jupiter or not. When you're listening for something that sounds like the ocean in the shortwave bands, it's all too easy to think you're hearing it in the background noise, and a little imagination makes you think you've found your target. These days we can listen to just about anything...

Kelvin Long is a familiar face on Centauri Dreams, the author of several previous articles here and many publications in the field of interstellar studies. The creator of Project Icarus, the re-design of the Project Daedalus starship of the 1970s, Long was a co-founder of Icarus Interstellar and went on to head the Initiative for Interstellar Studies. He also served as editor of the Journal of the British Interplanetary Society during a critical period in the journal’s history, and authored Deep Space Propulsion: A Roadmap to Interstellar Flight (Springer, 2011). Today he turns his thoughts to catastrophe, and the question of what would happen to human civilization if it were reduced to a small remnant. Could we preserve the most significant treasures of our science, our culture, in the face of a devastated Earth? Exploring these ideas takes us deep into the past before turning toward what Kelvin sees as a possible solution. by Kelvin F Long The year is 2050. Earth is a thriving...

Can Andy Weir's Artemis, the setting for his new novel of the same name, be best described as a city or a town? Or is it better to think of it, as Ioannis Kokkinidis does in the essay that follows, as a 'polis'? The ancient Greek term carries through the centuries to inform Ioannis' musings on Weir's creation, as he examines Artemis, a tourist destination like no other, from a deeply international perspective. Well known for his attempt to keep the science of The Martian accurate, Weir set a high bar, one to which Artemis will invariably be compared. Ioannis Kokkinidis is a resident of Fresno, CA with an abiding interest in deep space. He holds a Master of Science in Agricultural Engineering from the Department of Natural Resources Management and Agricultural Engineering of the Agricultural University of Athens. He went on to obtain a Mastère Spécialisé Systèmes d’informations localisées pour l’aménagement des territoires (SILAT) from AgroParisTech and AgroMontpellier and a PhD in...

Fifty years ago today, 2001: A Space Odyssey was all the buzz, and I was preparing to see it within days on a spectacular screen at the Loew's State Theater in St. Louis. The memory of that first viewing will always be bright, but now we have seasoned perspective from Centauri Dreams regular Al Jackson, working with Bob Mahoney and Jon Rogers, to put the film in perspective. The author of numerous scientific papers, Al's service to the space program included his time on the Lunar Module Simulator for Apollo, described below, and his many years at Johnson Space Center, mostly for Lockheed working the Shuttle and ISS programs. But let me get to Al's foreword -- I'll introduce Bob Mahoney and Jon Rogers within the text in the caption to their photos. Interest in 2001 is as robust as ever -- be aware that a new 513-page book about the film is about to be published. It's Michael Benson's Space Odyssey: Stanley Kubrick, Arthur C. Clarke, and the Making of a Masterpiece. Let's now return to...

The Tau Zero Foundation and Centauri Dreams congratulates team Space Exploration Technologies, for the successful, historic, pioneering test flight of the Falcon Heavy. Ad Astra Incrementis indeed! From all of us, Jeff Greason Marc Millis Rhonda Stevenson Andrew Aldrin Paul Gilster Bill Tauskey Rod Pyle

Once in space in 2018, the Transiting Exoplanet Survey Satellite (TESS) will be observing, among many other things, hundreds of thousands of red giant stars across the entire sky. Planets around red giants are an interesting topic, because such stars point to an evolutionary outcome our own Sun will share, and we'd like to know more about what happens to existing planets in such systems as the host star swells and reddens, engulfing inner worlds. New work out of the University of Hawaii Institute for Astronomy now examines two 'hot Jupiters' around red giants, stellar systems where we see the gas giants swelling up as the result of processes that remain controversial. The inflated size of planets like these can be explained in at least two ways, one of which involves a slowing of the cooling in the planet's atmosphere, which causes the planet to inflate soon after formation. But the data presented here, drawn from NASA's K2 mission, tend to corroborate the thinking of co-author Eric...