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Methane as Biosignature: A Conceptual Framework

by Paul Gilster | Mar 31, 2022 | Exoplanetary Science | 13 Comments

A living world around another star will not be an easy catch, no matter how sophisticated the coming generation of space- and ground-based telescopes turns out to be. It’s one thing to develop the tools to begin probing an exoplanet atmosphere, but quite another to be able to say with any degree of confidence that the result we see is the result of biology. When we do begin picking up an interesting gas like methane, we’ll need to evaluate the finding against other atmospheric constituents, and the arguments will fly about non-biological sources for what might be a biosignature. This is going to begin playing out as the James Webb Space Telescope turns its eye on exoplanets, and methane is the one potential sign of life that should be within its range. We know that oxygen, ozone, methane and carbon dioxide are produced through biological activity on Earth, and we also know that each can be produced in the absence of life. The simultaneous presence of such gases is what would intrigue...

SETI as Exploration

by Paul Gilster | Mar 29, 2022 | Culture and Society | 30 Comments

Early exoplanet detections always startled my friends outside the astronomical community. Anxious for a planet something like the Earth, they found themselves looking at a 'hot Jupiter' like 51 Pegasi b, which at the time seemed like little more than a weird curiosity. A Jupiter-like planet hugging a star? More hot Jupiters followed, which led to the need to explain how exoplanet detection worked with radial velocity methods, and why big planets close to their star should turn up early in the hunt. Earlier, there were the pulsar planets, as found by Aleksander Wolszczan and Dale Frail around the pulsar PSR B1 257+12 in the constellation Virgo. These were interestingly small, but obviously accumulating a sleet of radiation from their primary. Detected a year later, PSR B1620-26 b was found to orbit a white dwarf/pulsar binary system. But these odd detections some 30 years ago actually made the case for the age of exoplanet discovery that was about to open, a truly golden era of deep...

A Hybrid Interstellar Mission Using Antimatter

by Paul Gilster | Mar 25, 2022 | Missions | 34 Comments

Epsilon Eridani has always intrigued me because in astronomical terms, it's not all that far from the Sun. I can remember as a kid noting which stars were closest to us - the Centauri trio, Tau Ceti and Barnard's Star - wondering which of these would be the first to be visited by a probe from Earth. Later, I thought we would have quick confirmation of planets around Epsilon Eridani, since it's a scant (!) 10.5 light years out, but despite decades of radial velocity data, astronomers have only found one gas giant, and even that confirmation was slowed by noise-filled datasets. Even so, Epsilon Eridani b is confirmed. Also known as Ægir (named for a figure in Old Norse mythology), it's in a 3.5 AU orbit, circling the star every 7.4 years, with a mass somewhere between 0.6 and 1.5 times that of Jupiter. But there is more: We also get two asteroid belts in this system, as Gerald Jackson points out in his new paper on using antimatter for deceleration into nearby star systems, as well as...

Antimatter-driven Deceleration at Proxima Centauri

by Paul Gilster | Mar 22, 2022 | Antimatter | 27 Comments

Although I've often seen Arthur Conan Doyle's Sherlock Holmes cited in various ways, I hadn't chased down the source of this famous quote: "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth." Gerald Jackson's new paper identifies the story as Doyle's "The Adventure of the Blanched Soldier," which somehow escaped my attention when I read through the Sherlock Holmes corpus a couple of years back. I'm a great admirer of Doyle and love both Holmes and much of his other work, so it's good to get this citation straight. As I recall, Spock quotes Holmes to this effect in one of the Star Trek movies; this site's resident movie buffs will know which one, but I've forgotten. In any case, a Star Trek reference comes into useful play here because what Jackson (Hbar Technologies, LLC) is writing about is antimatter, a futuristic thing indeed, but also in Jackson's thinking a real candidate for a propulsion system that involves using...

An Abundance of Technosignatures?

by Paul Gilster | Mar 18, 2022 | Astrobiology and SETI | 73 Comments

What expectations do we bring to the hunt for life elsewhere in the universe? Opinions vary depending on who has the podium, but we can neatly divide the effort into two camps. The first looks for biosignatures, spurred by our remarkably growing and provocative catalog of exoplanets. The other explicitly looks for signs of technology, as exemplified by SETI, which from the start hunted for signals produced by intelligence. My guess is that a broad survey of those looking for biosignatures would find that they are excited by the emerging tools available to them, such as new generations of ground- and space-based telescopes, and the kind of modeling we saw in the last post applied to a hypothetical Alpha Centauri planet. We use our growing datasets to examine the nature of exoplanets and move beyond observation to model benchmarks for habitable worlds, including their atmospheric chemistry and even geology. Technosignatures are a different matter, and it's fascinating to read through a...

A New Title on Extraterrestrial Intelligence

by Paul Gilster | Mar 17, 2022 | Culture and Society | 4 Comments

Just a quick note for today as I finish up tomorrow's long post. But I did want you to be aware of this new title, Extraterrestrial Intelligence: Academic and Societal Implications, which has connections with recent topics and will again tomorrow, when we discuss a new paper from Jason Wright and SETI colleagues on technosignatures. As with the recent biography of John von Neumann, I haven't had the chance to read this yet, but it's certainly going on the list. The book is out of Cambridge Scholars Publishing. Here's the publisher's description: What are the implications for human society, and for our institutions of higher learning, of the discovery of a sophisticated extraterrestrial intelligence (ETI) operating on and around Earth? This book explores this timely question from a multidisciplinary perspective. It considers scientific, philosophical, theological, and interdisciplinary ways of thinking about the question, and it represents all viewpoints on how likely it is that an...

Modeling a Habitable Planet at Centauri A/B

by Paul Gilster | Mar 15, 2022 | Exoplanetary Science | 25 Comments

Why is it so difficult to detect planets around Alpha Centauri? Proxima Centauri is one thing; we’ve found interesting worlds there, though this small, dim star has been a tough target, examined through decades of steadily improving equipment. But Centauri A and B, the G-class and K-class central binary here, have proven impenetrable. Given that we’ve found over 4500 planets around other stars, why the problem here? Proximity turns out to be a challenge in itself. Centauri A and B are in an orbit around a common barycenter, angled such that the light from one will contaminate the search around the other. It’s a 79-year orbit, with the distance between A and B varying from 35.6 AU to 11.2. You can think of them as, at their furthest, separated by the Sun’s distance from Pluto (roughly), and at their closest, by about the distance to Saturn. The good news is that we have a window from 2022 to 2035 in which, even as our observing tools continue to improve, the parameters of that orbit...

Why Fill a Galaxy with Self-Reproducing Probes?

by Paul Gilster | Mar 10, 2022 | Culture and Society | 48 Comments

We can’t know whether there is a probe from another civilization – a von Neumann probe of the sort we discussed in the previous post – in our own Solar System unless we look for it. Even then, though, we have no guarantee that such a probe can be found. The Solar System is a vast place, and even if we home in on the more obvious targets, such as the Moon, and near-Earth objects in stable orbits, a well hidden artifact a billion or so years old, likely designed not to draw attention to itself, is a tricky catch. As with any discussion of extraterrestrial civilizations, we’re left to ponder the possibilities and the likelihoods, acknowledging how little we know about whether life itself is widely found. One question opens up another. Abiogenesis may be spectacularly rare, or it may be commonplace. What we eventually find in the ice moons of the outer system should offer us some clues, but widespread life doesn’t itself translate into intelligent, tool-making life. But for today, let’s...

Probing von Neumann Expansion

by Paul Gilster | Mar 8, 2022 | Astrobiology and SETI | 22 Comments

Before getting into the paper I want to discuss today, I want to mention the new biography of John von Neumann by Ananyo Bhattacharya. I make no comment on The Man from the Future (W. W. Norton & Company, 2022) yet because while I have a copy, I haven't had time to read it. But be aware that it’s out there – it’s getting good reviews, and given the impact of this remarkable figure on everything from programmable computers to game theory and the interstellar dispersion of civilizations, it’s a book you’ll at least want to stick on your reference list. I figure anyone who masters calculus by the age of eight, as von Neumann is reputed to have done, is going to turn out to make a substantial contribution somewhere. I’m also interested in how polymaths function, moving with what seems effortless ease through diverse fields of study and somehow leaving their mark on each. What a contrast to our age of micro-specialization, where relentless drilling down into a single topic – and this...

HOEE: The Starshade and the Ground

by Paul Gilster | Mar 4, 2022 | Exoplanetary Science | 20 Comments

I always keep an eye on the Phase I and Phase II studies in the pipeline at the NASA Innovative Advanced Concepts (NIAC) program. The goal is to support ideas in their early stages, with the 2022 awards going out to 17 different researchers to the tune of a combined $5.1 million. Of these, 12 are Phase I studies, which deliver $175,000 for a nine-month period, while the five Phase II awards go to $600,000 over two years. We looked at one of the Phase I studies, Jason Benkoski's solar-thermal engine and shield concept, in the last post. Today we go hunting exoplanets with a starshade. This particular iteration of the starshade concept is called Hybrid Observatory for Earth-like Exoplanets (HOEE), as proposed by John Mather (NASA GSFC). Here the idea is to leverage the resources of the huge ground-based telescopes that should define the next generation of such instruments - the Giant Magellan Telescope, the Extremely Large Telescope, etc. - by using a starshade to block the glare of...

Engineering the Oberth Maneuver

by Paul Gilster | Mar 3, 2022 | Missions | 23 Comments

As we saw recently with the analogy of salt grains for stars, the scale of things cosmic stuns the imagination. But we don't have to go to galactic scale. We can stay much closer to home and achieve the same effect. Because at our current technological levels, getting even as far as the outer planets taxes our capabilities. The least explored types of planet in our Solar System are the dwarf worlds, places like Ceres, Pluto and Charon, not to mention the enigmatic Triton. It takes years to reach them. Beyond these objects we have a wide range of other dwarfs that merit study, at distances that push us ever farther. In a description of their NIAC Phase I study, just announced as a selection for 2022, Jason Benkoski and colleagues at Johns Hopkins University look into a combination heat shield and solar propulsion system that would perform a close Solar pass and use the Sun's gravity to slingshot outwards at the highest possible velocity. It's a maneuver familiar to Centauri Dreams...

Lowering the Laser Barrier

by Paul Gilster | Mar 1, 2022 | Sail Concepts | 5 Comments

The continuing release of papers related to or referring to the Breakthrough Starshot sail concept is good news for the entire field. Interstellar studies as an academic discipline has never had this long or sustained a period of activity, and the growing number of speakers at space-related conferences attests to the current vitality of starflight among professionals and the general public alike. Not all interstellar propulsion concepts involve laser-beaming, of course, and we’ll soon look at what some would consider an ever more exotic concept. But today I’m focusing on a paper from Ho-Ting Tung and Artur Davoyan, both in the Mechanical and Aerospace Engineering Department at UCLA. You could say that these two researchers are filling in some much needed space between the full-bore interstellar effort of Breakthrough Starshot, the Solar System-oriented laser work of Andrew Higgins’ team at McGill, and much smaller, near-term experiments we could run not so far from now. Of the many...

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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