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Talking to the Lion

by Paul Gilster | Oct 29, 2021 | Astrobiology and SETI | 56 Comments

Extraterrestrial civilizations, if they exist, would pose a unique challenge in comprehension. With nothing in common other than what we know of physics and mathematics, we might conceivably exchange information. But could we communicate our cultural values and principles to them, or hope to understand theirs? It was Ludwig Wittgenstein who said "If a lion could speak, we couldn't understand him." True? One perspective on this is to look not into space but into time. Traditional SETI is a search through space and only indirectly, through speed of light factors, a search through time. But new forms of SETI that look for technosignatures -- and this includes searching our own Solar System for signs of technology like an ancient probe, as Jim Benford has championed -- open up the chronological perspective in a grand way. Now we are looking for conceivably ancient signs of a civilization that may have perished long before our Sun first shone. A Dyson shell, gathering most of the light...

BLC1: The ‘Proxima Signal’ and What We Learned

by Paul Gilster | Oct 27, 2021 | Astrobiology and SETI | 19 Comments

If we were to find a civilization at Proxima Centauri, the nearest star, it would either be a coincidence of staggering proportions -- two technological cultures just happening to thrive around neighboring stars -- or an indication that intelligent life is all but ubiquitous in the galaxy. ‘Ubiquitous’ could itself mean different things: Many civilizations, scattered in their myriads amongst the stars, or a single, ancient civilization that had spread widely through the galaxy. If a coincidence, add in the time factor and things get stranger still. For only the tiniest fraction of our planet’s existence has been impinged upon by a tool-making species, and who knows what the lifetime of a civilization is? Unless civilizations can live for eons, how could two of them be found around stars so close? Thus the possibility that BLC1 -- Breakthrough Listen Candidate 1 -- was a valid technosignature at Proxima Centauri was greeted with a huge degree of skepticism within the SETI community...

Planetary Protection in an Interstellar Mode

by Paul Gilster | Oct 26, 2021 | Culture and Society | 11 Comments

Back in 2013, Heath Rezabek began developing a series in these pages on a proposal he called Vessel, which he had first presented at the 100 Year Starship Symposium in September of 2012. A librarian and futurist, Rezabek saw the concept as a strategy to preserve both humanity's cultural as well as biological heritage, with strong echoes of Greg Benford's Library of Life, which proposed freezing species in threatened environments to save them. In Heath's case, a productive partnership with frequent Centauri Dreams contributor Nick Nielsen led to articles by both, which produced a series of interesting discussions in the comments. I noticed in Philip Lubin's new paper, discussed here on Friday, an explicit reference to the idea of interstellar craft as possible backup devices for living systems. Lubin singled out the Svalbard Global Seed Vault (styled by some the 'Doomsday Vault'), which preserves seed samples numbering in the millions, with the aim of keeping them safe for centuries....

Starlight: Toward an Interstellar Biology

by Paul Gilster | Oct 22, 2021 | Astrobiology and SETI | 32 Comments

If you could send out a fleet of small lightsails, accelerated to perhaps 20 percent of the speed of light, you could put something of human manufacture into the Alpha Centauri triple star system within about 20 years. So goes, of course, the thinking of Breakthrough Starshot, which continues to investigate whether such a proposal is practicable. As the feasibility study continues, we'll learn whether the scientists involved have been able to resolve some of the key issues, including especially data return and the need for power onboard to make it happen. The concept of beam-driven sails for acceleration to interstellar speeds goes back to Robert Forward (see Jim Benford's excellent A Photon Beam Propulsion Timeline in these pages) and has been examined for several decades by, among others, Geoffrey Landis, Gregory Matloff, Benford himself (working with brother Greg) in laboratory experiments at JPL, Leik Myrabo, and Chaouki Abdallah and team at the University of New Mexico. At the...

Thoughts on Water Vapor on Europa

by Paul Gilster | Oct 20, 2021 | Outer Solar System | 10 Comments

Juno has worked wonders for our knowledge of Jupiter, but we continue to rely on Hubble observations and still helpful imagery from Galileo as we study the giant planet's intriguing moon Europa, anticipating the arrival of Europa Clipper and the European Space Agency's Jupiter Icy Moons Explorer (JUICE) at the end of the decade. The great question is whether life can exist beneath the ice, and the evidence of plume activity, first found in 2013 in Hubble data, is encouraging in some ways more than others. A mission to Saturn's moon Enceladus can rely on geysers in a particular place -- the Tiger Stripes at the south pole -- and on geysers that are frequent. At Europa, predicting where and when a plume will burst forth is all but a black art. How do we sample a Europan plume? Image: Will we one day see Europa through the eyes of a (well-shielded) lander? Credit: NASA. While contemplating that question, we push ahead with other analyses that help us characterize this unusual place. A...

Planetary Composition: Enter the ‘Super-Mercuries’

by Paul Gilster | Oct 18, 2021 | Exoplanetary Science | 4 Comments

The idea that the composition of a star and its rocky planets are connected is a natural one. Both classes of object accrete material within a surrounding gas and dust environment, and thus we would expect a link between the two. Testing the hypothesis, researchers from three institutions -- the Instituto de Astrofísica e Ciências do Espaço (Portugal), the NCCR PlanetS project at the University of Bern, and the University of Zürich -- have confirmed the concept while fine-tuning the details. After all, we still have to explain iron-rich Mercury as an outlier in our own Solar System. Image: Mercury has an average density of 5430 kilograms per cubic meter, which is second only to Earth among all the planets. It is estimated that the planet Mercury, like Earth, has a ferrous core with a size equivalent to two-thirds to three-fourths that of the planet's overall radius. The core is believed to be composed of an iron-nickel alloy covered by a mantle and surface crust. Credit: NASA....

A Jupiter-class Planet Orbiting a White Dwarf

by Paul Gilster | Oct 15, 2021 | Exoplanetary Science | 6 Comments

A gas giant similar to Jupiter, and with a somewhat similar orbit, revolves around a white dwarf located about 6500 light years out toward galactic center. As reported in a paper in Nature, this is an interesting finding because stars like the Sun eventually wind up as white dwarfs, so we have to wonder what kind of planets could survive a star’s red giant phase and continue to orbit the primary. If Earth one day is engulfed, will the gas giants survive? The new discovery implies that result, and marks the first confirmed planetary system that looks like what ours could become. Image: An artist’s rendition of a newly discovered Jupiter-like exoplanet orbiting a white dwarf. This system is evidence that planets can survive their host star’s explosive red giant phase, and is the first confirmed planetary system that serves as an analogue to the face of the Sun and Jupiter in our own Solar System. Credit: W. M. Keck Observatory/Adam Makarenko. Underlining just how faint white dwarfs are...

Interesting Transient: A New Class of Object toward Galactic Center?

by Paul Gilster | Oct 14, 2021 | Deep Sky Astronomy & Telescopes | 14 Comments

The 36 dish antennae at ASKAP -- the Australian Square Kilometre Array Pathfinder in outback Western Australia -- comprise an interferometer with a total collecting area of about 4,000 square meters. ASKAP has commanded attention as a technology demonstrator for the planned Square Kilometer Array, but today we're looking at the discovery of a highly polarized, highly variable radio source labeled ASKAP J173608.2?321635, about 4 degrees from galactic center in the galactic plane. According to Ziteng Wang, who is lead author of the study on this signal and a University of Sydney PhD student, the observations are strikingly different from other variable radio sources: "The strangest property of this new signal is that it has a very high polarisation. This means its light oscillates in only one direction, but that direction rotates with time. The brightness of the object also varies dramatically, by a factor of 100, and the signal switches on and off apparently at random. We've never...

Enlarging Perspectives on Space (and Time)

by Paul Gilster | Oct 13, 2021 | Culture and Society | 12 Comments

What do we mean by an 'interstellar mission'? The question came up in relation to Interstellar Probe, that 'Voyager Plus' concept being investigated by the Johns Hopkins Applied Physics Laboratory. I do indeed see it as an interstellar mission, as Interstellar Probe takes us outside the heliosphere and into the local interstellar medium. We need to understand conditions there because it would be folly to mount a mission to another star without knowing the dynamics of the heliosphere's movement through the interstellar cloud we are currently in, or the ramifications of moving between it and the adjacent cloud as we make our crossing. How could it be otherwise? Journeys need maps and knowledge of conditions along the way. Thus we push into the fringes of interstellar space, and gradually extend our reach. As we do this, we inevitably produce changes in the way we perceive our place in the cosmos. Cultural expectations about space have been shaped by what I might call a 'planar'...

Interstellar Reach: Exploration as Choice

by Paul Gilster | Oct 11, 2021 | Culture and Society | 11 Comments

Two missions with interstellar implications have occupied us in recent days. The first, Interstellar Probe, has significance in being the first dedicated mission into the local interstellar medium. Here the science return would be immense, as we would have the opportunity to view the heliosphere from the outside. Culturally, Interstellar Probe is the kind of mission that can force resets in how we view exploration, a thought I want to expand on in the next post. The other mission -- multiple mission options, actually -- involves interstellar objects like the odd 1I/'Oumuamua and 2I/Borisov, the latter clearly a comet, the former still hard to categorize. In fact, between the two, what I think we can just call Comet Borisov seems almost pedestrian, with a composition so like comets in our own system as to suggest such objects are commonplace among the stars. Whereas to explain 'Oumuamua as a comet, we have to stretch our definitions into bizarre objects of pure hydrogen (a theory that...

Reaching an Interstellar Interloper

by Paul Gilster | Oct 8, 2021 | Missions | 51 Comments

The ongoing Interstellar Probe study at the Johns Hopkins University Applied Physics Laboratory reminds us of the great contribution of the Voyager spacecraft, but also of the need to develop their successors. Interstellar flight is a dazzling goal considered in the long term, but present technologies develop incrementally and missions to other stars are a multi-generational goal. But as we continue that essential effort with projects like Interstellar Probe, we can also make plans to explore objects from other stellar systems (ISOs) closer to home. I refer of course to the appearance in the last three years of two such objects, 1I/’Oumuamua and 2I/Borisov, the ‘I’ in their names referencing the exciting fact that these are interstellar in nature, passing briefly through our system before moving on. Papers have begun to appear to examine missions to one or the other of these objects, or to plan how, with sufficiently early discovery, we could get a spacecraft to the next one. And...

Assessing the Oberth Maneuver for Interstellar Probe

by Paul Gilster | Oct 6, 2021 | Missions | 26 Comments

I notice that the question of 'when to launch' has surfaced in comments to my first piece on Interstellar Probe, the APL study to design a spacecraft that would be, in effect, the successor to Voyager. It's a natural question, because if a craft takes 50 years to reach 1000 AU, there will likely be faster spacecraft designed later that will pass it in flight. I'm going to come down on the side of launching as soon as possible rather than anticipating future developments. Two reasons: The research effort involved in stretching what we can do today to reach as high a velocity as possible inevitably moves the ball forward. We learn as we go, and ideas arise in the effort that can hasten the day of faster spacecraft. The second reason is that a vehicle like Interstellar Probe is hardly passive. It does science all along its route. By the time it reaches 1000 AU, it has returned massive amounts of information about the interstellar medium, our Sun's passage through it, and the heliosphere...

Interstellar Probe: Pushing Beyond Voyager

by Paul Gilster | Oct 5, 2021 | Missions | 31 Comments

Our doughty Voyager 1 and 2, their operations enabled by radioisotope power systems that convert heat produced by the decay of plutonium-238 into electricity, have been pushing outward through and beyond the Solar System since 1977. Designed for a four and a half year mission, we now have, more or less by accident and good fortune, our first active probes of nearby interstellar space. But not for long. At some point before the end of this decade, both craft will lack the power to keep any of their scientific instruments functioning, and one great chapter in exploration will close. What will the successor to the Voyagers look like? The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has been working on a probe of the local interstellar medium. We're talking about a robotic venture that would be humanity's first dedicated mission to push into regions that future, longer-range interstellar craft will have to cross as they move far beyond the Sun. If it flies, Interstellar...

The Survival of M-Dwarf Planet Atmospheres

by Paul Gilster | Oct 1, 2021 | Exoplanetary Science | 16 Comments

I was interested in yesterday's story about the two super-Earths around nearby M-dwarfs -- TOI-1634b and TOI-1685b -- partly because of the research that follows. In both cases there is the question of atmospheres. The two TESS planets are so numbingly close to their host stars that they may have lost their original hydrogen/helium atmospheres in favor of an atmosphere sustained by emissions from within. Hearteningly, we should be able to find out more with the James Webb Space Telescope, on which ride the hopes of so many exoplanet researchers. Today's system is the intriguing L 98-59, only 35 light years from Earth and possessed of at least four planets, with a fifth as yet unconfirmed. Here we have two rocky inner worlds, a possible ocean planet (L 98-59 d) and another likely rocky world to the inside of the habitable zone boundary. Perhaps within the habitable zone, if it exists, is L 98-59f, so this is a system to keep an eye on, an obvious candidate as a JWST target. At UC...

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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