Paul Gilster | Centauri Dreams

How a Super-Earth Would Change the Solar System

by Paul Gilster | Mar 8, 2023 | Exoplanetary Science | 22 Comments

If there is a Planet Nine out there, I assume we’ll find it soon. That would be a welcome development, in that it would imply the Solar System isn’t quite as odd as it sometimes seems to be. We see super-Earths – and current thinking seems to be that this is what Planet Nine must be – in other stellar systems, in great numbers in fact. So it would stand to reason that early in its evolution our system produced a super-Earth, one that was presumably nudged into a distant, eccentric orbit by gravitational interactions. The gap in size between Earth and the next planet up in scale is wide. Neptune is 17 times more massive than our planet, and four times its radius. Gas giant migration surely played a role in the outcome, and when considering stellar system architectures, it’s noteworthy as well that all that real estate between Mars and Jupiter seems to demand something more than asteroidal debris. To make sense of such issues, Stephen Kane (University of California, Riverside) has run...

DART’s Ejecta and Planetary Defense

by Paul Gilster | Mar 6, 2023 | Asteroid and Comet Deflection | 8 Comments

I’m glad to see the widespread coverage of the DART mission results, both in terms of demonstrating to the public what is possible in terms of asteroid threat mitigation, and also of calming overblown fears that we have too little knowledge of where these objects are located. DART (Double Asteroid Redirection Test) was a surprisingly demonstrative success, shortening the orbit of the satellite asteroid Dimorphos by an unexpectedly large value of 33 minutes. The recoil effect from the ejection of asteroid material, perhaps as high as 0.5% of its total mass, accounts for the result. Watching the ejecta evolve has been fascinating in its own right, as the interactions between the two elements of the binary asteroid come into play along with solar radiation pressure. Asteroids have previously been observed that displayed a sustained tail, as Dimorphos did after impact, and the DART results suggest that the hypothesis of similar impacts on these objects is correct. Thus we learn valuable...

Re-thinking the Early Universe?

by Paul Gilster | Feb 28, 2023 | Deep Sky Astronomy & Telescopes | 47 Comments

I hadn’t intended to return so quickly to the issue of high-redshift galaxies, but SPT0418-47 jibes nicely with last week's piece on 13.5 billion year old galaxies as studied by Penn State’s Joel Leja and colleagues. In that case, the issue was the apparent maturity of these objects at such an early age in the universe. Today’s work, reported in a paper in The Astrophysical Journal Letters, comes from a team led by Bo Peng at Cornell University. It too uses JWST data, in this case targeting a previously unseen galaxy the instrument picked out of the foreground light of galaxy SPT0418-47. In both cases, we’re seeing data that challenge conventional understanding of conditions in this remote era. This is evidence, but of what? Are we wrong about the basics of galaxy formation? Do we need to recalibrate the models we use to understand astrophysics at high-redshift? SPT0418-47 is the galaxy JWST was being used to study, an intriguing subject in its own right. This is an infant galaxy...

High Redshift Caution

by Paul Gilster | Feb 23, 2023 | Deep Sky Astronomy & Telescopes | 32 Comments

When something turns up in astronomical data that contradicts long accepted theory, the way forward is to proceed with caution, keep taking data and try to resolve the tension with older models. That would of course include considering the possibilities of error somewhere in the observations. All that is obvious enough, but a new paper on JWST data on high-redshift galaxies is striking in its implications. Researchers examining this primordial era have found six galaxies, from no more than 500 to 700 million years after the Big Bang, that give the appearance of being massive. We’re looking at light from objects 13.5 billion years old that should be anything but mature, if compact, galaxies. That’s a surprise, and it’s fascinating to see the scrutiny to which these findings have been exposed. The editors of Nature have helpfully made available a peer review file containing back and forth comments between the authors and reviewers that give a jeweler’s eye look at how intricate the...

How Common Are Planets Around Red Dwarf Stars?

by Paul Gilster | Feb 22, 2023 | Exoplanetary Science | 7 Comments

We’re beginning to learn how common planets are around stars of various types, but M-dwarfs get special attention given their role in future astrobiological studies. As I’ve just been talking about CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs program, I’ll fold in today’s news about their release of 20,000 observations covering more than 300 stars, for we can mine some data here about planet occurrence rates. 59 new planets turn up in the spectroscopic data gathered at the Calar Alto Observatory in Span, with about 12 thought to be in the habitable zone of their star. I’ll await with interest our friend Andrew LePage’s assessment. His habitable zone examinations serve as a highly useful reality check. I mentioned spectrographic data above. The CARMENES instruments are built for optical as well as near-infrared studies, and have been used to explore nearby red dwarfs and their possible planets since...

Uranus Orbiter and Probe: Implications for Icy Moons

by Paul Gilster | Feb 21, 2023 | Outer Solar System | 7 Comments

What do you get if you shake ice in a container with centimeter-wide stainless steel balls at temperature of –200 ?C? The answer is a kind of ice with implications for the outer Solar System. I just ran across an article in Science (citation below) that describes the resulting powder, a form of ‘amorphous ice,’ meaning ice that lacks the familiar crystalline arrangement of regular ice. There is no regularity here, no ordered structure. The two previously discovered types of amorphous ice – varying by their density – are uncommon on Earth but an apparently standard constituent of comets. The new medium-density amorphous ice may well be produced on outer system moons, created through the shearing process that the researchers, led by Alexander Rosu-Finsen at University College London, produced in their lab work. There is a good overview of this water ‘frozen in time’ in a recent issue of Nature. The article quotes Christoph Salzmann (UCL), a co-author on the Science paper: The team used...

Wolf 1069b: Why System Architecture Matters

by Paul Gilster | Feb 17, 2023 | Exoplanetary Science | 19 Comments

Let’s look at a second red dwarf planet in this small series on such, this one being Wolf 1069b. I want to mention it partly because of the prior post on K2-415b, where we had the good fortune to be dealing with a transiting world around an M-dwarf that should be useful in future atmospheric characterization efforts. Wolf 1069b, by contrast, was found by radial velocity methods, and I’m less interested in whether or not it’s in a ‘habitable’ orbit than in the system architecture here, which raises questions. This work, recounted in a recent paper in Astronomy & Astrophysics, describes a planet that is not just Earth-sized, as is K2-415b, but roughly equivalent to Earth in mass, making a future search for biosignatures interesting once we have the capability of collecting photons directly from the planet. If the planet has an atmosphere, argue the authors of the paper, its surface temperature could reach 13 degrees Celsius, certainly a comfortable temperature for liquid water. A...

The Relevance of K2-415b

by Paul Gilster | Feb 14, 2023 | Exoplanetary Science | 6 Comments

I want to mention the recent confirmation of K2-415b because this world falls into an interesting category: Planets with major implications for studying their atmospheres. Orbiting an M5V M-dwarf every 4.018 days at a distance of 0.027 AU, this is not a planet with any likelihood for life. Far from it, given an equilibrium temperature expected to be in the range of 400 K (the equivalent figure for Earth is 255 K). And although it’s roughly Earth-sized, K2-415b turns out to be at least three times more massive. What this planet has going for it, though, is that it transits a low mass star, and at 70 light years, it’s close. Consider: If we want to take advantage of transmission spectroscopy to study light being filtered through the planetary atmosphere during ingress and egress from the transit, nearby M-dwarf systems make ideal targets. Their habitable zones are close in, so we get frequent transits around small stars. But the number of Earth-sized transiting worlds around nearby...

A Mission Architecture for the Solar Gravity Lens

by Paul Gilster | Feb 8, 2023 | Missions | 28 Comments

Over the past several years we’ve looked at two missions that are being designed to go beyond the heliosphere, much farther than the two Voyagers that are our only operational spacecraft in what we can call the Local Interstellar Medium. Actually, we can be more precise. That part of the Local Interstellar Medium where the Voyagers operate is referred to as the Very Local Interstellar Medium, the region where the LISM is directly affected by the presence of the heliosphere. The Interstellar Probe design from Johns Hopkins Applied Physics Laboratory and the Jet Propulsion Laboratory’s Solar Gravity Lens (SGL) mission would pass through both regions as they conduct their science operations. Both probes have ultimate targets beyond the VLISM, with Interstellar Probe capable of looking back at the heliosphere as a whole and reaching distances are far as 1000 AU still operational and returning data to Earth. The SGL mission begins its primary science mission at the Sun’s gravitational...

Into the Maelström

by Paul Gilster | Feb 3, 2023 | Exotic Physics | 37 Comments

"'This,' said I at length, to the old man -- 'this can be nothing else than the great whirlpool of the Maelström'... The ordinary accounts of this vortex had by no means prepared me for what I saw. That of Jonas Ramus, which is perhaps the most circumstantial of any, cannot impart the faintest conception either of the magnificence, or of the horror of the scene -- or of the wild bewildering sense of the novel which confounds the beholder." So wrote Edgar Allen Poe in 1841 in a short story called "A Descent into The Maelström," reckoned by some to be an early instance of science fiction. In today's essay, Adam Crowl explores another kind of whirlpool, armed with the tools of mathematics to take the deepest plunge imaginable, into the maw of a supermassive black hole. Adam's always fascinating musings can be followed on his Crowlspace site. by Adam Crowl The European Southern Observatory’s (ESO) GRAVITY instrument is a beam combiner in the infra-red K-band that operates as a part of...

MaRMIE: The Martian Regolith Microbiome Inoculation Experiment

by Paul Gilster | Jan 31, 2023 | Astrobiology and SETI | 54 Comments

Alex Tolley follows up his analysis of agriculture on Mars with a closer look at the Interstellar Research Group’s MaRMIE project – the Martian Regolith Microbiome Inoculation Experiment. Growing out of discussions on methods beyond hydroponics to make the Red Planet fertile, the project is developing an experimental framework, as described below, to test our assumptions about Martian regolith here on Earth. A path forward through simulation and experiment could help us narrow the options for what may be possible for future colonists. Fertile regolith, achieved through perchlorate removal, would open up possibilities far beyond what is achievable through hydroponics. by Alex Tolley Successful settlement of distant locations requires living off the land, which requires resourcing food. Failure can lead to disaster, as experienced by some of the early American colonies. While near Earth space settlements could be supplied with packaged food, this would be too costly for an expanding...

Food production on Mars: Dirt farming as the most scalable solution for settlement

by Paul Gilster | Jan 26, 2023 | Culture and Society | 142 Comments

Colonies on other worlds are a staple of science fiction and an obsession for rocket-obsessed entrepreneurs, but how do humans go about the business of living long-term once they get to a place like Mars? Alex Tolley has been pondering the question as part of a project he has been engaged in with the Interstellar Research Group. Martian regolith is, shall we say, a challenge, and the issue of perchlorates is only one of the factors that will make food production a major part of the planning and operation of any colony. The essay below can be complemented by Alex’s look at experimental techniques we can use long before colonization to consider crop growth in non-terrestrial situations. It will appear shortly on the IRG website, all part of the organization’s work on what its contributors call MaRMIE, the Martian Regolith Microbiome Inoculation Experiment. by Alex Tolley Introduction: Food Production Beyond Hydroponics Conventional wisdom suggests that food production in the Martian...

An Appreciation of SETI’s Robert Gray (1948-2021)

by Paul Gilster | Jan 19, 2023 | Astrobiology and SETI | 37 Comments

Robert Gray was something of an outsider in the community of SETI scientists, spending most of his career in the world of big data, calculating mortgage lending patterns and examining issues in urban planning from his office in Chicago. As an independent consultant specializing in data analysis, his talents were widely deployed. But SETI was a passion more than a hobby for Gray, and he became highly regarded by scientists he worked with, many of whom were both surprised to hear of his death on December 6, 2021. It was Jim Benford who gave me the news just recently, and it humbles me to think that a Centauri Dreams post I worked with Gray to publish (How Far Can Civilization Go?) appeared just months before he died. Gray’s independent status accounts for the lack of publicity about his death in our community, but I’m still startled that I’m only now learning about it. His name certainly has resonance on this site, particularly his book The Elusive Wow: Searching for Extraterrestrial...

The Value of LHS 475b

by Paul Gilster | Jan 13, 2023 | Exoplanetary Science | 10 Comments

LHS 475b, a planet whose diameter is all but identical to Earth's, makes news not so much because of what it is but because of what it tells us about studying the atmospheres of small rocky worlds. Credit for the confirmation of this planet goes to the NIRSpec (Near-Infrared Spectrograph) instrument aboard the James Webb Space Telescope, and LHS 475b marks the telescope’s first exoplanet catch. Data from the Transiting Exoplanet Survey Satellite (TESS) were sufficient to point scientists toward this system for a closer look. JWST confirmed the planet after only two transits. Based on this detection, the Webb telescope is going to live up to expectations about its capabilities in exoplanet work. NIRSpec is a European Space Agency contribution to the JWST mission, and a major one, as the instrument’s multi-object spectroscopy mode is able to obtain spectra of up to 100 objects simultaneously, a capability that maximizes JWST observing time. No other spectrograph in space can do this,...

Sunvoyager’s Pedigree: On the Growth of Interstellar Ideas

by Paul Gilster | Jan 11, 2023 | Missions | 19 Comments

Kelvin Long’s new paper on the mission concept called Sunvoyager would deploy inertial confinement fusion, described in the last post, to drive a spacecraft to 1000 AU in less than four years. The number pulsates with possibilities: A craft like this would move at 325 AU per year, or roughly 1500 kilometers per second, ninety times the velocity of Voyager 1. This kind of capability, which Long thinks we may achieve late in this century, would open up all kinds of fast science missions to the outer planets, the Kuiper Belt, and even the inner Oort Cloud. And the conquest of inertial confinement methods would open the prospect for later, still faster missions to nearby stars. Sunvoyager draws on the heritage of the Daedalus starship, that daring design conceived by British Interplanetary Society members in the 1970s, but as we saw last time, inertial confinement fusion (ICF) was likewise examined in a concept called Vista, and one of the pleasures of this kind of research for a...

SunVoyager: A Fast Fusion Mission Beyond the Heliosphere

by Paul Gilster | Jan 6, 2023 | Missions | 39 Comments

1000 AU makes a fine target for our next push past the heliosphere, keeping in mind that good science is to be had all along the way. Thus if we took 100 years to get to 1000 AU (and at Voyager speeds it would be a lot longer than that), we would still be gathering solid data about the Kuiper Belt, the heliosphere itself and its interactions with the interstellar medium, the nature and disposition of interstellar dust, and the plasma environment any future interstellar craft will have to pass through. We don’t have to get there fast to produce useful results, in other words, but it sure would help. The Thousand Astronomical Unit mission (TAU) was examined by NASA in the 1980s using nuclear electric propulsion technologies, one specification being the need to reach the target distance within 50 years. It’s interesting to me – and Kelvin Long discusses this in a new paper we’ll examine in the next few posts – that a large part of the science case for TAU was stellar parallax, for...

Gathering the Evidence for Life on Enceladus

by Paul Gilster | Jan 4, 2023 | Outer Solar System | 13 Comments

With a proposal for an Enceladus Orbilander mission in the works at the Johns Hopkins Applied Physics Laboratory, I continue to mull over the prospects for investigating this interesting moon. Something is producing methane in the ocean under the Enceladus ice shell, analyzed in a 2021 paper from Antonin Affholder (now at the University of Arizona) and colleagues, using Cassini data from passages through the plumes erupting from the southern polar regions. The scientists produced mathematical models and used a Bayesian analysis to weigh the probabilities that the methane is being created by life or through abiotic processes. The result: The plume data are consistent with both possibilities, although it’s interesting, based on what we know about hydrothermal chemistry on earth, that the amount of methane is higher than would be expected through any abiotic explanation. So we can’t rule out the possibility of some kind of microorganisms under the ice on Enceladus, and clearly need data...

Chasing nomadic worlds: Opening up the space between the stars

by Paul Gilster | Dec 28, 2022 | Uncategorized | 58 Comments

Ongoing projects like JHU/APL’s Interstellar Probe pose the question of just how we define an ‘interstellar’ journey. Does reaching the local interstellar medium outside the heliosphere qualify? JPL thinks so, which is why when you check on the latest news from the Voyagers, you see references to the Voyager Interstellar Mission. Andreas Hein and team, however, think there is a lot more to be said about targets between here and the nearest star. With the assistance of colleagues Manasvi Lingam and Marshall Eubanks, Andreas lays out targets as exotic as ‘rogue planets’ and brown dwarfs and ponders the implications for mission design. The author is Executive Director and Director Technical Programs of the UK-based not-for-profit Initiative for Interstellar Studies (i4is), where he is coordinating and contributing to research on diverse topics such as missions to interstellar objects, laser sail probes, self-replicating spacecraft, and world ships. He is also an associate professor of...

A Role for Comets in Europa’s Ocean?

by Paul Gilster | Dec 21, 2022 | Outer Solar System | 11 Comments

The role comets may play in the formation of life seems to be much in the news these days. Following our look at interstellar comets as a possibly deliberate way to spread life in the cosmos, I ran across a paper from Evan Carnahan (University of Texas at Austin) and colleagues (at JPL, Williams College as well as UT-Austin) that studies the surface of Europa with an eye toward explaining how impact features may evolve. Craters could be cometary in origin and need not necessarily penetrate completely through the ice, for the team's simulations of ice deformation show drainage into the ocean below from much smaller events. Here comets as well as asteroids come into play as impactors, their role being not as carriers of life per se but as mechanisms for mixing already existing materials from the surface into the ocean. Image: Tyre, a large impact crater on Europa. Credit: NASA/JPL/DLR. That, of course, gets the attention, for getting surface oxidants produced by solar irradiation...

The Ethics of Directed Panspermia

by Paul Gilster | Dec 16, 2022 | Culture and Society | 54 Comments

Interstellar flight poses no shortage of ethical questions. How to proceed if an intelligent species is discovered is a classic. If the species is primitive in terms of technology, do we announce ourselves to it, or observe from a distance, following some version of Star Trek's Prime Directive? One way into such issues is to ask how we would like to be treated ourselves if, say, a Type II civilization - stunningly more powerful than our own - were to show up entering the Solar System. Even more theoretical, though, is the question of panspermia, and in particular the idea of propagating life by making panspermia a matter of policy. Directed panspermia, as we saw in the last post, is the idea of using technology to spread life deliberately, something that is not currently within our power but can be reasonably extrapolated as one path humans might choose within a century or two. The key question is why we would do this, and on the broadest level, the answer takes in what seems to be...

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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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