Those of you who follow Centauri Dreams through email probably received an inadvertent test post this morning. My apologies. The post was triggered by work on the site's internals and was generated automatically by the email software module. Work on the site continues, but I think the email issue is fixed, so I anticipate no more of these. Thanks for your patience.
Freeman Dyson’s Gravitational Machines
What an intriguing thing to find Freeman Dyson’s “Gravitational Machines” paper popping up on arXiv. This one is yet another example of Dyson’s prescience, for in it he examines, decades before the actual event, how gravitational waves could be produced and detected, although he uses neutron stars rather than black holes as his focus. Fair enough. When this was written, in 1962, black holes were far more conjectural than they appear in most of the scientific literature today. But what a tangled history this paper presents. First of all, how does a 1962 paper get onto arXiv? A quick check reveals the uploader as David Derbes, a name that should resonate with Dyson purists. Derbes (University of Chicago Laboratory Schools, now retired) is the power behind getting Dyson’s lectures on quantum electrodynamics, first given at Cornell in 1951, into print in the volume Advanced Quantum Mechanics (World Scientific Publishing, 2007). He’s also an editor on Sidney Coleman’s Lectures on...
The Prevalence of ‘Jupiters’ around Larger Stars
Work on the Centauri Dreams internals continues, with the unwelcome result that the site has been popped offline twice because of a possible security problem. Needless to say, this has to be resolved before I can move forward on other aspects of the rebuild. While I deal with that issue, let me respond to a few backchannel questions about yesterday’s post on gas giants in red dwarf planetary systems. What I’m being asked about is my comment that gas giants like Jupiter, at similar distances and installation, around other classes of stars are common compared to what we see at red dwarfs. This has been a problematic issue, and the matter is a long way from achieving a consensus among researchers. A moment’s reflection yields the reason: Finding gas giants in outer system orbits around a star like the Sun is no easy matter. Radial velocity is most sensitive when dealing with large planets in tight orbits, which is why the first detections in main sequence stellar systems, beginning back...
A Scarcity of ‘Jupiters’ in Red Dwarf Systems
Gas giant worlds like Jupiter may be uncommon around red dwarf stars, as a number of recent studies have found. It would be useful to tighten up the data, however, because many of the papers on this matter have used stellar samples at the high end of the mass range of M-dwarfs. At the Center for Astrophysics | Harvard & Smithsonian (CfA), Emily Pass and colleagues have gone to work on the question by looking at lower-mass M-dwarfs and working with a lot of them, some 200 in their sample, all within 15 parsecs. The question is not purely academic, for some scientists suggest that the presence of a Jupiter-class planet – not uncommon around G-class stars like the Sun – is a factor in the development of life. Migrating inward from a formation in the first few hundred million years of the Solar System’s existence, Jupiter would have stirred up plenty of icy cometary bodies through gravitational interactions. Impacts from this infall into the inner system likely delivered a great deal...
Catching Up
Centauri Dreams began as a website back in August of 2004. I’m startled to realize, looking through the stats that my site’s software provides, that in the subsequent nineteen years, there have been 4,659 posts, along with close to 100,000 comments. The irony is that I started the site simply as a research venue for myself, thinking to keep up with the latest news by building a collection of articles and scientific papers. It took about a year before I even switched on the comments function. One of the benefits of publishing for such a length of time is perspective, as the interstellar research scene has grown and changed over the past two decades. But one thing I didn’t do is keep up with the software. Always focused on content, I’ve kept writing but have let too many generations of internal programming stay mired in older iterations. The dangers of this are obvious. A site with obsolete internals is all too open to hacking. And now, completely normal upgrades to some of the site’s...
SETI: Asking the Right Questions
Did Carl Sagan play a role in the famous Arecibo message transmitted toward the Hercules Cluster in 1974? I’ve always assumed so, given Sagan’s connection with Frank Drake, who was then at Cornell University, where Sagan spent most of his career. But opinion seems to vary. Artist/scientist Joe Davis, who now has affiliations with both MIT’s Laboratory of Molecular Structure and Harvard Medical School, noted in an email this morning that Sagan’s widow, Ann Druyan, supports the connection, but according to Davis, Drake himself denied Sagan’s role in the composition or transmission of the message. I mention all this because of Tuesday’s post on the simulated SETI signal being sent via ESO’s Mars ExoMars Trace Gas Orbiter, as a kind of work of art in its own right as well as a test case in building public involvement in the decoding of an unusual message. The idea of doing that irresistibly recalled Joe Davis because in 1988 Davis performed his own act of scientific art involving SETI,...
Links for IRG Interstellar Symposium in Montreal
The preliminary program for the Interstellar Research Group’s 8th Interstellar Symposium in Montreal is now available. For those of you heading to the event, I want to add that the early bird registration period for attending at a discount is May 31. Registration fees go up after that date. Registering at the conference hotel can be handled here. Registration before the 31st is recommended to get a room within the block reserved for IRG.
First Contact: A Global Simulation
Now and again scientists think of interesting ways to use our space missions in contexts for which they were not designed. I’m thinking, for example, of the ‘pale blue dot’ image snapped by Voyager 1 in 1990, an iconic view that forcibly speaks to the immensity of the universe and the smallness of the place we inhabit. Voyager’s cameras, we might recall, were added only after a debate among mission designers, some of whom argued that the mission could proceed without any cameras aboard. Fortunately, the camera advocates won, with results we’re all familiar with. Now we have a project out of The SETI Institute that would use a European Space Agency mission in a novel way, one that also challenges our thinking about our place in the cosmos. Daniela de Paulis, who serves as artist in residence at the institute, is working across numerous disciplines with researchers involved in SETI and astronautics to create A Sign in Space, the creation of an ‘extraterrestrial’ message. This is not a...
Remembering Jim Early (1943-2023)
I was saddened to learn of the recent death of James Early, author of a key paper on interstellar sail missions and a frequent attendee at IRG events (or TVIW, as the organization was known when I first met him). Jim passed away on April 28 in Saint George, UT at the age of 80, a well-liked figure in the interstellar community and a fine scientist. I wish I had known him better. I ran into him for the first time in a slightly awkward way, which Jim, ever the gentleman, quickly made light of. What happened was this. In 2012 I was researching damage that an interstellar sail mission might experience in the boost phase of its journey. Somewhere I had seen what I recall as a color image in a magazine (OMNI?) showing a battered, torn sail docked in what looked to be a repair facility at the end of an interstellar crossing. It raised the obvious question: If we did get a sail up to, say, 5% of the speed of light, wouldn’t even the tiniest particles along the way create significant damage...
Assembly theory (AT) – A New Approach to Detecting Extraterrestrial Life Unrecognizable by Present Technologies
With landers on places like Enceladus conceivable in the not distant future, how we might recognize extraterrestrial life if and when we run into it is no small matter. But maybe we can draw conclusions by addressing the complexity of an object, calculating what it would take to produce it. Don Wilkins considers this approach in today's essay as he lays out the background of Assembly Theory. A retired aerospace engineer with thirty-five years experience in designing, developing, testing, manufacturing and deploying avionics, Don tells me he has been an avid supporter of space flight and exploration all the way back to the days of Project Mercury. Based in St. Louis, where he is an adjunct instructor of electronics at Washington University, Don holds twelve patents and is involved with the university’s efforts at increasing participation in science, technology, engineering, and math. Have a look at how we might deploy AT methods not only in our system but around other stars. by Don...
Game Changer: Exploring the New Paradigm for Deep Space
The game changer for space exploration in coming decades will be self-assembly, enabling the growth of a new and invigorating paradigm in which multiple smallsat sailcraft launched as ‘rideshare’ payloads augment huge ‘flagship’ missions. Self-assembly allows formation-flying smallsats to emerge enroute as larger, fully capable craft carrying complex payloads to target. The case for this grows out of Slava Turyshev and team’s work at JPL as they refine the conceptual design for a mission to the solar gravitational lens at 550 AU and beyond. The advantages are patent, including lower cost, fast transit times and full capability at destination. Aspects of this paradigm are beginning to be explored in the literature, as I’ve been reminded by Alex Tolley, who forwarded an interesting paper out of the University of Padua (Italy). Drawing on an international team, lead author Giovanni Santi explores the use of CubeSat-scale spacecraft driven by sail technologies, in this case ‘lightsails’...
An Ice Giant’s Possible Oceans
Further fueling my interest in reaching the ice giants is a study in the Journal of Geophysical Research: Planets that investigates the possibility of oceans on the major moons of Uranus. Imaged by Voyager 2, Uranus is otherwise unvisited by our spacecraft, but Miranda, Ariel, Titania, Oberon and Umbriel hold considerable interest given what we are learning about oceans beneath the surface of icy moons. Hence the need to examine the Voyager 2 data in light of updated computer modeling. Julie Castillo-Rogez (JPL) is lead author of the paper: “When it comes to small bodies – dwarf planets and moons – planetary scientists previously have found evidence of oceans in several unlikely places, including the dwarf planets Ceres and Pluto, and Saturn’s moon Mimas. So there are mechanisms at play that we don’t fully understand. This paper investigates what those could be and how they are relevant to the many bodies in the solar system that could be rich in water but have limited internal...
GJ 486b: An Atmosphere around a Rocky M-dwarf Planet?
I might have mentioned the issues involving the James Webb Space Telescope’s MIRI instrument in my earlier post on in-flight maintenance and repair. MIRI is the Mid-Infrared Instrument that last summer had issues with friction in one of the wheels that selects between short, medium and longer wavelengths. Now there seems to be a problem, however slight, that affects the amount of light registered by MIRI’s sensors. The problems seem minor and are under investigation, which is a good thing because we need MIRI’s capabilities to study systems like GJ 486, where a transiting rocky exoplanet may or may not be showing traces of water in an atmosphere that may or may not be there. MIRI should help sort out the issue, which was raised through observations with another JWST instrument, the Near-Infrared Spectrograph (NIRSpec). The latter shows tantalizing evidence of water vapor, but the problem is untangling whether that signal is coming from the rocky planet or the star. This points to an...
GJ 486b: An Atmosphere around a Rocky M-dwarf Planet?
I might have mentioned the issues involving the James Webb Space Telescope’s MIRI instrument in my earlier post on in-flight maintenance and repair. MIRI is the Mid-Infrared Instrument that last summer had issues with friction in one of the wheels that selects between short, medium and longer wavelengths. Now there seems to be a problem, however slight, that affects the amount of light registered by MIRI’s sensors. The problems seem minor and are under investigation, which is a good thing because we need MIRI’s capabilities to study systems like GJ 486, where a transiting rocky exoplanet may or may not be showing traces of water in an atmosphere that may or may not be there. MIRI should help sort out the issue, which was raised through observations with another JWST instrument, the Near-Infrared Spectrograph (NIRSpec). The latter shows tantalizing evidence of water vapor, but the problem is untangling whether that signal is coming from the rocky planet or the star. This points to an...
Voyager as Technosignature
Here’s an image that brings out the philosopher in me, or maybe the poet. It’s Voyager 1, as detected by a new processing system called COSMIC, now deployed at the Very Large Array west of Socorro, New Mexico. Conceived as a way of collecting data in the search for technosignatures, COSMIC (Commensal Open-Source Multimode Interferometer Cluster) taps data from the ongoing VLASS (Very Large Array Sky Survey) project and shunts them into a receiver designed to spot narrow channels, on the order of one hertz wide, to spot possible components of a technosignature. Technosignatures fire the imagination as we contemplate advanced civilizations going about their business and the possibility of eavesdropping upon them. But for me, the image below conjures up thoughts of human persistence and a gutsy engagement with the biggest issues we face. Why are we here, and where exactly are we in the galaxy? In the cosmos? Spacecraft like the Voyagers were part of the effort to explore the Solar...
Working the Problem: Deep Space Repair
RIME (Radar for Icy Moons Exploration) is the first instrument ever deployed to the outer Solar System that can make direct measurements of conditions below the surface of an object. That makes it precisely tailored for Europa as well as Ganymede and Callisto, two other Galilean moons that also seem to have an internal ocean. Consider it a radar ‘sounder’ that can penetrate up to 9 kilometers below surface ice. RIME is a major part of why JUICE is going to the moons of Jupiter. Consider it problematic as well, at least for the moment, while controllers working the JUICE mission try to solve an unexpected deployment issue. The 16-meter long antenna shows movement, but continues to have trouble in becoming released from its mounting bracket. The antenna is currently about a third of its full intended length, according to ESA, partially extended but still stowed away. Image: Shortly after launch on 14 April, ESA’s Jupiter Icy Moons Explorer, JUICE, captured this image with its JUICE...
Part II: Sherlock Holmes and the Case of the Spherical Lens: Reflections on a Gravity Lens Telescope
Aerospace engineer Wes Kelly continues his investigations into gravitational lensing with a deep dive into what it will take to use the phenomenon to construct a close-up image of an exoplanet. For continuity, he leads off with the last few paragraphs of Part I, which then segue into the practicalities of flying a mission like JPL's Solar Gravitational Lens concept, and the difficulties of extracting a workable image from the maze of lensed photons. The bending of light in a gravitational field may offer our best chance to see surface features like continents and seasonal change on a world around another star. The question to be resolved: Just how does General Relativity make this possible? by Wes Kelly Conclusion of Part I At this point, having one’s hands on an all-around deflection angle for light at the edges of a “spherical lens” of about 700,000 kilometers radius (or b equal to the radius of the sun rS), if it were an objective lens of a corresponding telescope, what would be...
Sherlock Holmes and the Case of the Spherical Lens: Reflections on a Gravity Lens Telescope (Part I)
A growing interest in JPL's Solar Gravitational Lens mission here takes Wes Kelly on an odyssey into the past. A long-time Centauri Dreams contributor, Wes looks at the discovery of gravitational lensing, which takes us back not only to Einstein but to a putative planet that never existed. Part II of the essay, which will run in a few days, will treat the thorny issues lensing presents as we consider untangling the close-up image of an exoplanet, using an observatory hundreds of AU from the Sun. Wes has pursued a lifetime interest in flight through the air, in orbit and even to the stars. Known on Centauri Dreams as ‘wdk,’ he runs a small aerospace company in Houston (Triton Systems,LLC), founded for the purpose of developing a partially reusable HTOL launch vehicle for delivering small satellites to space. The company also provides aerospace engineering services to NASA and other customers, starting with contracts in the 1990s. Kelly studied aerospace engineering at the University...
SETI and Signal Leakage: Where Do Our Transmissions Go?
The old trope about signals from Earth reaching other civilizations receives an interesting twist when you ponder just what those signals might be. In his novel Contact, Carl Sagan has researchers led by Ellie Arroway discover an encrypted TV signal showing images from the Berlin Olympics in 1936. Thus returned, the signal announces contact (in a rather uncomfortable way). More comfortable is the old reference to aliens watching “I Love Lucy” episodes in their expanding cone of flight that began in 1951. How such signals could be detected is another matter. I’m reminded of a good friend whose passion for classical music has caused him to amass a collection of recordings that rival the holdings of a major archive. John likes to compare different versions of various pieces of music. How did Beecham handle Delius’ “A Walk in the Paradise Garden” as opposed to Leonard Slatkin? Collectors find fascination in such things. And one day John called me with a question. He was collecting the...
Probing the Shifting Surface of Icy Moons
In celebration of the recent JUICE launch, a few thoughts on what we’re learning about Ganymede, with eight years to go before the spacecraft enters the system and eventually settles into orbit around the icy moon. Specifically, let’s consider a paper just published in Icarus that offers results applicable not just to Ganymede but also Europa and Enceladus, those fascinating and possibly life-bearing worlds. We learn that when we look at the surface of an icy moon, we’re seeing in part the result of quakes within its structure caused by the gravitational pull of the parent planet. Image: ESA’s latest interplanetary mission, Juice, lifted off on an?Ariane 5 rocket?from?Europe’s Spaceport?in French 09:14 local time/08:14 EDT on 14 April 2023 to begin its eight-year journey to Jupiter, where it will study in detail the gas giant planet’s three large ocean-bearing moons: Ganymede, Callisto and Europa. Credit: ESA. The Icarus paper homes in on the link between such quakes, long presumed...