Our recent discussions about Claudio Maccone's FOCAL mission to the Sun's gravitational focus, and the ongoing work at the Jet Propulsion Laboratory for NASA's Innovative Advanced Concepts office, have had Alex Tolley thinking about alternative scenarios. Yes, a spacecraft moving along the focal line extending from the solar gravitational lens (SGL) would be capable of extraordinary imaging, and could serve as a communications relay for interstellar probes, but that tricky Sundiver maneuver suggested by Slava Turyshev and team in their 'string of pearls' concept puts huge demands on sail materials. Moreover, we'd ideally like to be able to slow the craft as it moves along the focus, to allow maximum time for observations. To achieve both fast transit and maneuverability at the gravitational focus, Alex advocates beamed propulsion, a method whose advantages and consequences are discussed below. Synergies with the ongoing Breakthrough Starshot effort are apparent. by Alex Tolley The...
A Holiday Thought Looking Ahead
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.
Stellar Flares as an Aid to Life Detection
The interesting transient associated with Proxima Centauri and monitored by Breakthrough Listen reminds us of a key fact about red dwarf stars and the planets around them. Such stars, especially in their youth, are prone to high flare activity, meaning violent, unpredictable emissions that can deplete atmospheric gases like ozone. Even if the atmosphere survives strong stellar winds, the loss of ozone can lead to high levels of ultraviolet radiation reaching the surface and compromising any life there. That stellar flares can be dramatic is captured in the image below, showing a filament eruption from the Sun and accompanying solar flares (credit: NASA/GSFC/SDO). As striking as the image is, it depicts activity on an older star less prone to strong flare activity than younger, smaller stars. We're also fortunate in having the shield offered by Earth's magnetic field, which can deflect the worst of the solar wind. Our G-class Sun lets us orbit at a comfortable distance, but planets in...
A Transient at Proxima Centauri?
I see there's now a Wikipedia page for BLC-1, the intriguing SETI detection made by Breakthrough Listen at the Parkes Observatory in Australia. The dataset in which the signal, found at 982 MHz, turned up comes from observations made in April and May of 2019, and it's good to know that Breakthrough is working up two papers on the signal and subsequent analysis, given that the public face of the detection was originally in the form of a story leaked to the British newspaper The Guardian before the backup research was available. Image: CSIRO's Parkes radio telescope in New South Wales, Australia. Credit: Shaun Amy. The first thing to say about BLC-1 is that the acronym stands for Breakthrough Listen Candidate 1, marking the first time a signal has made it through to actual 'candidate' status after five years of observations, which is itself noteworthy given the intensity of the effort. The second thing is that this is a transient, meaning it's short-lived, and it hasn't repeated. That...
JPL Work on a Gravitational Lensing Mission
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....
The FOCAL Radio Bridge
Getting a probe to another star is a big enough problem, but woven inextricably through it is the issue of communications. Adding payload steepens the propulsion curve in dramatic fashion, which is why recent thinking has dwelled so firmly on miniaturizing the spacecraft. Thus Breakthrough Starshot, which envisions payloads roughly on the order of a computer chip. No wonder, with spacecraft of that size, getting data back to Earth is such a daunting challenge. Can gravitational lensing help? We've seen that the Sun's mass shapes spacetime around it, bending light from targets on the other side so that electromagnetic waves come to a focal point about 550 AU out. The implications for imaging are under intense study at the Jet Propulsion Laboratory, where Slava Turyshev's team, working with a Phase III NIAC grant, is exploring "Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravitational Lens Mission," taking two prior studies, a Phase I and II at NIAC, forward...
Developing FOCAL Mission Concepts
In the early summer of 2005, I found myself, thanks to the efforts of Greg Matloff and Princeton's Ed Belbruno, in Princeton for a conference called New Trends in Astrodynamics and Applications II, which Dr. Belbruno had organized. I was to give a brief talk at the end of the session summarizing what was going on in the interstellar travel community. Two days of chill rain didn't dampen my enthusiasm at seeing Greg and his wife, the artist C Bangs, as well as Belbruno himself, who had been a great help as I put together my Centauri Dreams book. And on the morning of the first day of the conference, I joined Greg, C and Claudio Maccone for breakfast at the Nassau Inn, Princeton's lovely colonial era hostelry. I've since had the opportunity to talk with Dr. Maccone many times at conferences, and one year enjoyed memorable meals with him in the Italian Alps, but that first encounter really sticks in my mind. I had been thinking about gravitational lensing for several years, but it was...
Claudio Maccone: A Deep Dive into Gravitational Lensing
Sorry for the server problems the last few days, which resulted in some tinkering under the hood by people far more skilled at such things than I am. Meanwhile, those experiencing deja vu at seeing this post should take heart -- there is a simple explanation. Last week I posted an earlier article about Claudio Maccone's upcoming presentation on gravitational lensing and the FOCAL mission to exploit it, but had to withdraw the post when I realized the live session, a 'webinar' organized by Ravi Kumar Kopparapu (NASA GSFC) and Jacob Haqq Misra (Blue Marble Space Institute of Science), might not be available beyond a restricted audience. Once that was straightened out, the meeting had already occurred, but fortunately Dr. Maccone's session was recorded and is now available here. I'm going to go ahead and run the rest of that earlier post now, because most people didn't see it. Even so, and despite the fact that it was only up on the site for a few minutes, that turned out to be long...
Server Problems Resolved
I'm going to keep Alex Tolley's fine essay (below) at the top for another day, in hopes of re-starting the comment thread that was going along so nicely before the site went down. Then tomorrow we'll start talking about gravitational lensing, in the first of a series that may extend until next week.
Distinguishing Between Biological and Machine Civilization Techno-signatures
If we ever make a SETI detection, will it be of biological beings or machine intelligence? As Alex Tolley explains in today's essay, there are reasons for favoring the latter possibility, leading our author to compose what he calls a 'light-hearted speculation' about machines searching for other civilizations of their own kind. Life seems to be easy compared to this. We are developing the tools to delve into planetary atmospheres in search of biosignatures, hoping to cull out ambiguities. But is there an equivalent in the machine world of a biosignature, and how would it be found? Interesting implications arise, some of them seemingly close to home. by Alex Tolley Curiosity Rover. Credit Nasa. Terry Bisson's amusing short sci-fi story "They're made Out of Meat" [4], is a communication between two individuals who express their disbelief that a biological species (detected on Earth by a galactic survey) can possibly be intelligent. The denouement is to erase the record of discovery...
Deep Future: The Next Supercontinent
Science fiction writers range freely through time, making many scientific papers fertile ground for plot ideas and settings. So here's an extraordinary one. We know that Earth's continents used to be packed into a single large land mass called Pangaea, which is thought to have broken apart about 200 million years ago as tectonic plates shifted. Interestingly, we can expect a remote future in which the continents will have once again come together, as Michael Way (NASA GSFC) has pointed out at an online poster session at the ongoing virtual meeting of the American Geophysical Union. And such a supercontinent has ramifications for habitability. Let's talk about those because they have a bearing on astrobiology as we examine exoplanets and consider their suitability for life. We're a decade or so (at minimum) away from being able to determine how land and sea are distributed on a nearby world, but climate modeling is useful as we look toward estimating habitability. That involves, as...
Musings on Fusion and the Interstellar Ramjet
Proton-proton fusion produces 99 percent of the Sun's energy, in a process that begins with two hydrogen nuclei and ends with one helium nucleus, releasing energy along the way. We'd love to exploit the fusion process to create energy for our own directed uses, which is what Robert Bussard was thinking about with his interstellar ramjet when he published the idea in 1960. Such a ship might deploy electromagnetic fields thousands of kilometers in diameter to scoop up atoms from the interstellar medium, using them as reaction mass for the fusion that would drive it. Carl Sagan was a great enthusiast for the concept, and would describe it vividly in the book he wrote with Russian astronomer and astrophysicist Iosif S. Shklovskii. In Intelligent Life in the Universe (1966), the authors discuss a journey that takes advantage of time dilation, allowing a lightspeed-hugging starship powered by these methods to reach galactic center in a mere 21 years of ship-time; i.e., time as perceived by...