Centauri Dreams
Imagining and Planning Interstellar Exploration
New Horizons: Going Deep in the Kuiper Belt
We’ve retrieved all the data from New Horizons’ flyby of Pluto/Charon in 2015, the last of it being acquired on October 25 of this year. But data analysis is a long and fascinating process, with papers emerging in the journals and new discoveries peppering their pages. The New Horizons science team submitted almost 50 scientific papers in 2016, and we can expect that stream of publication to continue in high gear as we move deeper into the Kuiper Belt.
For New Horizons is very much an ongoing enterprise, as Alan Stern’s latest PI’s Perspective makes clear. We have an encounter with a small Kuiper Belt object (KBO) called 2014 MU69 to think about, and the symmetry that Stern points to in his essay is striking. Two years ago New Horizons had just emerged from cruise hibernation as preparations for the Pluto/Charon encounter began. And exactly two years from now, we’ll be again following the incoming datastream as the last of the New Horizons targets comes into breathtaking proximity.
But 2014 MU69 isn’t the only KBO in the cards. Stern describes what’s next:
The year ahead will begin with observations of a half-dozen KBOs by our LORRI [LOng Range Reconnaissance Imager] telescope/imager in January. Those observations, like the ones we made in 2016 of another half-dozen KBOs, are designed to better understand the orbits, surface properties, shapes, satellite systems and frequency of rings around these objects. These observations can’t be done from any ground-based telescope, the Hubble Space Telescope, or any other spacecraft – because all of those other resources are either too far away or viewing from the wrong angles to accomplish this science. So this work is something that only New Horizons can accomplish.
Ponder that 2014 MU69 is almost 6.5 billion kilometers out and you have to wonder when we’ll next get a spacecraft this deep into the system. The answer has as much to do with funding as our technologies, since a wide variety of outer system probes have been under discussion in the last forty years. Each new deep space mission that actually flies fuels public interest, but the phenomenon is all too brief, and although space exploration seems to be flourishing in the movies these days, it’s hard to see a New Horizons sequel any time soon.
Even so, I’m optimistic in the longer term because the process in view in a mission of this complexity works its own kind of magic. Yesterday I wrote about Vera Rubin’s ability to communicate not just her love of the stars to young scientists she worked with but her values of tenacity, curiosity and exploration. In the same way, a mission executed with the precision of New Horizons has to set an example for budding scientists everywhere, a young population out of which will surely grow at least a few future principal investigators like Alan Stern.
New Horizons is a long way from home, and January will be used to take advantage of its position through measurements of hydrogen gas in the heliosphere (using the Alice ultraviolet spectrometer) and charged particles and dust (through the SWAP, PEPSSI and SDC instruments). What’s different today about space missions is that a student with a PC can drill deep into all this, following tweets from researchers, exploring ideas on blogs and reading direct communications from the mission team. The Apollo days were fantastic, but we could never get as close to a mission as we can get to a New Horizons, or a Dawn or a Rosetta.
There are going to be things to track in early 2017 as New Horizons makes yet another course correction, but the spacecraft will then enter hibernation until September, when a new round of KBO observations begins. As Stern points out, flyby operations for 2014 MU69 are set to commence in July of 2018, meaning that while the vehicle hibernates, the mission teams will be writing and testing the command sequences for the January 1, 2019 flyby.
So the absorbing process of a deep space mission continues to play out in space and on Earth. The first observations ever made of a Kuiper Belt Object from within the Kuiper Belt itself are now out in the form of a paper in Astrophysical Journal Letters. The object is 1994 JR1, studied through the LORRI instrument after the Pluto/Charon flyby from a distance of 1.85 AU and then about six months later from a distance of 0.71 AU. The earlier observations were supplemented with simultaneous Hubble studies of the same object. We learn quite a lot from these early observations. From the paper’s summary:
(15810) 1994 JR1 has a V-R of 0.76, making it a very red KBO [V-R refers to spectral slope, a measure of reflectance vs wavelength]. Unique New Horizons observations showed that JR1 has a high surface roughness of 37±5°, indicating that it is potentially very cratered. They also showed that the rotational period of JR1 is 5.47±0.33 hours, faster than most similar-sized KBOs, and enabled a reduction of radial uncertainty of JR1’s position from 105 to 103 km.
Moreover, New Horizons has revealed this KBOs interactions with the objects around it:
Neptune perturbations bring Pluto and JR1 close together every 2.4 million years, when Pluto can perturb JR1’s orbit. Future ground-based photometry of JR1 would be useful to better constrain the period and opposition surge, and to allow preliminary estimates of JR1’s shape and pole. These proof of concept distant KBO observations demonstrate that the New Horizons extended mission will indeed be capable of observing dozens of distant KBOs during its flight through the Kuiper Belt.
Ongoing science like this from the outer Solar System will snare the attention of people making their initial way into astronomy and astronautics. Who knows what careers will be shaped by these studies, and what new targets that next generation will explore?
The paper is Porter et al., “The First High-Phase Observations of a KBO: New Horizons Imaging of (15810) 1994 JR1 from the Kuiper Belt,” Astrophysical Journal Letters Vol. 828, No. 2 (2016). Preprint available.
Vera Rubin (1928-2016)
When Vera Rubin went to Cornell University to earn a master’s degree, she quickly found herself immersed in galaxy dynamics, lured to the topic by Martha Stahr Carpenter. The interest, though, was a natural one; it drew on Rubin’s childhood fascination with the motion of stars across the sky. You could say that motion captivated her from her earliest days. At Cornell, she studied physics from such luminaries as Richard Feynman, Philip Morrison and Hans Bethe. She would complete the degree in 1951 and head on to Georgetown.
Rubin, who died on Christmas day, was possessed of a curiosity that made her ask questions others hadn’t thought of. In Bright Galaxies, Dark Matters (1997), a collection of her papers, the astronomer recalls writing to Milton Humason in 1949, asking him about the redshifts he and his colleagues were compiling. Rubin had heard that many had yet to be published, and she would use those she had to look for systematic motion among the galaxies, motion that would show up if you removed the Hubble expansion from the data.
“I found that many of these galaxies defined a great circle on the sky, or roughly a circle, and that there were large regions of positive and negative values of residual velocity,” Rubin told editor Sally Stephens in a 1992 interview. “What in fact I really found was the supergalactic plane, although I entitled the paper ‘Rotation of the Universe.'”
Rubin tended to dismiss this early work in later life (“I presume none of this work would hold up today”), and her paper was rejected by the Astrophysical Journal as well as the Astronomical Journal, though later presented at a 1950 AAS meeting. Even so, the questions she raised were hugely significant, and at the time under study by Kurt Gödel at Princeton, the school that turned down her graduate application because of her gender. What Rubin was homing in on was the presence of large-scale galactic motion.
Today, we talk about the Rubin-Ford effect, the observation that describes the motion of our galaxy relative to a sample of galaxies at varying distances and compares this to its motion relative to the cosmic microwave background (the Ford here is Kent Ford, an astronomer whose spectrometer became critical for Rubin’s studies of stellar motion in spiral galaxies). Early work that had been flawed by insufficient data would eventually grow into this result.
I always tend to link Rubin and Fritz Zwicky in my thinking. Way back in 1933, the Swiss astronomer who taught most of his career at Caltech was noting discrepancies between the apparent mass of galaxies in the Coma cluster and the amount of light they produced, leading him to coin the phrase ‘dunkle Materie’ (dark matter) to explain the effect. Both Zwicky and Rubin had an uncanny knack for seeing places where the universe was posing questions. For Rubin, it would become the motion of spiral galaxies that defined her career.
The problem leaped out at astronomers once Rubin put her finger on it. You would expect galaxies to spin in fairly conventional ways, with stars nearer the center moving faster than those on the outskirts, just as in our own Solar System, the inner planets orbit the Sun much faster than the outer worlds. But by 1974 Rubin was able to show that the outer stars in spiral galaxies move much faster than could be explained by the mass of the visible matter in the galaxies. Dark matter again reared its head, and became the subject of intense investigation.
We still haven’t observed dark matter directly, though the current calculation is that about 27 percent of the universe is made up of the stuff, with only 5 percent being the normal matter we had until recently assumed was all there was. By 1998, we had learned, too, of dark energy and the continuing expansion of the universe, yet another mystery demanding an explanation. The dark energy work would produce a Nobel Prize; dark matter has yet to do so. Rubin’s exclusion from the Nobel occupies much of the media commentary on her death. I think Phil Plait’s discussion is on the money.
Rubin would put her painstaking methods to work on over 200 galaxies in her career. Finishing her PhD in 1954 (her thesis advisor at Georgetown was George Gamow, a science popularizer and early advocate of Big Bang theory), Rubin taught at Georgetown for eleven years before joining the Carnegie Institution for Science in 1965, where she began her collaboration with Ford. She would become the second female astronomer elected to the National Academy of Sciences and would receive the National Medal of Science in 1993.
Rubin’s loss resonates through the world of astronomy and is keenly felt by the many she influenced, especially women who were inspired by her example to tackle a career in the physical sciences. We can measure careers by papers published and ideas propagated, but it’s all too easy to miss the more intangible factors like lives touched and careers launched. On all these scores Vera Rubin deserves the thanks of the field she did so much to shape.
Orbital Determination for Proxima Centauri
Let’s talk this morning about the relationship of Proxima Centauri to nearby Centauri A and B, because it’s an important issue in our investigations of Proxima b, not to mention the evolution of the entire system. Have a look at the image below, which shows Proxima Centauri’s orbit as determined by Pierre Kervella (CNRS/Universidad de Chile), Frédéric Thévenin (Observatoire de la Côte d’Azur) and Christophe Lovis (Observatoire astronomique de l’Universite? de Gene?ve). The three astronomers have demonstrated that all three stars — Proxima Centauri as well as Centauri A and B — form a single, gravitationally bound system.
Image: Proxima Centauri’s orbit (shown in yellow) around the Centauri A and B binary. Credit: Kervella, Thévenin and Lovis.
A couple of things to point out here, the first being the overall image. You’ll see Alpha Centauri clearly labeled within the yellow ellipse of Proxima’s orbit. Off to the right of the ellipse, you’ll see Beta Centauri. I often see the image of these two stars identified as Centauri A and B, but Kervella et al have it right. The single bright ‘star’ within the ellipse is the combined light of Centauri A and B. Beta Centauri, at the right, is an entirely different star, itself a triple system in the constellation Centaurus, at a distance of about 400 light years.
Now as to that orbit — 550,000 years for a single revolution — things get interesting. One reason it has been important to firm up Proxima’s orbit is that while a bound star would have affected the development of the entire system, the question has until now been unresolved. Was Proxima Centauri actually bound to Centauri A and B, or could it simply be passing by, associated with A and B only by happenstance? Back in 1993 Robert Matthews and Gerard Gilmore found this to be a borderline case, calling for further kinematic data to clarify the issue.
When Jeremy Wertheimer and Gregory Laughlin (UC-Santa Cruz) attacked the problem in 2006, they found it ‘quite likely’ that Proxima Centauri was bound to the A/B pair. If this were the case, it would mean that the trio probably formed together out of the same nearby material, with the result that we could expect them to have the same age and metallicity. Laughlin and Wertheimer assumed that future, yet more accurate kinematic measurements would make it clear ‘that Proxima Cen is currently near the apastron of an eccentric orbit…’
And now we have Kervella and team, who have used the HARPS instrument (High Accuracy Radial Velocity Planet Searcher) on ESO’s 3.6m instrument at La Silla to make the call. Using radial velocity and astrometry, the researchers have surmounted the main problem with determining Proxima’s bound state. The lack of high-precision radial velocity measurements has been the result of Proxima’s relative faintness, but drilling down into HARPS data has produced a new radial velocity of ?21.700 ± 0.027 km s?1, which tracks nicely with the prediction of Wertheimer and Laughlin, and is low enough to indicate a bound state.
As we consider that interesting planet around Proxima Centauri, we now can ponder that its star is the same age as Centauri A and B, and that its age is a comparable 6 billion years, making the planet about a billion years older than our Earth. Exactly how the planet formed becomes an interesting issue as well, because we have interactions between three stars to think about. From the paper:
The orbital motion of Proxima could have played a significant role in the formation and evolution of its planet. Barnes et al. (2016) proposed that a passage of Proxima close to ? Cen may have destabilized the original orbit(s) of Proxima’s planet(s), resulting in the current position of Proxima b. Conversely, it may also have influenced circumbinary planet formation around ? Cen (Worth & Sigurdsson 2016). Alternatively, Proxima b may also have formed as a distant circumbinary planet of ? Cen, and was subsequently captured by Proxima. In these scenarios, it could be an ocean planet resulting from the meltdown of an icy body (Brugger et al. 2016). Proxima b may therefore not have been located in the habitable zone (Ribas et al. 2016) for as long as the age of the ? Cen system (5 to 7 Ga; Miglio & Montalbán 2005; Eggenberger et al. 2004; Kervella et al. 2003; Thévenin et al. 2002).
So there we are. Plenty of alternatives to ponder as we look into the origins of the nearest known planet to our Solar System. Just how the researchers tuned up the radial velocity data to avoid the problem of convective blueshift — where the star’s unstable surface can shift the observed wavelength of spectral lines – and gravitational redshift, which can likewise be misleading, is covered in the paper’s appendix. The selection of four strong very high signal-to-noise emission lines made the difference in this exquisitely tight measurement.
The paper is Kervella, Thévenin & Lovis, “Proxima’s orbit around ? Centauri,” accepted at Astronomy & Astrophysics (preprint).
Seasonal Break
The other day on the hugely enjoyable Galactic Journey site, I ran into an interesting historical tidbit. Here, from the 1753 Cyclopædia: or, An Universal Dictionary of Arts and Sciences by Ephraim Chambers is a definition of the word ‘interstellar.’
And with a modernized presentation:
“Interstellar, is a word used by some authors to express those parts of the universe that are without and beyond our Solar system; in which are supposed to several other systems of planets moving around the fixed stars as the centers of their respective motions: and if it be true, as it is not improbable, that each fixed star is thus a sun to some habitable orbs, that move round it, the interstellar world will be infinitely the greater part of the universe.”
Another early instance of planetary systems around other stars in wide circulation at an early date. Chambers was working for John Senex, a London-based globe-maker, when he conceived the plan for his Cyclopædia, a project to which he soon devoted his entire attention. The first edition appeared by subscription in 1728 in a two volume, 2466 page folio, but the work, one of the first general encyclopedias to be published in English, would see numerous further editions, including one in Ireland as well as an Italian translation.
Those of you who are not yet familiar with Galactic Journey will want to remedy the lack, especially if you enjoy science fiction as much as most Centauri Dreams readers do. The site is something of a time machine, written from the perspective of science fiction magazines and events of over 50 years ago, and what’s delightful to me is that I often find issues of Analog or Fantastic discussed that I bought off the newsstand when they appeared. And because I love magazine fiction, every one of those issues is still here on my shelves, approximately ten feet from where I’m now writing.
We’re pushing into holiday travel time, so I’m going to close up shop until next week. Let me wish all of you a happy season and thank you for the comments and suggestions with which you’ve always enlivened the site. We have much to talk about in coming days, but for now, safe journey to all of you on the road.
Citizen SETI
I love watching people who have a passion for science constructing projects in ways that benefit the community. I once dabbled in radio astronomy through the Society of Amateur Radio Astronomers, and I could also point to the SETI League, with 1500 members on all seven continents engaged in one way or another with local SETI projects. And these days most everyone has heard the story of Planet Hunters, the citizen science project that identified the unusual Boyajian’s Star (KIC 8462852). When I heard from Roger Guay and Scott Guerin, who have been making their own theoretical contributions to SETI, I knew I wanted to tell their story here. The post that follows lays out an alien civilization detection simulation and a tool for visualizing how technological cultures might interact, with an entertaining coda about an unusual construct called a ‘Dyson shutter.’ I’m going to let Roger and Scott introduce themselves as they explain how their ideas developed.
by Roger Guay and Scott Guerin
Citizen Science plays an increasingly important role across several scientific disciplines and especially in the fields of astronomy and SETI. Tabby’s star, discovered by members of the Planet Hunters project and the SETI@home project are recent examples of massively parallel citizen-science efforts. Those large-scale projects are counterbalanced by individuals whose near obsession with a subject compels them to study, write, code, draw, design, talk about, or build artifacts that help them understand the ideas that excite them.
Roger Guay and Scott Guerin, working in isolation, recently discovered parallel evolution in their thinking about SETI and the challenges of interstellar detection and communication. Guay has undertaken the programming of a 10,000 x 8,000 light year swath of a typical galaxy and populates it with random radiating communicating civilizations. His model allows users to tweak basic parameters to see how frequently potential detections occur. Guerin is more interested in a galaxy-wide model and has used worksheets and animations to bring his thoughts to light. His ultimate goal is to develop a parametric civilization model so that interactions, if any, can be studied. However, at the core, both efforts were attempts at visualizing the Fermi Paradox across space-time, and both experimenters show how fading electromagnetic halos may be all that’s left for us to discover of an extraterrestrial civilization, if we listen hard enough.
The backgrounds, mindsets, and tool kits available to Roger and Scott play an important role in their path to this blog.
Roger Guay
I am a retired Physicist and Technical Fellow Emeritus from Boeing in Seattle. I can’t remember when I first became interested in being a scientist (it was in grade school) but I do remember when I first became obsessed with the Fermi paradox. It was during a discussion while on a road trip with a colleague. At first, this discussion mainly revolved around the almost unfathomable vastness of space and time in our galaxy, but then turned to parameters of the Drake equation. The one that was the most controversial was L, the lifetime of an Intelligent Civilization or IC.
The casual newcomer to the Drake equation will tend to assume a relatively long lifetime for an IC, but when considering detection methods such as SETI uses, one must adjust L to reflect the lifetime of the technology of the detection method. For example, SETI is listening for electromagnetic transmissions in the microwave to radio and TV range. So, L has to be the estimated lifetime of that technology. For SETI’s technology, we’ll call this the Radio Age. On Earth, the Radio Age started about 100 years ago and has already fallen off due to technological advances such as the internet and satellite communication. So I argued, an L = 150 ± 50 years might be a more reasonable assumption for the Drake equation when considering the detection method of listening for radio signals.
At this point the discussion was quite intense! When I thought about an L equal to a few hundred years in a galaxy that continues to evolve over a 13-billion-year lifespan, the image that came to my mind was that of fireflies in the night. And that was the precursor for my Alien Civilization Detection or ACD simulation.
One can imagine electromagnetic or “radio” bubbles appearing randomly in time and space and growing in size over time. At any instant in time the bubble from an IC will have a radius equal to the speed of light times the amount of time since that IC first began broadcasting. These bubbles will continue to grow at the speed of light. When the IC stops broadcasting for whatever reason, the bubble will become hollow and the shell thickness will reflect the time duration of that IC’s Radio Age lifetime.
If the age of our galaxy is compressed into one year, we on Earth have been “leaking” radio and television signals into space for only a small fraction of a second. And, considering the enormity of space and the fact that our “leakage” radiation has only made it to a few hundred stars out of the two to four hundred billion in our galaxy, one inevitably realizes there must be a significant synchronization problem that arises when ICs attempt to detect one another. So what does this synchronicity problem look like visually?
To answer this question my tasks became clear: dynamically generate and animate radio bubbles randomly in space and time, grow them at the speed of light at very fast accelerated rate in a highly compressed region of the galaxy, fade them over time for inverse square law decay, and then analyze the scene for detection. No Problem!!!
Using LiveCode, a modern derivative of HyperCard on steroids, I began my 5-year project to scientifically simulate this problem. Using the Monte Carlo Method whereby randomly generated rings denoting EM radiation from ICs pop into existence in a 8,000 X 10,000 LY region of the galaxy* centered on our solar system at a rate of about 100 years per second, the firefly analogy came to life. And the key to determining detection potential is to recognize that it can only occur when a radiation bubble is passing over another IC that is actively listening. This is the synchronicity problem that is dramatically apparent when the simulation is run!
To be scientifically accurate and meaningful, some basic assumptions were required:
- 1. ICs will appear not only randomly in space, but also randomly in time.
- 2. ICs will inevitably transition into (and probably out of) a Radio/TV age where they too will “leak” electromagnetic radiation into space.
- 3. The radio bubbles are assumed to be spherically homogeneous**.
To use the ACD simulation, the user chooses and adjusts parameters such as Max Range, Transmit and Listen times*** and N, the Drake equation estimate of the number of ICs in the galaxy at any given instant. During a simulation run, potential detections are tallied and the overall probability of detection is displayed.
About two years ago, as the project continued to evolve, I became aware of Stephan Webb’s encyclopedic book on the Fermi Paradox, If the Universe is Teeming with Aliens … Where is Everybody? This book was most influential in my thinking and the way I shaped the existing version of the ACD simulation.
A snapshot of the main screen of the ACD simulation midway through a 10,000 year run.
A Webb review of the ACD simulation is available here: http://stephenwebb.info/category/fermi-paradox/
And you can download it here at this Dropbox link:
https://www.dropbox.com/sh/dlkx24shyfjsoax/AADeFd2wZyZxvLYHU2f4jJ0ha?dl=0
Conclusions? The ACD simulation dramatically demonstrates that there is indeed a synchronicity problem that automatically arises when ICs attempt to detect one another. And for reasonable (based on Earth’s specifications) Drake equation parameter selections, detection potentials are shown to be typically hundreds of years apart. In other words, we can expect to search for a few hundred years before finding another IC in our section of the galaxy. When you consider Occam’s razor, is not this synchronicity problem the most logical resolution to the Fermi Paradox?
Footnotes:
* The thickness of the Milky Way is small compared to its diameter. So for regions close to the center of the thickness, we can approximate with a 2-dimensional model.
** Careful consideration has to be given to this last assumption: Of course, it is not accurate in that the radiation from a typical IC is assumed to be composed of many different sources and have widely varying parameters, as they are on Earth. But the bottom line is that the homogenous distribution gives the best case scenario of detection potential. An example of when to apply this thinking is to consider laser transmission vs radio broadcast. Since a laser would presumably by highly directed and therefore more intense at greater distances, the user of the ACD simulation might choose a Higher Max Range but at the same time realize that pointing problems will make detection potential much smaller than the ACD indicates. The ACD does not take this directly into consideration. Room for the ACD to grow?
*** One of the features of this simulation is that the user can make independent selections of both the transmit and listening times of ICs, whereas the Drake equation lumps them together in the lifetime parameter.
Scott Guerin
I grew up north of Milwaukee, Wisconsin and was the kid in 5th grade who would draw a nuclear reactor on the classroom’s chalkboard. My youthful designs were influenced by Voyage to the Bottom of the Sea, Lost in Space, everything NASA, and 2001: a Space Odyssey. In the mid 70s, I was a technical illustrator at the molecular biology laboratory at UW Madison and, after graduation with a fine arts degree, I went on to a 30-year career as an interpretive designer of permanent exhibits in science and history museums.
I began visually exploring SETI over two years ago in order to answer three questions: First, why is such a thought-provoking subject so often presented only in math and graphs thereby limiting information to experts? Secondly, why is the Fermi Paradox a paradox? Thirdly, what form might an interstellar “we are here” signaling technology take?
Using Sketchup, I built a simple galactic model to see what scenarios matched the current state of affairs: silence and absence. At a scale of 1 meter = 1 light year, I positioned Sol appropriately, and randomly “dropped” representations of civilizations (I refer to them as CivObjects) into the model. Imagine dropping a cup full of old washers, nails, wires, and screws onto a flat, 10″ plate and seeing if any happen to overlap with a grain-of-salt-sized solar system (and that speck is still ~105 too large).
The short answer is that they didn’t overlap and I’ve concluded that the synchronicity issue, combined with weak listening and looking protocols is a strong answer to the paradox. When synchronicity is considered along with sheer rarity of emitting civilizations (my personal stance), the silence makes even more sense.
For scale, the green area at lower right represents the Kepler star field if it were a ~6,000 LY diameter sphere. The solid discs represent currently emitting civilizations, the halos represent civilizations that have stopped emissions over time, and the lines and wedges represent directed communications. I sent this diagram to Paul and Marc at Centauri Dreams who were kind enough to pass it on to several leading scientists and they graciously, and quickly, replied with encouragement.
Curtis Charles Mead’s 2013 Harvard dissertation “A Configurable Terasample-per-second Imaging System for Optical SETI,” George Greenstein’s Understanding the Universe, Tarter’s, and the Benford’s papers, among others, were influential in my next steps. I realized the halos were unrealistic representations of a civilization’s electromagnetic emissions and that if you could see them from afar, they could be visualized as prickly, 3-dimensional sea urchin-like artifacts with tight beams of powerful radar, microwave, and laser emanating from a mushy sphere of less directional, weaker electromagnetic radiation.
From afar, Earth’s EM halo is a lumpy, flattened sphere some 120LY in radius dating to the first radio experiments in the late 1890’s. The 1974 Arecibo message toward M13 is shown being emitted at the 10 o’clock position.
From Tarter’s 2001 paper “At current levels of sensitivity, targeted microwave searches could detect the equivalent power of strong TV transmitters at a distance of 1 light year (the red sphere at center in the diagram), or the equivalent power of strong military radars to 300 ly, and the strongest signal generated on Earth (Arecibo planetary radar) to 3000 ly, whereas sky surveys are typically two orders of magnitude less sensitive. The sensitivity of current optical searches could detect megajoule pulses focused with a 10-m telescope out to a distance of 200 ly.”
In this speculative diagram, two civilizations “converse” across 70 LY. Mead’s paper confirms the aiming accuracy needed to correct for the the proper motion of the stars, given a laser beam just a handful of AU wide at the distance illustrated, is within human grasp. The civilizations shown would most likely have been emitting EM for hundreds of years so that their raw EM halos are so large and diffuse they cannot be shown in the diagram. The magenta blob represents the elemental EM “hum” of a civilization within a couple LY, the green spikes represent tightly beamed microwaves for typical communications and radar , while the yellow spikes are lasers reaching out to probes, being used as light-sail boosters, and fostering long distance high-bandwidth communications. Each civilization has an EM fingerprint, affected by their system’s ecliptic angle and rotation, persistence of ability, and types of technologies deployed — these equate to a unique CivObject.
In advance of achieving the goal of a fully parametric 3D model, I manually animated several kinds of civilizations and their interactions by imagining a CivObject as a variant of a Minkowski space-time cone. I move the cone’s Z axis (time) through a galactic hypersurface to illustrate a civilization’s history of passive and intentional transmission, as well as probes at sub-lightspeed. A CivObject’s anatomy reveals the course of a civilization’s history and I like to think of them as distant cousins of Hari Seldon’s prime radiant. https://vimeo.com/195239607 password: setiwow!
The anatomy of a CivObject allows arbitrary time scales to be visualized as function of xy directionality, EM strength, and type of emission. Below is Earth’s as a reference. Increasing transmission power is suggested by color.
I found it easy to animate transmissions but continue to struggle with visualizing periods of listening and the strength of receivers. Like Guay, I concluded that a potential detection can occur only when a transmission passes through a listening civilization. A “Conversing” model designed to actually simulate communication interactions needs to address both ends of “the line” with a full matrix of transmitter/receiver power ratios as well as sending/listening durations, directions, sensitivities, and intensities. In addition, a more realistic galactic model including 3d star locations, the GHZ, and interstellar extinction/absorption rates is needed.
And now for some sci-fi
A few months before KIC 8462852 was announced and Dyson Swarms became all the rage, I noticed one of those old ventilators on top of a barn roof and thought that if a Kardashev II civilization scaled it up to +-1AU diameter, it would become a solar powered, omni-directional signalling device capable of sending an “Intelligence was here” message across interstellar space. I called it a Dyson Shutter.
Imagine a star surrounded by a number of ribbon-like light sails connected at their poles. Each vane’s stability, movement, and position is controlled by the angle of sail relative to incoming photons from the central star. The shutter would be a high tech, ultra-low bandwidth, scalable construct. I have imagined that each sail, at the equator, would be no less than one Earth diameter wide which is at the lower end of Kepler-grade detection.
Depending on the number constructed, the vanes could be programmed to shift into simple configurations such as fibonacci and prime number sequences.
I imagine the Dyson Shutter remains in a stable message period for hundreds of rotations. Perhaps there are “services” for the occasional visitor, perhaps it has defenses against comets, incoming asteroids, or inter-galactic graffiti artists. Perhaps it is an intelligent being itself but is it a lure, a trap, a collector, or colleague? Is it possible Tabby’s star is a Dyson Shutter undergoing a multi-year message reconfiguration?
The shutter’s poles are imagined to be filled with command and control systems, manufacturing facilities, spaceports, etc.
Wrap
We hope that our work as presented here might inspire some of you to join the ranks of the Citizen Scientist. There are many opportunities and science needs the help. With today’s access to information and digital tools, anyone with a little passion for their ideas and a lot of imagination and persistence can help communicate complex issues to the public and make contributions to science. We hope that our stories resonate with at least some of you. Please let us know what you think and let’s all push back on the frontiers of ignorance!
PanSTARRS: Digital Sky Survey Data Release
A 1.8 meter telescope at the summit of Haleakal? on Maui is the first instrument in use at the Pan-STARRS (Panoramic Survey Telescope & Rapid Response System) observatory. Pan-STARRS recently completed a digital survey of the sky in visible and infrared wavelengths that began in May of 2010, a project that surveyed the entire sky visible from Hawaii over a period of four years, scanning it 12 times in each of five filters. The result is a collection of 3 billion separate sources, including not just stars and galaxies but numerous transient, moving and variable objects. All told, we’re dealing with about 2 petabytes of data.
Now we learn that data from the survey is being made available worldwide. Ken Chambers, director of the Pan-STARRS observatories, comments:
“The Pan-STARRS1 Surveys allow anyone to access millions of images and use the database and catalogs containing precision measurements of billions of stars and galaxies. Pan-STARRS has made discoveries from Near Earth Objects and Kuiper Belt Objects in the Solar System to lonely planets between the stars; it has mapped the dust in three dimensions in our galaxy and found new streams of stars; and it has found new kinds of exploding stars and distant quasars in the early universe.”
How heartening it is to see extensive information on more than 3 billion sources now becoming publicly available. The catalog of four years of observations is being rolled out in two phases, the first being the release of the ‘Static Sky,’ which presents the average of each of the observing epochs. For every object, in other words, we get an average value for its position, brightness and colors — it will also be possible to get the stack image in each of the observed colors, while galaxies will include further information. Next year, the plan is to release the full database giving information and images for each individual epoch.
Image: This compressed view of the entire sky visible from Hawaii by the Pan-STARRS1 Observatory is the result of half a million exposures, each about 45 seconds in length, taken over a period of 4 years. The shape comes from making a map of the celestial sphere, like a map of the Earth, but leaving out the southern quarter. The disk of the Milky Way looks like a yellow arc, and the dust lanes show up as reddish brown filaments. The background is made up of billions of faint stars and galaxies. If printed at full resolution, the image would be 2.4 kilometers long, and you would have to get close and squint to see the detail. Credit: Danny Farrow, Pan-STARRS1 Science Consortium and Max Planck Institute for Extraterrestial Physics.
As Centauri Dreams readers know, our focus here has been predominantly on objects relatively near to the Sun — one of our purposes, after all, is to consider interstellar probes and their potential targets. On that score, we learn this from Thomas Henning (Max Planck Institutes for Astronomy, Heidelberg):
“Based on Pan-STARRS, researchers are able to measure distances, motions and special characteristics such as the multiplicity fraction of all nearby stars, brown dwarfs, and of stellar remnants like, for example white dwarfs. This will expand the census of almost all objects in the solar neighbourhood to distances of about 300 light-years.”
There is definitely an exoplanet component here. Henning continues:
“The Pan-STARRS data will also allow a much better characterization of low-mass star formation in stellar clusters. Furthermore, we gathered about 4 million stellar light curves to identify Jupiter-like planets in close orbits around cool dwarf stars in order to constrain the fraction of such extrasolar planetary systems.”
In terms of protecting our planet, Pan-STARRS devoted part of its four-year survey to searching for hazardous asteroids, an effort that proved so successful that following the end of the survey, NASA began using the telescope and its 1.4 Gigapixel camera (GPC1) for further asteroid investigations. Researchers believe that over 90 percent of near-Earth objects larger than 1 kilometer have already been found, making the current focus of the Near Earth Object program the discovery of objects larger than 140 meters. Clearly, Pan-STARRS can help.
Image: Contributions of various astronomical surveys to the discovery of near-Earth asteroids, showing totals for NEAs of all sizes. Credit: Alan B. Chamberlin/Jet Propulsion Laboratory/NASA.
From a much broader perspective, PAN-STARRS has mapped our galaxy at a level of detail the MPIA is saying has never been achieved before, offering ‘a deep and global view’ of a significant fraction of the Milky Way’s plane and disk, areas that surveys generally avoid because of the complexity of these dense and dusty regions. In M31, the closest neighboring galaxy, the survey has detected several microlensing events and numerous Cepheid variables. The next step, according to this MPIA news release, is to measure redshifts of galaxies and other cosmological objects to analyze the distribution of galaxies in three dimensions, data that can provide constraints on our standard cosmological model.
The data from the first part of the Pan-STARRS survey is being archived at the Space Telescope Science Institute (STScI) in Baltimore and can be accessed through MAST (Mikulski Archive for Space Telescopes) using the Pan-STARRS1 link.
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