by Paul Gilster | Jan 17, 2014 | Culture and Society |
by J. N. Nielsen
Nick Nielsen thinks big. In fact, today’s essay, which ranges over vast stretches of time and space and places human civilization in a continually expanding context, reminds me of nothing so much as the Olaf Stapledon of Starmaker. As with Stapledon, the questions are deeply philosophical: If we find a way to travel arbitrarily close to the speed of light, thus creating a civilization Carl Sagan once envisioned — one spread not only over space but over aeons — how will we cohere as a species? And what forms will our migrations take after the first pioneers have left our niche in the cosmos behind? For more of Nielsen’s work, see his blogs Grand Strategy: The View from Oregon and Grand Strategy Annex.
In my previous Centauri Dreams post, Cosmic Loneliness and Interstellar Travel, I argued that our cosmic loneliness is the reason we seek peer species and peer civilizations in the universe, that interstellar travel is a more practicable way to explore the universe for intelligent life than SETI/METI communication, and that such travel will eventually result as a consequence of the development of a 1G starship (a spacecraft that can accelerate or decelerate at a rate equal to terrestrial gravity). In my Centauri Dreams post prior to that, SETI, METI, and Existential Risk, I argued that SETI efforts will find technological civilizations if they are out there, and, by the same token, we will be found whether we want to be found or not, but we ought not to shrink from this possibility because the potential risk is at the same time a civilizational opportunity.
In this present post I would like to explore what kind of large-scale spacefaring civilization would emerge from the positions I have taken in the previous posts, specifically, the idea that we would be found by advanced civilizations if there were any, but we haven’t been found. I would like for these three Centauri Dreams posts to be understood as one long argument (as Darwin said of his Origins), and the argument is this: if it makes more sense to travel than to communicate, and if there is no sign of travel to Earth by extraterrestrial civilizations, then we are alone, or very nearly alone, in the cosmos. We may not be absolutely alone in the universe, but we are likely to be sufficiently alone that we can embark upon the initial stages of building a spacefaring civilization without the likelihood of finding any peer civilization in our initial voyages.
On the basis of physics as we understand it today, the spacefaring civilization we are capable of building will be subject to the constraints of a relativistic universe (except in the case of a disruptive breakthrough in science or technology), but we must learn to see this limitation as being at the same time an opportunity. Relativistic interstellar travel, and the spacefaring civilization that emerges from such voyages, will contribute materially to the existential viability of a civilization. This is the great opportunity that lurks within the limitations imposed by relativistic travel.
In my first post to Centauri Dreams, Existential Risk and Far Future Civilization, I argued that the existential viability of civilization is contingent upon three conditions: 1) knowledge, 2) redundancy, and 3) autonomy. Knowledge transforms uncertainties into calculable risks that can be managed; redundancy assures that if one center of civilization succumbs to an existential risk, other centers of civilization will remain to continue the life of civilization; autonomy among centers of civilization assures that distinct centers will pursue distinct existential risk mitigation strategies, therefore lowering the likelihood that multiple redundant centers of civilization would all succumb to the same existential risk.
A spacefaring civilization established by relativistic interstellar travel secures all three of these conditions in an especially robust manner. And it does so, as Carl Sagan said, in virtue of, “another and quite unexpected method.” The unexpected method of securing existential risk mitigation is what I call the establishment of a temporally distributed civilization, i.e., a civilization that is distributed not only in space, but also in time.
The idea of a temporally distributed civilization is something that I began to develop in my 2012 100YSS presentation, “The Large Scale Structure of Spacefaring Civilization.” There I observed that we tend to think of human expansion into the universe as distribution in space, but in a relativistic universe, distribution in time cannot be separated from distribution in space. As the engineering innovations of industrial-technological civilization bring us gradually ever closer to the possibility of a 1G starship, our spatial distribution in the universe will at the same time become a temporal distribution through time dilation: the faster we go and the farther we go, the more time will have elapsed at our point of origin.
Time dilation is not only subject to misconception, but the way in which the “twin paradox” has been commonly presented seems almost as though calculated to elicit a poignant response: one of two twins remains on Earth, while another flies to a distant star at relativistic velocities. When the traveling twin, who has experienced acceleration, returns, the twin who has remained on Earth is now old, while the returning traveler is yet young. The greater the speed of travel, the greater the time dilation effect, so that a 1G starship would allow a traveler to not only exceed the age of a twin, but to exceed the age of the Earth, and this would be sad indeed. It sounds like madness to undertake such a voyage.
[Image credit: http://physicsforme.wordpress.com/2012/04/26/the-twin-paradox-in-relativity-revisited/]
Even if many or most individuals are dissuaded from interstellar travel by time dilation, or are risk averse and would never fly to the stars out of fear, it would ludicrous to argue that no one will take the risk, or that no one would be willing to leave the world behind. Even under the conditions of total separation I strongly suspect that there would be a few individuals and small groups willing to cut their ties to their homeworld and go on a one-way journey to the stars. And it is highly likely that among the first to make the journey to the stars, some will never be heard from again (Some of these may prove to be questions as fascinating to the public as the fate of Amelia Earhart.) They will be as lost to us as early ships lost at sea. Perhaps they will go farther than any of us; perhaps they will be waiting for us at the edge of the universe when we finally arrive, en masse, as a civilization.
This, however, represents a limiting case of relativistic travel. To give an accurate picture of the large scale structure of spacefaring civilizations, the twins paradox must be recast in terms of populations rather than individuals. As in evolutionary biology, it is the population that is the unit of selection, although in this context it is a human population that is temporally selected, or rather selects itself. The vanguard of spacefaring civilization will consist of populations who desire their differentiation from the civilization of source (eocivilization); this process will be strongly selective of those who feel alienated from the civilization of their birth and are willing to abandon it.
There will be long-term socio-political consequences of the establishment of initial interstellar settlements by those least attached to the civilization that made spacefaring possible, but these socio-political consequences will be limited by the small size of the communities in question. In the same way that any communicating civilization would be overtaken by any traveling civilization, because of the technological innovations that would occur during the period of time while waiting for a signal to travel interstellar distances and then return, so too any civilization that experiences less time as a result of time dilation would be overtaken by a non-accelerated center of civilization. Later technological innovations from the original center of civilization will eventually overtake the vanguard, but the scales of space, time, and technology involved will mean that it will be an open question whether these vanguard communities will have transformed themselves into something unrecognizable in the interim.
It is likely that the greater part of innovation in propulsion technologies (and therefore that attainment of greater velocities) will occur wherever the greater part of the human population is to be found, which in the initial stages of a spacefaring civilization means that most advances in propulsion technologies will occur on a given species’ home planet while its initial starships will be isolated from these innovations. Thus technologies on the home world will surpass those who have made the first interstellar journeys.
In so far as such interstellar travel is continually improved and refined, it would not be isolated groups, but rather large groups that will eventually travel, or many individuals or small groups who could rendezvous at an appointed place and time. Collectively, such a group of travelers would bring its contemporaneous civilization along with it—they would both travel to the stars, and have their familiar civilization, although that civilization would not continue to mirror the civilization of source indefinitely as it independently developed, though later voyages are likely to diverge less from the source of civilization than earlier voyages.
Beyond a certain threshold, when off-planet population clusters approach the levels of density required for innovative scientific research on an industrial scale, and as innovations from the original center of the civilization result in cheaper, more effective, and more widely distributed transportation technologies, the bias will shift from the certainties of settled planetary life to the possibilities of life on a larger scope and scale that represents an increase in an order of magnitude of the choices and opportunities available. For the same reasons that populations have steadily moved from rural areas to urban centers, driving further urbanization once urbanization had become a viable way of life for the formerly-rural masses, populations will steadily migrate from settled planetary life to an accelerated life that joins the time-dilated community once this becomes a viable way of life for the civilized masses.
As civilization enlarges in scope, it is subject to a greater degree to the natural forces that govern the large scale structures of space-time. At the largest cosmological scale, the theory of relativity would prove to be constitutive of civilization. The farther a civilization extends in space, the greater number of frames of reference it encounters and the greater the diversity of these frames of reference. It is this process that will yield a temporally distributed civilization.
In the context of a temporally distributed civilization, a distinction must be made between the chronological age of a civilization and the temporal span that a civilization covers, since the cosmological distribution of centers of civilization at relativistic velocities means that accelerated populations cover a greater span of time than unaccelerated populations remaining at the original source of civilization. The temporal span of a civilization is the total portion of the age of the universe occupied by a given spacefaring civilization. This temporal span will be much larger in its scale of time than the chronological age of the civilization.
More significantly, distinct centers of civilization widely dispersed in space and time (i.e., separated by a significant temporal span) may be chronologically very close in age. When velocities close to the speed of light are attainable, this temporal span may be dramatic. Centers of civilization separated by thousands or even millions of light years may be chronologically only a few years apart, so that essentially the same civilization exists millions of years apart in terms of its temporal span. Separation of months or years or even decades amounts to little more than a rounding error in terms of the scale of time involved.
This distribution of essentially the same civilization throughout widely separated spans of time will result in a very high degree of existential risk mitigation, since these temporally distributed centers of civilization will not even be subjected to the same natural disasters occurring on a cosmological scale, as they will inhabit different ages of the universe. A sterilizing gamma ray burst may doom the unfortunate center of civilization coeval with that disaster, but other coeval centers of civilization will be spared this particular risk, though they may be subject to other existential risks.
These coeval centers of civilization, approximately the same chronological age, but widely separated across the universe as faster and farther travel takes us ever greater distances from the original source of our civilization, will be like stepping stones across the cosmos. An interstellar traveler might pass from one arm of the Milky Way galaxy to another, always having a familiar center of civilization to stop and to pause. Some would choose to stay and maintain that center of civilization (and its coeval character), while others may choose to go farther. Such stepping stones across the cosmos might eventually take us from galaxy to galaxy, cluster to cluster, and supercluster to supercluster.
The new centers of civilization that result from interstellar voyaging, and which can serve as stepping stones across the cosmos, will be connected to each other as peer civilizations. It is only when you seek to retrace your steps that you come “back” to a near-peer civilization (i.e., a civilization sufficiently removed in time that it is no longer a peer simpliciter), now removed by degrees of separation in time, or even to a non-peer civilization, the farther and faster you go back to the former source of civilization. If homeworld civilization stagnates, one might even return to something like a peer civilization, but even a peer civilization would be unrecognizable, as the continents of Earth rearrange themselves and all our cities and monuments disappear and are replaced by new structures, until the Earth is no longer habitable.
The cosmos itself forces us to confront the fact that you can’t go home again. Earth is our cosmological home, and once we leave it for the stars we will not be able to return to the world that we left behind. But we will take our terrestrial civilization with us to the stars, and these new centers of civilization established by interstellar voyaging will possess the knowledge, redundancy, and autonomy requisite to mitigating any existential risk.
The civilization that I have described will be both strikingly similar to and radically different from the civilization that we know today, and we will have to formulate new modes of self-understanding in order to conceptualize our place within such a cosmic order. The advent of temporally distributed civilization will mean that the historical consciousness that human civilization has laboriously constructed, and which we have greatly expanded since the formulation of scientific historiography, will have to be expanded and extended once again by the expanded and extended human experience of a civilization that spans the geometry of spacetime across the galaxy and eventually across the universe, step by step.
by Paul Gilster | Jan 16, 2014 | Asteroid and Comet Deflection |
Just over 8300 people have now signed the petition supporting the New Horizons Message Initiative. The approach of the 10,000 figure reminds me to jog those who haven’t to stop by the site to sign the petition. For those not yet aware of the NHMI, the idea is to upload a crowdsourced package of images and data to the New Horizons spacecraft once it has completed its science mission at Pluto/Charon and any Kuiper Belt Object within range.
Jon Lomberg’s team calls the NHMI a ‘Voyager Golden Record 2.0,’ a worthy goal indeed, and I’ll also mention that the names of the first 10,000 signing the petition will be uploaded along with the images and data. For me, one of the most interesting aspects of the initiative will be to see how the crowdsourcing project works to determine both the form and the content of the message. New Horizons’ principal investigator Alan Stern has signed off on the idea, saying “I think it will inspire and engage people to think about SETI and New Horizons in new ways.”
While we work on developing this self-portrait of our species, it’s interesting to see the new ‘Messages to Bennu!’ campaign that’s developing through the OSIRIS-REx mission, in conjunction with The Planetary Society. OSIRIS-REx stands for — get ready for it — Origins-Spectral Interpretation Resource Identification Security Regolith Explorer. It’s a robotic mission, to be launched in 2016, that will spend more than two years at Bennu, a 500 meter carbonaceous asteroid. A surface sample will then be returned to Earth in 2023.
Image: When the OSIRIS-REx asteroid arrives at asteroid Bennu, it will study the asteroid from a distance before swooping down and grabbing a sample. On board the spacecraft will be the names of everybody participating in the “Messages to Bennu!” campaign. Credit: NASA/GSFC/UA.
The ‘messaging’ side of the mission involves putting a microchip with the names of people who have submitted them to The Planetary Society aboard the vehicle. You can sign up to have your name included here. Planetary Society CEO Bill Nye sees the mission of his organization as being ‘to engage the citizens of Earth in space exploration,’ an ongoing campaign that ‘Messages to Bennu!’ incorporates. We can hope that efforts like OSIRIS-REx and the New Horizons Message Initiative help to reawaken an all too lethargic public involvement with space.
The OSIRIS-REx countdown clock actually started on December 9, 2013, looking 999 days ahead to a launch in September of 2016. Principal investigator Dante Lauretta (University of Arizona) clearly likes the mission’s acronym, saying in a UA news release:
“Osiris was formed from pieces scattered across ancient Egypt, where he awoke as the bringer of life and ruler of the underworld. Our spacecraft has a similar story — it will be consist of components fabricated in locations around the world, that once together, will allow us to connect with a near-Earth object that is an accessible remnant from the formation of our solar system.”
As to Bennu, the target asteroid, it is a near-Earth object whose orbit is completed every 436 days, bringing it close to the Earth every six years. The object is considered a B-type asteroid, a subgrouping of the dark, carbonaceous C-type asteroids. These objects are useful for study because they have undergone little processing since the time of their formation. In addition to in situ studies and the sample return, OSIRIS-REx will also help us refine Bennu’s orbit by studying the Yarkovsky effect — the thermal force on the object — constraining the specific properties of the asteroid that make this effect a factor in its future trajectory. That’s useful information to have as we study near-Earth objects and potentially Earth-crossing orbits.
by Paul Gilster | Jan 15, 2014 | Exoplanetary Science |
2500 light years from Earth in the constellation of Cancer lies Messier 67, an open star cluster that is now known to be home to at least three planets. The new worlds, found using the HARPS spectrograph on the European Southern Observatory’s 3.6-meter instrument at La Silla, come as the result of an observation program covering 88 selected stars in the cluster over a period of six years. The finding is noteworthy because we have so few known planets in star clusters of any kind. Moreover, one of these planets orbits a truly Sun-like star.
Image: This wide-field image of the sky around the old open star cluster Messier 67 was created from images forming part of the Digitized Sky Survey 2. The cluster appears as a rich grouping of stars at the centre of the picture. Credit: ESO/Digitized Sky Survey 2 / Acknowledgement: Davide De Martin.
I’m cautious about calling anything ‘Sun-like’ given how loosely that term has been used over the years, but ESO astronomers say the cluster star YBP1194 fits the bill: It has a similar mass, and shows both chemical abundances and temperatures very close to Sol’s. Of the three discovered worlds, two orbit G-class stars similar to the Sun (the other is YBP1514), while the third orbits the red giant S364. The first two have roughly one-third the mass of Jupiter, orbiting their host stars in seven and five days respectively, while the third, more massive than Jupiter, orbits the red giant in 122 days.
Because most stars are thought to emerge from clusters, the small number of planets found in them has been a puzzle, spurring the recent work, which was led by Anna Brucalassi (Max Planck Institute for Extraterrestrial Physics). Says Brucalassi:
“In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars.”
Messier 67 contains about 500 stars and is an open cluster, a stellar grouping that has emerged from a single gas and dust cloud in the relatively recent past. Such clusters are normally found in the spiral arms of galaxies like ours. Globular clusters, on the other hand, are the much larger, spherical collections of stars that orbit around the center of the galaxy. Although a handful of planets have been found in open clusters (Messier 44 and NGC 6811 are other examples), no planets have yet turned up in the far more ancient globular clusters.
The lack of detected planets in open and globular clusters has been under discussion for some time now. From the paper:
To explain the dichotomy between field and cluster stars, it has been suggested that the cluster environment might have a significant impact on the disk-mass distribution. Eisner et al. (2008), studying disks around stars in the Orion Nebula Cluster (ONC), proposed that most of these stars do not possess sufficient mass in the disk to form Jupiter-mass planets or to support an eventual inward migration.
Brucalassi’s work, however, leads in a different direction. The paper continues:
van Saders & Gaudi (2011), in contrast, found no evidence in support of a fundamental difference in the short-period planet population between clusters and field stars, and attributed the non-detection of planets in transit surveys to the inadequate number of stars surveyed. This seems to be confirmed by the recent results.
Planets in open star clusters, in other words, are likely to be as common as those around isolated stars, a finding that draws not just from Brucalassi and team’s work but also from a number of recent observations discussed in the paper. The researchers continue to study M67 to examine the mass and chemical makeup of stars with and without planets.
The paper is Brucalassi et al., “Three planetary companions around M67 stars,” accepted for publication in Astronomy & Astrophysics. See also Pasquini et al., “Search for giant planets in M67 I. Overview” (preprint). And take note of Henry Cordova’s “The SETI Potential of Open Star Clusters,” which ran all the way back in 1995 in Vol. 1, No. 4 of SETIQuest, an early and prescient contribution.
by Paul Gilster | Jan 14, 2014 | Sail Concepts |
For years now Pekka Janhunen has been working on his concept of an electric sail with the same intensity that Claudio Maccone has brought to the gravitational focus mission called FOCAL. Both men are engaging advocates of their ideas, and having just had a good conversation with Dr. Maccone (by phone, unfortunately, as I’ve been down with the flu), I was pleased to see Dr. Janhunen’s electric sail pop up again in online discussions. It turns out that the physicist has been envisioning a sail mission to an unusual target.
Let’s talk a bit about the mission an electric sail enables. This is a solar wind-rider, taking advantage not of the momentum imparted by photons from the Sun but the stream of charged particles pushing from the Sun out to the heliopause (thereby blowing out the bubble’ in the interstellar medium we call the heliosphere). As Janhunen (Finnish Meteorological Institute) has designed it, the electric sail taps the Coulomb interaction in which particles are attracted or repulsed by an electric charge. The rotational motion of the spacecraft would allow the deployment of perhaps 100 tethers, thin wires that would be subsequently charged by an electron gun with the beam sent out along the spin axis.
Image: The electric sail is a space propulsion concept that uses the momentum of the solar wind to produce thrust. Credit: Alexandre Szames.
The electron gun keeps the spacecraft and tethers charged, with the electric field of the tethers extending tens of meters into the surrounding solar wind plasma — as the solar wind ‘blows,’ it pushes up against thin tethers that act, because of their charge, as wide surfaces against which the wind can push. The sail uses the attraction or repulsion of particles caused by the electric charge to ride the wind, the positively charged solar wind protons repelled by the positive voltage they meet in the charged tethers.
One disadvantage that electric sails bring to the mix, as opposed to solar sails like IKAROS, is that the solar wind is much weaker — Janhunen’s figures have it 5000 times weaker — than solar photon pressure at Earth’s distance from the Sun. This has come up before in comments here and it’s worth quoting Janhunen on the matter, from a site he maintains on electric sails:
The solar wind dynamic pressure varies but is on average about 2 nPa at Earth distance from the Sun… Due to the very large effective area and very low weight per unit length of a thin metal wire, the electric sail is still efficient, however. A 20-km long electric sail wire weighs only a few hundred grams and fits in a small reel, but when opened in space and connected to the spacecraft’s electron gun, it can produce several square kilometre effective solar wind sail area which is capable of extracting about 10 millinewton force from the solar wind.
Computer simulations using tethers up to 20 kilometers in length have yielded speeds of 100 kilometers per second, a nice step up from the 17 kps of Voyager 1, and enough to get a payload into the nearby interstellar medium in fifteen years. Or, as Janhunen describes in the recent paper on a Uranus atmospheric probe, an electric sail could reach the 7th planet in six years. Janhunen sees such a probe as equally applicable for a Titan mission and, indeed, missions to Neptune and Saturn itself, but notice that none of these are conceived as orbiter missions. A significant amount of chemical propellant is needed for orbital insertion unless we were to try aerocapture, but the problem with the latter is that it is at a much lower technical readiness level.
A demonstrator electric sail mission, then, is designed to keep costs down and reach its destination as fast as possible, with the interesting spin that, because we’re in need of no gravitational assists, the Uranus probe will have no launch window constraints. As defined in the paper on this work, the probe would consist of three modules stacked together: The electric sail module, a carrier module and an entry module. The entry module would be composed of the atmospheric probe and a heat-shield.
At approximately Saturn’s distance from the Sun, the electric sail module would be jettisoned and the carrier module used to adjust the trajectory as needed with small chemical thrusters (50 kg of propellant budgeted for here). And then the fun begins:
About 13 million km (8 days) before Uranus, the carrier module detaches itself from the entry module and makes a ~ 0.15 km/s transverse burn so that it passes by the planet at ~ 105 km distance, safely outside the ring system. Also a slowing down burn of the carrier module may be needed to optimise the link geometry during flyby.
Now events happen quickly. The entry module, protected by its heat shield, enters the atmosphere. A parachute is deployed and the heat shield drops away, with the probe now drifting down through the atmosphere of Uranus (think Huygens descending through Titan’s clouds), making measurements and transmitting data to the high gain antenna on the carrier module.
Thus we get atmospheric measurements of Uranus similar to what the Galileo probe was able to deliver at Jupiter, measuring the chemical and isotopic composition of the atmosphere. A successful mission builds the case for a series of such probes to Neptune, Saturn and Titan. Thus far Jupiter is the only giant planet whose atmosphere has been probed directly, and a second Jupiter probe using a similar instrument package would allow further useful comparisons. Our planet formation models, which predict chemical and isotope composition of the giant planet atmospheres, can thus be supplemented by in situ data.
Not to mention that we would learn much about flying and navigating an electric sail during the testing and implementation of the Uranus mission. The paper is Janhunen et al., “Fast E-sail Uranus entry probe mission,” submitted to the Meudon Uranus workshop (Sept 16-18, 2013) special issue of Planetary and Space Science (preprint).
by Paul Gilster | Jan 13, 2014 | Deep Sky Astronomy & Telescopes |
The supermassive black hole at the center of our galaxy comes to Centauri Dreams‘ attention every now and then, most recently on Friday, when we talked about its role in creating hypervelocity stars. At least some of these stars that are moving at speeds above galactic escape velocity may have been flung outward when a binary pair approached the black hole too closely, with one star being captured by it while the other was given its boost toward the intergalactic deeps.
At a mass of some four million Suns, Sagittarius A* (pronounced ‘Sagittarius A-star’) is relatively quiet, but we can study it through its interactions. And if scientists at the University of Michigan are right, those interactions are about to get a lot more interesting. A gas cloud some three times the mass of the Earth, dubbed G2 when it was found by German astronomers in 2011, is moving toward the black hole, which is 25,000 light years away near the constellations of Sagittarius and Scorpius.
What’s so unusual about this is the time-frame. We’re used to thinking in million-year increments at least when discussing astronomical events, but G2 was expected to encounter Sagittarius A* late last year. The event hasn’t occurred yet but astronomers think it will be a matter of only a few months before it happens. Exactly what happens next isn’t clear, says Jon Miller (University of Michigan), who along with colleague Nathalie Degenaar has been making daily images of the gas cloud’s approach using NASA’s orbiting Swift telescope.
“I would be delighted if Sagittarius A* suddenly became 10,000 times brighter,” Miller adds. “However it is possible that it will not react much—like a horse that won’t drink when led to water. If Sagittarius A* consumes some of G2, we can learn about black holes accreting at low levels—sneaking midnight snacks. It is potentially a unique window into how most black holes in the present-day universe accrete.”
Image: The galactic center as imaged by the Swift X-ray Telescope. This image is a montage of all data obtained in the monitoring program from 2006-2013. Credit: Nathalie Degenaar.
We have much to learn about the feeding habits of black holes. The Milky Way’s black hole isn’t nearly as bright as those in some galaxies. While we can’t see black holes directly because no light can escape from within, we can see the evidence of material falling into them, and it would be useful to know why some black holes consume matter at a slower pace than others. The X-ray wavelengths that Swift studies should give us our best data on the upcoming black hole encounter. A sudden spike in X-ray brightness would presumably mark the event, and the researchers will post the images online.
In studying black hole behavior, we’re also looking at key information about how galaxies live out their lives. After all, these objects are consuming matter and radically affecting the region around the very heart of the galaxy. “The way they do that influences the evolution of the entire galaxy—how stars are formed, how the galaxy grows, how it interacts with other galaxies,” says Nathalie Degenaar. Those of us of a certain age can delight in the recollection of Fred Hoyle’s 1957 novel The Black Cloud, in which a gas cloud approaching the Solar System turns out to be a bit more than astronomers had bargained for. Don’t miss this classic if you haven’t read it yet — you should have plenty of time to finish it before the G2 event.
