Paul Gilster | Centauri Dreams

OSIRIS-REx to Hunt for Earth ‘Trojans’

by Paul Gilster | Dec 14, 2016 | Asteroid and Comet Deflection | 18 Comments

The so-called 'trojan' asteroids that cluster at 60° ahead and behind the planet Jupiter make up a surprisingly populous category. Consider that thus far we have found only one trojan at Earth's Lagrangian points, while over 6000 have been discovered in Jupiter's orbit. The total number of trojans larger than 1 km in diameter associated with Jupiter has been estimated to be about 1 million, which matches up well with objects of equivalent size in the main asteroid belt. These days 'trojans' can also refer to similar bodies associated with other planets. We know, for example, of about 20 trojans involved with Neptune. That solitary Earth trojan, 2010 TK7, was discovered oscillating around Earth's L4 Lagrangian point in 2010 by the NEOWISE team using NASA's Wide-field Infrared Survey Explorer spacecraft. The object has a diameter of about 300 meters; its oscillations take it back and forth on a nearly 400 year cycle that at times puts it close to opposite the Sun with respect to...

Tidal Disruption by Black Hole?

by Paul Gilster | Dec 13, 2016 | Deep Sky Astronomy & Telescopes | 14 Comments

The supernova considered to be the brightest ever recorded may have been evidence of something even more exotic. The explosion was caught by the All Sky Automated Survey for SuperNovae (ASAS-SN), the event itself dubbed ASASSN-15h. Yesterday we looked at what happens to a star roughly as massive as the Sun as it goes through a red giant phase and becomes a white dwarf, but stars significantly more massive than the Sun take no such route. A star a minimum of 8 times the mass of the Sun can explode as a Type II supernova. But is that what ASASSN-15h really was? Detected in 2015 in a galaxy about 4 billion light years from Earth, the event has now been the subject of new work by an international team led by Giorgos Leloudas (Weizmann Institute of Science, Israel) and the Dark Cosmology Centre (Denmark). From this we get a new explanation: ASASSN-15h may have been the result of a rapidly spinning supermassive black hole tearing a relatively low mass star apart. The passing star, in other...

Glimpsing Our Solar System’s Future

by Paul Gilster | Dec 12, 2016 | Deep Sky Astronomy & Telescopes | 18 Comments

The star L2 Puppis (HD 56096), a red giant in the direction of the southern constellation Puppis (the Poop Deck), is the subject of interesting new investigations using data from the ALMA array in Chile. The star appears to belong on the asymptotic giant branch of the Hertzsprung-Russell diagram, a category dominated by highly evolved cool stars. The new study sees L2 Puppis as an analog for what our own Sun will become in billions of years. Thus Ward Homan (KU Leuven Institute of Astronomy, Belgium): "We discovered that L2 Puppis is about 10 billion years old. Five billion years ago, the star was an almost perfect twin of our Sun as it is today, with the same mass. One third of this mass was lost during the evolution of the star. The same will happen with our Sun in the very distant future." Image: Composite view of L2 Puppis in visible light | © P. Kervella et al. (CNRS/U. de Chile/Observatoire de Paris/LESIA/ESO/ALMA). But L2 Puppis is more than just an interesting glimpse at what...

John Glenn: An Arc of Fire

by Paul Gilster | Dec 9, 2016 | Uncategorized | 23 Comments

John Glenn was 95 when he died, but I have to admit I didn't think he'd make it to 41. The first American to orbit the Earth was 40 years old when he rode an Atlas rocket into the sky on February 20, 1962. I was a gawky kid, space-crazed, who had read absolutely everything I could find about the space program, and I knew just enough to understand that the Atlas, for all its muscular beauty, wasn't necessarily the safest thing you'd want to fly. Our school had set up a black and white television on the stage in the auditorium so we could all see the liftoff, which took place at 8:47 A.M. in St. Louis. In this era of enormous home viewing screens it's hard to imagine what a single small television could show to an auditorium filled with students, but at the time it was a window into history and we watched avidly as the rocket cut into the sky, and got later updates from teachers as Glenn orbited. We all assumed the hard part was over after the launch, and I know I was certainly...

Photonic Chip Boosts Exoplanet Detection

by Paul Gilster | Dec 8, 2016 | Exoplanetary Science | 17 Comments

The Australian Institute of Physics Congress ends today in Brisbane, concluding a schedule of talks that can be viewed here. Among the numerous research presentations was the description of a new optical chip for telescopes that should help astronomers tease out the image of a planet through thermal imaging, nulling out the light of the host star. The new photonic chip could be a replacement for bulk optics at the needed mid-infrared wavelengths. Harry-Dean Kenchington Goldsmith, a PhD candidate who built the chip at the Australian National University Physics Center, says that the same technology that allows astronomers to penetrate dust clouds to see planets in formation will also be used to study the atmospheres of potentially life-bearing planets. ANU's Steve Madden describes the chip as an interferometer that "adds equal but opposite light waves from a host sun which cancels out the light from the sun," making it possible to detect the much fainter light of a planet. He likened...

Loretta Jackson Delong (1948-2016)

by Paul Gilster | Dec 7, 2016 | Culture and Society | 2 Comments

I was saddened to learn through Tau Zero Foundation CEO Rhonda Stevenson of the recent death of Loretta Jackson Delong. Stevenson issued this statement The Tau Zero Foundation extends its sincerest condolences to Dan DeLong, the XCOR and Agile families for the great loss of Loretta Jackson Delong. She was a pioneer from the start, as she knew from the time she was twelve that she would build and fly spaceships. Through her life's journey, she repeatedly demonstrated rigor and grit, and she will be missed. The loss hits home particularly at Tau Zero because Aleta, as she was known to her friends, was a co-founder of XCOR, where she worked closely with co-founder and former CEO Jeff Greason, who is now chairman of the Tau Zero Foundation board. She would go on to collaborate with Greason again in the creation of Agile Aero, a Midland, TX-based startup targeting rapid design and prototyping techniques for space launch, hypersonic vehicles, and innovative aircraft. Greason is CEO of...

Up Close at Alpha Centauri

by Paul Gilster | Dec 6, 2016 | Missions | 20 Comments

In early December the Harvard-Smithsonian Center for Astrophysics offered as part of its fall colloquium series a talk by Harvard's Avi Loeb, fortunately captured on YouTube as Project Starshot: Visiting the Nearest Star Within Our Lifetime. We've looked at Breakthrough Starshot in many posts on Centauri Dreams, including my reports from the last set of meetings in Palo Alto, but for those new to the concept of using a laser array to send small, instrumented sails to the Alpha Centauri stars, this video is a fine introduction. You'll recall that yesterday I talked about Robert Austin's futuristic Asteroid Belt Astronomical Telescope, with an illustration of what such an instrument might see of the exoplanet Gliese 832c. If Starshot can achieve its goals, it will be able to make out continent sized features on the surface of Proxima b, or perhaps a planet around Centauri A or B. It would achieve, in other words, what it would take a near-Earth space-based telescope 300 kilometers wide...

Thought Experiment: The Asteroid Belt Astronomical Telescope

by Paul Gilster | Dec 5, 2016 | Deep Sky Astronomy & Telescopes | 33 Comments

Could laser light be used to shape and polish an asteroid to high optical standards? That's the question raised in an imaginative essay in Physics Today that posits the creation, a century from now, of the Asteroid Belt Astronomical Telescope (ABAT). It's science fiction today, part of the series of speculations that the magazine has been running to explore possible futures, but what a concept for an SF novel, and perhaps someday real astronomy (thanks to Centauri Dreams reader Klaus Seidensticker for sending me the link). Author Robert Austin (Florida Polytechnic University) creates a backstory involving a "self-described over-the-hill assistant professor at Purdue University" who uses a research grant to polish a 1-centimeter sphere of pyrolytic carbon magnetically levitated in a vacuum. He achieves the needed flat optical surface along with a reflective hemispherical 'bump' on the object's backside that can be used to reorient the mirror by photon pressure. Soon the idea of using...

Shifting Perspectives on Pluto’s ‘Heart’

by Paul Gilster | Dec 2, 2016 | Outer Solar System | 9 Comments

One of the great pleasures of doing this site is watching researchers matching ideas in peer-reviewed papers. A paper can meet the highest standards for publication but still present an argument that subsequent researchers question, igniting a new round of debate. Trying to get at the heart of a scientific question requires patience, but it's also as absorbing as a chess game, as witness the continuing debate over the history and significance of Pluto's Sputnik Planitia. And in this case, we have a researcher working both sides of the controversy. Resembling a polar ice cap, Sputnik Planitia is about 1000 kilometers across, and is centered on a latitude of 25 degrees north and a longitude of 175 degrees. Moreover, it is directly opposite the side of Pluto that always faces Charon, the result of tidal lock. Two weeks ago we looked at the possibility that this western lobe of Pluto's 'heart,' a deep basin filled with frozen gases like nitrogen, carbon dioxide and methane, was the...

Visualizing the Alien: A Hollywood Conundrum

by Paul Gilster | Dec 1, 2016 | Culture and Society | 90 Comments

Aliens used to look more or less like humans in the films of the 1950s. Think Michael Rennie in The Day the Earth Stood Still (1951), a polished alien presence if there ever was one. We got humanoid aliens with strange powers or technologies, like Jeff Morrow playing Exeter in This Island Earth (1955) -- a prominent forehead and strange hair is all it takes. Even James Arness' vegetable man (The Thing from Another World, 1951), although seen but briefly and on a rampage, is recognizably humanoid. Image: James Arness makes his appearance in Howard Hawks' The Thing from Another World. I watched all those films and many other SF movies besides when I was growing up, almost all on TV re-runs. Later, special effects would vastly improve, and non-humanoid aliens thrived, my favorite being the repulsive title character in Ridley Scott's Alien (1979), so dramatically visualized by Swiss surrealist Hans Rudolf Giger. Now we see aliens in all shapes and sizes, from the many-toothed predator...

Tight Constraints on Orbit of a Transiting ‘Super-Earth’

by Paul Gilster | Nov 30, 2016 | Exoplanetary Science | 10 Comments

The super-Earth K2-3d orbits a red dwarf star in the constellation Leo, some 150 light years from Earth. The outermost of three planets discovered in the system, K2-3d was found in the K2 phase of the Kepler mission (K2 Second Light), following the issues with the spacecraft's reaction wheels that led to the end of the primary mission. Interestingly, while the planet is large (with a radius 1.5 times that of Earth), its density is high and indicative of a solid surface (we can measure the radius of K2-3d by studying the transit light curve, while radial velocity methods yield the planet's mass, allowing astronomers to calculate its density). Given the right atmospheric parameters, liquid water could exist here, although most models show a tidally locked world receiving too much solar flux (1.4 times that of the Earth) to make habitable conditions likely. With an orbital period of 45 days, K2-3d's transits are interesting because the planet is close enough to be a useful candidate for...

Saturn: ‘Grazing’ the Rings

by Paul Gilster | Nov 29, 2016 | Outer Solar System | 24 Comments

What the Jet Propulsion Laboratory refers to as 'the first phase of the mission's dramatic endgame' begins tomorrow for the Cassini Saturn orbiter. Having given us an ocean within Enceladus and numerous images of Titan's lakes and seas (not to mention ring imagery of spectacular beauty), Cassini now enters a phase in which it encounters the rings in a new way, diving past their outer edge every seven days in a series of 20 passes. The spacecraft will be in an elliptical orbit inclined some 60 degrees from the planet's ring plane. "We're calling this phase of the mission Cassini's Ring-Grazing Orbits, because we'll be skimming past the outer edge of the rings," said Linda Spilker, Cassini project scientist (JPL). "In addition, we have two instruments that can sample particles and gases as we cross the ring plane, so in a sense Cassini is also 'grazing' on the rings." Image: Cassini crosses Saturn's F ring once on each of its 20 Ring-Grazing Orbits, shown here in tan and lasting from...

Freelancing an Interstellar Message

by Paul Gilster | Nov 28, 2016 | Astrobiology and SETI | 97 Comments

The problem in sending intentional signals to the stars isn't technology. It's our lack of consensus. Having widespread buy-in on whether, why and how to add an 'active' component to SETI is deeply polarizing, at least on the surface. But dig deeper: While there are those who think we should send signals about ourselves to other stars, the opposition doesn't necessarily disagree provided appropriate discussion and consultation be achieved first. I'm with the latter camp and always have been. To me, this is as sensible as coming up with an environmental impact statement and debating it. We need to be thinking about the issues involved here because as technologies get more powerful, individual actors will be able to send messages that would formerly have been in the province of governments. As I mentioned last week, such issues are not new to science, as witness the debate over recombinant DNA research that eventually led to multidisciplinary agreement -- for more on this, see Asilomar...

The Starship in our Future

by Paul Gilster | Nov 23, 2016 | Culture and Society | 133 Comments

The relentless expansion implicit in the Kardashev scale ranks civilizations according to their use of power, with the notion that there is an upward movement from exploiting the energy resources of a planet to the entire home star and then on to the galaxy (Type III). Hence the interest in trying to observe civilizations that operate on such colossal scales. Surely a Kardashev Type III culture would, in its manipulation of such titanic energies, cast a signature that would be observable even by a relatively lowly Type .7 civilization like ours. So far we see no signs of Type III civilizations, though early searches through our astronomical data continue (see G-HAT: Searching For Kardashev Type III, for example, which gets into the Glimpsing Heat from Alien Technologies work at Penn State). In Earth in Human Hands, David Grinspoon relates the question to our own survival challenges as we deal with the so-called Anthropocene, a time when our technologies are increasingly affecting our...

Looking for ‘Technosignatures’

by Paul Gilster | Nov 22, 2016 | Astrobiology and SETI | 41 Comments

We speculated yesterday that categorizing civilizations on the basis of their power use may not be a given, though it is the basis of the familiar Kardashev types. It seems natural to a rapidly changing technological society like ours that the trend is always upward, a clear path toward harnessing the energies of the home planet, then the Sun, then the galaxy. That this may not be the case seems to go against the grain of ‘Dysonian SETI,’ which looks for, among other things, artifacts as large as Dyson spheres and other astro-engineering projects on massive scales. Or maybe not, for some engineering involving adjustments to planetary environments may well produce observables. We just have to be aware of the range of possibilities here, and recognize our own limitations in trying to figure them out. For we’ve learned something else from technology, and that is that its components grow ever smaller. Working at nanotech scales to create things from the ground up isn’t beyond the...

SETI in the Anthropocene

by Paul Gilster | Nov 21, 2016 | Astrobiology and SETI | 78 Comments

Have we, as some have argued, entered a new 'age of humanity,' the so-called Anthropocene? The notion is controversial in many quarters, but it addresses the growing concern about our human influence on the Earth and the nature of planetary change. David Grinspoon's new book Earth in Human Hands (Grand Central Publishing, 2016) has much to say about the Anthropocene, but as anyone who has read the work of this canny scientist knows, he's not one to let facile assumptions get by unquestioned. For if the activity of humans is now emerging as an agent of geological change, then we are discussing our civilization in the same terms we talk about planetary forces like tectonic movement and the carbon cycle. This makes us major players whose effects we can begin to chart in terms of the effects of our technology on Earth's living systems. If the Anthropocene is happening, it presents us not only with danger but the prospect of a long-term future. And its implications take in not just our...

Nearby Super-Earth at GJ 536

by Paul Gilster | Nov 18, 2016 | Exoplanetary Science | 2 Comments

The discovery of a super-Earth of about 5 Earth masses orbiting the star GJ 536 is a helpful addition to our catalog of nearby red dwarf planets. About 33 light years out, GJ 536b orbits its primary at a distance of 0.06661 AU, an 8.7 day orbit that is too close to be in the habitable zone. But its very proximity to the star implies the possibility of a transit, which could pay big dividends in spectroscopic studies of its atmosphere. Follow-ups as soon as next year should tell us whether it does in fact transit. The work comes out of the Geneva Observatory, working with researchers in France and Portugal, and involves data from the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph on the European Southern Observatory’s 3.6 meter telescope at La Silla (Chile). And it has me thinking about the problems and benefits of red dwarf studies. For one thing, astronomers can use nearby M-dwarfs for exoplanet detection because the low mass of the star offers up a robust radial...

Fast Radio Bursts as Cosmological Probes

by Paul Gilster | Nov 17, 2016 | Deep Sky Astronomy & Telescopes | 5 Comments

One of the brightest Fast Radio Bursts seen since the phenomena were first detected in 2001 has been observed by the Parkes radio telescope in New South Wales. Maybe it should come as no surprise that Parkes was involved, given that most of the 18 FRBs that have so far been detected have been found there, including the so-called 'Lorimer' burst of 2001, which launched researchers' interest in these mysterious processes. This one is thought to be particularly helpful in constraining magnetic fields and gases in intergalactic space, for observed distortions produced by an FRB's travel yield data about the medium. Ryan Shannon (ICRAR-Curtin University), a co-author of the paper, refers to the region between the galaxies as the 'cosmic web,' a region of all but invisible gases and plasma particles that is extremely hard to map. FRBs are short but intense pulses of radio waves -- each lasts about a millisecond -- that are usually discovered by accident, and no two look the same. Radio...

Pluto: Sputnik Planitia Gives Credence to Possible Ocean

by Paul Gilster | Nov 16, 2016 | Outer Solar System | 18 Comments

We've been looking at the idea of an ocean beneath Pluto's icy surface for some time, including interesting work on the thermal evolution of the dwarf planet's ice shell from Guillaume Robuchon and Francis Nimmo (University of California at Santa Cruz). Back in 2011, The Case for Pluto's Ocean looked at their view that the stretching of Pluto's surface would have clear implications for an ocean kept warm by radioactive decay in the interior. Now Nimmo is back with a post-New Horizons analysis that also points to an ocean. The key here is Sputnik Planitia, forming part of the heart-shaped feature that was so distinctive during the flyby -- think of Sputnik Planitia as the heart's 'left ventricle.' The impact basin here is aligned almost exactly opposite from Charon. We learn in Nimmo's paper in Nature that there is only a 5 percent chance that the feature's alignment with Pluto's tidal axis is by coincidence. To Nimmo and colleagues, the alignment is a dead giveaway that extra mass in...

Project Blue: Imaging Alpha Centauri Planets

by Paul Gilster | Nov 15, 2016 | Exoplanetary Science | 28 Comments

We know about an extremely interesting planet around Proxima Centauri, and there are even plans afoot (Breakthrough Starshot) to get probes into the Alpha Centauri system later in this century. But last April, when Breakthrough Initiatives held a conference at Stanford to talk about this and numerous other matters, the question of what we could see came up. For in Alpha Centauri, we're dealing with three stars that are closer to us than any other. If there are planets around Centauri A and/or Centauri B, are there ways we could image them? This gets interesting in the context of Project Blue, a consortium of space organizations looking into exoplanetary imaging technologies. This morning Project Blue drew on the work of some of those present at Stanford, launching a campaign to fund a telescope that could obtain the first image of an Earth-like planet outside our Solar System, perhaps by as early as the end of the decade. The idea here is to ignite a Kickstarter effort aimed at...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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