In order to reach the nearest stars, we must first develop a propulsion technology that would take our robotic probes there in a reasonable time. Such propulsion technology has radically different requirements from conventional chemical rockets, because of the enormous distances that must be crossed. Surprisingly, many propulsion schemes for interstellar travel have been suggested and await only practical engineering solutions and the political will to make them a reality.
This is a result of the tremendous advances in astrophysics that have been made in recent decades and the perseverance and imagination of tenacious theoretical physicists. This book explores these different propulsion schemes - all based on current physics - and the challenges they present to physicists, engineers, and space exploration entrepreneurs.
This book will be helpful to anyone who really wants to understand the principles behind and likely future course of interstellar travel and who wants to recognizes the distinctions between pure fantasy such as Star Trek 's 'warp drive' and methods that are grounded in real physics and offer practical technological solutions for exploring the stars in the decades to come.
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We need something new. A much heavier, crewed spacecraft could reach the red planet in a month—about a fifth of the time predicted for the SLS. Photonic propulsion works by firing lasers at a reflective material like a solar sail.
Though the photons in the laser do not have mass, they do have energy and momentum, and they transfer a small amount of kinetic energy to the reflective surface when they bounce off. In the frictionless vacuum of space, the continued acceleration could hypothetically push a spacecraft to around 30 percent of the speed of light, the types of speeds we have achieved in partial accelerators. After launching a spacecraft into orbit with a conventional rocket, the probe could unfurl a light sail to be hit by powerful lasers on Earth. Our own Sun is visible to the upper right.
Risinger skysurvey. Not that Centauri B is an easy target. There are plenty of factors intrinsic to the star that can introduce jitter in these observations and thus render planet detection difficult. From the paper:. Their origin is associated with instrumental noise, stellar oscillation modes, granulation at the surface of the star, rotational activity, long-term activity induced by a magnetic cycle, the orbital motion of the binary composed of a Centauri A and B, light contamination from a Centauri A, and imprecise stellar coordinates.
Each of these factors had to be modeled and subtracted from the data. The team performed Monte Carlo simulations to check against the signal at 3. Notice how subtle these effects are and remember that they must be understood to get the real picture:. Therefore, no convection means no convective blueshift inside these regions, and so the spectrum of the integrated stellar surface will appear redshifted. Because a redshift means a measured positive radial velocity, a positive correlation between the magnetic cycle variation and the long-term radial velocity variation is then expected.
There was a sense of exhilaration in the air on Tuesday as the buzz around an Alpha Centauri planet built, and when the embargo was lifted, reports of the find filled the social media as the early articles began to appear online. Just how big a deal is Centauri B b?
A skeptic could point out that while finding an Earth-mass planet is significant, it must still be confirmed, and in any case, this is an Earth-mass planet that is nothing like a clement, habitable world. Then too, the level of investigation involved here was so intense that it may be years before we learn about other planets in this system, not to mention planets around Centauri A or Proxima. The main transit studies JWST will be able to undertake are: discovery of unseen planets, determining exoplanet properties like mass, radius, and physical structure, and characterizing exoplanet atmospheres to determine things like their temperature and weather.
If there are other planets in the Alpha Centauri system farther from the star, JWST may be able to detect them as well through imaging.source url
NASA Thinks There’s a Way to Get to Mars in 3 Days
Clearly the game is afoot. A confirmed Centauri B b would tell us that planet formation is indeed possible in the nearest stellar system to our own — this had by no means been obvious, and the debate over planet formation mechanisms in close binaries has been brisk. However, it requires an important investment in observation time, and thus only few targets can be observed over several years.
Recent statistical analyses and theoretical models of planetary formation suggest that low-mass rocky planets and especially Earth twins should be common. We are therefore confident that we are on the right path to the discovery of Earth analogues. Alpha Centauri is obviously a prime target for any future interstellar probe because it is so much closer than other stars. Space-based instrumentation will one day be able to tell us something about the larger Centauri B system, assuming other planets are present. The discovery of a terrestrial world in the habitable zone here would be a spur to exploration that could drive public interest and funding for increasingly sophisticated technologies.
Centauri B b is an exciting start to characterizing this fascinating system, a process that will demand time, patience, and effort just as rigorous as the Geneva team put in here. Well done to all involved! Lee puts the find into the broader context of exoplanet research as we turn our gaze to the nearest stars, those that would be the first targets of any future interstellar probes.
This Old Astronomy has given us a cosmological creation story, one which tells us we live in but one of innumerable galaxies, each populated with hundreds of billions of stars, all in an expanding, accelerating universe that began Somehow, life emerged and evolved here, eventually producing human beings, creatures with the intellectual capacity to wonder where they came from and the technological capability to determine where they will go.
Uniquely among the worlds in our solar system, the Earth has given birth to life that may before the Sun goes dim reach out to touch the stars. Perhaps, on other worlds circling other suns, other curious minds gaze at their night skies and wonder as we do whether they are alone. In this coming century, a New Astronomy is rising, one that focuses not on the edge of space and the beginning of time but on the nearest stars and the uncharted worlds they likely hold. It will be this New Astronomy, rather than the Old, that will at last complete the quest to place our existence on Earth within a cosmic context.
In a major leap forward in this enterprise, today a European planet-hunting team announced their discovery of an alien world about the same mass as Earth. But there is more to the story. There are two other stars in the system as well, the yellow Sun-like star Alpha Centauri A and the red dwarf star Proxima Centauri.
Astronomers began discovering exoplanets about two decades ago, finding at first a few per year. Since then, the pace of discovery has dramatically accelerated. Today there are more than confirmed exoplanets, and a single NASA mission, the Kepler spacecraft, has detected more than 2, additional candidates that await confirmation. The discovery of more Goldilocks worlds appears inevitable — statistics from the Kepler mission and other sources suggest that somewhere between ten to thirty percent of stars harbor potentially habitable planets.
Among the planet-hunters, the question is no longer whether life exists elsewhere in the universe, but rather how far removed the next-nearest living world might be. At a distance of just over 4. To reach Alpha Centauri B b, as this new world is called, would require a journey of some 25 trillion miles. For comparison, the next-nearest known exoplanet is a gas giant orbiting the orange star Epsilon Eridani, more than twice as far away.
With a probable surface temperature well above a thousand degrees Fahrenheit, Alpha Centauri B b is no Goldilocks world. Still, its presence is promising: Planets tend to come in packs, and some theorists had believed no planets at all could form in multi-star systems like Alpha Centauri, which are more common than singleton suns throughout our galaxy. It seems increasingly likely that small planets exist around most if not all stars, near and far alike, and that Alpha Centauri B may possess additional worlds further out in clement, habitable orbits, tantalizingly within reach.
Deep Space Propulsion: A Roadmap to Interstellar Flight (Astronomers' Universe) by Long, K. F
Looking out from Alpha Centauri B b and any other planets in that system, Cassiopeia would gain a sixth star, six times brighter than the other five, becoming not a W but a sinuous snake or a winding river. Image : Alpha Centauri as seen by the Cassini orbiter above the limb of Saturn. Despite its close proximity, as with nearly all other known exoplanets, Alpha Centauri B b is as yet unseen. It was detected indirectly, via a periodic centimeter-per-second wobble its orbit raises in the motions of its star, in a painstaking process that took four years of nightly monitoring and careful analysis.
Both of these discovery methods can constrain the most basic properties of a planet: its orbit, its mass, and perhaps its size and bulk composition. But neither can readily reveal whether or not any potentially habitable planet is actually a place much like Earth. The reflected planetary light would also contain spectroscopic signatures of atmospheric gases.
Carbon dioxide would suggest a rocky planet, and water vapor would hint at oceans or seas. Detecting oxygen and methane — gases produced on Earth by living things — would further suggest that the distant planet was not only habitable, but inhabited. To see the firefly, that overwhelming ten-billion-to-one background light must be suppressed. Amazingly, on paper and in laboratory studies, astronomers have already devised multiple ways to do exactly this for potentially Earth-like planets that may exist around nearby stars.
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Yet today NASA is not seriously funding any life-finding telescopes, and has no real plans to do so in the future. The agency instead is spread thin and lacking any unified direction, strapped for cash and struggling to avoid obsolescence while it maintains the International Space Station, builds a new fleet of rockets to replace the retired Space Shuttles, and completes the James Webb Space Telescope. Yet obsolescence is precisely what NASA will embrace if it fails to invest now in the next giant leap required for this New Astronomy.
Of all the scientific institutions and agencies upon this planet, at present NASA alone has the resources to build a telescope capable of directly imaging and characterizing any Earth-like planets around nearby stars. Unless it does so, as the list of potentially habitable planets grows long in years to come, all that shall grow along with it will be our ignorance of what those distant worlds are actually like and what may live upon them. Meanwhile powerful, influential Old Astronomy, which has revolutionized our understanding of the universe at its largest scales, is wary of the New, and at times has acted quite deliberately against it.
Alas, government-funded Big Science is too often a zero-sum game, one in which money that could go toward looking for life on exoplanets around nearby stars would be taken from cosmological efforts to study far-distant galactic clusters and the expansion of the universe. In a perfect world we would fully fund both quests simultaneously. But our world — with its economic instabilities, rising temperatures, growing populations, and plummeting biodiversity — seems to grow more imperfect by the day, in ways that no knowledge of dark energy or dark matter is likely to ever assuage.
The New Astronomy is different. We do not yet know whether planets like ours and creatures like us are in fact common or rare in the cosmos, but by trying to find out, we will unavoidably learn just how precious our planet truly is. Continuing with what promises to be a seriously interesting week in exoplanet studies, I want to home in this morning on PH1, a planet that reminds us how much the public has become involved in ongoing science thanks to the widespread distribution of computer power.
The volunteers — Kian Jek of San Francisco, California, and Robert Gagliano of Cottonwood, Arizona — were the first to spot the telltale lightcurve of a transit, which was then confirmed by astronomers using the Keck instruments at Mauna Kea Hawaii.
What the investigation uncovered was a gas giant about 6. But what really flags the attention is the fact that PH1 orbits within a four-star system. The planet is on a circumbinary orbit of two stars — with mass of 1. At about AU in the same system is a second binary pair orbiting the first. The inner pair comprise an eclipsing binary tagged KIC , located in the Kepler field and examined by the Planet Hunters duo using the first six quarters of publicly available Kepler data.
These planetary systems provide new boundary conditions for planet formation This ever increasing sample of dynamically extreme planetary systems will serve as unique and vital tests of proposed planetesimal formation models and core accretion theories….
Off in the distance, well beyond the planet orbit, resides a second pair of stars bound to the planetary system. PH1 was found serendipitously by Planet Hunters volunteers examining the light curves of the known Kepler eclipsing binaries. The discovery of PH1 highlights the potential of visual inspection through crowd sourcing to identify planet transits in eclipsing multistar systems, where the primary and secondary eclipses of host stars make detection challenging compared to planets with single host stars.
For more, see this Yale University news release. The paper is Schwamb et al. As Kepler continues to hunt, how can we move beyond its findings to learn more about terrestrial planets around much closer stars? Rather, there is a peak, followed by a falloff, with increasing distance from the parent star. The distribution curve for Earth-sized worlds shows a positive slope, so far. Only an extended Kepler mission will be able to determine the actual fraction of stars that have an Earth orbiting it. A low value for eta-Earth will mean that the search for Earth analogs in nearby solar systems will need to be pursued with vigor, and with multiple approaches.
Kepler, of course, is working with a large field of stars about light years away, the idea being to gather statistical information that will help us understand the broad trends of planet distribution. The Nearby Earth Astrometric Telescope has been proposed to the European Space Agency as a mission that could home in on nearby terrestrial planets in ways Kepler cannot. The idea here is to fly a pair of spacecraft separated by some 40 meters, providing the needed focal length to create high angular resolution.
One of the spacecraft carries a 1-meter mirror while the other is a detector probe that collects the focused light onto an array of CCDs. The goal is to detect Earth analogs within 50 light years, with an accuracy of 0. Says Horzempa:.
It will be able ascertain whether planets down to a mass of 1 Earth, or larger, orbit those stars. In addition, NEAT will be able to survey the solar systems discovered by Kepler, detecting giant planets that were missed by Kepler. The hope of the NEAT planners is to move beyond this experiment to a smallsat follow-up called micro-NEAT, which would put the formation flying algorithms through their paces, though at a separation of 12 rather than 40 meters.
Quite a lot of serious work could emerge from such a mission: Horzempa notes that micro-NEAT would be able to detect planets down to one Earth mass for our nearest neighbors, Alpha Centauri A and B. It would also be able to detect larger planets with a lower mass limit of 10 Earth masses around the 25 nearest stars. With funding for projects like DARWIN and Terrestrial Planet Finder in perpetual limbo, smaller missions that can advance the exoplanet hunt — and help us refine the value of eta-Earth — are the next priority. For more, see Mablet et al. The NEAT proposal summary is also available.
Since he has worked to catalyse the interstellar community through the organization of lectures, symposia, publications and design studies. The subject of Interstellar Studies derives its name from a set of special red cover issues of the Journal of the British Interplanetary Society , published between — This collection of papers represents a golden age of interstellar research.
Prior to this, the first technical paper addressing the interstellar challenge was published in the same journal in by Dr Les Shepherd. This can be considered the beginning of interstellar studies as an academic research subject.
Throughout the last 60 years many papers have been published addressing the science and technology associated with interstellar flight. Publications have also examined wider questions of social consequences, philosophical viewpoints and political or economic issues. This large body of work demonstrates that the interstellar challenge is one that engulfs a broad range of subjects and likely requires the application of a multitude of solution types.