2,688 research outputs found
Science Pipelines for the Square Kilometre Array
The Square Kilometre Array (SKA) will be both the largest radio telescope
ever constructed and the largest Big Data project in the known Universe. The
first phase of the project will generate on the order of 5 zettabytes of data
per year. A critical task for the SKA will be its ability to process data for
science, which will need to be conducted by science pipelines. Together with
polarization data from the LOFAR Multifrequency Snapshot Sky Survey (MSSS), we
have been developing a realistic SKA-like science pipeline that can handle the
large data volumes generated by LOFAR at 150 MHz. The pipeline uses task-based
parallelism to image, detect sources, and perform Faraday Tomography across the
entire LOFAR sky. The project thereby provides a unique opportunity to
contribute to the technological development of the SKA telescope, while
simultaneously enabling cutting-edge scientific results. In this paper, we
provide an update on current efforts to develop a science pipeline that can
enable tight constraints on the magnetised large-scale structure of the
Universe.Comment: Published in Galaxies, as part of a Special Issue on The Power of
Faraday Tomograph
Next Generation Very Large Array Memo No. 6, Science Working Group 1: The Cradle of Life
This paper discusses compelling science cases for a future long-baseline
interferometer operating at millimeter and centimeter wavelengths, like the
proposed Next Generation Vary Large Array (ngVLA). We report on the activities
of the Cradle of Life science working group, which focused on the formation of
low- and high-mass stars, the formation of planets and evolution of
protoplanetary disks, the physical and compositional study of Solar System
bodies, and the possible detection of radio signals from extraterrestrial
civilizations. We propose 19 scientific projects based on the current
specification of the ngVLA. Five of them are highlighted as possible Key
Science Projects: (1) Resolving the density structure and dynamics of the
youngest HII regions and high-mass protostellar jets, (2) Unveiling
binary/multiple protostars at higher resolution, (3) Mapping planet formation
regions in nearby disks on scales down to 1 AU, (4) Studying the formation of
complex molecules, and (5) Deep atmospheric mapping of giant planets in the
Solar System. For each of these projects, we discuss the scientific importance
and feasibility. The results presented here should be considered as the
beginning of a more in-depth analysis of the science enabled by such a
facility, and are by no means complete or exhaustive.Comment: 51 pages, 12 figures, 1 table. For more information visit
https://science.nrao.edu/futures/ngvl
Opportunities for asteroid retrieval missions
Asteroids and comets are of strategic importance for science in an effort to uncover the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The exploitation of these resources has long been discussed as a means to lower the cost of future space endeavours. In this chapter, we analyze the possibility of retrieving entire objects from accessible heliocentric orbits and moving them into the Earth’s neighbourhood. The asteroid retrieval transfers are sought from the continuum of low energy transfers enabled by the dynamics of invariant manifolds; specifically, the retrieval transfers target planar, vertical Lyapunov and halo orbit families associated with the collinear equilibrium points of the Sun-Earth Circular Restricted Three Body problem. The judicious use of these dynamical features provides the best opportunity to find extremely low energy transfers for asteroidal material. With the objective to minimise transfer costs, a global search of impulsive transfers connecting the unperturbed asteroid’s orbit with the stable manifold phase of the transfer is performed. A catalogue of asteroid retrieval opportunities of currently known NEOs is presented here. Despite the highly incomplete census of very small asteroids, the catalogue can already be populated with 12 different objects retrievable with less than 500 m/s of Δv. All, but one, of these objects have an expected size in the range that can be met by current propulsion technologies. Moreover, the methodology proposed represents a robust search for future retrieval candidates that can be automatically applied to a growing survey of NEOs
Galactic-scale macro-engineering: Looking for signs of other intelligent species, as an exercise in hope for our own
If we consider Big History as simply 'our' example of the process of cosmic
evolution playing out, then we can seek to broaden our view of our possible
fate as a species by asking questions about what paths or trajectories other
species' own versions of Big History might take or have taken. This paper
explores the broad outlines of possible scenarios for the evolution of
long-lived intelligent engineering species---scenarios which might have been
part of another species' own Big History story, or which may yet lie ahead in
our own distant future. A sufficiently long-lived engineering-oriented species
may decide to undertake a program of macro-engineering projects that might
eventually lead to a re-engineered galaxy so altered that its artificiality may
be detectable from Earth. We consider activities that lead ultimately to a
galactic structure consisting of a central inner core surrounded by a more
distant ring of stars separated by a relatively sparser 'gap', where star
systems and stellar materials may have been removed, 'lifted' or turned into
Dyson Spheres. When one looks to the sky, one finds that such galaxies do
indeed exist---including the beautiful ringed galaxy known as 'Hoag's Object'
(PGC 54559) in the constellation Serpens. This leads us to pose the question:
Is Hoag's Object an example of galaxy-scale macro-engineering? And this
suggests a program of possible observational activities and theoretical
explorations, several of which are presented here, that could be carried out in
order to begin to investigate this beguiling question.Comment: 17 pages. Published in: Teaching and Researching Big History:
Exploring a New Scholarly Field; L. Grinin, D. Baker, E. Quaedackers and A.
Korotayev (eds). Uchitel Publ House, Volgograd, Russia, 2014, Chapter 14, pp.
283-304. ISBN: 978-5-7057-4027-
Easily retrievable objects among the NEO population
Asteroids and comets are of strategic importance for science in an effort to understand the formation, evolution and composition of the Solar System. Near-Earth Objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The exploitation of these resources has long been discussed as a means to lower the cost of future space endeavours. In this paper, we consider the currently known NEO population and define a family of so-called Easily Retrievable Objects (EROs), objects that can be transported from accessible heliocentric orbits into the Earth’s neighbourhood at affordable costs. The asteroid retrieval transfers are sought from the continuum of low energy transfers enabled by the dynamics of invariant manifolds; specifically, the retrieval transfers target planar, vertical Lyapunov and halo orbit families associated with the collinear equilibrium points of the Sun-Earth Circular Restricted Three Body problem. The judicious use of these dynamical features provides the best opportunity to find extremely low energy Earth transfers for asteroid material. A catalogue of asteroid retrieval candidates is then presented. Despite the highly incomplete census of very small asteroids, the ERO catalogue can already be populated with 12 different objects retrievable with less than 500 m/s of Δv. Moreover, the approach proposed represents a robust search and ranking methodology for future retrieval candidates that can be automatically applied to the growing survey of NEOs
Advanced Aspects of the Galactic Habitability
Context. Astrobiological evolution of the Milky Way (or the shape of its
"astrobiological landscape") has emerged as one of the key research topics in
recent years. In order to build precise, quantitative models of the Galactic
habitability, we need to account for two opposing tendencies of life and
intelligence in the most general context: the tendency to spread to all
available ecological niches (conventionally dubbed "colonization") and the
tendency to succumb to various types of existential catastrophes
("catastrophism"). These evolutionary tendencies have become objects of study
in fields such as ecology, macroevolution, risk analysis, and futures studies,
while a serious astrobiological treatment has been lacking so far. Aims. Our
aim is to numerically investigate the dynamics of opposed processes of
expansion (panspermia, colonization) and extinction (catastrophic mechanisms)
of life in the Galaxy. Methods. We employ a new type of numerical simulation
based on 1D probabilistic cellular automaton with very high temporal
resolution, in order to study astrobiological dynamics. Results. While the
largest part of the examined parameter space shows very low habitability
values, as expected, the remaining part has some observationally appealing
features that imply, among other things, a reduction in the amount of
fine-tuning necessary for resolving the Fermi paradox. Conclusions. Advanced
aspects of Galactic habitability are amenable to precision studies using
massive parallel computer simulations. There are regions of parameter space
corresponding to a quasi-stationary state satisfying observable constraints and
possessing viable SETI targets.Comment: Language corrected version, to appear in Astronomy & astrophysic
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