Nearby Twin Research Articles

Mediated Futures in Anesthetic Space

Media are intimately connected to the future. They are simultaneously posited as encouraging speculation and foreclosing futures. Through an examination of the “canal craze” at the turn of the twentieth century in which the telescopic lens was believed to reveal Earth’s future by way of focusing in on its nearby twin, this paper moves beyond notions of open and closed visions by considering the function of noise in mediated futures. That the canals were an effect of dust, as both elemental medium and noise, encourages broader questions concerning how futures pivot on what lies at the blurred edges of media and beyond rather than on what media make clearly visible. This paper argues for an analytic of futures, both potential and prescribed, situated in the anesthetic fields of media ecologies, spaces of speculation, contestation, and the non-dyadic play of visibility-opacity-invisibility.

A Comparison of Distant and Nearby Solar Twins

Properties of solar twins at kiloparsec distances from the local standard of rest are compared to solar twins within 100 pc of the Sun. They have a velocity distribution closely similar to that of the nearby twins in addition to closely matching T eff, and [Fe/H]. The new twins are a kpc distant from Earth, and closer to the Galactic center. Additionally, they may be significantly older than nearby twins, and thus are useful for spectroscopic comparison with solar twins, in the search for fine structure constant variation.

Testing the role of AGN on the star formation and metal enrichment of ‘twin galaxies’

ABSTRACT We explore the effect of AGN activity on the star formation history of galaxies by analysing the stellar population properties of 10 pairs of nearby twin galaxies – selected as being visually similar except for the presence of an AGN. The selection of such twin samples represents a method to study AGN feedback, as recently proposed by del Moral Castro et al. We use integral field unit (IFU) data from CALIFA, stacked within three fixed apertures. AGN galaxies in a twin pair suggest more evolved stellar populations than their non-AGN counterpart 90 per cent of the time, regardless of aperture size. A comparison with a large sample from SDSS confirms that most twins are representative of the general population, but in each twin the differences between twin members is significant. A set of targeted line strengths reveal the AGN member of a twin pair is older and more metal-rich than the non-AGN galaxy, suggesting AGN galaxies in our sample may either have an earlier formation time or follow a different star formation and chemical enrichment history. These results are discussed within two simple, contrasting hypotheses for the role played by AGN in galaxy evolution, which can be tested in the future at a greater detail with the use of larger data sets.

Experimental and numerical assessment of cool-roof impact on thermal and energy performance of a school building in Greece

This paper presents an investigation of cool-roof impacts on thermal and energy performance of a School building located in Athens, Greece. The research work refers to a month recording of thermal performance indicators (TPIs) in selected classrooms, namely indoor air- roof- and ceiling surface- temperature. Thermal inspections also included roof thermal-camera scanning and reflectance measurements of exterior building surfaces. Thermal impacts were assessed in terms of comparisons of TPIs with the ones obtained by the same procedure in a nearby twin building. The impact of the cool roof on building energy performance and thermal comfort was assessed through dynamic energy simulations. Model calibration is achieved through comparisons of simulated indoor air temperature with the measured one in both the ex-ante and ex-post condition. Two summer-conditioning cases were analyzed, namely “ceiling fans with no cooling systems” (actual condition) and “air-conditioning split units with no ventilation systems”. For the building block below the cool roof it was found that: in the former case, the energy consumption for ventilation is reduced by at least 25% with an up to 3% increase of comfort operating hours, at the expense of a 12% heating penalty in winter. In the latter case, the energy consumption for cooling is reduced by at least 18% with a similar increase of comfort hours, compensating energy-consumption increase for heating in winter. It is concluded that the cool roof is an efficient solution for School buildings in warm climates as it improves summer thermal comfort and ensures annual energy savings when heat pumps are used for cooling purposes.

Interaction between oxygen interstitials and deformation twins in alpha-titanium

Twinning is an important deformation mechanism in many hexagonal close packed metals, including α-titanium (Ti) alloys. However, the mechanisms for twin nucleation, growth, and interaction with other defects are not completely understood. In this study we interrogate the behavior of oxygen (O) interstitials near a (101¯2) twin boundary using a combination of density functional theory (DFT) and modified embedded atom method (MEAM) calculations. The presence of the twin boundary significantly affects both interstitial formation energy as well as the activation barriers for diffusion between sites. We demonstrate that a tetrahedral interstitial is stable in the twin boundary, despite being unstable in bulk Ti, while the formation energies of the octahedral, hexahedral, and crowdion interstitials are all modified by a nearby twin. Further, the activation barriers for diffusion in the region near the twin are uniformly lower than in the bulk. An atom diffusing across the twin boundary moves through several paths with peak energies more than 0.3 eV lower than for comparable diffusion far from the twin, suggesting that the (101¯2) twin is a fast diffusion pathway and movement of oxygen interstitials across the twin during twin growth is possible.

Nucleation and propagation of {101¯2} twins in AZ31 magnesium alloy

Abstract Nucleation and propagation of tensile twins in magnesium alloy AZ31 are investigated for a large number of twins at an early stage of their development. High-resolution electron backscatter diffraction (HREBSD) techniques are employed to give additional insights. Correlations with grain orientation, boundary misorientation and active slip systems are observed in the region of twins that arise at grain boundaries. Two types of twin are identified: (1) slip-assisted twins that nucleate at grain boundaries with no apparent influence from nearby twins, and (2) twin-assisted twins that result from twins propagating across a grain boundary. Twinning occurs in “hard” grains that cannot accommodate necessary contraction via 〈a〉-type slip. Slip assisted twins nucleate at high-angle boundaries. Twin-assisted twinning occurs at low-angle boundaries. The distributions of grain boundary misorientation associated with each type of twin nucleation are mapped, and a strong correlation between Schmid factor and the emerging twin variant is highlighted.

Giant telescope hits a raw nerve for Hawaiians

Kea talks about the Thirty Meter Telescope (TMT) project. With a light-collecting mirror nine times the area of the ones on the nearby twin telescopes--currently the world's most powerful--the TMT will revolutionize the search for Earth-like worlds around other stars and peer to the very edge of the visible universe. The TMT may feel like the final straw for a people who have been treated shabbily in the past. Their resources were exploited by Westerners, and then a US-backed coup in 1893 overthrew the Hawaiians' last queen, Lili'uokalani, leading to US annexation of the islands. Given that history, it's perhaps not so surprising that native Hawaiians are rallying against the mountain's largest construction project to date. They also insist that the TMT does not comply with environmental regulations, a charge that forms the basis for the legal challenge to the project.

THE FUTURE OF THE SUN: AN EVOLVED SOLAR TWIN REVEALED BY CoRoT

The question of whether the Sun is peculiar within the class of solar-type stars has been the subject of active investigation over the past three decades. Although several solar twins have been found with stellar parameters similar to those of the Sun (albeit in a range of Li abundances and with somewhat different compositions), their rotation periods are unknown, except for 18 Sco, which is younger than the Sun and with a rotation period shorter than solar. It is difficult to obtain rotation periods for stars of solar age from ground-based observations, as a low activity level imply a shallow rotational modulation of their light curves. CoRoT has provided space-based long time series from which the rotation periods of solar twins as old as the Sun could be estimated. Based on high S/N high resolution spectroscopic observations gathered at the Subaru Telescope, we show that the star CoRoT ID 102684698 (CoRoT Sol 1) is a somewhat evolved solar twin with a low Li abundance. Its rotation period is 29 +- 5 days, compatible with its age (6.7 Gyr) and low lithium content A(Li) < 0.85 dex. Interestingly, our CoRoT solar twin seems to have enhanced abundances of the refractory elements with respect to the Sun, a typical characteristic of most nearby twins. With a magnitude V ~14.1, ID 102684698 is the first solar twin revealed by CoRoT, the farthest field solar twin so far known, and the only solar twin older than the Sun for which a rotation period has been determined.

Dwarf galaxies orbit Andromeda in a surprisingly thin plane

The Milky Way’s nearby twin is a good place to look for evidence of how galaxies form.The Milky Way’s nearby twin is a good place to look for evidence of how galaxies form.

Dwarf galaxies coherently orbit Andromeda

The Milky Way's nearby twin is a good place to study galaxy formation. The Milky Way's nearby twin is a good place to study galaxy formation.

The ring nebula around the blue supergiant SBW1: pre-explosion snapshot of an SN 1987A twin★†

SBW1 is a B supergiant surrounded by a ring nebula that is a nearby twin of SN 1987A. We present images and spectra of SBW1 obtained with HST, Spitzer, and Gemini South. HST images of SBW1 do not exhibit long Rayleigh-Taylor fingers, which are presumed to cause the hotspots in the SN1987A ring, but instead show a geometrically thin clumpy ring. The radial mass distribution and size scales of inhomogeneities in SBW1's ring closely resemble those in the SN1987A ring, but the more complete disk expected to reside at the base of the RT fingers is absent. This structure may explain why portions of the SN1987A ring between the hotspots have not yet brightened after more than 15 years. The model we suggest does not require a fast wind colliding with a previous red supergiant wind. More surprisingly, images of SBW1 also reveal diffuse emission filling the interior of the ring in H-alpha and thermal-IR emission; 190K dust dominates the 8-20 micron luminosity (but contains only 1e-5Msun). Cooler (85K dust resides in the equatorial ring itself (dust mass of 5e-3Msun). Diffuse emission extends inward to 1 arcsecond from the central star, where a paucity of emission suggests an inner hole excavated by the wind. We propose that diffuse emission inside the ring arises from an ionized flow of material photoevaporated from the dense ring, and it prevents the supergiant wind from advancing in the equator. This inner emission could correspond to a structure hypothesized to reside around SN1987A that was never directly detected. We suggest that photoionization can play an important dynamical role in shaping the ring nebula, and we speculate that this might help explain the origin of the polar rings around SN1987A. abridged.

Venus: Not evil, jus t a bit unfortunate

The Venus Express mission, currently orbiting Earth's nearest planetary neighbour, has just had its mission extended until the end of 2012 by the European Space Agency (ESA). In December 2010 it will be joined by the Japanese Venus Climate Orbiter, which has similar goals of understanding the atmosphere and climate. In this article Fred Taylor looks at what has been learned so far and what remains mysterious about our nearby twin, with its torrid weather and its global warming issues.

Venus Express mission

Venus Express is well and healthy and has now been providing exciting new data from Venus, our nearby twin planet, for over 2 years. Many of the new results are presented and discussed in the subsequent papers in this special section. The overall scientific objective of Venus Express is to carry out a detailed study of the atmosphere of Venus, including the interaction of the upper atmosphere with the solar wind and the interaction of the lowest part of the atmosphere with the surface of the planet. In addition, the plasma environment and magnetic fields as well as some aspects of the surface of the planet are addressed. For the first time, investigations make systematic use of the transparent infrared spectral windows in order to probe the atmosphere in four dimensions: three spatial dimensions plus time. The spacecraft design is taken from Mars Express with some modifications necessary owing to the specific environment around Venus. The payload is composed of three spectrometers, a camera, a magnetometer, an instrument for detecting energetic particles, and a radio science package. The orbit is polar and highly elliptic, with a pericenter altitude of about 200 km over the northern polar region and an apocenter altitude of 66,000 km. Presently, the coverage of the southern hemisphere is very good, but important gaps still do exist. The coverage of the northern hemisphere is much less dense. Venus Express is a part of the European Space Agency's program for the exploration of the inner solar system, which includes missions to study the Sun, Mercury, Venus, the Moon, Mars, and comets and asteroids.

Discovery of a Nearby Twin of SN 1987A's Nebula around the Luminous Blue Variable HD 168625: Was Sk -69 202 an LBV?

Some core-collapse supernovae show clear signs of interaction with dense circumstellar material that often appears to be non-spherical. Circumstellar nebulae around supernova progenitors provide clues to the origin of that asymmetry in immediate pre-supernova evolution. Here I discuss outstanding questions about the formation of the ring nebula around SN1987A and some implications of similar ring nebulae around Galactic B supergiants. Several clues hint that SN1987A's nebula may have been ejected in an LBV-like event, rather than through interacting winds in a transition from a red supergiant to a blue supergiant.