So what to do? Today, Duncan Forbes at Swinburne University in Australia and Pavel Kroup at the University of Bonn in Germany put forward a novel solution. They outline the various characteristics that astronomers think about when classifying galaxies.
These include factors such as the presence of stars, so gas clouds can't be defined as galaxies; being gravitationally bound, so materials that has been stripped away by another galaxy wouldn't count; whether the system is stable or not; whether it hosts a good variety of different types of star, which excludes globular clusters which contain only similar stars; and whether it is held together by dark matter, which many galaxies seem to be.
There are other factors too, of course. (Although they do not include the presence of a black hole at the centre of a galaxy as a defining characteristic , which is odd given the growing interest in the link between galactic evolutoin and black holes.)
Forbes and Kroup go on to suggest that the best way to achieve consensus is to crowdsource the problem. In other works, they want to use the wisdom of the crowd to determine what factors are important what aren't.
Contents contributed and discussions participated by Todd Suomela
SkyandTelescope.com - News from Sky & Telescope - A Megascope for Hawaii - 0 views
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TMT will also cost between 1 and 2 billion dollars when all is said and done. This is not quite at the scale of the world’s biggest science projects, like the Large Hadron Collider or the James Webb Space Telescope, but it’s getting there. In fact, TMT and other proposed observatories of this generation may end up being the biggest telescopes on Earth for all time because the funding required to go even larger would more logically be directed towards putting telescopes in orbit.
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Adaptive optics is a big part of TMT’s design. It will work both on Mauna Kea and Armazones, but astronomers expect it will work better on Mauna Kea. This is because the upper atmosphere—the part above the boundary layer—is somewhat less turbulent above Mauna Kea than it is above Armazones. Why? According to Racine it’s partly a function of latitude. Because Mauna Kea is nearer the equator it’s relatively unaffected by the jet streams that flow at higher latitutdes both north and south. Armazones’ upper atmosphere is a bit more turbulent in comparison and so somewhat harder for adaptive optics to deal with.
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Why and how did the Thirty Meter Telescope project decide to build at Mauna Kea?
Jupiter gets another cosmic punch, shows new bruise - Ars Technica - 0 views
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Over the weekend, Jupiter was apparently struck by an unknown object, probably a comet or an asteroid. The discovery was made by Anthony Wesley in Australia, an amateur astronomer well-known in both the amateur and professional astronomy communities.
Guest Post: Evalyn Gates on Cosmic Magnification (or - Invasion of the Giant Blue Space... - 0 views
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This is not just a pretty picture, however – the image packs a lot of scientific information. The authors extract the mass distribution in the cluster (which has implications for cosmological models), measure the mass-to-light ratio of the bright galaxy in the center of the cluster, and use the magnifying power of the lens to search for even more distant galaxies. The basic idea is to construct a model of the lens, starting with the cluster galaxies and a dark matter halo; then refine the model to reproduce the multiple images that are seen. Using this refined model it’s possible to predict the location of additional images of a given source, and to identify regions of high magnification that can then be examined for multiple images of other sources. Any additional images that are found can be used to further refine the model and so on.
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This galaxy has been lensed by the warp in spacetime created by the cluster. Light from the galaxy, which lies almost directly behind the center of the cluster but much farther away from us, travels along several curved paths through the cluster lens, producing multiple magnified images of the galaxy. The inset box shows a computer generated model of the unlensed source galaxy, enlarged by a factor of four so that the details, including the spiral arm structure, are visible. Without the lensing power of the cluster, we would see this galaxy as a single small blue smudge. In general, lensing will both magnify and distort (shear) images of a background source. This lens is fairly unique in that we see large but relatively intact images of the spiral galaxy, which implies that the mass distribution in the central region of the cluster must be nearly uniform.
Phoenix Lander Team: It Snows at Night on Mars | Universe Today - 0 views
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Phoenix landed at the north arctic region on Mars (68.22°N, 234.25°E) on May 25th, 2008. On Mars, this was just before the summer solstice. Phoenix operated for 5 months, and was able to observe conditions as the seasons changed from summer to winter, giving science teams an unprecedented look at the planet's changing weather patterns, including frost and precipitation.
ESO - ESO 24/09 - Astronomer's new guide to the galaxy: largest map of cold dust revealed - 0 views
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This new guide for astronomers, known as the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) shows the Milky Way in submillimetre-wavelength light (between infrared light and radio waves [1]). Images of the cosmos at these wavelengths are vital for studying the birthplaces of new stars and the structure of the crowded galactic core.
Particles Larger Than Galaxies Fill the Universe? - 0 views
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But over the roughly 13.7-billion-year lifetime of the cosmos, "relic" neutrinos have been stretched out by the expansion of the universe, enlarging the range in which each neutrino can exist.
[0904.0402] A thermodynamic basis for prebiotic amino acid synthesis and the nature of ... - 0 views
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Of the twenty amino acids used in proteins, ten were formed in Miller's atmospheric discharge experiments. The two other major proposed sources of prebiotic amino acid synthesis include formation in hydrothermal vents and delivery to Earth via meteorites. We combine observational and experimental data of amino acid frequencies formed by these diverse mechanisms and show that, regardless of the source, these ten early amino acids can be ranked in order of decreasing abundance in prebiotic contexts. This order can be predicted by thermodynamics. The relative abundances of the early amino acids were most likely reflected in the composition of the first proteins at the time the genetic code originated. The remaining amino acids were incorporated into proteins after pathways for their biochemical synthesis evolved. This is consistent with theories of the evolution of the genetic code by stepwise addition of new amino acids. These are hints that key aspects of early biochemistry may be universal.
Technology Review: Blogs: arXiv blog: Why ET's genetic code could be just like ours - 0 views
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"The combined actions of thermodynamics and subsequent natural selection suggest that the genetic code we observe on the Earth today may have significant features in common with life throughout the cosmos."
6dF Galaxy Survey - 0 views
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The 6dF Galaxy Survey (6dFGS) has mapped the nearby universe over nearly half the sky.
[0903.4849] Dark Matter Candidates - 0 views
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An overview is given of various dark matter candidates. Among the many suggestions given in the literature, axions, inert Higgs doublet, sterile neutrinos, supersymmetric particles and Kaluza-Klein particles are discussed.
Stuart Clark's Universe: The Sun Kings - 0 views
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Stuart Clark tells for the first time the full story behind Carrington's observations of a mysterious explosion on the surface of the Sun and how his brilliant insight-that the Sun's magnetism directly influences the Earth-helped to usher in the modern era of astronomy.
Todd Suomela
I'm a peripatetic wanderer through the awesome edifice of human knowledge, intent on self-development, reflection, and the synthesis of disparate ideas. I have always been, and will remain, a student. My interests are truly marvelous but this text box is too small to contain them.