Astronomy posts
- January 16, 2010
- 03:15 AM
- 1,430 views
The Moon, Where helium-3 from the sun is
by Alexander in The Astronomist.
Moon is a 2009 science fiction film about astronaut Sam Bell who is a solitary miner on the moon. When Helium and fusion was mentioned at the beginning of the film I was delighted that they had based the story on a kernel of science. The energy source they are gathering from the moon is Helium-3. Helium-3 is a light isotope of helium with two protons and one neutron which is suitable as a fusion fuel. I have done some research into the literature to determine just how feasible this 3He min........ Read more »
FA, W., & JIN, Y. (2007) Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer. Icarus, 190(1), 15-23. DOI: 10.1016/j.icarus.2007.03.014
Heber, V., Baur, H., & Wieler, R. (2003) Helium in Lunar Samples Analyzed by High‐Resolution Stepwise Etching: Implications for the Temporal Constancy of Solar Wind Isotopic Composition. The Astrophysical Journal, 597(1), 602-614. DOI: 10.1086/378402
- January 12, 2010
- 06:08 AM
- 614 views
A new, bigger kind of boom
by Niall in we are all in the gutter
Supernovae are exploding stars. Most are caused either by an exploding white dwarf or a massive star with an iron core which collapses. There is however a third possibility........ Read more »
Gal-Yam A, Mazzali P, Ofek EO, Nugent PE, Kulkarni SR, Kasliwal MM, Quimby RM, Filippenko AV, Cenko SB, Chornock R.... (2009) Supernova 2007bi as a pair-instability explosion. Nature, 462(7273), 624-7. PMID: 19956255
- January 7, 2010
- 01:10 PM
- 594 views
Even When Scientists are Wrong, Creationists Still Aren't Right
by Jon Voisey in Angry Astronomer
New evidence has shown the most commonly given age of the solar system is wrong.The equations used to derive the age of it from radiometric dating of numerous isotopes was fundamentally flawed because it assumed that the ratio of certain isotopes was the same. Detailed new measurements have shown it's not.This "implies substantial uncertainties in the ages previously determined by Pb-Pb dating". So astronomers have had to recalculate the age of the solar system given this new information.The old........ Read more »
Brennecka, G., Weyer, S., Wadhwa, M., Janney, P., Zipfel, J., & Anbar, A. (2009) 238U/235U Variations in Meteorites: Extant 247Cm and Implications for Pb-Pb Dating. Science. DOI: 10.1126/science.1180871
- January 6, 2010
- 07:52 AM
- 536 views
Astronomical Units
by Brian Koberlein in Upon Reflection
Figure 1: Aristarchus measured the angle between the Sun and the Moon when the moon was half full, then used trigonometry to measure the distance to the Sun. (Source: Wikipedia) In an earlier post I wrote about how astronomers can...... Read more »
Hirst, W. (1769) Account of Several Phaenomena Observed during the Ingress of Venus into the Solar Disc. By the Reverend W. Hirst, F. R. S. in a Letter to the Astronomer Royal. Philosophical Transactions (1683-1775), 59(1), 228-235. DOI: 10.1098/rstl.1769.0031
- January 4, 2010
- 09:17 AM
- 1,988 views
alien expansion vs. the fermi paradox
by Greg Fish in weird things
The last time we tackled the Fermi paradox, we talked about what it means to be intelligent and how trying to speak to an intelligent species separated from us by an evolutionary gulf we can barely begin to describe in a meaningful way would probably leave us at a loss for words. This time, we’re [...]... Read more »
Jacob D. Haqq-Misra, & Seth D. Baum. (2009) The Sustainability Solution to the Fermi Paradox. J.Br.Interplanet.Soc.62:47-51, 2009. arXiv: 0906.0568v1
- January 4, 2010
- 03:07 AM
- 901 views
Space is very fine-grained
by Charles Daney in Science and Reason
It would take you a lot longer to hike a significant distance over very hilly terrain than it would over a completely flat plain. For much the same reason, it would take light longer to cover the same distance depending whether the space through which it moves does or doesn't have large "hills".But what does it mean for space to contain "hills"? And how large do "hills" need to be to make a difference?Consider the second question first. There's no natural place on Earth that is perfectly flat, o........ Read more »
Abdo, A., Ackermann, M., Ajello, M., Asano, K., Atwood, W., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Baring, M.... (2009) A limit on the variation of the speed of light arising from quantum gravity effects. Nature, 462(7271), 331-334. DOI: 10.1038/nature08574
- January 3, 2010
- 08:48 PM
- 2,095 views
In the News this month: first observational evidence of a new type of supernova
Stars the size and mass of our Sun end their lives by first expanding as , then shrinking to . Stars heavier than this however, come to a much more violent end.; For stars with masses between about 10 and 100 times that of the Sun, they continue in the core, until they run out of hydrogen. They then begin to fuse the helium nuclei together to form heavier elements such as carbon, nitrogen and oxygen. This carries on through the elements until iron, at which point the to form either a neutron s........ Read more »
Gal-Yam, A., Mazzali, P., Ofek, E., Nugent, P., Kulkarni, S., Kasliwal, M., Quimby, R., Filippenko, A., Cenko, S., Chornock, R.... (2009) Supernova 2007bi as a pair-instability explosion. Nature, 462(7273), 624-627. DOI: 10.1038/nature08579
- January 3, 2010
- 09:03 AM
- 527 views
In the News this month: the role of magnetic fields in GRBs
are highly energetic explosions which release enormous amounts of energy in just a few seconds. So-called because they were first discovered through their intense gamma-ray emission, these explosions can be seen across the visible universe. The exact nature of the jets which give rise to this emission is however, not certain. Different jet models predict very different properties of the magnetic fields present in the out-flowing material. Some models suggest that weak are present only locally ........ Read more »
Steele, I., Mundell, C., Smith, R., Kobayashi, S., & Guidorzi, C. (2009) Ten per cent polarized optical emission from GRB 090102. Nature, 462(7274), 767-769. DOI: 10.1038/nature08590
- January 3, 2010
- 08:27 AM
- 463 views
In the News this month: stellar canibalism in globular clusters
contain some of the oldest known stars.; Formed billions of years ago in the halos of what eventually become the galaxies we see today, globular clusters are roughly spherical collections of stars bound together by their own gravity. Our own Milky Way contains many such clusters, several of which were catalogued by in the 18th Century.While most of the stars in globular clusters have ages of 12 to 13 billion years, some of them appear to be much younger. Most stars in globular clusters are red........ Read more »
Ferraro, F., Beccari, G., Dalessandro, E., Lanzoni, B., Sills, A., Rood, R., Pecci, F., Karakas, A., Miocchi, P., & Bovinelli, S. (2009) Two distinct sequences of blue straggler stars in the globular cluster M 30. Nature, 462(7276), 1028-1031. DOI: 10.1038/nature08607
Mathieu, R., & Geller, A. (2009) A binary star fraction of 76 per cent and unusual orbit parameters for the blue stragglers of NGC 188. Nature, 462(7276), 1032-1035. DOI: 10.1038/nature08568
- December 29, 2009
- 02:37 PM
- 527 views
Point of View
by Brian Koberlein in Upon Reflection
Figure 1: Tycho's model of the cosmos. The solar system revolves around a fixed Earth, which is all surrounded by the celestial sphere of stars. (Source: Wikipedia) When you look at the night sky it is easy to imagine that...... Read more »
Miller-Jones, J., Jonker, P., Dhawan, V., Brisken, W., Rupen, M., Nelemans, G., & Gallo, E. (2009) THE FIRST ACCURATE PARALLAX DISTANCE TO A BLACK HOLE. The Astrophysical Journal, 706(2). DOI: 10.1088/0004-637X/706/2/L230
- December 25, 2009
- 07:40 AM
- 1,567 views
Laser guide stars as magnetometers
by sarah in One Small Step
In a nice piece of cross-pollination between disciplines, scientists have proposed a new method for measuring the Earth’s magnetic field strength using technology developed for ground-based observational astronomy. As it turns out, the laser guide stars astronomers use to sense the turbulence high up in the atmosphere can be used as cheap and efficient magnetometers.
To [...]... Read more »
J. M. Higbie, S. M. Rochester, B. Patton, R. Holzlöhner, D. Bonaccini Calia, & D. Budker. (2009) Magnetometry with Mesospheric Sodium. arXiv:0912.4310v1 [physics.atom-ph]. arXiv: 0912.4310v1
- December 19, 2009
- 08:44 AM
- 730 views
Non-Singular Black Holes
by Brian Koberlein in Upon Reflection
The basic model of a black hole can be summed up as follows: gravity wins. The root cause of all black holes—be they tiny primordial black holes, solar mass black holes, or supermassive galactic black holes—is gravity. Squeeze enough mass...... Read more »
Mbonye, M., & Kazanas, D. (2005) Nonsingular black hole model as a possible end product of gravitational collapse. Physical Review D, 72(2). DOI: 10.1103/PhysRevD.72.024016
- December 16, 2009
- 07:56 PM
- 1,912 views
say, how far away is that black hole?
by Greg Fish in weird things
Trying to pin down the distance between our planet and a nearby black hole is a very tricky business. By virtue of being pinpoints of self-gravitating energy, black holes are usually about the size of a big city and very hard to observe directly. Their small size is also what makes it so difficult to [...]... Read more »
J. C. A. Miller-Jones, P. G. Jonker, V. Dhawan, W. Brisken, M. P. Rupen, G. Nelemans, & E. Gallo. (2009) The first accurate parallax distance to a black hole. ApJ Letters. arXiv: 0910.5253v1
- December 14, 2009
- 11:41 AM
- 621 views
Beyond the Farthest Star
by Brian Koberlein in Upon Reflection
Figure 1: The Orion Constellation. (Source: APoD) When you look up into the night sky, you are seeing into the past. Cosmic distances are so vast that it takes time for light to travel them. Light from the closest star...... Read more »
Zhang, B. (2009) Astrophysics: Most distant cosmic blast seen. Nature, 461(7268), 1221-1223. DOI: 10.1038/4611221a
- December 9, 2009
- 06:12 PM
- 602 views
Could Kepler find something closer to home?
by Niall in we are all in the gutter
You might have heard about Kepler and NASA space mission to find planets around other stars. But recently this paper came out recently showing how it could be used to probe unknown distant reaches of our own solar system.... Read more »
Eran O. Ofek, & Ehud Nakar. (2009) Detectability of Oort cloud objects using Kepler. Submitted to ApJL. arXiv: 0912.0948v1
- December 5, 2009
- 11:55 AM
- 1,438 views
searching for the biggest stars in the cosmos
by Greg Fish in weird things
Like the overwhelming majority of stars in the universe, our sun will die with a whisper. When stars which tip the scales at more than 1.5 times the mass of our sun end their lives, they go out with a bang, leaving either a highly compressed core we know as a neutron star, or a collapsed gravitational well we call a black hole. But when stars that exceed an astonishing 130 solar masses run out of fuel, something even stranger happens. [...]... Read more »
Gal-Yam, A., Mazzali, P., Ofek, E., Nugent, P., Kulkarni, S., Kasliwal, M., Quimby, R., Filippenko, A., Cenko, S., Chornock, R.... (2009) Supernova 2007bi as a pair-instability explosion. Nature, 462(7273), 624-627. DOI: 10.1038/nature08579
- December 3, 2009
- 11:30 PM
- 1,218 views
Galaxy Zoo 2
by Alexander in The Astronomist.
Galaxy Zoo is the worlds largest astronomy collaboration with over a hundred thousand collaborators. I discuss the impetus, implementation and some of the results of the project.... Read more »
Anze Slosar, Kate Land, Steven Bamford, Chris Lintott, Dan Andreescu, Phil Murray, Robert Nichol, M. Jordan Raddick, Kevin Schawinski, Alex Szalay.... (2008) Galaxy Zoo: Chiral correlation function of galaxy spins. MNRAS, 392(1225). arXiv: 0809.0717v2
- December 2, 2009
- 09:03 AM
- 494 views
In the News this month: spectacular outflows in Orion
The constellation of Orion contains some massive complex regions of star formation, the most obvious of which is the , M42, located in Orion's sword. Through an optical telescope you can see a large glowing cloud of gas illuminated by a cluster of young, hot stars. But behind this cloud, hidden from view, lies another cluster of proto-stars, clumps of gas still collapsing under gravity in the process of forming stars. As ordinary light cannot penetrate through the gas, other parts of the el........ Read more »
L. D. Matthews, L. J. Greenhill, C. Goddi, C. J. Chandler, E. M. L. Humphreys, & M. Kunz. (2010) A Feature Movie of SiO Emission 20-100 AU from the Massive Young Stellar Object Orion Source I. Astrophysical Journal. arXiv: 0911.2473v1
- December 2, 2009
- 08:41 AM
- 514 views
In the News this month: a new way to search for exoplanets
are continuously being refined and are detecting ever smaller planets at greater and greater distances from their parent stars. But a team of astronomers have between planetary systems and lithium abundance that could provide a . Most methods of searching for planetary systems around other stars are best suited to finding large planets orbiting very close to their host stars. But what if there was a way to determine the likelihood of a particular star hosting planets, without actually detectin........ Read more »
Israelian, G., Mena, E., Santos, N., Sousa, S., Mayor, M., Udry, S., Cerdeña, C., Rebolo, R., & Randich, S. (2009) Enhanced lithium depletion in Sun-like stars with orbiting planets. Nature, 462(7270), 189-191. DOI: 10.1038/nature08483
- December 2, 2009
- 08:20 AM
- 455 views
In the News this month: mystery at the centre of Cas A
When massive stars explode as supernovae, they leave behind a dense, compact object: either a neutron star or a black hole depending on the mass of the original star. They also produce an expanding shell of debris known as a supernova remnant. Many of these shells are known in the Milky Way, but compact objects are not detected in all of them. One object in particular, the remnant known as has been expanding since its progenitor star exploded about 330 years ago, but for a long time no compact ........ Read more »
Ho, W., & Heinke, C. (2009) A neutron star with a carbon atmosphere in the Cassiopeia A supernova remnant. Nature, 462(7269), 71-73. DOI: 10.1038/nature08525
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