Astronomy posts
- March 15, 2010
- 05:16 PM
- 24 views
a marauding star vs. our solar system
by Greg Fish in weird things
Imagine a speeding star plowing through the Oort Cloud surrounding our solar system and sending a stream of comets towards the Sun, a number of them smashing into Jupiter or diverted by the Jovian gravity into the inner solar system where the Earth could easily careen into them. The impacts could easily cause the kind [...]... Read more »
Bobylev, V. (2010) Searching for Stars Closely Encountering with the Solar System. Astronomy Letters, 2010 Vol. 36, No. 3. arXiv: 1003.2160v1
- March 12, 2010
- 03:01 AM
- 29 views
Galaxies are slowly running out of gas
by Charles Daney in Science and Reason
Galaxies are made of stars, and stars are made of... gas. So a large part of understanding how galaxies evolve and grow is understanding how much "gas" (literally, not "gasoline") is present in galaxies – but has not yet been incorporated in stars – at different periods in the history of the universe.What periods of the universe are most interesting in this regard? The answer is: periods somewhat less than the first half of the universe's existence since the time of the big bang, rou........ Read more »
Tacconi, L., Genzel, R., Neri, R., Cox, P., Cooper, M., Shapiro, K., Bolatto, A., Bouché, N., Bournaud, F., Burkert, A.... (2010) High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature, 463(7282), 781-784. DOI: 10.1038/nature08773
- March 7, 2010
- 05:04 AM
- 47 views
Gamma-ray bursts without the gamma rays?
by Charles Daney in Science and Reason
We discussed supernovae a bit in this recent post on gamma-ray bursts. There is now interesting new information on the connection between supernovae and gamma-ray bursts from two recently-described supernovae with atypical properties.Let's first review a little. Gamma-ray bursts (GRBs) are identified by detection of relatively brief (usually less than a few minutes) but highly energetic emissions of gamma rays. Although there's a great deal of diversity, most events fall into one of two categori........ Read more »
Soderberg, A., Chakraborti, S., Pignata, G., Chevalier, R., Chandra, P., Ray, A., Wieringa, M., Copete, A., Chaplin, V., Connaughton, V.... (2010) A relativistic type Ibc supernova without a detected γ-ray burst. Nature, 463(7280), 513-515. DOI: 10.1038/nature08714
Paragi, Z., Taylor, G., Kouveliotou, C., Granot, J., Ramirez-Ruiz, E., Bietenholz, M., van der Horst, A., Pidopryhora, Y., van Langevelde, H., Garrett, M.... (2010) A mildly relativistic radio jet from the otherwise normal type Ic supernova 2007gr. Nature, 463(7280), 516-518. DOI: 10.1038/nature08713
- March 4, 2010
- 06:43 PM
- 57 views
Will the Moon mess up a moon-base?
by Emma in we are all in the gutter
If we want to build a permanent base on the Moon – and the question of whether we ever will (or even should) remains very open – we need to have some idea of the effect the lunar environmental conditions will have on our equipment. There’s no point going to all [...]... Read more »
T. W. Murphy, Jr., E. G. Adelberger, J. B. R. Battat, C. D. Hoyle, R. J. McMillan, E. L. Michelsen, R. Samad, C. W. Stubbs, & H. E. Swanson. (2010) Long-term degradation of optical devices on the moon. Icarus. arXiv: 1003.0713v1
- March 4, 2010
- 04:20 PM
- 37 views
With a little help from our friends: Finding a home for E-ELT
by sarah in SarahAskew
ESO announced today that their Council have recommended Cerro Armazones in the Chilean Andes as the preferred site for their next generation optical/IR observatory, the 42-m European Extremely Large Telescope. The decision came in response to the delivery of a technical report by the organisation’s E-ELT Site Selection Advisory Committee, from which Armazones emerged as [...]... Read more »
M. Schoeck, S. Els, R. Riddle, W. Skidmore, T. Travouillon, R. Blum, E. Bustos, G. Chanan, S. G. Djorgovski, P. Gillett.... (2009) Thirty Meter Telescope Site Testing I: Overview. PASP. arXiv: 0904.1183v1
Skidmore, Warren, Els, Sebastian, Travouillon, Tony, Riddle, Reed, Schöck, Matthias, Bustos, Edison, Seguel, Juan, & Walker, David. (2009) Thirty Meter Telescope Site Testing V: Seeing and Isoplanatic Angle. PASP, 121(884), 1151-1166. info:/10.1086/644758
- March 4, 2010
- 03:44 AM
- 61 views
cold? what cold? it’s the uv rays that’ll kill you
by Greg Fish in weird things
It’s not that Mars is hostile to life as we know it, it’s just that even the toughest terrestrial microorganisms able to survive a big gamma ray burst from a nearby nuclear reactor die within ten minutes of exposure to a close simulation to the conditions on the red planet’s surface. That seems to be [...]... Read more »
Giuseppe Galletta; Giulio Bertoloni; Maurizio D'Alessandro. (2010) Bacterial survival in Martian conditions. Planetary and Space Science . arXiv: 1002.4077v1
- March 4, 2010
- 02:31 AM
- 45 views
In the News this month: emission from methane in the atmosphere of an extrasolar planet
In just fifteen years, have been discovered around stars other than the Sun using a variety of techniques. Even without the ability to directly image these other worlds, some of their properties can be determined. Most extra solar planets found so far are massive orbiting close to their parent stars, since these are the types of planets that the detection methods are most sensitive to. As develop and improve, astronomers are finding out more and more about these other worlds, including the co........ Read more »
Swain, M., Deroo, P., Griffith, C., Tinetti, G., Thatte, A., Vasisht, G., Chen, P., Bouwman, J., Crossfield, I., Angerhausen, D.... (2010) A ground-based near-infrared emission spectrum of the exoplanet HD 189733b. Nature, 463(7281), 637-639. DOI: 10.1038/nature08775
- March 4, 2010
- 01:58 AM
- 45 views
In the News this month: the molecular content of early galaxies
A long-standing question in the study of is whether the process was more efficient in the early universe than it is today. Stars form through the collapse of clouds of cold gas. As the collapse progresses, the of the cloud gets denser and hotter until begins and a star is born. In the local universe, however, cold molecular gas is relatively rare so star formation occurs slowly; the Milky Way forms new stars at a rate of only a few per year. More distant galaxies formed stars at a much higher........ Read more »
Tacconi, L., Genzel, R., Neri, R., Cox, P., Cooper, M., Shapiro, K., Bolatto, A., Bouché, N., Bournaud, F., Burkert, A.... (2010) High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature, 463(7282), 781-784. DOI: 10.1038/nature08773
- March 4, 2010
- 01:16 AM
- 42 views
In the News this month: the explosion mechanism behind type Ia supernovae
Supernova explosions are initially by the chemical signatures in their optical spectra. While some are caused by the catastrophic collapse of stars more than eight times as massive as the Sun, others are thought to be caused by , stars like the Sun which have already evolved off the main sequence and shrunk in size. Called Type Ia supernovae, such explosions are thought to have a fixed brightness, allowing them to be used as to measure distances to galaxies and test cosmological models of the ........ Read more »
Gilfanov, M., & Bogdán, A. (2010) An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate. Nature, 463(7283), 924-925. DOI: 10.1038/nature08685
- March 1, 2010
- 12:50 PM
- 51 views
On Software in Astronomy
by sarah in SarahAskew
I’ve been giving some thought to software development in astronomy, which is a difficult topic. All astronomers agree that good data processing, and hence good software, is crucial to doing rigorous science. To interpret observational data, to translate electrons on a detector to scientific knowledge, requires a solid understanding of the instrument, the observing conditions, [...]... Read more »
C. Sandin, T. Becker, M. M. Roth, J. Gerssen, A. Monreal-Ibero, P. Böhm, & P. Weilbacher. (2010) p3d: a general data-reduction tool for fiber-fed integral-field spectrographs. accepted by A. arXiv: 1002.4406v1
- March 1, 2010
- 08:32 AM
- 53 views
Stars Born as Planets
by Invader Xan in Supernova Condensate
Planets are resilient things. They can survive a lot of punishment from their host stars, with some planets having survived being broiled and others even having survived being engulfed as their parent star swells into a red giant. Amazingly, the means by which planets form is no less hardy, for instance being formed in the debris left after a supernova as pulsar planets. So if the method for planet formation is so rugged, what would happen if you started out with an extremely massive star? Could........ Read more »
Amit Kashi, & Noam Soker. (2010) Forming Low Mass Stars and Brown Dwarfs in Protoplanetary Disks of Very Massive Stars. preprint. arXiv: 1002.4693v1
- February 28, 2010
- 04:20 AM
- 46 views
Counting galaxy mergers you can’t see
by Rita in we are all in the gutter
I’m going to pick up where I left off a while ago, when we talked about galaxy evolution. I have a staggering backlog of papers to read on my desk, most of which have the words “merger history”, “mass assembly” or “galaxy pairs”. All of these expressions are more or less equivalent, and they relate [...]... Read more »
R. De Propris, S. P. Driver, M. M. Colless, M. J. Drinkwater, N. P. Ross, J. Bland-Hawthorn, D. G. York, & K. Pimbblet. (2010) An upper limit to the dry merger rate at ~ 0.55. ApJ. arXiv: 1001.0566v1
Sugata Kaviraj, Kok-Meng Tan, Richard S. Ellis, & Joseph Silk. (2010) The principal driver of star formation in early-type galaxies at late epochs: the case for minor mergers. MNRAS (submitted). arXiv: 1001.2141v1
- February 27, 2010
- 10:06 PM
- 35 views
Spiral galaxies are taking over
by Charles Daney in Science and Reason
Everybody knows what a spiral galaxy looks like. Here's a typical nearby example (M74):Among the largest and brightest galaxies close to our own, about 72% are of this spiral type, like M74. There is a classification system for galaxy shapes, and the remaining 28% of large, bright, nearby galaxies fall into classes called "elliptical", "lenticular", or simply "peculiar". (For simplicity and for other reasons that will become apparent, we're ignoring smalle........ Read more »
Delgado-Serrano, R., Hammer, F., Yang, Y., Puech, M., Flores, H., & Rodrigues, M. (2010) How was the Hubble sequence 6 Gyr ago?. Astronomy and Astrophysics. DOI: 10.1051/0004-6361/200912704
- February 24, 2010
- 03:06 AM
- 63 views
Where have all the protons gone?
by Charles Daney in Science and Reason
Astronomers have long known that there is a rather close relationship between the intrinsic luminosity of a spiral galaxy and the rotational velocity of stars (around the galactic center) in the outer portions of the galaxy. This relationship even has a name: the Tully-Fisher relation.It has also been known that small, nearby dwarf galaxies, which are irregular in shape, are not nearly as bright as they "should" be, according to the Tully-Fisher relation, given the measured average velocities of........ Read more »
McGaugh, S., Schombert, J., de Blok, W., & Zagursky, M. (2010) THE BARYON CONTENT OF COSMIC STRUCTURES. The Astrophysical Journal, 708(1). DOI: 10.1088/2041-8205/708/1/L14
- February 22, 2010
- 02:15 AM
- 58 views
Dwarf galaxies start making sense
by Charles Daney in Science and Reason
Cosmology has, for a decade, had its "standard model", which largely explains most of the cosmological phenomena that astronomers are able to observe. Except for a relatively small number of things that don't seem to make sense in the model. Prominent among the latter are dwarf galaxies – by one definition, galaxies having less than 10% of the total mass of the Milky Way.The standard model of cosmology is known officially as the Λ-cold-dark-matter model – ΛCDM. (This th........ Read more »
Governato, F., Brook, C., Mayer, L., Brooks, A., Rhee, G., Wadsley, J., Jonsson, P., Willman, B., Stinson, G., Quinn, T.... (2010) Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows. Nature, 463(7278), 203-206. DOI: 10.1038/nature08640
- February 19, 2010
- 03:47 AM
- 39 views
An Upper Limit On Not Knowing What the F*** They're Doing
by The Astronomist in The Astronomist.
First, I should say that the Supernova Cosmology Group and others using Type Ia supernova as standard candles are very precise in their work and I don't seriously doubt their results as they have been very consistent with other observations. There is though the one dark shadow looming over all their results and that is systematic error. Cosmologists use Type Ia supernova as a lighthouse in the dark because we can assume that all lighthouses have the same intrinsic luminosity and therefore any di........ Read more »
Marat Gilfanov, & Akos Bogdan. (2010) An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate. Nature, 18 February 2010, Vol.463, p.924. arXiv: 1002.3359v1
- February 19, 2010
- 12:05 AM
- 81 views
An Upper Limit On Not Knowing What the F*** They're Doing
by The Astronomist in The Astronomist.
First, I should say that the Supernova Cosmology Group and others using Type Ia supernova as standard candles are very precise in their work and I don't seriously doubt their results as they have been very consistent with other observations. There is though the one dark shadow looming over all their results and that is systematic error.... Read more »
Marat Gilfanov, & Akos Bogdan. (2010) An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate. Nature, 18 February 2010, Vol.463, p.924. arXiv: 1002.3359v1
- February 17, 2010
- 07:10 PM
- 73 views
Pop Goes the Pulsar
by Brian Koberlein in Upon Reflection
Note: This entry is a bit different from most of my posts. It is more mathematical, and uses MathML extensively to display equations. If you see gibberish instead of equations, then your browser isn't capable of viewing them. If you...... Read more »
HEWISH, A., BELL, S., PILKINGTON, J., SCOTT, P., & COLLINS, R. (1968) Observation of a Rapidly Pulsating Radio Source. Nature, 217(5130), 709-713. DOI: 10.1038/217709a0
- February 15, 2010
- 10:46 PM
- 64 views
Far out!
by Charles Daney in Science and Reason
If you're interested in something out of the ordinary, astronomically speaking, the best place to look for the exotic may be as far away (in both space and time) as possible.Perhaps that's why I like to consider really far out stuff, like the most distant gamma-ray burst seen yet. Or maybe I just like to get away from the depressing chaos and confusion of "modern" life.In any case, there's always something new, just beyond the farthest thing we've seen yet. That far-out gamma-ray burst (GRB 0904........ Read more »
R. J. Bouwens, G. D. Illingworth, I. Labbe, P. A. Oesch, M. Carollo, M. Trenti, P. G. van Dokkum, M. Franx, M. Stiavelli, V. Gonzalez.... (2009) Constraints on the First Galaxies: z~10 Galaxy Candidates from HST WFC3/IR. Nature. arXiv: 0912.4263v2
- February 10, 2010
- 11:22 PM
- 105 views
The Cosmos isn't strange, people are strange
by The Astronomist in The Astronomist.
The cosmos isn't strange, people are strange. The universe on the largest of scales is actually simple compared to the complexities of the human mind or even the weather. In a statistical sense all current observations indicate that universe is homogeneous and isotropic everywhere. The best evidence for this statement is the cosmic microwave background (CMB) radiation which is light from the big bang that has traveled unimpeded through the universe since recombination. A simp........ Read more »
C. L. Bennett, R. S. Hill, G. Hinshaw, D. Larson, K. M. Smith, J. Dunkley, B. Gold, M. Halpern, N. Jarosik, A. Kogut.... (2010) Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Are There Cosmic Microwave Background Anomalies?. ApJ. arXiv: 1001.4758v1
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