Astronomy posts
- November 17, 2011
- 12:00 PM
- 834 views
Milky Way Questions: Bok Globules and Herbig-Haro Objects
by Sarah in One Small Step
ResearchBlogging.orgThe Milky Way Project science team are currently busy laying what we hope is the final hand on our first publication. In this paper, we’ll describe the project and why we decided to take the citizen science approach for the task of identifying bubble structures in the Galaxy. We will also present our first results from the hundreds of thousands of classifications we’ve logged on the site, and how our new bubble catalog might be useful for further studies of star formation and the interstellar medium. As we’re big fans of open data sharing, the paper will of course be made publicly available via Arxiv.... Read more »
Reipurth, B., & Bally, J. (2001) Herbig-Haro Flows: Probes of Early Stellar Evolution . Annual Review of Astronomy and Astrophysics, 39(1), 403-455. DOI: 10.1146/annurev.astro.39.1.403
- November 16, 2011
- 03:50 PM
- 936 views
Be/X-ray binaries and 2 types of supernovae
by Olga Vovk in Universe at a glance
two subpopulations of Be/Xray binaries can associated with the two types of Type II supernovae providing different mechanisms for neutron star formation where electron-capture supernovae are responsible for low-mass neutron stars in X-ray binaries with short spin periods, short orbital periods and low eccentricities, while iron-core-collapse supernovae produce high-eccentricity binaries containing high-mass neutron stars, with longer spin periods.... Read more »
Christian Knigge, Malcolm Coe, & Philipp Podsiadlowski. (2011) Two Populations of X-ray Pulsars Produced by Two Types of Supernovae. Nature. arXiv: 1111.2051v1
- November 15, 2011
- 03:28 PM
- 530 views
How to (hopefully) not drown in data
by Emma in we are all in the gutter
More is better, right? Bigger telescopes and bigger surveys are both undoubtedly good things, but to make the best use of these advances we need to be able to handle the corresponding increase in data flow, and subsequent pressure on the astronomical archives which are going to have to cope with it. This is a [...]... Read more »
G. Bruce Berriman, & Steven L. Groom. (2011) How Will Astronomy Archives Survive The Data Tsunami?. ACM Queue. arXiv: 1111.0075v1
- November 14, 2011
- 07:54 AM
- 483 views
The earliest astronomers?
The short version of this post is that Astronomy in the Upper Palaeolithic? by Hayden & Villeneuve is a great paper. If you’re interested in astronomy in hunter-gatherer societies you should read it. I’m going to disagree with some parts of the paper below, but if Hayden & Villeneuve are wrong about some things, then [...]... Read more »
Hayden, B., & Villeneuve, S. (2011) Astronomy in the Upper Palaeolithic?. Cambridge Archaeological Journal, 21(03), 331-355. DOI: 10.1017/S0959774311000400
- November 14, 2011
- 07:02 AM
- 819 views
Scientists have found a recipe for cooking the solar system from scratch
by United Academics in United Academics
You take a cold cloud of gas, and set it 15 light-years from an exploding supernova. Stun the cloud with the supernova’s shockwave. Incubate, and watch as the solar system begins to take shape.... Read more »
M. Gritschneder, D. N. C. Lin, S. D. Murray, Q. -Z. Yin, & M. -N. Gong. (2011) The Supernova Triggered Formation and Enrichment of Our Solar System. Astrophysical Journal. arXiv: 1111.0012v1
- November 11, 2011
- 11:00 PM
- 473 views
Galaxy interactions accelerate the growth of supermassive black holes
by Charles Daney in Today's Science
It’s now well-known that there’s a rough correlation between a galaxy’s size and the size of its central supermassive black hole (SMBH). The correlation is even better (for spiral galaxies) between the black hole size and the size of the central bulge of the galaxy. It’s been found that the mass of a SMBH is [...]... Read more »
J. D. Silverman, P. Kampczyk, K. Jahnke, R. Andrae, S. Lilly, M. Elvis, F. Civano, V. Mainieri, C. Vignali, G. Zamorani.... (2011) The impact of galaxy interactions on AGN activity in zCOSMOS. Astrophysical Journal. arXiv: 1109.1292v1
- November 8, 2011
- 11:30 PM
- 403 views
Hubble directly observes the disk around a black hole
by Charles Daney in Today's Science
Quasars are the brightest persistent objects in the universe. They represent the brightest examples of a somewhat more common object: an active galactic nucleus (AGN). As the name implies, an AGN exists at the center of some galaxies. Most quasars, and even most AGN, are not found in the nearby universe, since they are especially [...]... Read more »
Muñoz, J., Mediavilla, E., Kochanek, C., Falco, E., & Mosquera, A. (2011) A STUDY OF GRAVITATIONAL LENS CHROMATICITY WITH THE HUBBLE SPACE TELESCOPE . The Astrophysical Journal, 742(2), 67. DOI: 10.1088/0004-637X/742/2/67
- November 5, 2011
- 12:43 AM
- 430 views
Record-breaking gamma-ray emissions from a millisecond pulsar
by Charles Daney in Today's Science
Breaking old records for some statistic or another generally makes for catchy headlines, at least. If nothing else, the fact that the statistic is being tracked (whether or not by Guinness) suggests it’s a matter of more than passing interest. Now astrophysicists have come up with a new find that breaks three records at the [...]... Read more »
, ., Freire, P., Abdo, A., Ajello, M., Allafort, A., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R.... (2011) Fermi Detection of a Luminous γ-Ray Pulsar in a Globular Cluster. Science. DOI: 10.1126/science.1207141
- October 31, 2011
- 12:35 PM
- 1,032 views
Could The First Stars In The Universe Really Be Annihilating Dark Matter?
by Joseph Smidt in The Eternal Universe
Stars today burn bright through the interactions of elements like hydrogen and helium. But was that the same story for the first stars in the universe, or was their light dominated by the annihilation of dark matter? Recently, Ili et al. took up the challenge of finding out what astronomers should be looking for if this is the cas.
Some background: If dark matter really is a weakly interacting particle, then shortly after the big bang, when the universe was very hot and dense, dark matter particles should have been rapidly annihilating. But what if, after gravitational collapse, the original dark matter halos (think giant globs of dark matter being pulled together by gravity) became so dense that it re-triggered the annihilation of dark matter? If this happened, the light from the first stars would not be mainly from elements like hydrogen and helium interacting, but instead be from dark matter annihilations themselves.
Well how could we detect such a thing? Well start by looking at the plot below:
Here we see the predicted "star formation rate" versus redshift predicted by their numerical simulations. What this shows is that the peak star formation of these "dark stars", as they are called, happened at a redshift of around ~12, or ~13 billion years ago, just after the big bang. (Remember, the higher the redshift the farther back in time.)
When an object emits a lot of light a long time ago, two things happen:
The light becomes redshifted due to the expansion of the universe so that what once was visible light becomes infrared.
They lose a lot of signal at certain wavelengths due to the Lyman alpha forest. (See plot below).
The plot above shows what happens when you have the combination of 1 and 2, and is the predicted "SED" for these objects meaning, this is how bright the objects are supposed to be at each wavelength. As you can see, one one hand, since these objects are at high redshift, the light they emit at the ultra-violet and visible wavelengths has been redshifted to the infrared. Second, because of the Lyman alpha-forest, you see a drop of below certain wavelengths of light. (If you don't understand all this it's fine, just know there are predictions for how bright these objects should be at each wavelength so we can now go look for something with that pattern.)
Unfortunately, we can stare at these objects at every wavelength. Instead, we have to use powerful telescopes and stare at them at the specific wavelengths of those telescopes and hope for the best. For example, this is a prediction of what Hubble could see in the 1.25 and 1.6 micrometer wavelength bands it has:
The solid red and blue curves are the predictions of the "magnitudes" of these objects in the 1.6 (red) and 1.25 (blue) micrometer bands of Hubble. (Magnitude is a measure of brightness and the smaller the magnitude the brighter the object... not a typo, astronomers do everything backwards...) So if you could find an object at redshift 10 with Hubble with a magnitude of ~28 in the 1.6 micrometer band and ~30 in the 1.25 micrometer band, that could be a good hint.
The next step would be to rule out such an object being a normal star. To do this you use spectroscopy:
Differentiating first galaxies at z>10 from [dark stars] would be possible with spectroscopy: the [dark stars] (which are too cool produce
significant nebular emission) will have only absorption lines while the galaxies are likely
to produce emission lines as well. .Of particular interest would be the HeII emission
lines at λ ∼ 1.6µ as well as Hα lines which would be signatures of early galaxies rather
than [dark stars].
So there you go: find a high redshift object with the right drop-off in brightness in the right wavelength bands with the right spectroscopy properties and you make have a star, not powered by the interactions of hydrogen and helium like stars today, but may in fact be light from dark matter annihilation similar to the theoretical dark matter annihilation that may have been given off just after the big bang.
Cosmin Ilie, Katherine Freese, Monica Valluri, Ilian T. Iliev, & Paul Shapiro (2011). Observing Dark Stars with JWST e-print arXiv: 1110.6202v1
... Read more »
Cosmin Ilie, Katherine Freese, Monica Valluri, Ilian T. Iliev, & Paul Shapiro. (2011) Observing Dark Stars with JWST. e-print. arXiv: 1110.6202v1
- October 30, 2011
- 04:39 AM
- 434 views
Astronomers Pin Down Galaxy Collision Rate
by Charles Daney in Today's Science
Galaxies have been growing over most of the 13.7 billion year history of the universe. Some of the growth is due to intergalactic gas gradually swept up by an existing galaxy and then driving star formation in the galaxy. But another growth mechanism is the merger of two (and sometimes more) existing galaxies into one. [...]... Read more »
Jennifer M. Lotz, Patrik Jonsson, T. J. Cox, Darren Croton, Joel R. Primack, Rachel S. Somerville, & Kyle Stewart. (2011) The Major and Minor Galaxy Merger Rates at z . Astrophysical Journal. arXiv: 1108.2508v1
- October 28, 2011
- 08:39 AM
- 16,263 views
Blue stragglers formed by engulfing red giants
by Kelly Oakes in Basic Space
Unusual stars known as blue stragglers have been causing trouble for astronomers since they were first seen in 1953: they are hotter and brighter than they should be, and much younger too. Now, they are causing mischief again for astronomers that are trying to work out where they come from.... Read more »
Geller AM, & Mathieu RD. (2011) A mass transfer origin for blue stragglers in NGC 188 as revealed by half-solar-mass companions. Nature, 478(7369), 356-9. PMID: 22012393
- October 26, 2011
- 04:24 PM
- 526 views
Dipping into the Royal Society’s archive
by Emma in we are all in the gutter
I’m not supposed to be blogging tonight but I’ve allowed myself half an hour to advertise the announcement from the Royal Society today that they’re making their entire journal archive permanently available online for free. The society was founded in 1660 with the aim of bringing together eminent scientists to discuss their research and promote [...]... Read more »
Herschel, W. (1785) On the Construction of the Heavens. By William Herschel, Esq. F. R. S. Philosophical Transactions of the Royal Society of London, 213-266. DOI: 10.1098/rstl.1785.0012
Herschel, W. (1785) Catalogue of Double Stars. By William Herschel, Esq. F. R. S. Philosophical Transactions of the Royal Society of London, 40-126. DOI: 10.1098/rstl.1785.0006
- October 24, 2011
- 07:38 AM
- 628 views
Scientists release most accurate simulation of the universe to date
by United Academics in United Academics
The Bolshoi supercomputer simulation, is the most accurate and detailed large cosmological simulation run to date (“bolshoi” is the Russian word for “great” or “grand”), giving physicists and astronomers a powerful new tool for understanding such cosmic mysteries as galaxy formation, dark matter, and dark energy.... Read more »
A. Klypin, S. Trujillo-Gomez, & J. Primack. (2010) Halos and galaxies in the standard cosmological model: results from the Bolshoi simulation. Xavi.org. arXiv: 1002.3660v4
Sebastian Trujillo-Gomez, Anatoly Klypin, Joel Primack, & Aaron J. Romanowsky. (2010) Galaxies in LCDM with Halo Abundance Matching: luminosity-velocity relation, baryonic mass-velocity relation, velocity function and clustering. Arxiv.org. arXiv: 1005.1289v3
- October 24, 2011
- 07:31 AM
- 556 views
Scientists release most accurate simulation of the universe to date
by Gijs van der Klei in UA
The Bolshoi supercomputer simulation, is the most accurate and detailed large cosmological simulation run to date (“bolshoi” is the Russian word for “great” or “grand”), giving physicists and astronomers a powerful new tool for understanding such cosmic mysteries as galaxy formation, dark matter, and dark energy. The simulation traces the evolution of the large-scale structure [...]... Read more »
A. Klypin, S. Trujillo-Gomez, & J. Primack. (2010) Halos and galaxies in the standard cosmological model: results from the Bolshoi simulation. Xavi.org. arXiv: 1002.3660v4
Sebastian Trujillo-Gomez, Anatoly Klypin, Joel Primack, & Aaron J. Romanowsky. (2010) Galaxies in LCDM with Halo Abundance Matching: luminosity-velocity relation, baryonic mass-velocity relation, velocity function and clustering. Arxiv.org. arXiv: 1005.1289v3
- October 21, 2011
- 09:05 AM
- 870 views
In Praise of the Comet
by thesoftanonymous in the.soft.anonymous
Comets get a lot of bad press. Before science came along, they were usually seen as bad omens from the gods – “tokens of impending doom” in the words of one Roman astrologer. Even now that we know comets to be lumps of ice and rock flying through space, countless movies portray them as harbingers of doom and destroyers of mankind.
But comets also deserve some praise, because we probably wouldn’t be here without them. Here's why...... Read more »
Hartogh P, Lis DC, Bockelée-Morvan D, de Val-Borro M, Biver N, Küppers M, Emprechtinger M, Bergin EA, Crovisier J, Rengel M.... (2011) Ocean-like water in the Jupiter-family comet 103P/Hartley 2. Nature, 478(7368), 218-20. PMID: 21976024
Michiel R. Hogerheijde, Edwin A. Bergin, Christian Brinch, L. Ilsedore Cleeves, Jeffrey K. J. Fogel, Geoffrey A. Blake, Carsten Dominik, Dariusz C. Lis, Gary Melnick, David Neufeld.... (2011) Detection of the Water Reservoir in a Forming Planetary System. Science 6054 (2011), 338. arXiv: 1110.4600v1
- October 20, 2011
- 06:30 PM
- 406 views
Distant Galaxies Reveal The Clearing of the Cosmic Fog
by Charles Daney in Today's Science
The first billion years after the big bang (out of about 13.7 billion years total since then) were among the most interesting in terms of giving birth to the kind of objects that still dominate the scene today. Mostly that means stars and galaxies, plus a few exotica such as quasars. Unfortunately, it’s very difficult [...]... Read more »
L. Pentericci, A. Fontana, E. Vanzella, M. Castellano, A. Grazian, M. Dijkstra, K. Boutsia, S. Cristiani, M. Dickinson, E. Giallongo.... (2011) Spectroscopic confirmation of z~7 LBGs: probing the earliest galaxies and the epoch of reionization. Astrophysical Journal. arXiv: 1107.1376v1
- October 19, 2011
- 05:20 PM
- 665 views
Space cleaner wanted: must have own laser
by Emma in we are all in the gutter
Since the launch of Sputnik in 1957 we’ve launched tonnes of stuff (literally) into space. We’ve not kept things very tidy up there either, so we now have hundreds of thousands of pieces of junk orbiting around us, threatening to crash into important things like the International Space Station. Or the satellite that handles your [...]... Read more »
Claude R. Phipps, Kevin L. Baker, Brian Bradford, E. Victor George, Stephen B. Libby, Duane A. Liedahl, Bogdan Marcovici, Scot S. Olivier, Lyn D. Pleasance, James P. Reilly.... (2011) Removing Orbital Debris with Lasers. Advances in Space Research. arXiv: 1110.3835v1
- October 17, 2011
- 05:25 PM
- 443 views
Universe’s “Standard Candles” Are White Dwarf Mergers
by Charles Daney in Today's Science
Supernovae are spectacular but fairly rare events, at least on the human time scale. In our own galaxy, only 5 have been seen (necessarily by the naked eye, before telescopes were invented in 1608) in the last 2000 years. Since there have been none in our galaxy when any telescopes were available to study them, [...]... Read more »
Graur, O., Poznanski, D., Maoz, D., Yasuda, N., Totani, T., Fukugita, M., Filippenko, A., Foley, R., Silverman, J., Gal-Yam, A.... (2011) Supernovae in the Subaru Deep Field: the rate and delay-time distribution of Type Ia supernovae out to redshift 2. Monthly Notices of the Royal Astronomical Society, 417(2), 916-940. DOI: 10.1111/j.1365-2966.2011.19287.x
- October 17, 2011
- 10:36 AM
- 642 views
The Black Hole Information Escape
by United Academics in United Academics
Professor Sam Braunstein and Dr. Manas Patra at the University of York, UK, saw a chance to uncover another piece of the black hole paradox that so many of the world’s most powerful minds are trying to figure out. Among other reasons, their work helps support the theory that information can escape black holes, which may eventually help us understand more about gravity, picking up where Newton and Einstein left off.... Read more »
Braunstein SL, & Patra MK. (2011) Black Hole Evaporation Rates without Spacetime. Physical review letters, 107(7), 71302. PMID: 21902381
- October 17, 2011
- 07:00 AM
- 574 views
SCUBA’s retirement home
by Emma in we are all in the gutter
A couple of weeks ago I paid a visit to the newly renovated National Museum of Scotland in Edinburgh. Whilst the new galleries are fantastic (and it’s always great to see dinosaur skeletons) my main focus was on finding the new home of a red cylinder with more than a passing resemblance to a British [...]... Read more »
Holland, W., Robson, E., Gear, W., Cunningham, C., Lightfoot, J., Jenness, T., Ivison, R., Stevens, J., Ade, P., Griffin, M.... (1999) SCUBA: a common-user submillimetre camera operating on the James Clerk Maxwell Telescope. Monthly Notices of the Royal Astronomical Society, 303(4), 659-672. DOI: 10.1046/j.1365-8711.1999.02111.x
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