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Proving Inflation?

Posted by tigerhawkvok on May 04, 2009 19:48 in physics , astronomy , IYA

A quick little news snippet from Science: The ESA's new satelitte, Planck, is due to launch on 5/14/09 and will take up the mantle of COBE and WMAP. However, in addition to just improving measurements of the Cosmic Microwave Background, Planck will also possibly prove inflationary theory.

The nuts-and-bolts of inflation say that, in the early early universe, an inversion of the Higgs field resulted in spacetime expanding at superluminal velocities and rapidly slowed down. This explains the flatness of space, the lack of magnetic monopoles, and perhaps the most importantly the uniform temperature of space. This could mean that parts of space no longer causally connected once were, and thus had time to reach a thermal equilibrium before expanding apart.

As a side-effect of inflationary theory, though, we expect to see B-mode polarization of the CMB (that is, polarization of the magnetic field). To quote the article:

But the prize quarry for Planck researchers is the B modes. These features are swirls in the CMB polarization mapped across the sky, and spotting them would essentially clinch the case for the mind-bending theory of inflation.
[...]
Although inflation fits the facts so far, researchers do not yet have direct proof that it occurred. The B modes would provide that. Current theory predicts that inflation should have generated gravitational waves and that those waves should have left lingering swirls in the polarization of the CMB.

The polarization may not be strong enough for Planck to detect, but with luck, they will be — and 45 years after the discovery of the CMB, and 30 years after the proposal of inflation, we might finally have an answer.

DOI: 10.1126/science.324_584b

IYA Entry

"Cosmic Blog?" What?

Posted by tigerhawkvok on March 15, 2009 21:19 in General , IYA

So, I've decided to keep up the "International Year of Astronomy" spirit and append a modified version of the IYA Cosmic Diary logo. Now, I don't quite meet the specifications for this:

The Cosmic Diary is not about the science of astronomy, but about what it is like to be an astronomer. Professionals will blog in text and images about their life, families, friends, hobbies and interests, as well as their work, latest research findings and the challenges they face. The bloggers represent a vibrant cross-section of working astronomers from around the world. They will write in many different languages and come from five continents. They will be asked to explain one particular aspect of their work to the public in more popular language. These "explanations" will be highlighted on the web and used as the basis for a book and documentary to be released during IYA2009 as the legacy of this project. [Source]

Yeah, I'm not even remotely official in this capacity. But, I did want some semi-official logo to stick on astronomy posts, and, helpfully, the IYA provided a source Adobe Illustrator file. Thus, I've appended the "Cosmic Blog" logo (with what I feel are better colors to boot) to the end of my astronomy posts, and will put them on all astronomy posts put up through 2009. Already, this blog is doing better than I'd hoped for in terms of updates — nothing like the Quantum Singularity blog (with all of 17 posts), and I'm keeping things a bit more informative. Not shabby!

In an amusing aside, the real Cosmic Diary site implemented an RSS fetching algorithm that's apparently less robust than my own — it took longer to load and threw an error instead of a graceful faliure.

Finally, is there any display problems with the Twitter feed on the right? It doesn't display right in Opera 10 (on my machine, anyway), but looks like it works on IE 8, Chrome 2, and FF 3. Safari, of course, being the poor Windows port it is, just spun its little pinwheel that covers up the "stop loading" button. Whoops.

Pulsars and Gravity

Posted by tigerhawkvok on March 14, 2009 02:56 in astronomy , news , IYA

Seeing as I mentioned gravity just a few days ago, while the Higgs boson is appropriate fodder, this "Perspectives" piece from Science magazine is a bit more topical.

In an effort to prove ever close to the ultimate answer, physicists and astronomers have been looking to probe gravity even deeper. The best results from orbiting pulsars agree with Einstein's theory of General Relativity to within 0.2%. Alternative models predict marginally, but measurably, different results with the most relativistic systems. The ultimate measure of relativistic gravity waves depend on orbital periods, eccentricity, and masses, so by seeking systems like these we can probe gravity even more deeply than we have already.

On the face of it, it may seem that 0.2% is good enough. 99.8% accurate will, in fact, get you to the Moon (in fact, that much error on your path amounts to a 1.74 km error in your landing site on a 384399 km trip). So why does it even matter? These alternative theories posit different fundamentals about the universe, including the necessity of dark matter and cosmic origin.

Pulsar schematic, via Wikipedia

Now, the most relativistic pulsar system we know of is PSR J0737-3039 — it has an orbital period of 2.4 hours, and an orbital decay of its semimajor axis of 7 mm/yr due to gravitational radiation in the form of gravity waves. Being a pulsar, it is an incredibly accurate clock, and enables measurements of such fine precision to be made, that we need to (and can!) measure the effects of its movement through the galaxy on its orbital decay. So, Deller et al. (DOI: 10.1126/science.1167969) show that using the VLBI and about a decade of observation can smash the possible GR error (or disprove GR at these precisions!) down to 0.01%.

Think about it. We're measuring something located ~600 parsecs away (1800 light-years [Lyr], give or take), measuring its orbital decay to millimeters to narrow constraints on one of the two most accurate theories in science to being "only" 99.99% accurate, up from 99.8%. Astronomy (and science in general) — bloody amazing.

By the way — I provide many links to scientific papers, in large part for rigor's sake, but if any readers (how many readers do I have? Do I have any?) are having difficulty, I'll see what I can do about finding free alternatives, such as arXiv.org preprints.

IYA Entry

Late Kepler Post

Posted by tigerhawkvok on March 10, 2009 20:16 in kepler , astronomy , news , research , IYA

So, I composed most of a post on the Kepler launch, then, well, forgot to post it. Belatedly, here we are:

So, Kepler. I mentioned it a little while ago, what was I talking about? Well, I was talking about the Kepler mission (kepler.gov) being sent up by NASA, set to launch on 3/6/09 (This is one of those "Whoops, posted late" parts).

Kepler is a sattelite that will observer one portion of the sky for its entire mission, looking for transit events. To understand a transit event, consider a lightbulb. When something passes in front of it, it obscures part of the surface from your view, and thus reduces the amount of light you observe. So, by observing the same starfield for its mission duration, Kepler can detect any minute changes in stellar flux, thus detecting a planet. The amount of flux change then gives you the planetary size (since color/spectral profile -> temperature -> size -> flux ).

However, there is a caveat here. Sunspots can often be regular, long lasting, or otherwise look like planets. So, my own impact on the Kepler project came with my research work with Gibor Basri, in which we wrote routines in IDL to analyze our own star for the influence of magnetograms on stellar luminosity profiles (IE, where are sunspots? How big? etc).

Various identification methods picking out
umbrae and penumbrae

A particularly good example can be seen in the figure to the left, where various versions of the algorithms pick out different features in a sunspot group. It is important to note that the differences are exaggerated -- the sun is very bright, so the "dark" spots are valued about 0.85 on an absolute scale. you can also see on the right an early version of the algorithm picking out by far most of the major solar features, including the harder-to-discern faculae, or unsually bright areas (which are, of course, very hard to observe in photos such as these).

Early feature identification

The detection and automation algorithms we developed were actually fairly robust and accurate, though CPU intensive (running through about 100 photos took about 3-4 hours on my now-deceased laptop Liz), though our funding ran out over here before I could complete an algorithm to reverse-construct a star from its magnetic profile. Thus, by also observing the long-range magnetic profile of the stars (particularly Sun-like stars) we can rule out some categories of false positives. Looking at some more "final" algorithm photos, you can see why this could be relevant:


light contrast

Solar feature identification with
later versions of the algorithm

If a dark spot such as that passed along the star, it is enough of a brightness dip that it could register as a false positive — that is to say, it could look very much like a planet. While prolonged observation is one way to get around this, feature identification is another way. And I had a part in it! Nifty!

More:

Updated: 3/13/09

IYA Entry

Possible 22 year old confirmation of gravity waves

Posted by tigerhawkvok on March 04, 2009 17:18 in astronomy , news , IYA

Via Slashdot and the arXiv blog, it turns out that we may have actually detected gravity waves in 1987 associated with SN1987A.

OK, that was a bit of a rush. Let's unpack that a bit. Astrophysicists have been searching for gravity waves for a while now, which are linearized plane wave solutions to the Einstein Field Equations with two polarizations (the other fourteen dropping out). The key bit to this solution is that the coordinate positions of the particles remain constant for all τ, but the fractional change in distance between points A and B changes in an oscillatory manner (as 0.5a sin[ωt+δ] ). Since all but two polarizations drop out, this means that for a plane wave oriented in the z direction, wave effects are restricted to the orthogonal x,y plane.

LIGO

Modern interferometers use long arms with a laser cavity to measure very very small fractional changes in distance via destructive & constructive interference. However, before this, large aluminum cylinders with piezoelectric crystals arranged about it were constructed in an attempt to measure these gravity waves. When SN 1987A went off (Supernova 1987 A, as the first one in 1987), John Weber reported that he detected gravitational waves from the SN detonation. However, calculations of first-order effects (almost always the largest) showed that his detector was insufficiently sensitive to have found any gravitational waves.

However, a new paper (preprint) shows that asymmetries in the 1987 explosion could lead to an enhancement by a factor of 104 in SN1987A, putting these waves right in Weber's detectable range.

So, it seems in retrospect that Weber got the short end of the stick, all things considered. But it's definitely worth re-examining his data to see if he did, in fact, confirm gravity waves 22 years ago.

IYA Entry

Goal and Astronomy

Posted by tigerhawkvok on March 02, 2009 15:43 in General , astronomy , IYA

So, I will announce a goal for this month: I intend to post an average of 3 times per week on this blog. There. Maybe posting this will keep me to it.

Sadly, I missed the timetable to post something interesting about Comet Lulin, which is incredibly low magnitude by now, and would be a shade tricky to spot even with a telescope (at least a 12" would really be needed at this point). However, if you're out stargazing this month, things are fairly boring quiet. You will be able to see Venus set around 8:30 PM (getting earlier as the month progresses), and Saturn transit (move across the meridian) around midnight. These are pre-DST time, so after March 8th they will advance an hour (IE, transit at 1 AM).

On the docket: Mus musculus, and perhaps a bit about evolution.

IYA Entry

Black holes and revelations

Posted by tigerhawkvok on February 21, 2009 15:50 in physics , astronomy , IYA

Last night, I gave a talk to the Tri-Valley Stargazers about black holes. It actually went rather well, and as usual, I enjoyed lecturing.

For those who are curious, here is the PowerPoint presentation (Office 2007) and the PDF.

IYA Entry

Happy New Year, and Welcome to IYA!

Posted by tigerhawkvok on January 02, 2009 00:06 in General , astronomy , IYA

Happy New Year everyone, and welcome to the International Year of Astronomy! It has been 400 years since Galileo turned a telescope to the sky, and first looked into the heavens. In addition to what posting I do (I'll try to keep it up at a higher rate), I'll try to post more about astronomy-related topics. See the link in my sidebar about this. Let's whet some appetites:

APOD 20090102
IYA Entry