APOD: Fermi Epicyles: The Vela Pulsar's Path (2012 May 04)

[ronavoig]

At first glimpse it reminded me of a Calabi–Yau manifold.

[Chris Peterson]

At first glimpse it reminded me of a Calabi–Yau manifold.

I think many of us were thinking the same thing! <g>

[Beyond]

Well, then i am one of the few. I have never heard of a Calabi-Yau manifold.

[neufer]

Ah... I misread things and took this to be where the camera points in the sky. So I'll agree that any particular source (in this case the Vela pulsar) is unlikely to ever be in exactly the same place on the focal plane. I don't think that's remotely the point of the image, however. What it illustrates, if anything, is how much time this object spends on the camera's detector despite the complex path it follows over the sky.

As with virtually every other object in the sky, The Vela Pulsar spends about 20% of the time being tracked on Fermi's LAT camera's detector.

The LAT's field of view is large, about 20% of the sky.

However, I don't know quite how one could possibly deduce that fact simply from the complex path the Vela Pulsar follows over the detector (even if one knew the time interval involved).

What this APOD illustrates, IMO, is the complex elegant path this bright object makes on the wide field LAT camera's detector over a long period of time. (Not unlike: http://apod.nasa.gov/apod/ap120121.html )

[Chris Peterson]

What this APOD illustrates, IMO, is the complex elegant path this bright object makes on the wide field LAT camera's detector over a long period of time. (Not unlike: http://apod.nasa.gov/apod/ap120121.html )

It certainly does that.

[ronavoig]

Well then I guess the structure of the universe must be the same viewed at all levels. From the very small to what we see as the very large. I'm glad that's finally known. I always thought the end of the universe looped around to its start. Ron

[Sam]

The video linked to at "By design" is worth a watch and a listen;
I myself thought it to be a superb example of Gesamtkunstwerk.

(Composed by Nolan Gasser; performed by the American Brass Quintet)

Click to play embedded YouTube video.

--
Sam

[neufer]

[b][color=#0000FF]The Vela Pulsar and its pulsar wind nebula, [/color][/b]

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<<The Vela Pulsar (PSR B0833-45 or PSR J0835-4510) is a radio, optical, X-ray and gamma-emitting pulsar associated with Vela Supernova Remnant, in the constellation of Vela. The association of the Vela pulsar with the Vela Supernova Remnant, made by astronomers at the University of Sydney in 1968, was direct observational proof that supernovae form neutron stars.

It has a period of 89 ms (the shortest known at the time of its discovery) and the remnant from the supernova explosion is estimated to be travelling at 1,200 km/s. It has the third brightest optical component of all known pulsars (V = 23.6 mag) which pulses twice for every single radio pulse. The Vela pulsar is the brightest persistent object in the high energy gamma ray sky.

In early 1970, Curtis proposed the presence of a planetary companion to explain certain variations observed in the pulsar's timing. The putative object would have a mass of about 0.01 Solar masses (i.e., 10 times the mass of Jupiter) and orbit the parent star at a distance of 0.3 Astronomical Units.>>

[b][url=http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/full/2008/47/aa09956-08/aa09956-08.html]Figure 1[/url] [color=#0000FF] While Vela X-1 is by far the brightest [20 keV to 800 keV X-ray] source in the field-of-view of ISGRI, we also detect 4U 0836-429 as a very prominent source reaching about a third of the average intensity of Vela X-1, and the relatively weak [20 keV to 800 keV X-ray] sources H 0918-5459, the Vela Pulsar.[/color][/b]

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<<Vela X-1 is a pulsing, eclipsing high-mass X-ray binary (HMXB) system, associated with the Uhuru source 4U 0900-40 and the supergiant star HD 77581. The X-ray emission of the neutron star is caused by the capture and accretion of matter from the stellar wind of the supergiant companion.

The orbital period of the system is 8.964 days, with the neutron star being eclipsed for about two days of each orbit by HD 77581. The spin period of the neutron star is about 283 seconds, and gives rise to strong X-ray pulsations. The mass of the pulsar is estimated to be at least 1.88±0.13 solar masses. Long term monitoring of the spin period shows small random increases and decreases over time similar to a random walk. The accreting matter causes the random spin period changes.

Vela X-1 should not be confused with the isolated radio pulsar, Vela X, which is a very different kind of object. Vela X is associated with a very strong 100 MeV gamma-ray source, which corresponds to a rather weak Uhuru X-ray source, 4U 0833-45.>>

Art "Gesamtkunstwerk" Neuendorffer

[Ann]

Well, then i am one of the few. I have never heard of a Calabi-Yau manifold.

I googled "Calabi-Yau manifold". Goodness! I've never read a wikipedia article that managed to confuse me so thoroughly! Or rather, I've never run into so many impossible words in an article that is supposedly in English. Or what about K3 surfaces, Kähler manifolds, canonical bundle, Calabi conjecture and Ricci flat metrics? Wanna know what a compact n-dimensional Kähler manifold M is? Easy as a pie! http://en.wikipedia.org/wiki/Calabi–Yau_manifold wrote:

The canonical bundle of M is trivial.
M has a holomorphic n-form that vanishes nowhere.
The structure group of M can be reduced from U(n) to SU(n).
M has a Kähler metric with global holonomy contained in SU(n).

Still confused? Don't worry, here's a further explanation:

These conditions imply that the first integral Chern class c1(M) of M vanishes, but the converse is not true. The simplest examples where this happens are hyperelliptic surfaces, finite quotients of a complex torus of complex dimension 2, which have vanishing first integral Chern class but the canonical bundle is not trivial.

Riiight. Okay. I feel enlightened. Let's look at a picture for a change:


The picture is from the wikipedia article about Calabi-Yau manifold and shows a section of a quintic Calabi–Yau three-fold (3D projection).

I'm sure you'll be glad to know!



Ann

[sage]

Oh goodness this discussion gave me a laugh right up to, and including, the quintic Calabi–Yau three-fold (3D projection).

It's spirograph lines, people! Billlions and billllions of spirograph lines

[Ann]

Photo: 1.54 m Danish telescope at the European Southern Observatory (ESO)
on 1996 February 14.

Vela pulsar bow shock!
















Ann

[copper5817]

Mr Peterson, thank you for answering my question. I was under the erroeneous assumption that the neutron star was still burning fuel. I am now even more intrigued

[peter_from_nyc]

Beautifully asymmetric. No spirograph-drawing seen.

Actually, as I understand it, it is exactly like a spirograph, or like the epicycles that astronomers used prior to Galileo when they assumed the Earth was the center of the universe.

Here, I believe after a few weeks of looking, thinking and talking about it, is that Fermi moves and takes a picture. The star is stationary. The Fermi Orbiter is the "center of the universe".

An example of epicycles is "The apparent movement of Sun and planets with Earth as center" from Wikipedia "Deferent and epicycle":