I was presenting this week’s Astrolunch talk at university. I chose to discuss space debris, and this included a quick overview of the Chinese missile test last year, which create a huge cloud of fragmented debris, much of which is still orbiting the Earth. In January 2007, China launched a surface-to-orbit missile that destroyed a satellite named Fengyun 1C. The act was internationally condemned, though of course no one really punished them.

You can see the debris in this screenshot. Each little Chinese flag is a piece of the satellite that remains in orbit.

If you want to track this debris yourself, you can do so in Google Earth using this handy KMZ file that I’ve created. It uses the same code as my previous efforts for tracking the ISS on Google Earth and tracking satellites on Google Earth in general.

Also, if you’re interested in the talk I gave, you can download the PDF of ‘Space Debris‘.

I wonder if this post will be visible through the Great Firewall of China?

UPDATE: The data used for this Google Earth feed comes directly from NORAD, who provide tracking data for most satellites and other orbiting bodies. I should stress that this only shows the trackable debris. This is only  a percentage of what is up there. Some objects are too small to be tracked by radar and so do not appear.

Yesterday’s Astrolunch talk was given by Prof. Mike Disney on the Stability of the Solar System. It was the first of two talks, and in of itself was very informative. Prof. Disney discussed the history of the question of whether or not the Solar System is a stable system. The final answer surprised me.

In his Principia Mathematica, Newton notes that the planets of the Solar System ought not to remain in their orbits indefinitely. He ascribes their apparent stability and endurance to an act of God, and uses that fact as evidence for the existence of God.

Laplace (another great mathematician of Western history), some hundred years later countered Newton’s argument. He showed that the evidence was actually quite the contrary and in fact the Solar System was stable after all. When asked what this meant about the existence of God, he replied, “I don’t need that hypothesis”.

In 1900, Poincare said that in fact Laplace was the one who was wrong! He argued that in any sufficiently complex, non-linear system, boundary conditions will experience such large-scale effects that the system cannot be stable. This is what is now known as Chaos Theory and it put the nail in the coffin for the idea that the Solar System could ever be considered stable.

Finally in the 1990s, computers became powerful enough that they could simulate the main bodies of the Solar System and answer the question more-or-less once and for all. And what did they find? Well Newton was right about one thing.

In fact, the Solar System is not stable. It sits on a fine line between stability and chaos and oscillates either side of that line on a timescale of roughly one Hubble Time. How does that affect you and me? Well it means that any time now, the Solar System could start to fall out of stability and chuck out a planet… or not.

Discussion after the talk lead me to believe that Mercury would be a best candidate for expulsion from the Solar System. Pluto might be more likely, but the simulations only include the planets, so I think we ought to make moves to get the Earth classified as a dwarf planet immediately.

You can download the 1803 publication Newton’s Principia Mathematica for free, from Google Books as a 17.0MB PDF file.

You can find a more mathematical version of this discussion here, if you like that sort of thing.

Astronomy Blog gives a great little overview of the upcoming meteor shower, including a top pic from Stellarium. I love this shower because I’m often in France for it where I can much better skies.

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This week’s Astrolunch talk was given by Vanessa Stroud from the Faulkes Telescope Group. As is always the case though, this talk was unrelated to her PhD research and she was talking about a new example of a certain type of nova that has been found using GalEx, the Galaxy Evolution Explorer.
This composite image shows Z Camelopardalis, or Z Cam, a double-star system that features a collapsed, dead star, called a white dwarf, and a companion star, as well as a ghostly shell around the system. The massive shell provides evidence of lingering material ejected during and swept up by a powerful classical nova explosion that occurred probably a few thousand years ago.

The image combines data gathered from the far-ultraviolet and near-ultraviolet detectors on NASA’s Galaxy Evolution Explorer on January 25th, 2004. The orbiting observatory first began imaging Z Cam in 2003.

Z Cam is the largest white object in the image, located near the center. Parts of the shell are seen as a lobe-like, wispy, yellowish feature below and to the right of Z Cam, and as two large, whitish, perpendicular lines on the left.

Z Cam was one of the first known recurrent dwarf nova, meaning it erupts in a series of small, “hiccup-like” blasts, unlike classical novae, which undergo a massive explosion. That’s why the huge shell around Z Cam caught the eye of astronomer Dr. Mark Seibert of Carnegie Institution of Washington in Pasadena, California - it could only be explained as the remnant of a full-blown classical nova explosion. This finding provides the first evidence that some binary systems undergo both types of explosions. Previously, a link between the two types of novae had been predicted, but there was no evidence to support the theory.

The faint bluish streak in the bottom right corner of the image is ultraviolet light reflected by dust that may or may not be related to Z Cam. Numerous foreground and background stars and galaxies are visible as yellow and white spots. The yellow objects are strong near-ultraviolet emitters; blue features have strong far-ultraviolet emission; and white objects have nearly equal amounts of near-ultraviolet and far-ultraviolet emission.

There is a lovely high-quality video showing how this sytem works which can be downloaded here.

This post was created from a NASA press release which can be found here.

The image above shows the Bullet Cluster. Also known as 1E 0657-56, this is a pair of clusters of galaxies some 3.4 billion light years away. As Jon Davies told us in yesterday’s Astrolunch meeting however: you should be careful about believing everything you see. This image is not a regular photograph by any means. You can see the galaxies scattered about with an orange glow. This much is familiar. Layered onto this optical data is the pink, X-Ray picture from the Chandra telescope. This pink light is actually the high energy X-Ray radiation from a hot gas that permeates the cluster. Again though it is not unusual to see two different wavelength regimes seen in the same photograph.

What is unusual is that the blue ‘light’ seen here is not photographic in nature at all. It is the location of the mass in this region deduced by weak gravitational lensing - it is not a real effect but rather a mathematical interpretation of where the mass should be. As you can see it does not line up with the visual traces of the mass that we see as light and X-Ray material.

This is because it is believed that the Bullet Cluster shows us quite nicely where the dark matter can be found in this cluster. The interpretation of this image by the researchers who have studied it is that the hot, pink gas is the energy released by ordinary matter in this pair of clusters as they have collided with one another. The energy of the collision has excited the gas to emit in the X-Ray.

However not all the mass in the region is ordinary (something believed to be true about most of the universe). Dark matter is material that has mas but doesn’t interact with other, ordinary matter by the usual routes. It does not feel magnetism, or electrical forces or emit light. But is stays tethered to the ordinary matter by gravity alone.

As these two clusters collided the dark matter passed through like an ordinary pair of gaseous objects would, where as the regular, every day material became heated and disturbed and distorted in shape.

There is a wonderful video of a simulation of this hypothetical collision which you can find here.

This lovely picture adds to the already heated debate among the astrophysical community as to the existence of dark matter.

So if you know me you’ll know that I’m annoyed about Pluto being demoted last year to Dwarf Planet. Well I’ve decided its now time to let it go. Pluto is still a planet, it may be a dwarf planet but just as dwarf stars are still stars and dwarf galaxies are still galaxies, dwarf planets are indeed still planets.

Indeed, Pluto remains the focus of much scientific attention. Just yesterday during our weekly Astrolunch, here at Uni a talk was given on how Pluto may have formed with its three moons, Charon, Nix and Hydra. They compose the only know quadruple body system, since no one is actually the central body - Pluto and Charon are comparably large and so orbit a centre of gravity.

Pluto is also the target of one of NASA big missions. Seen in the image above, launching into space just over a year ago, the New Horizons spacecraft is on its way to Pluto right now. It is using a new kind of propulsion technology to get there by 2015. As I type it is currently swinging by Jupiter using the planet’s immense gravity to alter and accelerate itself along its trajectory toward the edges of the Solar System.

In July 2015 it will encounter Pluto and Charon and study them up close for the first time ever. After this incredible mission it is set to head out into the Kuiper Belt, the region beyond Pluto filled with many smaller bodies, and study some of the objects there.

To find out where New Horizons is at any time you can check out this page on NASA’s mission site and if you have a Mac then there is a dashboard widget called Magic Number that tells you how far away from Pluto the craft is. Or just refresh this webpage to see the image below update.