It wasn't that long ago, I was writing about the alarming possible scenarios of Kessler syndrome and ablation cascades around Earth. Unnervingly, and almost one year after a UN report about such events, a satellite collision over Siberia last Tuesday (Feb 10th) seems to make the possibility slightly more real.

Two clouds of debris are currently in orbit around the Earth, consisting of over 500 fragments with over 100 of the largest being tracked from Earth. The source -- a collision between the defunct Russian Kosmos 2251 satellite and the American Iridium 33 satellite. Iridium 33, incidentally, was an operational communications satellite. Was. Both craft were destroyed in the collision.

In the following 48 hours, a "clumpy ring" of debris has spread across both orbits. Obviously, this poses quite a hazard for any other satellites in similar orbits (and a lot of communication satellites tend to orbit at similar altitudes). The collision happened at 800km, which is too high up to pose any serious danger to the International Space Station (at a low 350km altitude). It's slightly concerning for Hubble at 610km though. It certainly raises some concerns for scientific instruments in more eccentric orbits, such as IBEX and Chandra too.

Most people aren't actually too aware of hazardous space junk (even those who probably should be). Hopefully this might motivate a few people into trying to clear up the orbital garbage surrounding Earth. Humanity's influence on this planet, so it seems, doesn't stop with the atmosphere...


Image and various facts sourced from spaceweather.com
You can listen to their internet radio broadcasts too!

I just realised -- IBEX launches today!
At about 7:48pm BST (1:48pm EDT).

And it has a launch blog which is live 2 hours beforehand.

And I have mead.
Mead is good. Though it means I probably won't be sat at my computer at 10am on a Sunday.
(Probably a good thing).


EDIT-- I'm rubbish with time zones. It's actually at 7:48 this evening, isn't it?

I read somewhere a while ago (most likely Universe Today) about a plug in for Google Earth that shows around 13,000 of the satellites in orbit around the Earth, dead and alive.

It's really quite amazing exactly how many satellites are out there. More amazing that so many are actually no longer operational. It brings home a very real possiblity. A scenario called kessler syndrome.

Kessler syndrome, proposed by NASA's Donald J Kessler is a situation where the Earth has so much debris in orbit that it renders space travel and the use of satellites essentially impossible for generations. It would take decades to, possibly, millenia for all the junk to clear from the skies.

All newer satellites tend to be put into low Earth orbit where they'll eventually burn up in Earth's atmosphere, but there's a lot of debris still out there. A lot more since a certain Chinese missile test a few months ago (which increased orbital debris by over 20%). Essentially, the more junk is up there, the more chance there is of it smashing into things. Things like space shuttles.

A Kessler Syndrome is a scary scenario, because the more collisions between dead satellites, the more debris will be in orbit, increasing the chance of collisions and so on. The end result we don't want is a catastrophic event known as an ablation cascade.

In an ablation cascade, one explosion causes an expanding shell of debris. This shockwave of junk punctures successive satellites, causing more high velocity debris (possibly further explosions as coolant tanks are punctured) until Earth is wrapped in a coccoon of pulverised metal shards.

Of course, this is an extreme scenario, but seemingly one we should be wary of. Especially if commercial space travel is going to kick off in the next 20 years or so.


In the meantime though, it's really quite staggering. Humanity's most expensive scrap heap. Strangely, almost beautiful as well... Almost like some kind of man made globular cluster.

Seminars at Uni kicked off today with a talk about gamma ray bursts. Which was very cool. The concept of a collapsing black hole at the core of a star, giving out enough energy to punch two beams out of the star before triggering a supernova sounds... well... rather melodramatic. All the same, that's a leading theory for what causes one type of gamma ray burst.

I always enjoy listening to theories that concern things we don't understand. They're always really quite insightful!



So we may not know exactly what the mysterious gamma ray bursts are exactly, but there is one very interesting thing about them. Simply put, if you're quick enough to catch one, you can use them as a background light source. The afterglow of a GRB emits right the way down the full EM spectrum, after all. In other words, if you take the spectrum of a gamma ray burst, everything between you and it will show up in the light. And gamma ray bursts give out a lot of light. Enough light to see it clearly in the sky, brighter than several nearby stars? That's a lot of light.

It's interesting to consider light from a gamma ray burst illuminating interstellar chemicals that formed billions of years ago. Intergalactic chemicals even. I doubt very much has been written about the chemistry of the intergalactic medium. Kinda makes you wonder what might be out there...


Interestingly, all the data collected on these fearsome astrophysical beasts by NASA's Swift mission is publicly available. I might have to have a browse sometime...
(I've been linking to a lot of NASA missions here lately, haven't I...?)

No one seems to have been shouting too loudly about NASA's IBEX probe. In fairness I suppose, it isn't going to be looking at any planets or surveying any galaxies. From an astrochemical perspective though, IBEX is far more exciting than satellites like Fermi -- and that's saying something!

Because everyone likes acronyms these days, IBEX stands for Interstellar Boundary Explorer, and it's objective is to explore the very edge of the solar system, where interstellar space begins.

As any astrochemist will happily tell you, despite being technically a vacuum, interstellar space is far from empty. In fact, it's awash with all kinds of molecules, ions, dust grains and other lovely things that we astrochemists try very hard to identify.

So to explain exactly what IBEX will be looking at, here's a handy little picture...



The Sun, just like all other stars, has a stellar wind (or, when talking about the Sun, a Solar wind). It's constantly flinging streams of charged particles in all directions. The Solar wind is powerful enough that it actually blows a bubble in the interstellar medium, called a heliosphere. Some parts of the heliosphere are pictured above. For a start, it's big. Very big. Heading outwards, well past the Kuiper Belt, the first thing you reach is the Termination Shock. This is where the Solar wind begins to slow down significantly. It starts to compress and heat up. Incidentally, the Termination Shock varies. The more sunspots and flares the Sun is giving off, the stronger the Solar wind, so the further away the Termination Shock. Voyager II actually crossed the boundary 5 times!
(It recorded some data too...)

Cross the Termination Shock and you find yourself in the Heliosheath. This is where the Voyager probes now lie. Their current aim isto study the Heliosheath itself. It's a turbulent region, full of swirling gasses and plasmas, heated by the collision between the Solar wind and the Interstellar Medium (ISM). Though much is still unknown, it's thought that the heliosheath is drawn into a long teardrop shape, due to the Sun's orbit around the galaxy. The ISM pushes harder against one side, causing an elongated shape.

Finally, as the Solar wind becomes too weak to push back the ISM, you reach the Heliopause, the actual boundary of the solar system, and the edge of true interstellar space. As the Sun plows it's way around the galaxy though, it has one final effect. Stars create Bow Shocks as they plough their way through interstellar space, exactly the way a ship's bow cuts through water. It's not very obvious in The Sun's case, but it's been observed in several other stars. The effect's a lot more obvious if the star happens to be travelling through a nebula (like LL Orionis here)...



IBEX launches on October 19th. Let's hope it finds some interesting things!

My name has officially joined the multitude of others recorded on a microchip that'll be aboard NASA's Glory Mission satellite. Silly, but kinda cool.

I even have a nice little certificate to prove it...



Yay me!

Perhaps this could be the sound of opportunity knocking...

AKARI, formerly known as ASTRO-F is a JAXA space telescope from the same stables as the truly wonderful KAGUYA and HINODE space probes. It was sent into orbit with a supply of liquid helium coolant intended to last a bit over a year and a half. During that time, it mapped most of the sky in infrared at extremely high resolution (the colder it is, the less noise -- and liquid helium is about as cold as it gets).

Since it's launch in 2006 it has run out of coolant but continues to be mechanically cooled to around 40K. Now it enters what they've termed it's post-helium phase of operation. It has now been essentially thrown open to all of it's funding partners for telescope time, and courtesy of ESA, this means we can submit a proposal. They're taking submissions right up until July 4th, so I really better get analysing those spectra of mine and see if I need any more data!

AKARI is capable of both imaging and spectroscopy at 1.8 - 5.5 micron wavelengths. This interests me greatly, because a number of interesting spectral features lie in that region, including one that I've recently become rather interested in! Infrared astronomy is always better from orbit, just because the atmosphere has a habit of getting into the way. Don't get me wrong, I enjoy having an atmosphere as much as anyone else... It just has a habit of absorbing lots of that lovely IR and potentially masking genuine stellar features.

I wonder what AKARI's resolution is like...