A new redshift record!

A new record for most distant object* seems to have been claimed for the gamma ray burst GRB_090423. The burst, a brief flash of gamma rays and associated afterglow, was first detected by the SWIFT satellite, and then ground based telescopes followed up these observations with imaging and, once the optical/near-IR counterpart was found, spectroscopy. In this case the object proved to be very red with essentially no emission in the optical. This is a clear indicator for high redshift. The surprise was just how high – a redshift of 8.1, corresponding to just 630 Million years after the Big Bang.

The burst will have now faded so the likelihood of seeing anything more from this particular spot on the sky is probably low, but these observations push back still further the point at which we know condensed objects to have formed. They’ll also have something to say about the reionization of the universe which should have been happening around the time this gamma ray burst went off.

All rather exciting!

As a further footnote I am impressed that the wikipedia page for GRB_090423 is already up containing clear links to all the GCN circulars on the object. An impressive example of rapid online publication.

* This means most distant collapsed object as opposed to the cosmic microwave background which is more distant, coming just about 100000 years after the Big Bang, but isn’t a collapsed object like a star or black hole since it comes from the opacity of the entire universe.

News from the Sky

As many of you will have heard, two satellites – an Iridium communications satellite and a defunct Russian vehicle – collided in low earth orbit yesterday. This didn’t immediately mean much to me until the phone started ringing in my office. The college media office were looking for someone who could talk to the media about this. Since they know I’m involved with satellite astronomy I got the call.

I thus ended up waiting a fair bit for people to call back, and for a while I thought it would amount to nothing. But I’ve just finished a radio interview with IRN (independent radio news, the radio equivalent to ITN, and serving commercial stations across the UK). Seemed to go well.

If you hear me on your local station let me know!

ESA’s year

BBC News online reports on the upcoming year for ESA. There’s a lot going on, but I’m happy to see that Herschel and Planck are strongly featured.

Cosmic Radio Background discovered?

A balloon borne instrument called ARCADE-2 is causing some excitement as it seems to have discovered an excess of extragalactic emission at frequencies around 3.3 GHz. The above link points to a New York Times article on the result, which shows the prominence it’s achieved. The relevant papers can be found here on the arXiv, including the basic result here and discussion of the excess here.

The three most likely sources for error in these observations are stated as being galactic emission, systematic effects and unaccounted for radio emission from faint known sources. The authors conclude that the signal they see is grater than these possible contributions and suggest radio emission from the first generation of weak active galactic nuclei at high redshift.

I’m not sure what to make of this just yet. Claims like this from single experiments need to be checked and independently confirmed before we can give them serious weight, but it is an interesting result. The most interesting thing is that the waveband where the signal is detected, 3GHz, can be observed from the ground, so the next generation of sensitive radio telescopes, like eMERLIN and EVLA, should be able to make rapid progress on the problem once they start to operate.

A new Class of transient?

Astronomers from one of the large supernova search teams have found something they weren’t expecting. Detailed here, they’ve found an object that brightened and declined over a period of about 100 days, totally unlike a supernova or a microlensing source. Furthermore, it’s optical spectrum has five broad absorption bands which don’t match anything known or expected. No ‘host’ object has been found since the source faded.

It’s not often that a new object stumps astronomers in coming up with an idea of what it might be, but this one is really odd!

With larger, deeper variability studies on the way, for example, the LSST surveys, this object is an interesting hint that there’s more going on up there than we currently think.