Sometimes, if you want to understand the amazing things that happen in space, you have to make sense of them in a lab on Earth, first. Scientists are attempting to model some of the most powerful explosions in the universe by miniaturising them into lab experiments.
An artist concept of a gamma ray burst (Image: ESO, NAOJ/Flickr)
An international team of researchers made beams from a special kind of plasma (a gas where the charged particles are separated and not confined to atoms), called an electron-positron plasma. These beams seem to be creating strong, long-lasting magnetic fields. Perhaps these fields could help the researchers understand similar behaviours in much more violent systems, such as the gamma ray bursts in deep space.
Researcher Gianluca Sarri from Queens University, Belfast explains in a post for The Conversation:
In our experiment, we were able to observe, for the first time, some of the key phenomena that play a major role in the generation of gamma ray bursts, such as the self-generation of magnetic fields that lasted for a long time. These were able to confirm some major theoretical predictions of the strength and distribution of these fields. In short, our experiment independently confirms that the models currently used to understand gamma ray bursts are on the right track.
The team used the intense Gemini laser at the Rutherford Appleton Laboratory in the UK, with a special setup for studying what’s called an “electron-positron plasma beam”, or EPB. They created this beam by passing an intense laser pulse through a chamber filled with helium, which creates a beam of electrons. These electrons hit a lead target, and out comes the EPB, a plasma that has equal amounts of electrons and positrons, their antimatter partners. If you’ll remember, every charged particle has an antimatter partner that’s (almost) exactly the same except with the opposite charge.
The team has done this before. But here, they were able to actually make measurements of that EPB’s behaviour, including the long-lasting magnetic field caused by it travelling through a background plasma (one consisting of electrons and charged atoms, or ions, instead of positrons), according to the paper published recently in Physical Review Letters.
These phenomena can help explain how those gamma ray bursts form in astrophysical systems such as black holes. Sarri explains that black holes create beams of these electron-positron pairs, which make their own magnetic fields, creating gamma ray bursts – similar to what they have done in the lab.
Obviously a limitation of this work is that the lab is not a real black hole. But perhaps the experimental setup could help researchers better understand gamma ray bursts so they know whether a signal they spot in space comes from a stellar or alien source. Sarri writes: “Our study helps towards understanding black hole and pulsar emissions, so that, whenever we detect anything similar, we know that it is not coming from an alien civilisation.”