Why is the Milky Way blowing bubbles at 2 Million miles per hour?
Two million years ago, a massive eruption in the Milky Way caused gases to bubble out into the universe at two million miles per hour (3.2km/h).
Now, astronomers are beginning to see the aftermath of the explosion: billowing clouds of gas towering 30,000 light-years above and below the plane of our galaxy.
Dubbed ‘Fermi Bubbles’, these mysterious structures shouldn’t exist according to current astronomical theory – and scientists are still unable what caused their outburst.
The enormous structure was discovered five years ago as a gamma-ray glow on the sky in the direction of the galactic centre.
Using the Hubble telescope, Nasa is attempting to find the mass of the material being blown out of our galaxy, which could help determine the cause of the outburst.
‘We can study the details of these structures. We can look at how big the bubbles are and can measure how much of the sky they are covering.’
WHY IS THE MILKY WAY BLOWING BUBBLES? THEORIES SO FAR…
There are a number of theories attempting to explain why the Milky Way is blowing these enormous bubbles.
Some scientists believe they could have been created by huge jets of accelerated matter blasting out from the supermassive black hole at the centre of our galaxy.
Or they could have been formed by a population of giant stars, born from the plentiful gas surrounding the black hole, all exploding as supernovae at roughly the same time.
Another theory is that they are the result of collisions between dark matter particles that result in their annihilation, emitting charged particles in the process.
‘There are several models that explain them, but none of the models is perfect,’ said Dmitry Malyshev, a postdoctoral researcher at the Kavli Institute.
The giant lobes of Fermi Bubbles glow in nearly uniform gamma rays and appear like two 30,000-light-year-tall incandescent bulbs screwed into the centre of the galaxy.
The detection of their high-energy gamma rays suggested that a violent event in the galaxy’s core violently launched energised gas into space.
To provide more information about the outflows, Professor Fox looked at the ultraviolet light from a distant quasar – a galaxy with a bright active nucleus – that lies behind the northern bubble.
Imprinted on that light as it travels through the lobe is unique information about the velocity, composition, and temperature of the expanding gas inside the bubble.
The study found silicon, carbon, and aluminium, indicating that the gas is enriched in the heavy elements produced inside stars and represents the ancient remnants of star formation.
It measured the temperature of the gas at approximately 9,700°C (17,500°C), which is much cooler than expected.
‘We are seeing cooler gas, perhaps interstellar gas in our galaxy’s disk, being swept up into that hot outflow,’ Professor Fox explained.