Astronomers say they can use “galactoseismology” – the study of ripples in a galaxy’s disk – to map the interior structure of galaxies and learn about dark matter.
The video above shows a computer simulation of gas distribution (l) and stars (r) in the Milky Way and shows how a dwarf galaxy might have affected our galaxy as it brushed past.
A computer simulation of gas distribution (left) and stars (right) in the Milky Way shows how the dwarf galaxy impacted our galaxy (credit: Sukanya Chakrabarti/Rochester Institute of Technology)
Dr Sukanya Chakrabarti, an astronomer at the Rochester Institute of Technology who led the research, said: ‘It’s a bit like throwing a stone into a pond and making ripples.
‘Of course we aren’t talking about a pond, but our galaxy, which is tens of thousands of light years across, and made of stars and gas, but the result is the same – ripples.’
Ripples in the gas in the outermost reaches of the Milky Way were first discovered around a decade ago but have puzzled astronomers since.
Dr Chakrabarti and her team, believe they have solved the mystery after studying a trio of pulsating stars called the Cepheid variable.
These stars, which are visible in the constellation Norma, are thought to lie within a tiny galaxy around 300,000 light years away from the Milky Way.
Presenting their findings at the annual meeting of the American Astronomical Society in Kissimmee, Florida, Dr Chakrabarti said her team were able to calculate the speed at which these stars are moving away from the Milky Way.
Using data from the Gemini Observatory and the Magellan Telescope, they found they are all speeding away a similar speeds – around 450,000mph (724,200km/h).
She said: ‘This really implicates these stars as being part of an organised, fast-moving system, which we believe is a dwarf galaxy.
‘It’s also very likely this dwarf satellite brushed our galaxy millions of years ago and left ripples in its wake.’
She said they were able to calculate the speed of the stars as the pulsing light they produce is tied to their brightness, and so allows astronomers to calculate their distance.
Dr Chakrabarti said there could be many other dwarf galaxies on the outer fringes of our galaxy – known as the galaxy halo – creating other galactic quakes.
Our solar system sits on one of the spiral arms of our galaxy (pictured above Paranal, Chile), but astronomers have found the gas in the outer regions of the Milky Way’s disk are left with ripples much like seismic waves
She said: ‘There could be a population of yet undiscovered Cepheid variables that formed from a gas-rich dwarf galaxy falling into our galaxy’s halo.
‘With the capabilities of today’s telescopes and instruments we should be able to sample enough of the Milky Way’s halo to make reasonable estimates on dark matter content – one of the greatest mysteries in astronomy today.’
Scientists said the research is now part of a new blossoming field in astronomy known a galactoseismology.
Scientists believe there may be other dwarf galaxies that have skimmed past our own. Above a spiral galaxy called M51, thought to be similar to the Milky Way, has a close encounter with another smaller galaxy
Chris Davis, program director at the US National Science Foundation, said: ‘This new, potentially powerful way to study how stars, gas and dust are distributed in galaxies is really quite exciting.
‘Known as galactoseismology, it can trace both visible and invisible materials, including the elusive dark matter.
‘It’s a great way to better understand how galaxies and neighboring satellite dwarf galaxies interact as well.’