In a surprise discovery, astronomers have spotted telltale signs of 11 low-mass stars forming perilously close – within three light-years – to the Milky Way’s supermassive black hole, a region believed to be hostile to star formation. At such a distance, tidal forces driven by the supermassive black hole should be energetic enough to rip apart clouds of dust and gas before they can form stars.
But the presence of these newly-discovered protostars – the formative stage between a dense cloud of gas and a young, shining star – suggests that the conditions necessary for the birth of low-mass stars like our Sun may exist even in one of the most turbulent regions of our galaxy and possibly in similar locales throughout the universe.
“Despite all odds, we see the best evidence yet that low-mass stars are forming startlingly close to the supermassive black hole at the centre of the Milky Way,” said Farhad Yusef-Zadeh, an astronomer at Northwestern University in Evanston, Illinois, and lead author of a study published in the Astrophysical Journal Letters.
“This is a genuinely surprising result and one that demonstrates just how robust star formation can be, even in the most unlikely of places,” Yusef-Zadeh said. The observations were made with Atacama Large Millimeter/submillimeter Array (ALMA), an observatory in Chile. The ALMA data also suggest that these protostars are about 6,000 years old.
“This is important because it is the earliest phase of star formation we have found in this highly hostile environment,” Yusef-Zadeh said. The team of researchers identified these protostars by seeing the classic ‘double lobes’ of material that bracket each of them. These cosmic hourglass-like shapes signal the early stages of star formation.
Molecules, like carbon monoxide (CO), in these lobes glow brightly in millimetre-wavelength light, which ALMA can observe with remarkable precision and sensitivity. The Milky Way’s galactic centre, with its four million solar mass black hole, is located approximately 26,000 light-years from Earth in the direction of the constellation Sagittarius.