Astrophysics: Falling into black holes

A model for the gas cloud falling into our galaxy’s central black hole is proposed in Nature Communications this week. The results suggest a plausible explanation for recent observations of the galactic centre.

Observations of a cloud of ionised gas and dust falling towards Sagittarius A* (SgrA*, the black hole at the centre of the Milky Way) were reported earlier this year. The cloud is orbiting the black hole and will reach its closet point of orbit next year. Ruth Murray-Clay and Abraham Loeb suggest that this cloud is formed from a proto-planetary disc surrounding a young, low-mass star. The star was dislodged from its original orbit at the inner edge of a ring of young stars circling SgrA* and is now hurtling towards the black hole on an elliptical orbit. Although the star is too small to be directly observed, the proto-planetary dust cloud accompanying it is being disrupted as they travel, and this debris is what has been detected. Murray-Clay and Loeb show that their model matches the current observations of the cloud properties and predict the cloud’s evolution over the next few years as it approaches the black hole.

Although the model can naturally explain the observed properties of the cloud, the calculated probability for it to explain the observed position of the star in its orbit around SgrA* is very low. Future observations will enable testing of the model and determine whether this mechanism is the most plausible.