Free Astronomy Magazine May-June 2015

SPACE CHRONICLES Dusty cloud passes galactic centre black hole by ESO instrument on ESO’s Very Large Tele- scope and also monitored the be haviour of the central black hole re- gion in polarised light using the NACO instrument.) The images of infrared light coming from glowing hydrogen show that servations as the region is hidden behind thick dust clouds, requiring observations in infrared light. And, in addition, the events occur very close to the black hole, requiring adaptive optics to get sharp enough images. The team used the SINFONI A supermassive black hole with a mass four million times that of the Sun lies at the heart of the Milky Way galaxy. It is orbited by a small group of bright stars and, in addition, an enigmatic dusty cloud, known as G2, has been track- ed on its fall towards the black hole over the last few years. Closest approach, known as peribothron, was predicted to be in May 2014. The great tidal forces in this region of very strong gravity were expect- ed to tear the cloud apart and dis- perse it along its orbit. Some of this material would feed the black hole and lead to sudden flaring and other evidence of the monster enjoy- ing a rare meal. To study these uni- que events, the region at the galac- tic centre has been very carefully observed over the last few years by many teams using large telescopes around the world. A team led by Andreas Eckart (Uni- versity of Cologne, Germany) has ob- served the region using ESO’s Very Large Telescope (VLT) over many years, including new observations during the critical period from Feb- ruary to September 2014, just before and after the peribothron event in May 2014. These new observations are consistent with earlier ones made using the Keck Telescope on Hawaii. (These are very difficult ob- T his composite image shows the motion of the dusty cloud G2 as it closes in on, and then passes, the supermas- sive black hole at the centre of the Milky Way. These new obser- vations with ESO’s VLT have shown that the cloud appears to have survived its close en- counter with the black hole and remains a compact object that is not significantly extend- ed. In this image the position of the cloud in the years 2006, 2010, 2012 and February and September 2014 are shown, from left to right. The blobs have been colourised to show the motion of the cloud, red indicated that the object is reced- ing and blue approach- ing. The cross marks the position of the su- permassive black hole. [ESO/A. Eckart] 2006 2010 2012 Feb. 2014