Free Astronomy Magazine July-August 2015

COSMOLOGY A secondary image of the deformed galaxy in the shape of ring should ap- pear almost un- changed at the centre of the same ring. From its brightness, or lack of it, it is pos- sible to deduce the mass of any supermassive black hole nestled in the core of the interposed galaxy that is causing the gravitational lensing. The video below shows how the deformed image of SDP.81 would vary by moving the mass of the interposed galaxy. [Y. Tamura (The University of Tokyo)] monuclear furnaces. Moreover, spectro- scopic data show that the diffuse gas of SDP.81 is largely unstable and that is fall- ing inwards in large quantities, laying the foundation for the future formation of protostellar clouds. Besides reconstructing the shape of the most active regions of SDP.81, Tamura and Oguri’s model suggests also the existence of a supermassive black hole at the centre of the interposed galaxy, whose mass can be estimated from the possible presence and brightness of a weak “copy” of the re- mote galaxy at the centre of Einstein ring. Under optimal conditions that image should be apparent in the high-resolution photos taken by ALMA, but there seems to be no sign of it and the theory is that this hap- pens when the interposed galaxy has at its centre a supermassive black hole of a very considerable size. In the present case, the model indicates a mass of the black hole equal to 200-300 million solar masses, which amounts to a real monster, when we consider that the one nestled at the centre of our galaxy is about 60 times less massive. The results obtained with ALMA on SDP.81 are indicative of the enormous potential of that instrument, especially when used in synergy with that “natural telescope” called gravitational lensing. In the near fu- ture these instruments will be crucial for the characterization of galaxies in the young universe. cal structure approximately 5,000 light- years long. Never before have astronomers been able to unveil this type of relatively small structures at such a great distance from Earth. Dust and molecular gas are the basic ingredients for star formation. How- ever, ALMA cannot directly see the light of the stars of SDP.81, as they do not shine at the same wavelengths in which the instru- ment operates. Nonetheless, these clouds have all the characteristics to be gigantic nurseries filled with new stars, showing, in fact, similar or even greater sizes than the largest protostellar clouds of our galaxy and of those nearby, and, most important- ly, they have a sufficiently low tempera- ture to facilitate the aggregation of huge masses in relatively narrow areas, making it an ideal scenario for the ignition of ther- n