«Because of its relationship to the larger galaxy, estimated mass, and lack of an optical counterpart, the astronomers believe this gravitational anomaly may be caused by an extremely faint, dark-matter dominated satellite of the lensing galaxy. According to theoretical predictions, most galaxies should be brimming with similar dwarf galaxies and other companion objects. Detecting them, however, has proven challenging. Even around our own Milky Way, astronomers can identify only 40 or so of the thousands of satellite objects that are predicted to be present.»
Эта невидимая галактика отмечена яркой точкой в левой части. Изображение составлено из снимков HST и этой няшки
Подробнее:
http://apod.nasa.gov/apod/ap160420.html
https://public.nrao.edu/news/pressreleases/2016-sdp81-halo
https://public.nrao.edu/news/pressreleases/alma-ring-lens