We report on the MASTER Global Robotic Net discovery of an eclipsing binary , MASTER OT J095310.04+335352.8 , previously known as unremarkable star TYC 2505-672-1 , which displays extreme orbital parameters .
The orbital period P=69.1 yr is more than 2.5 times longer than that of \varepsilon -Aurigae , which is the previous record holder .
The light curve is characterized by an extremely deep total eclipse with a depth of more than 4.5 mag , which is symmetrically shaped and has a total duration of 3.5 yrs .
The eclipse is essentially gray .
The spectra acquired with the Russian 6 m BTA telescope both at minimum and maximum light mainly correspond to an M0-1III–type red giant , but the spectra taken at the bottom of eclipse show small traces of a sufficiently hot source .
The observed properties of this system can be better explained as the red giant eclipsed by a large cloud ( the disk ) of small particles surrounding the invisible secondary companion .