Astronomers generally assume that the dusty disks where planets form are found around young stars in stellar nurseries. Now, for the first time, a planet-forming disk has been found in the environment of a dying star. A team of astronomers is reporting at the meeting of the American Astronomical Society that material from the dying star Mira A is being captured into a disk around Mira B, its companion. Michael Ireland of the California Institute of Technology and his coauthors say that the finding implies that there should be many similar undiscovered systems in the solar neighborhood, providing a myriad of new places to look for young planets orbiting stars other than our Sun. Located 350 light years away in the constellation of Cetus, Mira first shook the foundations of the astronomy world 400 years ago with its changing brightness: visible to the naked eye for about 1 month at a time, becoming 1.000 times fainter and disappearing from view, only to re-appear again on an 11 month cycle. Although Mira was once a star very similar to the sun, it is now in its death throes as it loses its dusty outer layers at a rate of one Earth-mass every seven years. If Mira were a single star, all this material would travel into outer space. However, like two out of every three star systems, Mira has a companion star that orbits around it, in this case with a period of about 1.000 years. This companion, Mira B, has a gravitational field that catches nearly one percent of the material lost from Mira A. By using specialized high-contrast techniques at the 10-meter Keck I telescope in Hawaii and the 8-meter Gemini South telescope in Chile, Michael Ireland’s team discovered heat radiation coming not from Mira B itself, but also from a location offset from Mira B by a distance equivalent to Saturn’s orbit.
First Planet-Forming Disk Found in the Environment of a Dying Star