For the first time, astronomers have seen evidence of an aging star consuming its own planet. Such events are not uncommon as aging stars expand in size, engulfing nearby planets. But the events happen relatively quickly on a cosmological time scale and it is considered unlikely for one to be observed directly.
The star in question is known as a red giant. Such stars begin with a mass about the same as that of the Earth's sun. As they age, the hydrogen fusion reactions in their core become less efficient and most of the fusion is transferred to the outer shell of gases. The increased fusion makes the shell hotter and as much as 1,000 times brighter than normal, causing the diameter of the star to expand continually until its radius reaches a size equivalent to the Earth's distance from the sun.
A team headed by astronomer Alexander Wolszczan of Penn State University used the 9.2-meter (362-inch) Hobby-Eberly Telescope at the McDonald Observatory in the Davis Mountains of Texas to study a red giant star named BD+48 740. They reported in Astrophysical Journal Letters that the star has a diameter about 11 times that of our sun. Spectroscopy showed that the star contains an abnormally high amount of lithium, a rare element created primarily during the Big Bang.