Free Astronomy Magazine July-August 2016

SPACE CHRONICLES Building on past observations of the white dwarf called SDSSJ1043+0855 (the dead core of a star that origi- nally was a few times the mass of the Sun), which has been known to be gobbling up rocky material in its orbit for almost a decade, the team used Keck Observatory’s HIRES in- strument fitted to the 10-meter Keck I telescope as well as data from the Hubble Space Telescope to mea- sure and characterize the material being accreted by the star. What they found is that the white dwarf appears to be accreting the outer-most layers of a differenti- ated, rocky extrasolar body (i.e., the surface of massive, planet-like ob- ject) from its ex- tant planetary sys- tem. “Spectroscopic ob- servations of the white dwarf allow- ed us to measure the abundances of the rocky material as it is being ac- creted and filtered through the star’s atmosphere in real time,” Melis said. “ We can see the material that used to make up this planet being ac- creted and replen- ished on a daily timescale. What we see is what the rock was made of.” This may be the single best tool astronomers have to determine the chemical composi- tion of planets, according to Luca Rizzi, Support Astronomer at Keck Observatory. Planet-devouring star reveals possible limestone crumbs A group of researchers using the W. M. Keck Observatory have discovered a planet-like body that may have been encrusted in limestone and is having its surface layers devoured by its deceased host star. In addition to extending a rela- tively new method of determining the chemical composi- tion of planets to examine their in- ternal structure, the team found that the rocky ma- terial being accret- ed by the star could be com- prised of minerals that are typically associated with marine life pro- cesses here on Earth. The team – comprised of Carl Melis of University of California, San Diego and Patrick Dufour of the Université de Mon- tréal – announced their findings at the 228 th meeting of the American Astronomical Society. by Keck Observatory T he Keck II (twin of the Keck I) 10-meter, 36-segment mirror is seen from a bird's eye view nearly 30 meters above. [Laurie Hatch]