Extragalaxtic Planet Found

Scientists have recently (meaning in December of last year) discovered a planetary system that appears to have originated in another galaxy. The star, named HIP 13044, is part of the Helmi Stream, a satellite galaxy that was absorbed into the Milky way 6 to 9 billion years ago. It contains much less of the heavier elements than our sun does, and it is about the same size, but it is much older; scientists predict that it has already passed it’s red giant stage and contracted back down, and it is now burning helium.

The planet, which has the mass of about 1.25 Jupiters, orbits closer than Mercury does to our sun. This is surprising, because if the star had at one time been a red giant, it would have swallowed up a planet orbiting as close as this planet does. Researchers observing the planet hypothesize that the star’s expansion into a red giant caused a chaotic reaction with other planets that may have been orbiting the star, speeding its rotation, and knocking the large planet into a closer orbit. In any case, scientists hope to learn more about the contents of other galaxies by determining the composition of HIP 13044 and its planet.