Science & Tech

Molecular cloud has a heartbeat

2 min read

Dark molecular cloud Barnard 68 seems to pulsate

Barnard 68, located 300 light-years away in the constellation Ophiuchus, is a typical example of small, dark molecular clouds known as Bok Globules. Such dense, cold clouds of dust and gas appear black in photos because the dust blocks visible light from background stars. Molecular clouds are stellar nurseries. Young stars form from collapsing molecular clouds. Barnard 68, however, is a stable cloud containing no newborn stars. Now astronomer Charles Lada of the Harvard-Smithsonian Center for Astrophysics and colleagues have discovered that the dark molecular cloud known as Barnard 68 seems to pulsate like a heavenly tribute to Saint Valentine. Barnard 68 is the only molecular cloud known to pulsate in this manner. Barnard 68 holds as much material as one and a half Suns, chilled to a temperature of only 10 degrees above absolute zero (-440 degrees F). It is one of the coldest objects in the Universe. Appropriately for such a frigid temperature, it pulsates very slowly, considerably more slowly than the heart of an earthbound lizard on a cold fall morning. Barnard 68 spans about 24,000 times the average distance between the Earth and the Sun, or about two trillion miles. If our Sun were placed at the center of Barnard 68, the cloud would extend out to 300 times the orbit of Pluto. Our solar system would be a lonely place, because the cloud’s thick dust would obscure light from the surrounding stars and galaxies that fill the cosmos. Our night sky would be as black as coal, showing only the occasional pinpoint of light from the other nearby planets.