Frontiers of Astronomy Community Lectures

Are we made of stardust? This is the question Manuel Peimbert answered during his Frontiers of Astronomy Community Lecture about the origin of the elements delivered on April 18 at the IfA Manoa auditorium. As you might have guessed, the answer is "yes."

Peimbert explained that hydrogen, the lightest element, as well as some of the helium in the Universe, formed during the first four minutes after the Big Bang, the giant explosion that created the Universe. Hydrogen and helium make up about 98 percent of all matter. Stars the size of our Sun convert hydrogen to helium, and then eventually, helium to carbon. When these stars die, they leave a cloud of dust and gas (known by the misnomer "planetary nebula") that expands at the rate of 10 kilometers per second (over 22,000 mph) around a small white dwarf star.

Larger stars, those with at least eight times the mass of the Sun, make heavier elements, including oxygen, neon, magnesium, silicon, and iron, as well as helium and carbon. When these giant stars die in a supernova explosion that creates even heavier elements, they leave a very dense neutron star and a cloud of gas and dust that expands at speeds of at least 2,000 kilometers per second (over 4 million mph).

The gas and dust sent into the interstellar medium by dying stars gets recycled into a new generation of stars. That is why newer generations of stars have more heavy elements. It is around the stars with greater amounts of heavier elements that planets are most likely to form. Everything in this room, including you, Peimbert explained, is made up of elements that formed from stardust.

Bill Bottke of the Southwest Research Institute, Boulder, Colorado, will give the next Frontiers of Astronomy Community Lecture on Tuesday, June 27 at 7:30 p.m. in the IfA Manoa Auditorium. The topic will be "CSI Solar System: Using Computer Models to Investigate the Nature of Comets and Asteroids."

http://www.ifa.hawaii.edu/specialevents/