Herschel Helps Solve Mystery of Cosmic Dust Origins

This plot shows energy emitted from a supernova remnant called SN 1987A. Previously, NASA's Spitzer Space Telescope detected warm dust around the object. This dust formed before the explosion, but as shock waves impacted pre-existing dust grains, they heated up. In contrast, the Herschel Space Observatory, which sees longer wavelengths of infrared light than Spitzer, detected cold dust that formed after the explosion. A large amount of this dust is made from the gas ejected by the supernova itself. The formation of this dust started at least two years after the explosion, while gaseous material slowly expanded from the center of the supernova remnant. Dust continued to cool and release light at the longer infrared wavelengths Herschel sees.



New observations from the infrared Herschel Space Observatory reveal that an exploding star expelled the equivalent of between 160,000 and 230,000 Earth masses of fresh dust. This enormous quantity suggests that exploding stars, called supernovae, are the answer to the long-standing puzzle of what supplied our early universe with dust.




"This discovery illustrates the power of tackling a problem in astronomy with different wavelengths of light," said Paul Goldsmith, the NASA Herschel project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who is not a part of the current study. "Herschel's eye for longer-wavelength infrared light has given us new tools for addressing a profound cosmic mystery."



Herschel is led by the European Space Agency with important contributions from NASA.



Cosmic dust is made of various elements, such as carbon, oxygen, iron and other atoms heavier than hydrogen and helium. It is the stuff of which planets and people are made, and it is essential for star formation. Stars like our sun churn out flecks of dust as they age, spawning new generations of stars and their orbiting planets.



Astronomers have for decades wondered how dust was made in our early universe. Back then, sun-like stars had not been around long enough to produce the enormous amounts of dust observed in distant, early galaxies. Supernovae, on the other hand, are the explosions of massive stars that do not live long.



The new Herschel observations are the best evidence yet that supernovae are, in fact, the dust-making machines of the early cosmos.



"The Earth on which we stand is made almost entirely of material created inside a star," explained the principal investigator of the survey project, Margaret Meixner of the Space Telescope Science Institute, Baltimore, Md. "Now we have a direct measurement of how supernovae enrich space with the elements that condense into the dust that is needed for stars, planets and life."



The study, appearing in the July 8 issue of the journal Science, focused on the remains of the most recent supernova to be witnessed with the naked eye from Earth. Called SN 1987A, this remnant is the result of a stellar blast that occurred 170,000 light-years away and was seen on Earth in 1987. As the star blew up, it brightened in the night sky and then slowly faded over the following months. Because astronomers are able to witness the phases of this star's death over time, SN 1987A is one of the most extensively studied objects in the sky.