Herschel Helps Solve Mystery of Cosmic Dust Origins

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News release: 2011-204 July 7, 2011

Herschel Helps Solve Mystery of Cosmic Dust Origins

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-204&cid=release_2011-204

PASADENA, CALIF. -- 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.

A new view from NASA's Hubble Space Telescope showing how supernova 1987A has recently
brightened is at http://hubblesite.org/newscenter/archive/releases/2011/21 .

Initially, astronomers weren't sure if the Herschel telescope could even see this supernova remnant.
Herschel detects the longest infrared wavelengths, which means it can see very cold objects that emit
very little heat, such as dust. But it so happened that SN 1987A was imaged during a Herschel survey
of the object's host galaxy -- a small neighboring galaxy called the Large Magellanic Cloud (it's
called large because it's bigger than its sister galaxy, the Small Magellanic Cloud).

After the scientists retrieved the images from space, they were surprised to see that SN 1987A was
aglow with light. Careful calculations revealed that the glow was coming from enormous clouds of
dust -- consisting of 10,000 times more material than previous estimates. The dust is minus 429 to
minus 416 degrees Fahrenheit (about minus 221 to 213 Celsius) -- colder than Pluto, which is about
minus 400 degrees Fahrenheit (204 degrees Celsius).

"Our Herschel discovery of dust in SN 1987A can make a significant understanding in the dust in the
Large Magellanic Cloud," said Mikako Matsuura of University College London, England, the lead
author of the Science paper. "In addition to the puzzle of how dust is made in the early universe,
these results give us new clues to mysteries about how the Large Magellanic Cloud and even our own
Milky Way became so dusty."

Previous studies had turned up some evidence that supernovae are capable of producing dust. For
example, NASA's Spitzer Space Telescope, which detects shorter infrared wavelengths than
Herschel, found 10,000 Earth-masses worth of fresh dust around the supernova remnant called
Cassiopea A. Hershel can see even colder material, and thus the coldest reservoirs of dust. "The
discovery of up to 230,000 Earths worth of dust around SN 1987A is the best evidence yet that these
monstrous blasts are indeed mighty dust makers," said Eli Dwek, a co-author at NASA Goddard
Space Flight Center in Greenbelt, Md.

Other authors include M. Otsuka, J. Roman-Duval, K.S. Long and K.D. Gordon, Space Telescope
Science Institute, Baltimore, Md.; B. Babler, University of Wisconsin, Madison; M.J. Barlow,
University College London, United Kingdom; C. Engelbracht, K.A. Misselt and E. Montiel,
University of Arizona, Tucson; K. Sandstrom, Max Planck Institut für Astronomie, Heidelberg,
Germany; M. Lakićević and J.Th. van Loon, Keele University, United Kingdom; G. Sonneborn,
Goddard Space Flight Center, Greenbelt, Md.; G.C. Clayton, Louisiana State University, Baton
Rouge; P. Lundqvist, Stockholm, Sweden; T. Nozawa, University of Tokyo, Japan; S. Hony, K.
Okumura and M. Sauvage, the French Alternative Energies and Atomic Energy Commission, France.

Herschel is a European Space Agency cornerstone mission, with science instruments provided by
consortia of European institutes and with important participation by NASA. NASA's Herschel Project
Office is based at NASA's Jet Propulsion Laboratory. JPL contributed mission-enabling technology
for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the
Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena,
supports the United States astronomical community. Caltech manages JPL for NASA.

More information is online at http://www.nasa.gov/herschel and
http://www.esa.int/SPECIALS/Herschel/index.html .

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