Herschel Helps Solve Mystery of Cosmic Dust Origins

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Herschel Helps Solve Mystery of Cosmic Dust Origins
Jet Propulsion Laboratory
July 07, 2011

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. Lakicevic 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 .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney...@jpl.nasa.gov

2011-204