supernova remnant sn 1006 - hubblesite

Taken from: Hubble 2008: Science Year in Review

Produced by NASA Goddard Space Flight Center and the Space Telescope Science Institute.

The full contents of this book include more Hubble science articles, an overview of the telescope, and more. The complete volume and its component sections are available for download online at:

www.hubblesite.org/hubble_discoveries/science_year_in_review

National Aeronautics and Space Administration

Supernova Remnant SN 1006

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Hubble 2008: science Year in review

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This very thin section of a supernova remnant appears as a ribbon because Hubble is looking almost exactly along the edge of the expand-ing bubble, an object approximately 60 light-years across. The remnant was the product of a stellar explosion that occurred more than 8,000 years ago, but was only seen by observers in the year 1006 A.D., as its light took 7,000 years to travel the distance to Earth.

Supernova Remnant SN 1006

More than 8,000 years ago, the cataclysmic explosion of a nearby star sent a shock wave racing outward through space

at nearly 20 million miles an hour. Found in what is now the southern constellation of Lupus, the Wolf, the explosion—a

supernova—completely annihilated the star. The shock wave heated all the interstellar gas and dust in its path. Today, a

delicate, red-colored “ribbon” of gas appears to be floating alone in space in the direction of the former star. This “ribbon,”

in reality, is just a small portion of a large bubble of material called a supernova (SN) remnant that surrounds the site of the

explosion.

Known as SN 1006, the spherically-shaped stellar remnant is invisible at optical wavelengths except for this ribbon-like

structure. Radio telescopes discovered its presence in the 1960s, detecting a nearly circular ring of material at the location

of the supernova. In 1976, astronomers used the 4-m Blanco telescope at the Cerro Tololo Inter-American Observatory in

Chile to observe a faint optical glow from a small region on the northwest edge of the radio ring. A small slice of that region

is shown in detail in the Hubble image. The thin strand corresponds to a part of space where the shock wave is sweeping

up tenuous hydrogen gas, heating it, and causing it to radiate in visible light.

The twisting ribbon is indeed an optical illusion. It appears ribbon-like because it is observed almost exactly along the edge

of the expanding bubble. The strand is actually more like a crinkled sheet of paper or cloth viewed from the side. Slight

ripples in the sheet produce the sharp edges, and more diffuse light fills in between them.

Over the past few decades, astronomers have made observations of the SN 1006 remnant in many different wavelengths

of light. The presence of optical emission along only one section of this huge, expanding bubble tells astronomers that

neutral hydrogen gas is present in significant quantities only along this portion of the shell.

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The remnant’s expansion has now

slowed to only 6 million miles an hour,

or 100,000 miles a minute. Even at

this tremendous speed, it takes years

between observations to detect any

motion of the ribbon filament against

the background stars because it is so

distant—approximately 7,000 light-

years.

The stellar explosion was seen in 1006

A.D. by observers from Africa to the Far

East, although in reality, the star had

detonated 7,000 years before—the

travel time for the event’s light to reach Earth. It was probably the brightest “star” ever observed by humans. Over the course of

a few days, the star became brighter than the planet Venus. For several weeks, people could see it with unaided eyes—even

during the day—and it remained visible in dark skies for approximately two-and-a-half years before fading away. It is likely that

the supernova’s progenitor star was a white dwarf, the burned-out relic of an ordinary star. The dead star had probably become

unstable after siphoning too much matter off an orbiting companion star.

As seen from the ground, the ribbon-like filaments of the SN 1006 remnant seem to float in space. Hubble’s high resolution image provides a close-up view of a 5 light-year segment of the structure, less than a third of its overall length.

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The Hubble image is a composite of hydrogen-light observations taken with the Advanced Camera for Surveys in February

2006, and the Wide Field Planetary Camera 2 in April 2008. The supernova remnant was assigned a red hue in the image

to correspond to a prominent spectral line of hydrogen, which lies in the red portion of the electromagnetic spectrum. The

orange-colored dots and smudges in the image are distant background galaxies, while the white points of light are stars

in our Milky Way galaxy.

This image is a composite of visible (or optical), radio, and x-ray data of the full shell of the super-nova remnant from SN 1006. Only a small linear filament in the northwest corner of the shell is visible in the optical data. The shell has an angu-lar size of roughly 30 arcminutes (0.5 degree, or about the size of the full Moon). The small orange box along the bright filament at the top of the im-age corresponds to the dimensions of the Hubble image seen on page 82.

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The expanding shell of a supernova remnant is like a translucent bubble of gas with surface ripples and disturbances caused by varying gas densities. The structure seen by Hubble corresponds to a part of space where the shock wave is sweeping up tenuous hydrogen gas, heating it, and causing it to radiate in visible light. When viewed from the side, this flattened sheet of heated gas looks like a delicate, twisting ribbon.

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Further Reading

Blair, W.P., et al., “Hubble Space Telescope Imaging of the Primary Shock Front in the Cygnus Loop Supernova Remnant,” The Astronomical Journal, 129, 2268–2280, 2005.

Goldstein, B.R., and H.P. Yoke, “The 1006 Supernova in Far Eastern Sources,” The Astronomical Journal, 70, 748–753, 1965.

Raymond, J., et al., “The Preshock Gas of SN 1006 from Hubble Space Telescope Advanced Camera for Surveys Observations,” The Astrophysical Journal, 659, 1257–1264, 2007.

Reddy, F., “Supernova Aftermath: A Supernova’s Impact Lives on Long Beyond Its Fading Light,” Astronomy, 34(6), 42–43, 2006.

Semeniuk, I., “Blasts from the Past: The Dazzling Light of Long-gone Supernovae Is Still Visible If You Know Where to Look,” New Scientist, 194, 46–50, 2007.

van den Bergh, S., “The Optical Remnant of the Lupus Supernova of 1006,” The Astrophysical Journal, 208, L17, 1976.

Winkler, P.F., “SN 1006: A Thousand-year Perspective,” Highlights of Astronomy, 14, 301–302, 2007.

William P. Blair is an astrophysicist and research professor in the Department of Physics

and Astronomy at The Johns Hopkins University. His main scientific interests lie in the ar-

eas of gaseous nebulas and the interstellar medium, but his particular focus is supernova

remnants. He has used Hubble to observe various supernova remnants, both in the Milky

Way and in nearby galaxies, and he was instrumental in the study of the SN 1006 rem-

nant. He has been Chief of Operations for the Far Ultraviolet Spectroscopic Explorer (FUSE)

project at Johns Hopkins since 2000. Prior to FUSE, he worked for many years on the

Hopkins Ultraviolet Telescope, which flew twice on the Space Shuttle. He was born in Garden

City, Michigan, a suburb of Detroit. Dr. Blair earned a B.A. in mathematics and physics

from Olivet College in Olivet, Michigan. He obtained an M.S. and Ph.D. in astronomy from

the University of Michigan at Ann Arbor in 1981 and spent three years at the Harvard-

Smithsonian Center for Astrophysics prior to coming to Hopkins. (Photo credit: W. Kirk,

the Johns Hopkins University)

supernova remnant sn 1006 - hubblesite

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