V838 Monocerotis revisited: light echo imitates art
HUBBLE EUROPEAN SPACE AGENCY INFORMATION CENTRE
Posted: March 4, 2004
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The Hubble Space Telescope's Advanced Camera for Surveys captured this
stunning image of an expanding halo of light around V838 Monocerotis on
February 8, 2004. [Click to enlarge.]
Image credit: NASA, the Hubble Heritage Team (AURA/STScI) and ESA
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"Starry Night", Vincent van Gogh's famous painting, is renowned for its
bold whorls of light sweeping across a raging night sky. Although this
image of the heavens came only from the artist's restless imagination,
a new picture from the NASA/ESA Hubble Space Telescope bears remarkable
similarities to the van Gogh work, complete with never-before-seen spirals
of dust swirling across trillions of kilometres of interstellar space.
This image, obtained with the Advanced Camera for Surveys on February 8,
2004, is Hubble's latest view of an expanding halo of light around a distant
star, named V838 Monocerotis (V838 Mon). The illumination of interstellar
dust comes from the red supergiant star at the middle of the image, which
gave off a flashbulb-like pulse of light two years ago. V838 Mon is located
about 20,000 light-years away from Earth in the direction of the constellation
Monoceros, placing the star at the outer edge of our Milky Way galaxy.
Called a light echo, the expanding illumination of a dusty cloud around the
star has been revealing remarkable structures ever since the star suddenly
brightened for several weeks in early 2002. Though Hubble has followed the
light echo in several snapshots, this new image shows swirls or eddies in the
dusty cloud for the first time. These eddies are probably caused by turbulence
in the dust and gas around the star as they slowly expand away. The dust and
gas were likely ejected from the star in a previous explosion, similar to the
2002 event, which occurred some tens of thousands of years ago. The surrounding
dust remained invisible and unsuspected until suddenly illuminated by the
brilliant explosion of the central star two years ago.
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HST images of V838 Monocerotis taken in 2002 on May 20 (upper left),
September 2 (upper right), October 28 (lower left) and December 17 show
the dramatic changes in size and structure leading up to the February 8,
2004 image above.
[Click to enlarge.]
Image credit: NASA, the Hubble Heritage Team (AURA/STScI) and ESA
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The Hubble Space Telescope has imaged V838 Mon and its light echo several times
since the star's outburst in January 2002, in order to follow the constantly changing
appearance of the dust as the pulse of illumination continues to expand away from
the star at the speed of light. During the outburst event, the normally faint
star suddenly brightened, becoming 600,000 times more luminous than our Sun. It
was thus one of the most luminous stars in the entire Milky Way, until it faded
away again in April 2002. The star has some similarities to novae, which suddenly
increase in brightness due to thermonuclear explosions at their surfaces; however,
the detailed behaviour of V838 Mon, in particular its extremely red colour, has
been completely different from any previously known nova.
Nature's own piece of performance art, this structure will continue to change
its appearance in coming years as the light from the stellar outburst continues
to propagate outward and bounce off more distant black clouds of dust.
Astronomers expect the echoes to remain visible for at least the rest of the
current decade.
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