Like a flashbulb, a red giant star known as V838 Monocerotis lit up its environment about two years ago, and astronomers have been puzzling over snapshots taken ever since.
This latest in a series of images by the Hubble Space Telescope shows the flash of light illuminating gas and dust farther from the star than had been seen in previous images as the light continues to race outward at, well, at the speed of light.
The latest picture, captured Feb. 8 and released today, shows new detail. Swirls
or eddies are for the first time visible in the dusty cloud. These eddies are
probably created by turbulence in the cloud, related to its own expansion, astronomers
said.
The cloud is what allows the light echo to play out. The gas and dust in the
cloud was ejected in a previous eruption of the star tens of thousands of years
ago. It is expanding slowly, and as the more recently unleashed flash of light
passes through the cloud -- moving at a much more rapid clip -- it continually
illuminates new regions in a growing circle.
In essence, space around the star is changing, but our view of it is changing
even faster, as the light echoes off the structures, reflected our way. Of course,
because V838 Monocerotis is 20,000 light-years away, everything we're seeing
now actually happened 20,000 years ago in the time frame of the star.
What puzzles astronomers is not the light echo. They've seen those before.
But the star has not erupted in a manner consistent with other known types of
stars. Unlike a nova, an event in which a star ejects its outer layers, this
star simply expanded when the flash bulb went off. The continuing observations
aim to understand what's going on.
