Hubble Offered A Rare, Ring-Side Seat At The Death Of A Star
During its impressive 25 years the Hubble Space Telescope has captured numerous remarkable views of the universe, providing astronomers with a wealth of data for making astounding discoveries. Of all the beautiful astronomical objects observed by Hubble one of the most awe-inspiring is the massive, dying star V838 Moncerotis.
Hubble’s longevity has provided astronomers with a series of detailed images of V838 Mon captured between May 2002 and September 2006: the result is a fascinating “time-lapse” that uniquely illuminates the evolution of this massive, super-giant star. Hubble’s exceptionally sharp focus of V838 Mon offered a ring-side seat at the slow death of the star and excited astrophysicists with the chance to study the physics of the light, matter and microscopic dust of the interstellar medium.
V838 Monocerotis in April 2002, as the first flash of bright blue light emanates from the star. NASA\ESA\H E Bond
V838 Mon is about 20,000 light-years away from Earth, in the direction of the constellation of Monoceros (the unicorn). This enormous distance places the star at the outskirts of our galaxy, the Milky Way. In 2002 the star underwent an enigmatic and spectacular brightening, briefly becoming one of the most luminous stars in the Galaxy.
This stellar flash blasted out radiation at a rate 600,000 times the output of our sun. The astounding Hubble images taken over the following years reveal the flash of light illuminating the shells of dust and gas that surround the star.
At first glace, the ring of colour suggests we are witnessing the gradual expansion of the ejected shell of the exploding star. But in fact what are seeing is an extraordinary “light echo”.
As light from the powerful flash propagates outward at 300,000km per second, it travels through successive rings of dust that surround the star. Some light is scattered by micron-sized dust particles in the dust clouds, reflected back towards the telescope and Earth. The scattered light has travelled a greater distance than the light that arrived directly from the original flash, and so arrives later. This light echo is the optical analogue of the more familiar sound echo, generated when for example thunder bounces of surrounding mountain-sides.
The route the ‘light echo’ took, from star to telescope. NASA\ESA\A Feild
The light echo discovered by Hubble reveals successive layers of matter and dust, spanning light-years across. The images betray earlier phases in the life of a now ageing, red super-giant star. The latest images in this time-lapse from 2005 and 2006 show an object around about six light-years in diameter, and reveal the turbulent and intricate structure of the interstellar medium, a region where it seems magnetic fields thread the space between stars.
All of these sharp images were taken using the Advanced Camera for Surveys (ACS), which had only just been installed on Hubble during a service mission in March 2002. The images approach true colours by combining data filtered to isolate blue, green and infrared light.
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