Friday, November 10, 2017

Light from Supernova Bouncing Off Giant Dust Cloud

Light from a supernova explosion in the nearby starburst galaxy M82 is reverberating off a huge dust cloud in interstellar space.  The supernova, called SN 2014J, occurred at the upper right of M82, and is marked by an “X.” The supernova was discovered on Jan. 21, 2014.  The inset images at top reveal an expanding shell of light from the stellar explosion sweeping through interstellar space, called a “light echo.” The images were taken 10 months to nearly two years after the violent event (Nov. 6, 2014 to Oct. 12, 2016). The light is bouncing off a giant dust cloud that extends 300 to 1,600 light-years from the supernova and is being reflected toward Earth. Credit: NASA, ESA, and Y. Yang (Texas A&M University and Weizmann Institute of Science, Israel)  Acknowledgment: M. Mountain (AURA) and The Hubble Heritage Team (STScI/AURA)

Voices reverberating off mountains and the sound of footsteps bouncing off walls are examples of an echo. Echoes happen when sound waves ricochet off surfaces and return to the listener. Space has its own version of an echo. It’s not made with sound but with light, and occurs when light bounces off dust clouds.

The Hubble telescope has just captured one of these cosmic echoes, called a “light echo,” in the nearby starburst galaxy M82, located 11.4 million light-years away. A movie assembled from more than two years’ worth of Hubble images reveals an expanding shell of light from a supernova explosion sweeping through interstellar space three years after the stellar blast was discovered. The “echoing” light looks like a ripple expanding on a pond. The supernova, called SN 2014J, was discovered on Jan. 21, 2014.

A light echo occurs because light from the stellar blast travels different distances to arrive at Earth. Some light comes to Earth directly from the supernova blast. Other light is delayed because it travels indirectly. In this case, the light is bouncing off a huge dust cloud that extends 300 to 1,600 light-years around the supernova and is being reflected toward Earth.

So far, astronomers have spotted only 15 light echoes around supernovae outside our Milky Way galaxy. Light echo detections from supernovae are rarely seen because they must be nearby for a telescope to resolve them.

Credit: hubblesite.org

2 comments:

  1. Thinking about how those photons coming from the expanding ring are older the farther out they are from the center, I wonder if there are things out there that we see at two distinctly different ages simultaneously.

    Gravitational lensing, for instance, could provide a second, much older image (though distorted I guess) of a galaxy, I imagine.

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