Celestial Tour: A Celestial Light Echo

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An obscure star called V838 Monocerotis shone steadily until a sudden mysterious outburst made it, for a time, the brightest star in our galaxy.

Produced by: Space Telescope Science Institute, Office of Public Outreach

  • Pre-Outburst Image of V838 Monocerotis: Anglo-Australian Observatory
  • Outburst Image of V838 Monocerotis: U.S. Naval Observatory
  • Hubble Images of light echo from V838 Monocerotis: NASA, ESA, H. E. Bond (STScI)
  • Light path animation: G. Bacon
  • Time-lapse animation: NASA and L. Barranger
  • Written and designed by Bryan Preston
  • Music from John Serrie


 White title text on a black background, a celestial light echo. 

A photo of a star field, labeled May 1989. An arrow points to a specific star near the middle of the star field. Text, an obscure star called V838 Monocerotis shone steadily. 

A photo of the same star field labeled March 2002 appears beside the first photo but with the indicated star appearing bigger and glowing in a reddish color. Text, Until a sudden mysterious outburst made it, for a time, the brightest star in our galaxy, 600,000 times more luminous than our Sun. 

An animation shows the star surrounded by seven cloud shapes. Seven yellow arrows burst from the star toward the clouds, then the arrows fall downwards from the clouds. Text, The first light to reach us came directly from the star. Later, light reflected by previously unseen clouds of dust around the star began to arrive. This caused an amazing illusion. 

A photo labeled May 20, 2002, showing the red star surrounded by a thick glowing creamy white halo. Text, a light echo, the first seen in our galaxy since 1936, captured here by NASA's Hubble Space Telescope. The previous animation reappears. Text, Hubble's first view showed the star and the inner dust clouds around it. Light reflected from outer dust shells had not yet reached us. 

Month after month, more light arrived. Three photos appear consecutively, showing the expanding layers of dust clouds surrounding the red star. They are dated September 2, October 28, and December 17, 2002. 

Text, The arriving light revealed shells of dust farther out from the star, causing the illusion that the clouds are moving away from the star at faster than light speed. A 7-month time lapse shows the revelation of the brownish dust cloud layers surrounding the star. The movie gives the appearance that the dust cloud layers are expanding away from the star. 

Text, In fact, the clouds may be hardly moving at all. The photo from December 17, 2002 remains on screen. 

The time lapse movie is replayed. 

Text, The echo will probably continue to grow for several more years. 

The previous animation reappears, showing the yellow arrows falling from the clouds, flashing as they reach the edge of the frame. Text, Then, as light from clouds behind the star reaches us, the echo will appear to shrink and finally disappear. The animation disappears. 

The bright red star and surrounding brown dust clouds appear large on screen, along with bright background stars. Text, The clouds that surround this star were probably ejected from it in previous outbursts. 

As light from the flash sweeps into space, astronomers can view continuously changing cross-sections of the dust shells, building a 3D model of the space around the star, learning more about how aging stars spend their final years. 

Space Telescope Science Institute, Office of Public Outreach. Anglo-Australian Observatory, U.S. Naval Observatory, G. Bacon, NASA, L. Barranger, E.S.A, H.E. Bond, Jonn Serrie, Bryan Preston. 

For more information, visit hubble site dot org, press release 2003-10.