Image Tour: Star V838 Monocerotis

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with NASA’s Universe of Learning partners: Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, NASA Jet Propulsion Laboratory, and Sonoma State University

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Text, V838 Monocerotis Image Tour

 

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Fast Facts. Location, Constellation Monocerotis. Distance from Earth, 20,000 light-years. Size, 13.7 light-years across. Telescope, Hubble Space Telescope

 

In January 2002, a deceptively ordinary star suddenly flashed to at least 4000 times its previous brightness.

 

For several weeks, the red supergiant star V838 Monocerotis was the most brilliant star in the Milky Way.

 

The brightness faded, but as the light from the flash travels through space, it progressively illuminates the layers of dust surrounding the mysterious star.

 

This event is called a "light echo."

 

Tour Stop, Central Star.

 

A star that occasionally brightens dramatically is a nova.

 

Scientists aren't sure about the roots of V838 Monocerotis' behavior, but nova flashes usually occur when the gravity of a dense white dwarf pulls enough material from a nearby red supergiant to cause a reaction on the dwarf surface.

 

So V838 Monocerotis may actually be a two-star system.

 

Tour Stop, Gas and Dust. A nova is like a flashbulb going off in space - it illuminates everything around it.

 

In this case, we can clearly see the gas and dust that drifts through space near V838 Monocerotis.

 

Space is filled with gas and dust like this, but normally we can't see it, since it doesn't give off any light.

 

Tour Stop, Light Echo. As the light from star V838 Monocerotis moves outward, it illuminates more and more of the gas and dust around the star.

 

Hubble observed the star repeatedly to observe these "light echoes."

 

Let's start from the beginning. May 20, 2002

 

Four months after star V838 Monocerotis' outburst,, the flash illuminates the first layer of dust around the star.

 

Light traveling makes it look like the star itself is expanding, but this isn't the case. September 2, 2002

 

The light was already present but invisible in the darkness.

 

Each time Hubble observes the star, different, thin sections of dust are visible as the pulse of light from the initial explosion continues to travel. October 28, 2002

 

The light moves at a speed of 186,000 miles per second. December 17, 2002

 

Two years after the initial flash, the star continues to reveal surrounding dust layers. October 24, 2004

 

To get a sense of the scale involved, consider that light can travel from Earth to Pluto in about four hours, yet it's taken over two years to reach these layers of dust.

 

Notice that all the prominent stars in this image have a spiky, cross-shaped appearance, including V838 Monocerotis. Tour Stop, Foreground Stars.

 

These are stars in our galaxy.

 

Their distinctive shape is caused by light reflecting off the struts inside the telescope.

 

Central Star, Gas and Dust, Light Echo, Foreground Stars