Hubble sees optical echoes from a hyper red giant

In 2002, the red variable giant temporarily became the brightest star in the Milky Way. Hubble watched this star for several years and saw a unique phenomenon: optical echoes.

V838 Monocerotis is a binary star located 19,000 light years from Earth. Red Heavy Star is a true giant. For example, the radius of a star is 1570 solar radii (or 1570 times the radius of the sun). This makes it one of the largest known stars that we know of.

In January 2002, the massive giant – which is barely visible – quickly became 600,000 times brighter than the Sun. A few years ago, there was a big explosion, but it went somewhat unnoticed. Scientists believe that a massive giant swallowed a large planet or a small star. The light from the eruption then traveled through a cloud of dust surrounding the star. It looks as if the V838 Monocerotis is releasing stuff, but that’s not the case. Here we see the expanding flash illuminating the dust clouds already around the star.

Hubble took several photos of the V838 Monocerotis from 2002 to 2006, which led to the next series. It is rare for astronomers to see a celestial body change in such a short time. The images clearly show how the light from the star travels through the dust clouds. The light emitted first – when the star is hotter – appears bluer. Hence the gas spots appear to have blue edges.

The gas fragments in the image above are several trillion kilometers long. In the image on the right, the light echo is six light-years across. Thus, the resonance of light is wider than the distance from the Sun to the nearest star: Proxima Centauri.

When the photos are pasted one by one in time interval, a beautiful video is created. This video is not entirely realistic, because scenes are simulated between images, but it shows how a star transforms in a short time.