The Absolute Cosmos: Solved! 16 year old mystery of Blue Ring nebula
The Blue Ring nebula is composed of expanding hydrogen gas (blue) expanding from a central star- a remnant core of a stellar merger. Red filaments are shockwave filaments from the merging event. Image credit: NASA/JPL-Caltech/M. Seibert (Carnegie Institution for Science)/K. Hoadley (Caltech)/GALEX Team
With the help of NASA’s Galaxy Evolution Explorer (GALEX), scientists first spotted Blue Ring nebula in 2004. It was like something never been observed before in Milky Way galaxy.
Object appeared like a large, faint gas blob with a star at centre. Galaxy Evolution Explorer’s ultraviolet imagery showed the blob in blue colour. Blob does not emit visible light, so it can’t be seen with human eye.
Follow up observations revealed two thick rings within it, this prompted scientists to name it the Blue Ring nebula. The central star is called TYC 2597–735–1.
Now, scientists have revealed new evidence that could help in solving the mystery surrounding its structure and evolution.
Mostly stars in our galaxy are in binary systems, orbiting each other. When they come too close to each other, the result is stellar merging event which leads to systems’ demise.
When one star engulfs its orbiting companion, this causes the companion to spiral inward until the two stars collide. While the companion star loses its orbital energy, it ejects material outward at very high speeds.
In order to test this theory, scientists performed spectroscopic observations of the Blue Ring nebula with two large ground based telescopes: W. M. Keck Observatory in Hawaii and Hobby-Eberly Telescope at McDonald Observatory in Texas.
The observations allowed scientists to determine that central star is inflated and signatures of accretion probably from surrounding debris disk can also be seen.
The spectroscopic observation data combined with scientific models shows that the ring nebula is consistent with the process of merging binary star systems. This suggests that inward spiralling star was probably a low mass star.
The Blue Ring nebula is the only cosmic object where a clear view of the central star can be seen. This allow scientists to observe the properties of central stellar remnant.
All other merging binary systems observed before have been enveloped by opaque clouds and dust. Thus, obstructing the clear view of central stellar remnant.
To get more insights of the Blue Ring nebula, scientists also used archived data from NASA’s Spitzer Space Telescope and Wide-field Survey Explorer (WISE). The data showed surplus infrared emissions around the central star.
The data suggests that the central star is surrounded by a disk of dust which absorbs the star light and radiates it back in the infrared.
This disk of dust cut the cloud of debris surrounding the central in half, thus creating two cone shaped clouds extending in opposite directions with one of the cone pointing towards Earth making it look like a ring.
For more information: A blue ring nebula from a stellar merger several thousand years ago