A new study by the National Aeronautics and Space Administration (NASA) deciphered the mystery of a nebula detected 16 years ago, which seems to have its origins in the crash of two stars that merged to form a luminous spheroid, one of a kind.
Research on this object, different from all those that had been recognized in the Milky Way, began in 2004, from the Galaxy Explorer (GALEX) space-based, designed to study the history of star formation.
Scientists noticed a large, faint blob of gas with a star at its center. Among all, a blue stain caused by a thick ring located inside it stood out, it was thus that they identified it as the “Blue Ring Nebula”.
Although the images captured by GALEX showed that bluish halo, in reality it does not emit visible light to the human eye, so the experts devoted themselves to studying it with multiple means, from ground to space telescopes, “but the more they learned, the more it seemed mysterious ”.
For more than a decade, specialists turned to state-of-the-art theoretical models in which they applied the large amount of data they collected over time. As a result, the study was published in “Nature,” which revealed the composition of the Blue Ring Nebula.
NASA researchers stated that although fused star systems are very common, their study requires a long time after their formation. This is because at the time of their origin they are obscured by the debris that caused the collision and later they become difficult to identify because they bear a strong resemblance to unfused stars.
Despite the similarity between the star systems, the researchers differentiated that the nebula had a living star in its center, and they also noted that it did not radiate light, which distinguished it from other types of supernova remnants and planetary nebulae.
A couple of years after starting the research work at GALEX, found evidence of a shock wave in the nebula, suggesting that the gas that makes it up was ejected by a violent event around the central star.
“For quite some time we thought that maybe there was a planet several times the mass of Jupiter being ripped apart by the star, and that was throwing all that gas out of the system,” recalled Mark Seibert, an astrophysicist at the Carnegie Institution and a member of the GALEX team.
This idea lasted until 2012, when a space telescope studied the sky in infrared light, identifying a dust disk orbiting close to the star. Eventually, the team demonstrated that the disk and material ejected into space came from an object larger than a giant planet. something bigger than. In 2017, the Habitable Zone Planet Finder on the Hobby-Eberly Telescope confirmed that there was no compact object orbiting the star.
In this way, NASA experts concluded that the event that produced the nebula was a stellar merger between a star similar to our Sun and a small one. When the first of these stars was nearing the end of its life, it began to approach the smallest spheroid, causing it to break and fall. Afterwards, both were wrapped in a ring of rubble.
As for the bluish halo, the scientists explained that it is a consequence of two weak cone-shaped clouds of debris, which is why they are imperceptible to the human eye. However, the area where the cones overlapped formed the central blue ring that GALEX observed.
The luminosity of this phenomenon, responsible for GALEX detecting it, intensified with the passage of time, when the collisions excited the hydrogen molecules, causing them to radiate at a specific wavelength of glowing ultraviolet light.
During the research work, a group of astronomers joined gradually, adding their knowledge to obtain new data. This was the case of astrophysicist Brian Metzger, which through mathematical and computational models, applied to cosmic phenomena, was able to predict the way the nebula behaved.
Chris Martin, principal investigator at GALEX, revealed that with Metzger as part of the work progress was visibly rushed. “It wasn’t just that Brian could explain the data we were looking at; he was essentially predicting what we had observed before he saw it. He was saying, ‘If this is a stellar fusion, then you should see X,’ and it was like, ‘ Yes! We see that! ‘”He said.
NASA added that stellar mergers can occur with a frequency of approximately 10 years in the Milky Way. “We think there are probably many young remnants of stellar mergers in our galaxy, and the Blue Ring Nebula could show us what they look like so we can identify more,” they said.