Ultra-close Stars Discovered inside a Planetary Nebula

Ultra-close Stars Discovered inside a Planetary Nebula

Scientists want to have a detailed research in order to figure out the origins of some of the most spectacular and violent phenomena in our universe.

Planetary Nebula is a glowing shell of ionized dust and gas formed from the outer layers of stars during the final stages of their life. The name ‘Planetary Nebula’ is a misleading one as this phenomenon has nothing to do with the observation of actual planets. It is believed that the astronomers who discovered these amazing nebulae used this term due to their planet-like round shape. Antoine Darquier de Pellepoix, a French Astronomer who observed a planetary nebula in 1779, described that in the following words:

A very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet.

Most of the times, an interaction with a nearby star plays a vital role in the ejection of the glowing material and the formation of the detailed structures in the planetary nebulae. M3-1 is one such planetary nebula which is located in the constellation of Canis Major. Scientists were pretty confident that it will have a binary central star because it had structures with prominent jets and filaments, which is a typical feature of these binary star interactions.

An international team of researchers used the telescopes of the European Southern Observatory (ESO) in Chile to analyze M3-1 and found two stars in a binary pair. They take around 3 hours to complete an orbit around each other. The researching team studied the planetary nebula for several years before they could come up with fascinating discovery. Brent Miszalski, a Co-author of the study who serves as a Researcher at the Southern African Large Telescope, talked about their findings and said,

We knew M3-1 had to host a binary star, so we set about acquiring the observations required to prove this and to relate the properties of the nebula with the evolution of the star or stars that formed it.

The astronomers involved in the study found that the central star of the M3-1 has the shortest orbital period among all the binary central stars known to date. Both these stars are so close to each other that they cannot be distinguished from the ground. Consequently, the scientists used an alternate path to determine the existence of the second star. They figured it out by observing the combined brightness of these stars. The periodic eclipses of one star by the other led to marked variations in the brightness, which confirmed the presence of the second star. Henri Boffin, a Researcher at the ESO in Germany, elaborated that by saying,

When we began the observations, it was immediately clear that the system was a binary. We saw that the apparently single star at the center of the nebula was rapidly changing in brightness, and we knew that this must be due to the presence of a companion star.”

The analysis of the central star also revealed that the two stars are almost touching with each other. This means that the pair is likely to undergo a ‘Nova Eruption’ during which the glowing material will be transferred from one star to the other. This ultimately leads to a violent ‘Thermonuclear Explosion’ when the transferring material reaches a critical mass. It temporarily increases the brightness of the star system by up to a million times. Paulina Sowicka, a Ph.D. student at the Nicolas Copernicus Astronomical Center, referred to that in the following words:

After the various observing campaigns in Chile, we had enough data to begin to understand the properties of the two stars — their masses, temperatures, and radii. It was a real surprise that the two stars were so close together and so large that they were almost touching one another. A nova explosion could take place in just a few thousand years from now.”

Scientists observed a nova explosion inside another planetary nebula in 2007. It is still a really difficult event to explain because the material in the planetary nebula should have dissipated to a degree that it shouldn’t be visible. According to theory, the binary stars are well separated after the formation of nebulae and it should take a long time for them to come close again. The lead author of the study, David Jones, mentioned that the central stars of M3-1 make it a candidate for a similar explosion in near future.

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