This 170 years old Stellar Eruption is Simply Amazing

This 170 years old Stellar Eruption is Simply Amazing

The effects of the Great Eruption (which took place in 1843) can still be observed due to a phenomenon called Light Echoes.

Eta Carinae is a stellar system in the constellation Carina that has at least two stars. Their combined luminosity is estimated to be somewhere around 5 million times that of our Sun. Both of these stars have an eccentric orbit with a period of 5.54 years. The first one of them is the only star (known to humanity) that emits ultraviolet laser. Its companion is extremely hot and is 30 to 80 times bigger than the Sun of our solar system. The eruptions in this stellar system have always provided a topic of debate to the astronomical world and the observation from the Gemini South Telescope in Chile is the latest addition to that list.

The spectroscopic results of the Gemini revealed that the ejected material from this eruption is the fastest ever seen from a stellar outburst that didn’t destroy the star completely. Eta Carinae became the 2nd brightest star in our night sky following the Great Eruption but it was a temporary achievement as the star faded away and became invisible from naked eye after few years. Armin Rest, of the Space Telescope Science Institute and Nathan Smith, of the University of Arizona have spent last 7 years in determining the extent of this stellar blast. They have observed light echoes from Eta Carinae and its surroundings for this purpose.

Bright, short-lived events are the source of these light echoes. Light from these events reflect from clouds of dust and is redirected towards us. It is pretty much similar to an audio echo in terms of delay because the speed of light is also finite. The Great Eruption, which took place in the 19th century, was the event that created light echoes for Eta Carinae. An interesting thing here is that the original eruption was seen way back in the mid-1800s when no modern astronomical tool was available. Having said that, the delay in the signals offered an opportunity to the astronomers to decode the light from the eruption through latest telescopes. Smith referred to that in the following words:

A light echo is the next best thing to time travel. That’s why light echoes are so beautiful. They give us a chance to unravel the mysteries of a rare stellar eruption that was witnessed 170 years ago, but using our modern telescopes and cameras. We can also compare that information about the event itself with the 170-year old remnant nebula that was ejected. This was a behemoth stellar explosion from a very rare monster star, the likes of which has not happened since in our Milky Way Galaxy.”

According to researchers, the mass of the erupted material was 10 times more than the mass of our Sun. It is also responsible for the formation of Homunculus, a bright gas cloud. This dumbbell-shaped remnant is visible quite clearly in the sky and can be observed from the equatorial regions and the Southern Hemisphere of the Earth. Even a small telescope is powerful enough to observe this bright glow. However, there is nothing better than seeing the images captured by the Hubble Space Telescope of NASA.

The 8-meter telescope of Gemini South, the Magellan Telescope at the Las Campanas Observatory, and the 4-meter Blanco Telescope of the Cerro Tololo Inter-American Observatory were used to observe these light echoes. It helped the researchers to understand the expansion rate of this historical eruption. Rest explained the role of Gemini spectroscopy by saying,

Gemini spectroscopy helped pin down the unprecedented velocities we observed in this gas, which clocked in at between about 10,000 to 20,000 kilometers per second.”

The speed of this erupted material is at least 20 times more than what we generally get with massive stars. The researching team mentioned that a star system with two stars can manage such an extreme discharge. However, they proposed that the best possible explanation for all the observed facts can be done if we consider an interaction of three stars. They added that a merger between any two of these three stars did took place at some point of time to present Eta Carinae as a binary star system to today’s world. Richard Green, the Director of the Division of Astronomical Sciences at NSF, acknowledged the importance of this research and said,

Understanding the dynamics and environment around the largest stars in our galaxy is one of the most difficult areas of astronomy. Very massive stars live short lives compared to stars like our Sun, but nevertheless catching one in the act of a major evolutionary step is statistically unlikely. That’s why a case like Eta Carinae is so critical, and why NSF supports this kind of research.”

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Muneeb ud Deen
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