Science Daily

Hubble captures a massive star on the verge of extinction

Astronomers directed NASA’s Hubble Space Telescope at a dazzling “celebrity star,” one of the brightest stars seen in our galaxy, surrounded by a glowing halo of gas and dust, to commemorate the 31st anniversary of the Hubble Space Telescope’s launch.

“Living on the brink” is the price for the monster star’s opulence. To escape self-destruction, the star, known as AG Carinae, is engaged in a tug-of-war between gravity and radiation.

The expanding shell of gas and dust that surrounds the star is around five light-years wide, which is the same as the distance between here and the closest star beyond the Sun, Proxima Centauri.

The massive structure was formed by one or more massive eruptions about 10,000 years ago. The outer layers of the star were blown into space, just like a boiling teapot releasing its lid. The substance ejected is about ten times the mass of our Sun.

These outbursts are characteristic of the existence of a special breed of star known as a luminous blue variable, a brief convulsive period in the brief life of an ultra-bright, glamorous star who lives fast and dies young. There are some of the most massive and brilliant stars ever discovered. They only live for a few million years, compared to our Sun’s estimated 10-billion-year lifespan. AG Carinae has been around for a few million years and is located 20,000 light-years away in our Milky Way galaxy.

Luminous blue variables seem to have a dual personality: they appear to spend years in quiescent harmony before exploding in a petulant outburst. These behemoths are stars at their most extreme, vastly different from ordinary stars like our Sun. In reality, AG Carinae is estimated to be up to 70 times the mass of our Sun and to shine with the blinding brilliance of a million suns.

“I enjoy researching these stars because their volatility fascinates me. They’re doing something strange, “Kerstin Weis, a luminous blue vector specialist at Germany’s Ruhr University in Bochum, agreed.

Major outbursts like the one that produced the nebula happen only once or twice in the lifetime of a luminous blue variable. A luminous blue variable star only sheds material when it is on the verge of exploding as a supernova. Because of their massive shapes and extremely high temperatures, luminous blue variable stars like AG Carinae are constantly fighting for stability.

It’s a tug-of-war between radiation pressure from inside the star moving outward and gravity pressing inward. As a result of this celestial alignment, the star expands and contracts. Outward pressure periodically triumphs, and the star expands to such enormous proportions that it blows off its outer layers, much like a volcano erupting. However, this outburst occurs only when the star is on the verge of collapsing. After ejecting the material, the star contracts to its usual size, settles back down, and becomes dormant for a while.

AG Carinae, like many other luminous blue variables, is still unstable. It has had smaller outbursts that were not as intense as the one that formed the current nebula.

While AG Carinae is now dormant, it continues to emit searing radiation and powerful stellar wind as a super-hot star (streams of charged particles). This outflow continues to form the ancient nebula, sculpting complex structures as it collides with the slower-moving outer nebula. The wind will reach speeds of up to 670,000 miles per hour (one million kilometres per hour), which is roughly ten times faster than the expanding nebula. The hot wind eventually catches up with the cooler ejected material, ploughs into it, and drives it away from the star. The “snowploughs” effect has created a space around the star.

The red substance is a glowing hydrogen gas mixed with nitrogen gas. The diffuse red material at upper left indicates where the wind has burst through a shaky region of material and swept it into space.

The most noticeable characteristics are filamentary structures shaped like tadpoles and lopsided bubbles, which are outlined in blue. These structures are made up of dust clumps that have been illuminated by the star’s reflected light. The tadpole-shaped shapes, most visible on the left and right, are denser dust clumps sculpted by the stellar wind. Hubble’s keen vision shows the intricate mechanisms in great detail.

The photograph was taken in both visible and ultraviolet light. The filamentary dust structures that stretch all the way down toward the star are slightly clearer in ultraviolet light. Since this wavelength spectrum can only be seen from space, Hubble is suitable for ultraviolet-light observations.

Massive stars, such as AG Carinae, are significant to astronomers because of the far-reaching impact they have on their surroundings. The Ultraviolet Legacy Library of Young Stars as Essential Standards, Hubble’s largest initiative in history, is researching the ultraviolet light of young stars and how they form their surroundings.

Fewer than 50 luminous blue variable stars are identified among the galaxies in our local community of neighbouring galaxies. These stars are in this process for tens of thousands of years, just a blink of an eye in cosmic time. Many are predicted to die in titanic supernova explosions, which enrich the universe with heavier elements other than iron.

Naeem Ur Rehman

Pakistan's youngest blogger and the CEO of Raabta.net. He is currently the student of BS Environmental Sciences at University of the Punjab, Lahore. He is also working as a senior advisor to Aagahi.pk, Mukaalma, and Pylon TV.

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