When star dies in a violent cataclysmic supernova, it becomes the kitchen for the recipes of the universe, all the elements heavier than iron are produced in one of these explosive supernovae. When a star goes supernova it releases so much energy, that it outshines the galaxy it is from.
Do you know that supernova explosion can release energy as much as our star Sun can release over its entire life span – that is almost 10 billion years!
This post is not about supernovae but the beautiful remnants left behind the supernova called nebula. Nebula is a broad term, and it means interstellar clouds of dust, hydrogen, helium and other ionized gases and it is formed by many means, supernovae is one of them.
Let’s see some of the most beautiful remnants of stars.
Helix Nebula – The Helix, NGC 7293
This is a beautiful planetary nebula in the constellation Aquarius. It is some 650 light-years away from us and discovered in 18th century. Helix nebula is almost 3 light years in diameter – the ring like shape.
Planetary nebula is created when a star blows off the outer layers after it ran out of fuel. The outer layer expands like a bubble, the term ‘planetary nebula’ was coined by William Herschel because they looked like big gas giant planets.
There is a white dwarf star is in the heart of Helix nebula, when the original star went out of fuel and threw out its outer layers and leaving behind tiny, dense hot core, which is called white dwarf star.
Do you know? White dwarf star is about the size of our planet Earth, but it is very massive. A teaspoon of white dwarf material would weigh as much as few elephants!
You can see the dust circling the white dwarf star in the infrared/ultraviolet image – the bright purple area.
Infrared image data from Spitzer and Ultraviolet data from GALEX.
Cat’s Eye Nebula – NGC 6543
Cat’s Eye nebula is also a planetary nebula and it is one of the complex planetary nebula ever observed. In 1994 Hubble Space Telescope showed detailed structure of this nebula including its gas shells and jets of high speed gas.
Cat’s Eye Nebula is discovered by William Herschel in 1786 and it is about 3200 light years away from us. The reason behind the shape is that the star ejected its mass in series of pulses between 1500 years intervals.
Until recently the shell shape around the planetary nebula were considered rare phenomenon, but however in April 2004, in a paper published in European journal Astronomy and Astrophysics showed that the formation of these rings are likely to be a rule than exception.
Ring Nebula – NGC 6822
Ring Nebula is a planetary nebula in the constellation of Lyra. It is around 2000 light-years away and about 1 light-years across. This nebula was discovered by French astronomer Antoine Darquier de Pellepoix in 1779. Ring Nebula is also catalogued by Charles Messier and now known as Messier 57.
In the image, blue color in the central area is ionized helium. Cyan color in the inner ring is the glow of hydrogen and oxygen and the reddish color of outer ring is made out of nitrogen and sulfur.
We will see more nebulae in the future posts.
Source: Hubble Space Telescope, NASA and ESA
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