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The nebula NGC 6164/6165, also known as the Dragon’s Egg, a cloud of gas and dust surrounding a pair of stars called HD 148937, taken with the VLT Survey Telescope hosted at the European Southern Observatory’s Paranal Observatory in Cerro Paranal, Chile, have presented a puzzle to astronomers
One of the two large stars residing inside Dragon's Egg has a magnetic field, as does our sun. Its companion does not.
And such massive stars are not usually associated with nebulae.
Relatively few massive stars that are magnetic got that way because of stellar fratricide
In this case, the bigger star apparently gobbled up a smaller sibling star, and the mixing of their stellar material during this hostile takeover created a magnetic field
These two stars - gravitationally bound to each other in what is called a binary system - are located in our Milky Way galaxy about 3,700 light-years from Earth in the constellation Norma.
A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
The magnetic star is about 30 times more massive than the sun and its remaining companion is about 26.5 times more massive than the sun.
They orbit at a distance from each other varying from seven to 60 times the distance between Earth and the sun.
The Dragon's Egg is so named because it is located relatively near a larger nebula complex called the Fighting Dragons of Ara.
The stars inside the Dragon's Egg appear to have started out 4-6 million years ago as a triple system - three stars born at the same time and gravitationally bound.
The triple system's two innermost members included a larger star - perhaps 25 to 30 times the mass of the sun - and a smaller one - maybe five to 10 times the sun's mass.
The more massive one evolved more quickly than the other, with its outer layer engulfing the smaller star and triggering a merger that ejected into space the gas and dust that make up the nebula
This occurred very recently in a cosmic time scale - about 7,500 years ago, based on the expansion velocity of the material in the nebula.
It consists of mostly hydrogen and helium, but also an unusually large amount of nitrogen, after the merger
About 7% of massive stars are known to have a magnetic field.
Stellar magnetic fields store immense amounts of energy.
The sun's magnetic storms can interact with Earth's atmosphere and create our planet's thrilling auroras, but also can disrupt radio signals and navigation systems.
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