Astronomers unravel the mystery of the Dragon Egg nebula – 04/12/2024 – Science

Two large stars nestled in a cloud of gas and dust called the Dragon Egg Nebula were a mystery to astronomers. One of them has a magnetic field, like our Sun. Its neighbor does not. And normally stars this big are not associated with nebulae.

But researchers have apparently solved this mystery and also explained how a few large magnetic stars reached this condition: it is the fault of stellar fratricide. In this case, the larger star swallowed the smaller one, and the mixture of material from both bodies in this hostile capture created the magnetic field.

“This merger was probably very violent. When two stars merge, material can be thrown out, and this probably created the nebula we see today,” said astronomer Abigail Frost of the European Southern Observatory, based in Chile. She is the main author of a study published this Thursday (11) by Science magazine.

Computer simulations have in the past predicted that the joining of stellar material in such a merger could create a magnetic field in the combined star that resulted from the process.

“Our study is full observational proof of this scenario,” said astronomer Hugues Sana of KU Leuven in Belgium, one of the study’s senior authors.

The two stars — gravitationally linked to each other, in what is called a binary system — are located in the Milky Way, about 3,700 light-years from Earth, in the constellation Normas — a light-year is the distance that light travels in one year, or 9.5 trillion kilometers.

The researchers used nine years of observations from the Chile-based Very Large Telescope.

The magnetic star is about 30 times the mass of the Sun. Its remaining companion is approximately 26.5 times greater in mass than the Sun. They orbit with a distance between them of 7 to 60 times that observed between the Earth and the Sun .

The Dragon’s Egg Nebula is so named because it is located relatively close to a larger nebula complex called Ara’s Dragonfight. The stars inside the Dragon’s Egg appear to have begun between 4 and 6 million years ago as a triple system — three stars born at the same time and gravitationally bound.

Many stars the size of the Sun generate magnetic fields: “For low-mass stars like the Sun, convective heating — that of the movement of hot water in a radiator in your home — creates a movement of stellar material. This also creates an effect dynamo that induces the magnetic field,” Frost explained.

“However, for large stars, which are more than eight times the mass of the Sun, effects other than heat come into play, making it more complicated to explain the presence of magnetic fields for these types of stars,” said the astronomer.