Magnetars are some of the most extreme objects in the universe, with magnetic fields so strong that they can distort the atoms around them. They are a type of neutron star, which are the dense remnants of massive stars that exploded in supernovas.
But how do magnetars form and produce such colossal magnetic fields? A new discovery by a team of astronomers may provide an answer to this mystery.
A Magnetic Monster
The star in question is called HD 45166, and it is located about 3,000 light-years away from Earth in the constellation Monoceros. It is part of a binary system, meaning that it orbits another star. HD 45166 is a helium-rich star, which means that it has lost most of its hydrogen through violent eruptions. This type of star is also known as a Wolf-Rayet star, and they are usually very hot and massive.
However, HD 45166 is not a typical Wolf-Rayet star. It is only four times as massive as the Sun, half the mass of the smallest example we have seen anywhere else. It also has lots of carbon, oxygen, and nitrogen present, which is rare for this type of star. And its spectral lines have some unusual features that indicate that it has a very strong magnetic field.
Using various telescopes around the globe, including the Canada-France-Hawaii Telescope (CFHT) on Maunakea, the researchers were able to measure the magnetic field of HD 45166 and found that it is about 43,000 gauss. This is the most powerful magnetic field ever found in a massive star, and it is comparable to some white dwarfs, which are much smaller and denser than HD 45166.
A New Type of Star
The researchers speculate that HD 45166 is a new type of astronomical object: a massive magnetic helium star. They think that this star was created by the merger of two intermediate-mass stars, which resulted in a rapid rotation and a strong magnetic field. The merger also caused the star to lose its hydrogen envelope and expose its helium core.
This scenario explains why HD 45166 has some of the characteristics of a Wolf-Rayet star, but with some differences. For example, its axis of rotation is aligned with its orbit around its companion star, which is unusual for Wolf-Rayet stars. The merger also explains why HD 45166 has a lot of carbon, oxygen, and nitrogen in its atmosphere, as these elements are produced by nuclear fusion in the cores of intermediate-mass stars.
A Future Magnetar
The researchers also suggest that HD 45166 may be the first magnetar precursor we have seen. They predict that this star will end its life as a supernova and leave behind a neutron star with an extremely powerful magnetic field: a magnetar.
The idea is that HD 45166 will inherit its magnetic field from its progenitor stars, which were already highly magnetized before they merged. When the star collapses into a neutron star, its magnetic field will be amplified by several orders of magnitude due to conservation of magnetic flux. This will create a magnetar with a magnetic field of up to 10^15 gauss, which is about a trillion times stronger than Earth’s.
This hypothesis may solve one of the puzzles about magnetars: how do they form? Until now, we have not observed any massive stars with magnetic fields strong enough to produce magnetars when they die. HD 45166 may be the first example of such a star, and it may not be alone. The researchers estimate that there may be hundreds or thousands of similar stars in our galaxy.
A Fascinating Discovery
The discovery of HD 45166 is not only important for understanding magnetars, but also for studying stellar evolution and magnetic fields in general. It shows that there are more types of stars than we thought, and that stellar mergers can create new and exotic objects. It also demonstrates that magnetic fields can play a crucial role in shaping the fate and appearance of stars.
HD 45166 is a fascinating object that challenges our current knowledge and opens new avenues for research. It is a rare example of a magnetic monster that may become one of the most magnetic objects in the universe: a magnetar.