Astronomers have discovered two unusual stellar objects that may belong to a completely new class of star remnants.
These objects, nicknamed “Gandalf” and “Moon-Sized,” share a rare combination of features that scientists have not seen together before, raising new questions about how stars evolve after they die.
When stars like our Sun reach the end of their lives, they become white dwarfs—small, extremely dense remnants roughly the size of Earth.
However, not all white dwarfs are the same. In recent years, scientists have learned that many stars exist in pairs or groups, and interactions between them can create unusual outcomes.
The newly identified objects are especially intriguing because they appear to have formed from violent collisions between stars, creating what scientists call “merger remnants.”
Unlike typical white dwarfs, these remnants are extremely massive, highly magnetic, and spin very quickly. Even more surprising, both objects emit X-rays despite having no companion star nearby.
This is unusual because X-rays from white dwarfs are typically produced when they pull material from a nearby companion star, a process known as accretion. Without a companion, scientists have been left wondering where the X-rays are coming from.
The object called Gandalf was first studied in detail by researchers at the Institute of Science and Technology Austria. At first, scientists thought it might be part of a binary system, but no companion star was ever found. Instead, they noticed strange signals in the light coming from the object.
These signals suggested that some material was orbiting the star, but not in a full disk. Rather, it appeared to form a half-ring shape that changed as the star rotated every six minutes.
This kind of structure has never been observed before in a white dwarf. The researchers believe that Gandalf’s strong and uneven magnetic field may trap material in this unusual half-ring shape.
The second object, known as Moon-Sized, was discovered earlier and shares many of Gandalf’s unusual properties. It is also extremely massive, highly magnetic, spins rapidly, and emits X-rays without a companion. However, unlike Gandalf, it does not show signs of surrounding material.
Despite these differences, the two objects share five key characteristics: they are ultra-massive, strongly magnetic, fast-spinning, isolated, and X-ray emitting. Finding two objects with all these overlapping features is rare and has led scientists to suggest they represent a new class of stellar remnants.
There are still many unanswered questions. Researchers have proposed several possible explanations for the X-rays. One idea is that the star’s strong magnetic field and rapid rotation could drive material outward, creating energy emissions. Another possibility is that leftover material from the original stellar collision is slowly falling back onto the remnant over time.
Scientists also considered whether external material, such as debris from planets or asteroids, might be involved. However, this explanation does not fully account for the observations in both objects.
For now, the discovery of Gandalf and Moon-Sized opens a new window into the study of stellar evolution. Finding more objects like these will help researchers better understand how such remnants form and what makes them unique.
Source: KSR.
