A magnetar is a specific kind of neutron star, themselves the remaining cores of large stars following a supernova explosion. What sets magnetars apart is their intensely potent magnetic fields, far surpassing those of ordinary neutron stars by up to a thousandfold. These magnetic fields are powerful enough to alter the characteristics of the surrounding vacuum and even trigger “starquakes” on the magnetar’s surface, leading to brilliant emissions of X-rays and gamma rays.

Describing the appearance of a magnetar is challenging, as they’re not readily observable in the way planets or other stars might be. Neutron stars are incredibly small – around 20 kilometers in diameter – and distant, which can make direct visibility difficult. Instead, we detect them primarily through the strong magnetic fields they generate and the high-energy radiation they emit.

The environment near a magnetar is incredibly harsh. Its magnetic field has the strength to dismantle atoms, and the radiation levels are lethal. If one could approach and withstand these conditions, the magnetar would likely seem like a minuscule, extraordinarily dense sphere. The immense gravity of a magnetar bends light in a significant way, possibly leading to bizarre visual phenomena.

In the case a magnetar possesses an accretion disk – a disk of material being drawn onto the star – it might radiate intensely in X-rays due to the extreme heat produced by the inward spiral of material under the star’s powerful gravitational pull. However, as of my latest update in September 2021, magnetars are not commonly associated with having such disks.

The surface of a neutron star is anticipated to be exceptionally hot, potentially reaching millions of degrees. This means it could emit a white or possibly bluish-white glow if observed directly. However, this is somewhat conjectural, and the true appearance of a magnetar might vary greatly due to the extreme physical conditions and our still-evolving comprehension of these celestial objects.