In the vast expanse of space, there are some objects that defy the laws of physics as we know them. One such phenomenon is the ultra-luminous X-ray source (ULX), which can be up to 500 times brighter than what we thought was the limit of luminosity. In this article, we will explore the new discoveries, propositions, and recent investigations into these objects, which can provide us with answers to some of the most intriguing questions about the universe.
Why Is This a Problem?
Before delving into the details of ULX, it’s important to understand why this phenomenon is significant. When we think of bright objects in space, we know that they produce luminosity or light. But what we often don’t consider is that photons of light don’t just act as waves but also as particles that can exert a small push on any object they encounter. This effect is known as the Yarkovsky effect, and it’s the reason solar sails can work in space.
However, the brighter the object, the more push it provides to other objects. For example, the Sun can push things around in the solar system and even change the orbits of asteroids, making orbital predictions more challenging. This effect becomes more pronounced with stars that are hundreds, thousands, or even millions of times brighter than the Sun. At some point, the force produced by the light becomes strong enough to counteract the gravitational forces trying to pull objects into the star. This balance is known as the Eddington limit, and when an object becomes too bright, the light starts pushing things away, effectively counteracting gravity.
When an object reaches this limit, it has to be exceptionally bright. But scientists have discovered objects, such as ULX, that are at least 100 times brighter than what the Eddington limit would suggest. These objects produce light in different frequencies and have been observed in various x-ray sources and active galaxies. But usually, when a star becomes too bright, it starts losing a lot of mass from the outer shell, which results in a powerful solar wind that strips the star of its mass and eventually reduces the total luminosity.
What Are Ultra-Luminous X-Ray Sources?
ULX is a term used to describe an unusual class of astronomical objects that emit an extremely high amount of x-rays, at least 10 times higher than the Eddington limit. These objects are typically found in binary systems, where two stars orbit around each other, and one of them is a compact object, such as a neutron star or a black hole.
One example of ULX is the binary system located in the galaxy M82, which contains a super-bright x-ray object and a neutron star, specifically a pulsar. Recent investigations have attempted to determine what is happening in this system, and the findings are intriguing.
What Is Happening in ULX?
Scientists have been trying to figure out why ULX exists and how they produce so much luminosity. One theory is that these objects are powered by the accretion of matter onto a black hole or a neutron star. As matter falls into the compact object, it heats up, producing intense radiation, including x-rays.
However, this theory doesn’t explain why ULX can be so much brighter than the Eddington limit. Recent investigations have suggested that the answer lies in the geometry of the system. In the M82 binary system, for example, the neutron star is spinning rapidly, which creates a strong magnetic field that funnels matter from the companion star onto the neutron star’s poles. As the matter falls onto the poles, it collides and creates a shock wave that emits intense radiation, including x-rays.