The term “ghost star” refers to a new, peculiar, small yet extremely massive object that scientists are still uncertain about, which is blocking light from a distant star from reaching Earth.
According to SciTech Daily, the “ghost star” was serendipitously recorded by the Hubble Space Telescope and is being studied by scientists from the University of California, Berkeley (UC Berkeley).
Measurements reveal that it is a compact yet unusually heavy object, with an estimated mass ranging from 1.6 to 4.4 million solar masses. There are numerous hypotheses and debates about what it could be, and no one has been able to definitively state its nature, even though the basic properties of the object have been understood.
Graphic depicting the “ghost star” – (Image: SCITECH DAILY)
Designated OB110462, the “ghost star” is most likely a black hole or a neutron star—two types of remnants from massive stars that have died, but are unusual compared to other “zombie” stars.
However, whether it is a black hole or a neutron star, this object is still a remnant of the universe’s first stars—a “star ghost”—discovered wandering through the galaxy without pairing with another star.
Associate Professor Jessica Lu, one of the two lead researchers, expressed hope: “This is the first freely floating black hole or neutron star discovered using the gravitational microlensing method. With microlensing, we can probe these solitary, compact objects and weigh them. I believe we have opened a new window into these dark objects.”
Gravitational microlensing is an observational method based on optical effects, pioneered by scientist Albert Einstein in 1936 using his General Theory of Relativity: When one star in the sky passes in front of another, the light rays from the background star will bend due to the “gravitational pull” of the foreground star.
However, it wasn’t until recently that scientists successfully translated theory into effective observational methods.
Determining the frequency of these “ghost stars” residing in the Milky Way galaxy, which contains Earth, will help astronomers gain further insight into the evolution of stars, particularly how they die. They also hope that some ghost stars are actually primordial black holes, produced in vast numbers during the Big Bang.
The study was recently published online and has been approved by the scientific journal The Astrophysical Journal Letters.
