Scientists hypothesize presence of exoplanets made up of dark matter

A macroscopic dark matter state with its mass and radius similar to those of a planet will behave as a dark exoplanet if it is bounded to a star system.
Mrigakshi Dixit
Representational image of an exoplanet.
Representational image of an exoplanet.


Dark matter is one of the universe's most enigmatic theories. For astrophysicists, more is unknown about this mysterious stuff than known.

And scientists have been working tirelessly to decode the mystery of dark matter.

A new theory suggests that exoplanets could be made of dark matter. The University of Wisconsin-Madison scientists have dubbed it as “dark exoplanets.”

In a study, they point out ways by which we might be able to identify them.

Identifying dark exoplanets 

Dark matter is defined as a hypothetical invisible mass that accounts for more than 80 percent of all matter in the universe. Dark matter may have shaped the behavior of galaxies and other celestial bodies through gravitational force, such as how stars orbit the centers of their galaxies or how galaxies move too quickly within large clusters.

Despite this evidence, we are yet to detect dark matter directly. As it emits no light or energy, it isn't easy.

Currently it is assumed that all exoplanets are composed of ordinary matter. Several planetary systems, including ours, are mostly made up of basic ordinary matter known as baryonic matter – falling under the Standard Model of particle physics.

But what if exoplanets are made of other types of particles, such as dark matter? Dark matter is thought to be made up of more exotic, composite particles, like macroscopic dark matter. According to ScienceAlert, these particles could have planet-scale masses. 

"A macroscopic dark matter state with its mass and/or radius similar to those of a planet will behave as a dark exoplanet if it is bounded to a star system, even if the object's underlying physics resembles something else entirely," notes the research paper. 

Detecting via transit light method

The team focused on the transit light curve as one of the methods for searching for dark exoplanets. This method aids in investigating the host star's brightness over time and may reveal information about the exoplanet's size, orbit, and radius. Additionally, it could also measure the spectrum of the star during transits for the presence of molecules.

Eventually, the measurements could also be used to calculate the exoplanet's properties and density and determine the presence of particles. If the transit spectrum reveals any significant anomalies, it could point to the presence of a dark matter exoplanet. The study notes that a dark matter exoplanet's properties are likely to differ from those expected of ordinary exoplanets.

“Specifically, we focus on the transit light curve method and demonstrate how to distinguish partially transparent dark exoplanets from fully opaque ordinary exoplanets using both observed exoplanet data and dark exoplanet mock data. Our analysis shows that dark exoplanets with a large radius (above around 10% of the star radius) and a small optical depth (below around one) can be identified with current telescope sensitivities,” reads the paper.