If dark matter planets existed, would we be able to detect them? The answer is yes, according to a new study that demonstrates some ways to do just that.
Invisible dark matter seems to be present in all galaxies in the universe, with a few rare exceptions (which, incidentally, quite confuse astronomers). Nobody knows what it is made of, but it is possible to detect it through gravitational interaction with visible objects.
As the authors of the new study explain, there are hypotheses about what dark matter might look like if we could see it. The main ones can be summarized in two groups: isolated particles and macroscopic objects. In this second case, it could appear in the form of dark matter “bubbles”.
In this macroscopic state, dark matter can have large proportions, but also a planet-like size. And if such a bubble exists around stars, just as a planet would, astronomers could find them with some of the same techniques used to detect extrasolar worlds.
The study used two of the methods of detecting exoplanets (worlds orbiting stars other than the Sun), planetary transit and radial velocity. The first consists of observing the light curve when the planet passes in front of its star, while the second observes the displacement of the star due to the gravitational influence of the planet in question.
If an exoplanet is found using one of these techniques, scientists can use spectroscopy, that is, the spectrum of starlight passing through the planet’s atmosphere, to determine its atmospheric composition. Furthermore, when determining the star’s size and orbit around it, it is relatively straightforward to measure its mass and density.
An exoplanet with high density means it is likely to be a rocky world (like Earth), while low density is found on gaseous planets (like Jupiter). A dark matter exoplanet, on the other hand, may have properties that are different from the ordinary one, such as much higher or lower densities than the ordinary one.
If an exoplanet candidate has the light spectrum revealing unusual molecules in its “atmosphere”, or unexplained density, it may be that astronomers are “looking” at a dark matter bubble. In addition, the authors calculated how the light curve would be, which can become the basis for future more elaborate theoretical work.
There is still much to be done to expand this theory and the model to apply to real observations, but it is an interesting step towards the quest to understand dark matter. One of the improvements is to use simulations of planets with elliptical orbits, since only those with circular orbits were considered in the calculations.
The article is available at arXiv.org and awaiting peer review.
Source: arXiv.org
