A planet is able to affect the flow of matter from one star to a second, changing the brightness of their binary system. This makes it possible to spot planets orbiting cataclysmic variable pairs.
Cataclysmic variables are binary systems and their brightness changes as one star moves around the other. However, such variations sometimes do not coincide with the orbital period of the system, which may indicate the presence of a planet invisible to telescopes. This is the conclusion reached by the authors of a new paper published in the journal MNRAS. The astronomers believe the brightness anomalies will make it possible to detect new exoplanets even in such variable systems.
Cataclysmic variables are stars that change their brightness abruptly from time to time, flaring violently and then slowly fading away. They come in different types but always consist of two stars orbiting each other. One is much more massive, hotter and denser than its partner and gradually pulls its matter towards itself. This pair is usually made up of white dwarfs (about 0.75 solar mass on average, comparable in size to the Earth) and red dwarfs (0.1-0.3 solar mass and about 0.2 solar diameter).
Moving from a red dwarf to a white dwarf, the matter tends to form an accretion disk, which becomes very hot and sometimes begins to emit radiation brighter than even the stars themselves. From there, it falls to the surface of the white dwarf and, when enough material has accumulated on it, new thermonuclear reactions start there, causing the variable to flare up abruptly - on the scale of hours or days. Once the 'superfluous' reaction gas has been exhausted, the star will gradually die down to flare up again in a few or even thousands of years.
However, if such a system contains a third body, invisible to telescopes, its gravity should affect the flow of matter from the donor star and hence the accretion disk emission. The brightness of such cataclysmic variables may vary, not coinciding with the period of rotation of a pair of stars around each other. Just such objects - LU Constellation Giraffe, QZ Snake, V1007 Hercules and BK Lynx - have been considered in a new paper by Carlos Chavez and his colleagues at the Autonomous University of Nuevo Leon in Mexico. Their calculations showed that planet-like bodies may be present in at least two of these four systems.
Scientists believe that this approach will find application in the search for new exoplanets in the near future. The transit method, which is most popular today, can spot distant planets by varying the brightness of their stars when the planets partially cover them as they pass through their orbits. The planet's plane of rotation must be in the line of observation, otherwise no eclipse will occur. But variations in the brightness of cataclysmic variables do not depend on their orientation relative to us. Perhaps they will help discover many new exoplanets orbiting at all angles around such restless stellar pairs.
