14 DAY TRIAL // Researchers have recently managed to extract new knowledge on the violent binary star system HM Cancri, and to determine that its members spin around each other in a mere 5.4 minutes. This is extremely fast for such a cosmic pair, which is made up of two white dwarfs, stars about the size of our Sun that have reached the end of their life cycle, and are now burning helium rather than hydrogen. Astrophysicists explain that bodies in this class no longer have the amount of fuel they need to sustain a nuclear fusion reaction, AlphaGalileo reports.
The paper describes HM Cancri as the system with the shortest known orbital period. Granted, the pair itself takes up a very small space, roughly equal to 1/8 of the distance between the Earth and the Moon, or 8 times the diameter of our planet. The international group of investigators behind the research also featured two experts from the University of Warwick, in the United Kingdom, professor Tom Marsh and Dr Danny Steeghs. The experts reveal that these white dwarfs are made almost entirely out of compressed forms of helium, carbon and oxygen.
One of the peculiarities of this system is the fact that the proximity between the two members ensures that mass constantly flows from one to the other. This makes for some fairly interesting fireworks in space, and allows for the emission of important amount of electromagnetic radiation. In fact, it was exactly this light show that first evidenced HM Cancri in the eye of researchers back in 1999, when the first X-ray investigations of the area containing them revealed the pair. Even then, researchers noticed the 5.4-minute-long periodicity, but astronomers said at the time that they were unable to accept that this was the actual orbital period too, without any solid proof.
The recent study, Harvard-Smithsonian Center of Astrophysics (CfA) expert Dr Grij Roelof, provided just that. The group used the twin Keck Telescope in Hawaii, the largest ever built, to look at HM Cancri, and determine the orbital motion of the stars. Observations were made difficult by the fact that the system is located about 16,000 light-years away and has a brightness less than one millionth of the most dim star the human eye can see in the sky. The short orbital period also contributed to the difficulty of the observations.