However, the Vogt group published even more research that supported the two new planets. Later in 2012, they studied new Doppler spectroscopy experiments and found stronger signs of planets 581f and 581g. They also simulated the two orbit models that the two groups of scientists have proposed. Vogt's group found that the proposed system with four planets was unstable, meaning that if there were only four planets orbiting Gliese 581, the system would have broken a long time ago. On the other hand, they said that the system with six planets was much more stable.