436 b. Planet challenged In 2005, the existence of planet e was questioned by Jack Wisdom in a reanalysis of the data. He suggested that the 2.8-day planet was an alias and, separately, that there was a 260-day planet in orbit around 55 Cancri. In 2008, Fischer et al. published a new analysis that appeared to confirm the existence of the 2.8-day planet and the 260-day planet. However, the 2.8-day planet was shown to be an alias by Dawson and Fabrycky in 2010; its true period was 0.7365 days. Transit The planet's transit of its host star was announced on 27 April 2011, based on two weeks of nearly continuous photometric monitoring with the MOST space telescope. The transits occur with the period (0.74 days) and phase that had been predicted by Dawson and Fabrycky. This is one of the few planetary transits to be confirmed around a well-known star, and allowed investigations into the planet's composition. Orbit and mass The radial velocity method used to detect 55 Cancri e obtains the minimum mass of 7.8 times that of Earth, or 48% of the mass of Neptune. The transit shows that its inclination is about 83.4 ± 1.7, so the real mass is close to the minimum. 55 Cancri e is also coplanar with b. The planet is extremely likely to be tidally locked, meaning that there is a permanent day side and a permanent night side. Characteristics 55 Cancri e receives more radiation than Gliese 436 b. The side of the planet facing its star has temperatures more than 2,000 kelvin (approximately 1,700 degrees Celsius or 3,100 Fahrenheit), hot enough to melt iron. Infrared mapping with the Spitzer Space Telescope indicated an average front-side temperature of and an average back-side temperature of around . It was initially unknown whether 55 Cancri e was a small gas giant like Neptune or a large rocky terrestrial planet. In 2011, a transit of the planet was confirmed, allowing scientists to calculate its density. At first it was suspected to be a water planet. As initial observations showed no hydrogen in its Lyman-alpha signature during transit, Ehrenreich speculated that its volatile materials might be carbon dioxide instead of water or hydrogen. An alternative possibility is that 55 Cancri e is a solid planet made of carbon-rich material rather than the oxygen-rich material that makes up the terrestrial planets in the Solar System. In