Just a few weeks ago, NASA announced that they have discovered a new planet. Over the years, NASA has been known for their new discoveries. What is significant though, is that the planet that may be habitable because it's located in a "habitable zone". Although scientists do not know for sure, because they have not come into direct contact with this planet. To quote, "We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment," said Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center in Moffett Field. In light of this, there are some comparisons and differences between Kepler-452b and Earth to be made, as well as some remarks on habitability. Lower in this article, you will also find some information about the Kepler mission and some of the science behind it.
The planet Kepler-452b is shown below in comparison to our solar system. Note the similarity in terms of radius of orbit, which played a big role in it's discovery, as we will talk about further down the road.
At any rate, Kepler-452b and Earth have many similarities, and some rather blatant differences. For one, Kepler-452b is much older than Earth. Likewise, the star hosting Kepler-452b is 6 billion years old, aging our sun's age (1.5 billion years). This statistic is important, because stars that are older appear much brighter and are at higher temperatures, which as you could imagine affects the temperature of the planet. Kepler-452b is also distinctly larger than Earth at about 60 % larger in diameter, and given the expected larger mass, one feels a much stronger force of gravity than when on earth. Unfortunately though, nothing can be said of the water content yet, but that is certainly one of the big players in determining habitability.
According to NASA, a habitable zone will be a system that consists of a bright star, similar to the sun. They system also has to have planets that are in orbit around their sun. Their star should also have a similar temperature and also size. So far NASA has discovered only nine stars who are similar to our suns. In terms of the content of the planet, one would need water, nutrients, atmosphere, energy (I.E. plants converting sunlight to usable energy, photosynthesis), and a temperature similar to our earth's temperature. With that, we would be in good shape, however, finding all these things in just the right amounts is key, which is what makes earth so unique!
The Kepler Mission is specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets. The purpose of the mission, if you haven't caught on yet, is to find habitable planets. The duration between transits is one year, therefore mission duration should be three and a half years, given the relative speeds and distances that will be traveled. It shouldn't come as a surprise then, that what led primary to the discovery of Kepler-452b, is the spacecraft. The spacecraft includes a specially designed telescope called the photometer, which plays a large role in the clear photos that NASA has released. The photometer actually counts individual photons(particles) of light to create an image, much like the idealized sensors in our eyes. However, the diameter of the telescope needs to be large enough to reduce the noise from photon counting statistics, so that it can measure the small change in brightness of an Earth-like transit. With any luck, which it obviously had, the device can help detect planets that are similar to earth via the photons it counts, and help determine it's habitability.
NASAs Kepler Mission Discovers Bigger, Older Cousin to Earth | NASA. (n.d.). Retrieved from http://www.nasa.gov/press-release/nasa-kepler-mission-discovers-bigger-older-cousin-to-earth