Astronomers have discovered the smallest planet outside our Solar System, and the first that is definitely rocky like Earth. In September 2010, the 4th planet of the Red Dwarf star Gliese 581, appeared to be the best known example of a possible terrestrial exoplanet orbiting near its home star.
An extrasolar planet, or exoplanet, is a planet outside the Solar System. Extrasolar planets became an object of scientific inquiry in the nineteenth century. Many astronomers supposed that they existed, but there was no way of knowing how common they were or how similar they might be to the planets of our solar system. The first confirmed detection was made in 1992, arising interest in the possibility of extraterrestrial life. Most of the discovered extrasolar planets lie within 300 light years of the Solar System. Regardless of the precise number of stars with planets, the total number of exoplanets must be very large. Since our own Milky Way Galaxy has at least 200 billion stars, it must also contain billions of planets – if not hundreds of billions.
Precise measurements using the Kepler space telescope have shown that the planet, named Kepler 10b, has a diameter 1.4 times that of Earth, and a mass 4.6 times higher. Measurements of Kepler techniques using astero-seismology showed that the parent star was about eight billion years old – a grandparent among stars of its type. Kepler techniques are similar to the study of earthquakes on the Earth. In addition to the size of the host star, the details of the planet’s and star’s “dance” with each other, and the planet’s radius, the density of the planet can be calculated. Geoffrey Marcy University of California Berkeley marked this as “among the most profound scientific discoveries in human history.”
Since January 11 of this year (2011), astronomers announced confirmation of 518 such planets – with hundreds others awaiting for confirmation pending further investigation. Most are giant planets thought to resemble Jupiter.
http://www.bbc.co.uk/news/science-environment-12158028
Kepler Mission
The Kepler Mission is a NASA space observatory designed to discover Earth-like planets orbiting other stars. It was launched on 7 May 2009. The mission spacecraft is named in honor of 17th C astronomer Johannes Kepler.
http://www.kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=94
Most exoplanets cannot be seen directly through telescopes because bright light from the stars that they orbit drowns them out. Instead, astronomers use a variety of indirect techniques to find them. One method is to look for tiny wobbles in stars’ positions caused by their gravitational interactions with orbiting planets.
Johannes Kepler (1571 – 1630) was a key mathematician, astronomer and astrologer, in 17th century scientific revolution. He is best known for his laws of planetary motion, later developed by later astronomers. Kepler lived in an era when there was no clear distinction between astronomy and astrology, but there was a strong division between astronomy (a branch of mathematics within the liberal arts) and physics (a branch of natural philosophy).
Kepler also weaved religious reasoning into his work, motivated by the religious conviction that God had created the world according to an “intelligible plan that is accessible through the natural light of reason.” Kepler described his new astronomy as “celestial physics”. (Ref: Wikipedia: Johannes Kepler; Exoplanet, Exosolar)
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