Meet OGLE-2005-BLG-390Lb

It is the 'most earth-like planet' that has been discovered so far using a technique called, "gravitational microlensing, a method that relies on light from a background star being bent and magnified by the gravitational field of a star in the foreground."

What is Microlensing?

The gravitational microlensing technique is based on a concept first discussed by Albert Einstein in the early 20th century. When astronomers observe a star, the light waves generally travel straight from the star to the telescope. However, if another star passes directly in between, even if great distances separate the two, the gravity of the nearer object acts like a lens and magnifies the incoming light.

Telescopes cannot resolve the details of the magnified image, but they do notice a peak in light intensity, and when a planet is present around the closer star, the planet's gravity adds a small peak of its own.

Astronomers can use those features to determine how large the planet is and how far away it is from its star. This method is 50 times more likely to detect planets of approximately twice the mass of Jupiter than it is to detect planets closer to the mass of Earth. Even relatively tiny, low-mass objects can give a strong peak signal if alignment is perfect.

Of the more than 150 planets discovered to date, almost all were discovered using a different technique, the radial velocity method. Stars with planets can wobble from the effect of their planets' gravity, and astronomers can use the wobble to determine the size and orbit of the objects. While incredibly effective, existing technology utilizing this method can find only large, Jupiter-like planets or smaller planets that orbit too close to their host stars to harbor life.

Because the newly discovered planet is only the third astronomers have detected using gravitational microlensing and already they have found a small, rocky body, the researchers believe there is a strong likelihood that rocky planets may be even more common than their gas-giant brethren. This prediction would agree with one of the models for solar system formation, core accretion, which suggests that small, rocky, "failed Jupiters" should be far more common than the massive gaseous planets.

That's your science lesson for today:)

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