This Is an Actual Photo of a Planet in Another Solar System

Thanks to the Kepler telescope we know that thousands, perhaps billions of planets exist out there in the universe. But we haven’t actually seen very many of themKepler found planets by looking for the absence of starlight—it registered a planet’s presence when the light from a star dipped, as a planet passed in front. Other techniques let astronomers measure the presence of a planet by calculating how the star wobbles because of the gravitational pull of the orbiting planet. But this is different. The photo above is of a planet in a different solar system as seen through a telescope.


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Brightest Stars: Luminosity & Magnitude

A glance at the night sky above Earth shows that some stars are much brighter than others. However, the brightness of a star depends on its composition and how far it is from the planet.

Astronomers define star brightness in terms of apparent magnitude (how bright the star appears from Earth) and absolute magnitude (how bright the star appears at a standard distance of 32.6 light years, or 10 parsecs). Astronomers also measure luminosity — the amount of energy (light) that a star emits from its surface.