Answer to Question 1
A planet orbiting another star is called an extrasolar planet. Such a planet would be quite faint and difficult to detect so close to the glare of its star. But there are ways to find these planets. To see how, all you have to do is imagine walking a dog.You will remember that Earth and its moon orbit around their common center of mass, and two stars in a binary system orbit around their center of mass. When a planet orbits a star, the star moves very slightly as it orbits the center of mass of the planet-star system. Think of someone walking a poorly trained dog on a leash; the dog runs around pulling on the leash, and even if it were an invisible dog, you could plot its path by watching how its owner was jerked back and forth. Astronomers can detect a planet orbiting another star by watching how the star moves as the planet tugs on it.
Answer to Question 2
Infrared astronomers have found cold, low-density dust disks around older stars such as Vega and Beta Pictoris. Although much younger than the Sun, these stars are on the main sequence and have completed their formation, so they are clearly in a later stage than the newborn stars in Orion. These low-density disks generally have even lower-density inner zones where planets may have formed. Such tenuous dust disks are sometimes called debris disks because they are understood to be dusty debris released in collisions among small bodies such as comets, asteroids, and Kuiper Belt objects.
Accretion of the Inner Planets
The Inner Planets: A Comparison
Inverse Relation Between IQ and Disease. Could this explain the Flynn effect?
Orbital Motion of Earth and Other Planets
Reflectivity of Inner Planets
For the circuit in Figure 1, assume ideal diodes. The peak inverse voltage is approximately