Category: 4. Birth of Stars & Discovery of Planets outside Solar System

Learning Objectives By the end of this section, you will be able to: Traditionally, astronomers have assumed that the planets in our solar system formed at about their current distances from the Sun and have remained there ever since. The first step in the formation of a giant planet is to build up a solid…

Learning Objectives By the end of this section, you will be able to: Before the discovery of exoplanets, most astronomers expected that other planetary systems would be much like our own—planets following roughly circular orbits, with the most massive planets several AU from their parent star. Such systems do exist in large numbers, but many…

Learning Objectives By the end of this section, you will be able to: For centuries, astronomers have dreamed of finding planets around other stars, including other planets like Earth. Direct observations of such distant planets are very difficult, however. You might compare a planet orbiting a star to a mosquito flying around one of those…

Learning Objectives By the end of this section, you will be able to: Having developed on a planet and finding it essential to our existence, we have a special interest in how planets fit into the story of star formation. Yet planets outside the solar system are extremely difficult to detect. Recall that we see…

Learning Objectives By the end of this section, you will be able to: One of the best ways to summarize all of these details about how a star or protostar changes with time is to use a Hertzsprung-Russell (H–R) diagram. Recall from The Stars: A Celestial Census that, when looking at an H–R diagram, the temperature (the…

Learning Objectives By the end of this section, you will be able to: As we begin our exploration of how stars are formed, let’s review some basics about stars discussed in earlier chapters: If we want to find stars still in the process of formation, we must look in places that have plenty of the…

“There are countless suns and countless earths all rotating round their suns in exactly the same way as the planets of our system. We see only the suns because they are the largest bodies and are luminous, but their planets remain invisible to us because they are smaller and non-luminous. . . . The unnumbered…