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Mindblown: a blog about philosophy.

  • Further Evolution of Stars

    Learning Objectives By the end of this section, you will be able to: The “life story” we have related so far applies to almost all stars: each starts as a contracting protostar, then lives most of its life as a stable main-sequence star, and eventually moves off the main sequence toward the red-giant region. As…

  • Checking Out the Theory

    Learning Objectives By the end of this section, you will be able to: In the previous section, we indicated that that open clusters are younger than globular clusters, and associations are typically even younger. In this section, we will show how we determine the ages of these star clusters. The key observation is that the…

  • Star Clusters Learning Objectives By the end of this section, you will be able to: The preceding description of stellar evolution is based on calculations. However, no star completes its main-sequence lifetime or its evolution to a red giant quickly enough for us to observe these structural changes as they happen. Fortunately, nature has provided…

  • Evolution from the Main Sequence to Red Giants

    Learning Objectives By the end of this section, you will be able to: One of the best ways to get a “snapshot” of a group of stars is by plotting their properties on an H–R diagram. We have already used the H–R diagram to follow the evolution of protostars up to the time they reach the…

  • New Perspectives on Planet Formation

    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…

  • Exoplanets Everywhere: What We Are Learning

    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…

  • Planets beyond the Solar System: Search and Discovery

    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…

  • Evidence That Planets Form around Other Stars

    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…

  • The H–R Diagram and the Study of Stellar Evolution

    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…

  • Star Formation

    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…

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