It turns out that stellar binary (and even triple and quadruple) systems are quite common. In Chapter 10 we show how we can infer the masses of stars through the study of stellar binary systems. For some systems, where the inclination of orbits can be determined unambiguously, we can infer the masses of the stellar components, as well as the distance to the system. Together with the observed apparent magnitudes, this also gives the associated luminosities of their component stars.

In this chapter, Fred Markowitz first provides a brief background on the trends, prevalence, and demographic characteristics of homeless persons in the United States. Next, drawing on sociological theories of social selection and causation processes, he discusses how mental illness is both a cause and consequence of homelessness. He then reviews research on how homelessness is related to criminal offending and incarceration, and how stigma exacerbates these relationships. Finally, he discusses research on programs designed to reduce homelessness, highlighting advances in reducing homelessness in a country with universal health care and “housing first” as a guiding principle. Throughout, he emphasizes the need for more elaborate data for better understanding of processes involved in homelessness. This chapter raises several questions for discussion. First, while mental illness is a significant risk factor for homelessness, in what ways does homelessness exacerbate mental illness and inhibit recovery? Second, Finland has dramatically reduced homelessness over the last several decades. Is it possible to do the same in other countries, such as the United States? Finally, in what ways does lack of a universal health care system create limitations for research on the trajectories of or relationship between mental illness and homelessness?

Research on the use of health care systems has always had two fundamental rationales. First, and most directly, the continued high levels of unmet need, especially for mental health problems and for individuals from minoritized populations, raise concerns both about equity in care and levels of population health. Second, and more generally, understanding how individuals respond to the onset of crises, how they do or do not make decisions, whether they do or do not end up receiving treatment, can find no more critical example than when life and death are at stake. From the earliest studies that countered an ideal view of the “illness career” to recent complex systems models, a range of theories from social science and public health have offered guidance to understanding and examining health care utilization. Here, we describe a pioneering early approach and its critics followed by an overview and findings from the most dominant theoretical models that have been deployed. We describe recent trends that challenge the usual approach and offer three more recent models that target social networks generally and/or health care disparities specifically. We end with a discussion that provides both a sense of where we are and suggests new questions raised by contemporary changes in the landscape of care. Readers should consider how different disciplines and models conceptualized how, why and which people with mental health problems receive care in the formal health system. Further, what do recent studies add to our understanding of the social factors associated with the receipt of treatment and the patterns and pathway by which individuals get there?

Following directly the from the previous chapter, we see that in addition to a shift toward shorter peak wavelength, a higher temperature also increases the overall brightness of blackbody emission at all wavelengths. This suggests that the total energy emitted over all wavelengths should increase quite sharply with temperature. We introduce the Stefan-Boltzmann law, one of the linchpins of stellar astronomy.

How mental distress is understood and defined has significant social and political implications. For this reason, psychiatric nosology – the classification of mental disorders – has come to occupy a central role in debates over mental health policy, patient identity politics, and the professional authority of psychiatry. This chapter explores sociological research on psychiatric nosology. The first section examines the history of classification of mental disorders in the United States, focusing on the professional dynamics that have shaped the Diagnostic and Statistical Manual of Mental Disorders (DSM). The second section describes three key areas of sociological research on psychiatric nosology – medicalization, diagnostic practice, and patient identity – that highlight how social and political factors influence the classification of mental disorders and the concomitant effects of psychiatric nosology. In terms of discussion, how has medicalization impacted our understanding and classification of mental health disorders? Which diagnoses and disorders will later be recognized as acceptable diversity, as was the case with homosexuality? How do social and political factors affect the categorization of mental disorders? Specifically, how has the production, use, and reception of the DSM been shaped by “extra-scientific” political (professional or otherwise) considerations?

Societal concern regarding mental health and illness has grown exponentially worldwide since the publication of the last volume, A Handbook for the Study of Mental Health: Social Contexts, Theories, and Systems (2017). Over the past decade, public policymakers, researchers, clinicians, people living with mental health challenges, those who love them, and journalists in the United States and around the world have spoken out, more frequently and forcefully, about rates of mental distress and the need for policy reforms to increase access and strengthen mental health care. The chapters in this book highlight many of the most important contributions and insights that sociologists of mental health have made to these crucial public conversations as well as to contemporary scientific advancements in the understanding and treatment of mental health and illness.

Mass is clearly a physically important parameter for a star, as it will determine the strength of the gravity that tries to pull the star’s matter together. We discuss one basic way we can determine mass, from orbits of stars in stellar binaries, and see the range of stellar masses. This leads us to the virial theorem, which describes a stably bound gravitational system.

We conclude our discussion of stellar properties by considering ways to infer the rotation of stars. All stars rotate, but in cool, low-mass stars like the Sun the rotation is quite slow. In hotter, more-massive stars, the rotation can be more rapid, with some cases (e.g., the Berillium stars) near the "critical" rotation speed at the star’s surface.

This chapter considers stellar ages. Just how old are stars like the Sun? What provides the energy that keeps them shining? And what will happen to them as they exhaust various available energy sources? We show that the ages and lifetimes of stars like the Sun are set by long nuclear burning timescales and the implications that high-mass stars should have much shorter lifetimes than low-mass stars.