Guest Editor - Winter 2021
Astronomy proudly claims the title as the oldest of the natural sciences, with observational records reaching back well over three millennia. Scientists at Penn State are addressing two of the most fundamental questions anyone can pose: What is the nature of the universe? And is the Earth the sole abode of life in the cosmos? We highlight some of these efforts in this issue of the Science Journal.
Over 2,000 years ago, scholars had deduced that the Earth and the moon were spheres, the moon's diameter was approximately a third that of Earth, and the sun was many times the size of our home planet! Speculation that other solar systems existed, perhaps even hosting creatures resembling those on Earth, was present through the centuries, although this branch of inquiry was occasionally hazardous, as the fiery fate of Bruno attests.
Despite this extensive record of progress, only four decades ago, when I was in graduate school, the universe's temporal and spatial scales were so poorly constrained that the age of the universe could have been any value between 10 and 20 billion years. There was considerable uncertainty about whether the universe would continue to expand forever or would halt and collapse in a "big crunch." At that time, there was no evidence for the existence of planets outside of our solar system (known as exoplanets), and attempts to detect life in other star systems was confined to monitoring nearby stars with radio telescopes to record emissions from distant civilizations.
Today's view of the universe is strikingly different than that of my youth. Tremendous advances in instrumentation and computational power have revolutionized our understanding; we now are quite certain that the universe is in the midst of a perpetual expansion, the universe's size and age are known to an accuracy of a few percent, exoplanets appear to be ubiquitous (indeed, there are likely billions of these objects in our galaxy alone!), and the field of astrobiology has blossomed.
Penn State is one of the world leaders in the field of exoplanets, with Evan Pugh University Professors Alexander Wolszczan and James Kasting having discovered the first exoplanets and developed the important concept of the habitable zone, respectively. And a recently announced initiative—the Consortium for Planetary and Exoplanetary Sciences and Technology—in which Eberly’s Eric Ford and Jason Wright figure prominently will further advance the University’s stature in years to come. In this issue of the Science Journal, the first feature article describes an aspect of exoplanet research: the investigation of the formation mechanism for exoplanet systems, which combines observations at a variety of wavelengths with theoretical modeling, applications of advanced statistical methods, and the use of supercomputers.
The second feature article reviews an ambitious international project, in which Penn State is playing a leading role, that aims to determine the expansion history of the universe: the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). By examining the spatial distribution of distant galaxies, and how these structures change with time, astronomers hope to determine the basic composition of the universe. As one can deduce from the title of the survey, HETDEX's primary goal is the study of the mysterious phenomenon that has been designated dark energy; this entity appears to constitute approximately 70 percent of the universe, yet its existence was unknown until the last decade of the twentieth century!
As an astronomer, I am both excited and slightly embarrassed that despite thousands of years of effort, the very nature of the most important constituent of the universe remains a complete mystery! I do believe that we stand on the precipice of a new Copernican revolution, which may require a radical revision of our perspective of our position in the universe; I am enormously excited by the role that Penn State’s scientists will be playing as we enter this brave new world.
Donald Schneider
Distinguished Professor and Head of Astronomy and Astrophysics