Banner by Anthony Pascarella
Looking to the Stars and Beyond
by Anthony Pascarella
Imagine for a moment that the Earth is the size of a grain of salt. At this scale, the Sun would be the size of a grapefruit about 10 yards away. The edge of the solar system, marked by the Kuiper Belt outside of Neptune’s orbit, would be about five football fields away. Even Alpha Centauri, the closest star system to us at almost 4 and a half light years away, would be the same distance as a trip from New York to Denver.
Now imagine the distance between the Sun and Alpha Centauri is just 1 inch wide. At this size, the center of our galaxy, the Milky Way, would be about 150 meters away. The Andromeda Galaxy, our nearest galactic neighbor, would be a 15-minute drive away. The Virgo Cluster, a massive collection of nearly 1,300 galaxies in the constellation of Virgo, is over 52 million light years away. At this scale, that equates to a three-hour drive from Pittsburgh to Harrisburg. And the cosmic microwave background, which is the afterglow heat from the birth of the universe and the furthest possible light we can detect, would be just about two-thirds of the way from the Earth to the Moon.
Since humankind first looked to the stars, we have asked ourselves what role we play in the larger picture. As it turns out, that picture is much, much larger than we could have ever imagined. We have come a long way from the first theories of Ptolemy and Copernicus. The more we study our night sky, the more we have come to realize how small our little rock hurtling through space really is. In fact, one astronomer earned part of this year’s Nobel Prize in Physics for proposing that we only know about five percent of what lies beyond our little blue planet. James Peebles, an Albert Einstein Professor of Science at Princeton University, has devoted his life to studying physical cosmology, a branch of astrophysics that specializes in the large-scale structure of the universe itself. Since the mid-1960s, he has developed a theoretical model that now forms the foundation of what modern-day astronomers know about the cosmos.
Peebles used this model to study the cosmic microwave background, the residual heat of the Big Bang that radiates in all directions. What he found is that we only know a tiny fraction of what theoretically exists. The rest is hidden as dark matter and dark energy, currently impossible for us to detect with even our most advanced observational technologies. “This is a mystery and a challenge to modern physics,” reads the Nobel Prize press release. The only way for astronomers to study the hidden 95 percent of the universe is to observe its effects on what we can observe. To this day, Peebles continues his work of studying the “underappreciated issues” of physical cosmology. He looks at isolated galaxies that exist in areas with little to no other matter. These empty voids may be a clue to the existence of the theoretical dark matter, as this would explain how these galaxies could have formed so far from any others. “What might we learn from lines of research that are off the beaten track?” Peebles asks in his Princeton bio. “They check accepted ideas … and there is a chance Nature has prepared yet another surprise for us.”
The other two recipients of this year’s Nobel Prize in Physics, Michel Mayor and Didier Queloz, received their award for their joint 1995 discovery of the first planet outside of our solar system. The discovery of 51 Pegasi b, a gas giant similar to Jupiter, has since led to the discovery of over 4,000 exoplanets in the Milky Way alone. Among these are planets of nearly every size, orbital path and topographical composition imaginable. Some have surfaces made entirely of molten lava, while others are so large that they dwarf even Jupiter. A few worlds might have oceans, and where there is water, there is the potential for life.
Using the concept that a planet with a large enough mass and gravitational field will cause its host star to “wobble” as it orbits, Mayor and Queloz could measure the subtle shifts in the light radiating from such a system. Just as a siren sounds higher in pitch as it gets closer and drops in pitch as it recedes, wavelengths of light compress and stretch in the same manner. As the star “wobbles” towards Earth, pulled by the gravity of its planet, the light that star emits shifts slightly towards the blue end of the light spectrum, since the waves of light compress. When the planet is on the opposite side of the star, the light shifts more towards the red end of the spectrum as the wavelength size increases. This technique allowed the two astronomers to detect a periodic shift in the light coming from the star 51 Pegasi. Upon studying these shifts over a period of time, they confirmed that it was due to the presence of a large, gaseous world orbiting the star so close it circled once every four days. After the discovery of 51 Pegasi b, entire telescopes were built with the sole purpose of finding these new worlds. With these advancements, astronomers have been forced to reexamine how planets form, and it is now theorized that the number of planets far exceeds the number of stars.
Both astronomical breakthroughs have caused a monumental shift in the way astronomers study the cosmos. Peebles’ calculations and models have laid the groundwork for the modern-day theories of how the universe came to be, while Mayor and Queloz’s detection of the first exoplanet has shown us the endless possibility of worlds that lie beyond our solar system. Though there may seem to be little connection between these two discoveries, they share a common theme: bringing humankind one step closer to understanding the mysteries of the cosmos. If there is one thing that unites us, it is our curiosity. As long as we continue to look to the stars and question what lies beyond, there will always be a drive to keep searching, innovating and discovering.