What I’m passionate about: Neutron stars, Pulsars, and Magnetars
Lahari Ganti
Many of us are familiar with stars, the bright, burning, balls of plasma in the sky. Yet few people know what happens at the end of these object’s “life cycles”. Most stars similar in size to our sun shed their outer layers to form colorful planetary nebulae. Yet stars tens to hundreds of times more massive than the sun take a more violent turn. At the end of their lives, they undergo what is known as a core collapse supernova: some of the most dramatic fireworks in the universe. The core of the star is crushed so tightly that protons and electrons fuse into neutrons packed densely together . Sometimes, in particularly massive stars, the core can collapse further to form a black hole, but that’s a topic for another time. For now, we’ll go back to the densely packed neutrons. These crushed atomic nuclei form an object called a neutron star, which is exactly what it sounds like. Picture two suns stuffed into an area as small as a city. That’s how dense a neutron star is. In fact, one teaspoon of a neutron star weighs about the same amount as Mt. Everest.
Within neutron stars, there are a few different categories. Pulsars are neutron stars that spin many times per second and emit radiation at their poles. When these beams of radiation are pointed towards earth, we detect a pulse. A fun fact about pulsars is that they were once thought to be alien signals!
Pulsars have various purposes in astronomy. Since pulse arrivals are so regular, irregularities in pulsar timing can be used to detect gravitational waves, fluctuations in space and time. Additionally, changes in the intensity of pulses can be used to make a map of the interstellar medium, bits of dust and gas scattered throughout the universe. Magnetars are a type of neutron star that have the strongest magnetic fields in the universe. A magnetar has a magnetic field up to 10 trillion times stronger than a refrigerator magnet’s magnetic field. Magnetars are especially interesting because they are associated with gamma ray bursts and X-ray bursts, some of the most energetic
events in the universe. Magnetars are interesting because they help us learn more about forces and allow us to test scientific theories.
Neutron stars are also found in binary systems. One famous example of a binary neutron star system is the Hulse-Taylor pulsar, a binary system of a pulsar and a neutron star . The Hulse-Taylor pulsar’s orbital decay allowed for the first indirect detection of gravitational waves and for testing general relativity. In fact, binary neutron stars systems continue to be useful for testing theories today. Gravitational waves produced by these binary systems and neutron star collisions can be studied by LIGO, a gravitational wave observatory.
Overall neutron stars are intriguing objects that have a wide range of applications in astronomy and physics. From pulsar scintillation used to map the interstellar medium, to binary neutron stars and neutron star collisions, neutron stars help us learn more about the universe every day.