# Gravity and Light: Combining Gravitational Wave and Electromagnetic Observations in the 2020s

## TL;DR

The paper discusses the potential scientific breakthroughs from combining gravitational wave and electromagnetic observations, emphasizing the importance of multi-messenger astronomy in understanding diverse astrophysical phenomena.

## Contribution

It outlines the scientific opportunities and questions enabled by future multi-messenger observations, highlighting the potential for major discoveries in astrophysics and cosmology.

## Key findings

- Detection of GW170817 and its electromagnetic counterpart demonstrated multi-messenger potential.
- Future observations will include neutron-star-black-hole mergers and supernovae.
- Combining GW and EM data can address key questions in astrophysics and fundamental physics.

## Abstract

As of today, we have directly detected exactly one source in both gravitational waves (GWs) and electromagnetic (EM) radiation, the binary neutron star merger GW170817, its associated gamma-ray burst GRB170817A, and the subsequent kilonova SSS17a/AT 2017gfo. Within ten years, we will detect hundreds of events, including new classes of events such as neutron-star-black-hole mergers, core-collapse supernovae, and almost certainly something completely unexpected. As we build this sample, we will explore exotic astrophysical topics ranging from nucleosynthesis, stellar evolution, general relativity, high-energy astrophysics, nuclear matter, to cosmology. The discovery potential is extraordinary, and investments in this area will yield major scientific breakthroughs. Here we outline some of the most exciting scientific questions that can be answered by combining GW and EM observations.