Episode for August 7th, 2023 Download

Our galaxy likely holds hundreds of billions of planets around other stars but when and how did we begin finding them? What was the first exoplanet detected? It turns out that the first discovery wasn’t one, but two planets in the same system.

The steady drumbeat of exoplanet discovery began in 1992 when astronomers Aleksander Wolszczan and Dale Frail found two rocky planets orbiting a type of neutron star known as a pulsar, a rapidly spinning stellar corpse that pulses with millisecond bursts of searing radiation.

Measuring slight changes in the timing of the pulses is what allowed scientists to reveal the two rocky planets in orbit around the pulsar.The planets were named Poltergeist and Phobetor, and they were about the size of Earth and Neptune, respectively. They orbited the pulsar at distances of about where the asteroid belt and Uranus is in our solar system.

These first two planets found by humans on Earth are not habitable. They are too close to the pulsar, and are constantly bombarded by radiation. However, their discovery showed that planets can exist around other stars, and it opened up the possibility that there may be habitable planets out there.

Finding these planets around this spinning star essentially opened the floodgates, and hinted that there must be planets everywhere because if we can find planets around a neutron star, which is a very harsh environment, then the planet production process must be very robust.

A little bit later astronomers started looking for planets like ours and the first planet detected around a Sun-like star was in 1995, and turned out to be a hot Jupiter: a gas giant about half the mass of our own Jupiter in an extremely close, four-day orbit around its star. A year on this planet, in other words, lasts only four days.

From these exciting beginnings, over 5,000 exoplanets have since been discovered and some of them are located in the habitable zone of their stars, which is the region around a star where liquid water could exist on the surface of a planet. Some of these planets are even Earth-sized, which makes them even more likely to be habitable.

The discovery of exoplanets has opened up a new chapter in our understanding of the universe. We now know that planets are not just a unique feature of our own solar system, but are common throughout the galaxy.

We are on the cusp of a new era of discovery, and the possibilities are endless. We are on a quest that will hopefully answer some of the most fundamental questions about our place in the universe, and that could also change the course of human history.