The youngest neutron star we’ve found is now 37 years old. Last week, the James Webb Space Telescope discovered the most direct evidence of it. It was hidden among the remains of the supernova cloud where it was born.
Normally, astronomical objects are millions or billions of years old. So finding something younger than Lady Gaga is unusual. Even stranger is that we know its birthdate: February 23, 1987. That means it just turned 37 last Friday.
We know the exact date of its birth because it happened during a rare event that occurs only once every few centuries: a supernova. This supernova, called SN 1987A, brightened the sky for a few months in early 1987. It was located in the Large Magellanic Cloud, a small galaxy near the Milky Way, about 168,000 light-years away. This explosion should have left behind either a black hole or a neutron star.
Since then, astronomers have been looking for signs of what remained. In 2019, a team from Cardiff University noticed that a certain area of dust in the cloud was shining brighter in certain types of light. Others have found similar evidence indirectly, but a new study has now found the clearest evidence yet that a baby neutron star is there.
The James Webb Space Telescope played a crucial role in this discovery, as it has in many recent ones. Astronomers used its infrared instruments to study the gas and dust in the SN 1987A cloud. They found argon ions that had lost five of their electrons, indicating they were exposed to very powerful photons, which is a strong indicator of a neutron star.
Claes Fransson, the lead author of the study, explained, “To create these ions in the ejecta, there had to be a source of high-energy radiation in the center of the SN 1987A remnant.” The study considered various possibilities and concluded that a newly formed neutron star is the most likely explanation.
So, happy 37th birthday to the likely neutron star of SN 1987A! While a person at that age might be thinking about a midlife crisis, this neutron star has barely begun its long journey and could continue shining for billions of years.
Let’s address a couple of points before we dive into discussions. First, yes, we know that technically, this neutron star is about 168,037 years old due to its distance. But when we start adjusting for time like that, things get complicated. It’s simpler and more practical to describe things based on our perspective here on Earth, since it’s the only viewpoint we have. So, don’t blame us if beings in the LMC have known about it for 168 millennia.
Second, new neutron stars are forming all the time across the universe. So, technically, the title for the youngest neutron star changes constantly. However, when we say “youngest,” we’re referring to the ones we humans have directly detected, allowing us to study their early stages closely.
