Astronomers from the University of Manchester have recently presented a study at the National Astronomy Meeting (NAM 2022) revealing that exoplanets orbiting rapidly rotating stars known as pulsars might be incredibly rare. This is an intriguing finding since the very first exoplanets discovered in 1992 were found orbiting a pulsar known as PSR B1257+12. This study is the largest search for exoplanets orbiting pulsars to date, with the findings being presented by Iuliana Nițu, a PhD student at the University of Manchester.
"[Pulsars] produce signals which sweep the Earth every time they rotate, similarly to a cosmic lighthouse," says Nițu. "These signals can then be picked up by radio telescopes and turned into a lot of amazing science."
The research team searched for signals indicating the presence of planets with masses up to 100 times that of Earth, or almost twice the size of Neptune, and demonstrating orbital periods between 20 days and 17 years. The team made 10 potential detections, with the most promising being the system PSR J2007+3120 that potentially hosts at least two planets, both with masses a few times larger than Earth and orbital periods of 1.9 and ~3.6 years.
A key finding of this study was the planets in this system exhibit highly elliptical orbits. This is in stark contrast to the near-circular planetary orbits of our solar system, indicating that the formation processes for pulsar-planet systems greatly varies from traditional star-planet systems such as our own.
"Pulsars are incredibly interesting and exotic objects,” says Nițu. “Exactly 30 years ago, the first extra-solar planets were discovered around a pulsar, but we are yet to understand how these planets can form and survive in such extreme conditions. Finding out how common these are, and what they look like is a crucial step towards this."
This study demonstrates how exoplanets continue to defy how we look at the universe, and particularly how planets are formed. Another example of exoplanets defying traditional star-planet systems is “Hot Jupiters”. As their name implies, they are Jupiter-sized exoplanets who orbit extremely close to their parent star, sometimes completing one orbit in only a few days. Like the aforementioned study, this also contradicts our own solar system, as planets rocky planets are found orbiting close to our Sun with the gas planets orbiting much farther away.
What new discoveries will we make about exoplanets in the coming years, and how much different are exoplanetary systems compared to our own? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!