A star is born: Astronomers spot youngest known magnetar
Astronomers at NASA and ESA have discovered the youngest pulsar known. This celestial child is a mere 240 years old, and its birth would have been visible on Earth at the time as a supernova.
In astronomy, most objects have had millions or billions of birthdays, so it’s pretty rare to spot something out there that’s younger than American independence. But this little star, known as Swift J1818.0−1607, is the youngest of its type, nudging out Cassiopeia A by about 60-odd years.
Not only is it a neutron star, but it’s also a magnetar, which is a rare type that has a particularly powerful magnetic field. So far only 30 other magnetars have been discovered. It also belongs to the even more exclusive club of magnetars that are also radio pulsars, of which there are only five known members.
Being so young also helps astronomers learn more about the early days of these weird objects.
"This object is showing us an earlier time in a magnetar's life than we've ever seen before, very shortly after its formation," says Nanda Rea, principal investigator on the study.
And it’s quite a gifted child, too. As a neutron star, it packs the mass of two Suns into a space the size of a city. It rotates once every 1.36 seconds, making it one of the fastest-spinning objects ever found. And its incredible magnetic field means it often flares up into outbursts of gamma rays, X-rays and radio waves.
In fact, it was discovered during one of these temper tantrums. NASA’s Neil Gehrels Swift Observatory spotted it on March 12, during an X-ray flare-up. Follow-up observations by XMM-Newton, NuSTAR and the Sardinia Radio Telescope unveiled more of its characteristics.
Magnetars appear to be rare – we know of over 3,000 neutron stars but just 31 pulsars. But the team says that they could be more common than we give them credit for.
“Astronomers have also discovered many magnetars in the past decade, doubling the known population,” says Alice Borghese, co-author of the study. “It’s likely that magnetars are just good at flying under the radar when they’re dormant, and are only discovered when they ‘wake up’ – as demonstrated by this baby magnetar, which was far less luminous before the outburst that led to its discovery.”
The research was published in the Astrophysical Journal Letters.