July 4, 2015
Scientists predict stellar ‘fireworks’ in 2018
You may think your 4th of July fireworks are something special, but they pale in comparison to the high-energy pyrotechnics expected to occur in early 2018, as a stellar remnant roughly the same size as a city encounters one of our galaxy’s brightest stars.As David Thompson, a deputy project scientist stationed at the Goddard Space Flight Center in Greenbelt, Maryland, and his colleagues explained recently in the Monthly Notices of the Royal Astronomical Society, the encounter is expected to put on a rather memorable light show.
In fact, scientists are already in the process of organizing a global campaign to watch the event, which will involve a pulsar known as J2032+4127 swinging by its massive companion star, and will include everything from radio wavelengths to the highest-energy gamma rays detectable, the space agency said.
Pulsars make for quite the show
The pulsar, called J2032 for short, is the crushed core of a massive star that went supernova. The highly-magnetized object weighs almost twice as much as the sun and is approximately 12 miles across, NASA explained, and it spins seven times per second. It was discovered in 2009 by a team of researchers at the University of Manchester in the UK.
As they kept tabs on it from 2010 through 2014, physics professor Andrew Lyne said that his team “detected strange variations in the rotation and the rate at which the rotation slows down, behavior we have not seen in any other isolated pulsar. Ultimately, we realized these peculiarities were caused by motion around another star, making this the longest-period binary system containing a radio pulsar.”
That companion star is a Be star called MT91 213, and according to NASA, its mass is 15 times that of our sun, with a brightness 10,000 times higher than our host star. Be stars like MT91 213 are embedded in large disks of gas and dust and have strong stellar winds. When the researchers first discovered the pulsar, they notices that it was in the same direction as the Be star.
‘Astrophysical fireworks’ are worth the wait
However, as Paul Ray, an astrophysicist at the Naval Research Laboratory explained, “our initial measurements did not give any evidence that either star was a member of a binary system. The only way to escape that conclusion was if the binary system had a very long orbital period, much longer than the longest known pulsar-massive star binary at the time, which seemed unlikely.”
The pulsar was found to have an elongated orbit lasting about 25 years, and at one point in that orbit three years from now, it passes closest to its companion. As it whips around MT91 213, J2032 is expected to plunge through the star’s surrounding disk and set off what NASA is calling “astrophysical fireworks.”
This event is expected to help astronomers measure the gravity, magnetic field, stellar wind, and disk properties of the massive Be star, the agency said. It will also be special for other reasons, such as the fact that out of the half-dozen systems found thus far in which a massive star uses hydrogen as its central energy source, J2032's has the greatest combined mass, has the longest orbital period, and is the closest to Earth (just 5,000 light years away).
“This forewarning of the energetic fireworks expected at closest approach in three years' time allows us to prepare to study the system across the entire electromagnetic spectrum with the largest telescopes,” added Manchester astrophysics professor Ben Stappers.