Scientists have discovered a young star undergoing a rare growth spurt – giving a fascinating glimpse into the development of these distant stellar objects. The newfound star, called Gaia 17bpi, belongs to a group of stars known as FU Ori’s, named after the original member of the group, FU Orionis found in the Orion constellation.
Typically these FU Ori stars, which are less than a few million years old, are hidden behind thick clouds of dust and are therefore hard to observe. Researchers from University of Exeter in the UK spotted the star undertaking a dramatic phase of evolution, whereby matter swirling around falls onto the star, and so bulking up its mass. The team was able to see this stellar outburst through both infrared and visible light.
Gaia 17bpi is only the 25th member of the FU Ori class found to date, and one of only about a dozen caught in the act of an outburst. “It’s taken a lot of patient waiting and careful sifting of data to uncover this star, but once we realised what was going it has exceeded expectations,” said Tim Naylor, a professor from University of Exeter. “It also gives us insight into events which may have happened as the planets in our own Solar System were beginning to form from a disc of material around the Sun,” Naylor said.
Gaia 17bpi was first spotted by the European Space Agency’s Gaia satellite, which scans the sky continuously and makes precise measurements of stars in visible light. When Gaia spots a change in a star’s brightness, an alert goes out to the astronomy community. The star’s brightening had been independently captured in infrared light by NASA’s asteroid-hunting NEOWISE satellite at the same time that Gaia saw it, as well as one-and-a-half-years earlier.
NASA’s infrared-sensing Spitzer Space Telescope also happened to have witnessed the beginning of the star’s brightening phase twice back in 2014, giving the researchers a bonanza of infrared data.
“These FU Ori events are extremely important in our current understanding of the process of star formation but have remained almost mythical because they have been so difficult to observe,” said Lynne Hillenbrand, professor of at Caltech. “This is actually the first time we’ve ever seen one of these events as it happens in both optical and infrared light, and these data have let us map the movement of material through the disk and onto the star,” said Hillenbrand.
The findings shine light on some of the longstanding mysteries surrounding the evolution of young stars, including how a star acquires all of its mass. Theorists believe that FU Ori events – in which mass is dumped from the disk onto the star over a total period of about 100 years – may help solve the riddle. The study shows how material moves from the midrange of a disk, in a region located around one astronomical unit – the distance between the Earth and the sun – from the star, to the star itself.