Space scientist helps identify young star caught in a fit of growth

A researcher at the University is among an international team to have discovered a young star in the midst of a rare growth spurt - a dramatic phase of stellar evolution when matter swirling around a star falls onto the star, bulking up its mass.

Dr Dirk Froebrich, of the University’s School of Physical Sciences, made use of Kent’s Beacon Observatory to study the optical brightness and colours of Gaia 17bpi. The star belongs to a class of stars known as FU Ori’s, named after the original member of the group, FU Orionis.

Typically these stars, which are less than a few million years old, are hidden behind thick clouds of dust and hard to observe. This new object is only the 25th member of this class found to date and one of only about a dozen caught in the act of an outburst.

The newfound star, called Gaia 17bpi, was first spotted by the European Space Agency’s Gaia satellite, which scans the sky continuously, making 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 project, led by the US science and engineering institute Caltech, also saw NASA‘s infrared-sensing Spitzer Space Telescope used to witness the beginning of the star’s brightening phase twice back in 2014, providing the researchers with infrared data.

The new findings shine light on some of the longstanding mysteries surrounding the evolution of young stars. One unanswered question is: How does a star acquire all of its mass? Stars form from collapsing balls of gas and dust. With time, a disk of material forms around the star, and the star continues to siphon material from this disk. But, according to previous observations, stars do not pull material onto themselves fast enough to reach their final masses.

Dr Froebrich said: ‘We believe that these 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. We think that all stars undergo around 10 to 20 or so of these FU Ori events in their lifetimes but, because this stellar phase is often hidden behind dust, the data are limited.’

The study, entitled Gaia 17bpi: An FU Ori Type Outburst, is published in the journal The Astrophysical Journal. Other authors include: Carlos Contreras Peña and Tim Naylor of the University of Exeter; Michael Kuhn and Luisa Rebull of Caltech; Simon Hodgkin of Cambridge University; and Amy Mainzer of JPL.