Free Astronomy Magazine January-February 2019

21 JANUARY-FEBRUARY 2019 SPACE CHRONICLES spectacular jets, which are typically formed by the in- teraction of two stars. According to Brent Miszalski, a researcher at the SALT telescope in South Africa and co-author of the work, “We knew it had to contain a bi- nary, that’s why we decided to study the system to try to understand the re- lationship between the stars and the nebula they have formed” . The ob- servations quickly confirmed the researchers’ suspi- cions. “When we began observing it was immediately clear that it was, in- deed, a binary. Moreover, the bright- ness of the system was changing very quickly and this could mean a rather short orbital period” , says Henri Bof- fin, a researcher at the European Southern Observatory (ESO) in Ger- many. In fact, the study revealed the H ST archival imagery of M 3-1 showing its remarkable filamentary nucleus and extended jet- like structures. [Jones et al.] T his animation shows the orbits of the almost touching stars inside the planetary nebula M3-1. [Jones et al.] separation between the stars to be, approximately, 160,000 kilometers, or less than half the distance be- tween the Moon and the Earth. After various observing campaigns in Chile with ESO’s Very Large Tele- scope (VLT) and New Technology Tel- escope (NTT), the researchers had enough data to work out the prop- erties of the binary system, like the masses, temperatures and sizes of both stars. “To our surprise, we dis- covered that the two stars were quite big and that, as they are so close to one another, it is very likely that they will begin to interact again in just another few thousand years perhaps resulting in nova explosion” adds Paulina Sowicka, PhD student at the Nicolas Copernicus Astronom- ical Center in Poland. The result contradicts current theo- ries of binary stellar evolution which predict that, upon forming the plan- etary nebula, the two stars should take quite a long time before begin- ning to interact again. By the time they do, the nebula should have dis- persed and should no longer be visi- ble. However, a nova explosion in 2007, known as Nova Vul 2007, was found to be inside another planetary nebula, putting into question the models. “In the case of M3-1, we have found a candidate to experi- ence a similar evolution. Given that the stars are almost touching, they shouldn’t take too long before inter- acting again and, perhaps, produc- ing another nova inside a planetary nebula” , concludes Jones. !