Last week, master and PhD students conducted observations at the Nordic Optical Telescope (NOT) as a part of the course Observational Astrophysics II. The NOT observations are used in an exercise to classify different types of supernovae. The students took their own data of six different objects and classified five of these as type Ia SNe, and one as a type II SN. Jesper Sollerman, the group leader of the Supernova group at the Department, provided the students with the targets to observe and gave the students a preparatory seminar on supernova target discovery and selection.

Students of the Observational Astrophysics II course, in the process of making observations of supernovae using the Nordic Optical Telescope (NOT). Image credit: Terese Thidemann Hansen.

The classifications were published as an AstroNote on the Transient Name Server (TNS). TNS is the official reporting mechanism of astronomical transient objects such as supernova candidates. The TNS is hosted by the International Astronomical Union. You can find the classified SNa and their data here and here.

Supernova SN 2024igg, discovered by the Zwicky Transient Facility in the galaxy NGC 5876, and subsequently classified as a Type II supernova by the students in the course with the aid of their NOT observations. Type II supernovae are explosions of massive stars. The image shows the galaxy before (left) the supernova explosion, the first image of the supernova (middle), and a subtraction of the two images revealing the new supernova clearly.

Type Ia SNe occur in binary systems containing at least one white dwarf. One scenario can be when a star at the end of its lifetimes lose mass to a white dwarf. Eventually, the white dwarf will reach a critical mass that triggers a runaway nuclear fusion reaction which results in an explosion.

Type II SNe happen when a massive star runs out of “fuel” in its core, halting the outwards directed pressure that keeps the star stable. This causes the star to collapse under its own weight, leading to an explosion. The supernova types show different characteristics in the light that is emitted from them, also called their spectra. Through analysis of the spectra, astronomers can get clues about what type of supernova they are observing. Therefore, the supernovae can be classified.

The course Observational Astrophysics II is given as a master course at the Department of Astronomy as Stockholm University each spring. It is a hands-on course that introduces its students to how astrophysical observations are performed. During the course the students observe with both the 20 m radio telescope at Onsala Space Observatory and the Nordic Optical Telescope and subsequently analyse their data.

“The Observational Astrophysics II course gives the students a unique opportunity to get hands-on observational experience using science-grade research facilities and develop skills essential for all astronomers. An added bonus is that they get to obtain data and work on projects from research groups in the department, in this case, the SN group, which can lead to co-authorship on publications.” says Terese Thidemann Hansen, researcher and teacher on the course.

You can find more information about the course here.