Supernova reveals secrets to texas-led team of astronomers
This schematic shows the various ejecta and winds (red and purple) given off by the exploding star (left, yellow). The common-envelope disk (blue) surrounds both stars, the one exploding as a supernova and its binary partner (not shown). The boundary layer around the common-envelope disk is the source of the hydrogen the team detected. Credit: B. Thomas et al./UT Austin

An international group of astronomy led by Benjamin Thomas of The University of Texas at Austin used observations from the Hobby-Eberly Telescope at the McDonald Observatory to uncover a puzzling mystery about a stellar explosion discovered several years ago and evolving even now. The results of a study published in the Astrophysical Journal will help astronomy better understand how massive stars live and die.

Astronomers around the world use telescopes to follow an exploding star as the light it gives off changes rapidly over time. They can see the light from a supernova, but then it starts to dim. They can deduce the physical characteristics of the system by noting the peaks and valleys in the light's brightness, called a light curve, as well as the characteristic wavelength of light emitted at different times.

The emission that is coming from matter that has been cast off from the progenitor system before it explodes as a supernova is really cool.

The progenitor of the supernova was a system in which two stars were in contact. The companion star lost its outer blanket of hydrogen as the massive star evolved. The first star's inner core burned lighter chemical elements into heavier ones until it ran out of fuel. The pressure from the core that held up the star dropped when that happened. The star's core collapsed, causing a huge explosion.

It's a type of supernova that's called a "Type Ib" because it doesn't show any hydrogen in its ejected material at first.

Since its discovery, Thomas and his team have been using telescopes at McDonald Observatory. Many other teams around the world have studied it with telescopes on the ground and in space, as well as in different types of light, including radio waves from the ground-based Very Large Array, and X-rays from the space-based Chandra Observatory.

Astronomers thought a Type Ib supernova should behave, but the studies from all of the telescopes didn't add up.

A surprising finding was made by another team using a different telescope, as the optical signature from the HET showed.

It is completely weird for a Type Ib supernova to begin showing hydrogen.

The light curve of that hydrogen was strange.

Most of the light curves were the same as expected: they got brighter, peaked, and started to fall. The optical light from the hydrogen was not affected.

UT Austin professor and team member J. Craig Wheeler said that the mystery that they have wrestled with is how to fit their Texas HET observations of hydrogen and its characteristics into theType Ib picture.

The team realized that previous models of the system assumed that the supernova had exploded and sent out its shockwave in a spherical manner. The data from HET showed that the hypothesis was impossible.

Wheeler said that it would not fit into a spherically symmetric picture.

The team proposes a model where the hydrogen envelopes of the two stars merged to form a common-envelope configuration, where both were contained within a single envelope of gas. The envelope was expelled in a disk-like structure around the two stars. When one of the stars exploded, its fast- moving ejecta collided with the slow- moving disk, and also slid along the disk surface at an intermediate speed.

The team believes that the origin of the hydrogen they detected is in the boundary layer.

The key to the mystery of the supernova was found in the HET data.

Wheeler said the question of how massive stars lose their mass is a big scientific question. Where is it? When was it ejected? By what process? We were going after the macro questions.

Wheeler said that the event was an important one that was illustrating the process.

More information: Benjamin Thomas et al, Seven Years of Supernova 2014C: a Multi-Wavelength Synthesis of an Extraordinary Supernova, The Astrophysical Journal (2022). arXiv:2203.12747 [astro-ph.HE], Journal information: Astrophysical Journal Citation: Supernova reveals its secrets to team of astronomers (2022, April 27) retrieved 27 April 2022 from This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.