Red Supergiant's Dim History Unraveled By Hubble Space Telescope

NASA researchers have published a new study that sheds light on the reason why the red supergiant VY Canis Majoris has grown dim, citing a phenomenon similar to the one that caused Betelgeuse to grow temporarily dim last year. The new findings were made possible using data gathered by the aging Hubble Space Telescope.

Early last year, the iconic red supergiant star Betelgeuse surprised astronomers when it grew dim, stayed that way for several weeks, and then slowly returned to its expected brightness. Using the Hubble Space Telescope, experts eventually narrowed down the likely reason for that dimming: dust caused by a 'gaseous outflow.'

A newly published study has found that 'the same processes' behind Betelgeuse's dimming may also explain why red 'hypergiant' VY Canis Majoris in the Great Dog constellation has also dimmed. This star, which NASA describes as a 'monster' due to its massive size, is much larger than Betelgeuse.

At a considerably greater scale, the study reports that VY Canis Majoris has experienced multiple 'massive ejections of material' that have led to the fading effect — this star is no longer visible with the naked eye as a result. The dimming effect is probably the result of dust caused by the ejections, which is blocking the light.

The Hubble data was used to more accurately determine when these ejections happened, ultimately narrowing it down to several instances that happened in the 19th and 20th centuries.

At the start of its life, VY Canis Majoris was a bright blue supergiant star, slowly becoming a red supergiant over a few million years. The researchers suggest the star may have switched back to a hotter state before once again cooling down, making it a 'second-stage red supergiant.'