IC 2220 - Toby Jug Nebula

Description by Sakib Rasool

Located towards the constellation of Carina, IC 2220 is a fairly rare example of a yellow reflection nebula. It was given the popular name of the Toby Jug Nebula in 1979 after its appearance in colour photographs taken by David Malin at the Anglo-Australian Observatory.

The central illuminating star it surrounds is the variable red giant V341 Carinae. Studies done by professional astronomers in the past attributed its formation to either mass loss or being ejected by an unseen companion. There is often difficulty in ascertaining the three dimensional structure of a nebula based on our two dimensional view of it. IC 2220 is likely to be both bipolar and biconical.

Reflection nebulae surrounding red giant stars are scarce and the very few examples that are known happen to be a case of ambient interstellar matter in the surrounding region being illuminated. Despite the Toby Jug Nebula lying in a region of interstellar dust, it is unique that not only is it illuminated by a red giant but it has also been produced by it as well via mass loss. The visibility of the nebula is produced by dust grains reflecting the light of the star and it contains a mixture of elements with silicon dioxide being the most likely responsible for the reflection.

Studies by professional astronomers in the past postulated that V341 Carinae was a former member of the open cluster NGC 2516 in the past. This association was based on both sharing similar distances. However in subsequent decades, better quality and more accurate astrometry data from the Hipparcos satellite showed that V341 Carinae had a much closer distance than NGC 2516 of 1200 light years while NGC 2516 has a distance of 1300 light years.

However in the 21st century, more detailed observations are not exclusively reserved for the professional realm of astronomy. Through the proliferation of the internet and other technologies, it is possible for amateur astronomers to own or operate remote observatories. In fact, this image is the product of a remote observatory in Chile being operared by the image author in America.

One such amateur astrophotographer called Josep Drudis who owns a remote observatory in Australia (along with a certain Don Goldman), with the assistance of his daughter Anna, serendipitously took hydrogen alpha exposures for IC 2220 in 2018 for the sake of curiosity and exploration. What was uncovered could not have been predicted, the presence of multiple overlapping arc shaped nebulosities and bubbles. Visually these are represented by the red waves of hydrogen gas visible in this deep image.

Taking into account the well known history of V341 Carinae involving mass loss, these likely represent multiple episodes of mass loss prior to the event that generated the yellow reflection nebula. This is further supported by the separation of the various parts of the whole nebula. There is an absence of ionized hydrogen alpha emission coinciding with the reflection nebula as this is younger and more recent and probably not containing any hydrogen. Since V341 Carinae is known to be a red giant star with an age of 50 million years, it is not unreasonable to assume that the larger and older hydrogen bubbles represent the outer layers of the star that have been ejected in the past. As of March 2020, these enigmatic structures haven't been studied by professional astronomers yet.

Data from El Sauce, Chile 17” Planewave CDK

RGB - 340 Min each, HA - 600-min