‘Ears’ have been discovered on a cosmic nebula

Scientists have now established the key point: these ‘ears’ formed before the main cloud of gas surrounding the star. In other words, the nebula’s history has turned out to be more complex than previously thought: the star did not die in a single, calm outburst, but probably in several stages.

Details

NGC 6563 is located in the constellation Sagittarius, approximately 5,400 light-years from Earth. It was first discovered back in 1826, but new technology has made it possible to examine its structure in much greater detail. To do this, astronomers used data from the MUSE spectrograph on the Very Large Telescope in Chile and the Manchester Echelle Spectrograph in Mexico.

It turned out that the nebula has a main oval cloud, a thin outer shell, two lateral protrusions — the very ‘ears’ — and several other smaller structures. The gas in the main shell is expanding at a speed of around 22 km/s.

The most interesting aspect is the age of the various features. The nebula’s main shell is estimated to have formed around 3,600–3,700 years ago. The ‘ears’, however, turned out to be much older: one is approximately 7,500 years old, the other around 8,800 years old.

Put simply, the star first ejected material in two directions, forming the lateral protrusions. The main gaseous envelope appeared later.

Why might the nebula have developed ‘ears’?

Scientists believe that these protrusions may have arisen due to directed gas flows. This is not like a uniform sphere expanding in all directions, but rather like outflows in specific directions.

One possible scenario is the influence of a second star. If the dying star had a stellar companion, their interaction could have ‘directed’ the gas outbursts and made the nebula’s shape more complex. The authors do not claim that this has been definitively proven, but the data fit this explanation well.

Another factor is the environment surrounding the nebula. The gas may not have expanded into a vacuum, but rather into a heterogeneous environment. Consequently, one side may have moved differently from the other, and the shape of the cloud became irregular over time.

Why this is important

Such nebulae show how Sun-like stars end their lives. When a star runs out of fuel, it sheds its outer layers. These layers form a bright cloud of gas, whilst a hot stellar core remains at the centre.

NGC 6563 shows that this process may not be straightforward or symmetrical. The star may have shed material in several ‘batches’, at different times and in different directions.

This helps astronomers better understand why some nebulae appear almost circular, others elongated, and others still feature rings, tails, jets or ‘ears’.

Background

Planetary nebulae got their name a long time ago, when, viewed through old telescopes, they resembled the small discs of planets. In reality, they are not planets, but the remnants of the outer layers of dying stars.

NGC 6563 was previously described as an elliptical, slightly egg-shaped nebula. New research has clarified its shape and the motion of the gas: it has a main oval body, a thin shell and two older lateral protrusions.

It is these ‘ears’ that change the picture. They suggest that, before the main cloud appeared, the star had already undergone an earlier stage of material ejection.

Source

Study: Zahra Al et al., “Morphokinematic Structure of the Planetary Nebula NGC 6563”, *Galaxies*, 2026.