The Red Rectangle Nebula, known as HD 44179, is a star similar to our Sun that’s nearing the end of its life, and has begun shedding its outer layers into space.
It’s located in the constellation Monoceros about 2,300 lightyears from Earth.
This strange-looking deep-sky object is likely what’s known as a proto-planetary nebula.
As stars like our Sun near the end of their life, they begin to run out of fuel and start ejecting their outer layers of material.
It’s widely believed that the Red Rectangle Nebula is in the early stages of this process, and began shedding material into space about 14,000 years ago.
A few more thousand years into the future, the central star at the core of the nebula will be much smaller and much hotter, causing the nebula to glow even brighter, forming what astronomers know as a planetary nebula.
The term ‘planetary nebula’ is something of a misnomer, however, as they don’t have anything to do with planets.
Planetary nebulae often form puffed-out, spherical shapes, rather like a planetary body: hence their name.
But the Red Rectangle clearly isn’t forming a spherical shape, so what’s going on?
How the Red Rectangle gets its shape
As can be seen with newer images of the Red Rectangle Nebula, like those captured using the Hubble Space Telescope, the nebula is more of an ‘X’ shape.
This is much the same as the famous Boomerang Nebula, the coldest place in the Universe, which when viewed through newer, more powerful telescopes, no longer appears to have a boomerang shape.
The Red Rectangle Nebula’s X formation is a result of outflows of gas and dust emanating from the central star, according to astronomers.
Material is flowing from the star in two opposing directions, producing the distinctive shape.
But what about the layered texture of the outflows? Astronomers say these rung-like formations are produced by regular mass ejections pulsing from the star every few hundred years.
Another reason the Red Rectangle Nebula has such a strange shape could be explained by a relatively new discovery: the star at the centre is actually two stars.
This binary star system is a pair of stars that orbit each other once every 10.5 months, and gravitational interactions between the two may have caused the ejection of a thick disc of dust that once surrounded them.
That could be another explanation for the Red Rectangle Nebula’s unusual shape, as the ejected disc is affecting the funnelling of outflows from the central star.
Discovery
The Red Rectangle Nebula was discovered in 1973 during a rocket flight launched to search for sources of infrared radiation in space.
This mission was known as the Air Force Cambridge Research Laboratory (AFCRL) rocket sky survey.
The name Red Rectangle Nebula was coined by Astronomers Martin Cohen and Mike Merrill, who in 1973 captured an image of the nebula with the 4-metre telescope at Kitt Peak National Observatory.