HD 44179, which first caught the attention of astronomers in the 1970s and earned the moniker the “Red Rectangle” due to its unique shape and color, has been revealed to be a dying star and not a planetary nebula as previously thought, the ESA announced this week.
While the Red Rectangle’s existence was known since the early 20th century, it wasn’t until a rocket equipped with an infrared detector was fired in its direction in 1973 that researchers began to realize just how unique HD 44179 truly was. Then, in 2007, an image captured by the Hubble Space Telescope’s Advanced Camera for Surveys showed the star in all its glory.
That image focuses on wavelengths of red light, highlighting hydrogen gas emissions (displayed in red in the photograph below). Also featured is a secondary, broader range of orange-red light which was colored blue in order to increase the contrast. Located some 2,300 light-years from Earth in the constellation Monoceros, the feature is home to a star nearing the end of its lifespan.
According to the ESA, the star in question “has puffed up as the nuclear reactions at its core have faltered, and this has resulted in it shedding its outer layers into space.” They added that this kind of gas cloud was mistakenly labelled as a planetary nebula because astronomer William Herschel believed they looked similar to Uranus (a world which he discovered).
The star HD 44179 is surrounded by an extraordinary structure known as the Red Rectangle. (Credit ESA/Hubble and NASA)
So what’s causing its unusual shape, anyway?
The Hubble image depicting the Red Rectangle also features an X-shape that suggests that there is something keeping the star’s atmosphere from expanding in a uniform fashion. Rather, there is likely a thick dusk disk surrounding the star that causes the gas outflow to be funnelled into two wide cones, which appear in the photograph as diagonal lines.
Hubble scientists explained that the dying star, which is located in the center of the rectangular object, pumps out gas and other material to make the nebula while also giving it is unique and distinctive shape. Furthermore, the star appears to be a close binary, which they said could help explain its unusual appearance. Much of the Red Rectangle remains mysterious, however.
Once the star finishes expelling all of its mass, it will leave behind a very hot white dwarf, and the resulting ultraviolet radiation will be so luminescent that it will cause the surrounding gas to glow, NASA and the ESA explained. The Hubble image was originally published in 2010, they added, and the field of view is roughly 25 by 20 arcseconds.
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Feature Image: The HD 44179 nebula, known as the “Red Rectangle”. Credit: NASA/ESA, Hans Van Winckel (Catholic University of Leuven, Belgium) and Martin Cohen (University of California)
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