Wednesday, 18 October, 2017

The Red Rectangle Nebula

The Red Rectangle was first discovered during a rocket flight in the early 1970s, when astronomers were searching for strong infrared radiation sources. Usually stars surrounded by clouds of dust are often strong infrared sources because the dust is heated by the starlight and radiates long-wavelength light.

monoceros394x290Embedded in the NGC 2244 nebula, it has an apparent magnitude brightness of 9.02 and lies about 2,300 light-years from Earth in the direction of the constellation Monoceros. The nebula itself is a notorious carbon rich nebula, with clear spectral signatures of anthracene and pyrene (hydrocarbons) – potentially vital organic molecules for the formation of life.

redrectangle hubbleA new image, taken with NASA’s Hubble Space Telescope, reveals startling new details of one of the most unusual nebulae known in our Milky Way. Cataloged as HD 44179, but commonly called the “Red Rectangle” because of its unique shape and color surrounding a dying star. Hubble’s sharp pictures show that it is not really rectangular, but has an overall X-shaped structure, arising from outflows of gas and dust ejected from the central star in two opposing directions.

HD44179Also remarkable are straight features that appear like rungs on a ladder, making the Red Rectangle look similar to a spider web, a shape unlike that of any other known nebula in the sky. These rungs may have arisen in episodes of mass ejection from the star occurring every few hundred years.

RR_ISOAstronomers found that the star in the center is actually a close pair of stars that orbit each other with a period of about 10.5 months. Interactions between these stars have probably caused the ejection of the thick dust disk that obscures our view of the binary. Data revealed that the disc in the Red Rectangle is oxygen rich, with evidence for strong silicate dust grain processing.

HD44179Another remarkable feature of the Red Rectangle is the dark band passing across the central star. This dark band is the shadow of a dense disk of dust that surrounds the star. The star in the center of the Red Rectangle is one that began its life as a star similar to our Sun. It is now nearing the end of its lifetime, and is in the process of ejecting its outer layers to produce the visible nebula. In fact, the star itself cannot be seen directly, due to the thickness of the dust disk. All we can see is light that streams out perpendicularly to the disk, and then scatters off of dust particles toward our direction.


Sources: Hubble, Institute of Astronomy, NASA.