- A glowing cloud called Caldwell 4 or Iris Nebula reflects light from a nearby star
- The nebula is 1,400 light-years away, located in the Cepheus constellation near Polaris
- Discovered in 1794 by William Herschel, it has an apparent magnitude of 7
A glowing cloud in space that looks like a soft blue and pink flower is catching the attention of scientists and skywatchers. This cloud is called Caldwell 4, also known as the Iris Nebula or NGC 7023. It is special because it does not make its own light but shines by reflecting the light of a nearby star, reported NASA.
Most nebulae visible in the night sky are emission nebulae. These are vast clouds of dust and gas that produce their own light due to their extreme heat. In contrast, Caldwell 4 is a reflection nebula, meaning its colour is created by the scattered light of the star at its center.
This star is located among the dense stars of the Cepheus constellation. The Iris Nebula is approximately 1,400 light-years from Earth, and its luminous gas extends for approximately 6 light-years.
When Was Iris Nebula Discovered
The Iris Nebula was discovered on October 18, 1794, by the German-British astronomer William Herschel. He also discovered the planet Uranus and was knighted in 1816. The apparent magnitude of this nebula is recorded as 7.
Caldwell 4 is located near the North Celestial Pole and the pole star Polaris. Therefore, it is nearly impossible to view from the Southern Hemisphere. It can be best seen with binoculars during early autumn in the Northern Hemisphere. To locate it, the two brightest stars in the constellation Cepheus can be used as guides. Because this nebula is faint and diffuse, clear, dark skies away from city lights are ideal for viewing.
The Iris Nebula holds special significance for scientists because of its unique colours. Reflection nebulae glow because they contain extremely fine solid particles. These particles can be 10 to 100 times smaller than Earth's dust. They scatter light around them, creating a faint glow in the nebula, which often appears blue, just like the sky.
Although this nebula appears primarily blue, it also contains long, fibrous structures of a deep red colour. These red areas indicate an unknown chemical compound, possibly hydrocarbon-based. By studying such nebulae, astronomers try to understand what elements are involved in the formation of stars.
This close-up image of a pink halo within Caldwell 4 was created by combining four separate exposures. These images were taken using the Hubble Space Telescope's Advanced Camera for Surveys using visible and near-infrared filters.
Astronomers also used Hubble's Near Infrared Camera and Multi-Object Spectrometer, known as NICMOS, to identify the chemical elements present in Caldwell 4.
