22 November 2016 | The Helping Hand


Credit: Patrick “Paddy” Gilliland | Click to enlarge

Image Data
  • Location: Worcestershire, United Kingdom
  • Date: Oct. 2, 2016, Oct. 3, 2016, Oct. 4, 2016, Oct. 5, 2016, Oct. 6, 2016
  • Camera: FLI MicroLine 8300 CCD-camera FLI
  • Optics: Officina Stellare Veloce RH 200
  • Mount: Paramount-ME
  • Filters: Astrodon L/R/G/B
  • Exposure: Blue: 20×120″ bin 1×1, Green: 20×120″ bin 1×1, Luminance: 178×180″ bin 1×1, Luminance: 50×30″ bin 1×1, Luminance: 43×300″ bin 1×1, Luminance: 20×60″ bin 1×1, Red: 21×120″ bin 1×1. Total: 15.3 hours

Truely resembling a helping hand, this dark cloud, also known as LDN 1357, is a region of gas and dust.

Other objects in this image are LDN 1355, LBN 643 and vdB 9 & 7. In the lower right is vdB 7 around the bright star HD 17138. The distance from Earth to HD 17138 is about 203 light years.

A dark nebula or absorption nebula is a type of interstellar cloud that is so dense it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust or material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy.

Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C18O (CO with oxygen as the 18O isotope), CS, NH3 (ammonia), H2CO (formaldehyde), c-C3H2 (cyclopropenylidene) and a molecular ion N2H+ (diazenylium), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding star formation.

The form of such dark clouds is very irregular: they have no clearly defined outer boundaries and sometimes take on convoluted serpentine shapes. The largest dark nebulae are visible to the naked eye, appearing as dark patches against the brighter background of the Milky Way like the Coalsack Nebula and the Great Rift. These naked-eye objects are sometimes known as dark cloud constellations and take on a variety of names.

In the inner outer molecular regions of dark nebulae, important events take place, such as the formation of stars and masers.


EAPOD Archive

Want to join us in our quest to show the beauty of the universe to the world? Share this EAPOD with your friends!

Regular publication has been ceased for an indefinite period.