Editing Extinction (astronomy) (section)

==The 2175-angstrom feature==

One prominent feature in measured extinction curves of many objects within the Milky Way is a broad 'bump' at about 2175 [[Angstrom|Å]], well into the [[ultraviolet]] region of the electromagnetic spectrum. This feature was first observed in the 1960s,<ref>{{Cite journal
  | author=Stecher, Theodore P.
  | title=Interstellar Extinction in the Ultraviolet
  | journal=Astrophysical Journal
  | date=1965
  | volume=142
  | page=1683
  | bibcode=1965ApJ...142.1683S
  | doi=10.1086/148462
}}</ref><ref>{{Cite journal
  | author=Stecher, Theodore P.
  | title=Interstellar Extinction in the Ultraviolet. II
  | journal=Astrophysical Journal
  | date=1969
  | volume=157
  | pages=L125
  | bibcode=1969ApJ...157L.125S
  | doi=10.1086/180400
| doi-access=free
  }}</ref> but its origin is still not well understood. Several models have been presented to account for this bump which include [[graphite|graphitic]] grains with a mixture of [[Polycyclic aromatic hydrocarbon|PAH]] molecules. Investigations of interstellar grains embedded in interplanetary dust particles (IDP) observed this feature and identified the carrier with organic carbon and amorphous silicates present in the grains.<ref>{{Cite journal
  | author=Bradley, John
  | title=An Astronomical 2175 Å Feature in Interplanetary Dust Particles
  | journal=Science
  | date=2005
  | volume=307
  | issue=5707
  | pages=244–247
  | bibcode=2005Sci...307..244B
  | doi=10.1126/science.1106717
  | pmid=15653501
  | display-authors=2
  | last2=Dai
  | first2=ZR
  | last3=Erni
  | first3=R
  | last4=Browning
  | first4=N
  | last5=Graham
  | first5=G
  | last6=Weber
  | first6=P
  | last7=Smith
  | first7=J
  | last8=Hutcheon
  | first8=I
  | last9=Ishii
  | first9=H
| s2cid=96858465
 }}</ref>