List of interstellar and circumstellar molecules

Source: Wikipedia, the free encyclopedia.

vibrational bands
of several molecules labelled in colour

This is a list of molecules that have been detected in the interstellar medium and circumstellar envelopes, grouped by the number of component atoms. The chemical formula is listed for each detected compound, along with any ionized form that has also been observed.

Background

linear molecule
. is the
rotational constant
of the molecule, is the rotational quantum number, is the upper level and is the lower level.

The molecules listed below were detected through

molecular bonds, producing signatures in the mid- or far-infrared. Gas-phase molecules also have quantised rotational levels, leading to transitions at microwave or radio wavelengths.[1]

Sometimes a transition can involve more than one of these types of energy level e.g.

vibronic bands by a simultaneous change in vibrational level, which in turn are split again into rotational branches.[2]

The spectrum of a particular molecule is governed by the

isotope shifts
.

Detection of a new interstellar or circumstellar molecule requires identifying a suitable astronomical object where it is likely to be present, then observing it with a

sub-mm astronomy also becoming important from the 1990s.[3]

The inventory of detected molecules is highly biased towards certain types which are easier to detect: e.g. radio astronomy is most sensitive to small linear molecules with a high

molecular hydrogen), is completely invisible to radio telescopes because it has no dipole;[3] its electronic transitions are too energetic for optical telescopes, so detection of H2 required ultraviolet observations with a sounding rocket.[5] Vibrational lines are often not specific to an individual molecule, allowing only the general class to be identified. For example, the vibrational lines of polycyclic aromatic hydrocarbons (PAHs) were identified in 1984,[6] showing the class of molecules is very common in space,[7] but it took until 2021 to identify any specific PAHs through their rotational lines.[8][9]

The carbon star CW Leonis. The visible shells of circumstellar material were ejected by the central star over thousands of years.

One of the richest sources for detecting interstellar molecules is

giant molecular cloud near the centre of the Milky Way. About half of the molecules listed below were first found in Sgr B2, and many of the others have been subsequently detected there.[10] A rich source of circumstellar molecules is CW Leonis (also known as IRC +10216), a nearby carbon star, where about 50 molecules have been identified.[11]
There is no clear boundary between interstellar and circumstellar media, so both are included in the tables below.

The discipline of

molecular astrophysics
.

Molecules

The following tables list molecules that have been detected in the interstellar medium or circumstellar matter, grouped by the number of component

Deuterated molecules, which contain at least one deuterium
(2H) atom, have slightly different masses and are listed in a separate table. The total number of unique species, including distinct ionization states, is indicated in each section header.

Most of the molecules detected so far are

inorganic molecule with five or more atoms is SiH4.[14] Molecules larger than that all have at least one carbon atom, with no N−N or O−O bonds.[14]

Carbon monoxide is frequently used to trace the distribution of mass in molecular clouds.[15]

Diatomic (43)

H+
3
cation is one of the most abundant ions in the universe. It was first detected in 1993.[56][57]

Triatomic (44)

Formaldehyde is an organic molecule that is widely distributed in the interstellar medium.[91]

Four atoms (30)

Methane, the primary component of natural gas, has also been detected on comets and in the atmosphere of several planets in the Solar System.[117]

Five atoms (20)

methylene to form acetamide.[140]

Six atoms (16)

vinyl alcohol and ethylene oxide have all been detected in interstellar space.[153]

Seven atoms (13)

The radio signature of acetic acid, a compound found in vinegar, was confirmed in 1997.[162]

Eight atoms (14)

Nine atoms (10)

Diacetylene, HCCCCH
Methyldiacetylene, HCCCCCH3
Cyanotetraacetylene, HCCCCCCCCCN
A number of polyyne-derived chemicals are among the heaviest molecules found in the interstellar medium.

Ten or more atoms (22)

Deuterated molecules (22)

These molecules all contain one or more deuterium atoms, a heavier isotope of hydrogen.

Unconfirmed (13)

Evidence for the existence of the following molecules has been reported in the scientific literature, but the detections either are described as tentative by the authors, or have been challenged by other researchers. They await independent confirmation.

See also

References

  1. .
  2. ^ .
  3. ^ Woon, D. E. (May 2005), Methylidyne radical, The Astrochemist, retrieved 2007-02-13
  4. ^
  5. .
  6. .
  7. ^ .
  8. ^ .
  9. , retrieved 2011-05-09
  10. ^
  11. ^ The Structure of Molecular Cloud Cores, Centre for Astrophysics and Planetary Science, University of Kent, retrieved 2007-02-16
  12. ^
  13. New York Times
    . Retrieved 13 December 2013.
  14. .
  15. ^ Landau, Elizabeth (12 October 2016). "Building Blocks of Life's Building Blocks Come From Starlight". NASA. Retrieved 13 October 2016.
  16. ^
  17. ^
  18. ^
  19. ^
  20. ^
  21. , retrieved 2010-09-03
  22. LA Times
    . Retrieved March 9, 2014.
  23. .
  24. ^
  25. ^ Fisher, Christine (17 April 2019). "NASA finally found evidence of the universe's earliest molecule - The elusive helium hydride was found 3,000 light-years away". Engadget. Retrieved 17 April 2018.
  26. S2CID 119548024
    .
  27. ^ Astronomers Detect Molecular Nitrogen Outside Solar System, Space Daily, June 9, 2004, retrieved 2010-06-25
  28. S2CID 4302582
  29. ^ Staff writers (March 27, 2007), Elusive oxygen molecule finally discovered in interstellar space, Physorg.com, retrieved 2007-04-02
  30. .
  31. .
  32. ^
  33. .
  34. ^
  35. ^
  36. ^
  37. .
  38. .
  39. ^
  40. .
  41. .
  42. on December 22, 2006, retrieved 2007-02-08
  43. .
  44. ^
    doi:10.1086/318951{{citation}}: CS1 maint: multiple names: authors list (link
    )
  45. ^
  46. ^
  47. ^ .
  48. ^
  49. ^
  50. from the original on 27 June 2023. Retrieved 27 June 2023.
  51. ^
  52. .
  53. .
  54. .
  55. .
  56. ^
  57. .
  58. ^ H. S. P. Müller (2013). "On Ammonium, NH4+, in the ISM". Retrieved 2022-05-25.
  59. S2CID 118461954
    .
  60. ^ , retrieved 2006-08-10
  61. ^
  62. ^
  63. ^
  64. .
  65. ^ . 37.
  66. .
  67. .
  68. ^
  69. ^
  70. ^ "Complex Organic Molecules Discovered in Infant Star System". NRAO. Astrobiology Web. 8 April 2015. Retrieved 2015-04-09.
  71. ^ First Detection of Methyl Alcohol in a Planet-forming Disc. 15 June 2016.
  72. ^
  73. doi:10.3847/1538-4357/ace523.{{cite journal}}: CS1 maint: numeric names: authors list (link
    )
  74. ^
  75. ^ , retrieved 2006-12-20
  76. ^
  77. .
  78. .
  79. .
  80. .
  81. ^
  82. ^
  83. .
  84. .
  85. .
  86. ^ .
  87. ^
  88. ^
  89. Asilomar, CA, pp. 119–127{{citation}}: CS1 maint: location missing publisher (link
    )
  90. .
  91. .
  92. .
  93. ^
  94. ^ Eyre, Michael (26 September 2014). "Complex organic molecule found in interstellar space". BBC News. Retrieved 2014-09-26.
  95. S2CID 14573206
    .
  96. .
  97. .
  98. .
  99. ^
  100. .
  101. ^
  102. ^
  103. ^
  104. .
  105. .
  106. .
  107. .
  108. ^ .
  109. .
  110. .
  111. .
  112. .
  113. .
  114. - This spectral assignment has not been independently confirmed, and is described by the authors as "tentative" (page L58).
  115. .
  116. ^ a b Battersby, S. (2004). "Space molecules point to organic origins". New Scientist. Retrieved 11 December 2009.
  117. S2CID 56343980

Notes

  1. isotope of argon is 40Ar, so ArH+ would have a mass of 41 amu. However, the interstellar detection was of the 36ArH+ isotopologue
    , which has a mass of 37 amu.

External links