Galactic Center

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The Galactic Center, as seen by one of the 2MASS infrared telescopes, is located in the bright upper left portion of the image.
Marked location of the Galactic Center.
A starchart of the night sky towards the Galactic Center.

The Galactic Center is the rotational center and the

Shaula, south to the Pipe Nebula
.

There are around 10 million stars within one parsec of the Galactic Center, dominated by red giants, with a significant population of massive supergiants and Wolf–Rayet stars from star formation in the region around 1 million years ago. The core stars are a small part within the much wider galactic bulge.

Discovery

This pan video gives a closer look at a huge image of the central parts of the Milky Way made by combining thousands of images from ESO's VISTA telescope on Paranal in Chile and compares it with the view in visible light. Because VISTA has a camera sensitive to infrared light, it can see through much of the dust blocking the view in visible light, although many more opaque dust filaments still show up well in this picture.

Because of interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet, or soft (low-energy) X-ray wavelengths. The available information about the Galactic Center comes from observations at gamma ray, hard (high-energy) X-ray, infrared, submillimetre, and radio wavelengths.

Alnasl (Gamma Sagittarii) there is a one-degree-wide void in the interstellar dust lanes, which provides a relatively clear view of the swarms of stars around the nucleus of the Milky Way Galaxy.[8] This gap has been known as Baade's Window ever since.[9]

At

Virgo A and Centaurus A. By 1954 they had built an 80-foot (24 m) fixed dish antenna and used it to make a detailed study of an extended, extremely powerful belt of radio emission that was detected in Sagittarius. They named an intense point-source near the center of this belt Sagittarius A, and realised that it was located at the very center of the Galaxy, despite being some 32 degrees south-west of the conjectured galactic center of the time.[10]

In 1958 the

).

In July 2022, astronomers reported the discovery of massive amounts of

Distance to the Galactic Center

Animation of a barred galaxy like the Milky Way showing the presence of an X-shaped bulge. The X-shape extends to about one half of the bar radius. It is directly visible when the bar is seen from the side, but when the viewer is close to the long axis of the bar it cannot be seen directly and its presence can only be inferred from the distribution of brightnesses of stars along a given direction.

The exact distance between the Solar System and the Galactic Center is not certain,[14] although estimates since 2000 have remained within the range 24–28.4 kilolight-years (7.4–8.7 kiloparsecs).[15] The latest estimates from geometric-based methods and standard candles yield the following distances to the Galactic Center:

  • 7.4±0.2(stat) ± 0.2(syst) or 7.4±0.3 kpc (≈24±kly)[15]
  • 7.62±0.32 kpc (≈24.8±1 kly)[16]
  • 7.7±0.7 kpc (≈25.1±2.3 kly)[17]
  • 7.94 or 8.0±0.5 kpc (≈26±1.6 kly)[18][19][20]
  • 7.98±0.15(stat) ± 0.20(syst) or 8.0±0.25 kpc (≈26±0.8 kly)[21]
  • 8.33±0.35 kpc (≈27±1.1 kly)[5]
  • 8.0±0.3 kpc (≈25.96±0.98 kly)[22]
  • 8.7±0.5 kpc (≈28.4±1.6 kly)[23]
  • 8.122±0.031 kpc (≈26.49±0.1 kly)[24]
  • 8.178±0.013(stat) ± 0.022(syst) kpc (≈26.67±0.1 kly)[3]

An accurate determination of the distance to the Galactic Center as established from

reddening law; a bias for smaller values of the distance to the Galactic Center because of a preferential sampling of stars toward the near side of the Galactic bulge owing to interstellar extinction; and an uncertainty in characterizing how a mean distance to a group of variable stars found in the direction of the Galactic bulge relates to the distance to the Galactic Center.[25][26]

The nature of the Milky Way's

kpc ring that contains a large fraction of the molecular hydrogen present in the Milky Way, and most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of the Milky Way.[31]

Supermassive black hole

The supermassive black hole Sagittarius A*, imaged by the Event Horizon Telescope.[32]

The complex astronomical radio source Sagittarius A appears to be located almost exactly at the Galactic Center and contains an intense compact radio source, Sagittarius A*, which coincides with a supermassive black hole at the center of the Milky Way. Accretion of gas onto the black hole, probably involving an accretion disk around it, would release energy to power the radio source, itself much larger than the black hole.

A study in 2008 which linked

perihelion
) is 46 million kilometers (0.3 AU). Thus, the diameter of the radio source is slightly less than the distance from Mercury to the Sun.

Scientists at the Max Planck Institute for Extraterrestrial Physics in Germany using Chilean telescopes have confirmed the existence of a supermassive black hole at the Galactic Center, on the order of 4.3 million solar masses.[5] Later studies have estimated a mass of 3.7 million[34][35] or 4.1 million solar masses.[24]

On 5 January 2015, NASA reported observing an

magnetic field lines within gas flowing into Sagittarius A*, according to astronomers.[36]

There is a supermassive black hole in the bright white area to the right of the center of the image. This composite photograph covers about half of a degree.

Gamma- and X-ray emitting Fermi bubbles

Galactic gamma- and X-ray bubbles
Gamma- and X-ray bubbles at the Milky Way galaxy center: Top: illustration; Bottom: video.

In November 2010, it was announced that two large elliptical lobe structures of energetic

light years above and below the Galactic Center.[37] The galaxy's diffuse gamma-ray fog hampered prior observations, but the discovery team led by D. Finkbeiner, building on research by G. Dobler, worked around this problem.[37] The 2014 Bruno Rossi Prize went to Tracy Slatyer, Douglas Finkbeiner, and Meng Su "for their discovery, in gamma rays, of the large unanticipated Galactic structure called the Fermi bubbles".[39]

The origin of the bubbles is being researched.[40][41] The bubbles are connected and seemingly coupled, via energy transport, to the galactic core by columnar structures of energetic plasma termed chimneys.[42] In 2020, for the first time, the lobes were seen in visible light[43] and optical measurements were made.[44] By 2022, detailed computer simulations further confirmed that the bubbles were caused by the Sagittarius A* black hole.[45][38]

Stellar population

meteor

The central cubic

S0-102. The scenarios invoked to explain this formation involve either star formation in a massive star cluster offset from the Galactic Center that would have migrated to its current location once formed, or star formation within a massive, compact gas accretion disk around the central black-hole. Current evidence favors the latter theory, as formation through a large accretion disk is more likely to lead to the observed discrete edge of the young stellar cluster at roughly 0.5 parsec.[48] Most of these 100 young, massive stars seem to be concentrated within one or two disks, rather than randomly distributed within the central parsec.[49][50]
This observation however does not allow definite conclusions to be drawn at this point.

Star formation does not seem to be occurring currently at the Galactic Center, although the Circumnuclear Disk of molecular gas that orbits the Galactic Center at two parsecs seems a fairly favorable site for star formation. Work presented in 2002 by Antony Stark and Chris Martin mapping the gas density in a 400-

relativistic jets as matter falls into the central black hole
. It is thought that the Milky Way undergoes a starburst of this sort every 500 million years.

In addition to the paradox of youth, there is also a "conundrum of old age" associated with the distribution of the old stars at the Galactic Center. Theoretical models had predicted that the old stars—which far outnumber young stars—should have a steeply-rising density near the black hole, a so-called Bahcall–Wolf cusp. Instead, it was discovered in 2009 that the density of the old stars peaks at a distance of roughly 0.5 parsec from Sgr A*, then falls inward: instead of a dense cluster, there is a "hole", or core, around the black hole.[51] Several suggestions have been put forward to explain this puzzling observation, but none is completely satisfactory.[52][53] For instance, although the black hole would eat stars near it, creating a region of low density, this region would be much smaller than a parsec. Because the observed stars are a fraction of the total number, it is theoretically possible that the overall stellar distribution is different from what is observed, although no plausible models of this sort have been proposed yet.

Gallery

In May 2021 NASA published new images of the Galactic Center, based on surveys from Chandra X-ray Observatory and other telescopes.[54] Images are about 2.2 degrees (1,000 light years) across and 4.2 degrees (2,000 light years) long.

A panorama of the Galactic Center builds on previous surveys from
X-rays from Chandra are orange, green, and purple, showing different X-ray energies, and the radio data from MeerKAT are gray. The next images show single (broadband) colors, with Chandra X-ray data in pink and MeerKAT radio data in blue.
Composite labeled image.
Composite image.
X-ray and Radio single color composite.
  • A small portion of a gigapixel color mosaic of the Milky Way's heart.[55]
    A small portion of a gigapixel color mosaic of the Milky Way's heart.[55]
  • Red giant stars coexist with white, Sun-like stars.[56]
    Red giant stars coexist with white, Sun-like stars.[56]
  • White Dwarfs in Milky Way's Central Hub.[57]
    White Dwarfs in Milky Way's Central Hub.[57]
  • The center of the Milky Way – image taken by ISAAC, the VLT's near- and mid-infrared spectrometer and camera.
    The center of the Milky Way – image taken by ISAAC, the VLT's near- and mid-infrared spectrometer and camera.
  • Infrared image from Spitzer Space Telescope.
    Infrared image from Spitzer Space Telescope.
  • A view of the night sky near Sagittarius, enhanced to show better contrast and detail in the dust lanes. The principal stars in Sagittarius are indicated in red.
    A view of the night sky near Sagittarius, enhanced to show better contrast and detail in the dust lanes. The principal stars in Sagittarius are indicated in red.
  • The central parts of the Milky Way, as observed in the near-infrared with the NACO instrument on ESO's Very Large Telescope.
    The central parts of the Milky Way, as observed in the near-infrared with the NACO instrument on .
  • Infra-red image of the center of the Milky Way revealing a new population of massive stars.
    Infra-red image of the center of the Milky Way revealing a new population of massive stars.
  • Detection of an unusually bright X-ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy.[36]
    Detection of an unusually bright X-ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy.[36]
  • The center of the Milky Way, as imaged by 64 radio telescopes of the South African MeerKAT array.
    The center of the Milky Way, as imaged by 64 radio telescopes of the South African MeerKAT array.
The surroundings of the Galactic Center (Top view map).
The surroundings of the Galactic Center (Top view map).

See also

Notes and references

  1. ^ Overbye, Dennis (31 January 2022). "An Electrifying View of the Heart of the Milky Way – A new radio-wave image of the center of our galaxy reveals all the forms of frenzy that a hundred million or so stars can get up to". The New York Times. Retrieved 1 February 2022.
  2. S2CID 246275657
    .
  3. ^ .
  4. ^ .
  5. ^ .
  6. ^ Ley, Willy (August 1965). "The Galactic Giants". For Your Information. Galaxy Science Fiction. pp. 130–142.
  7. .
  8. .
  9. .
  10. .
  11. .
  12. ^ Starr, Michelle (8 July 2022). "Loads of Precursors For RNA Have Been Detected in The Center of Our Galaxy". ScienceAlert. Retrieved 9 July 2022.
  13. .
  14. .
  15. ^ .
  16. .
  17. .
  18. .
  19. .
  20. (PDF) on 21 June 2007.
  21. ].
  22. .
  23. ^ .
  24. ^ .
  25. ^ .
  26. ^ Vovk, Olga (27 April 2011). "Milky Way: Distance to the Galactic Centre". Universe at a glance (blog). Retrieved 23 March 2019.
  27. S2CID 15040792
    .
  28. .
  29. .
  30. .
  31. ^ Staff (12 September 2005). "Introduction: Galactic Ring Survey". Boston University. Retrieved 10 May 2007.
  32. ^ "Astronomers reveal first image of the black hole at the heart of our galaxy". Event Horizon Telescope. Archived from the original on 12 May 2022. Retrieved 12 May 2022.
  33. S2CID 205040663
    .
  34. .
  35. .
  36. ^ a b Chou, Felicia; Anderson, Janet; Watzke, Megan (5 January 2015). "Release 15-001 – NASA's Chandra Detects Record-Breaking Outburst from Milky Way's Black Hole". NASA.
  37. ^ a b c Aguilar, David A.; Pulliam, Christine (9 November 2010). "Astronomers Find Giant, Previously Unseen Structure in our Galaxy". Harvard-Smithsonian Center for Astrophysics. Release No. 2010-22.
  38. ^
    S2CID 247292361
    .
  39. ^ "2014 Rossi prize awarded to Douglas Finkbeiner, Tracy Slatyer, and Meng Su". Harvard University. 8 January 2014.
  40. S2CID 56443272
    .
  41. ^ Liu, Jia (15 May 2020). "Researchers reveal common origin of Fermi bubbles and galactic center X-ray outflows". Phys.org. Science X Network.
  42. PMID 30894730
    .
  43. .
  44. ^ "236th Meeting of the American Astronomical Society". www.abstractsonline.com. Retrieved 8 June 2020.
  45. ^ University of Michigan (8 March 2022). "Massive bubbles at center of Milky Way caused by supermassive black hole". Phys.org. Science X Network.
  46. ^ "Lecture 31: The Center of Our Galaxy".
  47. S2CID 20968628
    .
  48. .
  49. ^ "UCLA Galactic Center Group". Archived from the original on 26 June 2017. Retrieved 9 November 2007.
  50. ^ "Galactic Center".
  51. S2CID 5221750
    .
  52. .
  53. .
  54. .
  55. ^ "Lights out in the galactic centre". www.eso.org. Retrieved 30 April 2018.
  56. ^ "Hubble captures glittering crowded hub of our Milky Way". www.spacetelescope.org. Retrieved 15 January 2018.
  57. ^ "Hubble Spots White Dwarfs in Milky Way's Central Hub". Retrieved 9 November 2015.

Further reading

Press

External links