Great comet

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Comet McNaught as the Great Comet of 2007 Comet P1 McNaught02 - 23-01-07.jpg
Comet McNaught as the Great Comet of 2007

A great comet is a comet that becomes exceptionally bright. There is no official definition; often the term is attached to comets such as Halley's Comet, which during certain appearances are bright enough to be noticed by casual observers who are not looking for them, and become well known outside the astronomical community. Typically, they are as bright or brighter than a second magnitude star and have tails that are 10 degrees or longer under dark skies. [1] Great comets appear at irregular, unpredictable intervals, on average about once per decade. Although comets are officially named after their discoverers, great comets are sometimes also referred to by the year in which they appeared great, using the formulation "The Great Comet of ...", followed by the year. It can also be used as a generic name when a very bright comet is discovered by many observers simultaneously. [2]

Contents

Causes

The Great Comet of 1680 over Rotterdam as painted by Lieve Verschuier Lieve Verschuier - Staartster (komeet) boven Rotterdam - 11028-A-B - Museum Rotterdam.jpg
The Great Comet of 1680 over Rotterdam as painted by Lieve Verschuier

The vast majority of comets are never bright enough to be seen by the naked eye, and generally pass through the inner Solar System unseen by anyone except astronomers. However, occasionally a comet may brighten to naked eye visibility, and even more rarely it may become as bright as or brighter than the brightest stars. The requirements for this to occur are: a large and active nucleus, a close approach to the Sun, and a close approach to the Earth. A comet fulfilling all three of these criteria will certainly be very bright. Sometimes, a comet failing on one criterion will still be bright. For example, Comet Hale–Bopp did not approach the Sun very closely, but had an exceptionally large and active nucleus. It was visible to the naked eye for several months and was very widely observed. Similarly, Comet Hyakutake was a relatively small comet, but appeared bright because it passed very close to the Earth.

Size and activity of the nucleus

Cometary nuclei vary in size from a few hundreds of metres across or less to many kilometres across. When they approach the Sun, large amounts of gas and dust are ejected by cometary nuclei, due to solar heating. A crucial factor in how bright a comet becomes is how large and how active its nucleus is. After many returns to the inner Solar System, cometary nuclei become depleted in volatile materials and thus are much less bright than comets which are making their first passage through the Solar System.

Comet Hale-Bopp Comet-Hale-Bopp-29-03-1997 hires adj.jpg
Comet Hale-Bopp

The sudden brightening of Comet Holmes in 2007 showed the importance of the activity of the nucleus in the comet's brightness. On October 23–24, 2007, the comet underwent a sudden outburst which caused it to brighten by factor of about half a million. It unexpectedly brightened from an apparent magnitude of about 17 to about 2.8 in a period of only 42 hours, making it visible to the naked eye. All these temporarily made comet 17P the largest (by radius) object in the Solar System although its nucleus is estimated to be only about 3.4 km in diameter.

Close perihelion approach

The brightness of a simple reflective body varies with the inverse square of its distance from the Sun. That is, if an object's distance from the Sun is halved, its brightness is quadrupled. However, comets behave differently, due to their ejection of large amounts of volatile gas which then also reflect sunlight and may also fluoresce. Their brightness varies roughly as the inverse cube of their distance from the Sun, meaning that if a comet's distance from the Sun is halved, it will become eight times as bright.

This means that the peak brightness of a comet depends significantly on its distance from the Sun. For most comets, the perihelion of their orbit lies outside the Earth's orbit. Any comet approaching the Sun to within 0.5  AU (75 million  km ) or less may have a chance of becoming a great comet.

Close approach to the Earth

For a comet to become very bright, it also needs to pass close to the Earth. Halley's Comet, for example, is usually very bright when it passes through the inner Solar System every seventy-six years, but during its 1986 apparition, its closest approach to Earth was almost the most distant possible. The comet became visible to the naked eye, but was unspectacular. On the other hand, the intrinsically small and faint Comet Hyakutake (C/1996 B2) appeared very bright and spectacular due to its very close approach to Earth at its nearest during March 1996. Its passage near the Earth was one of the closest cometary approaches on record with a distance of 0.1  AU (15 million  km ; 39  LD ).

List of great comets

Great comets of the past two millennia include the following below. This list includes multiple bright apparitions of Halley's Comet since 86 BC:

Comet
DesignationNameImage Dimensions
(km)
(a)
Total
magnitude (M1)
(b)
Maximum
brightness
Perihelion
date
Remarks
X/-371 Great Comet of 371 BC ---371 BCA winter comet reported by Aristotle and Ephorus [3]
P/-86 Q1 Halley 11 km5.52.06 August 87 BCRecorded by ancient Babylonians and Chinese [3]
C/-43 K1 Caesar -–4.0–9.025 May 44 BCNamed after Julius Caesar [4]
P/-11 Q1 Halley 11 km5.5–5.010 October 12 BCVisible to the named eye for 5 months [3]
X/-4 G1 Star of Bethlehem?---15 April 4 BC
P/66 B1 Halley 11 km5.5–7.026 January 66Possibly recorded on Josephus' book, The Jewish War
P/141 F1 Halley 11 km5.5–4.022 March 141
X/178 R1Great Comet of 178 AD---September 178 [3]
X/191 T1Great Comet of 191 AD---20 October 191
P/218 H1 Halley 11 km5.5–4.017 May 218
C/240 V1Great Comet of 240 AD-4.5-30 November 240
P/295 J1 Halley 11 km5.5–3.020 April 295
P/374 E1 Halley 11 km5.5–3.017 February 374Passed within 13.5 million km from Earth
C/390 Q1 Great Comet of 390 AD-7.0–1.05 September 390
C/400 F1Great Comet of 400 AD-6.00.025 February 400
C/442 V1Great Comet of 442 AD-1.51.0–2.015 December 442
P/451 L1 Halley 11 km5.5–3.024 June 451Appeared before the defeat of Attila the Hun at the Battle of Chalons
P/530 Q1 Halley 11 km5.5–3.026 September 530
C/565 O1Great Comet of 565 AD-1.50.015 July 565
C/568 O1Great Comet of 568 AD-5.00.025 September 568
P/607 H1 Halley 11 km5.5–4.013 March 607Passed within 13 million km from Earth [3]
P/684 R1 Halley 11 km5.5–2.028 October 684 [3]
P/760 K1 Halley 11 km5.5–2.022 May 760
C/770 K1Great Comet of 770 AD-3.21.0–2.05 June 770
P/837 F1 Halley 11 km5.5–3.028 February 837Closest known approach to Earth by Halley at 5 million km
C/905 K1Great Comet of 905 AD-4.50.026 April 905
P/912 J1 Halley 11 km5.5–2.09 July 912
P/989 N1 Halley 11 km5.5–1.09 September 989
P/1066 G1 Halley
Comete Tapisserie Bayeux.jpg
11 km5.5–4.023 March 1066Recorded in the Bayeux tapestry
X/1106 C1 Great Comet of 1106 ---1106Parent body of the Kreutz sungrazers
C/1132 T1Great Comet of 1132-4.5–1.030 August 1132 [3]
P/1145 G1 Halley 11 km5.5–2.021 April 1145Depicted on the Eadwine Psalter [3]
P/1222 R1 Halley 11 km5.5–1.030 September 1222 [3]
C/1240 B1Great Comet of 1240-2.50.021 January 1240 [3]
C/1264 N1 Great Comet of 1264
Great comet of 1264.jpg
-3.0–4.00.020 July 1264 [5]
P/1301 R1 Halley
Giotto - Scrovegni - -18- - Adoration of the Magi.jpg
11 km5.5–1.024 October 1301Depicted on the Adoration of the Magi by Giotto di Bondone [3]
P/1378 S1 Halley 11 km5.5–1.09 November 1378 [3]
C/1402 D1 Great Comet of 1402
Augsburger Wunderzeichenbuch, Folio 65.jpg
-0.0–1.0–3.021 March 1402 [6]
P/1456 K1 Halley 11 km5.50.09 June 1456
C/1468 S1Great Comet of 1468-3.21.0–2.07 October 1468 [3]
C/1471 Y1 Great Comet of 1471
Nuremberg chronicles f 254r 1 comet.jpg
-2.0–3.01 March 1472Passed within 10 million km from Earth on January 1472 [7]
P/1531 P1 Halley
Astronomicum Caesareum (1540), p.89v (comet illustration).jpg
11 km5.5–1.025 August 1531 [3]
C/1532 R1Great Comet of 1532-1.8–1.018 October 1532 [3]
C/1533 M1Great Comet of 1533-3.00.015 June 1533 [3]
C/1556 D1 Great Comet of 1556
Istanbul comet and earthquake 1556.jpg
-3.0–2.022 April 1556 [8]
C/1577 V1 Tycho
Von einem Schrecklichen vnd Wunderbarlichen Cometen so sich den Dienstag nach Martini dieses lauffenden M. D. Lxxvij. Jahrs am Himmel erzeiget hat (grayscale).png
-–1.8–3.027 October 1577
P/1607 S1 Halley 11 km5.50.027 October 1607Apparition seen by Johannes Kepler
C/1618 W1 Great Comet of 1618
De verschijning van een komeet in november 1618. NL-HlmNHA 53012544.JPG
-4.60.0–1.06 December 1618
C/1664 W1Great Comet of 1664-2.4–1.04 December 1664 [9]
C/1665 F1Great Comet of 1665-4.9–1.024 April 1665 [3]
C/1668 E1Great Comet of 1668-6.01.0–2.028 February 1668 [3]
C/1680 V1 Kirch
Lieve Verschuier - Staartster (komeet) boven Rotterdam - 11028-A-B - Museum Rotterdam.jpg
-4.01.0–2.018 December 1680Also known as Newton's Comet
P/1682 Q1 Halley
PSM V76 D017 Halley comet in 1682 (horizontal).png
11 km5.5–1.015 September 1682Apparition seen by its namesake, Sir Edmond Halley
C/1686 R1Great Comet of 1686-5.01.0–2.016 September 1686 [3]
C/1743 X1 Klinkenberg–Chéseaux
Cheseaux's Comet of 1744 (The World of Comets).jpg
-0.5–7.01 March 1744
P/1758 Y1 Halley
PSM V76 D017 Halley comet in 1759 (horizontal).png
11 km5.5–1.013 March 1759First successfully predicted return of Halley
C/1760 A1 Great Comet of 1760 -7.62.017 December 1759Passed within 10.2 million km from Earth
C/1769 P1 Messier
Comet 1769 Amsterdam.png
-3.20.08 October 1769 [3]
C/1807 R1 Great Comet of 1807
Basi Revolt.jpg
-1.61.019 September 1807 [3]
C/1811 F1 Flaguergues
Comet of 1811.jpg
30–40 km-0.012 September 1811Visible to the naked eye for 8.55 months
C/1819 N1 Tralles
Great Comet of 1819 from Kendall.jpg
-4.01.0–2.028 June 1819
C/1823 Y1 de Bréauté–Pons
1823comet.jpg
-6.50.09 December 1823
C/1831 A1 Herapath -6.22.028 December 1830
P/1835 P1 Halley
PSM V76 D018 Halley comet in 1835.png
11 km5.50.016 November 1835
C/1843 D1 Great Comet of 1843
Smyth The Great Comet of 1843.jpg
-4.9–3.027 February 1843 Kreutz sungrazer
C/1844 Y1Great Comet of 1844-4.92.514 December 1844 [10]
C/1845 L1Great Comet of 1845-4.0–2.06 June 1845
C/1854 F1Great Comet of 1854-7.02.024 March 1854 [11]
C/1858 L1 Donati
CometDonati.jpg
-3.30.0–1.030 September 1858First comet to be photographed
C/1861 J1 Tebbutt
Great Comet 1861.jpg
-3.90.012 June 1861
C/1865 B1 Great Southern Comet of 1865
Ilustracao O Grande Cometa de 1865 - Semana Illustrada 217.jpg
-3.81.014 January 1865 [3]
C/1874 H1 Coggia
Comet Coggia, 1874.jpg
-5.70.0–1.09 July 1874
C/1880 C1 Great Southern Comet of 1880
Great Southern Comet of 1880.jpg
-7.1–8.93.028 January 1880 Kreutz sungrazer
C/1881 K1 Tebbutt
Trouvelot - The great comet of 1881 - edit 1.jpg
-4.11.016 June 1881
C/1882 R1 Great Comet of 1882
Great Comet of 1882.jpg
-0.7–17.017 September 1882 Kreutz sungrazer, brightest comet ever recorded in history
C/1887 B1 Thome
Great comet of 1887.JPG
-6.3-11 January 1887 Kreutz sungrazer
C/1901 G1 Viscara
Great comet of 1901.jpg
-9.0–1.524 April 1901
P/1909 R1 Halley
Halley's Comet - May 29 1910.jpg
11 km5.50.020 April 1910
C/1910 A1 Great January Comet of 1910
Comet 1910 A1.jpg
-5.0–5.017 January 1910Appeared about four months before the 1910 apparition of Halley
C/1927 X1 Skjellerup–Maristany
Comet 1927k Skjellerup by Slipher.jpg
-5.2–4.018 December 1927
C/1947 X1 Southern Comet of 1947
Comet 1947n.jpg
-6.0–5.02 December 1947 [12]
C/1948 V1 Eclipse Comet of 1948
Comet 1948l.jpg
-9.0–1.027 October 1948 [12]
C/1956 R1 Arend–Roland
Comet Arend-Roland on April 27 by Palomar.jpg
-5.9–0.58 April 1957
C/1957 P1 Mrkos
Comet Mrkos August 25.19 by Palomar.jpg
-4.171.01 August 1957
C/1962 C1 Seki–Lines
Comet Seki-Lines.jpg
--–1.51 April 1962 [11]
C/1965 S1 Ikeya–Seki
Ikeyaseki tail 30Oct1965.jpg
--–10.021 October 1965 Kreutz sungrazer. Brightest comet of the 20th century
C/1969 Y1 Bennett
Comet Bennett 30.5 March 1970.jpg
-4.60.020 March 1970 [3]
C/1975 V1 West
C-west-1976-ps.jpg
-4.4–3.026 February 1976 [3]
C/1995 O1 Hale–Bopp
Comet Hale-Bopp 1995O1.jpg
60 km–1.3–1.81 April 1997Visible to the naked eye for 18 months
C/1996 B1 Hyakutake
Komet Hyakutake von Franz Haar (1).jpg
4.2 km7.40.01 May 1996Passed within 0.1 AU from Earth
C/2006 P1 McNaught
Comet P1 McNaught02 - 23-01-07.jpg
25 km?5.4–5.512 January 2007Brightest comet of the 21st century so far
C/2011 W3 Lovejoy
Iss030e015472 Edit.jpg
0.2–0.5 km15.3–4.016 December 2011 Kreutz sungrazer
C/2020 F3 NEOWISE
Comet 2020 F3 (NEOWISE) on Jul 14 2020 aligned to stars.jpg
5 km7.50.5–1.03 July 2020 [13] [14] [15] [16] [17]
C/2023 A3 Tsuchinshan–ATLAS
Comet Tsuchinshan-ATLAS over Ohio (Composite).jpg
3.2 km?6.5–4.927 September 2024 [18] [19]
C/2024 G3 ATLAS
C2024 G3 (ATLAS) from the ISS by D. Pettit, 11-1-2025 (crop).jpg
-7.6–3.813 January 2025 [20]
Notes:
(a)Due to a non-spherical, irregular shape, a comet's x, y, and z axes instead of an (average) diameter are often used to describe its dimensions.
(b)Total magnitude (M1) as defined in Gary W. Kronk's Cometography: A Catalog of Comets book series
 · List ordered in ascending order by a comet's chronological apparition.

Notes

  1. Seargent, David A. J. (2009). The greatest comets in history: broom stars and celestial scimitars. New York: Springer. p. vii. ISBN   978-0-387-09512-7.
  2. "IAU Comet-naming Guidelines". www.cbat.eps.harvard.edu. Retrieved 8 December 2024.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Donald K. Yeomans (April 2007). "Great Comets in History". Jet Propulsion Laboratory/California Institute of Technology (Solar System Dynamics). Retrieved 2011-02-02.
  4. Ramsey, John T. & Licht, A. Lewis (1997), The Comet of 44 B.C. and Caesar's Funeral Games, Atlanta, ISBN   0-7885-0273-5 {{citation}}: CS1 maint: location missing publisher (link).
  5. The Living Age, Volume 58. Lithotyped by Cowles and Company, 17 Washington St., Boston. Press of Geo. C. Rand & Avery. 1858. p.  879.
  6. David A. J. Seargent (2009). The Greatest Comets in History: Broom Stars and Celestial Scimitars. Springer Science + Business Media. p. 99. ISBN   978-0-387-09512-7.
  7. "Great Comet of 1471". Atlas of Great Comets. Cambridge University Press: 49–50. 2015. doi:10.1017/CBO9781316145166.010. ISBN   9781107093492.
  8. Vsekhsvyatsky, S. K. (1958). Physical Characteristics of Comets. Moscow: Fizmatgiz. p. 102.
  9. "Great Comet of 1664". Atlas of Great Comets. Cambridge University Press: 72–77. 2015. doi:10.1017/CBO9781316145166.016. ISBN   9781107093492.
  10. Bond, G.P. (1850). "On the great comet of 1844–45". The Astronomical Journal. 1: 97. Bibcode:1850AJ......1...97B. doi:10.1086/100067.
  11. 1 2 Bortle, J., "The Bright Comet Chronicles", harvard.edu, retrieved 2008-11-18
  12. 1 2 "Brightest comets seen since 1935". www.icq.eps.harvard.edu. Retrieved 17 January 2024.
  13. "Weekly Information about Bright Comets (2020 July 18: North)". Seiichi Yoshida. July 18, 2020. Archived from the original on July 19, 2020. Retrieved July 18, 2020.
  14. "Seiichi Yoshida's Diary of Comet Observations (2020)". Seiichi Yoshida. July 19, 2020. Archived from the original on July 20, 2020. Retrieved July 19, 2020.
  15. "Comet NEOWISE Updtae: Easy To See In The Evening! When And How To See Comet NEOWISE". Farmer's Almanac. July 18, 2020. Archived from the original on July 19, 2020. Retrieved July 19, 2020.
  16. "APOD: 2022 July 26 - Comet NEOWISE Rising over the Adriatic Sea". NASA. July 26, 2022. Retrieved October 17, 2024.
  17. "Great Comets: What Are They, And When Will the Next Comet Be Visible?". Star Walk. October 16, 2024. Retrieved October 17, 2024.
  18. 2024 October 21 - Comet Tsuchinshan-ATLAS over California. APOD Podcast. Event occurs at 6m00s via YouTube.
  19. 2024 November 11 - The Unusual Tails of Comet Tsuchinshan ATLAS. APOD Podcast. Event occurs at 0m19s via YouTube.
  20. "Why Comet G3 (ATLAS) will be 'remembered as the Great Comet of 2025' (photos)". Space.com. January 27, 2025. Retrieved January 27, 2025.