Leonids

For other uses, see Leonid (disambiguation).

Leonids
A Leonid meteor during the peak of the Leonids in 2009
Pronunciation/ˈliːənɪdz/
Discovery date902 AD (first record)[1]
Parent body55P/Tempel–Tuttle[2]
Radiant
ConstellationLeo
Right ascension10h 17m [3]
Declination+21.6°[3]
Properties
Occurs during3 November – 2 December[3]
Date of peak17 November
Velocity70–71[3][4] km/s
Zenithal hourly rate15[3]
See also: List of meteor showers

The Leonids (/ˈliːənɪdz/ LEE-ə-nidz) are a prolific annual meteor shower associated with the comet Tempel–Tuttle, and are also known for their spectacular meteor storms that occur about every 33 years.[5] The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. Their proper Greek name should be Leontids with an additional ⟨t⟩ (Λεοντίδαι, Leontídai), but the word was initially constructed as a Greek/Latin hybrid[citation needed] and it has been used since.

Earth moves through meteoroid streams left from passages of a comet. The streams consist of solid particles, known as meteoroids, normally ejected by the comet as its frozen gases evaporate under the heat of the Sun when it is near the Sun – typically closer than Jupiter's orbit. Due to the retrograde orbit of 55P/Tempel–Tuttle, the Leonids are fast moving streams which encounter the path of Earth and impact at 70 km/s (43 mi/s).[3] It is the fastest annual meteor shower.[3] Larger Leonids which are about 10 mm (0.4 in) across have a mass of 0.5 g (0.02 oz) and are known for generating bright (apparent magnitude −1.5) meteors.[6] An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet.

The meteoroids left by the comet are organized in trails in orbits similar to – though different from – that of the comet. They are differentially disturbed by the planets, in particular Jupiter,[7] and to a lesser extent by radiation pressure from the Sun – the Poynting–Robertson effect and the Yarkovsky effect.[8] These trails of meteoroids cause meteor showers when Earth encounters them. Old trails are spatially not dense and compose the meteor shower with a few meteors per minute. In the case of the Leonids, that tends to peak around 18 November, but some are spread through several days on either side and the specific peak changes every year. Conversely, young trails are spatially very dense and the cause of meteor outbursts when the Earth enters one.

The Leonids also produce meteor storms (very large outbursts) about every 33 years, during which activity exceeds 1,000 meteors per hour,[9] with some events exceeding 100,000 meteors per hour,[10] in contrast to the sporadic background (5 to 8 meteors per hour) and the shower background (several meteors per hour).

Meteoroids[6]
Size Apparent Magnitude Comparable in brightness
2 mm (0.08 in) +3.7 (visual) Delta Ursae Majoris
10 mm (0.4 in) −1.5 (bright) Sirius
20 mm (0.8 in) −3.8 (Fireball) Venus
  1. ^ Cite error: The named reference MAC was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference moore_rees2011 was invoked but never defined (see the help page).
  3. ^ a b c d e f g Cite error: The named reference AMS2023 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference aj116_1_499 was invoked but never defined (see the help page).
  5. ^ Byrd, Deborah (15 November 2018). "All you need to know: 2019's Leonid meteor shower". EarthSky. Archived from the original on 11 November 2019. Retrieved 26 February 2019.
  6. ^ a b Cite error: The named reference jenniskens2006 was invoked but never defined (see the help page).
  7. ^ McNaught, Robert H.; Asher, David J. (1999). "Leonid Dust Trails and Meteor Storms". WGN, Journal of the International Meteor Organization. 27 (2): 85–102. Bibcode:1999JIMO...27...85M.
  8. ^ Brown, Peter Gordon (1999). Evolution of Two periodic Meteoroid Streams: the Perseids and Leonids (Thesis). p. 4005. Bibcode:1999PhDT.........7B. Archived from the original on 5 June 2010. Retrieved 24 December 2009.
  9. ^ Sophie Lewis (16 November 2019). "Leonids meteor shower will soon light up the sky. Here's how to watch". CBS News. Archived from the original on 31 October 2020. Retrieved 18 August 2020.
  10. ^ Matthew Cappucci (18 November 2019). "Leonid shower a dud in 2019, but past years have featured extreme 'meteor storms'". The Washington Post. Archived from the original on 26 September 2020. Retrieved 18 August 2020.