হেলির ধুমকেতু (Halley's Comet)

 Halley's Comet, Comet Halley, or sometimes simply Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years.[1] Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and thus the only naked-eye comet that can appear twice in a human lifetime.[15] It last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.

                                  Discovery

Discovered by

Prehistoric (observation)

Edmond Halley (recognition of periodicity)

Discovery date

1758 (first predicted perihelion)

Orbital characteristics[1]

Epoch 4 August 2061 (2474040.5)

Aphelion

35.14 au

(aphelion: 9 December 2023)

Perihelion

0.59278 au[4]

(last perihelion: 9 February 1986)

(next perihelion: 28 July 2061)

Semi-major axis

17.737 au

Eccentricity

0.96658

Orbital period (sidereal)

74.7 yr

75y 5m 19d (perihelion to perihelion)

Mean anomaly

0.07323°

Inclination

161.96°

Longitude of ascending node

59.396°

Time of perihelion

28 July 2061

≈27 March 2134

Argument of perihelion

112.05°

Earth MOID

0.075 au (11.2 million km)

(epoch 1968)

TJupiter

-0.598

                    Physical characteristics

Dimensions

15 km × 8 km

Mean diameter

11 km

Mass

2.2×1014 kg

Mean density

0.6 g/cm3 (average)

0.2–1.5 g/cm3 (est.)

Escape velocity

~0.002 km/s

Synodic rotation period

2.2 d (52.8 h) (?)

Albedo

0.04

Apparent magnitude

28.2 (in 2003)