C/1983 J1 (Sugano–Saigusa–Fujikawa)
Fourth closest comet approach to Earth in the 20th century.
C/1983 J1 (Sugano–Saigusa–Fujikawa) is a non-periodic comet discovered independently by three Japanese observers on 8 May 1983. It is notable for making the fourth closest observed approach of a comet to Earth in the 20th century, passing at a distance of 0.063 AU on 12 June 1983.
Quick Facts
- Discoverer
- Matsuo Sugano / Yoshikazu Saigusa / Shigehisa Fujikawa
- Discovery Date
- 8 May 1983
- Designations
- 1983e, 1983V
- Orbit Ref
- jpl
- Epoch
- 15 May 1983 (JD 2445469.5)
- Observation Arc
- 39 days
- Obs
- 55
- Aphelion
- 9,600 AU
- Perihelion
- 0.471 AU
- Semimajor
- 4,800 AU
- Eccentricity
- 0.9999
- Period
- 330,000 years
Facts from the source article.
Lore & Background
The comet was discovered on 8 May 1983 by three Japanese observers within 48 minutes: Matsuo Sugano using a 15-cm reflector, Yoshikazu Saigusa using a 0.20-m reflector, and Shigehisa Fujikawa using 12×120 binoculars, who estimated its magnitude to be 7. It had already passed perihelion on 1 May and was located in Andromeda at a solar elongation of 29 degrees. The comet faded slightly during May despite approaching Earth, with magnitude 8.3 on 20 May, then brightened in early June, reaching magnitude 6.6 on June 6 with a coma 15 arcminutes across. At closest approach on 12 June, it was visible to the naked eye at magnitude 5.5, appearing diffuse with a coma about one degree across. After that it faded rapidly, with magnitude 7.8 on 16 June, and was last detected on 20 June.
Reader's Guide
C/1983 J1 is significant as the fourth closest observed comet approach to Earth in the 20th century, passing just 0.063 AU away. Its close passage allowed detailed scientific observations. The Arecibo Observatory detected it in radiowaves on 11 June 1983, revealing a very small cross section of about 0.04 km², indicating a tiny nucleus with an effective radius of 0.37 km. Infrared and visual photometry confirmed this size. The radio spectrum showed lines of cyanoacetylene, while other species had only upper limits. Infrared observations on 13 June gave a water production rate of 1.1×10²⁸ mol/s, but levels of NH₂, CN, C₂, and C₃ were unusually low relative to [OI] compared to other comets. The dust/gas mass ratio was below 0.01 on 12 June, suggesting a gas-rich comet. Robert McNaught noted Earth would pass near the comet's orbit 2.9 days after the comet, possibly causing a meteor shower. Radar observations on 14 June recorded a small increase in short-duration meteors, and a similar shower in 1984 suggested the comet may have passed close to the Sun before 1983.
Did You Know?
- The comet was discovered independently by three Japanese observers within 48 minutes on 8 May 1983.
- Its closest approach to Earth on 12 June 1983 was the fourth closest observed comet approach in the 20th century.
- The comet's nucleus had an effective radius of only about 0.37 km, based on infrared and visual photometry.
- A possible meteor shower from the comet was detected by radar on 14 June 1983 and again in 1984.
Frequently Asked Questions
Who discovered C/1983 J1 (Sugano–Saigusa–Fujikawa)?
Three Japanese skywatchers—Matsuo Sugano, Yoshikazu Saigusa, and Shigehisa Fujikawa—each independently spotted the comet on 8 May 1983. It is a non-periodic (long-period) comet, so it does not return on a short, predictable cycle.
How close did C/1983 J1 pass to Earth?
The comet swept past Earth at a distance of 0.063 AU (roughly 9.4 million km) on 12 June 1983 at 19:00 UTC. That flyby ranks as the fourth closest observed comet approach to our planet in the entire 20th century.
How bright and how big was C/1983 J1 at closest approach?
At its nearest point the comet shone at an apparent magnitude of about 5.5, sitting right at the limit of naked-eye visibility under dark conditions. Its nucleus has an effective radius of approximately 0.37 km (± 0.05 km).
When did C/1983 J1 reach perihelion, and will it come back?
The comet reached perihelion on 1 May 1983, a few weeks before the Japanese observers first detected it. Because its orbit is non-periodic, it is not expected to swing back near the Sun within any human timescale.
Why do amateur astronomers consider C/1983 J1 a landmark event?
Its 0.063 AU flyby made it the fourth closest comet to Earth recorded in the 20th century, giving observers of that era a rare, bright target in the June 1983 sky. The independent triple discovery by three Japanese visual hunters also underscores how much dedicated naked-eye and small-telescope searching still contributes to comet science.
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