C/1990 K1 (Levy)
Non-periodic comet discovered by David H. Levy in 1990.
C/1990 K1 (Levy) is a non-periodic comet discovered by David H. Levy on 20 May 1990. It eventually grew bright enough to be seen without optical aid and holds the distinction of being the first comet observed by the Hubble Space Telescope.
Levy spotted the comet during his usual search routine, aiming a 40-cm reflector toward the star Alpheratz. At discovery, it shone at magnitude 9.6 with a tail roughly 2 arcminutes long, marking his sixth comet find. It was then 2.59 AU from the Sun and 3.07 AU from Earth. Confirmation came the next day, with other observers reporting magnitudes between 10 and 11. The first naked-eye sighting occurred on 23 July, when the comet reached magnitude 6.0; within a week, its tail stretched just over a degree. Brightening continued through August: John Bortle recorded magnitudes of 5.7 on the 3rd and 4.1 on the 28th, while S. Garro in France logged 3.6 on the 23rd. The tail became visible to the naked eye, though most detailed observations required optical aid, and by month’s end it extended about 3.5 degrees. The comet made its closest approach to Earth on 26 August 1990, at 0.43 AU (64 million km). During September, it faded slowly as it moved away from Earth but toward perihelion; by 20 September its magnitude hovered around 5. On 27 September, the Hubble Space Telescope captured it—the first comet it had ever observed. In October, only the Southern Hemisphere could see it, at magnitude 6, and perihelion occurred on 24 October. Solar elongation shrank to 24 degrees in November, limiting observations. Alan Hale recovered the comet on 10 December at magnitude 7, after which it began moving north. Over the next two months, tail lengths of 0.5 to 1.5 degrees were reported as the comet slowly dimmed. The final detection came on 1 April 1992, via CCD images from the Oak Ridge Observatory’s 155-cm reflector.
Because Comet Levy was well placed for study both before and after perihelion and remained fairly bright, scientists measured production rates of OH, NH, CN, C₂, and C₃ at various solar distances. Most species produced more material before perihelion, with hydroxyl showing the strongest asymmetry—its output peaked about a month before the others. On shorter timescales, the comet varied in both optical and ultraviolet light.
Quick Facts
- Discovery Ref
- IAUC_5017
- Discoverer
- David H. Levy
- Discovery Date
- 20 May 1990
- Designations
- 1990c, 1990 XX
- Orbit Ref
- jpl
- Epoch
- 1990-Oct-29.0
- Observation Arc
- 920 days
- Earliest Precovery Date
- 24 September 1989
- Perihelion
- 0.939 AU
- Eccentricity
- 1.00058
- Inclination
- 131.58°
- Asc Node
- 139.36°
Facts from the source article.
Lore & Background
David H. Levy discovered the comet on 20 May 1990 during his comet hunting routine, looking towards the star Alpheratz with a 40-cm reflector. He noted a magnitude of 9.6 and a tail about 2 arcminutes long. The comet was then 2.59 AU from the Sun and 3.07 AU from Earth. The discovery was confirmed the next day with reported magnitudes between 10 and 11. The first naked eye observation was reported on 23 July at magnitude 6.0. The comet brightened through August, with John Bortle reporting magnitudes 5.7 and 4.1 on 3 and 28 August respectively, and S. Garro reporting magnitude 3.6 on 23 August. The tail reached about 3.5 degrees long by the end of August. Closest approach to Earth was on 26 August 1990 at 0.43 AU. During September the comet faded slowly, and on 27 September it was observed by the Hubble Space Telescope, the first comet observed by HST. Perihelion occurred on 24 October. The comet was recovered on 10 December by Alan Hale at magnitude 7. It was last detected on 1 April 1992 in CCD images from the Oak Ridge Observatory.
Reader's Guide
Comet Levy was well positioned for observation both before and after perihelion and was quite bright. Scientific results include measurements of production rates for OH, NH, CN, C2, and C3, with most species having larger production before perihelion; hydroxyl showed the most pronounced asymmetry, peaking about a month before other molecules. The comet varied in optical and ultraviolet wavelengths, with an optical variation period estimated at 18.9 hours in late August, while the International Ultraviolet Explorer detected a period of 17.0 ± 0.1 hours on 18 September, though this did not fit well with earlier IUE observations, indicating the period decreased. HST observations on 27 September 1990 showed the coma brighter on the sunward side, suggesting sublimation primarily on the dayside, and an expanding dust arc that may explain periodic brightness changes. The velocity of H2O+ ions near the nucleus was about 10 km/s, accelerating to 50–70 km/s in the tail. ASTRO-1's Hopkins Ultraviolet Telescope detected carbon monoxide, atomic hydrogen, carbon, and sulfur. Methanol fluorescence was detected in infrared images, providing the first two-dimensional images of methanol distribution in a comet's coma. IRAM detected rotational lines of methanol and hydrogen sulfide, indicating formation at very low temperatures. Caltech submillimeter observatory detected hydrogen cyanide, formaldehyde, and methanol, with HCN rotational temperature estimated at 33 ± 1 K.
Did You Know?
- C/1990 K1 was the first comet observed by the Hubble Space Telescope, on 27 September 1990.
- The comet's closest approach to Earth was on 26 August 1990 at a distance of 0.43 AU.
- The comet was discovered by David H. Levy on 20 May 1990, his sixth comet discovery.
Frequently Asked Questions
Who discovered C/1990 K1 (Levy) and how did he find it?
David H. Levy identified the comet on 20 May 1990 while scanning the sky with his 40-cm reflector near the star Alpheratz. It was the sixth comet he had ever discovered, appearing at magnitude 9.6 with a small tail of about two arcminutes.
What makes C/1990 K1 (Levy) historically significant?
It holds the record as the first comet ever imaged by the Hubble Space Telescope. As a non-periodic visitor, it also made the news for becoming bright enough for unaided-eye observation during its 1990 apparition.
How close did C/1990 K1 (Levy) come to Earth?
The comet reached its closest approach on 26 August 1990, passing just 0.43 AU from our planet. Its perihelion, or closest point to the Sun, followed on 24 October 1990.
What is C/1990 K1 (Levy)'s orbital classification?
It is classified as a non-periodic (long-period) comet, meaning it does not return on a short, predictable cycle like short-period comets do. Its last confirmed detection was on 1 April 1992, after which it faded from view.
Why is C/1990 K1 (Levy) important to comet astronomy?
Beyond being the first Hubble-observed comet, it demonstrated how a modest 40-cm telescope could still find a new bright visitor in the 1990s. Its naked-eye visibility and multi-instrument study made it a popular target for both professional and amateur observers that year.
More in Named Comets, Part 2 1-24
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