C/1993 Y1 (McNaught–Russell)
Long-period comet possibly linked to a 6th-century apparition.
Comet McNaught–Russell (C/1993 Y1) is a long-period comet that peaked at magnitude 6.5 in early 1994, too faint to see with the naked eye. Robert H. McNaught and Kenneth S. Russell discovered it on a photographic plate taken by Russell on the night of 17 December 1993, using the UK Schmidt Telescope in Australia. Both astronomers worked at Siding Spring Observatory and together found five comets between 1991 and 1995. At discovery, the comet appeared as a diffuse trail of about magnitude 17.5 in the constellation Horologium.
Its orbit was initially calculated to have a period exceeding 1,400 years. François Colas of Paris Observatory and Ichiro Hasegawa noted that the comet’s path matched that of C/574 G1, recorded by Chinese observers from 4 April to 23 May in AD 574. This suggested a period of 1,430±30 years, making it the longest-period comet observed on two separate returns. Because the comet did not approach any planets, its orbit should remain largely unchanged, placing its next return around 3300. However, a 2024 study found that while the paths of the two comets may have run parallel southward, the tail length and brightness of the AD 574 object did not match historical records, ruling out that apparition as an earlier visit of McNaught–Russell.
Quick Facts
- Discovery Ref
- IAUC_5910
- Discoverer
- Robert H. McNaught / Kenneth S. Russell
- Discovery Site
- Siding Spring Observatory
- Discovery Date
- 17 December 1993
- Designations
- 1994 XI, 1993v
- Orbit Ref
- jpldata · barycenter
- Epoch
- 28 April 1994 (JD 2449470.5)
- Observation Arc
- 265 days
- Obs
- 377
- Perihelion
- 0.8676 AU
- Aphelion
- 270 AU (inbound) / 240 AU (outbound)
- Eccentricity
- 0.9932IAUC_5943
Facts from the source article.
Lore & Background
The comet was first spotted by Robert McNaught from a photographic plate exposed by Kenneth Russell on the night of 17 December 1993. At the time of discovery, the comet was a diffuse trail about magnitude 17.5 within the constellation Horologium. Its orbital period was initially estimated at over 1400 years.
Francois Colas and Ichiro Hasegawa noted that the path of McNaught–Russell coincided with that of comet C/574 G1, recorded in AD 574 over a period from April 4 to May 23 by observers in China. This would give the comet a period of 1430±30 years, making it the longest-period comet seen on two separate returns. Since the comet was not observed to approach any planets, its orbit should remain largely unchanged, placing its next approach around 3300.
However, a 2024 study concluded that while the paths of the 574 AD comet and Comet McNaught–Russell may have run parallel southward, the expected tail length and brightness did not match the historical records, ruling out the possibility that this was an earlier apparition.
Reader's Guide
Comet McNaught–Russell is notable for its potential identification with a comet observed in AD 574, which would have made it the longest-period comet ever recorded on two separate returns. The initial orbital period estimate of over 1400 years was refined to 1430±30 years based on this possible linkage. However, a 2024 study cast doubt on the identification, noting discrepancies in tail length and brightness between the historical record and what would be expected for McNaught–Russell. Because the comet did not approach any planets, its orbit is expected to remain largely unchanged, with its next return to the inner Solar System predicted around 3300. The comet was discovered by Robert H. McNaught and Kenneth S. Russell, who together discovered five comets between 1991 and 1995 using the UK Schmidt Telescope at Siding Spring Observatory. Its maximum brightness of magnitude 6.5 placed it just below naked-eye visibility in early 1994.
Did You Know?
- The comet was discovered from a photographic plate exposed by Kenneth Russell on 17 December 1993.
- Its orbital period was initially estimated at over 1400 years, later refined to 1430±30 years.
- A 2024 study ruled out its identification with a comet recorded in AD 574 due to mismatched tail length and brightness.
Frequently Asked Questions
Who discovered C/1993 Y1 (McNaught–Russell)?
Robert H. McNaught and Kenneth S. Russell, both astronomers at Siding Spring Observatory in Australia, identified the comet on a photographic plate that Russell had captured on the night of 17 December 1993 using the UK Schmidt Telescope.
How bright did C/1993 Y1 (McNaught–Russell) get at its peak?
The comet brightened to roughly magnitude 6.5 in early 1994, placing it just beyond the limit of easy naked-eye visibility for most observers under dark skies.
What did C/1993 Y1 (McNaught–Russell) look like when it was first found?
On the discovery plate it appeared as a faint, diffuse trail of about magnitude 17.5 located in the southern constellation Horologium.
What is C/1993 Y1 (McNaught–Russell)'s orbital period?
Initial orbit calculations placed its period at well over 1,400 years, firmly classifying it as a long-period comet returning from the outer solar system.
Is C/1993 Y1 (McNaught–Russell) possibly the same comet seen in antiquity?
Some researchers have proposed a tentative link between this object and a recorded apparition from the sixth century, though the connection has not been definitively confirmed.
More in Named Comets, Part 5 1-24
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