C/2004 F4 (Bradfield)
 The comet in the dawn sky | |
| Discovery[1] | |
|---|---|
| Discovered by | William A. Bradfield |
| Discovery date | 23 March 2004 |
| Orbital characteristics[2] | |
| Epoch | 2004-Jun-01.0 |
| Observation arc | 155 days |
| Aphelion | 475 AU |
| Perihelion | 0.168 AU |
| Semi-major axis | 238 AU |
| Eccentricity | 0.99929 |
| Orbital period | 3,660 years |
| Inclination | 63.16° |
| 222.78° | |
| Argument of periapsis | 332.79° |
| Last perihelion | 17 April 2004 |
| Earth MOID | 0.32 AU |
| Jupiter MOID | 0.56 AU |
| Comet total magnitude (M1) | 11.3 |
C/2004 F4 (Bradfield) is a non-periodic comet discovered by amateur astronomer William A. Bradfield on 23 March 2004.[1] The comet brightened to an apparent magnitude of about 3.3.[3]
Observational history
[edit]The comet was discovered by amateur astronomer William A. Bradfield from Yankalilla, South Australia on 23 March 2004 with a 0.25-m reflector telescope, during his search for sungrazing comets. That was Bradfield's 18th comet discovery. The comet was then located in evening twilight and its magnitude was estimated to be about magnitude 8. Robert H. McNaught observed the comet on 9 April 2004 and estimated that the comet had a magnitude of 5, while Terry Lovejoy estimated its magnitude to be 3.3 on 12 April, while its tail measured half a degree long.[1] At that time, two more naked eye comets were visible in the sky, C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR).[3]
The comet reached perihelion on 17 April 2004, at a distance of 0.168 AU (25.1 million km; 15.6 million mi).[2] The comet became visible in the C3 coronograph of the Solar and Heliospheric Observatory (SOHO) between 16 and 20 April 2004.[4] The comet had a bright head and a long white tail.[5] The appearance of the comet was in the coronograph was unusual, with the coma growing perpendicularly to the apparent motion, and thus indicating a growing dust tail, while on 19 April a series of structures were seen near the head, probably streamers or striae. If these were streamers, they indicated an uprise in activity every 0.5 day.[6] The orbital ephimeris based on the SOHO observations indicated that the comet on 20 April had an magnitude of 2.5.[6]
The comet was spotted in bright twilight on 22 April, when the comet had an estimated magnitude of about 4 to 4.5.[7] On 25 April, while the comet was estimated to have a same magnitude, its tail was estimated to 8.5 degrees long with naked eye, while on 27 April the tail length was estimated to be 10 degrees with 7×35 binoculars, while the comet was estimated to have a magnitude of 5. On 30 April the apparent magnitude was estimated to be 5.8 while the tail was estimated to be 3.5 degrees long.[8]
On 2–3 May, Earth crossed the orbital plane of the comet. As a result, a sunward spike (or anti-tail) and a ray-shaped structure in the dust tail.[9]
References
[edit]- ^ a b c "IAUC 8319: C/2004 F4". www.cbat.eps.harvard.edu. 12 April 2004. Retrieved 28 August 2023.
- ^ a b "Small-Body Database Lookup: C/2004 F4 (Bradfield)". ssd.jpl.nasa.gov.
- ^ a b "Brightest comets seen since 1935". www.icq.eps.harvard.edu. Retrieved 26 August 2023.
- ^ "Pick of the Week: Comet Bradfield Coming into View (April 15, 2004)". soho.nascom.nasa.gov. Retrieved 28 August 2023.
- ^ "SOHO-Gallery: Best Of SOHO". soho.nascom.nasa.gov. Retrieved 28 August 2023.
- ^ a b "IAUC 8326: C/2004 F4". www.cbat.eps.harvard.edu. 20 April 2004.
- ^ "IAUC 8329: 2004bj, 2004bk; C/2002 T7; 1999 DJ_4; C/2004 F4". www.cbat.eps.harvard.edu. 23 April 2004.
- ^ "IAUC 8334: 2004bl; C/2003 N2, O4-O8, P1,, P2; C/2004 F4". www.cbat.eps.harvard.edu. 30 April 2004.
- ^ Pansecchi, L.; Scardia, M. (February 2005). "A neck-line structure in the dust tail of Comet C/2004 F4 (Bradfield)". Astronomy & Astrophysics. 430 (3): 1129–1132. doi:10.1051/0004-6361:20041766.
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