Five-kilometre-wide 3200 Phaethon’s 523½-day orbit brings it closer to the Sun than any other named asteroid. Rocky debris strewn along its orbit is responsible for the mid-December Geminid meteor shower. Phaethon passes just 0.069 astronomical units (10.3 million kilometres, 6.4 million miles or 26 lunar distances) from Earth at 23 UT (11pm GMT) on 16 December, making it a viable target for small telescopes for at least a week. Click the graphic to be taken to an interactive Java applet. Image credit: Orbit Viewer applet originally written and kindly provided by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL) / Ade Ashford (AN).
As shooting-star devotees prepare for the naked-eye spectacle of the Geminid meteor shower in mid-December, hopes are high that this active and consistent annual display will perform well under late evening skies unhindered by the light of a waning Moon. While one might expect a meteor per minute originating high in the southeast by midnight around the maximum on 14 December, owners of small telescopes can also witness the close passage of the meteors’ parent body — a curious “rock comet” known as 3200 Phaethon.
Magnitude +10.8 asteroid 3200 Phaethon leaves a trail 90 arcseconds long (about twice the angular size of Jupiter) against the stars of Perseus during this 4-minute exposure concluding at 18:57 UT on 13 December. A Canon 200mm f/2.8 prime lens and EOS 1100D DSLR on a Star Adventurer tracking mount were used to capture this image. Picture credit: Ade Ashford.Phaethon and the Geminids
Discovered on 11 October 1983, 3200 Phaethon has a highly eccentric orbit with a period of 523½ days that brings it closer to the Sun than any other named asteroid. Geminid meteors originate from particles shed by Phaethon and spread along its orbit. This rocky debris enters our planet’s atmosphere at speeds of around 35 kilometres (22 miles) per second, burning up in a flash of incandescence due to friction with the air. The Earth currently encounters Phaethon’s debris cloud between 8 and 17 December, passing through the thickest concentrations of dust on Thursday, 14 December when rates of around 100 meteors per hour can be expected under clear skies away from light pollution.
For ten nights starting 8 December, asteroid 3200 Phaethon is 12th-magnitude or brighter and well placed for Northern Hemisphere observers as it gallops through the constellations of Auriga, Perseus, Andromeda, Pisces and Pegasus at a rate of up to 15 degrees/day. The magnitude +11.4 asteroid passes 1¼ degrees south of Capella at 21 UT (9pm GMT) on Sunday, 10 December. Magnitude +10.7 Phaethon also clips the southern edge of open cluster M34 in Perseus as darkness falls in the UK on Thursday, 14 December. See the bottom of the page for detailed finder charts and nightly J2000.0 Epoch topocentric ephemerides for the UK, also applicable (with negligible parallax error) to observers in Western Europe. AN graphic by Ade Ashford.
Phaethon passes just 0.069 astronomical units (10.3 million kilometres, or 6.4 million miles) from Earth at 23 UT (11pm GMT) on 16 December, making it a viable target for telescopes of 10cm (4-inch) aperture and larger. For ten nights starting 8 December, the Apollo asteroid is 12th-magnitude or brighter and well placed for Northern Hemisphere observers as it gallops through the constellations of Auriga, Perseus, Andromeda, Pisces and Pegasus at a rate of up to 15 degrees/day. It passes 1¼ degrees south of Capella at 21 UT (9pm GMT) on Sunday, 10 December when its predicted magnitude is +11.4. Phaethon also clips the southern edge of open cluster M34 in Perseus as darkness falls in the UK on Thursday, 14 December when the asteroid should be at its peak brightness of magnitude +10.7.
If you don’t catch Phaethon this time around and wish to see it both closer and brighter, there’s a 76-year wait. The asteroid attains magnitude +9.4 on 14 December 2093, when it lies 0.0198 astronomical units (2.96 million kilometres, 1.84 million miles or 7.7 lunar distances) from our planet against the northern constellation backdrop of Boötes, motoring across the sky at a rate exceeding 57 degrees/day.
Night 1: evening of 8 December to morning of 9 December (UK dates)
Key to columns: the date in YYYY MM DD format and the Universal Time (UT), which is synonymous with GMT in the UK. Next is Phaethon’s right ascension (R.A.) and declination (Decl.) for the J2000.0 Epoch. The asteroid’s distance from Earth (Delta) and Sun (r) are measured in astronomical units (AU). Finally, Phaethon’s visual magnitude (Mag.).
Night 2: evening of 9 December to morning of 10 December (UK dates)
Night 3: evening of 10 December to morning of 11 December (UK dates)This detailed four-degree-wide finder chart shows the position of 3200 Phaethon at hourly intervals (small crosses) from 18h UT (6pm GMT) on 10 December to 06 UT (6am GMT) on 11 December. Stars as faint as magnitude +12 are shown. Note that the magnitude +11.4 asteroid passes 1¼ degrees south of prominent northern star Capella in the constellation of Auriga at 21 UT (9pm GMT) on Sunday, 10 December. The scale bar in the lower left corner is one degree (60 arcminutes) long. Click the graphic for a PDF version of this chart suitable for printing and using outside at the telescope. AN graphic by Ade Ashford.
Night 4: evening of 11 December to morning of 12 December (UK dates)
Night 5: evening of 12 December to morning of 13 December (UK dates)
Night 6: evening of 13 December to morning of 14 December (UK dates)
Key to columns: the date in YYYY MM DD format and the Universal Time (UT), which is synonymous with GMT in the UK. Next is Phaethon’s right ascension (R.A.) and declination (Decl.) for the J2000.0 Epoch. The asteroid’s distance from Earth (Delta) and Sun (r) are measured in astronomical units (AU). Finally, Phaethon’s visual magnitude (Mag.).
Night 7: evening of 14 December to morning of 15 December (UK dates)This detailed four-degree-wide finder chart depicts the border of constellations Perseus and Andromeda in the vicinity of open cluster M34. The position of 3200 Phaethon is shown at hourly intervals (small crosses) from 18h UT (6pm GMT) on 14 December to 01 UT (1am GMT) on 15 December. Stars as faint as magnitude +12 are revealed. Note that the magnitude +10.7 asteroid is near peak brightness this night and clips the southern edge of open cluster M34 in Perseus as darkness falls in the UK on Thursday, 14 December. The scale bar in the lower left corner is one degree (60 arcminutes) long. Click the graphic for a PDF version of this chart suitable for printing and using outside at the telescope. AN graphic by Ade Ashford.
Night 8: evening of 15 December to morning of 16 December (UK dates)
Night 9: evening of 16 December to morning of 17 December (UK dates)
Night 10: evening of 17 December to morning of 18 December (UK dates)
Night 11: evening of 18 December to morning of 19 December (UK dates)
This research has made use of data and/or services provided by the IAU’s Minor Planet Center, formatted by Ade Ashford.
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