3200 Pheathon

Click on image to enlarge

Object: 3200 Pheathon

Type: Asteroid 

Distance: 0.0797 AU (11.9 million km) 

Constellation: Perseus/Andromeda

Date: 14 December 2017
Equipment: SXV-H9, Vixen 114mm f5.3 ED refractor

Subframes: 322 x 3s, 17s between frames

The above image shows the track of NEO (Near Earth Object) 3200 Pheathon (pronounced Fay-Ath-On - I think!) as it crossed the Perseus/Andromeda border during the early evening of 14th. December. The field is about a degree wide (52' to be precise).

Images were acquired in Astroart, with selected frames stacked and time-annotated in PaintShopPro. Magnitude of the asteriod appeared to be around 10.7 when compared with similarly bright stars in the image.

The three brightest stars in the image have been labelled by way of positional reference.

Above is a GIF animation using all 322 frames, showing the progression of the asteroid.  A stray meteor crosses the field about a second into the video. I don't think it's a satellite (couldn't find evidence of one in the region at the time from various web searches) or a Geminid (wrong radiant).

3200 Phaethon (1983 TB) was discovered on Oct. 11 1983 by NASA's Infrared Astronomical Satellite (IRAS). Phaethon is the third largest near-Earth asteroid classified as "Potentially Hazardous" after 53319 1999 JM8 (~7 km) and 4183 Cuno (~5.6 km). At over 3 miles wide and moving at 20 km/s, one can only imagine the devastation that this potential "dinosaur killer" might cause were it to strike the UK.

Probably not as much as Brexit of course, although unlike Brexit, there is no risk of such an impact coming to pass in the foreseeable future.

Phaethon is categorized as an Apollo asteroid, as its orbital semi-major axis is greater than that of the Earth's at 1.27 AU (190 million km). It is also suspected to be a member of the Pallas family of asteroids.

Phaethon has an unusually high eccentricity of 0.890 and a perihelion (closest approach to the Sun) of 0.140 AU, the smallest known in the near-earth asteroid population. Its surface temperature at perihelion reaches around 750 C.

Due to the close perihelion, Phaethon is named for the Greek mythological son of Helios (the Sun god). In Greek mythology, Phaethon drove his father's chariot for one day, lost control of its horses, and nearly set the Earth on fire.

On December 16, at its closest approach, the asteroid was only 6.4 million miles (10.3 million kilometers) away, the nearest it will be until 2093. The radar images below were taken by the Arecibo Observatory Planetary Radar during its close fly-by, and have allowed astronomers to distinguish details of its surface.

These images, captured at a resolution of 250 feet (75 meters) per pixel, show the asteroid to be spheroidal in shape, with a diameter of roughly 3.6 miles (6 kilometers). The researchers also used Arecibo’s radar to spot a depression near 3200 Phaethon’s equator that stretches a few hundred meters at minimum, as well as a dark, spherical spot close to one of the asteroid’s poles.

Phaethon’s highly eccentric orbit more closely resembles that of a comet than an asteroid; it has been referred to as a "rock comet".

Phaethon is widely thought to be the parent body for the Geminid meteor stream due to similarities between its orbit and that of the meteors. Most meteor streams are associated with comets, suggesting that Phaethon may be an inactive comet nucleus, although in recent studies performed by NASA's STEREO spacecraft, dust tails have been observed and in 2010, Phaethon was detected ejecting dust.