While rapture-ready folks are celebrating today, the flyby of 3200 Phaeton has been known for years and is not considered a threat to our survival by science. One YouTube video even explains that 3200 Phaeton proves Barack Obama is the anti-Christ due to Oprah declaring he is “the one” on some tangentially associated date and that Phaeton sounds like Python–more proof–and that Phaeton is a destroyer in mythology, and, and…) In fact, NASA recently explained Phaeton in connection with the Geminids Meteor Shower which peaked December 13-14, 2017.
“About the Geminid Shower
The Geminids are active every December, when Earth passes through a massive trail of dusty debris shed by a weird, rocky object named 3200 Phaethon. The dust and grit burn up when they run into Earth’s atmosphere in a flurry of “shooting stars.”
“Phaethon’s nature is debated,” said Cooke. “It’s either a near-Earth asteroid or an extinct comet, sometimes called a rock comet.”
As an added bonus this year, astronomers will have a chance to study Phaethon up close in mid-December, when it passes nearest to Earth since its discovery in 1983.”
Asteroid Phaethon NASA Fact Sheet 12.13.10
The Geminids are a unique meteor shower in that their identified parent body is not a comet, but what seems to be an asteroid! Of the meteor showers with known parent bodies studied by meteor scientists, the Geminids are the only shower to have an asteroidal parent body; all others have a cometary origin. 3200 Phaethon measures 5.10 km in diameter which increases the ‘unique’ factor; considering the amount of debris we see, we would expect Phaethon to be a much larger body!
Phaethon was discovered on October 11, 1983 using the Infrared Astronomical Satellite, and named after the Greek myth of Phaethon, son of the sun god Helios, due to its close approach to our Sun.
Phaethon is technically classified as an asteroid — the first to be discovered via satellite. But how could an asteroid produce meteoroids that cause the Geminids? One theory is that Phaethon broke apart from another object, ejecting meteoroids as a part of the breakup. This doesn’t agree with other things we know, however. Another theory is that a collision with another object thousands of years ago could have produced debris that Earth now travels through. This theory appears to be unlikely as well, based on other evidence. Another theory assumes Phaethon to be a dead comet (the spent nucleus of a comet whose ices had been sublimated away) that produced debris in the past that now intersects Earth’s orbit. But no evidence for mass loss from the object has ever been reported…. until recently. In 2009 the NASA spacecraft STEREO-A observed 3200 Phaethon to brighten by a factor of two, quite unexpectedly. This brightening at perihelion was likely due to a release of dust from the object, possibly due to heating and cracking of the surface rocks as Phaethon came close to the Sun. That brings us to the fourth theory, that Phaethon is a rock comet. The problem with this theory is that it doesn’t account for the amount of dust in the Geminid stream.
So what it comes down to is that the Geminid parent object is a mystery.
Goldstone Radar Observations Planning: Asteroid 3200 Phaethon
3200 Phaethon (1983 TB) was discovered on 1983 Oct. 11 by NASA's Infrared Astronomical Satellite (IRAS).
With a diameter of about 5 km, Phaethon is the third largest near-Earth asteroid classified as "Potentially Hazardous"
after 53319 1999 JM8 (~7 km) and 4183 Cuno (~5.6 km).
Phaethon has an unusually high eccentricity of 0.890 and a perihelion of 0.140 au
that is among the smallest known in the near-Earth asteroid population. 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.
Phaethon will approach within 0.069 au of Earth on 2017 December 16 when it will be a strong
radar imaging target at Goldstone and Arecibo. This will be the best opportunity to date for radar observations
of this asteroid and we hope to obtain detailed images with resolutions as fine as 75 m/pixel at Goldstone
and 15 m/pixel at Arecibo. The images should be excellent for obtaining a detailed 3D model.
Extensive photometric observations by many observers have yielded a rotation period of 3.6 h, a lightcurve amplitude
of up to ~0.4 mag, and a pole direction of (lambda, beta) = (85+- 13, -20+-10) deg (Ansdell et al. 2014).
Ansdell et al. also obtained axis ratios of x/y = 1.04 and x/z = 1.14, so Phaethon appears relatively unelongated
along its equator but somewhat flattened at its poles.
Spectroscopic observations by several observing teams strongly suggest that Phaethon is an optically-dark B-class
object. However, thermal infrared observations dating back to the 1990s by Harris et al. give an optical
albedo of 0.11 that seems somewhat bright for the B class. More recent observations by NASA's NEOWISE
mission have detected Phaethon and could provide an update on the diameter and albedo.
Phaethon was detected by radar at Arecibo in December 2007. Due to equipment problems, the 2007 data
consist of a modest number of echo power spectra and a handful of delay-Doppler images from two days.
Echo power spectra obtained at Arecibo in 2007 were strong and provided a maximum bandwidth of 44 Hz.
Combined with the rotation period of 3.6 h, the bandwidth places a lower bound on the maximum pole-on dimension
of about 5.7 km. The 2007 delay-Doppler images show a rounded object, which is consistent with the shape of the echo
power spectra, but were relatively weak and do not show detailed surface features.
The 2007 Arecibo observations have a radar cross section of about 2.4 km^2, that, if we adopt a diameter of
5.1 km, imply a radar albedo of 0.12. As such, the SNRs in the tables below could be too low by about 20%.
Phaethon is widely thought to be the parent body for the Geminids meteor stream due to similarities between
its orbit and that of the meteors (Whipple 1983; Williams and Wu 1993). Most meteor streams are associated with comets,
so this raises the question of whether Phaethon could be an inactive comet nucleus.
Observations by Jewitt and colleagues have revealed episodic activity by Phaethon, but have not, to date,
shown the signature of particles as large as those in the Geminids meteors. The implication is that Phaethon
experiences occasional outbursts that produce particles far larger than any seen so far. As such, Phaethon is an unusual
object that appears asteroidal most of the time but occasionally shows low levels of activity when it is
near perihleion. Phaethon is classified as an asteroid,
not as a comet, and despite the high eccentricity, the object's Tisserand parameter is not cometary.
The 2017 apparition is the closest to Earth since the asteroid's discovery
so it may be possible for optical observers to detect new activity. If Phaethon shows
unexpectedly strong activity in 2017, then there is a small (perhaps very small) chance that CW radar observations
might reveal echoes from a cloud of small particles similar to the "skirts" seen in radar observations of
active comet nuclei.
The very low perihelion of Phaethon makes it a possible candidate for detecting general relativistic
and/or solar oblateness effects in its orbital motion (Margot and Giorgini 2010), so one of our principal
objectives is to obtain high-resolution radar ranging measurements to support this effort.
Phaethon will be brighter than 16th magnitude for about one month from November-December 2017.
Phaethon is predicted to reach 11th magnitude in mid-December when it will be visible in small telescopes
for experienced observers at sites with dark skies.
Phaethon is potentially detectable at Goldstone for about three weeks and tracks are scheduled on
ten days between Dec. 11-21.
Due to its relatively rapid motion in declination, Phaethon is visible at Arecibo on only five days
from Dec. 15-19 and observations are scheduled on all of those dates.
We may also request time at Green Bank to receive Goldstone transmissions.
The 2017 encounter is the closest by this asteroid since 1974 and until 2093.
Phaethon is classified as a "Potentially Hazardous Asteroid" by the Minor Planet Center.
Orbital and Physical Characteristics
Discovery date 1983 Oct 11
orbit type Apollo
Close approach date 2017 Dec 16
Close approach dist. 0.0689 au
Close approach dist. 26.8 lunar distances
semimajor axis 1.271 au
inclination 22.2 deg
orbital period 1.433 y
perihelion distance 0.140 au
aphelion distance 2.402 au
MOID 0.0206 au
Tisserand parameter 4.510 (asteroidal)
absolute magnitude (H) 14.6
diameter 5.1 km
optical albedo 0.11
spectral class F, B
rotation period 3.603 h
lightcurve amplitude 0.11 - 0.44 mag
pole direction lambda = 85 deg, beta = -20 deg
Phaethon Close Earth Approaches Within 0.15 au:
Date (TDB) Body CA Dist MinDist MaxDist Vrel TCA3Sg Nsigs P_i/p
A.D. 1631 Dec 04.87057 Earth .129451 .129448 .129455 37.463 0.28 8.94E5 .000000
A.D. 1723 Dec 05.57449 Earth .145430 .145389 .145471 38.105 2.71 6.83E5 .000000
A.D. 1746 Dec 06.19456 Earth .128707 .128685 .128730 37.584 1.48 6.47E5 .000000
A.D. 1769 Dec 05.41186 Earth .142850 .142847 .142853 38.059 0.18 6.18E5 .000000
A.D. 1802 Dec 07.50563 Earth .128020 .127994 .128046 37.576 1.69 5.65E5 .000000
A.D. 1812 Dec 14.41557 Earth .075414 .075392 .075436 31.957 1.32 5.41E5 .000000
A.D. 1845 Dec 08.17934 Earth .111777 .111762 .111792 37.074 0.95 5.05E5 .000000
A.D. 1855 Dec 15.93005 Earth .086277 .086264 .086289 31.544 0.70 4.93E5 .000000
A.D. 1888 Dec 09.19404 Earth .088686 .088677 .088694 36.336 0.56 4.43E5 .000000
A.D. 1898 Dec 16.74220 Earth .107786 .107778 .107794 30.863 0.40 4.47E5 .000000
A.D. 1931 Dec 13.50144 Earth .038389 .038386 .038392 34.597 0.21 3.88E5 .000000
A.D. 1964 Dec 08.70985 Earth .131281 .131280 .131283 37.774 0.09 4.10E5 .000000
A.D. 1974 Dec 16.36240 Earth .054746 .054745 .054747 32.365 0.07 3.49E5 .000000
A.D. 2007 Dec 10.19673 Earth .120896 .120896 .120896 37.446 0.02 4.10E6 .000000
A.D. 2017 Dec 16.95810 Earth .068932 .068932 .068932 31.888 0.03 5.45E5 .000000
A.D. 2050 Dec 11.82259 Earth .082569 .082568 .082571 36.236 0.09 2.86E5 .000000
A.D. 2060 Dec 18.48085 Earth .111131 .111129 .111133 30.648 0.08 2.72E5 .000000
A.D. 2093 Dec 14.45306 Earth .019812 .019810 .019813 34.234 0.14 1.69E5 .000000 Wow...
A.D. 2136 Dec 13.92650 Earth .055065 .055062 .055068 35.401 0.20 6.11E5 .000000
A.D. 2146 Dec 19.83488 Earth .090252 .090248 .090255 31.170 0.16 98428. .000000
A.D. 2189 Dec 15.24219 Earth .035481 .035478 .035485 34.795 0.21 74794. .000000
A.D. 2199 Dec 20.58935 Earth .094898 .094896 .094899 31.016 0.06 2.44E5 .000000
A.D. 2242 Dec 14.61151 Earth .091625 .091613 .091636 36.502 0.68 62050. .000000
A.D. 2252 Dec 19.01935 Earth .033027 .033013 .033041 32.755 0.72 51202. .000000
A.D. 2295 Dec 15.68761 Earth .079921 .079893 .079949 36.095 1.62 1.19E5 .000000
A.D. 2305 Dec 22.37725 Earth .084068 .084034 .084103 31.292 1.67 1.56E5 .000000
A.D. 2348 Dec 18.51981 Earth .026363 .026291 .026435 34.388 4.49 2.31E5 .000000
A.D. 2358 Dec 23.35001 Earth .096338 .096314 .096363 30.968 1.17 2.57E5 .000000
A.D. 2401 Dec 15.20440 Earth .122133 .121893 .122374 37.327 14.55 3.24E5 .000000
A.D. 2411 Dec 20.98099 Earth .021385 .021209 .021565 33.333 18.19 3.47E5 .000000
A.D. 2454 Dec 15.03196 Earth .141051 .138488 .143615 37.905 157.41 4.26E5 .000000
A.D. 2464 Dec 20.49665 Earth .025300 .024373 .026604 33.392 174.52 4.52E5 .000000
Phaethon also makes repeated close encounters with Venus, Mercury, and 15 Eunomia.
Last update: 2017 Dec 14