* Astronomy

Blobrana · L

Asteroid (3200) Phaethon

Blobrana · L

Asteroid (3200) Phaethon is at Opposition in the constellation Auriga on the 11th December 2017.

Magnitude: 11.3 V
Distance to Earth: 0.124 AU (48.2 lunar distances)
Distance to Sun: 1.100 AU

Blobrana · L

Title: Resurrection of (3200) Phaethon in 2016
Author: Man-To Hui, Jing Li

We present a study of the active asteroid (3200) Phaethon in the 2016 apparition using the STEREO spacecraft and compare the results with data from the previous two perihelia in 2009 and 2012. Once again, Phaethon brightened by ~2 mag soon after its perihelion passage, contradicting expectations from the phase function of a macroscopic monolithic body. Subsequently, a short antisolar tail of ~0.1° in length was formed within ~1 day and quickly disappeared. No trail was seen. Our syndyne-synchrone analysis indicates that the tail was comprised of submicron to micron particles and can be approximated by a synchrone coinciding with the outburst. We estimate that the outburst has released a mass of ~10^4--10^5 kg, comparable to the two mass ejections in 2009 and 2012, and that the average mass-loss rate is ~0.1--1 kg s^-1. The forward-scattering effect hinted at low level activity of Phaethon prior to the outburst, which increased the effective cross section by merely \lesssim 1 km^2. Without the forward-scattering enhancement, detecting such activity at side-scattering phase angles is very difficult. The forward-scattering effect also reinforces that the ejected dust grains rather than gas emissions were responsible for the activity of Phaethon. Despite Phaethon's reactivation, it is highly unlikely that the Geminid meteoroid stream can be sustained by similar perihelion mass-loss events.

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Blobrana · L

RE: Asteroid 3200 Phaethon (1983 TB)

Blobrana · L

A suggestion for CCD imagers (Phaethon is an asteroid and the parent body of the Geminid meteor shower): https://t.co/YgYIaoh9nr pic.twitter.com/KuuS35pMY1
Jan Hattenbach (@JanHattenbach) September 25, 2016

Blobrana · L

Asteroid (3200) Phaethon

Blobrana · L

RE: Asteroid 3200 Phaethon (1983 TB)

Blobrana · L

Asteroid (3200) Phaethon, at mag 16.7, will pass 0.56° from Mars at 23:00 UT, 1st September 2013.

Ephemeris

Date             UT      R.A. (J2000) Decl.         Delta     r         El.    Ph.     Mag
2013 08 31 000000 08 11 25.0 +20 46 30   1.581   0.986   37.1  38.1  17.1
2013 09 01 000000 08 15 56.8 +20 24 19   1.562   0.969   36.9  38.8  17.0
2013 09 02 000000 08 20 34.1 +20 01 07   1.544   0.952   36.8  39.4  17.0
2013 09 03 000000 08 25 16.9 +19 36 53   1.525   0.934   36.6  40.0  17.0
2013 09 04 000000 08 30 05.4 +19 11 34   1.507   0.916   36.3  40.7  16.9
2013 09 05 000000 08 34 59.9 +18 45 07   1.489   0.898   36.1  41.4  16.9
2013 09 06 000000 08 40 00.7 +18 17 29   1.472   0.880   35.8  42.0  16.8

Blobrana · L

Title: The Dust Tail of Asteroid (3200) Phaethon
Authors: David Jewitt, Jing Li, Jessica Agarwal

We report the discovery of a comet-like tail on asteroid (3200) Phaethon when imaged at optical wavelengths near perihelion. In both 2009 and 2012, the tail appears >=350" (2.5x10^8 m) in length and extends approximately in the projected anti-solar direction. We interpret the tail as being caused by dust particles accelerated by solar radiation pressure. The sudden appearance and the morphology of the tail indicate that the dust particles are small, with an effective radius ~1 micrometer and a combined mass ~3x10^5 kg. These particles are likely products of thermal fracture and/or desiccation cracking under the very high surface temperatures (~1000 K) experienced by Phaethon at perihelion. The existence of the tail confirms earlier inferences about activity in this body based on the detection of anomalous brightening. Phaethon, the presumed source of the Geminid meteoroids, is still active.

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Blobrana · L

Title: Recurrent Perihelion Activity in (3200) Phaethon
Authors: Jing Li, David Jewitt

We present a study of planet-crossing asteroid (3200) Phaethon at three successive perihelia in 2009, 2010 and 2012, using the NASA STEREO spacecraft. Phaethon is clearly detected in 2009 and 2012, but not in 2010. In both former years, Phaethon brightened unexpectedly by ~1 magnitude at large phase angles, inconsistent with the ~1 magnitude of steady fading expected from a discrete, macroscopic body over the same phase angle range. With a perihelion distance of 0.14 AU and surface temperatures up to ~1000 K, a thermal origin of this anomalous brightening is strongly suspected. However, simple thermal emission from Phaethon is too weak, by a factor >1000, to explain the brightening. Neither can ice survive on this body, ruling out comet-like sublimation. Our preferred explanation is that brightening occurs as a result of dust produced and ejected from Phaethon, perhaps by thermal fracture and/or thermal decomposition of surface minerals when near perihelion. A contribution from prompt emission by oxygen released by desiccation of surface minerals cannot be excluded. We infer an ejected mass of order 4x10^8 a_mm kg per outburst, where a_mm is the mean dust radius in millimetres. For plausible dust radii, this mass is small compared to the estimated mass of Phaethon (~2x10^14 kg) and to the mass of the Geminid stream (10^12 kg to 10^13 kg) with which Phaethon is dynamically associated. Perihelion mass-loss events like those observed in 2009 and 2012 contribute to, but do not necessarily account for the Geminids stream mass.