Rock comet
   HOME

TheInfoList



OR:

3200 Phaethon (; previously sometimes spelled Phæton), provisionally designated , is an
active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * "Active" (song), a 2024 song by Asake and Travis Scott from Asake's album ''Lungu Boy'' * Active Records, a record label Ships * ''Active'' (ship), several com ...
Apollo asteroid The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Ear ...
with an orbit that brings it closer to the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
than any other named asteroid (though there are numerous unnamed asteroids with smaller perihelia, such as ). For this reason, it was named after the
Greek Hero Hero cults were one of the most distinctive features of ancient Greek religion. In Homeric Greek, "hero" (, ) refers to the mortal offspring of a human and a god. By the historical period, the word came to mean specifically a ''dead'' man, vene ...
, Phaëthon, son of the sun god
Helios In ancient Greek religion and Greek mythology, mythology, Helios (; ; Homeric Greek: ) is the god who personification, personifies the Sun. His name is also Latinized as Helius, and he is often given the epithets Hyperion ("the one above") an ...
. It is in
diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...
and is the
parent body A parent body in meteoritics is the celestial body from which originates a meteorite or a class of meteorites. Identification It is easiest to correlate a meteorite with a parent body when the parent body still exists. This is the case for Lun ...
of the
Geminids The Geminids are a prolific meteor shower with 3200 Phaethon (which is thought to be an Apollo asteroid with a " rock comet" orbit.) being the parent body. Because of this, it would make this shower, along with the Quadrantids, the only ...
meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at ext ...
of mid-December. With an
observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...
of 35+ years, it has a very well determined orbit. The 2017 Earth approach distance of about 10 million km was known with an accuracy of ±700 m.


Discovery

Phaethon was the first asteroid to be discovered using images from a spacecraft.
Simon F. Green Simon F. Green (born 1959) is an astronomer. He is a Senior Lecturer in Planetary and Space Science at the Open University. He specializes in the study of asteroids and trans-Neptunian objects, and for a long time worked with the IRAS satellite to ...
and John K. Davies discovered it in images from October 11, 1983, while searching
Infrared Astronomical Satellite The Infrared Astronomical Satellite ( Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mo ...
(IRAS) data for moving objects. It was formally announced on October 14 in IAUC 3878 along with optical confirmation by
Charles T. Kowal Charles Thomas Kowal (November 8, 1940 – November 28, 2011) was an American astronomer known for his observations and discoveries in the Solar System. As a staff astronomer at Caltech's Mount Wilson and Palomar Mountain observatories between ...
, who reported it to be asteroidal in appearance. Its provisional designation was , and it later received the numerical designation and name in 1985.


Orbital characteristics

Phaethon is categorized as an
Apollo asteroid The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Ear ...
, as its orbital
semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...
is greater than that of the
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
's at . It is also suspected to be a member of the
Pallas family The Pallas family (''adj. Palladian''; ) is a small asteroid family of B-type asteroids at very high Orbital inclination, inclinations in the intermediate asteroid belt. The family was identified by Kiyotsugu Hirayama in 1928. The namesake of the ...
of asteroids. Its most remarkable distinction is that it approaches the Sun closer than any other named asteroid: its
perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
is only — less than half of Mercury's perihelial distance. It is a Mercury-, Venus-, Earth-, and
Mars-crosser A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and . Many databases, for i ...
as a result of its high orbital eccentricity. The surface temperature at perihelion could reach around . Phaethon is a possible candidate for detecting general relativistic and/or solar
oblateness Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid) respectively. Other terms used are ellipticity, or oblateness. The usual notation for flattening is f ...
effects in its orbital motion due to the frequent close approaches to the Sun. The Apollo asteroids (155140) 2005 UD and (225416) 1999 YC share similar orbits with Phaethon, suggesting a possible common breakup origin.


Potentially hazardous asteroid

Phaethon is categorized as a
potentially hazardous asteroid A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. Th ...
(PHA), but that does not mean there is a near-term threat of an impact. It is a potentially hazardous asteroid merely as a result of its size ( absolute magnitude ) and Earth
minimum orbit intersection distance Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits o ...
). The Earth minimum orbit intersection distance (E-MOID) is , which is defined by the shortest distance between the orbit of Phaethon and the orbit of Earth. With a 30+ year observation arc, the orbit of Phaethon is very well understood with very small uncertainties. Close approaches of Phaethon are well constrained for the next 400 years.


Physical characteristics

Phaethon is an asteroid with fairly unusual characteristics in that its orbit more closely resembles that of a
comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
than an asteroid; it has been referred to as a "rock comet". In studies performed by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
's
STEREO Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
spacecraft in 2009 and 2012, rapid brightening and dust tail have been observed. It is possible that the Sun's heat is causing fractures similar to
mudcrack Mudcracks (also known as mud cracks, desiccation cracks or cracked mud) are sedimentary structures formed as muddy sediment dries and contracts.Jackson, J.A., 1997, ''Glossary of Geology'' (4th ed.), American Geological Institute, Alexandria, VA ...
s in a
dry lake A dry lake bed, also known as a playa (), is a basin or depression that formerly contained a standing surface water body, which disappears when evaporation processes exceed recharge. If the floor of a dry lake is covered by deposits of alkalin ...
bed. This occurs because Phaethon's orbit takes it closer to the Sun than any other named asteroid (0.14  AU at
perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
) causing extreme heating and enough
solar radiation pressure Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of ...
to push any separated pieces off the asteroid's surface. Since its discovery, several other objects were found exhibiting mixed cometary and asteroidal features, such as 133P/Elst–Pizarro, leading to a new class of objects dubbed "
active asteroid Active asteroids are small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a coma, tail, or other visual evidence of mass-loss (like a comet), but their orbits remain within Jupite ...
s". In 2018, observations revealed that Phaethon was blue in color. This is extremely rare, as most asteroids tend to be grey or red. In 2020,
polarimetric Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or hav ...
study revealed Phaethon has a surface with steep slopes covered by a mix of
regolith Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...
with larger pebbles. Phaethon's composition fits the notion of its cometary origin; it is classified as a
F-type asteroid F-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-type asteroid#C-group asteroids, C-group. Characteristics F-type asteroids have spectra generally similar to those of the B-type asteroid, B-type ...
because it is composed of dark material or a B-type asteroid because of its blue color. In 2022 it was shown how Phaethon's blue color and its rock-comet-like emission activity can be explained by the effects of the intense solar heating at perihelion causing sublimation of any darkish-red refractory organic, nano-phase iron (nFe0), and pyroxene materials on its surface. Analysis of a mid-infrared spectral emissivity spectrum from the
Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...
showed Phaethon to be linked to the rare Yamato-type (CY)
carbonaceous chondrites Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 8 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites. The C chondrites represent only a small propor ...
. This link appears speculative and partial. Further analysis of this spectrum confirmed the presence of Mg-rich
olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...
,
carbonates A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group . ...
, and Fe-
sulfides Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families of ...
. These minerals decompose at the temperatures that Phaethon reaches at perihelion, resulting in outgassing, in a process called
thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition of a substance caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic ...
. It is believed that this process leads to dust ejection and can explain the formation of the Geminid meteor stream.


Meteor shower

Shortly after its discovery,
Fred Whipple Fred Lawrence Whipple (November 5, 1906 – August 30, 2004) was an American astronomer, who worked at the Harvard College Observatory for more than 70 years. Among his achievements were asteroid and comet discoveries, the " dirty snowball" hy ...
observed that the "orbital elements of 1983 TB shown on IAUC 3879 are virtually coincident with the mean orbital elements of 19 Geminid meteors photographed with the super-Schmidt meteor cameras". In other words, Phaethon is the long-sought parent body of the
Geminids The Geminids are a prolific meteor shower with 3200 Phaethon (which is thought to be an Apollo asteroid with a " rock comet" orbit.) being the parent body. Because of this, it would make this shower, along with the Quadrantids, the only ...
meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at ext ...
of mid-December.


Planned flyby

DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage Phaethon fLyby dUSt science) is a planned mission to fly by 3200 Phaethon, as well as various minor bodies originating from it. The spacecraft is being developed by the Japanese space agency
JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
and will demonstrate advanced technologies for future deep space exploration. DESTINY+ is planned to be launched no earlier than 2028.


Close approaches

Phaethon approached to of Earth on December 10, 2007, and was detected by
radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
at
Arecibo Arecibo (; ) is a Arecibo barrio-pueblo, city and Municipalities of Puerto Rico, municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado, Puerto Rico, Utuado and Ciales, Puerto Rico, Ciale ...
. When Phaethon came to perihelion in July 2009, it was found to be brighter than expected. During its approach, the
STEREO Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
-A spacecraft detected an unexpected brightening, roughly by a factor of two.


2010 approach


2017 approach

On December 16, 2017, at 23:00  UT, Phaethon passed from Earth (27
lunar distance The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. In contrast, the Lunar distance (LD or \Delta_), or Earth–Moon characteristic distance, is a unit of measure ...
s). The Earth approach distance was known with a 3-sigma precision of ±700 m. This was the best opportunity to date for radar observations by Goldstone and
Arecibo Arecibo (; ) is a Arecibo barrio-pueblo, city and Municipalities of Puerto Rico, municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado, Puerto Rico, Utuado and Ciales, Puerto Rico, Ciale ...
, with a resolution of . The asteroid was bright enough to see in small telescopes, peaking at magnitude 10.8 between December 13–15 while dimming slightly to magnitude 11 on December 16 at closest approach. Arecibo made observations of Phaethon from December 15–19. It will not make an Earth approach closer than the 2017 passage until December 14, 2093, when it will pass from Earth.


Notes


References


External links


(3200) Phaethon
by the Associazione Friulana di Astronomia e Meteorologia
"The 2004 Geminid Meteor Shower"
by Science@NASA
"ScienceCasts: Rock Comet Meteor Shower"
by Science@NASA on YouTube.com
Phaethon orbit and observations
at
IAU The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
Minor Planet Center * * * {{DEFAULTSORT:Phaethon 003200 003200 003200 Named minor planets 003200 003200 003200 Mercury-crossing asteroids Venus-crossing asteroids Earth-crossing asteroids 003200 003200 # 003200 003200 003200 19831011