Zodiacal dust
Encyclopedia
The Zodiacal dust cloud is visible as a diffuse glow, known as the zodiacal light
, that stretches along the zodiac
, and is best seen just after sunset and before sunrise in spring and autumn when the zodiac is at a steep angle to the horizon.
The glow was first correctly identified as being due to scattered sunlight from dust particles in the solar system by Joshua Childrey in 1661. The dust forms a thick pancake-shaped cloud in the Solar System
collectively known as the zodiacal cloud, which occupies the same plane of the ecliptic
. The dust particles are between 10 and 300 micrometre
s in diameter, with most mass around 150 micrometres.
The zodiacal cloud can be observed by the naked eye at certain times of the year and appears as a second "Milky Way" along the ecliptic
. This phenomenon is called the zodiacal light.
s and from collisions between asteroid
s in the asteroid belt
. Peter Jenniskens
had previously recognized that many of our meteor showers have no known active comet parent bodies. In a 2010 article in the Astrophysical Journal, David Nesvorny and Peter Jenniskens attributed over 85 percent of the dust to occasional fragmentations of Jupiter Family Comets that are nearly dormant
. Jupiter Family Comets have orbital periods of less than 20 years and are considered dormant when not actively outgassing, but may do so in the future. Nesvorny and Jenniskens' first fully dynamical model of the zodiacal cloud demonstrated that only if the dust was released in orbits that approach Jupiter, is it stirred up enough to explain the thickness of the zodiacal dust cloud. The dust in meteoroid streams is much larger, 300 to 10,000 micrometre
s in diameter, and falls apart in smaller zodiacal dust grains over time.
Small particles of dust that orbit the Sun are steadily forced into more circular (but still elongated) orbits by the Poynting-Robertson effect
. According to Nesvorny and Jenniskens, when the dust grains are as small as about 150 micrometres in size, they will hit the Earth at an average speed of 14.5 km/s, many as slowly as 12 km/s. If so, they pointed out, this comet dust
can survive entry in partially molten form, accounting for the unusual attributes of the micrometeorites collected in Antarctica, which do not resemble the larger meteorites known to originate from asteroids.
Particles can be reduced in size by collisions or by space weathering. When ground down to sizes less than 10 micrometres, the grains are removed from the inner solar system by solar radiation pressure. The dust is then replenished by the infall from comets.
Zodiacal dust around nearby stars is called exozodiacal dust
; it is a potentially important source of noise for directly imaging extrasolar planets. Nesvorny and Je nniskens have pointed out that this exozodiacal dust, or hot debris disks, can also help find planets, as planets tend to scatter the comets to the inner solar system.
, lead guitarist with the band Queen
, handed in his PhD thesis Radial Velocities in the Zodiacal Dust Cloud 36 years after starting it and then abandoning it in favour of a musical career. That he was able to submit it was possible only because of the minimal amount of research on the topic that had been carried out in the intervening years. May describes the subject as being one that became "trendy" again in the 2000s.
Zodiacal light
Zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. Caused by sunlight scattered by space dust in the zodiacal cloud, it is so faint that either moonlight or light pollution renders...
, that stretches along the zodiac
Zodiac
In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...
, and is best seen just after sunset and before sunrise in spring and autumn when the zodiac is at a steep angle to the horizon.
The glow was first correctly identified as being due to scattered sunlight from dust particles in the solar system by Joshua Childrey in 1661. The dust forms a thick pancake-shaped cloud in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
collectively known as the zodiacal cloud, which occupies the same plane of the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
. The dust particles are between 10 and 300 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s in diameter, with most mass around 150 micrometres.
The zodiacal cloud can be observed by the naked eye at certain times of the year and appears as a second "Milky Way" along the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
. This phenomenon is called the zodiacal light.
Origin
The source of that dust was long debated. Until recently, it was thought that the dust originated from the tails of active cometComet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s and from collisions between asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
s in the asteroid belt
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
. Peter Jenniskens
Peter Jenniskens
Petrus Matheus Marie Jenniskens is a Dutch astronomer and a senior research scientist at the Carl Sagan Center of the SETI Institute and at NASA Ames Research Center. He is an expert on meteor showers. Jenniskens is the author of the 790 page book "Meteor Showers and their Parent Comets"...
had previously recognized that many of our meteor showers have no known active comet parent bodies. In a 2010 article in the Astrophysical Journal, David Nesvorny and Peter Jenniskens attributed over 85 percent of the dust to occasional fragmentations of Jupiter Family Comets that are nearly dormant
Extinct comet
Extinct comets are comets that have expelled most of their volatile ice and have little left to form a tail or coma. The volatile material contained in the comet nucleus evaporates away, and all that remains is inert rock or rubble that can resemble an asteroid. Comets may go through a transition...
. Jupiter Family Comets have orbital periods of less than 20 years and are considered dormant when not actively outgassing, but may do so in the future. Nesvorny and Jenniskens' first fully dynamical model of the zodiacal cloud demonstrated that only if the dust was released in orbits that approach Jupiter, is it stirred up enough to explain the thickness of the zodiacal dust cloud. The dust in meteoroid streams is much larger, 300 to 10,000 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s in diameter, and falls apart in smaller zodiacal dust grains over time.
Small particles of dust that orbit the Sun are steadily forced into more circular (but still elongated) orbits by the Poynting-Robertson effect
Poynting-Robertson effect
The Poynting–Robertson effect, also known as Poynting–Robertson drag, named after John Henry Poynting and Howard Percy Robertson, is a process by which solar radiation causes a dust grain in the Solar System to slowly spiral into the sun...
. According to Nesvorny and Jenniskens, when the dust grains are as small as about 150 micrometres in size, they will hit the Earth at an average speed of 14.5 km/s, many as slowly as 12 km/s. If so, they pointed out, this comet dust
Comet dust
Comet dust refers to cosmic dust that originates from a comet. Comet dust can provide clues to comets' origin.-Dust and comet origin:The models for the origin of comets are: 1) the interstellar model, 2) the solar system model, 3) primordial rubble piles 4) aggregation of planetesimals in the dust...
can survive entry in partially molten form, accounting for the unusual attributes of the micrometeorites collected in Antarctica, which do not resemble the larger meteorites known to originate from asteroids.
Particles can be reduced in size by collisions or by space weathering. When ground down to sizes less than 10 micrometres, the grains are removed from the inner solar system by solar radiation pressure. The dust is then replenished by the infall from comets.
Zodiacal dust around nearby stars is called exozodiacal dust
Exozodiacal dust
Exozodiacal dust is the exoplanetary analog of zodiacal dust, the 1-100 micrometre-sized grains of silicate dust that fill the plane of the solar system, especially interior to the asteroid belt. As for the zodiacal dust, these grains are probably produced by outgasing comets as well as by...
; it is a potentially important source of noise for directly imaging extrasolar planets. Nesvorny and Je nniskens have pointed out that this exozodiacal dust, or hot debris disks, can also help find planets, as planets tend to scatter the comets to the inner solar system.
Brian May
In August 2007, Brian MayBrian May
Brian Harold May, CBE is an English musician and astrophysicist most widely known as the guitarist and a songwriter of the rock band Queen...
, lead guitarist with the band Queen
Queen (band)
Queen are a British rock band formed in London in 1971, originally consisting of Freddie Mercury , Brian May , John Deacon , and Roger Taylor...
, handed in his PhD thesis Radial Velocities in the Zodiacal Dust Cloud 36 years after starting it and then abandoning it in favour of a musical career. That he was able to submit it was possible only because of the minimal amount of research on the topic that had been carried out in the intervening years. May describes the subject as being one that became "trendy" again in the 2000s.