HD 113766
Encyclopedia
HD 113766 is a binary star system located 424 ly from Earth
in the direction of the constellation
Centaurus
. The star system is approximately 10 million years old and is slightly more massive than our sun, but what makes HD 113766 special is the presence of a large belt of warm (~440 K
) dust surrounding the star HD 113766 A. The dense dust belt, more than 100 times more massive than our own asteroid belt, is thought to be collapsing to form a rocky planet
, which when it has formed will lie within the star's terrestrial habitable zone
where liquid water can exist on its surface. HD 113766 represents the most well understood system in a growing class of objects that should provide more clues to how rocky planets like the Earth formed.
spectrometer
on board the Spitzer Space Telescope
, and interpreted using the results of the NASA
Deep Impact and STARDUST
missions. Analysis of the atomic and mineral composition, dust temperature, and dust mass show a huge amount of warm material similar to metal rich S-type asteroid
s in a narrow belt at 1.8+/-0.2 AU
from the 4.4 L☉ HD 113766 A. The group found at least a Mars' mass worth of warm dust in particles of size 10 m or less, and very likely as much as a few Earth masses of dust if one adds in the contribution of material in bodies up to 1 km in radius which are currently thought to be the basic building blocks of rocky planet formation. Comparison with current planetary formation theories suggests that the disk is in the early stages of terrestrial (rocky) planet formation. This can be also inferred by the presence of metals in the rocky material making up the disk. If planets had already formed the high density metals should have sunk to their cores during the molten stage of planet formation; a process known as planetary differentiation
.
, and is at the equivalent position of the solar system's asteroid belt, while the second belt is even farther out between 30 and 80 AU
, where the solar system's Kuiper Belt would lie. This material may be the source of future water for the rocky planet at 1.8 AU
if and when it completes its formation.
There may also be gas giant
planets in this system, already formed (in the first 1-5 Myrs) before the current era of rocky planet formation. While none have been detected to date, by analogy with the solar system, their presence is likely, since evidence for analogues of the solar system's asteroid belt, Kuiper belt, and terrestrial planets have been found.
from the A star where the terrestrial planet is forming. Located at more than 4 times the distance of Pluto from our own Sun, HD 113766 B has almost no effect on the material orbiting close to HD 113766 A.
, which has been reported to have a large amount of warm dust mass at the equivalent distance of the solar system's asteroid belt. It is not currently known why both of these star systems should have such configurations; i.e. a protoplanetary disk around part of the system while other stars in the system lack one.
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
in the direction of the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Centaurus
Centaurus
Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
. The star system is approximately 10 million years old and is slightly more massive than our sun, but what makes HD 113766 special is the presence of a large belt of warm (~440 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
) dust surrounding the star HD 113766 A. The dense dust belt, more than 100 times more massive than our own asteroid belt, is thought to be collapsing to form a rocky planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
, which when it has formed will lie within the star's terrestrial habitable zone
Habitable zone
In astronomy and astrobiology, a habitable zone is an umbrella term for regions that are considered favourable to life. The concept is inferred from the empirical study of conditions favourable for Life on Earth...
where liquid water can exist on its surface. HD 113766 represents the most well understood system in a growing class of objects that should provide more clues to how rocky planets like the Earth formed.
Rocky accretion belt
The dusty material in the system was analyzed in 2007 by a group led by Dr. Carey Lisse, of the Johns Hopkins University Applied Physics Laboratory in Laurel, MD, USA. Observations were made using the infraredInfrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
on board the Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
, and interpreted using the results of the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Deep Impact and STARDUST
Stardust (spacecraft)
Stardust is a 300-kilogram robotic space probe launched by NASA on February 7, 1999 to study the asteroid 5535 Annefrank and collect samples from the coma of comet Wild 2. The primary mission was completed January 15, 2006, when the sample return capsule returned to Earth...
missions. Analysis of the atomic and mineral composition, dust temperature, and dust mass show a huge amount of warm material similar to metal rich S-type 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 a narrow belt at 1.8+/-0.2 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from the 4.4 L☉ HD 113766 A. The group found at least a Mars' mass worth of warm dust in particles of size 10 m or less, and very likely as much as a few Earth masses of dust if one adds in the contribution of material in bodies up to 1 km in radius which are currently thought to be the basic building blocks of rocky planet formation. Comparison with current planetary formation theories suggests that the disk is in the early stages of terrestrial (rocky) planet formation. This can be also inferred by the presence of metals in the rocky material making up the disk. If planets had already formed the high density metals should have sunk to their cores during the molten stage of planet formation; a process known as planetary differentiation
Planetary differentiation
In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behaviour, where the body develops into compositionally distinct layers; the denser materials of a planet sink to the center,...
.
Icy accretion belts
While no water gas was found to be associated with the warm dust belt, two concentrations of icy material were found in the system. The first belt lies between 4 and 9 AUAstronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, and is at the equivalent position of the solar system's asteroid belt, while the second belt is even farther out between 30 and 80 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, where the solar system's Kuiper Belt would lie. This material may be the source of future water for the rocky planet at 1.8 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
if and when it completes its formation.
There may also be gas giant
Gas giant
A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...
planets in this system, already formed (in the first 1-5 Myrs) before the current era of rocky planet formation. While none have been detected to date, by analogy with the solar system, their presence is likely, since evidence for analogues of the solar system's asteroid belt, Kuiper belt, and terrestrial planets have been found.
HD 113766 B
The star system was first identified as being potentially interesting by Backman et al. using observations made by the Infrared Astronomical Satellite (IRAS) in 1983. Later measurements in 2001 by a team led by Meyer et al. determined that the system was actually a close binary, with the second star in the system, HD 113766 B, a near twin of HD 113766 A orbiting approximately 170 AUAstronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from the A star where the terrestrial planet is forming. Located at more than 4 times the distance of Pluto from our own Sun, HD 113766 B has almost no effect on the material orbiting close to HD 113766 A.
Similar star systems
Binary star systems are common, found more frequently than single star systems like our own. The arrangement of HD 113766, a binary star system with a protoplanetary disk around one star, is somewhat similar to the one-half of the system HD 98800HD 98800
HD 98800, also catalogued as TV Crateris , is a quadruple star system approximately 150 light-years away in the constellation of Crater . The system is located within the TW Hydrae association...
, which has been reported to have a large amount of warm dust mass at the equivalent distance of the solar system's asteroid belt. It is not currently known why both of these star systems should have such configurations; i.e. a protoplanetary disk around part of the system while other stars in the system lack one.