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Eta Corvi (Eta Crv, η Corvi, η Crv) is an
F-type F-type may refer to: *F-type asteroid, a type of carbonaceous asteroid *F-ATPase, a membrane protein *F-type main-sequence star, a hydrogen-fusing star * F-type Prisons, high-security prisons in Turkey *MG F-type Magna, six-cylinder-engined car pr ...
main-sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of star ...
star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
, the sixth-brightest star in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
of
Corvus ''Corvus'' is a widely distributed genus of passerine birds ranging from medium-sized to large-sized in the family Corvidae. It includes species commonly known as crows, ravens, and rooks. The species commonly encountered in Europe are the car ...
. Two debris disks have been detected orbiting this star, one at ~150 AU, and a warmer one within a few astronomical units (AU).


Properties

Eta Corvi is only about 30% of the Sun's age. The concentration of
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and other heavy elements in its atmosphere is only about 93% that of the Sun's. The
projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bu ...
at the star's equator (''v'' sin ''i'') is 68 km/s - more than 30 times faster than that for the Sun. A yellow-white main sequence star of spectral type F2V, it has an estimated surface temperature of 6950 K. It is 1.52 times as massive as the Sun and is 4.87 times as luminous. It is 59 light-years distant from the Solar System. The
IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...
satellite detected an excess of infrared radiation from this star, beyond what would normally be expected for a stellar object of this class. Observations in the submillimetre band confirmed the presence of excess dust in orbit around the star having about 60% of the mass of the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
and a temperature of 80 K. The data indicated a
debris disk A debris disk (American English), or debris disc ( Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris ...
with an estimated maximum radius of 180 AU from the star, or 180 times the separation of Earth and the Sun. (Compare with the
Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
, which extends out to 55 AU from the Sun.) Recent submillimeter observations confirm the presence of an outer flat, circumstellar disk of debris with an outer radius of 150 AU. It is oriented at an
inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...
to the line of sight from the Earth. Most of the inner 100 AU of the disk is relatively free of material, which suggests it was cleared away by a planetary system. In addition, infrared radiation which appears to be from an inner, hotter, debris disk within 3.5 AU of the star has been observed. Since the
Poynting–Robertson effect The Poynting–Robertson effect, also known as Poynting–Robertson drag, named after John Henry Poynting and Howard P. Robertson, is a process by which solar radiation causes a dust grain orbiting a star to lose angular momentum relative to its or ...
would cause the dust in the outer disk to spiral in to the star within 20 million years, much younger than the age of the system, the observed presence of dust in the outer disk means that it must be constantly replenished. It is thought that this happens by the collisions of
planetesimal Planetesimals () are solid objects thought to exist in protoplanetary disks and debris disks. Believed to have formed in the Solar System about 4.6 billion years ago, they aid study of its formation. Formation A widely accepted theory of pla ...
s orbiting at a distance of about 150 AU, which are repeatedly broken down into smaller and smaller pieces, eventually becoming dust. The origin of the inner disk is not clear. It may have originated from planetesimals recently having moved from the outer regions of the system into the inner system, in a process similar to the
Late Heavy Bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized astronomical event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According ...
in the history of the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
, and subsequently being ground to dust by collisions.


Possible Late Heavy Bombardment

In 2010–2011, Carey Lisse of the
Johns Hopkins University The Johns Hopkins University (often abbreviated as Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland, United States. Founded in 1876 based on the European research institution model, J ...
Applied Physics Laboratory and his group analyzed the Spitzer IRS 5–35 μm spectrum of the warm, ~360 K circumstellar dust and found that it showed clear evidence for warm, water- and carbon-rich dust at ~3 AU from the central star, in the system's
habitable zone In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...
, uncoupled and in a separate reservoir from the system's extended sub-mm dust ring at 150 ± 20 AU. Spectral features similar in kind and amplitude to those found for ultra-primitive (i.e., formed very early in the lifetime of the Eta Corvi system) ~10
Myr Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
old cometary material were found (water ice and gas,
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 ...
s and
pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...
s,
amorphous carbon Amorphous carbon is free, reactive carbon that has no crystalline structure. Amorphous carbon materials may be stabilized by terminating dangling-π bonds with hydrogen. As with other amorphous solids, some short-range order can be observed. Amo ...
and metal
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 ...
), in addition to emissions due to impact produced
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...
and high temperature/pressure
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
aceous phases. The warm dust is very primitive, and definitely not from an asteroidal parent body. A large amount, at least 3 x 1019 kg, of 0.1 – 1000 μm warm dust is present, in a roughly collisional
equilibrium Equilibrium may refer to: Film and television * ''Equilibrium'' (film), a 2002 science fiction film * '' The Story of Three Loves'', also known as ''Equilibrium'', a 1953 romantic anthology film * "Equilibrium" (''seaQuest 2032'') * ''Equilibr ...
distribution with dn/da ~ a−3.5. This is the equivalent of a 160-
kilometer The kilometre ( SI symbol: km; or ), spelt kilometer in American and Philippine English, is a unit of length in the International System of Units (SI), equal to one thousand metres (kilo- being the SI prefix for ). It is the preferred mea ...
-radius
centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...
or medium-sized
Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
object of 1.0 g cm−3 density or 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 ...
" of 260 km radius and 0.40 g cm−3 density. The warm dust mass is much larger than that of a solar system comet (1012 – 1015 kg), but is very similar to the mass of a Kuiper belt object (1019 – 1021 kg). The amount of water tied up in the observed material, ~1019 kg, is > 0.1% of the water in the Earth's oceans, and the amount of carbon is also considerable, ~1018 kg. The team found that the best model for what is going on is that some process (e.g.,
planetary migration Planetary migration occurs when a planet or other body in orbit around a star interacts with a disk of gas or planetesimals, resulting in the alteration of its orbital parameters, especially its semi-major axis. Planetary migration is the most ...
) is dynamically exciting the Eta Corvi-equivalent of the Solar System's
Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
(KB), causing frequent collisions amongst Kuiper belt objects (KBOs) and producing the observed copious Kuiper belt dust. As part of this process, one or more of the excited KBOs was scattered onto an orbit that sent it into the inner system, where it collided with a planetary-class body at ~3 AU, releasing a large amount of thermally unprocessed, primitive ice and carbon-rich dust. Their analysis suggests that the system is likely a good analogue for the
Late Heavy Bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized astronomical event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According ...
(LHB) processes that occurred in the early Solar System at 0.6–0.8 Gyr after the formation of the
calcium–aluminium-rich inclusion A calcium–aluminium-rich inclusion or Ca–Al-rich inclusion (CAI) is a submillimeter- to centimeter-sized light-colored calcium- and aluminium-rich inclusion found in carbonaceous chondrite meteorites. The four CAIs that have been dated using ...
s (
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
s such as
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 ...
s that are among the first
solid Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...
s condensed from the cooling
protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk; while the two are sim ...
) and is thus worthy of further detailed study in order to understand the nature of the LHB. It is also a good system to perform a search for a rocky planetary body at ~3 AU (the impacted planet), and for a giant planet at ~115 AU (the Kuiper belt dynamical stirrer at ~ the 3:2 resonance of the Kuiper belt dust at 150 AU).


Name

In
Chinese astronomy Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The Ancient China, ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categori ...
, Eta Corvi is called 左轄,
Pinyin Hanyu Pinyin, or simply pinyin, officially the Chinese Phonetic Alphabet, is the most common romanization system for Standard Chinese. ''Hanyu'' () literally means 'Han Chinese, Han language'—that is, the Chinese language—while ''pinyin' ...
: Zuǒxiá, meaning ''Left Linchpin'', because this star is marking itself and stands alone in the ''Left Linchpin'' asterism,
Chariot A chariot is a type of vehicle similar to a cart, driven by a charioteer, usually using horses to provide rapid Propulsion, motive power. The oldest known chariots have been found in burials of the Sintashta culture in modern-day Chelyabinsk O ...
mansion (see :
Chinese constellation Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" ( Chinese ''xīng guān''). The Chinese asterisms are generally smaller than the constellations of Hellenisti ...
). 左轄 (Zuǒxiá), westernized into Tso Hea, but the name ''Tso Hea'' was already designated for
β Corvi Beta Corvi or β Corvi, officially named Kraz (), is the second-brightest star in the southern constellation of Corvus with an apparent visual magnitude of 2.647. Based on parallax measurements obtained during the Hipparcos miss ...
(Kraz) by R.H. Allen.


References

{{Stars of Corvus Corvus (constellation) Circumstellar disks F-type main-sequence stars Corvi, 8 Corvi, Eta 109085 061174 0471 4775 Durchmusterung objects TIC objects