IC 443
Encyclopedia
IC 443 is a Galactic supernova remnant
(SNR) in the constellation Gemini
. On the plan of the sky, it is located near the star Eta Geminorum
.
Its distance is roughly 5,000 light years from Earth.
IC 443 may be the remains of a supernova
that occurred 3,000 - 30,000 years ago. The same supernova event likely created the neutron star
CXOU J061705.3+222127
, the collapsed remnant of the stellar core. IC 443 is one of the best-studied cases of supernova remnants interacting with surrounding molecular clouds.
(by comparison, the full moon is 30 arcmin across). At the estimated distance of 5,000 ly (1,500 parsec
) from Earth, it corresponds to a physical size of roughly 70 light years (20 parsec).
The SNR optical and radio morphology is shell-like (e.g. a prototypical shell-like SNR is SN 1006
), consisting of two connected sub-shells with different centers and radii. A third larger sub-shell, initially attributed to IC 443, is now recognized as a different and older (100,000 years) SNR, called G189.6+3.3.
Notably, IC 443 X-ray morphology is centrally peaked and a very soft X-ray shell is barely visible.
Unlike plerion remnants, e.g. the Crab Nebula
, the inner X-ray emission is not dominated by the central pulsar wind nebula
.
It has indeed a thermal origin. IC 443 shows very similar features to the class of mixed morphology SNRs. Both optical and X-ray emission are heavily absorbed by a giant molecular cloud in the foreground, crossing the whole remnant body from northwest to southeast.
The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000 years ago. Recent Chandra
and XMM-Newton
observations
identified a plerion nebula
, close to the remnant southern rim. The point source near the apex of the nebula is a neutron star
, relic of a SN explosion. The location in a star forming region and the presence of a neutron star
favor a Type II supernova
, the ultimate fate of a massive star, as the progenitor explosion.
direction (l=189.1°), close to the Galactic plane (b=+3.0°). Many objects lie in the same region of sky: the HII region S249, several young stars (members of the GEM OB1 association), and an older SNR (G189.6+3.3).
The remnant is evolving in a rich and complex environment, which strongly affects its morphology.
Multi-wavelength observations show the presence of sharp density gradients and different cloud geometries in the surroundings of IC 443. Massive star
s are known to be short lived (roughly 30 million years), ending their life when they are still embedded within the progenitor cloud.
The more massive stars (O-type) probably clear the circum-stellar environment by powerful stellar winds or photoionizing radiation
. Early B-type stars, with a typical mass between 8 and 12 solar masses, are not capable of this, and they likely interact with the primordial molecular cloud when they explode. Thus, it is not surprising that the SNR IC 443, which is thought to be the aftermath of a stellar explosion, evolved in such a complex environment. For instance, an appreciable fraction of supernova remnant
s lies close to dense molecular clouds (~50 out of 265 in the Green catalogue),
and most of them (~60%) show clear signs of interaction with the adjacent cloud.
X-ray and the optical images are characterized by a dark lane, crossing IC 443 from northwest to southeast. Emission from quiescent molecular gas has been observed toward the same direction,
and it is likely due to a giant molecular cloud, located between the remnant and the observer.
This is the main source of extinction of the low energy SNR emission.
In the southeast the blast wave
is interacting with a very dense (~10,000 cm−3) and clumpy molecular cloud, such that the emitting shocked gas has a ring-like shape. The blast wave
has been strongly decelerated by the cloud and is moving with an estimated velocity of roughly 30–40 km s−1.
OH (1720 MHz) maser
emission, which is a robust tracer of interaction between SNRs and dense molecular clouds, has been detected in this region.
Interestingly, a source of gamma-ray radiation is spatially coincident with IC 443 and the maser
emission region, though is not well understood whether it is physically associated with the remnant or not.
In the northeast, where the brightest optical filaments are located, the SNR is interacting with
a very different environment. The forward shock
has encountered a wall of neutral hydrogen
(HI), and is propagating into a less dense medium (~10-1,000 cm−3) with a much higher velocity (80–100 km s−1) than in the southern ridge.
In the western region, the shock wave
breaks out into a more homogeneous and rarefied medium.
Supernova remnant
A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.There are two...
(SNR) in the constellation Gemini
Gemini (constellation)
Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century astronomer Ptolemy and it remains one of the 88 modern constellations today. Its name is Latin for "twins", and it is associated with the twins Castor and Pollux in Greek mythology...
. On the plan of the sky, it is located near the star Eta Geminorum
Eta Geminorum
Eta Geminorum is a triple star system in the constellation Gemini. It has the traditional names Tejat Prior, Propus and Praepes and Pish Pai ....
.
Its distance is roughly 5,000 light years from Earth.
IC 443 may be the remains of a supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
that occurred 3,000 - 30,000 years ago. The same supernova event likely created the neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
CXOU J061705.3+222127
CXOU J061705.3+222127
CXOU J061705.3+222127 is a neutron star. It was likely formed 30,000 years ago in the supernova that created the supernova remnant IC 443. It is travelling at approximately 800,000 km/h away from the site.-External links:...
, the collapsed remnant of the stellar core. IC 443 is one of the best-studied cases of supernova remnants interacting with surrounding molecular clouds.
Global Properties
IC 443 is an extended source, having an angular diameter of 50 arcminMinute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....
(by comparison, the full moon is 30 arcmin across). At the estimated distance of 5,000 ly (1,500 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
) from Earth, it corresponds to a physical size of roughly 70 light years (20 parsec).
The SNR optical and radio morphology is shell-like (e.g. a prototypical shell-like SNR is SN 1006
SN 1006
SN 1006 was a supernova, widely seen on Earth beginning in the year 1006 AD; Earth was about 7,200 light-years away from the supernova. It was the brightest apparent magnitude stellar event in recorded history reaching an estimated -7.5 visual magnitude...
), consisting of two connected sub-shells with different centers and radii. A third larger sub-shell, initially attributed to IC 443, is now recognized as a different and older (100,000 years) SNR, called G189.6+3.3.
Notably, IC 443 X-ray morphology is centrally peaked and a very soft X-ray shell is barely visible.
Unlike plerion remnants, e.g. the Crab Nebula
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
, the inner X-ray emission is not dominated by the central pulsar wind nebula
Pulsar wind nebula
A pulsar wind nebula is a nebula powered by the pulsar wind of a pulsar. At the early stages of their evolution, pulsar wind nebulae are often found inside the shells of supernova remnants...
.
It has indeed a thermal origin. IC 443 shows very similar features to the class of mixed morphology SNRs. Both optical and X-ray emission are heavily absorbed by a giant molecular cloud in the foreground, crossing the whole remnant body from northwest to southeast.
The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000 years ago. Recent Chandra
Chandra X-ray Observatory
The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit.Chandra...
and XMM-Newton
XMM-Newton
The XMM-Newton is an orbiting X-ray observatory launched by ESA in December 1999 on a Ariane 5 rocket...
observations
identified a plerion nebula
Pulsar wind nebula
A pulsar wind nebula is a nebula powered by the pulsar wind of a pulsar. At the early stages of their evolution, pulsar wind nebulae are often found inside the shells of supernova remnants...
, close to the remnant southern rim. The point source near the apex of the nebula is a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
, relic of a SN explosion. The location in a star forming region and the presence of a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
favor a Type II supernova
Type II supernova
A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 9 times, and no more than 40–50 times the mass of the Sun for this type of explosion. It is distinguished from other types of supernova by the presence of hydrogen in its spectrum...
, the ultimate fate of a massive star, as the progenitor explosion.
The SNR environment
The SNR IC 443 is located in the Galactic anticenterGalactic anticenter
The galactic anticenter is a theoretical point in the sky that lies directly opposite the center of the Milky Way galaxy. Because this point is relative, it will vary depending on the location of the observer; it is not an actual fixed point in space. Most of the time, this term refers to the...
direction (l=189.1°), close to the Galactic plane (b=+3.0°). Many objects lie in the same region of sky: the HII region S249, several young stars (members of the GEM OB1 association), and an older SNR (G189.6+3.3).
The remnant is evolving in a rich and complex environment, which strongly affects its morphology.
Multi-wavelength observations show the presence of sharp density gradients and different cloud geometries in the surroundings of IC 443. Massive star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s are known to be short lived (roughly 30 million years), ending their life when they are still embedded within the progenitor cloud.
The more massive stars (O-type) probably clear the circum-stellar environment by powerful stellar winds or photoionizing radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
. Early B-type stars, with a typical mass between 8 and 12 solar masses, are not capable of this, and they likely interact with the primordial molecular cloud when they explode. Thus, it is not surprising that the SNR IC 443, which is thought to be the aftermath of a stellar explosion, evolved in such a complex environment. For instance, an appreciable fraction of supernova remnant
Supernova remnant
A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.There are two...
s lies close to dense molecular clouds (~50 out of 265 in the Green catalogue),
and most of them (~60%) show clear signs of interaction with the adjacent cloud.
X-ray and the optical images are characterized by a dark lane, crossing IC 443 from northwest to southeast. Emission from quiescent molecular gas has been observed toward the same direction,
and it is likely due to a giant molecular cloud, located between the remnant and the observer.
This is the main source of extinction of the low energy SNR emission.
In the southeast the blast wave
Blast wave
A blast wave in fluid dynamics is the pressure and flow resulting from the deposition of a large amount of energy in a small very localised volume. The flow field can be approximated as a lead shock wave, followed by a 'self-similar' subsonic flow field. In simpler terms, a blast wave is an area of...
is interacting with a very dense (~10,000 cm−3) and clumpy molecular cloud, such that the emitting shocked gas has a ring-like shape. The blast wave
Blast wave
A blast wave in fluid dynamics is the pressure and flow resulting from the deposition of a large amount of energy in a small very localised volume. The flow field can be approximated as a lead shock wave, followed by a 'self-similar' subsonic flow field. In simpler terms, a blast wave is an area of...
has been strongly decelerated by the cloud and is moving with an estimated velocity of roughly 30–40 km s−1.
OH (1720 MHz) maser
Astrophysical maser
An astrophysical maser is a naturally occurring source of stimulated spectral line emission, typically in the microwave portion of the electromagnetic spectrum...
emission, which is a robust tracer of interaction between SNRs and dense molecular clouds, has been detected in this region.
Interestingly, a source of gamma-ray radiation is spatially coincident with IC 443 and the maser
Astrophysical maser
An astrophysical maser is a naturally occurring source of stimulated spectral line emission, typically in the microwave portion of the electromagnetic spectrum...
emission region, though is not well understood whether it is physically associated with the remnant or not.
In the northeast, where the brightest optical filaments are located, the SNR is interacting with
a very different environment. The forward shock
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
has encountered a wall of neutral hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
(HI), and is propagating into a less dense medium (~10-1,000 cm−3) with a much higher velocity (80–100 km s−1) than in the southern ridge.
In the western region, the shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
breaks out into a more homogeneous and rarefied medium.
See also
- CXOU J061705.3+222127CXOU J061705.3+222127CXOU J061705.3+222127 is a neutron star. It was likely formed 30,000 years ago in the supernova that created the supernova remnant IC 443. It is travelling at approximately 800,000 km/h away from the site.-External links:...
, the neutron starNeutron starA neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
embedded within supernova remnant IC 443.
External links
- The Case Of The Neutron Star With A Wayward Wake Chandra X-ray Center (ScienceDaily) June 1, 2006
- Astronomy Picture of the DayAstronomy Picture of the DayAstronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...
- IC 443: Supernova Remnant and Neutron Star 2006 June 2
- The Elusive Jellyfish Nebula 2010 May 15