V838 Monocerotis
Encyclopedia
V838 Monocerotis (V838 Mon) is a red variable
star
in the constellation
Monoceros
about 20,000 light years (6 kpc
) from the Sun
, and possibly one of the largest known stars. The previously unknown star was observed in early 2002 experiencing a major outburst. Originally believed to be a typical nova
eruption, it was then realized to be something completely different. The reason for the outburst is still uncertain, but several conjectures have been put forward, including an eruption related to stellar death processes and a merger of a binary star or planets.
, the Unicorn. Being a new variable star, it was designated V838 Monocerotis, the 838th variable star of Monoceros. The initial light curve
resembled that of a nova
, an eruption that occurs when enough hydrogen
gas has accumulated on the surface of a white dwarf
from its close binary
companion. Therefore it was also designated Nova Monocerotis 2002. V838 Monocerotis reached maximum visual magnitude of 6.75 on February 6, 2002, after which it started to dim rapidly, as expected. However, in early March the star started to brighten again, this time mostly in infrared
wavelengths. Yet another brightening in infrared occurred in early April, after which the star returned to near its original brightness before the eruption, magnitude 15.6. The lightcurve produced by the eruption is unlike anything previously seen.
The star brightened to about a million times solar luminosity
ensuring that at the time of maximum V838 Monocerotis was one of the most luminous stars in the Milky Way
galaxy. The brightening was caused by a rapid expansion of the outer layers of the star. The star was observed using the Palomar Testbed Interferometer
which provided a radius of 1,570 ± 400 solar
radii (comparable to Jupiter
's orbital radius), confirming the earlier indirect calculations. The expansion took only a couple of months, meaning that its speed was abnormal. The laws of thermodynamics
dictate that expanding gas cools. Therefore the star became extremely cool and deep red. In fact, some astronomer
s argue that the spectra
of the star resembled that of L-type brown dwarf
s. If that is the case, V838 Monocerotis would be the first known L-type supergiant
.
. The star, designated M31-RV, reached the absolute bolometric magnitude
of −9.95 at maximum (corresponding a luminosity of 0.75 million times solar) before dimming beyond detectability. A similar eruption occurred in 1994 in the Milky Way (V4332 Sagittarii).
the eruption generated, the distance of the star was first estimated to be 1,900 to 2,900 light years. Combined with the apparent magnitude measured from pre-eruption photographs, it was thought to be an underluminous F-type dwarf not much unlike our Sun which posed a considerable enigma.
More accurate measurements gave a much larger distance, 20,000 light years (6 kpc). It appears that the star is considerably more massive and luminous than the Sun. The mass of the star is probably from 5 to 10 times solar, and luminosity from 550 to 5,000 times solar. The original radius may have been about 5 times solar and temperature 4,700–30,000 K
. Needless to say, these values are very approximate. Munari et al. (2005) suggest that the progenitor star is in fact a very massive supergiant with a mass of about 65 times solar. They also conclude that the system may be only about 4 million years old.
The spectrum of V838 Monocerotis reveals a companion, a hot blue B-type main sequence
star probably not much different from the erupted star. It is also possible that the erupted star was slightly less massive than the companion and only just entering the main sequence.
Based on the photometric parallax
of the companion, Munari et al. get a greater distance, 36,000 light years (10 kpc).
Rapidly brightening objects like novae and supernova
e are known to produce a phenomenon known as light echo
. The light that travels directly from the object arrives first. If there are clouds of interstellar matter
around the star, some light is reflected from the clouds. Because of the longer path, the reflected light arrives later producing a vision of expanding rings of light around the erupted object. In addition, the rings appear to travel faster than the speed of light
.
In the case of V838 Monocerotis, the light echo produced was unprecedented and is well documented in images taken by the Hubble Space Telescope
. While the photos appear to depict an expanding spherical shell of debris, they are actually formed by the illumination of an ever-expanding ellipsoid with the progenitor star at one focus and the observer at the other. Hence, despite appearances, the structures in these photos are actually concave toward the viewer.
It is not yet clear if the surrounding nebulosity is associated with the star itself. If that is the case, they may have been produced by the star in earlier eruptions which would rule out several models that are based on single catastrophic events. However, there is strong evidence that the V838 Monocerotis system is very young and still embedded in the nebula
from which it formed.
Interestingly, the first eruption occurred at shorter wavelengths (i.e. was bluer) and can be seen in the light echo: the outer border of the echo is bluish in the Hubble images.
star, on the verge of its death. The nebulosity illuminated by the light echo may actually be shells of dust surrounding the star, created by the star during previous similar outbursts. The brightening may have been a so-called helium flash
, where the core of a dying low-mass star suddenly ignites carbon
fusion
disrupting, but not destroying, the star. Such an event is known to have occurred in Sakurai's Object
. However, several pieces of evidence supports the argument that the dust is interstellar rather than centered around V838 Monoceros. A dying star that has lost its outer envelopes would be appropriately hot, but the evidence points to a young star instead.
. If that is the case, the outburst may have been a so-called helium flash
, a thermonuclear event where a shell in the star containing helium
suddenly ignites and starts to fuse carbon. Very massive stars survive multiple such events, however they experience heavy mass loss (about half of the original mass is lost while in the main sequence
) before settling as extremely hot Wolf-Rayet star
s. This theory may also explain the apparent dust shells around the star. V838 Monoceros is located in the approximate direction of the Galactic anticenter
and off from the disk of the Milky Way. Stellar birth is less active in outer galactic regions, and it is not clear how such a massive star can form there. However, there are very young clusters like Ruprecht 44 and the 4 million years old NGC 1893
at a distance of ca. 7 kpc and 6 kpc, respectively.
s have shown the merger model to be plausible. The simulations also show that the inflated envelope would have come almost entirely from the smaller component. In addition, the merger model explains the multiple peaks in the light curve observed during the outburst.
s. If one of the planets entered into the atmosphere of the star, the stellar atmosphere would have begun slowing down the planet. As the planet penetrated deeper into the atmosphere, friction would become stronger and kinetic energy would be released into the star more rapidly. The star's envelope would then warm up enough to trigger deuterium
fusion, which would lead to rapid expansion. The later peaks may then have occurred when two other planets entered into the expanded envelope. The authors of this model calculate that every year about 0.4 planetary capture events occur in Sun-like stars in the Milky Way galaxy, whereas for massive stars like V838 Monocerotis the rate is approximately 0.5–2.5 events per year.
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
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...
in 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....
Monoceros
Monoceros
Monoceros is a faint constellation on the celestial equator. Its name is Greek for unicorn. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the south and Hydra to the east...
about 20,000 light years (6 kpc
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 the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, and possibly one of the largest known stars. The previously unknown star was observed in early 2002 experiencing a major outburst. Originally believed to be a typical nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
eruption, it was then realized to be something completely different. The reason for the outburst is still uncertain, but several conjectures have been put forward, including an eruption related to stellar death processes and a merger of a binary star or planets.
Outburst
On January 6, 2002, an unknown star was seen to brighten up in MonocerosMonoceros
Monoceros is a faint constellation on the celestial equator. Its name is Greek for unicorn. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the south and Hydra to the east...
, the Unicorn. Being a new variable star, it was designated V838 Monocerotis, the 838th variable star of Monoceros. The initial light curve
Light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...
resembled that of a nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
, an eruption that occurs when enough 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...
gas has accumulated on the surface of a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
from its close binary
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
companion. Therefore it was also designated Nova Monocerotis 2002. V838 Monocerotis reached maximum visual magnitude of 6.75 on February 6, 2002, after which it started to dim rapidly, as expected. However, in early March the star started to brighten again, this time mostly in infrared
Infrared
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...
wavelengths. Yet another brightening in infrared occurred in early April, after which the star returned to near its original brightness before the eruption, magnitude 15.6. The lightcurve produced by the eruption is unlike anything previously seen.
The star brightened to about a million times solar luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
ensuring that at the time of maximum V838 Monocerotis was one of the most luminous stars in the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy. The brightening was caused by a rapid expansion of the outer layers of the star. The star was observed using the Palomar Testbed Interferometer
Palomar Testbed Interferometer
The Palomar Testbed Interferometer was a near-IR, long-baseline stellar interferometer located at Palomar Observatory in north San Diego County. It was built by Caltech/JPL and was intended to serve as a testbed for developing interferometric techniques to be used at the Keck Interferometer...
which provided a radius of 1,570 ± 400 solar
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
radii (comparable to Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
's orbital radius), confirming the earlier indirect calculations. The expansion took only a couple of months, meaning that its speed was abnormal. The laws of thermodynamics
Thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
dictate that expanding gas cools. Therefore the star became extremely cool and deep red. In fact, some astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
s argue that the spectra
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
of the star resembled that of L-type brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
s. If that is the case, V838 Monocerotis would be the first known L-type supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
.
Other possibly similar events
There are a handful of outbursts that resemble the one which occurred on V838 Monocerotis. In 1988 a red star was detected erupting in the Andromeda GalaxyAndromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
. The star, designated M31-RV, reached the absolute bolometric magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...
of −9.95 at maximum (corresponding a luminosity of 0.75 million times solar) before dimming beyond detectability. A similar eruption occurred in 1994 in the Milky Way (V4332 Sagittarii).
Progenitor star
Some details are emerging on the nature of the star that experienced the outburst. Based on an incorrect interpretation of the light echoLight echo
thumb|right|250px|Reflected light following path B arrives shortly after the direct flash following path A but before light following path C. B and C have the same apparent distance from the star as seen from [[Earth]]....
the eruption generated, the distance of the star was first estimated to be 1,900 to 2,900 light years. Combined with the apparent magnitude measured from pre-eruption photographs, it was thought to be an underluminous F-type dwarf not much unlike our Sun which posed a considerable enigma.
More accurate measurements gave a much larger distance, 20,000 light years (6 kpc). It appears that the star is considerably more massive and luminous than the Sun. The mass of the star is probably from 5 to 10 times solar, and luminosity from 550 to 5,000 times solar. The original radius may have been about 5 times solar and temperature 4,700–30,000 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...
. Needless to say, these values are very approximate. Munari et al. (2005) suggest that the progenitor star is in fact a very massive supergiant with a mass of about 65 times solar. They also conclude that the system may be only about 4 million years old.
The spectrum of V838 Monocerotis reveals a companion, a hot blue B-type main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
star probably not much different from the erupted star. It is also possible that the erupted star was slightly less massive than the companion and only just entering the main sequence.
Based on the photometric parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
of the companion, Munari et al. get a greater distance, 36,000 light years (10 kpc).
Light echo
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...
e are known to produce a phenomenon known as light echo
Light echo
thumb|right|250px|Reflected light following path B arrives shortly after the direct flash following path A but before light following path C. B and C have the same apparent distance from the star as seen from [[Earth]]....
. The light that travels directly from the object arrives first. If there are clouds of interstellar matter
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
around the star, some light is reflected from the clouds. Because of the longer path, the reflected light arrives later producing a vision of expanding rings of light around the erupted object. In addition, the rings appear to travel faster than the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
.
In the case of V838 Monocerotis, the light echo produced was unprecedented and is well documented in images taken by the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
. While the photos appear to depict an expanding spherical shell of debris, they are actually formed by the illumination of an ever-expanding ellipsoid with the progenitor star at one focus and the observer at the other. Hence, despite appearances, the structures in these photos are actually concave toward the viewer.
It is not yet clear if the surrounding nebulosity is associated with the star itself. If that is the case, they may have been produced by the star in earlier eruptions which would rule out several models that are based on single catastrophic events. However, there is strong evidence that the V838 Monocerotis system is very young and still embedded in the nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
from which it formed.
Interestingly, the first eruption occurred at shorter wavelengths (i.e. was bluer) and can be seen in the light echo: the outer border of the echo is bluish in the Hubble images.
Models
So far several rather different explanations for the eruption of V838 Monocerotis have been published.Atypical nova outburst
The outburst of V838 Monocerotis may be a nova eruption after all, albeit a very unusual one. However, this is very unlikely considering that the system includes a B-type star, and stars of this type are young and massive. There has not been enough time for a possible white dwarf to cool and accrete enough material to cause the eruption.Thermal pulse of a dying star
V838 Monocerotis may be a post-asymptotic giant branchAsymptotic Giant Branch
The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars late in their lives....
star, on the verge of its death. The nebulosity illuminated by the light echo may actually be shells of dust surrounding the star, created by the star during previous similar outbursts. The brightening may have been a so-called helium flash
Helium flash
A helium flash is the runaway fusion of helium in the core of low mass stars of less than about 2.25 solar masses and greater than about 0.5 solar mass, or on the surface of an accreting white dwarf star. They may also occur in the outer layers of larger stars in shell flashes...
, where the core of a dying low-mass star suddenly ignites carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
disrupting, but not destroying, the star. Such an event is known to have occurred in Sakurai's Object
Sakurai's Object
Sakurai's Object in the constellation of Sagittarius, an object discovered to behave as a "slow nova" by Yukio Sakurai, a Japanese amateur astronomer, in 1996...
. However, several pieces of evidence supports the argument that the dust is interstellar rather than centered around V838 Monoceros. A dying star that has lost its outer envelopes would be appropriately hot, but the evidence points to a young star instead.
Thermonuclear event within a massive supergiant
According to some evidence, V838 Monocerotis may be a very massive supergiantSupergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
. If that is the case, the outburst may have been a so-called helium flash
Helium flash
A helium flash is the runaway fusion of helium in the core of low mass stars of less than about 2.25 solar masses and greater than about 0.5 solar mass, or on the surface of an accreting white dwarf star. They may also occur in the outer layers of larger stars in shell flashes...
, a thermonuclear event where a shell in the star containing helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
suddenly ignites and starts to fuse carbon. Very massive stars survive multiple such events, however they experience heavy mass loss (about half of the original mass is lost while in the main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
) before settling as extremely hot Wolf-Rayet star
Wolf-Rayet star
Wolf–Rayet stars are evolved, massive stars , which are losing mass rapidly by means of a very strong stellar wind, with speeds up to 2000 km/s...
s. This theory may also explain the apparent dust shells around the star. V838 Monoceros is located in the approximate direction of the Galactic anticenter
Galactic 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...
and off from the disk of the Milky Way. Stellar birth is less active in outer galactic regions, and it is not clear how such a massive star can form there. However, there are very young clusters like Ruprecht 44 and the 4 million years old NGC 1893
NGC 1893
NGC 1893 is an open cluster in the constellation Auriga.-References:* *...
at a distance of ca. 7 kpc and 6 kpc, respectively.
Mergeburst
The outburst may have been the result of a so-called mergeburst, the merger of two main sequence stars (or an 8 M☉ main sequence star and a 0.3 M☉ pre-main sequence star). This model is strengthened by the apparent youth of the system and the fact that multiple stellar systems may be unstable. The less massive component may have been in a very eccentric orbit or deflected towards the massive one. Computer simulationComputer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
s have shown the merger model to be plausible. The simulations also show that the inflated envelope would have come almost entirely from the smaller component. In addition, the merger model explains the multiple peaks in the light curve observed during the outburst.
Planetary capture event
Another possibility is that V838 Monocerotis may have swallowed its giant planetPlanet
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,...
s. If one of the planets entered into the atmosphere of the star, the stellar atmosphere would have begun slowing down the planet. As the planet penetrated deeper into the atmosphere, friction would become stronger and kinetic energy would be released into the star more rapidly. The star's envelope would then warm up enough to trigger deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
fusion, which would lead to rapid expansion. The later peaks may then have occurred when two other planets entered into the expanded envelope. The authors of this model calculate that every year about 0.4 planetary capture events occur in Sun-like stars in the Milky Way galaxy, whereas for massive stars like V838 Monocerotis the rate is approximately 0.5–2.5 events per year.
External links
- AAVSO Variable Star of the Month. December, 2002: V838 Mon
- Show 12: A Flash of Brilliance Dr. Frank Summers tells about the Mysterious Erupting Star
- Hubble Watches Light from Mysterious Erupting Star Reverberate Through Space — STScI press release STScI-2003-10 (March 26, 2003; received on 10 August 2006)
- Light Continues to Echo Three Years After Stellar Outburst — STScI press release STScI-2005-02 (February 3, 2005; received on 10 August 2006)
- The Hubble Heritage Project — more information and images (received on 10 August 2006)
- Hubble's Latest Views of Light Echo from Star V838 Monocerotis — STScI press release STScI-2006-50 (Exposure dates: November 17, 2005 and September 9, 2006. Released October 26, 2006.)
- V838 at ESA/Hubble
- Slacker Astronomy video podcast and animation of V838 Mon
- NASA Astronomy Picture of the Day for 2002-10-03. Photos taken by Lisa Crause using the 1 meter telescope at the South African Astronomical ObservatorySouth African Astronomical ObservatorySouth African Astronomical Observatory is the national center for optical and infrared astronomy in South Africa. It was established in 1972. The observatory is run by the National Research Foundation of South Africa. The facility's function is to conduct research in astronomy and astrophysics...