Analysis by Mr. Alain Ranguis, both of the possibility that Wolf 424 might be IUMMA (the sun of UMMO) and of the other alternative possibilities mentioned by the Ummites in various letters. You can find the original study in French here.

 

On the Frontiers of Wolf 424:
The sun of Ummo?

By

 

 

On 16 April 1996 the Hubble space telescope was able, for the first time, to photograph successfully the binary system Wolf 424. This pair of stars is located in the Northern hemisphere, in the constellation of Virgo, at a distance of approximately 14 light years (A light year (LY) is the distance travelled by light in one year at a speed of approximately 300,000 km/s). The two stars of this system are said to be potential candidates for the title of brown dwarfs. These are newcomers to the astrophysicists' bestiary; we will come back to this later.

 

The mass of a star (or of a brown dwarf) can only be determined if it is a member of a binary system. Only the determination of the relative orbit, from observations with high angular resolution, makes it possible to obtain, thanks to Kepler's third law, the total mass of the system and then the individual masses.

 

The time taken to reach the greatest separation between the two components of binary systems can be measured in minutes, hours, days, years and even hundreds of years. Astrometric measurements from the ground are usually based on many years of observations with photographic plates. Often the two components cannot be resolved and then form an oval on the plates. The optimal method for determining the orbital parameters is the direct image of a binary system with its components separated. This work from the ground is very difficult for close and faint companions.

    

Until now, the estimate of the dynamical masses of the Wolf 424 system derived from the orbital elements obtained from the photographic and micrometric observations of the last 60 years.

 

The Hubble telescope has resolved this binary system into its two components, thus making it possible to determine the distance between the primary and its companion. The novelty is that the image was obtained in the visible spectrum without the use of any filter. This has allowed astronomers to refine the calculation of the orbits and then that of the masses.

 

In 1991, using a very powerful infrared imaging technique, the two components of this system had been separated. The angle of separation found at that time was 0.436 seconds of arc. At the time of the observation by the Hubble telescope, the companion had passed periastron (the point of the orbit at which the distance between the two components is smallest) and the distance was only 0.42 seconds of arc ± 0.03". By way of comparison, this is equivalent to the angle formed by the two headlights of a car observed from a distance of approximately 260 km.

 

The two stars have very similar luminosities. The apparent visual magnitude of the pair is about 12.5. Spectroscopic and photometric measurements of these two objects suggest that they have very similar masses.

 

The photos of the Wolf 424 AB system, obtained with the Faint Object Spectrograph (FOS) of the Hubble telescope, show that the companion does not follow the orbit predicted by Heintz ^B in 1989.

 

The updating of the orbital elements brings the estimate of the total mass of the pair to 0.143 solar masses (M_O) (component masses 0.076 M_O and 0.067 M_O), which is greater than the previous estimate of 0.110 M_O deduced from photographic observations, but smaller than the estimated mass of 0.232 M_O (component masses 0.123 and 0.109 M_O) deduced from infrared and visual speckle observations.

 

The revision of the orbit and of the position of the companion, determined by Hubble's FOS, confirms the possibility that the masses of the components, or at least that of Wolf 424 B, are substellar, in the domain of brown dwarfs.

 

The first theoretical work on the existence of brown dwarfs was carried out in 1963 by Kumar, and then in 1975 by Tarter. It had been realized that very low-mass "stars" did not have central temperatures sufficient to start hydrogen burning. The existence and properties of these new bodies thrill astrophysicists, since they make it possible to solve several important problems in astrophysics, such as:

 

• The identification of invisible matter (or missing mass), both in our Galaxy and in others. In this connection, read Jean-Pierre Petit's excellent book "On a perdu la moitié de l'univers" ("Half of the universe has been lost"), Éditions Albin Michel, 1997, which opens another line of research on this problem.
• The understanding of the formation of stars and of the fragmentation of low-mass protostars.
• The determination of the masses of first-generation stars, called Population I, and mainly of those of low mass.

 

Let us get to know these very particular objects a little better, and first study the genesis of stars.

 

A star is essentially made up of hydrogen (90%) and helium (10%) in a fluid or gaseous state. But before it is worthy of that name it passes through the protostar stage.

 

At this stage, under the action of its own weight, the mass of gas composing it contracts slowly, since the internal gas pressure is insufficient to oppose it. As this process of contraction continues, the temperature at the centre of the star may eventually reach the critical temperature of one million degrees.

 

Beyond this limit the process of nuclear fusion begins. The energy released is colossal and produces a rise in temperature sufficient for the pressure exerted by the gas to oppose its gravitational collapse. The star then reaches equilibrium. It has taken some millions of years for stars such as our Sun, for example, to reach that equilibrium.

 

If, on the other hand, the threshold of the critical temperature is not reached, nuclear reactions only occur locally, and a generalized process does not develop. In this case nothing opposes the continuation of the gravitational contraction of the gas. However, it will stop by itself when the matter has reached a state called "degenerate". A pressure called "quantum" pressure will from then on oppose gravitational contraction.

 

In this new state the "failed" star will behave paradoxically: its contraction is accompanied by a rise in pressure, yet its temperature falls! This is the definition astrophysicists give of a brown dwarf.

 

We can relate the notion of critical temperature to that of critical mass. Thus the critical mass for hydrogen burning is about 0.08 times the mass of the Sun, or 80 times that of Jupiter. This is the maximum mass a brown dwarf can reach.

 

On the other hand, the minimum mass a brown dwarf can reach could a priori be that of Jupiter. However, astrophysicists propose assigning a lower limit of 0.01 M_O, that is, 10 times that of Jupiter.

 

The temperature of the zone of a brown dwarf that emits most of its energy, called the effective temperature, is typically below 2,000 ºC, and it radiates essentially in the infrared.

 

Moreover, it can be shown that brown dwarfs have a practically constant radius, comparable to that of Jupiter, that is, about 71,000 kilometres.

 

The Wolf 424 system has yet another particularity, since it is at the centre of a controversy that has divided the scientific and ufological world for many years.

 

It is closely related to what is called the UMMO affair. Let us briefly recall its content.

 

In Spain, in the mid-1960s, a certain Fernando Sesma Manzano claimed to have been contacted by a race of extraterrestrials originating from a planet, UMMO, orbiting a star they call IUMMA.

 

These contacts are organized through letters received by post or by telephone messages. Thus nearly a thousand pages have been received, in Spain and around the world, by representatives of almost all social classes. They deal with all the subjects that a civilization which has apparently managed to master interstellar travel could have tackled.

 

However, in their prose they often return to this leitmotiv: "Believe us, but not too much!". It is up to us to unravel the part of truth or of lies contained in these writings.

 

In the course of this study we will try to check their assertions in astronomical matters, without presuming a priori whether the origin of these characters is terrestrial or not. For convenience we will go on calling them Ummites.

 

Several of these letters give details of the location, in our terminology, of their sun. In a letter dated 1969, addressed to Antonio Ribera (Spanish ufologist), they state that the star we call Wolf 424 would be the only body referenced in our catalogues that is found in the zone where their sun should be (solid angle: Right ascension => 12h 31mn 14s ± 2mn 11s, Declination => 9º 18' 7" ± 14' 2")

 

But, still according to them, a cloud of dust located at a distance of 3.682 parsecs (12 LY) from our sun would obscure our view in this direction and could lead to an error of location.

 

But, and this is where the boat springs a leak, the possibility that either IUMMA or Wolf 424 is a binary system is not raised at any time.

 

In 1967 the various catalogues of astronomical data available already indicated that Wolf 424, or Gliese 473 in that terminology, was a binary system. The first announcement of this possibility was made by Kuiper on 6 June 1938 (visual observation). The first measurement of the parallax appeared that same year; it was repeated in 1952 and refined in 1958.

 

One has to wait until 1952-53 to find the publication of a second visual observation of the binary system. The first article on Wolf 424 was published in 1941 in a professional astronomy journal. In fact, from the end of 1937 the first photographic and visual studies of the binary system were undertaken in order to determine the orbital parameters and the masses of the components.

 

Even if the "Ummites" had not known of this information, disseminated only in specialized or popular magazines (with the errors we know of), they should have spoken of the particular characteristic of their solar system, had that been the case.

 

This flagrant error has been used by the detractors of the UMMO affair to assert that the whole story was nothing but a vast hoax.

 

Before being so categorical, let us study this "omission" and the contradictions in their writings more deeply

 

I. Comparative study of the physical data of various bodies.

 

First, let us recapitulate the data (Table 1) made available to us by the Ummites and compare them with those known for Wolf 424 and our sun.

 

Table 1: Comparative data for the various bodies. Values deduced by calculation.

 

¹ The values of the stellar radii are deduced from knowledge of the absolute magnitude M of the star and its surface temperature T through the following law:

 

 

 

Let us study the agreements and differences between each of these data:

 

I. 1. Important difference between the apparent and absolute visual magnitudes of Iumma and Wolf 424 A.

 

The origin of magnitudes goes back to antiquity. To distinguish stars by their apparent brightness, Hipparchus, as early as the 2nd century B.C., had divided them into six magnitudes. The brightest were considered stars of the first magnitude and the faintest visible to the naked eye of the sixth magnitude. This classification is purely biological, because it rests on a visual impression, the brightness of a star. Astronomy has refined and extended this classification, while keeping Hipparchus's bases.

 

According to this principle, magnitudes have been defined on a logarithmic scale:

 

m = -2.5 log (Brightness) + constant Pogson's law

 

Because of this, the brighter a star is, the lower its magnitude. Thus a first-magnitude star is 2.5 times brighter than a second-magnitude star.

 

So far we have mentioned only the apparent magnitude, denoted m, which is a function of the real brightness and of the distance.

 

To be able to compare the data for a group of stars, they are all placed at the same conventional distance of 10 parsecs (1 parsec is the distance at which we would see the mean radius of the Earth's orbit under an angle of 1 second of arc). We call absolute magnitude, designated by M, the magnitude the stars would have at that distance. The following relation between absolute magnitudes M and apparent magnitudes m makes it possible to calculate the distance D to the star in parsecs:

 

M - m = 5 -5 log D

 

After this explanatory approach to the various definitions of magnitude, let us see what the Ummites say in this respect.

 

From the beginning they stated that, in the direction of IUMMA, there was a cloud of dust at a distance of approximately 12 LY. This would explain, according to them, the notable differences revealed between the luminosities of IUMMA and Wolf 424 A.

 

Indeed, the absorption exerted by a mass of interstellar dust inevitably reduces the brightness of the stars located within or behind it. But we have shown that magnitude is obtained directly from the value of the brightness, or luminosity, of the star. Therefore, if this brightness is underestimated, the magnitude will inevitably be too. On average this absorption amounts to one point of magnitude for a star located at 1000 parsecs, but there may be large deviations from this average value, depending on the density of the cloud.

 

Moreover, dark matter essentially absorbs short-wavelength radiation. This implies a reddening of the light of the stars located behind an absorbing cloud (dust cloud), which is in general proportional to the total absorption caused by that cloud.

 

To crown it all, light that has passed through such a cloud will be polarized, that is, the electromagnetic oscillations that make up the light predominate in a given direction, whereas they are identical in all directions for unpolarized light.

 

Besides the attenuation and polarization of light, dark matter also shows itself through absorption lines in the spectrum of the stars located behind the clouds: lines of neutral sodium and singly ionized calcium, of iron, of titanium..., well observable in the visible domain. Depending on the speed of movement of the cloud, this may entail variable shifts for the different lines.

 

Taking all these various considerations into account, we will see later whether we can confirm or refute the existence of that dust cloud.

 

I. 2. Notable difference between the surface temperatures of the two bodies.

 

The surface temperatures of stars are determined by studying their emission spectrum.

 

When an intense beam of ordinary white light passes through a small slit, and then a prism or a grating, it spreads out into a rainbow called a spectrum. This spectrum goes from the highest to the lowest frequencies of visible light: violet, indigo, green, yellow, orange and red. As we can distinguish these colours, we call it the spectrum of visible light. We can use it to determine the chemical composition of distant objects. Different molecules or chemical components absorb different colours or frequencies of light, which may or may not be part of the visible spectrum. Each substance generates a series of characteristic lines in the spectrum, which constitutes its signature.

 

A star is regarded as a sphere of extremely hot, compressed gas which gives a continuous spectrum comparable to that of a black body (a body assumed to be perfectly absorbent). This continuous source is surrounded by a cooler and less dense gaseous atmosphere, which gives us absorption lines characteristic of the elements of the atmosphere. The study of the absorption or emission spectrum is called spectrography.

 

It has the following advantages:

 

• The identification of the spectral lines makes it possible to deduce the chemical composition of the stellar atmosphere as well as the temperature conditions prevailing there (conditions of ionization and excitation).
• The precise determination of the position of these lines makes it possible to measure the shifts caused by the radial movements of the star (speed of recession or approach: Doppler effect) or by a strong magnetic field (Zeeman effect)
• The photometric study of the spectrum makes it possible, among other things, to obtain the temperature of the atmosphere and that of the star.

 

Observation has shown that stellar spectra can be classified in a continuous series that depends on only one parameter: temperature. The spectral types called O-B-A-F-G-K-M, subdivided decimally, are characterized by the colour of the continuous spectrum and by the absorption lines of certain elements.

 

Table 2: Characteristics of the spectral types.

 

Figure 1: Spectral classes and associated spectra.

 

Astronomers have thus classified stars according to their temperatures or spectrum and their luminosities; this is what we call the Hertzsprung-Russell diagram (fig. 2). It makes it possible to describe the evolution of stars, from protostar to their final stage.

 

For most of their lives stars remain on the main sequence, which corresponds to a phase of equilibrium of the body. For the Sun this phase should still last some five thousand million years. It lasts all the longer, the lower the temperature of the star.

 

Figure 2: Hertzsprung-Russell diagram.

 

Astrophysicists use several definitions of temperature. To determine them, the laws established for the case of the Black Body are used, which to a first approximation apply to stars. Depending on the method used, the values obtained may differ slightly from one another.

 

We distinguish:

 

• A so-called colour temperature T_c.

 

We deduce it from Wien's displacement law (2), which links the wavelength of maximum intensity in the continuous spectrum with temperature, and from Planck's radiation law (3), which expresses the variation of intensity in the spectrum as a function of temperature. The latter will be obtained by fitting the shape of the curves (Radiation curve: fig. 3)

 

 

 

Figure 3: Application of Wien's and Planck's laws for the three bodies.

 

• A so-called effective temperature T_e.

 

It is the temperature at which a black body of the same surface would emit the same total energy as the star. The total energy is determined by calculating the area bounded by the energy curve (Figure 3). The temperature is deduced by the Stefan-Boltzmann law (4), provided we know the diameter of the star.

 

 

The surface temperature of Wolf 424 A is, on the hypothesis that it is a star and not a brown dwarf, about 2500 K, which places it in spectral category M (red dwarf). Iumma would have a surface temperature of 4580.3 K, which necessarily places it in spectral category K (orange star) (See table 2 and Figure 2)

 

We saw in the previous chapter that a dust cloud does not have a constant absorption value over the whole spectrum, but preferentially attenuates short wavelengths. This leads to a reddening of the light passing through it, which has the effect of shifting the maximum of the curve of intensity variation in the spectrum towards long wavelengths. Consequently, the value of the temperature determined by Wien's law will be lower than the intrinsic value.

 

However, if we try to fit the shape of the curve obtained to Planck's theoretical curve for various temperatures, we notice that the only truly comparable part over a large part of the spectrum lies at the long wavelengths

 

Figure 4: Comparison of the curves of intensity variation in the spectrum for different temperatures.

 

The curve of the attenuated spectrum was obtained by subjecting Planck's curve, corresponding to the temperature of IUMMA, to a progressive attenuation corresponding to that observed for interstellar matter.

 

Another check is made thanks to the absorption lines present in stellar spectra; as we specified earlier, they are a representation of the chemical composition and temperature of the stars. It is true that the constituent spectrum of an absorbing cloud is superimposed on that of the star, but unlike the star's intrinsic lines, which undergo variations over time (Zeeman, Doppler effects, etc.), those of the cloud are almost unchanging.

 

For these reasons it is impossible for us to make so large an error in evaluating the surface temperature of a body, and certainly not because of the existence of an absorbing cloud. An admissible error of a few tens of degrees is acceptable, but not of 2000 K!

 

I. 3. Notable difference between the masses of the two bodies and between their stellar radii.

 

One of the latest publications on Wolf 424, published in January 1999, has made it possible to remove ambiguity about the values of the masses of the components. It gives, for the main component of the binary system, a mass of 0.143 M_O. This value does not correspond to that of IUMMA, which would be around 0.75 M_O, that is, almost 5 times higher.

 

If we accept that the stars IUMMA and Wolf 424 are still located on the main sequence of the Hertzsprung-Russell diagram (figure 2), we can determine their stellar radii using formula 1. This is an extension of the Stefan-Boltzmann law and of Pogson's formula.

 

Here too the difference is significant! (Cf. table 1)

 

I. 4. Agreement on distances.

 

In 1966 the Ummites give the distance separating our sun from Iumma on 4 January 1955 as 14.436954 LY. On the other hand, it is only 14.421 LY on 8 July 1967.

 

If this difference is not due to an error (deliberate or not) in reproducing the values, we can attribute it to an approach of IUMMA and the Sun in our space.

 

Indeed, every body in our Galaxy is subject to various movements: its movement around the galactic centre, within its own system, and its rotation on itself. Thus the Sun is currently heading towards the constellation of Hercules at a speed of 19.4 km/s, and moves around the galactic centre at 250 km/s.

 

The displacement, or space motion, of the stars relative to our sun can be broken down into two quantities:

 

• The radial velocity along the line of sight, which is expressed in km/s and whose value may be positive or negative. It is determined by the shift in position of the spectral lines (Doppler effect).
• The proper motion, perpendicular to the line of sight, which is expressed in seconds of arc per year.

 

 

If the Ummites' figures are correct and the difference is indeed due to a movement of the body, Iumma would have a space motion of about 380 km/s (!) towards us.

 

The distance we assigned to Wolf 424 in 1991 is 14.05 LY ± 0.25 LY. The pair of stars has a proper motion of 1"76/year with a parallax of 0"233 and a radial velocity of recession of 20 km/s. Its space motion, deduced from these values, is about 40 km/s.

 

What can we deduce?

 

It would seem that Wolf 424 and Iumma are located at approximately the same distance from our sun; their proper motions, on the other hand, are very different.

 

I. 5. Conclusion.

 

We have seen that the data agree as regards the distance from the sun. As for luminosity, we have not so far been able either to refute or to confirm the existence of the dust cloud; this study will be carried out later. In any case, the disagreements over fundamental data such as the mass of the bodies and their temperatures are unequivocal.

 

Iumma cannot in any way be Wolf 424.

 

There are other reasons for this, not yet mentioned.

 

Wolf 424 A is a UV Ceti type body, more commonly called a flare star or eruptive star; the pair is designated in the catalogues by the abbreviation FL Vir (FL for FLare and Vir for Virgo, the constellation of Virgo).

 

This term flare star is linked to certain families of stars. The UV Ceti stars are essentially red dwarfs that show explosive increases in brightness, which often last only a few minutes and never exceed a few hours. They then return to their normal brightness. The amplitude of the variation can range between 1 and 6 magnitudes.

 

For UV Ceti stars these are supposed to be eruptions comparable to those occurring on the Sun. The energies released are equivalent for the two bodies, but since the sun is more than ten thousand times more luminous, this does not alter the total brightness of the body.

 

In the case of Wolf 424, several studies have revealed rapid brightening times of the order of 10 to 20 seconds, with average durations of the maximum reaching 15 minutes. About 10% of the energy emitted by the pair in the ultraviolet comes from these maxima. This system is one of the most unstable known since, on average, 4.5 maxima occur per hour.

 

The mechanism put forward to explain such a phenomenon, and especially for this system, points to a maser effect (acronym of Microwave Amplification by Stimulated Emission of Radiation, amplification of microwaves by induced, or stimulated, emission of electromagnetic radiation. If we transfer this to the visible domain we get the laser). This effect implies an increase in the magnetic fields of the stellar corona to values close to 250 G.

 

A very recent article (January 1999) removes any ambiguity as to the possibility that one of the components of the stellar pair Wolf 424 lies within the domain of brown dwarfs. It is the result of a campaign of observations of the system by the Hubble telescope. The precise data collected, being visual, on the relative positions of the pair have made it possible to determine precisely the real orbit of the two components. The new determination of the masses of the two stars gives for Wolf 424A: 0.143 M_O ± 0.011 M_O and for Wolf 424B: 0.131 M_O ± 0.010 M_O

 

These extreme conditions of the binary system rule out the possibility of life emerging on a hypothetical planet.

 

II. Study on the existence of dust clouds.

 

II. 1. Analysis of infrared detection.

 

In paragraph I.1 we dealt with the observational consequences of the existence of interstellar dust clouds. These would consist of objects in the form of elongated grains with average dimensions of 0.5 μm, composed of metallic particles and ice covering graphite. Nothing prevents, on a local scale, the existence of such a cloud, although it is rare.

 

Below are two photos of the portion of sky that interests us; they have been taken from a catalogue of the Institute that manages the space telescope.

The photo on the left (fig. 5a) was taken in the visible spectral domain. Wolf 424 is located in the constellation of Virgo, in a zone of low stellar density, since it lies outside the galactic plane, at the edge of the famous group of galaxies: Virgo and Coma. The sky coverage of the plate is 1 x 1 degrees of arc, which represents, at a distance of 14 LY, an extent of 0.058 LY². (The original of this plate can be found on the Internet at this address)

 

We notice that in the surroundings of Wolf 424 there is a notable decrease in stars of high luminosity (see marked zone). If this is really due to the presence of a cloud, the latter would have an extent of about 0.0004 LY².

 

We know that interstellar dust essentially absorbs short-wavelength radiation. Thus a photo, taken with a blue filter, of the central region of our galaxy, hidden by a dust cloud, will show very few stars, whereas in the infrared it will be swarming with them.

 

Several scientific satellites (IRAS, ISO, etc.) have explored the sky in this frequency domain. The IRAS satellite "saw" in four monochromatic bands centred on the wavelengths of 12, 25, 60 and 100 mm. The combination of these monochromatic images made it possible to deduce the infrared colours, which themselves reflect the temperature of the sources observed. The coldest (around 30 K) emit essentially around 100 mm, whereas the hottest (250 K) radiate at a shorter wavelength, around 12 mm. We have arbitrarily assigned the colour red to the former and the colour blue to the latter; yellow and green represent intermediate temperatures.

 

The photo on the right (fig. 5b) shows the same sector taken in the infrared by the IRAS satellite. The image also corresponds to an area of 1º x 1º. As the resolution of this plate is only 1'5 instead of the 1"7 of the previous plate, it does not allow us to detect stars, but only groups of them.

 

 

Figures 5a and 5b : NASA-STSCI plate

 

Iras 12 µm Iras 25 µm Iras 60 µm Iras 100 µm

 

Figures 6a, b, c, d: Infrared photos, at various wavelengths, of the selected sky zone.

 

The network of filaments that we can make out in figure 5b has been named cirrus. They are thin, cold dust clouds. Their temperature of around 30 K is characteristic of graphite, one of the materials that go into the composition of the dust grains of interstellar clouds. Their distance is not known for the moment. The parallax method has only made it possible to set a lower limit of 1000 astronomical units (1 AU = 150 million km -Earth/Sun distance-). However, their almost uniform distribution over the celestial sphere suggests that part of these cirrus may be close by and surround the solar system.

 

One of these filaments covers the zone of sky in which Wolf 424 is located. But the impossibility of specifying the exact distance of the filament and its density does not allow us to conclude.

 

II. 2. Study of the differences between the photographic magnitudes in the blue and the red.

 

The United States Naval Observatory, under the aegis of the US Navy, publishes a catalogue containing the photometric data of stars down to magnitude 20. These values are available for the colours blue and red. Figures 7a and 7b show a visualization of these data. The diameter of the stars is inversely proportional to the value of the magnitude. Thus the higher it is, the less luminous the star and therefore the smaller the associated diameter.

 

We saw in the previous study that there is what we call cirrus in our zone of investigation, but that it was impossible to know the distance to those objects precisely.

 

We know that of Wolf 424, around 14 LY, and on the other hand, in the same zone of sky, we find the reference star TYC 0874-00235-1, of visual magnitude 11.16.

 

Following the famous Hipparcos mission, two catalogues have been published: Hipparcos and Tycho. They include the astrometric data (position, parallax, proper motions) and photometric data (magnitudes in the blue and red) of more than a million stars. This has allowed us to know the position of a star relatively close to Wolf 424 but at a distance of about 40 LY.

 

Figure 7a: magnitudes in the red Figure 7b: magnitudes in the blue.

 

Table 3

 

The other stars of the field all have magnitudes in the blue that are greater than those they have in the red. From table 4 we see that this is not the case for Wolf424, but it is for Tyc-235. If this difference is not due to an intrinsic radiation characteristic of the star, it could be attributed to the fact that the reddening of the stars, due to obscuration by interstellar dust, seems to operate, in this zone, beyond a distance of 14 LY.

 

This study shows that the dust density of the filamentary network revealed by the previous study is not great enough to "redden" the spectrum of Wolf 424.

 

But nothing prevents its density in another zone from being high enough to attenuate the luminosity of Iumma as the Ummites indicate.

 

II. 3. Study by statistical counting of stars of similar apparent magnitude.

 

This method, developed by the astronomer M. Wolf, makes it possible, thanks to statistical counting, to reveal the presence of a dark cloud. We start from the fact that, statistically, stars of a given apparent magnitude are located at a given distance.

In an unobscured star field, the number of stars whose magnitude goes up to a limit value increases as this magnitude increases, and the curve has a very regular slope.

 

But the presence of a dark cloud disturbs this regularity: the curve, owing to absorption, shows a bend, and then continues below the unobscured curve.

 

In order to test the validity of this method, we have taken as a standard a complex of dark clouds located near a young open cluster, IC5146, located about 1000 parsecs (pc) away, in the direction of the constellation of Cygnus. This cloud complex has been the subject of numerous studies.

 

This method requires knowing the magnitude of the stars, that the population of those located behind the cloud be comparable to the reference one, that the absorption be uniform over the whole field and that the stars all be located behind the dark cloud.

 

We have thus defined two zones with the same area, one containing the dark cloud and the other relatively close and free of all absorption. (Table 5)

 

Table 4

 

The apparent visual magnitudes of the stars contained in these two zones are provided by the catalogue of the United States Naval Observatory. See below the graphs obtained for this test zone.

 

Figure 8: Comparison of the graphs for the zones with and without a dark cloud.

 

 

We clearly distinguish a characteristic bend in the curve corresponding to the zone containing the dark cloud. The values of the apparent visual magnitude framing the bend make it possible to obtain, thanks to a nomogram, the average distance of the dark cloud.

 

Nomogram 1: Theoretical curve that makes it possible to obtain the distance of the dark cloud from the apparent visual magnitude deduced from the disturbance in the numerical distribution of the stars

.

The dark cloud detected in this zone is located at a distance of between 470 and 550 parsecs. These values agree with those given in the literature.

 

Let us apply this method to our case. Below is the table of the zones chosen.

 

Table 5

 

 

Figure 9: Curves corresponding to our zone of investigation.

 

The result is less conclusive than in the previous case, for numerous reasons:

 

• The statistics are less favourable, since we are in a zone relatively poor in stars.
• The deficit of bright stars (therefore of low magnitude) does not allow us to go beyond a distance of 100 parsecs, therefore beyond our limit of investigation distance (3.7 pc.)

 

Consequently, this method cannot be applied to our case unless a dark cloud were present at a distance of at least 300 pc.

 

II. 4. Conclusion.

 

The research methods used have made it possible to reveal the existence of a cloud of cosmic dust in the direction of Wolf 424.

 

On the other hand, they have not allowed us to provide any information as to its density or its distance. However, the photos (figures 6a to 6d) obtained from IRAS satellite data give an impression of its distribution.

 

The existence of this cloud or of its filaments is also compatible with the fact that the Ummites learned of our existence thanks to the interception of a radio message. Indeed, as we have seen in the previous chapters, dust lets through long-wavelength radiation, which is the case for radio waves. On the other hand, they would have the same problem as we do in the visible domain: our sun must seem very pale to them.

 

Summing up the two previous chapters, we can put forward 3 new working hypotheses:

 

1. Iumma really exists and is located near Wolf 424.
2. Iumma is located in a completely different stellar zone.
3. Iumma does not exist at all and this part of the UMMO affair is false.

 

To answer points 1 and 2, it is necessary to have access to photos of the stellar zone of Wolf 424 as well as to the characteristics of the exposures. Point 3 will be deduced from the results of the two previous points.

 

III. Analysis of existing photos and search in star catalogues.

 

III. 1. Preliminary analysis of the photos.

 

In one of their texts the Ummites explain that Wolf 424 could also be one of the stars close to Iumma: the first would be located 2.07 LY (surface temperature 3210 K) and the other only 0.62 LY (temperature 2575 K) from their sun.

 

(To be continued)

 

(U-C Note: Alain Ranguis has not continued to develop this study, at least as far as we know)