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Suppose that you are an extraterrestrial being, member of a mission towards planet Earth. For certain reasons, you write letters to a Spanish pseudo-professor who is in fact for a long time a mildly crazy and very credulous amateur of esotericism and stories of "men from space", which he himself is telling around for quite a while.
In these letters, you start by providing some astronomical information about the star system you come from, this is only normal.
If you really are an alien, it may very well happen that you give information which is not yet known on Earth, voluntarily or involuntarily, and that thereafter, their accuracy becomes proof that you were really an alien visitor!
But on the other hand, if you are not really an alien but merely a prankster who created a hoax to have a laugh at credulous "professors", you endeavor to give some credibility to your astronomical data by consulting some articles on astronomy. You choose a star that really exists, which is close to ours, so that you don't get too much rejection by people that argue that interstellar space travel is impossible or very long, and you choose a start allowing that some civilization if aliens of human appearance could have appeared there (*) and so on.
If, thereafter, it proves that your data were erroneous, you would try to catch up with the errors one way or another. Even if practically everyone realizes your mistakes and laughs at it, there are enough credulous people who would still faithfully buy your snake oil!
Here is what the "Ummites" wrote about their star.
In a book of Martine Castello, Isabelle White and Philippe Chambon published in 1991 and entitled "La conspiration des étoiles - Les Ummos terrestres ou extraterrestres" (The conspiracy of stars - Ummos terrestrials or extraterrestrials)", page 50, there is a letter which is presented as written in 1965 (*) and received by ufologist Antonio Ribeira who states that in "Ummo: the language of the aliens". In this letter, the "Ummites" indicate that the planet from which they come is named Ummo and revolves around their named star Iumma, and:
The "Ummites" say that Iumma would be probably the star that we call Wolf 424, but it would not be easy to establish that because our astronomy is not very precise, and that complicates the change of reference frame which they must make to find their star such as sighted from ours:
And:
In a letter which would be later referenced as "D32" and which can be found at www.ummo-sciences.org/fr/D32.htm where it is dated of March 18, 1966, a letter sent to the so-called "professor" named Sesma, they say:
In other words, they are not completely sure that their star is the one we call Wolf 424, but that coincides in a surprising manner.
The reason the "Ummites" are not sure is, they say, because...
In a letter D 36 which is said to be of June 1966, to Sesma and Garrido, available at www.ummo-sciences.org/fr/D36.htm the "Ummites" who had some problems with readers who find their data on Wolf 424 erroneous, try to specify:
And:
And:
In a letter which will be references as "D41-1" and which one finds at www.ummo-sciences.org/fr/D41-1.htm dated before March 11, 1966, sent to Sesma, the "Ummites" write:
The "Ummites" give the distance between our sun and their star Wolf 424 that they call Iumma:
They specify that their trip to Earth is not their first spaceflight. They traveled much already, they write it in a letter to Sesma (www.ummo-sciences.org/fr/D41-16.htm):
The galaxy has a diameter of approximately 100.000 light years, which makes them very performing space travelers.
The Earth is not the first planet they visit, one of the other planets that they said to have visited is 10.000 light years of theirs, which gives the opportunity to them to specify their performances:
They can thus sometimes travel a 10.000 light years in 90 days about, which is a quite impressive performance. At this speed, they would cross the galaxy from one end to the other in only two years and half. For a planet which would be at 10 light years of theirs, that is to say "next door", they would be there in two or three hours at this speed. But let us forget that, because they specify that it all depends on "crumplings" in space which change in a random and unforeseeable manner except in the short run.
Of course you can interpret the above unclear line more optimistically as "40.078.427,56 of thousandth of 86 Earth days, which means they traveled 10.000 light years in 0.02 days... or cross the galaxy in 0.2 days i.e a few hours.
Let's remember that it means that according to the "Ummites" the distances between stars vary in the course of time because of some sort of space warps. They are sometimes remote, sometimes close, which the "Ummites" write to professor Sesma in 1966 (http://www.ummo-sciences.org/fr/D45.htm):
So, on January 4, 1955, between their sun and ours, there is a 3,68502 light-years distance, but there is also a bit more than 14 years lights, or, it is longer than 4.4 light-years. It depends when.
In another letter, they indicate 14 light-years of distance again, in connection with a radio signal that left the Earth between the 4th and the 8th of February 1934 which took 14 years to arrive on Ummo, therefore arrived in 1948 from the terrestrial reference. (http://www.ummo-sciences.org/fr/D57-1.htm):
Once that radio wave received, they waited a little more than 200 days so that a favorable "fold" of space occurs, they take off from Ummo and arrives towards Neptune on January 7, 1949, and land on Earth on March 28, 1950. They thus spent a few months to cross the 4 years lights that the space warp which they used to shorten the "normal" 14 light-years distance.
Before seeking to check the "Ummites" information, it is wise to get the chronology of our own knowledge on Wolf 424: what we know, how we know it, and since when we know it. The chronological table which follows fixes the situation insofar it is relevant to the Ummo affair.
Also, it is useful to know that Wolf 424 A has various designations according to catalogues: Wolf 42A, Gliese 473A, G 12-43, G 60-14, LHS 333, LTT 13546, and LFT 923. As for Wolf 424 B, designations are also Fl Vir, Gliese 473B, G 236-65 B, and LHS 333B.
| Date: | By: | |
|---|---|---|
| 1919 | Max Wolf, astronomer. |
Wolf 424 was known before the "Ummites" say the come from there, the Ummites know that, the ummologists know that that not every Ummo-fan knows. It had been discovered by Maximilian Franz Joseph Wolf (1863-1932), a pioneer of astrophotography, hence its name. That star is discovered on photographic plate taken in visible light through a telescope, it is invisible to the naked eye. It is in the Virgo constellation. The star enters Wolf's "Katalog von 1053 starken bewegten Fixsternen" under the name of Wolf 424 in 1919. |
| 1927 | Wolf 424 is observed by several astronomers and shows a relatively round form which still let think that it is a single star. |
|
| 1937 | In the observations, Wolf 424 did show, little by little, not a single star (a round) but a lengthened form. The maximum of lengthening is reached in 1937, and it is that year that the obvious explanation appears: it is a binary system, formed of two stars orbiting around each other, named from now on Wolf 424 A and Wolf 424 B. |
|
| 1937 | Astronomers start to make photographic and visual observations of Wolf 424 amongst other reasons in order to determine the orbital parameters and the masses of two stars of the binary system. |
|
| 1938 | The Time |
The very famous Time magazine of May 23, 1938 publishes an article on the discoveries of close star and not only mentions Wolf 424, but makes of it the star that is probably the nearest to the sun, an imagination-striking information, and at a distance from 3.7 light-*years which is practically that given initially by the "Ummites", 3,68502 light-years, before it changed to 14.6 by virtue that the 3,68502 light-years distance was via a "temporary space warp"! The magazine indicates that Professor Gerard Pieter Kuiper found that Wolf 424 has an unusual "very late M-type" spectrum which indicates that the star is 50,000 times less luminous than the sun. Its apparent magnitude is 11.8, which is about six magnitudes be low the limit of naked-eye visibility. Comparison of the apparent with the intrinsic brightness yielded the distance. They also mention that Director Otto Struve of Yerkes would not say for sure that Wolf 424 is the sun's nearest known neighbor. It may be a double star, in which case the combined light of the two components would make it appear closer than it actually is. Parallax measurements requiring a year or more will be necessary to settle the contest between Proxima Centauri and Wolf 424. The very interesting part of the article is that the distance of Wolf 424 from the sun indicated in this very widely diffused magazine is the distance indicated initially in the Ummo letters! "Its (Proxima Centauri) distance from the sun is 4.3 light years — about 25 trillion miles. In 1915 Dr. Robert T. A. Innes of Johannesburg discovered, by parallax observations,* that a faint star near Alpha Centauri was only 4.16 light-years away. For 23 years, up to last week, that star, appropriately called Proxima Centauri, held rank as the No. 1 solar neighbor. Last week, from the University of Chicago's Yerkes Observatory in Wisconsin, it was announced that another faint star, Wolf 424 appears to be only 3.7 light-years distant. This is so close that a train traveling a thousand miles a day would get there in 60 million years."
It should be noted that still nowadays, Ummo-proponents who did not seek themselves an answer, doubt that it is certain that "the observatory of Yerkes had given a distance Wolf 424 of + or - 3,68 Al in catalogues former to the beginning of 1966". What precedes should answers their doubts. |
| 1938 | Dirk Reuyl | This astronomer studies photographic plates of Wolf 424 and announces that in his opinion it really is a binary system. |
| 1938 | Kuiper | This astronomer visually observes Wolf 424 AB with the telescope and announces that indeed, they are really a binary system of two stars. |
| 1939 | Pierre Rousseau in his book "Exploration du ciel", Hachette, 1939, p 87, indicates the distance between the Sun and Wolf 424 as of 3.68 light years (source Dominique Caudron). |
|
| 1967 | Kunkel | Kunkel studies by measurements the variability of luminosity of the Wolf 424 AB system. |
| 1972 | Heintz | His measurements indicate that the two stars have masses of 0.067 and 0.064 solar masses. |
| 1973 | T.J. Moffett | T.J. Moffett publishes " Wolf 424: a neglected flare star." He indicates that whereas Wolf 424 A and B are two almost identical stars having the masses among the lowest known for stars, one or both have an 8% luminosity variation in the ultraviolet band, therefore more variable than Kunkel had indicated in 1967. |
| 1988 | Geyer, Harrington, Worley | These astronomers make comparisons with Gliese 65 AB and estimate that Wolf 424 A and B are indeed very small stars. |
| 1989 | Heintz | The astronomer used photographs and measures taken from 1968 to 1988 and estimates that Wolf 424 A and B are right below the limit to be stars and are thus brown dwarfs. |
| 1991 | Hubble |
The Hubble space telescope provides the first photographs of Wolf 424 AB in infra-red light on which the two stars appear distinct:
|
| 1991 | T.J. Davidge et P. C. Boeshaar | The two astronomers observe Wolf 424AB in the near infrared and examine their spectrum. They show the similarity with Gliese 65AB and Gliese 866 AB and show that if Heintz is right about the system being of substellar masses, then the system is aged approximately only 100 million years. |
| 1992 | Henry et al. | The team of astronomer Henry made of better measurements and estimates that Heintz was mistaken: Wolf 424 A and B are a little bit bigger than he thought and therefore they really are very small stars. |
| 1996 | Hubble | The Hubble space telescope provides the first photographs of Wolf 424 AB in natural light without any filter on which the two stars appear distinct. |
| 1998 | Hubble | Using Hubble space telescope data, astronomers estimate that Wolf 424 A and B are not the brown dwarfs, but are just below the maximum limit of stars, hence very small stars, small red dwarfs. |
| 1999 | G. Torres, T.J. Henry, O.G. Franz, L.H. Wasserman |
These astronomers study the size of Wolf 424 AB. They present in American Astronomy Journal (562-573) of January 1999 new measurements which they took using the Fine Sensors Guidance of the Hubble space telescope, that show that the masses of two stars are indeed just above, and not just below, the minimal mass of stars, and that they are thus not brown dwarfs. They confirm the variations of luminosity of the system, and indicate that it suggests a strong activity of sunspots on Wolf 424 B while Wolf 424 A has a constant luminosity typical of M dwarfs stars. Wolf 424 B has approximately 13% of the mass of the sun, 14% of the diameter of the sun and only 8/100,000e of the luminosity of the sun. |
| 2006 | B. R. Pettersen | This astronomer makes measurements on the variability of luminosity of Wolf 424 AB. He records 57 surges of increased luminosity in 20 hours of observation. He compares his measurements with measurements in 1980, and his analysis indicates that the flares had varied during the years according to the changing distances between the two stars, which changes in 16 years cycles. |
In the early "contactees" hoaxes in the Fifties, the contactees located the origin of their extraterrestrial friends primarily on close planets. But quite soon, it was no more possible to claim that they come from Jupiter or Saturn, because sensible people had already made fun of that: the large gas planets do not even have a solid surface to walk on. Mars did not suit much either because more and more data arrived making impossible that a technical humanoid contemporary and indigenous civilization resides there: Mars was presented little by little like a "dead planet", some sort of "bigger moon" (a largely erroneous vision, but it was indeed the image which took shape during the Fifties). There remained Venus, about which not much was known but that was currently described as "our sister planet" But in the sixties, when the first "Ummites letters" appear, Venus was already outfashioned: a suffocating atmosphere of 400°C on ground level. It was thus necessary to relocate the aliens around another star. Of course, the nearest was ideal, since it limited the objections that everyone automatically put forth at the time on the "impossibility" of "interstellar travels" considered to be "much too slow."
The other plus of another star than the sun was of course that we were still far from being able to go check there if there are really aliens on some planet.
Thus, in the other hoaxes of this era, the inhabitants of planet "Auco", according to what Saliano told the very same Sesma, came from Alpha centauri at 4.4 light-years, and the "Bââvites" who wrote "Bââvites letters" to Robert Charroux came from Proxima Centauri within 4.2 ligh-years.
We saw that in the above table: at a certain time, it was very widely propagated in the Press that Wolf 424 is the nearest star to ours, it was quite simply a logical choice for a new hoax.
Of course, the choice of Wolf 424 at 3.68 light years was practically the only possibility for the hoaxers: all the other close stars were already "inhabited" by other aliens: Auco at Alpha Centauri, the "Bââvites" at Proxima Centauri... There was simply "no vacancy" anymore among the closest nears except for wolf 424, the "closest"! However it was important not to be put in " competition " near Sesma and its friends who believed completely in the "Auco" and "Bââvi" stories. Another close star, which was not already "occupied" was needed, and Wolf 424 was ideal as the next one, Barnard is at 6 light years, then we have Wolf 359 at 7.8 light--years, and the next ones are all beyond 8 light-years.
It was an erroneous choice, but while the news "the star nearest to ours is Wolf 424" was widely spread in general public magazines and books, the correction of the distance error, which put the star a bit more than 14 light-years away, was the kind of news that does note create a sensation and thus remains in little-spread professional astronomy journals, in ignorance of the letters' author. It is really when the error was revealed to Sesma who had received the letters and read them publicly in a pub in Madrid, that the nest letters tried to "catch up" with the error by an easy trick which placed Wolf 424 at the corrected distance of 14 light-years while claiming that the 3.68 light-years was "space-warp" shortcut.
The big glitch, that the Ummo-defenders do not want to see, is that this "shortcut" distance was precisely exactly that given initially by astronomers by mistake as the distance Sun-Wolf 424!
The "counter-argument" on the glitch by certain Ummo-partisans is to flatly claim that "as soon as the first letter about the 3.68 light-years" the "Ummites" in would immediately have indicated at the same time that the 3.68 is the distance in the convenient hyperspace and that they mentioned the 14 lights-years of "normal" distance too. This is simply false. Nobody seems to really know which is the "first letter". The people who received them, Sesma initially, did not consider useful to date precisely the arrival of each letter. It were diffused publicly only later, for example by Ribeira in 1969 for one of it of which all that one can say is that it dates according to 1967 because it comprises accounts of events of 1967. But the true chronology of the writing of these letters is claimed to be a true headache, which conveniently allows all the liberties because the initial ummologists of the time were not at all rigorous people but credulous eccentrics (such as Sesma, first recipient of the letters).
In any case, the most consensual chronology of the ummologists is actually:
What is absolutely certain is that letter D41-1 says:
There is, in this letter, absolutely no mention that this would be a distance in some "space-warp" shortcut, no mention of any doubt that WOLF 424 is the correct star, and no mention of any 14 light-years distance, nothing at all of all this!
Worse, this information is on first page of a batch of 112 pages sent to Sesma, whose text shows very clearly that it is the FIRST CONTACT, while ALL the other letters are CLEARLY FURTHER INFORMATION.
This letter of FIRST CONTACT starts as follows:
It is this letter of FIRST CONTACT which indicates in its continuation:
It is really the first in the chronology, like Jacques Vallée said!
According to Ummo-Science.org, which says nothing of the date given by Vallée it is "1966" with no additional precisions!
What is clear, I insist, is that there is NO mention of 14 light years, only that of the 3.8 light years in this first letter, and no mention of any "space shortcut", no doubts about Iumma being Wolf 424, all this comes only LATER, in LATER letters.
All the other letters, those that introduce the 14 light years, those that introduce doubts about Wolf 424 being the right star, those that introduce the "space warp" trick, are WITH NO DOUBT later letters, here is the evidence:
The CHRONOLOGIALLY NEXT letter, D45 start with "Professor Sesma Manzano: Our comrade forwarded your request for FURTHER INFORMATION to us; which is given to you on the History and the Philosophy of UMMO."
Those are FURTHER INFORMATION, and it is in this letter that "Ummites" try to catch up with the blunder of their FIRST letter of introduction by working out the space warp trick and only now mentioning the 14 lights-years normal distance and REINTERPRETING the 3.68 light-years.
This D45 letter, according to Ummo-science.org is said to be "undoubtedly former to March 11, 1966". But, as vague and unjustified and without effect it is (January 1965 is well prior to March 11, 1966), it CANNOT HAVE BEEN SENT BEFORE D41-1.
The next letter would be D 32. It is of course also not a "first letter", at all! It is a letter of correction on blunders concerning measurements units in previous letters. The correction consists in telling that the previous letters spoke in "Ummo measurement units" which are "not the same as on the Earth." The letter is clearly not the first and NOT prior to D41-1. It starts as follows: "Professor Fernando Sesma, throughout our documents we were obliged indistinctly to use modules and units sometimes of the Planet Earth... "
And so on! It is absolutely clear that D41-1 is the FIRST, and this proves the reality of the terrible glitch of the Sun-Iumma wrong distance, that the 14 light-years, the doubts about Wolf 424 being Iumma and the introduction of the "space-warp" trick all come later in later letters.
When the Ummo-proponents tell you that "as soon as the first letter" the 3.68 light-years were "explained" as a distance in some particular space warp conditions, they tell you pure and simple BS!
But as their credulous readers trust them, as they thus do not read the letters and do not check anything, they eagerly buy that...
Many authors, even sympathetic to the notion that Ummo aliens exist and wrote these letters, are very embarrassed: for the astronomers, Wolf 424 is not one star, but two stars orbiting one around the other, a binary system, with stars Wolf 424 A and Wolf 424 B. Their embarrassment comes from the fact that the "Ummites" speak only about one Wolf 424 star, which is naturally a strong indication of hoax: when your planet has two stars, to mention only one is quite weird.
For example, on ufoweb.free.fr/wolf.htm this embarrassment is expressed by Alain Ranguis, speaking about this topic, from "Ummo letters":
The simplest explanation of that oddity is rather obvious: the general public literature, books on space and Press articles, mentioned without much detail of clarity that Wolf 424 is a "binary system", and the author of the letters understood in this: "a star and a planet" instead of "two stars". The Press said THE "closest star" is a "double system", a star and something else, therefore a planet.
You might recall the distance given from their star to ours by the "Ummites" in the D41-1 letter at www.ummo-sciences.org/fr/D41-1.htm
The "Ummites" give the distance between their star and ours:
You might recall what was indicated in the D36 letter ( www.ummo-sciences.org/fr/D36.htm ):
Isn't it just a bit odd that it is practically the same figure which come again for two measurements of different distances in different units? From the astronomical point of view, it is a "remarkable unnoticed coincidence". But from the psychological point of view, with an author without competences in astronomy trying to "put some numbers out", in a hasty context of "fixing the glitches that people found", it is much less astonishing that similar figures arise spontaneously.
The "Ummites" letters indicate a magnitude (luminosity) for Wolf 424; which is completely false.
When that was told to Sesma, the "Ummites" answered: well, that was because of a cloud of dust which weakens the luminosity of Wolf 424 for our telescopes.
You would laugh at such an obvious trick, wouldn't you?
In reality, there never was a cloud of dust. In 1994, Castello, Chambon and Blanc already announced it in their book:
A very localized cloud is not a good explanation either. Wolf 424 is only at 14 light years. Imagine a cloud of dust 14 years lights deep, on the basis of the sun and going until Wolf 424: it would have been noticed. Thus the cloud must be well closer to Wolf 424. Right in front of it, and rather tiny. Much less than one year light thickness, much less than one year light of width. A very small very dense cloud?
Yes, the explanation by the cloud is given by Ummites for a simple reason: they had given erroneous values for the brightness of the star (its magnitude). To catch up with the blunder that Garrido had pointed to Sesma who spoke publicly of this, they sent him a new letter, D36 (see www.ummo-sciences.org/fr/D36.htm ):
But this is simply one more glitch! They clearly put the cloud between us and them, at 12 light years of their star, so it is 2 light years from ours since there are 14 light-years between both! It is an egregious blunder because at 2 light years from the sun, one is still in the borders of dust of our own solar system, and it does not have any cloud there who should mask a lot of the sky in that direction (people generally do not realize that there is still matter of the solar system almost halfway of Proxima of the Centaur, the star nearest to us who is to 4 Al and some. When one leaves the solar system, one enters almost immediately the system Alpha Centauri).
Lastly and lately, certain defenders of the "Ummites" ensured that images by the IRAS, ISO and other satellites show a "cloud in front of Wolf 424". Not! These "clouds" are completely insufficient to catch up with the "Ummites" blunders on the one hand, on the other hand they are distributed on all the vault of the visible heaven and not just "in front of Wolf 424". Certain defenders of Ummo suggest that the "discovered" cloud would be opaque enough to dissimulate a whole "unknown" star near Wolf 424, but this is only more wishful thinking.
In any events, the measurements methods for the masses and the temperature of stars can absolutely not be affected enough by any cloud to the point of correcting the hugeness of the Ummites blunders: wrong mass and star type, wrong magnitude, wrong size, single star.
All that shows that to correct a terrible mess concerning the luminosity, more blunders are made. A situation perfectly compatible with the thesis that the letters are just an uneducated hoax.
Wolf 424 A is a very small star, having less than 17% of the diameter of the sun and approximately 14% of the mass of the sun, very cold, one of the least luminous stars in the vicinity of the sun. It has only 14/100,000 of the luminosity of the sun: only the convection movements bring energy from the fusion at its core towards its surface.
According to the "Ummites", Wolf 424 has an apparent visual magnitude of 5.6, but actually it is 13.6, which makes it incredibly less luminous.
According to the "Ummites", Wolf 424 has an absolute magnitude visual of 7.4, therefore a little less brilliant than the sun, but actually the visual magnitude of both stars Wolf 424 A is only of 14 approximately, which is incredibly less brilliant than the sun and to the Ummites' claim.
Imagine we replaced our sun by Wolf 424 A. What would the sky look like?
Well, Wolf 424 A is so little brilliant that you would need a telescope to realize that it has a round shape.
The day, its light would be so weak that it would not light our planet more than 10 full moons.
As for Wolf 424 B, it is a little less brilliant.
For Ummites, their star is hardly different from the sun: just a little smaller, just a little less brilliant.
But in reality, Wolf 424 A and B are so small that it was a long debate and much observations before being sure that they are at least large enough to be called stars, i.e. bodies large enough so that they get hot enough so that nuclear fusion starts. Wolf 424 A and B are just on the border between star and non-star, among the smallest known stars. For these smallest stars, the temperature of the surface is much lower than that of the sun. The sun has a surface temperature of 5780 °K, the "Ummites" wrote that their star has 4580,3 °K surface temperature but in the reality Wolf 424 A and B have surface temperatures of less than 2000 and 2500 °K.
In fact, for these smaller stars, only the core is in the state of nuclear fusion. Consequently, surface temperature is quite low and is only heated by the diffusion of the core heat towards surface by movements of convection.
Note: because the temperature measurements are made by various methods among which spectral methods, even with some "cloud of dust" in front of our apparatuses, an error on the temperature measurement would be only in the order of ten degrees, and never of 2000 degrees.
According to the "Ummites", the mass of their star is of 1,48 1030 kilos, that is to say a little less than the sun and its 1,991 1030 kilos.
But actually, the mass of Wolf 424 A is only about 0,151 1030 and that of Wolf 424 B only of about 0,245 1030 kilos.
For better representing the masses of stars mentally, the astronomers express them in "solar masses": The Sun has a solar mass of 1.
For Ummites, their star has a solar mass of 0.75 but when the solar mass of Wolf 424 A is only 0.143, five times less than what they had claimed, and Wolf 424 B is of the same order of mass.
This article will not deal with "Ummites" errors concerning their planet itself. We will see that it would be quite useless! I indicate here only the errors concerning their star, and what these errors imply about their planet.
By convention, the distance between the Sun and the Earth is called "one Astronomical Unit", "AU". The Earth is at 1 astronomical unit from the Sun. March is at 1.5 AU of the Sun. Jupiter is to 5.2 AU from the Sun.
How many Astronomical Units are Wolf 424 A and B apart?
Well, the fact is that this distance is very variable the two stars have a very eccentric orbit around each other instead of a circular orbit.
This distance varies between 2.6 Astronomical Units and 4.2 Astronomical Units every 16 years approximately. The illustration below shows the kind of orbit that the two stars move through one around the other:

By comparison with our solar system, we have Wolf 424 A which would be where the sun is, and Wolf 424 B, having practically the same size as Wolf 424 A, would wander somewhere between Mars and Jupiter.
You might suspect it: a planet which would be somewhere in-between these two stars distant from 2.6 to 4.2 or in orbit outside of the orbit of these two stars would have characteristics quite different from those of the Earth:
In all the cases, it is quite simply impossible that a planet like the one described in the Ummo letters, with a form of life of the human type like the "Ummites" are, can exist around or between these two stars:
Do the letters give the distance between their star and their planet? Yes, in two places.
So we have there in this letter whose date is given as 1966, 99,6 million kilometers between the planet and the star of the "Ummites."
The "Ummite" letter D84 at www.ummo-sciences.org/fr/D84.htm also indicates the distance between their planet and their star, this time IN CENTIMETERS:
Do not ask why these aliens would now give this astronomical measurements in centimeters, that IS a true mystery!
With this distance from one or the other of two stars, according to the erroneous magnitude given by the "Ummites", it receives already five times less light than the Earth receives, which already places it outside the habitable for a human creature like the Ummites are. It is already scientifically highly laughable to imagine the evolution on separate planets resulting in identical creatures on different stars' planets, but if these planets are also very different, it confines to the BS of the highest order. (On the other hand, as by chance, it is a "fashionable" idea, within the world of the "contactees" hoaxes to describe their alien friends as "similar with us", with very few "differences" such as for example "their telepathic powers" etc.)
Knowing the real luminosity of these stars, it would have received in fact less than 10% of what we receive from the Sun. By way of comparison, Mars, which moves between 1.38 and 1.66 UA of the sun, receives only twice less light than the Earth from our Sun.
Can we imagine some convenient "greenhouse effect" which catches up with the error? Not, for the "Ummites" describe a composition of their atmosphere similar to ours, and NO greenhouse effect. And especially, the orbit not being possibly circular, with a choice between ejection or a remote capricious trajectory, the atmospheric conditions cannot be stable, the conditions of lighting must vary, the temperatures also. The planets of Ummites is quite simply not possible.
You can easily imagine the disturbances of the orbit that obligatorily result from the situation. But the "Ummites" do NOT indicate a disturbed orbit of their planet at all, on the contrary, they claim an orbit that is more circular than that of our good old Earth.
In such a configuration, with two stars of comparable luminosity, close one to the other and a planet put in there, between stars that have a complex orbit with distances between 2.6 UA and 4.6 UA by cycles of a few 16 years, it is not even possible to speak about days and night as we do on Earth with its single star, but the "Ummites" do claim that their days are of 31 of our hours...
In the same manner, the "Ummites" claim the use years, defined as on our premises in connection with the time to complete a full orbit of their (not) single star (time divided by 18 for some mysterious reason). But with two stars and their planet between the two or more distance of one or the other that are not to it one of different, this definition of the year does not mean anything at all: the orbit cannot be circular, it cannot be completed in the same duration each time, their definition of the year is impossible.
A word on the Ummoyear.
Ummites define something equivalent to our years. Like us, this measurement is based on the time to achieve 1 orbit of their star, which the Earth does into 365 around the sun.
But the "Ummites" divide this time by 18. They call this unit a XEE. An earthly XEE would be 365/18 days, some 20 days.
But how many Earth days are necessary for their planet to revolve around their star?
In the most initial letter claimed to going be of 1966:
A XEE is thus 0.212 Earth-years. Therefore three XEE are 0.212*3 Earth-years, that is to say 0.636 Earth-years. In days, this is 365*0.636 = 232 days. So their planet orbits their sun in 232 Earth-days.
But the number of days that is necessary for their planet to make one orbit around their single star can also be deducted from indications in letter 41-6 of the same year 1966, a letter about the "everyday life on Ummo", which tells of the duration needed to educate their children as follows:
Thus, 28 XEE are like 6 Earth-years.
28 XEE are thus 6*365 days i.e. 2190 Earth-days.
Thus 1 XEE is 2190/28 days or 78 days.
As 1 XEE is 1/18 of a revolution around their star,
thus 78*18 days are needed for Ummo to make one revolution around their star, that is 1404 days, nearly 4 years.
Here thus a huge contradiction again! Their year is of 232 days here, and 1404 days elsewhere...
To catch up with the enormous blunders which led to the astronomical impossibility that a planet inhabited by beings of the human type and as described in the Ummites letters exists in orbit around Wolf 424, the Ummo proponents are currently opposing three lines of argumentations.
The first is that in their letters, the "Ummites" indicate that they sometimes voluntarily lie. They thus could lie about the localization of their planet. Why not? This is undebatable: any huge error in the letter would thus be of zero significance as proof that the letters are not written by aliens. But conversely, this means that there is no possible astronomical proof to find from research on astronomical "exactitudes" of the Ummites letters concerning their star or their planet. As all is in error, we must believe that the errors are "on purpose", if ever something were right, it would be wise to think (it is not obvious that the Ummo proponents are happy when we think), it would be wise to think that it would be mere luck.
The second is that their star would not be really Wolf 424, but another star. In certain alternatives, it would be another star in the direction of Wolf 424, direction which is indicated by Ummites themselves. But at 14 years lights, in that direction, there is of course no other star.
The third is that their star would be another star, in another direction. The "Ummites" would lie us (that is perfectly compatible with the thesis of a hoax, of course, but that does not appeal to the Ummo proponents). This brings us back to ground zero: we do not know anything of their star then. For example, one Ummo supporter defends that their star would be actually Alpha Centauri. This star is in another direction than Wolf 424AB, the constellation of the Centaur and not Virgo, and at another distance, 4.4 light-years instead of 14 light-years. Why Alpha Centauri and not any other star? No reason for that.
What is interesting here is that all this provides you a means of estimating the competence and the objectivity of the Ummo supporters: what do they tell you and what do they hide away or are unaware of on the topic of Wolf 424? Which distortions and omissions do they use to "save" Wolf 424?
One thing is terribly sure: what is told in the Ummites letters about their star is, from the point of view of astronomical reality, entirely false.
The type of the errors made in the letters speaking about Wolf 424, and the accumulation of blunders to fix blunders, all that is perfectly compatible with the thesis that the initial letters in question - not necessarily all those which followed, that is another history - were written by the initial prankster. All these errors all are connected to the situation of knowledge and ignorance of this prankster, who unknowingly chose the wrong star while genuinely believing that it was the ideal star.
Some publications in astronomy concerning the observations and studies on Wolf 424 AB, Wolf 424 A, Wolf 424 B:
Note: the majority of these articles are available in entirety - or at least their abstract - on the Internet. To find them, just copy their title into a search engine such as Google.com's input textbox.