The Sun, a UK tabloid, published on 17 August an article titled: A MYSTERY++ object tearing towards Earth at break-neck speed has raised fears that ALIENS are on their way here with these two pictures

That sounds scary, right? What is happening?. Here are the facts.

The “Mystery object” was discovered on 1 July 2025 by ATLAS (Asteroid Terrestrial-impact Last Alert System). ATLAS is a cooperation of earth-based observatories that continuously watch the sky, looking for moving astronomical objects. ATLAS started in 2015 and currently five observatories are taking part. They specialise in looking for smaller asteroids that may impact Earth and can only be detected when they are close. a last alert. Until now they have found 1241 Near-Earth asteroids, of which 110 were potentially hazardous. But also other objects were found, 106 comets and 4847 supernovae (which don’t move but change brightness)

The object found on 1 July is a comet, but it is causing huge excitement in the scientific community because of its extremely high speed. That means it comes from outside our solar system, will be slightly deflected by the Sun, and will escape again. Here is its (hyperbolic) orbit. The (animated) image comes from Wikipedia: 3I/ATLAS

The Wikipedia article contains a massive amount of information about 3I/ATLAS, a proof of the excitement caused by its discovery. Two more pictures from Wikipedia, the original discovery photo (animated gif) and a detailed photo taken by the Hubble telescope on 21 July.

The fuzziness of 3I/ATLAS in the Hubble picture is characteristic of a comet. The icy nucleus is hidden in a coma, water and dust evaporated by the solar radiation. That’s why the present estimate of its size is very inaccurate ( between 0.32 and 5.6 km). The comet will reach its perihelion (closest distance to the Sun) on 29 October and will never come closer to Earth than 209 million km (on 19 December).

Until now, three interstellar visitors have been detected: 1I/’/Oumuamua in 2017, the interstellar comet 2I/Borisov in 2019, and now 3I/ATLAS. In my blog post of February 2018, Oumuamua, I discussed in detail the first interstellar visitor. Now we have another one.

So, why the consternation in the popular press and the social media, like here or here or here. Google for 3I/ATLAS alien and you will find more links.

In my Oumuamua post, I wrote: “Of course, there are people who are wondering if it could be a spaceship”. Basically, it was one man who suggested this, Avi Loeb, an astrophysicist at Harvard University. He was widely criticised by the scientific community. He even wrote a popular science book about it: Extraterrestrial. The consensus is now that Oumuamua is just a physical object.

Avi Laub must have an obsession with alien life. Within weeks of 31/ATLAS’ discovery, he published an article, Is the Interstellar Object 3I/ATLAS Alien Technology? Here is a quote (bold by me):.

As largely a pedagogical exercise, in this paper we present additional analysis into the astrodynamics of 3I/ATLAS, and hypothesize that this object could be technological, and possibly hostile as would be expected from the ‘Dark Forest’ resolution to the ‘Fermi Paradox’

He also has a blog and wrote two posts about 3I/ATLAS, on 17 July and 5 August . And two weeks ago, he was interviewed by FOX 10 Talks. Click on the screenshot to watch the video. The interviewers are in awe that, for the first time, they have a Harvard professor in their program.

When Loeb is right about 3I/ATLAS, that it might be an alien, hostile spacecraft, what about November? Here is a possible scenario.

The spacecraft, disguised as a comet (!), reaches perihelium on 29 October. If you look at the animated GIF above, you will see that Earth is then on the other side of the Sun, so 3i/ATLAS will not be visible to us. During that period, the spacecraft will change its course and when it is visible again, it will come to attack and destroy us!

Just when I was ready to publish this post, I came across this website: Elon Musk: “It’s Confirmed, The 3I ATLAS is an Alien Space Craft!”. I am sure the mention of Musk is fake, only meant to attract more viewers. But the YouTube video on the website is fascinating, a mixture of science and sc-ifi. Click on the screenshot to watch the video.

Don’t worry. It’s a comet, not a disguised alien spacecraft.

Here is a promise. If humanity is still alive after November, I will write a post about the Fermi Paradox and the Dark Forest. And about my solution, the Rare Earth hypothesis.

In April 2016 I published a post Our Solar System, an update. At the end of this post I wrote about the New Horizons mission, that it was on its way to the Kuiper Belt, after a successful flyby of {luto.

Here is the Kuiper Belt, a ring of (mainly) small icy bodies orbiting the sun beyond the orbit of Neptune. The distance scales are in Astronomical Units (AU), where 1 AU is 150 million km. the average distance between Earth and the Sun. The locations of Jupiter, Saturn, Uranus, and Neptune are given. Earth and the other planets are inside the yellow blob in the center. The grey cloud between this blob and Jupiter represents the asteroid belt.

More than 3000 Kuiper Belt Objects (KBOs) have been found and that number is increasing yearly. Many of them are (relatively) small, like, for instance, the 2014 MU69, mentioned in my 2016 post as the next destination for New Horizons. Another flyby on 1 January 2019 was very successful. Here is an image of 2014 MU69, taken by New Horizons. It is a contact binary, dimensions ~40x20x10 km, now renamed Arrokoth. See the appendix about naming (and renaming) objects in the Solar System.

The official name for any object orbiting the Sun beyond Neptune is Trans-Neptunian Object (TNO). Some of them can be quite large. In 2005 Eris was discovered, with a diameter of ~2300 km, about 1/5th of Earth’s diameter, similar in size to Pluto. A heated discussion among astronomers led in 2006 to the demotion of Pluto as a planet and the introduction of a new concept: dwarf planet. Pluto was always an odd one out with its elliptical orbit. It is now a dwarf planet, like Eris. Here is the Outer Solar System.

More dwarf planets have been discovered in the region beyond Neptune. A fascinating one is Sedna, discovered in 2003. Its orbit is extremely elliptical, its distance to the Sun varying between 76 and 937 AU, far outside the Kuiper Belt. One orbit takes 11.400 years, Various estimates for its diameter, Wikipedia gives >1000 km. Here is the orbit of Sedna in orange. The Outer Solar System is now so tiny, the Kuiper belt is marked in blue.

Also shown is the orbit of 2012VP113, in red. Discovered in 2012, diameter ~600 km. Again very elliptical, distance to the Sun between 80 and 460 AU. One orbit takes ~4500 years. You may wonder how astronomers discover such a remote object and even determine some of its properties. In the picture you can see how. Three images, taken by a powerful telescope, with a 30-minute interval, have been superimposed. Look at the small dot in the center. That is 2012VP113, moving against the background of stars

One more extreme TNO, 2015TG387, was discovered in 2015. Its aphelion (the farthest distance from the SUn) is a staggering 2114 AU. The orbital period is about 40.000 years.

More of these extremely elliptical TNOs have been found. What can have been the cause? . Not the giant planets or the Kuiper Belt, they never come close enough to feel their gravitation.

In 2016, two astronomers, Batygin and Brown, came up with an interesting hypothesis. A planet with a mass of about ten times that of Earth, orbiting the Sun in an elliptical orbit between 280 and 1120 AU, orbital period of 5000 years, could explain the orbits. In the diagram, the orbit of this hypothetical Planet Nine is shown.

P[anet Nine has not yet been found and it will not be easy. Not all astronomers are convinced that it exists, but it generated a lot of interest in extreme TNOs.

Recently, a new one has been found 2017 OF201. First observed in 2017. Distance to Sun between  45 and 1630 AU. Orbital period 24.000 years. Here are again three superimposed pictures, this time taken with an interval of 1 hour. Estimated diameter ≈ 550 to 850 km.

In an appendix I will tell more about the interesting way this extreme TNO was discovered and how an estimate could be made about its size. The evidence presented was so convincing that on 21 May TNO 2017 OF201 was accepted by the authoritative International Astronomical Union (IAU) as a new dwarf planet. I flurry of articles in magazines and newspapers followed. Some are accurate, like the EarthSky one, others contain errors, like the Yahoo!News one.

Here the orbit of 2017PF201 is added in red to the other TNOs. The supposed orbit of PLanet 9, here called Planer X, is shown in black.

As you see, the orientation of this new TNO is completely different from the others! And that is a serious challenge for the Planet 9 theory. Model calculations show that Planet 9 would strongly disturb the orbit of 2017 OF201 and, in the future, would kick it out of the solar system. So, does Planet 9 really exist?

That was the ending I had in mind for this post.

But, very recently another interesting article was published, claiming that PLanet 9 may have been found! Click here for the original publication (quite technical). The idea is “simple”. Planet 9 will be cold, but still it emits (thermal) infrared radiation. The authors use data from two infrared missions, IRAS (1983) and Akari (2006), comparing them, filtering out all known infrared sources and looking for an area, that doesn’t move within a few months, the operating time of both missions, but is found in a different location after 23 years. They find one suitable candidate, which fits with the theoretical orbit of Planet 9. Amazing.

I am sure that this is not the end of the story 🙂 .

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Appendix 1 Naming/renaming of astronomical objects in the solar system

All astronomical solar system objects (except comets), smaller than planets, are called minor planets (planetoids). Asteroids, KBOs, TNOs, and dwarf planets. The Minor Planet Center keeps track of them. When a new minor planet has been discovered, it gets a name. For the new dwarf planet, this (provisional) name is 2017 OF₂₀₁. Here is the explanation. 2017 was the year it was first observed. Followed by two letters.

The first letter, O, tells in which half-month of that year it was discovered, in the second half pf JUly 2017. The second letter gives the order of discovery for that half-month. The F would naan that it was the sixth minor planet discovered in that half-month. But wait. When this coding was designed ( in 1925), it could handle 25 discoveries in a half-month, but nowadays, with modern technology, there are many more. That’s why the subscript is added. 201 x 25 = 5025 +8 = 5033. This dwarf planet was the 5033th discovery in the second half of July 2017!

When the orbit is determined accurately enough, this provisional designation is replaced by a (sequential) number. The team that discovered the minor planet can then suggest a name. The minor planet 2014 MU69, visited by New Horizons, is now named 486958 Arrokoth. Using the coding given above, you should be able to check that Arrokoth was the 745th discovery in the second half of June 2014.

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Appendix 2 T The discovery of dwarf planet 2017 OF₂₀₁.

The original article can be found here. The authors use data from the Dark Energy Survey project, which itself is not related to the solar system. To find objects in the solar system, you must look for objects that move. Using the survey data, already ~800 TNOs have been found. The next step is to find the distance of the object. For that we use the apparent motion of the object against the background of the stars. It is called parallax. Due to Earth’s orbit around the Sun, the position of the object changes. From how much it changes, the distance can be calculated. For 2017 OF₂₀₁ this distance is at the moment about 90 AU.

The combined effect of parallax and real motion for 2017 OF₂₀₁ is shown in this diagram

The oval (due to parallax) is moving throughout the years. Observation dates are indicated.

From the amount of light, combined with the distance, a rough estimate can be made of the size. For 2017 OF₂₀₁ this results in a diameter of 550 to 850 km . Big enough to call the object a dwarf planet.

Before you start protesting, we are not talking about the Western (Gregorian) calendar but about the Chinese one 😉 .

In the Western calendar, a year has 365 days, but one orbit of Earth around the Sun takes 365.25 days, 6 hours more! To compensate for this shortage, an extra day is added (29 February), when the year is divisible by 4. As 2025 is not divisible by 4, it is NOT a leap year. Have a look at Appendix* f for more details.

MoonThe Chinese calendar is a lunar calendar, based on the orbit of the Moon around the Earth. One orbit takes on average 29.53 days. Therefore, a lunar year is 12 x 29.53 = 354.36 days, 11-12 days shorter than the solar year.

As a result the lunar year moves forward 11-12 days yearly with respect to the solar year. The Islamic calendar is doing that.

Does that matter? It depends, for an agricultural society it does, because a lunar calendar has no relation with the seasons.

The solar year has seasons because the Earth’s axis is tilted. Here is a diagram. There are two times when the Sun is right above the equator. Day and night are of equal length all over the world. They are called the Spring equinox (~ 21 March) and the Autumnal equinox (~21 September). Around 21 June, the Sun reaches its northernmost position, the Summer Solstice, when daylight is at its maximum in the Northern hemisphere. Half a year later, the daylight is minimal. around 21 December, the Winter Solstice. (Of course in the Southern hemisphere it is just the other way around).

I wrote “around” and in the diagram a few dates are mentioned. In Appendix 2 I will explain why the dates vary, although the events are fixed.

Another way to describe the location of the Sun, is by using degrees (ecliptic longitude is the technical term).. We start at the Spring equinox (0°), and go counterclockwise. Then the Summer solstice is at 90°, the Autumnal equinox at 180°, and the Winter solstice at 270°.

Can we also divide the solar year in months? Sure, by dividing the Sun’s orbit in 12 sectors, each of 30 degrees. Each sector corresponds to a solar month. It is what the Chinese solar calendar does. It introduces 24 Solar Terms, two for each month, one for the start and one for the center. It is called the Center Point of that month. (similar to a Full Moon day in the lunar calendar). Here is a diagram of the 24 Solar Terms.

The diagram contains lots of information, the names of the solar terms (in English and Chinese) and the approximate dates. When you are Chinese, you may find a few familiar names: Qing Ming (15°), Dhong Zhi (270°) and Li Chun (315°). More about this in Appendix 3.

To explain the lunisolar calendar, we need the dates for the lunar and the solar months. Lunar data( for the years 2005-2045) can be found here and the Solar Terms (for the years 1900-2049) are here.

Here is the info for the first lunar month in 2025. The link above gives 29 January at 20:35 for the New Moon. So, the first month of CNY starts at 29 Januarty. The next New Moon is at 28 February, so the last day of the first month is 27 February.

The Solar calendar starts with Li Chun (the beginning of Spring). Using the Solar Terms link above, we find the date for that solar term: 3 February at 22:10, so the first solar month starts on 3 February. The next solar term (Rain Water) is at 18 February 18:-0, so tne Center Point is on 18 February. I have collected the results in the table below. The first lunar month contains the first solar center point.

I have done the same for the next two lunar months.More or less the same but the Solar Center Point shifts to more the end of the lunar month (8 resp. 7 days). That makes sense because a solar month is slightly longer than a lunar month.

Here are the other months for 2025. Notice the month I have given a blue color.

As you see there is a lunar month that doesn’t contain a solar center point!. When that happens, that month is considered a leap month. It just duplicates the earlier month. The result is that a lunisolar leap year contains 13 lunar months.

Notice how after the leap month the solar center point is at the beginning of the lunar month. Each lunar month it will advance 1-2 days, so after 2-3 years there will be another leap month. Not necessarily the sixth month, like this year. See Appendix 4.

In the Chinese lunisolar calendar, a lunar month is a leap month when it does NOT contain a solar center point.

Appendix 1 About a leap year in the Gregorian Calendar

A leap day is added when the year is divisible by 4. This makes the length of a year 365 + 1/4 = 365.25 days. But the solar year is actually 365.2422 days, slightly less. Therefore, the Gregorian calendar has a second rule: when the year is divisible by 100, it is NOT a leap year; This makes the average year length 365 +1/4 -1/100 = 365.244 days. A better approximation, but it can be made even better by a third rule: when the year is divisible by 400, it IS a leap year; making the average year length 365 + ¹⁄₄ − ¹⁄₁₀₀ + ¹⁄₄₀₀ = 365.2425 days. More information about leap years can be found here.

Appendix 2: Why do the dates for solar terms vary, while the events are fixed.

Because a normal year is 6 hours short of a solar year, the solar terms will shift 6 hours! Take for example Li Chun. In 2025 it falls on 3 Fberuary at 22:10, but in 2026 on 4 February at 4:02. Six hours later, so next year Li Chun will fall on 4 February. Another cause of variability is the time zone system we are using on Earth. All dates and times in this post are in China/Malaysia time (UTC + 8). in that timezone the Summer Solstice falls in 2025 on 21 June at 2:42. New York is using Eastern Time (UTC-4), the Summer Solstice in that timezone is 12 hours earlier and falls on 20 June 22:42, one day earlier.

Appendix 3 About Dong Zi, Qing Ming and Li Chun

The Chinese festivalls follow the Lunar calendar , with three exceptions. Around Qing Ming (Cheng Beng) Chinese families visite the graves of their ancestors. `And around Dong Zhi, Chinese celebrate the harmony in the family. Li Chun is of special imporatnce for the believers in Feng shui. All three belong to the solar calendar, they don’t move around.

Appendix 4: How to find a leap month

You don’t need mathematics to find a leap month, just the tables for moon phases and solar terms as given above. Solar Center Points advance relative to lunar months, so we must find a lunar month where the Solar Center point falls on the first day of that month. We have to continue until 2028 before we find a month that fits that condition. Here is the relevant part of the table for 2028

I2028 will be a leap year, the 5th month will be duplicated.

In 1995 NASA published this picture, taken by the Hubble Space Telescope. It shows a small part of the Eagle Nebula and became instantly famous. Because in the “pillars” stars are born, the picture got the name “Pillars of Creation”.

The Hubble Space Telescope was launched in 1990 and is still operating, with quite a few Space Shuttle service missions. To celebrate its 25th anniversary, a new picture of the Pillars of Creation was published in 2015. With a new camera installed, more details are visible,

At the same time this picture was published, an infrared picture of the Pillars. Infrared light can travel more easily through dust and clouds and that is why now you see stars in the pillars, where young stars are still being formed. But I hope you wonder how this can be an infrared picture as infrared light is invisible light. The explanation will be the main part of this post.

But first here are two pictures, recently taken by the James Webb Space Telescope. The JWST is an infrared telescope has and has two cameras on board to take pictures. The NIRCAM for near infrared light and the MIRI for medium infrared light. Here is the NIRCAM photo

And here is the image from MIRI, Amazingly different. And again, how can these be infrared pictures’?

Time to give some explanation about the pictures and also about the Eagle Nebula, where the Pillars of Creation are located.

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About visible and invisible light

Light is an electromagnetic wave, as are microwaves, radio waves, X-rays etc, They all have different wavelengths. The wavelengths of visible light are often given in nanometers (nm), where 1 nm is 1/billionth meter. Or in micrometer (μm) where 1 μm = 1000 nm. The human eye is sensitive to wavelengths between ~380 and ~750 nanometer and sees the various wavelengths as different colors! The longest wavelengths are seen as red, the shortest as purple/blue with all the “rainbow” colors in between.. In this diagram the electromagnetic spectrum is shown. The infrared part can be subdivided in near infrared, mid infrared and far infrared

The Hubble telescope has two cameras onboard. Most of the iconic Hubble pictures have been taken by the Wide Field Camera. The present wide field camera (WFC3) can take photos in two channels, one for ultraviolet and visible light (UVIS) and the other one for near infrared (NIR), The range of UVIS is 200-1000 nm and of the NIR 800-1700 nm

The James Webb has two cameras, the NIRCAM for the near Infrared, range 600-5000 nm and the MIRI for the mid Iinfrared, range 5000-28000 nm (5 μm -28 μm).

Before we describe in some detail how digital cameras record images, it is useful to have a look at the way the human eye sees colors.

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How does the human eye see colors?

The retina of the human eye contains about 6 million nerve cells, called cones. These cones come in three different types, S, M and L, sensitive to various parts of the spectrum. The S type cones are sensitive to the blue part of the spectrum and are also often called Blue cones, In the same way the other two are often called Green and Red.

The brain is able to combine the response of these RGB- cells. For some people the M and/or L cone cells are not working properly. As a result they are colorblind.

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How does a digital camera record colors?

Digital cameras have sensors consisting of millions of individual pixels that record the intensity of the incoming light, basically in a gray scale (black and white). That these cameras can take color pictures is because in front of the sensor there is a color filter, consisting of a mosaic of millions of red, green and blue “pixels”. A so-called Bayer filter. See the diagram below. Taking a picture, means actually taking a red, green and blue picture at the same time, but these pictures are “incomplete”. By mathematical techniques (interpolation) the full color pictures are constructed.

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Here is an example, where three images, in red, green and blue, when combined, give the full image in natural colors.

The sensors in space telescopes do not have these Bayer filters, they just record the image in gray scales. However, various filters can be placed in front of the sensor and multiple images can be taken of the same object. For example, the Hubble WFC3 camera has a huge choice of filters, 47 for the UVIS channel and 14 for the IR channel.

Why so many? Some filters are broadband, they pass a wide range of wavelengths. From a scientific point of vew the narrowband filters are interesting because they pass only the light emitted by specific elements. Here is one example, hydrogen (H) emits red light with a very specific wavelength of 656 nm. So one of the filters only passes wavelengths around that value and a picture taken with this filter shows the presence of hydrogen. Similar filters can be used to check the presence of oxygen (O), sulphur (S) etc.

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The Pillars of Creation pictures are “false-color” pictures!

On 1 April 1995, astrophysicists Jeff Hester and Paul Scowen published an article The Eagle Nebula, in which they showed a picture of the Pillars of Creation. If you think that was “just” a picture taken by the Hubble telescope, you are seriously mistaken. The PBS/NOVA website More than just a pretty picture explains in 19(!) webpages how the iconic photo was created. Very readable,

The WFC2 consisted actually of four cameras, each recording a quadrant. The top-right quadrant camera was slightly different, zooming to show more details. Resizing it to the format of the other three, causes the characteristic Hubble image with the “steps” in one corner. Here is the original image of this top right quadrant, in gray scales. What a mess. For an explanation how to clean this image, see the website. The second image shows the result of the various cleaning operations. What a difference !

We can do the same for the other quadrants.

Now we can “glue” the four parts together. You can still see a bit the seams between the four images.

For this mage a filter was used that only let blue-green light through from (doubly ionised) Oxygen atoms (OIII). Two more filters were used to create images in the same way. One filter let only the reddish light from Hydrogen atoms through (Ha), the other one selected reddish(!) light from ionised Sulphur atoms SII). Three narrowband filters, two of them in the same color range.

Here are the three filtered images

You might expect that the next step would be to give these image’s color corresponding to the filter used for each of them. The Ha and SII reddish and the OIII one greenish. But that is NOT what Hester and Scowen did. They assigned the RGB colors to the three images. Blue to the OIII image, Green tot the Ha image and Red to the SII image.

Final step is to combine them: the Pillars of Creation.

The main reason to assign “false colors” to the pictures is to enhance the contrast and to see how the various elements are distributed. Almost all Hubble photos are false color (also called pseudo color). Using the three narrowband filters for S, H and O and assigning them to RGB is so common that it is often called the Hubble Palette. Doing a Google image search for Hubble Palette gives a huge number of hits. Here is a part.

Other combinations of narrowband filters are also used. Here is an example where 6 filters have been used for the Butterfly Nebula. Besides SII, Ha and OIII, also ionised nitrogen, helium and oxygen. In the table the natural colors are given and also the colors assigned in the Hubble palette.

An American astrophotographer got curious how this nebula would look in the natural colors. Here are two images’, left the false color one and right the picture in natural colors. It is clear that the artificial image reveals many more details

It must be clear now that while with the Hubble telescope you have a choice to use false colors, with the JWST there is no other option, as infrared light is not visible. Here are the filters used for the MIRI camera. The colors suggested for the various infrared ranges are not significant, just to guide the eye.

For the MIRI picture three filters were used, F770W, F1130W and F1500W. In the above diagram I have marked them. For this picture they are assigned Blue, Green and Red respectively.

The NIRCam camera has many more filters, broadband, narrowband etc.

For the NIRCam picture 6 filters have been used, marked in the diagram above.

I have read somewhere that creating these images should be considered as art and I agree.

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The Eagle Nebula

Finally a few remarks about the Eagle Nebula. When massive stars die, they can “explode” as a supernova, erupting their remnants into space. In these clouds of dust and various elements, new stars can be formed. The Eagle Nebula is such a cloud, here is a picture taken by an astrophotographer, using a telescope and a DSLR camera! Many of the bright spots in this picture are young stars already formed in the cloud. These stars are so hot that they emit UV light and even X-rays. This radiation can has enough energy to ionize the cloud. Such a cloud is called an emission nebula. The dominant reddish color is caused by hydrogen

The Eagle nebula is located about 7000 lightyear away and is huge, roughly 70 x 55 lightyear. It is a young nebula, estimated age is 5.5 million year. It is also a temporary event, the forming of new stars still continues and the radiation those stars will erode the nebula.

In the center of the above image, you can see the pillars of creation.Here is a dteail. Comapre it with the images of Hubble and Webb. Even these pillars are huge, the logext one is about 4 lightyear long.

A final remark. From the Hubble and Webb picture you might think that the pillars are almost like rock, impenetrable. But this is not true at all. The density of nebulas varies between 100 – 1 million particles per cubic cm. A high vacuum on earth still has considerably more particles per cubic cm. It is just the huge size that makes the pillars look like solid.