Where does the Moon come from?

Posted on August 13, 2014 by janstu

Last week it was full moon, and not just an ordinary one, but a perigee full moon, often popularly called a “Super Moon”. The orbit of the moon around the earth is elliptical, so the distance between moon and earth varies between 363.104 km (perigee) and 406.696 km (apogee). When a full moon occurs at perigee, the moon looks larger and brighter. It’s not a rare phenomenon, 9 September this year will be the next perigee full moon, and June 2013 there was another one. It’s a bit of a media hype.

My friend Chuan took a beautiful picture of this perigee full moon, in the middle of the night, with his point and shoot camera(!), handheld, 24x zoom.

The dark regions are called Mare (Sea) because in the past people believed that there was water on the moon. Actually they are basaltic plains, formed by ancient volcanic eruptions. Huge craters mark the places where meteorites have hit the moon. Here is a map of the moon with the names of craters and seas.

We can see only one side of the moon because the moon is “tidally locked” to the earth, always showing the same face to us. This interesting phenomenon deserves a separate post..:-) So how does the other (“dark”) side of the moon look like? It’s only after the start of the space age that we were able to explore. With a surprising result. Here is the other side of the moon

A lot of craters, but no “seas”. Why so different? Which leads to another, more basic question, where does the moon come from? Was it “born” at the same time as the sun and the other planets, ~4.5 billion years ago? Many hypotheses have been formulated, here is the theory that is generally accepted at the moment. It is called the Giant Impact Hypothesis

Not long after the formation of the solar system, there was another planet, about the size of Mars, which collided with the (young) Earth. Here is an artist impression of this collision.

This hypothetical planet has been named Theia, after a Greek goddess, the mother of Selene, the goddess of the moon. The effect of this dramatic collision was that a large part of Theia and Gaia, as the young Earth is sometimes called, melted together, forming the present Earth, but another part of Gaia and Theia was thrown out during the collision and coalesced into the Moon.

So powerful was this collision that the new Moon and probably also part of the Earth consisted of molten magma. The Moon, being smaller, cooled faster, and because of the heat of Earth and the tidal locking, the near side of the moon got a thinner crust than the far side! According to this theory that might be the reason that the near side has had more volcanic activity than the far side. There are many more arguments in favour of this giant impact hypothesis.

Of course the next question is then, where did Theia herself come from? A very promising idea is that this planet might have been formed in about the same orbit as Gaia. In 1772(!) the French mathematician Lagrange studied the properties of rotating systems, like the earth orbiting the sun. He discovered that there exist points in such a system, where other objects can exist in a stable way. There are five such points, nowadays called Lagrange points

In the Lagrange points L4 and L5 the gravitational force of Sun and Earth balance in such a way, that objects will corotate with Earth around the Sun. During the formation of the solar system, mass could have accumulated in for example L5 and formed Theia. Through the disturbance by other planets (Venus for example), this planet could, after millions of years, leave L5 and collide with Earth.

Just skip this last part if you find it too complicated…:-)

Rosetta meets 67P

Posted on August 6, 2014 by janstu

In January I have published a post about the Rosetta spacecraft, launched in 2004 with as destination a comet, the 67P/Tsjoerjoemov-Gerasimenko. It had gone in hibernation in June 2011 and on 20-1-2014 it woke up again.

In the past six months the spacecraft has been coming closer to the comet while its thrusters have slowed it down in a number of carefully planned maneuvers.

Today (6-8-2014) was another critical moment. In a thrust of more than 6 minutes, the spacecraft should reduce its speed relative to the comet to about 1 m/s, while at a distance of ~ 100 km away from 67P.

It has been confirmed that the operation was successful. Mind you, the comet and Rosetta are at the moment moving between Mars and Jupiter, on their way to the Sun. The distance to earth is about 400 million km, so signals between Rosetta and Earth take more than 20 minutes!

Check this fascinating link to follow Rosetta in its complicated trajectory, from the start in 2004 until the end of the mission in 2015: Where is Rosetta

As Rosetta is now close to the comet its on board camera has taken pictures of the comet. Here is one, taken three days ago. An amazing picture. The comet has already been nicknamed “rubber duck”. A “binary” comet, consisting of two parts! And it doesn’t look like a “dirty snowball” at all. To say that the scientists are excited, would be an understatement..:-)

Here is another interesting picture, superimposing the comet on the city of London, to give an impression of its size.

What will happen next? Rosetta will follow a complicated triangular trajectory the coming weeks (using again its thrusters) to test and explore the gravitational field of the comet. Here is a YouTube of its proposed trajectory. Almost like an abstract ballet..:-).

The sudden orbital changes are caused by the thrusters, the curvature by the gravitational field of the comet. The complicated shape of the comet may make it more difficult to determine its gravitational field. Finally Rosetta will settle down in a stable orbit around the comet, maybe as close at 10 km, and then, in November, it will launch its small probe Philae, to make a soft landing on the comet.

That will become another update…:-)

For more information, follow the very informative Blog of Rosetta

Wake up, Rosetta!

Posted on January 19, 2014 by janstu

Almost ten years ago, in March 2004, the European Space Agency (ESA) launched a spacecraft with an ambitious mission: to orbit and land on a comet. The spacecraft was called Rosetta. Once in orbit around the comet, a small probe, called Philae, would be launched to make a soft landing on the comet. In this artist impression you see Rosetta in orbit and Philae on its way down to the comet.

Destination of Rosetta is the comet 67P/Churyumov–Gerasimenko This “dirty snowball” as comets are sometimes called, was discovered in 1969. It has a diameter of 4 km and orbits the Sun with a period of 6.45 year. Comet orbits are very elliptical, when they are close to the sun, some of the comet material evaporates and gives rise to the famous comet tail. At the moment this comet is on its way to the Sun, reaching its closest distance (perihelion) in August 2015. Here is a model of the comet nucleus, generated from images taken by the Hubble telescope.

If everything goes as planned Rosetta will reach comet 67P/Churyumov–Gerasimenko in May 2014. A few months later, in November 2014, the probe will land on the surface of the comet. End of mission in December 2015.

Why does it take so long to reach the comet? Have a look at this diagram, where you see the orbit of the comet (red), the orbits of Earth and Mars (green and blue) and the flight path of Rosetta (dashed line).

The reason for the complicated flight path is that it is not feasible to give the spacecraft enough speed at launch to reach its target. To give the spacecraft its required speed, one or more so-called gravitational slingshots are needed.The principle is this: steer the spacecraft close to a planet or moon. Because these objects have their own (high) speed, the force of gravitation can give extra speed to the spacecraft. A simple analogy can be found in sports. When a ball hits a stationary held tennis racket, the speed of the ball will basically remain the same (only reversed). But when the player moves the racket towards the ball, the ball will bounce back with a much higher speed.

Rosetta has used four of these slingshots, marked in the diagram above Three times with Earth (2,4,6) and once with Mars (3). Imagine how accurately the scientists have to steer!

Actually they did it in a clever way so there were a few bonuses..:-) The second slingshot by Earth (4) was performed in such a way that the path of Rosetta would cross the path of an asteroid, Steins, on 5 September 2008! Perfect to test if all equipment was still working correctly. Here is an image of this rather small (diameter ~ 6 km) asteroid, taken by Rosetta during the fly-by (5 in the diagram). Closest distance between the two ~ 800 km, distance from the Sun more than 300 million km. Amazing.

The last slingshot brought Rosetta in a very elliptical orbit, similar to the target comet. This is necessary because the spacecraft must approach the comet with a low relative speed, otherwise it can not go into orbit around the comet

Again a bonus, a spectacular one. The path of Rosetta crossed the orbit of another asteroid, a big one (diameter ~ 120 km), called Lutetia. Here is a picture. Asteroids are as old as the solar system, what an inferno it must have been in the beginning, noticing the surface pockmarked with craters.

The very elliptical orbit of Rosetta after the last slingshot, means that it is moving very far from the Sun. And it depends on the Sun for it uses solar power. The engineers came with an ingenious solution, they let Rosetta go into hibernation!

On 9 June 2011, they sent a signal to Rosetta to switch off all instruments, keeping only the main computer and some heating alive, and starting a timer. It worked, because from then on the spacecraft did not send any signals.

For more than two and a half years there has been no communication with Rosetta! The timer has been programmed to give Rosetta a wake up call on 20-1-2014 at 10.00 GMT. The wake up process will take many hours. The controlled spinning has to be stopped, the antenna has to be pointed to earth etc, etc. It is expected that the first signal should reach Earth around 17:30-18:30 GMT (Malaysia time is GMT + 8 hours).

You can follow the events on Monday 20-1-2014 via live streaming (starts 9:15 GMT):

More information can be found on the ESA Wake Up Rosetta page. They have done a good publicity job. For example they have organised a Wake Up Rosetta competition for the general public. You can create a video and submit it (until tomorrow). Here is the Facebook page where you can view the contributions. And vote for your favourite!

Tomorrow will be a nerve-wrecking and nail-biting day for many scientists!

UPDATE 21-1-2014

Rosetta has woken up! Yesterday at 18:20 GMT a big applause started in the ESA control room, when a spike appeared in the spectrum analyser. It was the first signal from Rosetta, which had traveled for 45 minutes to reach Earth, 800 million km away.. In Malaysia it was already 2:20 am but I could not sleep, had to watch…:-) Here are two screenshots from the live blog

This was a sign of life, next step will be to receive a health report. What a brilliant achievement.

Another update

A friend sent me a link to an ESA webpage: Where is Rosetta An animation of the path of Rosetta through the Solar System. Breathtakingly beautiful. You can zoom in and out, tilt, etc. The page takes time to load, but really worth the effort !

Our Sun again

Posted on November 13, 2013 by janstu

It is almost one year ago that I gave you an update about the Solar Sunspot Cycle 24. For those who have not read those earlier posts, a short recapitulation.

Sunspots are dark spots on the surface of the Sun and related to the sun’s magnetic structure. It is a periodic phenomenon, sometimes there are many, sometimes there are almost none at all. The period is about 11-12 years, and one such a period is called a Sunspot Cycle.

This periodic behaviour was discovered in 1843 by Schwabe, a German astronomer. Rather arbitrarily a numbering was introduced, with cycle 1 lasting from 1755 until 1766. We are now at the maximum of cycle 24. In the picture below the ‘average’ number of sunspots is shown as a function of time, for cycle 23 and 24, updated until November 2013

As you see, the maximum is considerably lower than the maximum of cycle 23. And that is the reason that I have published my earlier posts, for example Don’t worry, our Sun is not dead. You can read more background information there.

Here is a graph showing you the large variation in these sunspot maxima during the last 500 years. In the last 50 years the sunspot activity has been unusually high, whereas in the second half of the 17th century there was hardly any activity at all. This period is called the Maunder Minimum, whereas the last 50 years are sometimes called the Modern Maximum. Another period of low activity occurred in the beginning of the 19th century: the Dalton Minimum.

So now the burning question is: are we on our way to a new minimum

The picture above I have used already in my post, one year ago, How is the Sun doing these days? At that time the prediction was that the maximum would be about 76 and I had marked this maximum with a red cross, comparing it with the low value of 64 in 1906. Now, one year later, we have reached the maximum and it is even lower than predicted, ~ 65 (red circle). Although it is a bit early, a few predictions have been made already for cycle 25, which will peak around 2024. Peak may not be the right word, because the maximum might be as low as 7!

If we are going to a new minimum, will it be Dalton-like or Maunder-like? No one can tell at this moment. We do not really understand much of the underlying mechanism. When we study the Sun in visible light, it looks peaceful, with occasionally a few spots..:-). But look at the Sun in the ultraviolet region, and you see how violent it is.

Is there a relation between the periods of large/small solar activity and the climate on Earth? During the Maunder Minimum we had the Little Ice Age. Is the Global Warming fully due to the hothouse effect of carbon dioxide, or has the Modern Maximum also its influence? This is a sensitive topic, that I will not touch. The next decade we will hopefully learn more.

For more information, here is a very readable article in Sky and Telescope (published already two years ago): Is the Sunspot Cycle About to Stop?

Physics Nobel Prize (2011)

Posted on July 14, 2013 by janstu

The Nobel Prize for Physics in 2011?

But that is long ago, the Nobel Prize 2012 has already been awarded and in October the winners of the 2013 prize will be known!

Yes, this post is long overdue, I know 🙂 Every year I am interested, being a physicist myself, who will get the Nobel Prize for physics and for what . And nowadays often I have no idea what it is about :-(, being out of touch with the modern developments for so long already. So I was quite happy that I understood the importance of the discovery made by Perlmutter, Schmidt and Riess in 1998 that our Universe is expanding at an accelerated rate.

From left to right, Perlmutter, Schmidt and Riess

Of course you have heard about the Big Bang, the primordial explosion that created the Universe, about 14 billion year ago. As a result of this explosion the Universe is expanding and also cooling down. Proof: when we look at faraway galaxies, we observe that they are moving away from us and each other, the farther away the faster they move. And in 1965 the Cosmic Background Radiation was discovered, proof of the cooling down of the Universe.

When I was doing my PhD research, in the seventies, the Big Bang theory was widely accepted. And also that the rate of expansion should decrease with time because of the mutual gravitational attraction between all matter in the Universe. If the Universe contained enough mass, the expansion would finally stop, followed by contraction and ending in what became known as the “Big Crunch” where the whole Universe would again be concentrated in a single point. And might even start again in another Big Bang! An attractive idea in those hippie days!

Here are the possible scenarios. In the coasting scenario there is not enough mass to stop the expansion, in the middle one there is just enough mass to stop it (asymptotically), but not enough to reverse the process (as in the left scenario)

The problem was that when you counted all the visible mass in the Universe, there was just not enough to stop the expansion. It was named the “missing mass problem”.

Would it be possible to determine experimentally which scenarios was the correct one? To measure the rate of expansion, you should measure the velocity of very faraway galaxies. Measuring the velocity is not that difficult, you have to measure the Doppler shift. When an ambulance passes you, you will first hear a higher sound of the siren, and a lower sound when the ambulance is moving away from you. For light it is basically the same, here you will see a difference in colour. When a star or galaxy is approaching is, the colour is a bit bluer, when it moves away it will be redder. Measuring the “redshift” gives us the velocity.

The big problem is how to determine the distance to such a faraway galaxy! The technique used in astronomy is based on the fact that light from a light source becomes more spread out when the distance is larger. Probably every photographer is aware of this “inverse-square law”

So if you know how “strong” the light source itself is, you can determine the distance by measuring the amount of light at that distance. But how do we know how much light a star really produces? In general that is impossible, because you have big bright stars and small, not so bright stars.

What the Nobel Prize winners did was looking at very special events, so-called (type 1A) supernova’s. A supernova is a star that explodes at the end of its life. During a few days/weeks it can produce more light than a whole galaxy. And the intensity of this light is basically the same for each supernova explosion (of type 1A). They are extremely rare events, it is estimated that in our own Milky Way they occur only a few times in a century! But when they occur, they are so bright that they can even be observed in very distant galaxies. And there are so many galaxies.

Finally we can now explain the research done by the (competing) teams of Perlmutter and Schmidt & Riess. They looked for type 1A supernovas in distant galaxies and determined the distance and the velocity. To show you how complicated this kind of research is, here is an image of a recent supernova discovery, SN Wilson. In this image a few bright points are stars, but many are galaxies. The tiny square contains the galaxy with the supernova.

Here are three enlarged images of this tiny square. The galaxy is the round spot in the center. Left image shows the situation before the supernova exploded, in the middle one the supernova has exploded. You don’t see any difference? Let the computer “Subtract” the left image from the middle one and you get the image to the right! Voila, the supernova ..:-)!

These images, taken by the Hubble telescope were taken by the team of Riess in 2010. The distance is 10 billion light year, which makes this galaxy the most distant one, observed until now.

As the light of this galaxy needed 10 billion years to reach us, we observe it now as it was 10 billion years ago! Looking far away means looking in the past. The scientists expected to find that in the past the expansion of the universe would be faster than it is now, as explained in the beginning of this post.

What they actually found, shocked the scientific world: the expansion of the Universe was accelerating . It was so unexpected that it was very fortunate that two research teams came to the same conclusion.

So there had to be a repulsive force, stronger than the attractive force of gravitation. This repulsive force is now named “dark energy” but we still have no clear idea what it is.

It is for this discovery that the two teams shared the Nobel Prize.

The three scenarios, mentioned above are all wrong. It is the fourth scenario, shown below, that we now believe to be correct. There is even a possibility that this acceleration will increase so dramatically with time, that the Universe would end in a Big Rip, where finally, stars, planets, even atoms would be ripped apart.

Much progress has been made since 1998, especially in the analysis of the Cosmic Background Radiation. It has confirmed that there is a repulsive force, now named “dark energy”. It has also confirmed that there is a lot of invisible matter in the Universe, now called “dark matter”. In both names “dark” describes our ignorance, at the moment we just do not know what they are. I am planning to write a separate post another time about this topic.

Let me end this post with an image that gives the distribution of “normal” matter, dark matter and dark energy in our Universe. I have seen this kind of picture numerous times, and I still find it shocking.

The stars, the planets, humans, everything is made of normal matter: protons, neutrons, electrons. We know a lot about it. But it is only 4% of our Universe. About the other 22+74 % we know next to nothing at the moment!

If I could start a new life now, I would choose astrophysics and cosmology as my field of study…:-)

Several images above have been taken from this very interesting set of lecture notes.

Visitors from outer space

Posted on April 5, 2013 by janstu

15 February 2013: A small asteroid enters the Earth atmosphere over Russia. Mass ~11.000 tonnes, size ~20 m and speed ~18 km/s. At an altitude between 15-25 km it explodes, causing a shock wave on the ground resulting in about 1500 people hurt (mostly by scattered glass) and ~ 7000 buildings damaged. Estimated energy 440 kilotons of TNT, equivalent to ~25 times the energy of the atomic bomb on Hiroshima, most of it absorbed in the atmosphere. This asteroid had not been discovered before its impact.

On the same day about 15 hours later, asteroid 2012 DA₁₄ passes Earth at a distance of only 28.000 km (that is within the orbit of the telecommunication satellites!). Bigger (about 40.000 tonnes and 30 m), it was discovered in February 2012. Although occurring almost simultaneously, the two events are not related.

Next year, 19-10-2014, comet C/2013 A1 will pass extremely close to Mars, with a small possibility of an impact with the planet. Here we are talking about a different order of magnitude! Estimated size of the comet nucleus is ~ 3km! IF it would hit Mars, the energy released would be in the order of millions of Megatons of TNT. For comparison, the asteroid that struck Earth 65 million years ago and ended the dinosaur era on Earth was only about three times as powerful.

Do we have to get worried? In the aftermath of the Chelyabinsk meteor there was a lot of commotion in the media that action should be taken immediately to protect us from future collisions. Suggesting that nobody had expected this. As if the scientific world was not already aware of this problem!

Those outer space objects (asteroids, meteorites, comets) that can come close to (or even hit) Earth are called Near Earth Objects (NEO’s). Because of the impact risk they are monitored already for decades. The problem is that there are many of them and that they come in all sizes. Here is a graph of their distribution. The blue line gives the number of known NEO’s, the red line is a estimate of their total number. Please note the double logarithmic scale of the graph! For example, only about 100 NEO’s with a size of ~10 meter have been observed, whereas the estimated total number is ~ 10 million!

At the moment about 10.000 Near-Earth objects have been discovered. About 900 of them are asteroids with a size of 1 km or larger.

Here is a table with (statistical) information about the impact of a NEO. The second row gives data for objects with a size of 30 meter. The 2012 DA14 falls in this category. The effect of impact: a fireball, a shock wave and minor damage. Fits quite well the Chelyabinsk meteor, although it was smaller. The second column gives the average time in years between impacts of this size: 300 year.

If comet C/2013 A1 would have been on a (near) collision course with Earth, it would fall in the category: Billions of people dead, global climate change. Time interval: millions of years.

Followers of my blog may remember the post about Apophis At the time of discovery there was worry that it might hit Earth. We know now that the probability of impact is negligible. With its estimated size of 300 m it would create havoc, but no global destruction.

If a NEO on collision course is discovered early enough, it may be possible to deflect it. Numerous proposals exist. See my post Paintballing Apophis or do a Google search on “deflecting a NEO”

Conclusion: Earth runs a risk of an impact with a NEO. It is not a matter of IF but of WHEN. Early observation of “dangerous” NEO’s is important, so protecting measures can be taken. That is why there are global initiatives, like for example NEOShield

For this post graphs, tables etc have been taken from this very informative site.

Largest structure in the Universe discovered

Posted on January 29, 2013 by janstu

This will be a bit longish post…:-)

A few weeks ago an in international team of astronomers announced the discovery of the largest structure in the universe: a group of quasars extending over a distance of 4 billion lightyear (ly).

Quasars (Quasi-Stellar Radio Objects) were discovered about 50 years ago. They look like stars but are so distant (billions of ly away) that they can not be stars. Now we know that they are active nuclei of galaxies, surrounding a massive black hole in the center. Billions of ly away means that we observe them as they were billions of years ago when the universe was still young.

More than 200.000 quasars are known at present. Some of them occur in (large) groups, called LQC‘s.The group that has now been discovered has 72 members (the black circles in the image). The red crosses form another, smaller group.

So, why is the discovery of this large group of quasars so exciting? To make that clear, we have to talk about the cosmological principle and the large-scale structure of the universe.

Long it has been thought that the Earth was the center of the Universe. Then it was discovered that Earth is one of several planets orbiting a star, the Sun. It is the blue marble in the image below. It is not in scale, light needs only 8 minutes to travel from the Sun to Earth, and more than four hours to reach the outermost planet Neptune.

Is the Sun the center of the Universe? No, the Sun is one of several hundreds of billions of stars in our galaxy, the Milky Way. Some of you may have seen the Milky Way on a cloudless clear night far away from cities, as a white band of light across the sky. Here is an artist impression of the Milky Way as seen by an observer from outer space. The approximate location of our Sun has been indicated with a red cross. The diameter of the Milky Way is about 100.000 ly.

Is then the Milky Way the center of the Universe? Again negative! Our Milky Way is just one of hundreds of billions of similar galaxies. The scientists now think that the Universe has no center! From each location and in each direction the Universe looks the same, if you observe it on a sufficiently large scale. This is called the Cosmological Principle

So, what is a sufficiently large scale? If the galaxies would be randomly distributed in the Universe, we would not need to zoom out further. But that is not the case! Our Milky Way is a member of a group of more than 50 galaxies, bound by gravity. It is called the Local Group. Most of the galaxies in this Local Group are small ones, with the exception of our neighbour, the beautiful Andromeda galaxy.

Andromeda is bigger than the Milky Way, may contain one trillion stars and is located at a distance of 2.5 million light-years from our galaxy. Here is a “3-dimensional” sketch of the local group.

The size of the Local Group is in the order of 10 million ly. Many more of these galaxy clusters exist, for example the Virgo Cluster, much bigger than our Local Group, consisting of more than 1000 galaxies, at a distance of 54 million ly.

Here is the Virgo Cluster. All the fuzzy blobs are galaxies, the light points are stars in our own Milky Way. Click on the image to enlarge it and take a few minutes to think about the meaning of life..:-)

We still have to zoom further out. Our Local Group, the Virgo Cluster, the Fornax cluster, the Eridanus cluster and about 100 more are part of an even larger collection, the Virgo Supercluster . Here is one more “3-dimensional” sketch of this supercluster.

You will see the Local Group in the center, the Fornax and Eridanus clusters and many more. We are talking now about a size of more than 100 million ly already!

Many more superclusters have been discovered. Could it be that these superclusters of galaxies are randomly distributed in the Universe. Let’s zoom out one more time! The image below shows the superclusters around us within a distance of 1 billion ly. So the width of this image is 2000 million ly.

Obviously this is not a random distribution. Clusters and superclusters are aligned along filaments filaments, with in between large portions of space almost without any galaxies. It looks like a kind of foam-like structure and is sometimes called the Cosmic Web. In the center you notice the Virgo supercluster. Keep in mind the zooming out steps we have made to reach here! Earth → Sol → Milky Way → Local Group → Virgo Cluster → Virgo Supercluster → Cosmic Web.

Do we need to zoom out more? According to the present cosmology theories: NO. Computer simulations starting from right after the Big Bang show that this foam-like structure on a scale of hundreds of millions of light-years is to be expected. Starting point for these simulations is the measured Cosmic Background Radiation CMB), as depicted in the image below.

To explain the relation between this CMB image and the large-scale structure asks for another post…:-). Basically the Standard model of Cosmology is used, including the effects of Dark Matter and Dark Energy. Here is a typical result of such a simulation. The image has a width of 1500 million ly The bright nodes represent Superclusters. You will notice strings of galaxies and voids, quite comparable to the real Universe. At this scale, the Universe looks basically everywhere the same.

We started this post with the discovery of a group of quasars extending about 4000 million ly. Quasars are nuclei of galaxies, so in the terminology used above, they would form a “cluster”. But a cluster of this size would not fit in the above image at all!

This explains the excitement among astronomers and cosmologists. Is the Standard Model of Cosmology wrong?

Let’s wait and see!

Several images in this post come from a fascinating website: An Atlas of the Universe

Doomsday 2012 and the Sun

Posted on December 31, 2012 by janstu

The Mayan Long Count calendar ended on 21-12-2012. Actually it did not really end, but a new cycle started on that date. So 21-12-2012 can be seen as Mayan New Year’s Eve. The next one will be on 26-3-2407.

Quite a few people expected that the world would end on this day. Sad. Suddenly Nibiru would show up behind the moon and destroy Earth, or the magnetic field of Earth would suddenly reverse, etc.

Here is a picture of the Sun, apparently taken just after “Doomsday”. It looks like the Sun is winking…:-). The picture comes from a recent newspaper article, personally I doubt if the picture is authentic, especially the “lips” I find suspicious.

In the past I have published several posts about the Sun. It will reach a maximum in its 11-year sunspot cycle, next year. It is becoming clear now that this maximum will be very low. Here is a picture updated until December 2012.

The expected maximum of around 72 will be the lowest since 1906. Nevertheless Michio Kaku , the physicist “who would kill his mother to get publicity” (quote by me, LOL) is warning about solar storms that might create havoc on earth.

Paintballing Apophis!

Posted on October 31, 2012 by janstu

Before I started blogging, I wrote emails to a group of friends, interested in science. Several of these emails I have, after editing, entered as posts for my blog.
The first email (and now the first post on this blog) was about Apophis, an asteroid, that will pass Earth in 2029 at a close distance, and might (with a chance of 1 to 250.000) collide with Earth 7 years later, in 2036

This is an artist impression of Apophis, diameter ~ 270 m with an estimated mass of 27 megatonnes.

A collision with the earth would be a catastrophe. The impact would be the equivalent of 900 megaton TNT, ~ 60.000 Hiroshima atomic bombs.

When Apophis was discovered in 2004, there was a brief period of concern that this asteroid might hit Earth in 2029. It will not, and even in 2036 the chance is almost neglegible

But there are thousands of asteroids with orbits that may bring them close to Earth, so called NEA‘s, and NASA has an observation program to monitor them.

What to do when an asteroid is discovered which is on a crash course with Earth? We will have to deflect it! How? Many solutions have been proposed. Send a rocket to the asteroid and detonate a nuclear bomb, or let the rocket crash itself against the asteroid. Or use a strong laser beam to deflect the course.When you do this while the asteroid is still far away, a tiny change in course could be sufficient.

For a couple of years already a yearly competition “Move an Asteroid” is organised by the Space Generation Advisory Council , for students and young (space) professionals.

This year the competition was won by a MIT graduate student, Sung Wook Paek.

His winning proposal:

Launch a rocket, with a cargo of 5000 kg of pellets, filled with white paint. When near the asteroid, fire two salvos of pellets, timed in such a way, that the (spinning) asteroid will be completely covered with a very thin layer of white paint.

Here are two screenshots of a YouTube clip, published by MIT. In the left picture two pellet clouds are approaching the asteroid. In the right picture one cloud has painted one half of the asteroid white already.

The colliding pellets will change the course of the asteroid a little bit. That is not new, but the white paint is. The photons from the sun will reflect against this bright white surface, and this results in (additional) radiation pressure. Also a tiny effect, so this kind of action should be taken, many years before the asteroid comes close to the earth.

Cosmic paintball, what a nice idea!

How is the Sun doing these days?

Posted on September 18, 2012 by janstu

My last post about the Sun is from August 2010. At that time it had become clear already that the present Solar Cycle 24 would be a weak one. We are now two years further, the maximum in solar activity is expected around September next year. Time for an update.

Here is the most recent prediction, with data points until September

The current prediction is a (smoothed) sunspot number maximum of about 76. That is low! We have to go back to Cycle 14 in 1906, to find a lower maximum value of 64.

Here is a graph of the Solar Cycles over the past four centuries. With red crosses I have marked the 1906 maximum and the (predicted) 2013 maximum.

You will notice that the last half century we have had a “wave” of solar activity. Is that coming to an end now and will we enter a period of low solar activity? Nobody knows, as we do not understand very well the origin of the Solar Cycle.

Both the Maunder minimum (17th century) and the Dalton minimum (~ 1800) had influence on the Earth climate. Severe winters in Europe as can be seen in paintings of the Dutch School, like this famous one by Hendrick Avercamp (1585-1634)

Now we live in a period of global warming. There are strong indications that our carbon emission is at least partly responsible for this. But could there also be a contribution due to the high solar activity during the last fifty years? Those are sensitive questions..:-)

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Category Archives: Astronomy