Anybody out there?

When you have followed my blog posts, you will know that I am a supporter of the Rare Earth Hypothesis. Mind you, I will be more than happy if  proof of extraterrestrial life is found, but for the time being, I think we may well be alone in the Universe..:-(

Actually, for many years already I am participating in the SETI@home project. SETI stands for Search for ExtraTerrestrial Intelligence. The purpose of the project is to analyse radio signals for signs of intelligent life in the universe, and it is doing this by what is called distributed computing. The data to be analysed come from the Arecibo radio telescope in Puerto Rico.

More than 120.000 PC’s all over the world take part, my PC is one of them. When my computer is idle, it starts analysing a data packet received from Arecibo. Results of the analysis are sent back to SETI, I receive a new data packet and so on…:-)  Here is the Arecibo telescope (with its mirror diameter of 300 m the largest in the world) and a screenshot of my monitor while it is analysing the data. Visual output is a screen saver, moving around the screen all the time..

Arecibo_Observatory_Aerial_View_small

seti

The project has started in 1999 but until now no sign of (intelligent) life has been found.

You might describe this activity as LISTENING : is there anybody in the universe trying to communicate with us?

What about SHOUTING : is anybody out there? That is the topic of this post. Making our (human) existence known to the universe.

The first attempt to send out a signal to the universe dates back to 1972. The Pioneer 10 space probe was going to explore Jupiter and would leave the solar system after the end of its mission. Carl Sagan , who had been active already in promoting SETI, suggested  that a “plaque” should be attached to the space probe, with information about our human species. The left image gives an artist impression of the Pioneer 10, now traveling in outer space, far away from Earth. It might come close to Aldebaran, a red giant star, in about 2 million years..:-) The right image shows the Pioneer plaque, designed by Sagan and his wife.

1024px-Pioneer_10-11_spacecraft

Pioneer_plaque.svg

For more info about the meaning of the various elements, click on the link above. Here I only want to mention that there was a discussion about the naked humans. Was that acceptable of “porn”? By the way, the male genitals are shown, but the female vagina is missing, so aliens will still be in doubt how we reproduce. Would they be able to interpret the info correctly? Here is a hilarious interpretation: the Real Pioneer Plaque

Five years later the two Voyager space probes 1 and 2 were launched, again to explore the outer solar system. They have been extremely successful and are still operational, after almost 40 years! The Voyager 1 is now 19.6 billion km away from Earth, you can check the actual distance here . It has on board a phonographic(!) record containing information about Earth and about us. A kind of time capsule! The left image shows an artist impression of the Voyager 1 with the location of the golden record clearly visible. The right image shows the cover of the Voyager Golden Record.

voyager

The_Sounds_of_Earth_Record_Cover_-_GPN-2000-001978

Mind you, in 1977 digital coding was not common, no jpeg or mp3 existed yet, it was all analog!. Here is a fascinating Table of Contents of the Golden Record. Please click on this link and be surprised. A welcome message by Jimmy Carter, at that time US president! Greetings in 55 languages. One of them in Dutch (yes!), another one in Indonesian, four Chinese dialects, but no Malay, nor Tamil..:-(  Music, from classical until modern. But this time no picture of naked humans, thanks to a (still) prudish US..:-).

If ever an alien civilization would pick up this time capsule, would they be able to decipher it? Some sources doubt it,  check this funny Gizmodo report

You might compare these first attempts with throwing a bottle in the ocean. Maybe somebody will ever find it. Can we get more active?

Yes, we can. In 1974 the Arecibo telescope, mentioned above, sent out the Arecibo message to the Universe. A sequence of 1679 zero’s and one’s. Why that number? Because it is a semi-prime, product of two large prime numbers 23 and 73. When you order the message, split in a matrix of 73 x 23, you will get this (in black and white!):

320px-Arecibo_message.svg

To “explain” this, the white part represents our decimal system, the green one the  nucleotides  in our DNA, the blue one the double helix. The red human has next to it the human size (in binary) and the human population (also in binary), but probably you understood that already, didn’t you…LOL? Yellow represents our solar system, the third planet is shifted to the left with the human standing on it. Easy, right?

But would you be able to reconstruct the content from this binary sequence?

000000101010100000000000010100000101000000010010001000100010010110010
101010101010101001001000000000000000000000000000000000000011000000000
000000000011010000000000000000000110100000000000000000010101000000000
000000000111110000000000000000000000000000000011000011100011000011000
100000000000001100100001101000110001100001101011111011111011111011111
000000000000000000000000001000000000000000001000000000000000000000000
000010000000000000000011111100000000000001111100000000000000000000000
110000110000111000110001000000010000000001000011010000110001110011010
111110111110111110111110000000000000000000000000010000001100000000010
000000000011000000000000000100000110000000000111111000001100000011111
000000000011000000000000010000000010000000010000010000001100000001000
000011000011000000100000000001100010000110000000000000001100110000000
000000110001000011000000000110000110000001000000010000001000000001000
001000000011000000001000100000000110000000010001000000000100000001000
001000000010000000100000001000000000000110000000001100000000110000000
001000111010110000000000010000000100000000000000100000111110000000000
001000010111010010110110000001001110010011111110111000011100000110111
000000000101000001110110010000001010000011111100100000010100000110000
001000001101100000000000000000000000000000000000111000001000000000000
001110101000101010101010011100000000010101010000000000000000101000000
000000001111100000000000000001111111110000000000001110000000111000000
000110000000000011000000011010000000001011000001100110000000110011000
010001010000010100010000100010010001001000100000000100010100010000000
000001000010000100000000000010000000001000000000000001001010000000000
01111001111101001111000

 

These communication attempts date back quite a long time. Here is a recent one. On 9 October 2008 a high-powered digital radio signal was sent towards the Gliese 581c extrasolar planet: called A message from Earth. Followers of my blog may remember Gliese 581 as the name of a star with more than one habitable planets in orbit. Here is the blog report: New extrasolar planet has been discovered

The distance is about 20 light year, the message will reach the star in early 2029. If “they” reply immediately , we may expect a reply around 2050…:-) Here is the Ukrainian (!) telescope used to send out the message, and a sketch of the Gliese 581 planetary system.

70-м_антенна_П-2500_(РТ-70)

Gliese-581d-habitable-BEST1

Let me end this post with a question:

Is it wise for us to make our presence known to the Universe?

Stephen Hawking is not so sure about it and he is not the only one. Contact with aliens  could be risky.If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans ,” he said. “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet.”

A contact with aliens might be very different from Spielberg’s Close Encounters of the Third Kind, my favourite science fiction movie, released in 1977.

Close_Encounters_of_the_Third_Kind_Aliens

About galaxy SDP.81

This astronomy blog needs a fairly long introduction, sorry…:-)

Our Sun is one of the more than 100 billion stars in the Milky Way galaxy. Here is the Milky Way, as seen from Earth. Many of you may never have seen this “milky” band, because you need a clear sky without light pollution. Next to it an artist expression of the Milky Way with the location of our Sun indicated by a red arrow.

milky-way-afpgt

milkywayr

The Milky Way is one of the about 100 billion galaxies in the observable Universe. The Andromeda galaxy (left pic) is a close neighbour at a distance of about 2.5 million light-year.  The picture to the right was taken by the Hubble telescope. This image shows about 10.000 galaxies!

m31big_small

01_January_small

Many of you will have seen (and admired) the images taken by the Hubble telescope. Here is the telescope, it is still orbiting Earth at an altitude of ~ 550 km. Next to it the probably most iconic Hubble image, nicknamed the Pillars of Creation.

HST-SM4_small

pillars of creatrion_cropped

But not many of you will have heard about the Herschel telescope! This space telescope has been operational from 2009 to 2013. Its major objective was to discover how the first galaxies formed and evolved, starting from clouds of gas and dust. These clouds are not yet hot enough to emit visible light, but they still emit (thermal) radiation with wavelengths in the far infrared. It is this far infrared and sub-millimeter radiation that Herschel has recorded. Here is the Herschel telescope and a picture, taken by it. Not as spectacular as the Hubble pictures, right?

image description

Herschel-ATLAS_SDP_display

Actually, each pinprick in this image is a galaxy! Or better, a galaxy “under construction”, still basically a contracting cloud of gas and dust, Hubble would not be able to see them. Most of these galaxies are billions of light years (ly) away, the radiation we receive now, has been sent out when the universe was young.

We are finally coming closer to SDP.81. It is one of the baby galaxies (ID81 in the image below), discovered by Herschel, at a distance of about 11.7 billion ly .  Why is it (and a few more) so bright ?

Herschel-ATLAS_SDP_lenses_small

Here comes the surprising answer: because its radiation has been magnified by a gravitational lens between this galaxy and earth!

A gravitational lens? Yes, Einstein’s General Theory of Relativity predicted that light can be bent by massive objects. Or, formulated more correctly, massive objects will curve the fabric of space-time. His theory was spectacularly confirmed in 1919 during a solar eclipse (and made Einstein instantaneously famous!)  Here is a schematic diagram of this light bending.

4a4a7

In the case of SDP.81 a massive galaxy is located, 3.4 billion ly from Earth, exactly between us and SDP.81. A rare coincidence? Sure, but keep in mind that there are 100 billion galaxies..:-)

A  gravitational lens works differently from a traditional lens where the light bending is strongest at the edge of the lens. Here it is the other way around, bending is stronger near the center. When the alignment is perfect the (magnified) image becomes a ring,  a so-called Einstein Ring. Here are a few examples of Einstein rings, images (in visible light) taken by Hubble. Some are only partial because of misalignment.

hubble_ein_rings

Wouldn’t it be great to find out if the image of SPD.81 is also an Einstein ring? Then we need a much higher resolution then the (already large) 3.5 meter mirror of Herschel could give us.

Alma can help us! ALMA stands for Atacama Large Millimeter/submillimeter Array. It is a collection of 66 radio telescopes  (with 12 and 7 meter antennas), located at 5000 meter altitude in Chili. Here is ALMA

DCIM114GOPRO

Technically it is called an (astronomical) interferometer. To keep it simple: the radio telescopes work together in such a way that they effectively combine to a huge mirror of many hundreds meters or even kilometers diameter. The telescopes can be moved around. The high altitude has been chosen because the climate in the Atacama desert is extremely dry, crucial for observations in the millimeter/submillimeter range. The maximum resolution has been described by the  Alma astronomers as being “about the same as seeing the rim of a basketball hoop atop the Eiffel Tower from the observing deck of the Empire State Building“.

Here is Alma’s result for SDP.81, published a few weeks ago. An almost perfect Einstein ring! Keep in mind that this radiation is invisible, the red color has been added for the dramatic effect. And the visible light of the lensing galaxy is not recorded by ALMA.

ALMA_image_of_the_gravitationally_lensed_galaxy_SDP.81_small.

And here is a combination of three images. The left image is taken by the Hubble space telescope. The lensing galaxy is visible. The middle picture shows the Alma result, in more subdued colours. And the third picture? Montage of the SDP.81 Einstein Ring and the lensed galaxy

The Einstein ring in the middle picture is a “distorted” image of SDP.81. But, assuming a (simple) model for the gravitational lens in between, you could try to reconstruct the “real” image. And that’s what has been done with the third image as result.

An (approximate) image of the SDP.81 galaxy how it was, almost 12 billion year ago, when the Universe was still young. Some structure is visible, the bright parts are regions of dramatic star formation.

Amazing!

Close Encounters

The Close Encounter concept has been introduced by ufologists, people who believe in ufo’s and aliens. You will not be surprised that I don’t, although, to be honest, the Spielberg movies  E.T. and Close Encounters of the Third Kind, belong to my absolute favourites….:-)

Close Encounters

The close encounters in this blog post are different and more prosaic . Not between humans and aliens, but between spacecraft and “celestial bodies”. In the past  fifty years hundreds of close encounters have taken place, with spacecraft flying by, orbiting or even landing on planets, moons, comets and asteroids in  in our solar system. If you are interested in the whole list (314! and counting), surf to NASA’s National Space Science Data Center and select “Planetary Science”.

In this year there will be two memorable and exciting close encounters.

DAWN

Next week ( 6 March), the Dawn spacecraft will enter orbit around the asteroid Ceres. Here is an artist impression of Dawn and its travel to Ceres, starting already in 2007

Dawn

The asteroid belt is located between the orbits of Mars and Jupiter. Ceres is, with its diameter of  950 km, the largest of the asteroids. When it was discovered in 1801, it was considered a planet for some time. As you see, on its way to Ceres, Dawn has first explored Vesta, the second-largest asteroid (diameter 525 km). Here is a composite image of Vesta taken by Dawn. Note the three craters, nicknamed the “snowman” and the “bump” at the south pole, a mountain twice as high as Mount Everest…:-)

Vesta

Dawn left Vesta in September 2012 and is now closing in on Ceres. Here is a picture taken by Dawn ten days ago, on 19 February. Note the two bright spots. The scientists have no clear idea yet what they are, and of course they are getting excited…:-)

Ceres

Ceres is the final destination of Dawn. The coming months it will explore the surface of Ceres  from various distances and finally settle down in a stable orbit (July 2015). You can follow Dawn on the Dawn Blog

NEW HORIZONS

On 19 January 2006 the New Horizons spacecraft was launched from Cape Canaveral. Destination: Pluto, at that time still the ninth planet of our solar system. But not for long, because later that year Pluto was degraded to the status of dwarf planet, together with Ceres. The left picture shows the trajectory of New Horizons, with its actual position on 28 February, the right picture gives an artist impression of the spacecraft closing in on Pluto and its moon Charon.

New Horizons trajectory

New Horizons and Pluto

After passing Jupiter in 2007, the spacecraft has gone into hibernation for considerable times, to save energy. Every now and then waking up to let Earth know that it was still alive…:-). Last year in December, it became fully awake again.

As you see, Pluto is an outsider, with its very elliptical orbit. We know consider it a member of the Kuiper Belt. The spacecraft will fly by on 14 July this year and come as close as ~ 10.000 km! How will Pluto look like? Here is an artist impression of Pluto’s surface, its moon Charon and the Sun. Yes, that is our Sun, not much more than a bright star. Communication with New Horizons takes more than 4 hours, one way.

Pluto

If the spacecraft keeps functioning, we will know a lot more about Pluto after the fly by. Exciting!

New Horizons will not go into orbit, just fly by. With the little fuel left, it will try to visit a few more members of the Kuiper Belt, and then leave our solar system, like the two Voyagers before. But that is a topic for another post.

ROSETTA

One more memorable event in 2015. I have reported a few times already about Rosetta, now in orbit around the comet 67P. This comet will reach its perihelion (closest to the Sun) in August this year. Already part of the comet is evaporating (forming the famous “comet tail”). Rosetta is still exploring the comet from various distances. The left picture, taken from far, shows the evaporation. The right picture is a close-up from the surface, taken from a distance of 8.9 km only!

67P

close up

The location of the Philae lander is still not accurately known. The scientists are hoping that soon this lander will get enough sunlight (it is probably in the shade of a rock wall) and will wake up again. Let’s keep our fingers crossed..:-)

 

Here is Rosetta again! (updated)

In two earlier posts I have reported about the exciting space adventure of Rosetta, a spacecraft launched in 2004 with as destination a comet, the  67P/Tsjoerjoemov-Gerasimenko. The first post, Wake up, Rosetta!, described how, after a hibernation of more than two and a half years, Rosetta woke up in January 2014, according to plan.

The second post, Rosetta meets 67P, published last August, reports how Rosetta successfully goes into orbit round the comet. It turns out that the comet has a strange shape, like a rubber bathtub duck.  Here is a picture, taken on 19 September at  28.6 km from the center of the comet. The head points to the right. If you look carefully you will see a kind of smoke coming from the “neck” of the comet. That is the coma, part of the comet material is evaporating because it is approaching the sun. Later, closer to the sun, 67P will develop the characteristic comet “tail”. The comet is rotating with a period of 12 hours and 36 minutes.

67P

The last few months the scientific instruments on board Rosetta have already been busy. For example analysing the composition of the “coma” smoke. With interesting results, finding not only water and carbon dioxide, but also methanol, ammonia and hydrogen sulphide. Here is an interesting blog about The “perfume” of 67P.  Quote:  If you could smell the comet, you would probably wish that you hadn’t

But the ultimate goal of the expedition is to land a module on the comet itself! This module has been called Philae and you can see it here still attached to Rosetta.

Rosetta with Philae

The last few months,  the scientists have been working hard to find a suitable landing site for Philae. That has not been a simple job, because of the complicated structure of the comet. The landing site should be relatively flat and smooth. Several options have been studied, finally the decision was made to choose location J, on the head of the duck in the picture below.

Landing sites

The landing site has now been renamed Agilkia. Why? Google and find out yourself 🙂 Hint: there is a relation with Rosetta and Philae.

The critical landing operation will take place on Wednesday November 12. At 8:35 GMT Philae will be deployed from Rosetta and start its slow fall to the comet.  It has no thrusters that can change its course, so ultimate precision is required in the timing of the separation. Keep also in mind that the distance between earth and the comet is at the moment about 500 million km, so signals take time to reach Rosetta. To be exact: 28 minutes and 20 seconds one way! So it will be 9:03 GMT before we know if the separation has been successful.

Falling to the comet? Yes, because the gravitational attraction of the comet is very small, but it exists. The falling proces willl take about 7 hours! And the speed at landing will be “only” ~ 1m/s. For comparison, that is the speed an object would get here on earth, when it falls 5 cm!

As soon as Philae touches the surface of the comet, two harpoons will be fired down to anchor the module. Otherwise it might bounce back into space! Here is an artist impression of a successful landing.

Philae landed

The two red lines under Philae are the harpoons. The construction of the three supporting “legs” allows landing on moderate slopes. If the slope is steeper than 30 degrees, the Philae might topple over, resulting in failure. The whole procedure is considered a risky one, success estimates of 75% “only” have been mentioned..

So let us keep our fingers crossed Wednesday! Malaysian time is GMT + 8 hrs, Dutch time is GMT + 1 hr. Here is the ESA control room. How many nails will be bitten on that day, waiting seven hours, while you can do nothing…:-)?

ESOC

On Wednesday there will be a live broadcast of the landing procedure

UPDATE 12 NOVEMBER

5am GMT

The Live broadcast has started already. It is still early in Darmstadt, people are arriving in the ESOC control room, where it is obviously quite cold…:-) Many sniffy people.

Here is a diagram of what will happen today. As I explained in my post, after separation Philae will “fall” to the comet. No course correction possible after separation, so utmost precision is needed

.Rosetta_s_trajectory_12_November_node_full_image_2

The last few days pictures have been taken by Rosetta with amazing details. Click here for a collection. Here is  a spectacular one.

67P_detail

7:30 GMT

Just watched an interview with Gerhard Schwehm, mission manager of the Rosetta project. Now retired. I did not realise that the project started in 1985, almost 30(!) years ago. Less than one hour now until separation.

8:05 GMT 

I have been naive..:-) Thinking that at this moment the command should be sent to Rosetta to deploy Philae (because it takes 28 minutes for the signal to reach Rosetta). But of course they will not do it that way..:-)  Rosetta has been programmed to deploy Philae at 8:35am !  Around 9am GMT the ESOC will know if that separation has been successful.

8:35am  GMT

At this moment, 511 million km away, the Philae is starting its fall to the comet 67P. In spite of a problem that has been found in the  lander. As explained in my post, the Philae could bounce back after touching the surface of the comet. Therefore two harpoons are fired at touchdown to anchor it. Also, on top of the Philae, an amount of gas should be released, giving the Philae an extra push to the surface. It seems that this “thruster” doesn’t work properly.So everything will now depend on the harpoons.

9:05am GMT

Separation is succesfull!!

Waiting. Tense

Waiting

Relief. Hugging

We did it

From now on, the Philae is on its own. In two hours time hopefully contact will be reestablished between Rosetta and Philae

11:10am GMT

Contact established between Philae and Rosetta! Great! This is a bigger step than the deployment. Philae is too weak to communicate directly with Earth, it has to do that via Rosetta. And it did! So now we can follow its descent to the comet, and it may even be able to send pictures.

Tension and relief again..:-)

Waiting for a sign of life2

We got it

2:20pm GMT

The first image taken by Philae of Rosetta, just a short time after deployment. Unprocessed, so not high quality, but convincing proof that Philae is on its way to 67P

Rosetta as seen from Philae

2:40pm GMT

Telemetry data from Philae show that it is following the calculated trajectory accurately. The landing will be the most critical part. Everybody at Esoc keeps his/her fingers crossed.

Here is an image taken by Rosetta’s Osiris camera of the descending Philae lander. Amazing. The landing arms are out.

filae

3:30pm GMT

Waiting now for news about the landing. Personally I do no like the optimistic way of talking about success. There is a reasonable chance of failure, and then the disappointment will be huge.

4:05pm GMT

Success? Or not? It seems Philae has landed. Congratulations

And within minutes the news is spreading all over the world…:-)

CNN

UPDATE 14 NOVEMBER

We know now that the Philae has really landed, but not without difficulty! The harpoons meant to anchor the lander, did not fire, so the lander bounced back after touchdown. Because of the low gravity of the comet, it took almost 2 hours before the second touchdown! Then, a few minutes later, the third and final touchdown. The first bounce took the lander up, about 1 km vertically, but also possibly the same distance horizontally. So at the moment the scientists are not sure where actually the Philae landed! During a live broadcast, 13-11, one of the lead scientists explained that the intended landing location was the red square (see below). But after the two bounces, the probable location is now within the blue “lozenge”

location

Because the Philae is not anchored, some of the planned experiments (like drilling to obtain and analyse some comet material) will be risky, as the lander might loose its balance and topple over.

It seems that the Philae has landed in a location that is more rocky than intended, maybe even beside a cliff. Those rocks may obstruct sunlight from reaching the solar panels of Philae. At the moment Philae is using the energy of its batteries, but soon it will depend on solar energy.

So there are minor(?) problems, which can hopefully be solved. Still the landing is an awesome achievement and at the moment the lander is already collecting scientific data and sending them to Rosetta. Also pictures of the surroundings have been taken. Here are first results, not yet fully processed. To the left a series of six “panoramic” pictures. On some of them a foot of the Philae can be seen. The collage to the right shows the same pictures, but with Philae superimposed.

ESA_Rosetta_Philae_CIVA_FirstPanoramic-838x1024

Comet_panoramic_lander_orientation_node_full_image_2

 

 

 

Where does the Moon come from?

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.

perigee full moon

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.

Names of seas and craters

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

Far 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 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.

Theia meets Gaia

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

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.

theia1

theia2

theia3

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

Rosetta meets 67P

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. Comet 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.

67P_London

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!

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.

Rosetta and Philae

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.

Nucleus of 67P

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).

Rosetta flight path

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.

Stein asteroid

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.

Lutetia

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

The signal

Hello World, I am awake

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

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.

Sunspots

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

Cycle 23 and 24

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.

Solarcycles

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.

solar images

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)

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

2011_nobel_prize

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 1956 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)

future_of_the_universe

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”

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.

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 ..:-)!

Before and after

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.

accelerating universe

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.

darkenergy_pie

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

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.

Asteroid hits Earth

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!

Distribution of NEO's

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.

Neo impact risk

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

Neoshield

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