Total Solar Eclipse 2017

Are you using Whatsapp and did you recently receive this picture? Getting excited already, that in a few weeks time you will observe a unique event?

Sorry to disappoint you, but this is complete nonsense. Yes, on 21 August 2017 there will be a total solar eclipse, and to watch it is an experience of a lifetime. But solar eclipses are common, almost every year there will be a solar eclipse visible, somewhere on Earth..:-)

Here is a list of solar eclipses between 2011 and 2020. In the third column the type of eclipse is given. Twenty four eclipses in total, five of them total. The last column gives the geographic region where the eclipse will be visible.

I do not want this blog to be very technical, but some explanation may be useful..:-)

A solar eclipse occurs when the moon passes between the sun and the earth.

The moon orbits the earth in about 29 days, so you would expect a solar eclipse roughly every month. But the orbital plane of the moon is tilted 5 degrees, therefore the shadow of the moon will not touch the earth every month. Also, because of the (big) size of the sun, the shadow of the moon (the white lines) just reaches a small part of the earth. The pink lines mark the region where the moon blocks the sun only partially.

Another effect is that the orbit of the moon is slightly elliptical, so the distance of the moon to the earth is not always the same. If the moon passes between the sun and earth while it is farther away from the earth, it can not block the sun completely, resulting in an “annular” eclipse.

Let us look in a bit more detail at the 21 August eclipse. The blue band is where you can see the total eclipse. Weather permitting of course…:-) The light blue lines parallel to the blue band indicate the regions where you have a 75%, 50% and 25% partial eclipse.

Is there anything special about this eclipse? Yes..:-)  It will only be visible from the Unites States of America and no other country!  AMERICA FIRST…:-)  Probably Trump will  twitter one of these days that it is one of the successes of his administration…;-)

Of course there is a lot of interest in the USA for this Great American Eclipse . Here are a few advertisements, taken from the Internet.

But also for the USA it is not a unique event. The last total eclipse, visible in mainland USA, was on 26 February 1979 and the next one will be on 8 April 2024.

Total eclipses are spectacular. It gets dark, and the solar corona becomes visible. A reason for many people to travel to a region where the total eclipse can be watched.

Actually I was one of them, 8 years ago!

Friends  told us about a total eclipse, visible in China on 22 July 2009.  Here it is

We decided to visit China, Hangzhou region, around that time, hoping for clear skies. The full report you can read here: China July 2009 part I: Hangzhou.

Many people, locals and tourists,  full of expectation.

Actually it was rather cloudy. Here you see pictures during the start of the eclipse. We kept our fingers crossed.

And we were lucky. The clouds were breaking, it was not completely clear, but enough to see the “diamond ring” and the corona

It was an unforgettable experience. As it will be for the Americans (and the many foreign tourists) on 21 August.

When you compare the two eclipse maps, you see in the lower right corner the duration of the totality.  The China one 6m 39s, the American one “only” 2m 40s. CHINA FIRST!

The maps come from a very informative website about solar (and lunar) eclipses,

Jupiter and Juno

This post is about the planet Jupiter and the spacecraft Juno, launched in August 2011 and orbiting Jupiter since July 2016. The image shows both the planet and the spacecraft.

But we will start with some Roman (Greek) mythology. Jupiter (Zeus) was the king of the gods and Juno (Hera) his wife. Jupiter was an promiscuous god with numerous extramarital affairs and Juno was a jealous spouse, always keeping a eye on her adulterous husband.  Here are a few of his affairs

  • He lusted for Io, and transformed the girl into a cow, to hide her from  his wife. In vain, Juno asked him to give her the cow as a present.
  • He abducted Europa, disguised as a bull. King Minos of Crete was one of their children
  • He fell in love with the nymph Callisto and took the shape of virgin goddess(!) Artemis to seduce her.
  • He was so enchanted of Ganymede, that, in the shape of a raven, he took the beautiful boy(!) to Mount Olympos.

You will understand that as schoolboys we were always happy when our Latin and Greek  teachers told us about these myths…:-)

Back to astronomy. Jupiter is the largest planet in our solar system. The planet is so big that all the other planets would fit in it. It is the second-brightest planet (after Venus) in the night sky.

In 1610, Galileo discovered that Jupiter has four moons. In the image you can see their size, compared to Jupiter. They look small beside the planet, but they are actually big. The largest one, Ganymede, is bigger than the planet Mercury!

The four moons were named after the four lovers of Jupiter named above! Below you see a (resized) image of each moon and a painting with Jupiter in action.

Since Galileo observed the four moons, many more (smaller ones) have been discovered. At the moment 67  moons have been observed, of which 53 have been named, often after Jupiter’s girlfriends and boyfriends…:-) Here is the complete list of Jupter’s moons

It may now be clear why the spacecraft has been named Juno  🙂  After the launch of the spacecraft, NASA published a mission statement in which they explained the name of the spacecraft:

The god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife, the goddess Juno, was able to peer through the clouds and reveal Jupiter’s true nature.”

Actually the mission of Juno is to explore Jupiter and not his moons…:-) Much is still unknown about this gas giant. Does it have a solid core? Does its atmosphere contain water? An important part of the mission will be the study of Jupiter’s gravitational and magnetic fields.

So, let us follow Juno on her exploration of Jupiter. It took her five years to reach Jupiter. Why so long? Here is the reason:

To give the spacecraft enough speed at launch to reach Jupiter would cost too much energy. Therefore it is first launched in an (elliptical) orbit around the sun.

The Deep Space Maneuvers one year later will bring it back very close to Earth, which will give it a gravitational slingshot. See my Rosetta blog for an explanation.

As a result the orbit becomes a hyperbole, at the right moment crossing the orbit of Jupiter, where it will be captured by the planet.

Here is a fascinating animation of the whole process.

Jupiter has to be approached carefully because of its intense radiation belts. The magnetic field of a planet traps charged particles like electrons and protons in a doughnut-shaped region around the planet. Earth has these radiation belts, they are called the Van Allen Belts. For Jupiter they are many thousand times stronger and can seriously damage the spacecraft.

To protect the instruments of Juno, the most sensitive ones have been placed in a titanium container with 1 cm thick walls and a weight of 18 kg.

Here is an image of the spacecraft during assembly. The Radiation Vault is the brown box on top of the spacecraft.

Note the size of the human!

To minimise the radiation risk, Juno has to be captured carefully in a polar orbit. Here is a YouTube animation:

The capture orbit is very elliptical with a period of ~ 54 days. The original plan was to reduce the period to 14 days, after two capture orbits (1 and 2). The first reduced orbit (3) would be a clean-up orbit, followed by 32 “science” orbits (4-36), each of them slightly shifted, so the whole surface of Jupiter would be covered.The image gives an impression of these science orbits. Mind you, during each 14 days only a few hours before and after perijove (the point of shortest distance to Jupiter) can be used for science!

However, during the second orbit, a few days before the planned Orbit Reduction Maneuver on 19 October 2016, a problem was found with some helium valves needed to operate the main engine, and a few hours before perijove, the spacecraft went into “safe mode”, because the onboard computer encountered unexpected conditions. The next two orbits were used for testing and diagnostics.

Finally, on 17 February 2017, mission control decided it was too risky to perform the Orbit Reduction Maneuver. So the  spacecraft will remain in  its 54 day orbit. Totally 12 science orbits will be performed until July 2018. The next perijove (orbit 7) will occur on 11 July.

It must have been quite a disappointment for the scientists, instead of new data every two weeks, they now have to wait almost eight weeks.

Are there results already? The instruments that are measuring the magnetic field of Jupiter and the composition of the Jovian atmosphere are collecting data, it seems the magnetic field is more lumpy than expected.

The most spectacular results come from the on-board camera Junocam. Here is an image of Jupiter’s south pole, not observable from Earth. Amazingly complex and turbulent.

And last week NASA published another picture, taken 19 May, just after Juno passed perijove 7. Keep in mind that these images are color enhanced! Part of the south pole region is visible. The white spots are part of the “String of Pearls”, massive counterclockwise rotating storms.

The next orbit will pass over the famous Great Red Spot, a storm on Jupiter that has lasted already for several hundred years and is so big that Earth would fit inside it. Will be interesting to see images.

At the end of the Juno mission,  the spacecraft will be directed into the Jovian atmosphere, where it will be completely destroyed. This will be done to avoid any chance that material of Juno might “contaminate” one of  Jupiter’s moons. If ever life forms are found on these moons, there must not be any doubt about its origin.

To end this post in a lighthearted way, the Juno has three passengers on board! Figurines, specially crafted by Lego in the shape of Jupiter (with a lightning bolt), Juno (with a magnifying glass) and Galileo (with a telescope and Jupiter in his hand)

Preparing this post, I have made extensive use of a very informative web page: Juno Mission and Trajectory Design . Very detailed and sometimes quite technical, but worth reading.



Neighbour, here we come!

In a recent blog, Our nearest neighbour? , I reported about the discovery of the planet Proxima b, orbiting around a star, “only” 4.22 lightyear away from Earth. In several media it was suggested that within a few decades a spaceship could be launched to reach this planet. A spaceship is science-fiction, but there exists an ambitious plan to send a swarm of space-chips to Proxima b within a few decades. I promised to write a separate blog about this Breakthrough Starshot  Here it is.

In 1865 the French novelist Jules Verne wrote De la Terre à la Lune (From the Earth to the Moon), in which he describes how three adventurers travel to the moon in a projectile, shot from the earth by a large cannon. I have read it spellbound when I was a teenager. You can read it online here , it is fascinating (and hilarious too).

The illustrations are beautiful. Here  are some. From left to right the three adventurers climbing into the projectile, the comfortable interior and the firing of the canon.
verne1 verne2 verne3

Why this introduction? We know now that this method is not used in our space age. We don’t shoot our spacecraft to the moon or other planets, we use rocket propulsion.  The  Voyager 1 (825 kg) was launched by a Titan-Centaur rocket (600.000 kg). The images show the launch, the Voyager spacecraft and a structure diagram of the rocket. The Centaur is mounted on top of the Titan. A huge amount of fuel is needed to launch a “tiny” payload!

Voyager & Titan


After completing its mission, the Voyager is now leaving our Solar System with a speed of more than 60.000 km/h That is fast but it would still take about 75.000 year to reach Proxima b, if it was going in that direction (which is not the case).

So we can forget about  space travel to the stars, using rocket propulsion, at least in the foreseeable future. Is there another option, more in the style of Jules Verne?

Actually there may be one…:-)

One year ago Travis Brashears, a graduate student at the University of Santa Barbara in California, and his supervisor, Philip Lubin, professor of astrophysics and cosmology at the same university, published a paper Directed Energy Interstellar Propulsion of WaferSats in which powerful lasers “shoot” miniature (~ 1 gram only!) electronic chips away from earth in the direction of a nearby star, with a speed approaching the speed of light! Here are the (main) writers , Brashears left and Lubin right.


Does this sound as science fiction? For me it does. But apparently not for these guys.

Sure, light exerts pressure, there are several projects going on, using sunlight propelling a solar sail , a bit similar to the sail of a sailing boat being blown by the wind. One successful project is IKAROS, a solar sail of 196 m (!) , launched in 2010 by Japan. Here an artist impression of the sail, with Venus, its destination. The sail is so big. because the thrust of the sunlight is only small.


Next year March the LightSail 2 will be launched. To the left the actual spacecraft, a so-called cubesat. To the right an artist impression of the LightSail in space, with a deployed sail. Notice how small the cubesat is compared to the sail!



These projects are using sunlight. The project of Brashears and Lubin is futuristiic.

  1. A ground-based laser will be used as a “shotgun”  Estimated power needed 100 GW. That is a lot! The Three Gorges Dam in China, the largest power plant in the world, generates 22.5 GW.
  2. The spacecraft will be a chip with a mass of about 1 gram, with a light sail of ~  1 m2   . The plan is to prepare about 1000 of these miniature “spacechips” and launch them simultaneously in a mothership, orbiting the earth. From there the starchips will be shot, one after another on a daily basis, during 3 year.
  3. The laser will give a spacechip in about 10 minutes a speed of 20% of the speed of light. That is fast , 60.000 km/s
  4. The spacechips will reach Proxima b in about 20 year. Hopefully at least a few of them will have survived the journey.
  5. They will send back pictures to earth.
  6. Estimated cost of the project US$ 5-10 billion.
  7. Proposed launch date about 20-30 years from now.

Here is an artist impression of the launch. Mind you, the spacechip is the tiny dot in the center of the light sail!


Futuristic indeed. The time span of 20-30 year is because much of the technology still has to be developed. Designing a spacecraft on a centimeter-size, gram-scale chip, developing a light sail with a thickness of 1 micron or less, building a 100 GW laser and many more challenges.

Here another artist impression. The plan is to build a so-called “phased”  array of smaller lasers, with a combined power of 100 GW. If you use 100 kW lasers ( at the moment the maximum power available), you need a staggering 1 million of them.

Laser array

I am skeptic, as usual…:-) But not everybody is. Yuri Milner, for example is optimistic.  This Russian/American tech entrepreneur and multi-billionaire,  started as a physicist and is very interested in the big question “Are we alone in the universe“. In July 2015 he announced, together with the British physicist Stephen Hawking, the Breakthrough Initiatives , a program to search for extraterrestrial intelligence. At that time the program consisted of two parts.

  1. Breakthrough Listen.  Basically a large-scale version of the SETI project. Funded by Milner with US$100 million.
  2. Breakthrough Message. A prize pool of 1 US$ 1 million for the best (digital) messages that could be sent out into deep space. No concrete plan to actually send these messages, because for example Hawking thinks it might not be advisable to do that. See my blog Anybody Out There?

In April 2016, part 3,  Breakthrough Starshot, was announced by Milner and Hawking. Milner and Mark Zuckerberg (FaceBook) will contribute another US$ 100 million to explore the technological feasibility of the program outlined above.

Milner, Hawking and Dyson

From left to right Yuri Milner (holding a protoype of a spacechip in his hand), Stephen Hawking and “eminence grise” Freeman Dyson, a physicist and cosmologist, now 93 year old. If you are interested in really futuristic ideas, have a look at his Dyson Sphere 🙂

Below is an animation of the process. A few comments may be useful.

  1. There are 135 lasers in the array. You need at least 1 million.
  2. The spacechips are launched simultaneously in a container, but released and shot one after another.
  3. When they reach Proxima b after ~ 20 years, they will pass the planet at full speed (60.000 km/s). So fast that the camera on board can only take a few pictures. Also data will be collected about magnetic fields etc.
  4. These data will be sent back to earth, using miniature lasers on the spacechip, focused with the help of the light-sail.
  5.  About 4.22 year later, the ground-based laser array will receive these data. Hopefully…:-)

I have been working about two weeks on this blog, reading and collecting as much information as I could find. To be honest, I became more and more skeptic.

A few days ago Scientific American has published a very informative article about the Starshot Program: Inside the Breakthrough Starshot Mission to Alpha Centauri. Many scientists were asked for their opinion about the project. There is respect for the technological challenge, but scepsis about the scientific value.

Supermoon, 14 November 2016

Just a short post about the Supermoon of 14 November, widely publicised by the media the last few weeks as a not to be missed, once in a lifetime event. For example on Facebook

It’s a hype.

Supermoons are not rare, they occur regularly, on average every 14 months. The last one was 28 September 2015, the next one will be 4 December 2017.

Full moons have different sizes because the orbit of the moon is slightly elliptical. The image shows the moon orbit, exaggerated. The average distance to Earth is 385.000 km, but the moon can come as close as 356.500 km (perigee) and as far as 406.700 km (apogee). The moon orbit also rotates itself with a period of 8.85 year


As a result of these two effects, a full moon can sometimes occur when the moon is in or near its perigee. An observer on Earth will then see this full moon brighter and larger, than when it occurs in its apogee. Dividing the apogee distance by the perigee distance, we find 406.700 / 356.500 = ~ 1.14, so the moon will look ~14 % brighter and ~ 30 % larger. This effect is easily observable, as you can see in the image below.  By the way, the name Supermoon has been introduced by astrologers, the correct name is Perigee Full Moon.


So, why this sudden interest in this particular Perigee Full Moon of 14 November?

The values given for apogee and perigee are actually averages. Because of the influence of sun and planets they vary slightly in time. Here are the perigee distances during the Supermoons of 2015 and 2016 :

  • 356.876 km in 2015
  • 356.511 km in 2016

The perigee distance on 14 November is a little bit smaller! To be precise , 365 km smaller, ~0.1%. So the Supermoon of 14 November will be 0.1% brighter and 0.2% larger. Observable for the unaided eye? Not at all, believe me…:-)!

Why the hype?  When you look at the Perigee Full Moons in the past and future, you  have to go back to 1948 to find an even smaller full moon perigee: 356.462 km (49 km smaller).  And from now on you have to wait until 2034 to find a smaller one: 356.447 km (64 km smaller). These Supermoons will be ~0.02 % brighter.

That’s why it is said: the brightest Supermoon in 86 year…:-). Technically correct, but….   a hype.

My suggestion, try to observe the moon tomorrow, when it is rising, just after sunset. The moon looks always larger when close to the horizon! This is an optical illusion, the Moon Illusion. Combined with the Perigee Full Moon it will be beautiful

And when you are not free tomorrow, it is not that critical. One or two days later you can still admire the Supermoon.

Our nearest neighbour?

As you may know from my  blog, I think we may be alone in the Universe. But of course I would be more than happy if (intelligent) life would be found outside our own planet. My PC is taking part in the SETI project, see my blog  Anybody out there? Last week there was excitement about a strong signal from a sunlike star, but: No alien signal, says SETI astronomer.

Numerous extrasolar planets have been found by now, as of 1 September 2016 the count was 3518. A few dozen of them might be able to support life (rocky, similar size to Earth, orbiting in the habitable zone of their star).

So, why did this Letter to Nature (one of the leading science magazines) :  A terrestrial planet candidate in a temperate orbit around Proxima Centauri cause so much commotion that it became front page news in the media?

The answer is simple: Proxima Centauri is not just one of the hundreds of billion stars in our galaxy. It is the star closest to our Sun, at a distance of 4.22 lightyear “only“,

Let’s have a closer look at this nearest neighbour of the Sun.  Where can we find it in the night sky? And can we see it  with unaided eyes or binoculars?

Here is the night sky (in Malaysia) in March, south-eastern direction. You will notice three constellations, dominated by Centaurus. The name comes from Greek mythology, where a Centaur is a half-horse half-man creatureSky-march


Here is how the Greek saw a Centaur in the stars.

You may find it difficult to see a centaur, but the two bright stars in his left leg are conspicuous. Rigel Kent, better known as α Centauri, is the third-brightest star in the sky, after Sirius and  Canopus. 

Hadar (β Centauri) is also a bright star.

α Centauri is actually a star system, consisting of three stars. Two of them, α Centauri A and B are so close that they can not be separated by the unaided eye. Here is an image taken by the Hubble telescope.

Best image of Alpha Centauri A and B


α Centauri A (to the left) is slightly larger than the Sun, while B is a bit smaller. They orbit around each other with a period of 80 years.



The third component, α Centauri C is a red dwarf, much smaller and cooler (more reddish)  than the Sun. Very far away  (about 0.21 ly) from the other two. If it is bound by gravitation to A and B (not 100% sure), the estimated orbiting period is ~ 500.000 year. Here are A and B (seen as one star here) and C (in the center of the red circle). The other stars are Milky Way stars, much farther away.

The α Centauri system is closer to the Sun than any other star, about 4.35 ly away, and of the three components, α Centauri C is a bit closer (4.22 ly) and therefore it has been named Proxima Centauri.

Because of the close distance, the system has been studied intensively. A planet might be orbiting α Centauri B, but even if found to be true, it will not be habitable.


Now a planet has been found, orbiting the red dwarf in the α Centauri system. It has been called Proxima b. Very close to the star, orbiting it in about 11 days only. Compare this with Mercury’s period of 88 days. But because the star is less bright than the Sun, the planet is still in the habitable zone. Here is an artist impression how the planet could look like. α Centauri A and B are also shown, as bright stars.


Our closest neighbour! But a distance of 4.22 light-year means that Proxima b is still 40 trillion km away from Earth. At this moment spacecraft New Horizon, after taking spectacular pictures of dwarf planet Pluto, is leaving our solar system with a respectable speed of ~ 60.000 km/h. That is fast, but it would take ~ 80.000 year to reach Proxima b.

Here is what the Mail Online reported on 24/8. “The second Earth that we could visit in our lifetime”  and  “just four light years away

Actually there is an audacious plan to send a probe to Proxima b. Not a spaceship but a space-chip! Not one probe, but a swarm of them. Interested?  The project is called .Breakthrough Starshot and it deserves a separate blog post.

Here only a few comments on the idea of a “second Earth”.

  • As the planet orbits very closely to its Sun, it will probably be tidally locked, like Mercury. In that case the sun side will be scorching hot, the other side dark and freezing cold. Only the twilight zone might be able to support life
  • Proxima Centauri is a flare star, with occasional eruptions of radiation, comparable but much stronger than the solar flares. Not very suitable for the development of life.
  • Will there be water on Proxima b?  Earth got its water during the Late Heavy Bombardment. when numerous comets and asteroids, disturbed in their orbit by the giant planets, collided wit Earth.

In this very readable Scientific American blog more skeptical arguments are given.

Here are a few other habitable planets. Proxima b is not yet in this list, it belongs to the bottom row, Proxima Centauri is a so-called M star

Kepler-452b (top row) is sometimes nicknamed Earth’s Cousin..:-) But the distance to Earth is a whopping 1400 light-year!  It would take New Horizon about 25 million year to go there.

More about the Breakthrough Starshot project in a later blog post

Our Solar system, an update

My last blog about the Rosetta, Dawn and New Horizon missions was posted in July last year. Before I give an update, let’s first have a look at our Sun. Here is a recent graph of the number of sunspots. Cycle 24 has reached a maximum in April 2014 and is coming to an end.


As you will notice, cycle 24 has a double peak, in itself not unusual, but this time the second peak is higher than the first one. The maximum of cycle 24 is much smaller than that of cycle 23, and the prediction for cycle 25 is that it will be similar to cycle 24 or even smaller.

Here is a graph of the sunspot cycles, recorded until now. It looks like we have passed the Modern Maximum and are going to a minimum. Are we heading to a new “Little Ice Age“?  As I wrote in an earlier post, this is a sensitive issue, and I will not comment on it..:-). Be very wary when you search the Internet for info  about a relation between solar activity and global warming. Always check the credentials of the report. You might try this site: Skeptical Science


Here is a dramatic image of our Sun, taken by the Solar Dynamics Observatory. Magnetic field lines are superimposed.



Rosetta is still orbiting comet 67P, which has passed its perihelion and is now on its way out into deep space. Here is the position of Rosetta and the comet, end of last year, the comet has passed already the orbit of Mars. No signals of the comet lander Philae have been received anymore, but Rosetta itself is still active.


Here is a recent image of 67P, taken on 27 March, when Rosetta was 329 km away from the comet nucleus. The Sun is behind the comet, with a spectacular result.


The scientists are planning to let Rosetta make a controlled landing on 67P in September 2016, which will be the end of the mission. You can find the latest news on Rosetta’s blog


Dawn is still in orbit around dwarf planet Ceres. Slowly getting closer, resulting in more detailed pictures. You may remember the excitement about the bright white spots. Now we know that they are located in the center of a crater, which has been given a name: Occator. More (smaller) white spots have been found


Here is the most recent picture (in false color), taken 30-3-2016 from an altitude of 385 km. . Spectacular. Scientists now think that the white spots are formed by highly reflective material, possibly ice or salt.


Actually Dawn is taking pictures of the whole surface of Ceres. Scientists have been busy giving names to the various features..:-)

Ceres mapping

For more information about Dawn, read this detailed blog So.Much.Ceres, published a few weeks ago

New Horizons

On 14 July 2015, the New Horizons spacecraft passed Pluto at an altitude of 12.500 km above its surface. It took as many pictures during the fly-by (of only a few minutes!) as possible and it still has not finished transmitting all the data to Earth!

Here is one of the images, released a few days ago. It shows numerous “haloed” craters. The false-color image gives the composition: purple is methane ice, blue is water ice. Why the crater rims and walls consist of methane ice has not yet been explained.

Craters on PLuto

New Horizons is now on its way to the Kuiper Belt, where it is supposed to flyby one of the Kuiper Belt objects, 2014 MU69 , on 1-1-2019.  Here are the present locations of the New Horizons spacecraft and 2014 MU69


Planet 9

We have reached the outskirts of our Solar System. Pluto, once the 9th planet, has been demoted and is now considered a dwarf planet belonging to the Kuiper belt. Recently more dwarf planets have been discovered in the region beyond Neptune,  Eris ( in 2005) , Haumea (in 2004) and Makemake (in 2005)  Like Pluto they have quite elliptical  orbits and periods in the range of a few hundred years. Pluto for example has a period of  248 year and its distance to the Sun varies between 30 and 49 AU, where 1 AU (the average distance between Earth and Sun) = 150 million km. The orbits of these dwarf planets have been strongly influenced by big neighbour Neptune.

In 2003 dwarf planet Sedna was discovered with an estimated period of 11.400 year and a distance to the sun varying between 76 and 936 (!) AU. Here is the orbit of Sedna. Pluto’s orbit is purple.


What could have caused such an extremely elliptical orbit? It can not have been gravitational disturbance by Neptune, because it never comes close to Neptune (distance of Neptune to the Sun is 30 AU).

In the last decade more of these “strange” objects have been discovered. For example in 2012  2012 VP113, estimated period 4200 year, distance to the Sun between 80 and 438 AU, also very elliptical.  Here the orbits of six of them are given.


Could these orbits be gravitationally disturbed by an UNKNOWN planet in the outer reaches of the Solar system?

On 20 January 2016 astronomers Brown and Batygin published an article in the Astronomical Journal: Evidence for a distant giant planet in the Solar System (abstract). Using computer models, they find that a planet with a mass about 10 times the mass of Earth, a period of 10.000-20.000 year, and a distance to the Sun varying between 200 and 1200 AU, could explain the orbits. Tentatively this planet is named Planet Nine .

Here is a sketch with the position of this Planet Nine.


Of course this is a hypothesis until now. Other explanations are possible. Next step is to try and find Planet Nine. That will not be easy, even for the most powerful telescopes. And where to look for it?

Here is a picture of the two authors, both astronomers from Caltech. By the way, Brown (left) is  the guy who discovered Eris, which started the demotion process for Pluto!

Brown & Batygin

They have started a website The Search for Planet Nine and just submitted a (highly technical) paper in which they discuss where to search for this planet.

If Planet Nine is ever found, I will not be surprised if they get a Nobel Prize for their research.

Close encounter with Pluto

In an earlier post, Close Encounters , I mentioned three memorable astronomical events in 2015. One of them was the flyby by the New Horizons spacecraft of the (dwarf) planet Pluto on 14 July at 11:49:58 UTC  (7:49:58 pm Malaysian time)

One day earlier, when the New Horizons was still a respectable 800.000 km away from Pluto, it took this picture.The heart-shaped region, the smooth surface, caused already much excitement


New Horizons was approaching Pluto at a speed of ~ 50.000 km/h, so the flyby was near. At this high speed the observation window for taking close-up pictures was narrow. It was decided to stop communicating with the spacecraft during the flyby, as the on-board computers would be busy collecting data. There was a lot of tension in the control room during the blackout. Here is the response when the first signal of New Horizons after the flyby is received. Mind you, it takes about 4.5 hours for light and radio signals  to cross over form the spacecraft to Earth, as the distance to Pluto is about 5 billion km at the moment.


This first signal was only a sanity signal that everything was working normally. Transmission of the images is a time-consuming process. It was only the next day that NASA published the first detailed image. nh-pluto-surface-scale

Many surprises. The surface looks very smooth, scientists think it can not be more than a few hundred million year old. Has Pluto still an active interior? And there are mountains, up to 3 km high. They might consist of water ice.

A second picture has been published today, details of Pluto’s (principal) moon, Charon.


More excitement. Impact craters here, but what is this strange feature in the top left corner? More pictures will arrive and hopefully be published in the coming days. But the analysis will take months if not years.

New Horizons has done a marvelous job. It will now pass through the Kuiper Belt and leave our solar system. You can follow the spacecraft on the New Horizons website

What about the two other events?

Dawn has successfully entered orbit around Ceres and is still observing the asteroid. The white dots on its surface have not yet been explained. Here is a collage of images taken by Dawn. The Dawn Blog is still online and active


Finally Rosetta and Philae

Rosetta is still orbiting comet 67P, which is now on its way to perihelion, the closest distance to the Sun. Perihelion will be reached on 13 August. Already the comet is feeling the heat of the Sun and partly evaporating. This picture was taken on 7 July


Mixed news about Philae. There was huge excitement when it came out of hibernation on 13 June and “talked” for a few minutes with Rosetta. But after that, communication has been intermittent, for reasons unknown. However, ten days ago, Philae has contacted Rosetta again and actually transferred data from one of its on-board experiments! The scientists are hopeful that it will get more active the next few weeks. Read more on the Rosetta/Philae blog

I will update this post when more  news/pictures become available

Update 18-7-2015

Yesterday NASA published another picture, a detail of the heart-shaped area , which has been provisionally named Sputnik Plain. Some features have been identified. This icy plain can not be more than 100 million old. More details here


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..



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.



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.



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!):


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?



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.



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.


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.



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!



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.


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


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 ?


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.


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.


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


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.


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.


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.


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


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…:-)


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 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


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.


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.


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!


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..:-)