Europa Multiple-Flyby Mission

Hi,
today I am going to write about proposed mission to investigate Europa.

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Europa Multiple-Flyby Mission is a plan consisting of orbiter and a lander directed towards Jupiter‘s moon.

The reason why to choose Europa is quite clear. There is probably liquid water under its surface and if one launches such a thing, it might get public’s attention.[1] (Which might be now more important than ever considering how Trump wants to cut down NASA’s budget especially on the most important thing that they do: Earth’s climate monitoring.)

First of all the orbiter, which would be launched in the next decade, would learn as much as it could about the surface of the moon, Jupiter’s magnetosphere (see later), weird water

This is two images of course. The original does not have the Europa in middle but only black spot. You can see the plumes on roughly 7 o’clock.

plumes and so on. There are 9 instruments together planned.

Instruments on those orbiters are able to collect data faster than we can receive it. This is because there are more mission that need attention of our receivers. Those are not some small receivers but specialized ones and all missions have some time to send information. For example New Horizons, just from its flyby of Pluto kept sending data for some 6 months.

In case of Jupiter oriented mission this might be a problem because Jupiter has extremely strong magnetosphere which will probably damage the instruments in matter of few weeks. This way it is best to get close to Europa and then get away as soon as possible and send the data later. This can not be done for the lander so it really lasts in matter of days. (Yes, it is still a problem even if you cover your equipment under 150 kilograms of titanium as is planned!)

The lander is thing planned even further into future, around 20 years or so. Much can change and we will see what the priorities are at that point.

Dragallur

[1]People will probably get quite excited by mission promising founding signs of extraterrestrial life.

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What does the 3rd Kepler’s law say?

Hi,
today I want to do a short post about the 3rd Kepler’s law. I kind of really like it because it has very simple explanation but lot of uses at the same time.

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The law goes as follow:

T stands for time and a for semi-major axis of ellipse, that is basicly radius for planets since

What is semi-latus rectum?

their orbit is highly circular. The index 1 and 2 stands for first and second object, basicly you are comparing two objects with each other though they must orbit the same body. This is very useful since you can compare anything in Solar System orbiting Sun with Earth. Why is it useful? Because Earth’s semi-major axis is 1AU and orbit lasts for 1 year which means that this fraction will disappear and you are left only with the object you want to calculate with.

Where did this even came from? The prove for this equation is very simple and basicly stands on the fact that centripetal force equals gravitational force for our orbiting object.

Fg=Fc

We can find the equations for both of these forces and from them finally get to the Kepler’s law:

Ok, before you start to freak out, this is completely easy. First line is clear, I have accidentaly indexed Fd instead of Fc because in Czech the force is called “dostředivá”.

Second line shows the forces and their equations, third canceles the mass of the orbiting body and the radius of orbit. Since v=s/t we can write it down as is shown. Also watch out because s is whole orbit so s^2=4π^2

The equation that you have in fifth and six line is also usable equation! It is more general and does not need the second orbiting body but it needs the mass of object. From this equation you can also figure out the mass of Sun which is completely amazing! (You have to watch out for the right units!)

After the small space I have divided the equation by the same one except that it works with some other object orbiting the same star (or planet..), with this step I will get easily rid of all the π, gravitational constant and mass of the center object.

Now we have the original 3rd Kepler’s law!

Dragallur

PS: in the prove we also assumed that r=a which means that planets orbit on circles not ellipses but it is accurate enough

Moons of our Solar System: Thebe

Hi,
continuing in the promised series about moons I will today cover the satellite Thebe, this time I even have some “high resolution” pictures so keep on reading!

There are few huge craters on Thebe. (largest is Zethus with diameter of 40 km)

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Thebe is another Jupiter‘s moon. It is quite smaller than Amalthea, with 100 kilometers as mean diameter. It was named for Greek nymph, in both stories I found, she was lover of Zeus (yet again) but in one she was also the daughter of Egyptian king.

It is quite similar to Amalthea, again it is tidally locked, which means that one side always turns toward Jupiter (this is also true for Moon). The surface is probably red what you can not see on black and white pictures of course. We can estimate its mass only based on the similarity with Amalthea, the value you will get is roughly 4*10^17 kilograms.

For the first time its image was taken back in 1979 by Voyager. Later, Stephen  P. Synnott found it on one picture. Four years later the name we use was first used.[1]

The fact that it is blurry wont help you much.

The above picture is the first sign of another moon, but watch out, this one is only shadow.

In background you can see some huge storms on Jupiter.

Another picture of Jupiter but this time Thebe is really visible! (Yeah it is not just filth on you monitor).

Finally, Jupiter has faint rings. These rings have to made up of something. Usually rings are created when some rocks are ripped apart by tidal forces. Also they can be fed over long periods of time be debris that leaves some moons.

Thebe has one very faint ring which is created by the second method. It is three times fainter than the ring of Amalthea which is very faint too. It has diameter of 65k-113k kilometers and it is not so thin (8400 km) as the Saturn’s rings which are even only several meters tall.

Dragallur

References: 1) 2) 3) 4) 5) 6) 7)

PS: the second and third pictures were taken from the same site and official permission should be needed only for commercial purposes, which is not me.

[1]S/1979 J 2 was the original name, though I did not decode it it probably means S=satellte 1979=the year it was found J=Jupiter 2=probably second in row with this designation.

Moons of our Solar System: Himalia

Hi,
it has been about 4 months since I last posted about moons. The last post was about Amalthea (pretty cool name huh?). I thought that maybe I should resume some of the series so lets see how it will go. (its mostly astronomy blog so no wonder that these things are here.)

If I count right, Himalia has 29 pixels!

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Last time I was talking about Jupiter’s moons so I will continue with those. Today the topic is Himalia.

As you could guess, this name is connected to Jupiter (Zeus in Greek mythology). Most of the time all the people (moons) are lovers of Zeus and Himalia is no exception, she was the nymph that brought 3 sons to Zeus, those were Spartaios, Kronios and Kytos.

Though I found that she is good for watching I highly doubt this since the apparent magnitude (how bright it is) is only 14.6 which makes it almost as visible as Charon, the moon of Pluto (15.55).

Himalia is the largest irregular satellite of Jupiter. To be irregular satellite means to be formed somewhere else and be captured later on by the planet. Such moon has highly eccentric orbit which is also inclined and even retrograde. She orbits much further from Jupiter than the other moons I talked about. The distance ranges from 11-13 million kilometers! This is one 15th of the distance of Earth to Sun which is quite a lot for a moon!

Since there are many other objects around Jupiter like Galilean moons that are easier to study (also more interesting) not many missions studied this piece of rock. It was discovered on 3rd December of 1904 by Charles Dillon Perrine. We know some things from spectroscopy, it is similar to C-type asteroid which means that it contains minerals with

Not so good either

water though otherwise such an asteroid is pretty dark. While Himalia is small compared to planets, it has masss of 4.19*10^18 [1]. It’s diameter is not very clear because the closest pictures were taken millions of kilometers away. There are basicly two pictures of this moon, one which you can see above is by Cassini-Huygens and second is by New Horizons (on the right).

It was thought that Himalia has something to do with the disappearance of other even smaller moon Dia when it disappeared in 2000. Dia was luckily found in 2010 so Himalia is innocent.

Dragallur

[1] This does not mean that Himalia is heavy in Solar System, Earth has roughly 6*10^24.

Green trail, golden leaf!

Hi,
this is very abstract title I guess but it summarizes why I did not post last Saturday when I planned, yes I am sorry. Anyway I was on this contest called Green trail, golden leaf which is contest of mostly biology though there is also astronomy, meteorology (not this year) and geology. I was not contestant for the first time, but organizator and I helped with astronomy site.

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There are two categories which are basicly for older (10-15) and younger (0-10) kids (numbers are rough). The contest happens in groups of 6 people. They are then walking the trail three at a time, getting points on various sites on various topics and finally their points add up.

In Friday I had actually presentation first. I was pretty happy how I did it except that it was a little bit too long. The problem was that even that the presentation was for roughly 50-60 minutes the kids were discussing and asking questions a lot (which made me happy of course) but finally the presentation was roughly 100 minutes.

I was talking about the view on Earth, geocentrism, heliocentrism, no centrism at all and why the Universe is so big and why people usually think it is not. I followed up with aliens and Fermi paradox, of course wow signal and KIC xx… were also mentioned. In the end I mentioned SpaceX, terraformation of Mars, New Horizons and Voyager.

As I said the presentation was going pretty good as well as the contest itself. For younger kids we had questions like:

1. Name 3 astronauts
2. What is astronomical unit and what is light year
3. Name 3 missions (Apollo and other count as 1)
4. Name 4 constellations that are visible in Czech Republic
5. Highest mountain in Solar System and where it is
6. Where do comets come from?
7. Difference between meteorite, meteor, meteoroid and asteroid.
8. … (and other)

 

For older it was bit more difficult:

1. What is afelium and perihelium
2. Name all Galilean moons and give a small info for one of them
3. What is HR diagram
4. (Lot of pictures about life time of star)
5. Draw the orbit of typicall comet and draw both tails and name one place where they come from.
6. … (and other)

From 12 sites astronomy was the 2nd toughest 😀

Lets see how would you do, I will return to it some other post.

Dragallur

Moons of our Solar System: Amalthea

Hi,
today I will write about another moon of Jupiter. This is surely not known to larger community because it is much smaller than the Galilean moons. I would like to say that it is beautiful as her name which I really love but the images of its surface are kind of blurry.

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Totally beautiful:

Amalthea was discovered in 1892 by E.E.Barnard (that guy after whom Barnard’s star is named after [1]). What this tells about it? Well it has to be quite big because back then the observations were not so good yet.

It was named after Amalthea, the Greek nymph who nurse Zeus, so once again it has to do with the planet it orbits.

Orbit

Amalthea if part of one ring of Jupiter, this one is called Gossamer ring. It is orbiting as 3rd satellite from Jupiter as far as we know, at the distance of roughly 181,365.84 kilometers, there is practicly no eccentricity in its movements and it take almost 12 hours to complete one spin. Some of those strange features can be explained by the moon Io.

Surface

When I said that it is not small I really meant it: 250 x 146 x 128 kilometers does some stuff. It does not have any geological activity as Io so its surface is heavily covered with craters.

There are some huge ones on its surface which were surely made by violent impact probably changing the orbit of the moon a lot, you can see them on the picture.

Otherwise there is not something too special observed about the surface of the moon, it is cold place but we still have a lot to search there.

The ring in which she orbits is made from her because Jupiter is reaping dust from its surface.

When person would stand on its surface it would see enormous Jupiter over 40° of sky. The gravity there is not so strong compared to our Moon but still great: 58m/s. Jupiter would also be very very bright, 900x brighter than Moon when it is full.

Dragallur

[1] Check out my page about Daedalus mission!

 

 

Moons of our Solar System: Io

Hi,
it has been couple of posts since I last wrote about moons ofour solar system. Today I will write about the last Galilean moon: Io.

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Io is kind of hellish world. With extreme temperatures and extremely poisonous chemicals, everywhere. Still it has suprisingly beautiful colors and this piece of strange rock is very important component in Jupiter‘s system, lets see why.

Io was with the rest of Galilean moons found out first by Galileo and Simon Marius who gave her the name: Io which was pristess of Hera. She was also Zeus’s lover as it happens frequently.

Surface

The picture which is above is taken in true colors and there is yellow red and brown because of certain element. You probably remember this one: sulfur.

There are also various kinds of silicates, this is stuff that contains silicon. Otherwise sulfur dioxide and all other various compounds.

What really suprised scientist when they saw the surface for the first time was that there were and are not many craters. They wanted to date how old the moon is but it surpised them what they found. The surface is in this feature similar to Earth. There are almost no craters because of its geologic activity (othewise rare) which transforms the top layers all the time.

There are more than 400 active volcanoes. Io, is the most geologicly active thing in whole
known Solar System.

There are roughly 150 mountains on the surface ranging to even higher heights than Mount Everest. There are not very steep because there is a huge erosion causing stuff to smooth out. Those mountains were created by the push of the litosphere going down while some parts went up. There are also special features called paterae. They are similar to what on Earth we call caldera which forms as you can see on the right.

This particular picture shows the formation of Crater Lake in state of Oregon, I have been there and I must say that it is something extremely beatiful!

Otherwise the surface is cold, about -143°C but there are some areas around volcanoes which are heated up to even 17°C.

Observation

For a long time humans just saw Io as a point in the sky with magnitude of 5. It took the first probes to actually observe something about it except roughly the color.

Pioneer 10 and 11 launched in 1972 and 1973 respectively were the first probes to collect some data.

After that famous Voyager 1 and 2 did another flyby collecting even more data followed up by Galileo and New Horizons.

Orbit, size and atmosphere

The orbit of Io is in resonance with Ganymede and Europa as I already mentioned before. This creates tidal heating through friction causing all this geological activity. Io orbits as fifth moon from Jupiter but it is the closest one of the Galilean moons. This means roughly 421,700 kilometers and one orbit takes 42.5 hours, the moon itself does not rotate because it is tidaly locked to Jupiter.

Io is just a little bigger than Moon, by about 5% which means diameter 3642,6 kilometers but far greater mass (+20%). Io is very dense moon.

There is even atmosphere but it has the pressure of about one billionth of our atmosphere. It is mostly composed of oxide disulfide. If some probe would land there it would not be able to use parachute and it would not need heat shield to prevent from burning. To slow down, it would have to use its rocket nozzles.

What is really interesting is that it interacts with Jupiters magnetosphere which takes out about one ton of material from Io. Io also works as giant generator creating electric field which would kill human in matter of minutes with the power of 400,000 volts and 3,000,000 ampers.

Dragallur

Io picture
Caldera picture

Moons of our Solar System: Callisto

Hi,
here it comes, here it goes after a lot of other posts I have decided to write again about moons and this time I continue to really cold piece of giantic rock and 2nd biggest moon of Jupiter and 3rd largest in whole Solar System right after Titan. It is Callisto not The Spear of Vengeance.

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Callisto was found with other Galilean moons by Galileo Galilei and independently Marius. Marius gave her this name. Instead of Callisto, Jupiter IV was used. I am really glad that it changed.
Callisto was one of many lovers of Zeus or Jupiter for Roman`s.

As you can see on the picture below, Callisto is really just a little smaller than Mercury.
It is smaller just by few kilometers but it has just a third of Mercury`s weight. As you can see it depends a lot on the stuff from which the object is made.

Callisto orbits at really big distance. 1.88 million kilometers which is almost 1/75 of the distance between Sun and Earth. For moon it is a big number, more than 4 times between Moon and Earth.

It is actually very important that it is so far away because the rest of the Galilean moons are orbiting in resonance which means that they are creating heat in their interior because of friction of the liquids inside.

Callisto can be described as very cold and hard place. There is no volcanism or tectonic activity on its surface to smooth all the features. But there are also no mountains since they are caused by tectonic activity.
Only things you can find there are craters and there is lot of them. Actually the number can not increase a lot because they will almost always overlap so the ones that are old will erode and disappear.

Crater which you can see on the right is called Valhalla crater and this one is the largest. The middle is only 600 kilometers wide but with the rings from the rest of the collision you can say that Valhalla has 1800 kilometers. Another huge guy is Asgard with 1600 km.

The surface is very old and also very cold with temperatures oscillating between -130 and -190 degrees of Celsius.
Most of the surface is covered by water ice.

Under the surface it is assumed that there is thick salty ocean.

Callisto has really thin atmosphere which is made up of carbon dioxide which is the same for Mars. The atmosphere is actually so thin that it has to be powered from dry ice which is evaporating from surface, otherwise it would disappear completely.

There is mission planned to go for Galilean moons in 2020. It is called Europa Jupiter System Mission and it would be founded by NASA and ESA (European Space Agency). More than Callisto, Europa is the moon of interest since there is much higher probability of live because there is this heat from friction.

Dragallur

1st and 3rd picture
2nd picture

Why is the Moon so strange?

Hi,
here it comes, here it goes. Today I will write about the strange shape of Moon which is actually pretty normal and you probably saw it some day, of course I mean that the strange thing is that it is “turned” by 90° degrees. I saw it yesterday/today during flight from Rio de Janeiro to London. It was very difficult for me to imagine the position of Moon, Earth and Sun to create this. But today I have downloaded Stellarium which seems to be pretty awesome and now it is clear to me so I will try to explain it.

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Fine, the problem is the rotational axis of Earth. It is tilted by over 20°. This means that when you are standing on equator you are moving by a huge distance up and down like on rail coaster during day and night (this changes your point of view on the Moon so the lighted part seems to change). When you are far away from equator you are not moving that much. Parallel are not so long, the difference is less and less and when you get on pole it is not moving at ALL! By this move I mean rotating of the part of lighted Moon through its journey since from our point of view Moon seems to be lighted from different sides throughout the day.

Well it was kind of hard for me to find the right words but you can always ask in the comments.
Dragallur

Source of 1st picture: https://10minuteastronomy.wordpress.com/category/sky-motions/

Planet classification

Hi,
here it comes, here it goes. Today I will write about planet classification since I want to start to write about dwarf planets. This post will be little similar to Stellar classification but you will see that for planets there are not those classes for size differences. The most important thing is of course to know what is planet and what is not, which I will explain.

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Ok in the year of 2006 International Astronomical Union anounced that Pluto is not a planet. It`s been almost ten years but I still know people that can not get over it. I know this picture is sad (and not to scale).

For now the definition go as follows:

Planet has to be orbiting Sun
Have to be generally spherical
Has to have enough strong gravity to clear its orbit.

So the thing is that Pluto can only check first two criteria but not the third so such a object is called a dwarf planet.
Also you can see that planet is only object that is orbiting Sun which as it seems is not any exoplanet. This means that those 2000 planets that we found are just a huge objects, but for the official definition they are not planets either. And.. because they are so far away, it can not be known yet if they are spherical or not.

You can see that those definitions are not very good but luckily one guy on some conference proposed new definition which is not yet agreed to be new one but anyway International Astronomical Union will have to make a better one which will be probably very similar to this:

Planet has to be orbiting at least one star or the remains of one. (So yeah, stuff that is orbiting white dwarf is still a planet if it meets the other criteria. Read about multiple star systems)
Planet has to have a clear path to itself. (Sorry Pluto.)
Planet has to have mass lower than the mass of Jupiter. (This is good so we dont accidentaly name brown dwarfs as planets.)

Now we know what are planets. Lets move what are dwarf planets. Those are the objects that are not able to satisfy the third rule, their orbit around Sun is not clean. Dwarf planets are: Ceres, Pluto, Haumea, Makemake, Eris and Sedna for example.There are some other candidates also.

There is type of objects that are called minor planets. Those can be at the same time dwarf planets, like Ceres. The number of minor planets is increasing by very large amount every month. Only few of them are named, large part is numbered and there is  rest for which we dont even know exact orbit. Together there are almost 700,000 minor planets.

I did not find exact definition but minor planets should be those that are orbiting Sun, that is about it. They dont have to have any particular size, shape and their path can be trafic jam of asteroids. Actually yes, the asteroids are minor planets and also all the trojans and so on.
Above you can see all the types of objects that can appear in our Solar System except Sun.
Thats about it, I will definitely make post about or more about asteroids, comets and of course I will be continuing with moons.

Dragallur

Pictures are from wikipedia pages: IAU definition of planets, Minor planets and Dwarf planets and the first one is from this page: