Why do stars twinkle (and planets not)?

Hi,
I felt so embarassed that I finally had to find it out and now I am writing this short post about it. For few years, roughly, I am studying astronomy yet, I never knew why stars twinkle and planets not. I confess.

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Stars twinkle because the light that reaches us goes through atmosphere and atmosphere is not very homogenous – smooth. Air refracts light and there is different temperature once in a while, humidity and so on, I think that lot of factors play the role. This causes the light of star to scatter a bit and creates the twinkling effect.

Planets do not do it. This is great because you can identify them extremely fast on the sky and you do not mistake them for some other bright star. Why? Their light still goes through atmosphere. Because they are not “point sources”. Stars are so far away that even with best telescopes we see them only as points. Planets with simple telescope on backyard already have shape. Some of their light scatters one direction, some the other and it basically cancels out creating nice image. This is also why it is better to go star-gazing in the winter, colder air does not create so much “noise” on the picture.

Dragallur

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Space NEWS #10 (Very close exoplanet)

Hi,
today I am bringing news about the closest ever found exoplanet that is also potentially habitable. This planet is orbiting Proxima Centauri, the closest star to Sun.

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This is great news. Like really, what is the probability of finding one of the best candidates for Earth like planet closest to us that it could get. But to be clear of what is really going on, it is not as that we are going to get a picture of it. Not at all, we do not even know its size (is probably above 1.3 of Earth’s) or anything about its composition. Its just that it is very very likely that the planet is there because of Doppler shifts and other fancy astronomical tools that enable scientists to discover exoplanets.

No, this is not how the planet looks like.. but yay! Random artistic pictures!

Proxima is red dwarf. This means that it is smaller and cooler than Sun. The difference is so huge that the planet may be in habitable zone even though it is probably only 7.3 million kilometers away compared to Earth’s 150 [1]. So if there is water it may be liquid but nothing is very sure. If there are some greenhouse gases it is probably warm enough.

Before leaving, just check out this cool comparison of the angular diameter (size) of Sun and Proxima from Earth and from the new planet (Proxima b):

Yes, any life on Proxima b would have much bigger and redder star to look on.

Dragallur

Check out these two pages for more info: 1) 2)

[1]Proxima has surface temperature of 3050K, 0.1 percent of SOlar luminosity, radius 0.14 and 12% of Sun’s mass.

Planets of our Solar System: Neptune

Hi,
here it goes, here it comes the last post for the series: Planets of our Solar System, maybe if you discover new one I will mention it.
Ok so today I am going to write about Neptune, the eight planet of Solar System, you will see how much we now about thing which is so far away, lets go!

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As I said, Neptune is eight planet and the last once since Pluto is no longer considered to be planet (I will make sure to write epitaph about him).

It was discovered not by accident but by math. When Uranus was discovered and its motion across sky was calculated astronomers saw that it is not on the place where it should be. This was because of Neptune which is influencing Uranus. This happened in the year of 1846 and was discovered by Johann Gall and astronomy student Louis d`Arrest.
Neptune was named after Neptune, the roman god of sea. Greek equivalent is Poseidon of course.
Neptune orbits at the distance of 4.5 billions kilometers. Its radius is 25,000 km and he is little smaller than Uranus but much denser.
He gets 1\800 of the Suns energy as we do and as other gas giants in our Solar System he is radiating more energy than recieving, 2.7 times more.
Interior of Neptune is similar to Uranus`s.
The core makes up two thirds of the planets radius and is made up of rock, ice and some iron and nickel silicates.

Mantle is similar to Uranus`s and there are also probably small diamonds created from methane molecules.

Atmosphere is made up of hydrogen and helium but because Neptune is ice giant there is only  80% of hydrogen and 19% of helium. There is also methane which creates the same effect as on Uranus, it absorbs red light which makes the planet blue. Atmosphere also makes 5 to 10 % of planets weight.
The atmosphere is much more violent than Uranus`s. There are frequent storms and as far as I know they (not counting solar winds :D) are fastest in Solar System.. 2000 kmh. When Voyager 2 flyed around Neptune it saw a giantic storm in its atmosphere. It was similar to Red Giant Spot which is on Jupiter. It was called Dark Giant Spot and it soon dissapeared but some other stormy features appear often (You can see it on the picture).
On the surface is temperature higher than on Uran, about -213°C.

Neptune has magnetosphere and it is as strange as the one on Uranus. It is moved by about half of planet`s radius which astronomers think can be feature of all ice giants. Neptune also has aurora.

There are 5 known rings of Neptune and 14 moons about which I will talk  in future episodes of Moons of our Solar System, so stay tuned.

Dragallur

Pictures taken from wikipedia and http://astronomy.wikia.com/wiki/Neptune_Project and http://spaceplace.nasa.gov/review/solar-system-scramble/scramble-text.html

Planets of our Solar System: Uranus

Hi,
today lets see some stuff about Uranus!
Uranus was named after the god of sky. It is third largest planet but fourth in mass.
It is special type of gas giant: the ice giant. The difference between him and Saturn and Jupiter is that there is only 83% of hydrogen in its atmosphere.

Uranus was discovered by William Herschel. It is actually the first discovered planet. It is called discovered because it was not known in ancient times and it took a guy and telescope to find him. Some people found Uranus before William but they did not notice the strange movement and marked him as star. Uranus lies right on the edge of visibility by naked eye with apparent magnitude about +5.7 or so.

The interior of Uranus is very specific. There is outer atmosphere as you can see on the picture. There is lot of methane which makes Uranus look blue, methane absorbs red light very well. To see some cool stuff with methane, click here.
It continues to mantle where is water, ammonia etc… by astronomers those things are considered to be ice stuff, which is as strange as that everything else than hydrogen and helium to be considered metal.
Very important is that ice giants don`t have metallic hydrogen inside. The inner core is made up of mostly rock, it is about half the size of Earth.

Because of low inner heat of Uranus there are not many features in the atmosphere while sometimes some clouds and storms appear there. Speaking of storms, there can be winds which have the speed of 900km|h, which is hella lot!

Uranus has magnetosphere. Also very strange because its center is moved by third of his radius. Uranus has probably the strangest rotational axis of all planets in Solar System. It is turned by about 90° as you can see on the next picture.
Astronomers are not very sure why this is, maybe because of some huge impact. On the picture you can see the planetary rings of Uranus. There is 13 of them and they are really thin.
Uranus also has 27 found natural satellites which are named after Shakespear`s characters.

It takes 84.07 years him to go around Sun. Day there is shorter than on Earth with little over 17 hours. The usual distance from Sun is almost 3 billions kilometers or about 20 astronomical units.

Under the thick atmosphere there is a huge pressure which can brake methane molecules appart and form diamonds.
There was only one mission to go around him and it was Voyager 2 so we dont know so much stuff about him.

Dragallur

Picture are taken from Uran czech wikipage.

Planets of our Solar System: Mars

Hi,
today I am getting to fourth planet of Solar System since I skipped Earth.
It is Mars, The Red Planet.

Mars is very pretty planet. There are actually nice conditions, really the best for us if we are not counting Earth of course. This makes Mars very kind of nice for research and everything.
We are able to see him in the morning below Venus but it is not really bright. Still if you have good eye you may be able to see the reddish color of its surface, I will get later to it.

Mars orbits 1,52 AU from the Sun. The difference between closest and furthest distance from our star is over 40.000 km compared to Mercury´s 23.000 km and Jupiter´s 76.000 km.

You wont get overheated very much on its surface, there is average temperature about -60°C. Surface color is red, right you guessed it and it because of iron oxide (hematite). It also makes sense that people named it Mars, after roman god of war (Greek version is
Ares).

There are two main things about physical geography “up” there. Some time in the past Mars collided with huge rock
which made crater over whole north part. Same on the Moon, lava could easily bubble up through thin crust and smooth everything out (as a proof you can see it on the picture). While on the south there are lot of impact craters.

When you see this map immediately your eye moves to huge red spot on the right, those are mountains, actually volcanoes with tallest mountain in the whole Solar System: Olympus Moons which is 27 km tall with surface area about the size of France. This one and also other volcanoes were made when tectonics of Mars were still active.

Really cool thing is in the middle of map, such a small blue line cutting few kilometers to earth. It is Vales Marineris (picture is from Celestia).
This canyon is crack which was made when the crust was cooling. It is 4000 km long, 200 km wide and 7 km deep.

Water on Mars
You have probably heard of it and I will make sure to make separate post about it.
So yes, NASA found liquid water on Mars. Problem is that it is full of soil so you can call it water, yes but it is more kind of mud which is flowing from season to season with its low freezing temperature. There are also polar ice caps on the poles with little water on them and mostly dry ice (CO2).

Even that Mars has atmosphere, it is extremely week and when it is winter on Mars one third of it is in solid form on surface.
Scientists are sure that there was liquid water before (even oceans) but it evaporated and solar winds blew it away because Mars´s gravity was not strong enough to hold it (Mars has only 0,3G).

Mars has two moons but I will talk about them in different episode since I made this: “Moons of our Solar System” thing.

Dragallur

I also wrote about visiting of Mars

Previous post about Mercury
Previous post about Venus

Civilizations: Dyson´s sphere

Hi,
Again I will write about civilizations but this time only about Dyson´s spheres which I mentioned before as a thing which would be used by civilization of type II and type III.

Because there is high probability of all civilizations using energy, we assume that all “worlds” will need more and more energy as their population grows.
At one point there wont be enough energy on its home planet. They/we will need some source of energy which would be kind of permanent. Here comes this Dyson´s sphere because it is a sphere which surrounds home star and collects its energy.

First there are smaller types of Dyson´s sphere like a Dyson´s ring. It is ring of objects sharing the same orbit and collecting energy of star. They would transfer the energy by wireless power transfer.
Expansion to ring is swarm which is lot of rings around star. BUT those ring´s orbit would intercept each other so it would be really difficult to avoid some crush.
To solve this you would have to have statellites instead of satellites. Those would be objects which would be stationary and they would not orbit the star. Those things would fight with gravity by large sail which would be pushed away from the star by solar wind. BUT this sail would have to be extremely light.. when I say extremely I mean very extremely because paper has 80g for squared meter and this sail would have to be about 0.7g for m^2. This would require ultra light nanotubes.
Last type is sphere which would collect almost all energy made by star. It would be extremely difficult to stabilize it and collect all the material.

Dragallur