Orbital period

Hi,

in today’s short post I will write about orbital period of planets, more accurately synodic and sidereal period.


In the post about year and how difficult it is to determine how long it is, I mentioned that there are some ways you can measure the time it takes for planet to orbit star.

Sidereal period is the time it takes for Earth or other object, orbit once with respect to distant stars.

Now distant stars are great because they tend to be on the same spot most of the time. For example on the Voyager plague there is a map to show the position of distant pulsars, why? Because such things are stable, easy to see and far away. For year we use stars in Milky Way which is still fine, most move by fractions of arcseconds every year which is something you can not notice with eye and has some effects in thousands of years.

Sidereal period of Earth around the Sun is 365.25636 days. (I wonder if you could talk about something like sidereal period of Sun around the center of Galaxy, probably yes)


Synodic period is about two bodies orbiting Sun for example. It is the time that it takes for the two objects to get to same position. So if Mars and Earth are right behind each other (which is called opposition), synodic period is the time it takes for it to happen again. Now of course both planets orbit and the faster one (the one closer to Sun) always has to make at least one revolution. When that happens it just needs to catch up with the slower planet. With this simple thought you can come up with equation that lets you calculate the synodic period:

1/S=1/P-1/p

(lower case p is the sidereal period of the object with longer period)

Thats about it for know, enjoy your winter holiday while/if you still have it!

Dragallur

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.


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):

Sun and Proxima compared

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.

Juno has some real party instruments!

Hi,
as I promised, today I will write about instruments that Juno has acquired for the journey to Jupiter. Also I wont post anything for something like two weeks again because I am going with my mum and sister to Poland on vacation. After that I will be few days at home and then I will go to Germany for one year (of course I will start writing again at that time).


Juno is very well prepared to gather some data, here are all the things that Juno is capable of:

Gravity measurements

To measure if Jupiter has solid core or not scientists are going to measure Doppler shift of radio waves transmitted back to Earth. The changes of gravity from computed should be from either storms if they go very deep into the atmosphere and/or changes of density and surface of the core if it exists.

JADE – Jovian Auroral Distributions Experiment

Those are three detectors that each covers 120° + one special detector that has 270° view. This experiment is trying to observe the auroras of Jupiter by measuring the charged particles that create them.

JEDI – Jupiter Energetic Particle Detector Instrument

Right this does not correspond to the acronym but you know.. Jedi 😉

This experiment is similar to JADE except that it consists of only one detector and detects particles with lower energy.

JIRAM – Jovian Infrared Auroral Mapper

Again this one watches over auroras but also it makes infrared images of the atmosphere.

JunoCAM

This is somewhat unnecessary camera that is going to collect pictures for public. There was even voting for what pictures it should take because it wont have so much time. As I said in the last post it is going to have some cool resolution but we will have to wait about month for it.

Magnetometer

Juno also has magnetometer that will measure the strength of the magnetic field and its other attributes. It is quite big instrument with 3.6 meters height.

MWR – Microwave radiometer

Such thing was not used before on Jupiter so it could be huge surprise what we will see in microwave radiation because that is exactly what wavelength this instrument measures.

Ultraviolet Imaging Spectrometer – UVS

This one will watch Jupiter in ultraviolet. Here nice target are again the aurora because they are much easier to watch in UV especially because you can do it even during day.

Waves

Waves are basically two antennas which are about 3 meters long and then one smaller electronic device. This instrument is going to measure the interactions between magnetic field and atmosphere. The smaller device is mostly wire, turned 10,000 times around some bar.


From all of this it could seem that Juno is going to measure only magnetosphere and auroras though this is simply what you can do without needing to crush into the planet. (Which will happen anyway though Juno wont survive of course). All of these things are quite observable from far away and yet they can tell you a lot about the planet.

Dragallur

Check out these pages for more info: 1) 2) 3)

Juno is right at the party!

Hi,
wondering what to write about today I decided that best would be to catch up with the mission Juno which is going to explore Jupiter.

Juno Reaches Jupiter

This is doodle by Google which shows the excitement of the scientists as they watch the signal from Juno coming back after it started to orbit Jupiter.


So it has been basically 5 years since NASA launched Juno (2011 August). This satellite is the second one after Galileo that is going to orbit around Jupiter. Most of others were just on flyby to other places and Galileo kind of broke.

Artist’s impression of Juno.

Juno mission is going to last for about 1 and ½ of a year. This seems kind of short time when you consider that it took alone 5 years to get there. SciShow Space said that it is because NASA does not want to risk getting Europa spoiled with ANY organisms from Earth though I think that this is nonsense and that NASA just does not have enough money which is something I will get to in another post.

What will we get? Well hopefully we will learn more about formation of Jupiter and whole Solar System, this is basically the main purpose but priority is also the gas of Jupiter and its magnetic field. We wont get probably any pictures of the moons because they are not part of the mission and they would be very small. At one point the JunoCam instrument will have a great resolution of Jupiter, about 15 kilometers per pixel. This is something amazing since Jupiter has about 140,000 km in diameter.

Right now Juno is on what is called “capture orbit”. Those are two 53.5 days long orbits which will then lead to 14 day science orbits where the real data is going to be harvested.

Everything about the mission is quite planned.

Juno is also the furthest man-made satellite that is powered only on solar panels. At the distance where it is, there is only 4% of sunlight compared to Earth.

Next time I will cover what tools Juno carries.

Dragallur

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.


The law goes as follow:{\frac  {T_{1}^{2}}{T_{2}^{2}}}={\frac  {a_{1}^{3}}{a_{2}^{3}}}

T stands for time and 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 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:KeplerLaw3

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

Green trail, golden leaf! (part 2)

Hi,
in the last post I was writing about the contest I was one, so check it out if you have not already.


It was pretty cool, and I got surprised at how the kids discussed with me so many things on my presentation.

Those were the questions I mentioned last post:

 

  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)

These were for younger kids and there were two more though I can not remember them..

The first question was normally quite ok, though not always they got 3. Of course most said Armstrong and Gagarin and some people said Vladimír Remek who is the first Czech astronaut.

Astronomical unit is distance from Earth to Sun and light year is the distance the light travels in one year. I thought that those would be very easy but actually to my surprise the kids usually knew what light year is but not AU, though I would guess rather the opposite.

Three missions? Most said Apollo and Sputnik (really, why Sputnik?). Some said the third which was for example Curiosity.

Four constellations are Ursa Major, Ursa Minor, Leo, Orion… and so on, we did not approve parts of constellation like Big Dipper which is just part of Ursa Major.

Olympus Moons on Mars.. few kids new this.

Nobody knew both Kuiper belt and Oort cloud I think and some teams knew one, this was kind of hard I guess.

You already know the difference from one of my posts!

Questions for older kids:

 

  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. What is the heaviest element that fuses in core of star.

Afelium: furthest point to Sun. Perihelium: closest point to Sun.
Most people did not know.

Only one group was able to name Europa, Callisto, Ganymede and Io.. most did not know what Galilean moons are.

I already described HR diagram in one post, I really love it though!

There was nebulae, protostar (most people did not recognize it), normal star, red giant, supernova, white dwarf, neutron star and black hole.

Comet has very elliptical orbit and it comes either from Kuiper belt or Oort cloud as I said.
It has two types of tails:

There are two types of tails.

It is iron!

Dragallur

 

 

 

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.


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

Receding planets

Hi,
today I will continue with short post because I have a lot of work to do for my 15 page essay.


When you are watching planets they travel along some predictable paths which from the view of whole Solar System are ellipses. If you measure where they are on the sky you must do it relative to something. Usually you will use stars that is because ground is too far away and it would be inaccurate (too far away in degrees).

So you measure the planet’s position every day and then strange thing happens, the planet goes back and weeks later it returns back to its original pathway, what happened?

This movement is called retrograde – backwards motion. Of course nothing like that happens simply because there is nothing to cause it.
It would take about this force to actually stop Mars in one second: 15,453,822,450,000,000,000,000,000.

T is Earth, P is planet which we observe, A is the projection on celestial sphere.

The picture above should explain you what happened here. The thing is that we orbit faster than Mars. The picture that we see A1-A5 is the projection on the background, also called celestial sphere.

The same thing happens when you are driving on highway and there is truck ahead of you. As you catch up, the truck moves relatively to objects that are very far away. At one point as you drive around the truck you may not even see them and then suddenly the truck seems to be behind the far away stuff that you watched but the truck was moving the same way all the time.

This was a huge problem for astronomers. First they made various epicycles on epicycles to explain this strange movement and it took Copernicus to show that it is just an optical illusion.

Dragallur

 

 

 

Space NEWS #8 (Planet Nine and Flower on ISS)

Hi,
why space news again? Well new planet has been found, if you know something about astronomy this would not really excite you since new planets are found “all the time”. Well what if I say to you that Solar System has new planet? The planet Nine?

Also on ISS first flower was able to bloom!


When I saw the message about planet Nine I was very excited, but most media made again a mistake to say that it was found, that is not right it was not found yet. There is a strong evidence that such a planet could exist in our Solar System (if this planet is really approved to have been found, I promise to make another post about for “Planets of our Solar System”).

This planet would have mass to about 10 times the mass of Earth making it about the same size as Uran and Neptune, which means that it would be ice giant.

Above you can see the artist’s impression of such a planet. The evidence for it is in the movemenent of TNOs (trans neptunian objects). Those are things like Sedna which you can see below.

Those objects as well as planet Nine have highly excentic orbit. It is clear that we can detect them only when they are close to Sun which means that there are surely more of them. The problem is with their orbit lined up in plane which is very improbably without planet Nine. It’s magnitude is very low, to about +20 or so making it really hard to see even if we were able to find it’s exact spot on the sky. It could orbit in distance ranging from 200 AU in afelion and 1000 AU in perihelion. Caltech is the institution that published about it 20.1.2016.

This week also for the first time flower called zinnia (it is on the picture) finally bloomed. Why this plant? Because it has longer growth of about 60 to 80 days which is more then plants which were planted before.

This flower is a big step forward to grow tomatoes.. tomatoes for food!

That is why it is so important, we need to be able to make a food in microgravity to sustain when traveling through deep space.

Dragallur

 

The Universe is enormous

Hi,
I was thinking what topic should I mention today and remembered that the Universe is huge, and it is so huge that we completely underestimate it (at least I think that I still do).


First I will turn towards our planet, the Earth.
Here the biggest misconception is the size of Africa, you see the problem is that in most maps of Earth which you will see is Africa in the middle. If you know little about geography you know that there is no way to perfectly put our planet to scale on map. There are some ways which will be more accurate than other but most of the time Africa is going to be smaller than other continents. continent_infographic-01 copy

OK, now compare this map above with the scale on your home atlas, Africa is going to look tiny probably with Greenland, Siberia and Canada huge.

Now look at the picture of Earth and Moon distance, they are so little, Earth would be able to fit there so many times!

Now, seriously, look at this amazing page: THIS You start with Moon which is wide as one pixel. Next you will see Sun which seems to be pretty huge. Now if you click the speed of light button you will start to move slowly to right. Oh my god, the speed is so awfully low!

On top of page you have the bar with planets so you can click on them and ride from one another, remember, it is TO scale, and after you drive through whole map they say: You would have to travel 6,500 more maps like this to get to something.

This is huge, we are from Sun only 150,000,000 km.

OK´, Sun is small, lets see why:
1st picture shows that Sun is big:

2nd picture, well Sun gets little smaller:

3rd picture is actually a whole different story:
Now here is the last to compare it all, with little bonus of Canis Majori:
Ok but all of this stuff is so freaking small compared to whole Milky way! The radio signal from Earth which traveled for tens of years is not even visible on map of Milky way!
You can fit Sun 1420 times next to each other inside VY Canis Majoris.
And  you can fit Earth like this 109 times.
This means that you can fit Earth 157,780 times inside VY.
The diameter of Milky way is roughly 140,000 light years. Where one light year is 9,460,730,472,580,800 meters.

This is 741,669,055,548 Earths for diameter of Milky way. 2,540,000 light years is the distance to Andromeda galaxy, the closest galaxy.

Virgo Supercluster has 110,000,000 light years. Easy. On the next picture from @HighTechPanda , you can see the comparison of largest galaxy to Milky way, enjoy!And last, observable universe has 93,000,000,000 light years in diameter.

Still so underrated.

Dragallur

Africa picture