Habitable zone of a star

Hi,
habitable zone of a star. Sounds like a comfy place, right? Well it can be. It is at least on (tiny portion of) Earth which is an example of object in habitable zone. Such a „zone“ is important for astronomers, or maybe it’s just important for headlines in newspapers.


Habitable zone in a Solar System based on luminosity.

Habitable zone is an area around star where we, with quite limited knowledge on this subject, think that life could be. The simplest „definition“ is that it’s the area where satellite (such as planet) would be able to sustain liquid water. We cannot be sure of course if life needs it but it is the case for the one that evolved on Earth.

The true habitable zone is something a bit more complicated. The simplest case of a planet would be one that behaves as a black body, that means that it absorbs all radiation (light for example) regardless of its wavelength. This is immediately just an assumption because such a planet does not exist. Earth just as Uranus or Mercury reflect light, the planet’s albedo describes this. Albedo is an attribute telling us how much object reflects light. 0 means that it is a black body and 1 means that it is white body aka perfect mirror.

There are even more factors that one could consider. For example, when planet has thick atmosphere it can sustain liquid water (and life) even further out from habitable zone on the other hand if that happens to planet like Venus which is already pretty close, you have got hell. If satellite orbits with high eccentricity the conditions are again different.

It’s hard to combine all of this together which results in lot of different outcomes depending what model one picks. Estimates for Solar System are between 0.9 or even 0.6 to 1.3, 2 or 3 astronomical units. In most of them Earth is just on the inner edge. These numbers were pulled from Wikipedia.

When we hear in news that a new exoplanet was found in a habitable zone it might not mean much. This news usually come alongside the information that the planet has similar size that of Earth, it’s not like we could travel there or anything, now we are mostly collecting data and learning.

Dragallur

HZ picture: By Habitable_zone-en.svg: Chewiederivative work: Ignacio javier igjav (talk) – Habitable_zone-en.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8462897

Pareidolia

Hi,
today I will write about pareidolia a commonly seen phenomena. People often see familiar objects in completely random things, like rocks.


Clearly there is face in the upper middle part of the picture on the left. There is definitely sign of both eyes, of nose and mouth, thats more than one needs to SNice.svgrecognise face in something, consider the following one on the right. Do you see the black thick circle filled with yellow color, two ellipses and curved line extended in the ends? Yeah me too.

The point is that humans are great in recognizing (most often faces) in things that are actually not them. The first picture is photo of region Cydonia which is a area on Mars. It was taken in 1976 by Viking 1 and of course people thought that it was proof for extraterrestrial life! Well if you take enough photos of Mars there is high probability that some of the rocks there will resemble primitive faces.

Pick me! Some may bypass this pear for its blemished skin while others will see how eager it is to please

“I am the evidence of life on Earth, beware!”

Pareidolia does not happen only in images but also in sounds. For example there is a group of people who listen to so-called “ghost boxes” (sub category of ghost hunters). Ghost box is a box that is skimming quickly through radio channels. This creates lot of background noise and static noise with mix of what you can hear from the actual radio.. they say that the ghost can easily communicate through it.

Simplest explanation is of course that they just interpret extremely bad audio as some kind of words, plus if they listen for many hours they will eventually pop out something that will be an answer to your question, here is a link so you can consider for yourself, remember humans are great in interpreting random noise as actual words[1] (skip like 3 minutes for actual talk).

The story of the original Mars picture got stretched over many years. 2 decades after taking the picture, there was much better one taken by Mars Express as you can see below it was just the low resolution of Viking spacecraft.

There are many things that can trick us so it is not best to take the first explanation that we can think of, be sceptical and do not share if you do not know anything about it.

Dragallur

[1]The “answers” should be mostly made by random quotes from songs.

Smiley: By en:User:Mystìc – Originally created by en:User:Mystìc at en:Image:SNive.gif. Vectorized by Psiĥedelisto, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=55079042

Pear: http://www.dailymail.co.uk/femail/article-3280816/What-photos-s-faces-suffer-facial-pareidolia.html

 

Its about Trappist-1

Hi,
I noticed that in the last days lot of attention was given to this new exoplanets. Well, I guess I have to stay in the “popular sphere” and follow with my post!


Around star called TRAPPIST-1 also known as 2MASS J23062928-0502285 were found together 7 exoplanets, more on this down in the post.

First the star.

Trappist-1 is very small star in special category L which means that it is a red dwarf. You wont find this category in the normal stellar classification because this one and other are made for brown and red dwarfs and were introduced later on. This of course means that Trappist-1 is not very bright or very hot and NOT visible to naked eye (it has apparent magnitude of 18.8 which is way outside of what human eye can see).

All pictures of these planets are artist’s impression.

 

The planets were discovered using transit photometry. Method that takes advantage of the planets blocking out some of the star’s light. In 2015 there were 3 discovered already and in February this year, astronomers in Belgium found another 4.

There names are truly beautiful: b,c,d,e,f,g,h (aka. Trappist-1b…)
b,c,e,f,g have similar size to Earth and d,h have radius somewhere between Mars and Earth. e,f,g also orbit in the habitable zone of planet which is an area around the star where liquid water might stay on the surface.

Bit of a problem is that since the planets are so close they receive lot of radiation from Trappist-1 and are also probably tidaly locked, which means that they are facing the star with always the same side, thats what is happening to our Moon too. All of their orbits’ radiuses (semimajor axes) are in matter of few millions of kilometers. For Earth this is 1 AU or 150 millions and for Mercury roughly one third. Their years last few days, for Trappist-1b it is just 1,5 days. Those are definitely some crazy numbers but since we know so little about formation of new life we can not really say how high the probability of something living there is.

NO signals were detected from that direction.

Dragallur

PS: You would have amazing view from the planets since they are so close together.

Source of picture: By NASA/JPL-Caltech – Catalog page · Full-res (JPEG · TIFF), Public Domain, https://commons.wikimedia.org/w/index.php?curid=56513150

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