Transit photometry

Kepler 186f

Hi,
Today I will write about transit photometry.
This is method of finding exoplanets (means those which are not in our Solar System).

Of course we can not see any of those planets because they are too small. But what we can see or better what can Kepler Space Telescope see is effect of such a exoplanet when it transits around its star. To see this clearly, watch this video.

To describe it with words, when planet transits (orbits) star and Kepler is watching it he will see the little difference in its brightness, some of the light will be blocked by some planet. When this happens periodically we know that there is some planet.
Of course this has some limitations, we can only see objects that are orbiting close to its star because no telescope or satellite has service life of 30 years which would be needed
for Saturn if some extraterrestrial life would watch Sun. Those 30 years are counting with Saturn transiting Sun at the time of telescope´s start.

So this is transit photometry which can be used only for enough large planets that are not really far away from their stars. Usually scientist are mostly trying to find planets in “life zones”. Those zones are in some fixed distance depending on the type of star and it means that we think there could be live. There is lot of candidates for habitable planets and probably best of them is Kepler 452b which is orbiting G type star (same as Sun). 
Because legendary Kepler is getting old and he is able to watch only fixed part of sky there is TESS (Transiting Exoplanet Survey Satellite) which will be able to watch 90%.

In the year of 2024 there will also come PLATO (Planetary Transits and Oscillations of stars). This mission is planned for six years but still it will no be able to find planets with the size of Mars or Mercury.

Last one is NGTS (Next Generation Transit Survey) which is trying to find planets smaller than Neptune around stars with apparent magnitude lower than 13 (7 is not visible to average human eye).

Also astronomers can find out how big is exoplanet by its gravitational effect on star and from this we can even count what is its density.

Dragallur

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Stellar classification

Hi,
what you can see on the picture is extremely cool (hot actually) even that you don´t know it yet. It is called Hertzsprung-Russell diagram and I will try to explain it with the rest of Stellar classification.

So there is first thing I have to clear out: What is Absolute magnitude?
Absolute magnitude describes how bright is star. This of course depends on the distance from which you are looking. It is called absolute because of fixed distance of 10 parsecs (around 32.6 light years). There exists also apparent magnitude which is taken from Earth´s view.

This absolute/apparent magnitude is in logarithmic scale. This means that for every point in magnitude, brightness increases by x2.512. So for 5 points, brightness increases 100 times (2.512^5=100.0226), this corresponds to what was created in ancient Greece. Also it is important to note that negative means more bright.

Absolute magnitude is Y-axis on HR diagram (it can also be luminosity) while X-axis is spectral class or sometimes surface temperature.
Spectral class corresponds with surface temperature, mass, solar radius and its rareness.
There are usually seven types but on the picture you can see nine.
Those seven are OBAFGKM. Where O type is hottest and M coolest with lowest mass.
You can use mnemonic to remember it: Oh Be A Fine Girl (Guy) Kiss Me (I really like this one :D).

And the last thing you need to know about the diagram are those roman numbers. Those are luminosity classes.
VII: those are white dwarfs.
VI: subdwarfs
V: main sequence stars
IV: subgiants
III: giants
II: bright giants
Ib: less luminous giants
Ia: luminous super giants
0: hyper giants! (those are shown on the right picture, blue line is orbit on Neptune and those stars are: blue hyper giant, yellow hg., red super giant and red hyper giant)

So now we can take our Sun and find out what we can tell about it.
Wikipedia says that spectral classification of Sun is G2V.
G: it is spectral class (girl/guy)
on the diagram it is rather on the left and you can see it is yellow.
2: means that Sun is in the upper part of G spectral class, this is only for subdividing those classes where 0 is highest and 9 lowest.
V: (it is 5) this means that Sun belongs to main sequence stars.

Now you can easily find where it stands.
Another example could be 10 Lacertae a star in the constellation of Lacertae.
O9V is its classification.
O: (Oh) you can see it is a super giant but with “only” 9 so it is rather smaller and cooler super giant.
V: again this one is lying in the main sequence so it would belong to upper left corner of diagram.

That´s about it, if you ever check for any star, this classification can be extremely helpful for you.

Dragallur

Note that there is table for spectral classes (taken from wikipedia page stellar classification):

O	≥ 30,000 K	blue	blue	≥ 16 M☉	≥ 6.6 R☉	≥ 30,000 L☉	Weak	~0.00003%
B	10,000–30,000 K	blue white	deep blue white	2.1–16 M☉	1.8–6.6 R☉	25–30,000 L☉	Medium	0.13%
A	7,500–10,000 K	white	blue white	1.4–2.1 M☉	1.4–1.8 R☉	5–25 L☉	Strong	0.6%
F	6,000–7,500 K	yellow white	white	1.04–1.4 M☉	1.15–1.4 R☉	1.5–5 L☉	Medium	3%
G	5,200–6,000 K	yellow	yellowish white	0.8–1.04 M☉	0.96–1.15 R☉	0.6–1.5 L☉	Weak	7.6%
K	3,700–5,200 K	orange	pale yellow orange	0.45–0.8 M☉	0.7–0.96 R☉	0.08–0.6 L☉	Very weak	12.1%
M	2,400–3,700 K	red	light orange red	0.08–0.45 M☉	≤ 0.7 R☉	≤ 0.08 L☉	Very weak	76.45%

Stars of our Solar System: Sun

Hi,
after few hours of study I am bringing next post, this time I am returning to where everything begun, The Sun!
So Sun is the center of our Solar System. But it is far away from the center of our galaxy as you can see on picture (it is about 27000 light years).

Sun is the brightest object on our sky with apparent magnitude -26,74 (I will definitely make post about apparent magnitude because I found it very interesting). Sun makes up of 99.8% of Solar
System´s mass so you have no way of thinking that Jupiter is big. It is 1.4 million kilometers across with mass 333,000 of Earths.

The surface temperature is 5,000°C. Surface here is the edge of what we see, or also edge of photo sphere which I will mention later on.
In the core there are temperatures about 15,000,000°C.
Sun is fusing hydrogen into helium as most stars do. Still in the core there are some more heavy elements like carbon, oxide, neon and others but only in small parts.

Every second our Sun burns 700,000,000 tuns of hydrogen which fuses into 695,000,000 tuns of helium. Those 5 millions is heat escaping the star. This is the same weight as 15 Empire State Buildings! But even more astounding is that this energy equals to 400 billions of megatons of nuclear bombs every second! That is why we feel the heat even from such a distance.

So, there are few layers. (Whole Sun is rotating but different layers in different speeds.)

Core: is the hottest part which takes up over 20% of Sun´s radius (not 20% of volume, remember, it is sphere). Here the fusion takes part.

Radiative zone: stretches to 0.7 of Sun´s radius. There are hypothesis that this zone with next zone creates magnetic field of Sun. Also here the energy is transferred by diffusion.

Convective zone: This zone is almost the rest of Sun´s volume. Here like in ocean hot gas goes up and colder down in process called convection.

Photo sphere: is the visible part of Sun. It is thousands of kilometers thick and much much colder and it has very low density (0.37% of air density on sea level).

Corona: is the outer layer of Sun. We are not really sure why but it is ridiculously hot, about 1-2 million °C even that it spreads 1-2 Sun radii from Sun´s surface. It is even less dense than photo sphere so you can not see it without telescopes blocking Sun or Sun eclipse.

For photon it can take 100-200 thousands year to escape from core because right after photon is created it collides with some particle which blasts it away with less energy so this photon is kinda lost for a long time.

Solar flares are events when charged stuff interacts with plasma. This creates eruption (last picture).
Coronal mass ejections happen when two opposite magnetic fields interact with each other throwing lot of stuff into space and some electromagnetic radiation (first picture).

Both events are connected and can occur together. In the year of 2012 we were very lucky since one coronal mass ejection appeared but thankfully missed us (this CME was so strong that it would probably cut off most of electronic circuits and we would be recovering for very long time).

This is end for today, I hope u guys liked this little bit longer post.
Dragallur

PS: I was taking information from lot of sites but I forgot to copy their URL but it was wiki, NASA and some others from first pages on google.

For more about stars, visit one of my old posts about life cycle of those balls!
And to see what kind of dwarf Sun is visit this post!

Moons of our Solar System: Deimos

Hi,
today I will write about even smaller moon than Phobos. This time it is Deimos, again named after kid of Ares (Mars) and Aphrodite (Venus). Deimos was the god of terror/panic/dread. Radius of Deimos is 6.2 kilometers which is almost half of Phobos. This guy was also found by Asaph Hall but 6 days earlier than Phobos.

Deimos is even farther away from his father. When we would watch him from Mars´s surface we would see just a small point and in full Moon he would be bright about as Venus from our point of view, otherwise he could look like ordinary star.

On the GIF you can see Deimos hiding behind much larger Phobos. Its surface should be similar to his brother´s but instead it is much smoother which is made by “sand” which smooths everything out over time.

There are only two features named and those are craters Swift and Voltaire named after writers who speculated about moons around Mars even before anybody new they are there.

Its original is not really sure. Usually you will find that Jupiter´s gravitation threw both moons toward Mars and he caught them (this would one reason for so circular orbits of both moons) but most likely they are his kids anyway.

And again his escape velocity is 20.16km/h so if you can run 50 meters in less than 8 seconds you will be able to left him… if it would work like this.

Dragallur

If you have not read about Phobos yet, you should!

https://en.wikipedia.org/wiki/Deimos_(moon)
http://mars.nasa.gov/allaboutmars/extreme/moons/deimos/
http://www.seasky.org/solar-system/mars-deimos.html

Apollo missions: Apollo 10

Hi,
what a surprise! I am here again with Apollo missions this time with fourth manned mission.

Apollo 10 was launched in the year 1969 May 18 and 16:49:00 PM. Members of crew were three of course: from left to right Cernan, Stafford and Young.

Stafford was captain. Apollo 10 crew were unique because it was first Apollo mission where all members were already in space (Apollo 11 was second and last). Both Young and Stafford were flying for the third time while Cernan for second.

There was also back up crew if some problems occurred but Cooper and Eisele (Apollo 7) were not in favor of NASA because of some incidents on their missions so it was not planned to move them on next mission (as was usual) and they were back up crew only because NASA did not have enough experienced astronauts.

Highlight of this mission were prepared so that they had all data they needed for Apollo 11 which would two months later land on Moon. Everything they needed to do was done, the most important thing was to approach Moon as close as possible.
By one historian it is said that NASA had to give them low amount of fuel so they could not land Moon even if they wanted.

This approaching was achieved by departing a little Lunar module (called Snoopy, it is on the picture with moon) leaving only Young on the board of “Mothership” while Stafford and Cernan achieved the distance from surface of 15.6 km.

Apollo 10 orbited Moon thirty times and then after 8 days and 3 minutes and 23 seconds they splashed down in the Pacific ocean (actually mission was planned 1 minute shorter this means that they really messed it up).

One of Snoopy´s stage was left there and nobody knows where it landed (crushed) but in the year of 2011 group of amateurs started project to find it out.

Dragallur

I was taking data from these pages:
https://www.nasa.gov/mission_pages/apollo/missions/apollo10.html#.Vi5Wz7erTc

https://en.wikipedia.org/wiki/Apollo_10

Read about Apollo 9!

Moons of our Solar System: Phobos

Hi,
today I will write about second moon. This time it is Phobos, the bigger of the two moons of Mars.
His name comes from the son of Ares (Mars) and Aphrodite (Venus). Phobos is really strange, he orbits closer to its planet than any other moon. Every year it is closer by 2 meters so one day, about 50 million years in the future Phobos will either crush onto
Mars´s surface or he will be ripped by tidal forces so only ring will be left of him.

Phobos was found in the year of 1877 by Asaph Hall. His surface is one of the darkest of any object in our Solar System (this picture has enhanced colors). There are lot of craters and the biggest has almost the same diameter as whole Phobos. You can see it on the right of the picture and it is called Stickney crater after Asaph´s wife. Temperatures can go from -4°C to -112°C.

Phobos has too low gravity so he could not round himself, that is why he looks as potato. Escape velocity from his surface is 41km/h which means that Usain Bolt would be able to run into space on his own feet. The gravity is 0.000581 of gravity on Earth.

Phobos is small but even than he weights about  10,658,529,896,187,200 kg (or 10.6 quadrillion).

One more strange thing about him is that he is orbiting faster than Mars turns around his axis so he can be seen thrice a day rising from west and setting east.

Dragallur

PS: thanks for those who are reading my blog, I have written 50 posts already!

Capturing territory, Facebook page

Hi,
I am here to announce that I just made a facebook page for my blog it is called Science and rationality as my wordpress.
WHY?
Because I want to extend my virtual territory and maybe collect some people from the internet.

Mostly I plan to use my facebook page for short news and links to wordpress.
I will see how it goes and if any people are “liking”.

Dragallur

Make sure to check also my twitter!

Planets of our Solar System: Jupiter

Hi,
lets see what we got here, the biggest planet of our Solar System into which all other planets would fit with space to spare. It is Jupiter, named after Roman god of gods or Zeus in Greece mythology.

It is nine times wider than Earth but its mass is 1300 times larger. It is the fastest spinning planet, one day on Jupiter is 10 hours long which makes him 6% less like a circle. Mean distance from Sun is 800,000,000 km or 5.2 AU.

Jupiter is the closest gas giant, which means that he has no surface only thicker and thicker poisonous clouds with various gases. Darker parts are called zones and lighter belts, both of them are rotating in opposite directions. This process is powered by the internal heat of planet (Jupiter loses heat more than he receives) and by fast rotation.
On the picture you can see The Great Red Spot, it is on left of southern hemisphere. That is storm which lasts for decades but now we know that it is shrinking and eventually it will disappear. But for now it is stronger than any storms we ever hope to have on Earth with winds of over 500 km.

When we would dive beneath its deadly atmosphere we would appear in ocean of metallic hydrogen (hydrogen atoms that are sharing their electrons which makes them act as metal). Underneath we are not really sure but there can be solid core of metals and/or rocks.

While Jupiter is really large it is not even close to becoming star, it would have to be 12 times more massive. There exists a theory that Jupiter helps Earth by changing the pathway of comets and other stuff in space but on the other hand it could work in the same opposite way, but still we are not dead yet.

Juno (Hera) spacecraft is right now heading towards Jupiter. In the half of 2016 it will arrive and for 15 months it will collect the most accurate data that we ever had because of its close orbit.

For now there is 65 known moons orbiting Jupiter and I will definitely mention some of them in the future.

Dragallur

PS: be sure to check out Mercury, Venus and Mars!

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

Moons of our Solar System: The Moon

Hi,
since I have done first two planets of Solar System I would go to the Earth but I find it not so important for me 😀 so I will do the Earth´s partner, the Moon.

Our Moon is largest compared to other moons with their planets.
It has radius of 3470 km compared to Earth which has 6378 km. Moon is orbiting about 380 000 km far away while Earth orbits Sun in 150 000 000 km.

First of all. It is assumed that the Moon was created by extremely huge impact of some planet about the size of Mars which collided with Earth. From this collision Moon was born having both material from Earth and from second planet (Theia is it´s unofficial name).
This event made Earth very very hot so when Moon was cooling its closer side to us was
cooling more slowly and when material evaporated it felt on the dark side. This made Moon much thinner on the side turned to us. (Moon is locked by tidal force)

Over eons and eons stuff fell on our brother. When something collided on the thinner side it was much more common to break through thin layer of the surface so lava could bubble up. When this happened couple of times places called mares (marines) were created, this could not happen on the other side because of its thick crust.

There are lot of different structures on the surface. Dark one are marines, there are also craters and lines from old lava flow or even small canyons and places where it is thought that can be milliards of liters of water in the form of ice. Moon is not geologically active but there is still some liquid lava inside, even after 4.5 mld years.

Dragallur

PS: I saw the blood moon and it was amazing!