Alpha Centauri

Alpha Centauri is the closest star system to our Sun. It is actually a triple star system, with Alpha Centauri A, a G2V star much like our Sun, Alpha Centauri B, a slightly smaller and cooler K1V star, and Proxima Centauri (also Alpha Centauri C), an M6V red dwarf. Proxima Centauri is named thus, because is the closest star to our Sun.


Alpha Centauri is approximately 4.34 light years away, and as shown above, the largest of the stars is very similar to the Sun. This stellar system is important and will be the first star system humanity will ever visit when we are finally able to leave our own Solar System. Right now, it would take about 81,000 years with our fastest spacecraft technology to reach the star system.


Once we get to Alpha Centauri, we will be able to see if it has planets similar to ours and if the planetary system would be recognizable to us. We would want to see if there were any Earth-like planets and if there could be life on them. Just like the Moon should be our first logical step in colonizing the Solar System, Alpha Centauri is the first logical step in exploring our galaxy.

Days of the Week

So we now finish up the days of the week, and the one thing I want you to take away from the past week is the Latin names for the days of the week. The moment calendar used today (the Gregorian Calendar) was a revision of the Julian Calendar which was based on the old Roman calendar. What this calendar gave us was the 7-day week. And the ancient Romans also thought that there were 7 celestial bodies orbiting around the Earth: the Moon, the Sun, Venus, Mercury, Mars, Jupiter and Saturn, which also happen to be what the Romans named the days of the week after.

Sunday

Sunday. Depending on where you live, the first day or the last day of the week. Obviously, you can easily see that Sunday is named after the Sun. Let's look at Sunday in other languages.

French: dimanche
Spanish: domingo
Italian: domenica
German: Sonntag
Latin: dies Solis

German and Latin are also named after the Sun. What about the other romance languages? Those are actually derived from the Latin for Lord, dominicus. When Christianity became the prevalent religion, Sunday was referred to as the Lord's Day, hence the root for the Romance languages.

Saturday

It's Saturday! And you know that this means we'll look at Saturday in other languages.

French: samedi
Italian: Sabato
Spanish: Sabado
German: Samstag
Latin: dies Saturni

English and Latin have the same root, the Roman god Saturn, while the others refer to the day of Sabbath, which has always been Saturday. East Germans sometimes use Sonnabend, which literally means Sunday Eve.

Friday

Friday, the best day of the week, if you ask me.


Let's see what Friday is in other languages.


French: Vendredi
Italian: Venerdi
Spanish: viernes
German: Freitag
Latin: dies Veneris


All the Romance translations are based on the Latin which translates to "day of Venus". What is the Germanic equivalent of Venus? Frigg (or Friya), the wife of Odin, who was also the goddess of love.

Thursday

Thursday, the fourth day of the week or the fifth, depending on whether or not your week starts on Monday or on Sunday.


Let's look at Thursday in other languages:


French: jeudi
Italian: giovedi
Spanish: jueves

German: Donnerstag
Latin: dies Iovis


Looking at the Romance languages, they are all named after Jupiter, the supreme Roman god. He is also the god of thunder which leads to ... Thor in old Norse mythology. Yes, Thor was not the supreme Norse god, that was Oden, but because he was also the god of thunder, that's where we got Thursday. Donnerstag is also named after the Germanic Thor.

Wednesday

Wednesday in other languages:


French: mercredi
Spanish: miercoles
Italian: mercoledi
German: Mittwoch (literally, midweek)
Latin: dies Mercurii


Romance languages are obviously named after Mercury.


English comes from Odin or Woden (Germanic god similar to Mercury).


German Mittwoch used to be Wodenstag.

Tuesday

Tuesday in other languages:


French - mardi
Spanish - martes
Italian - martedi
German - Dienstag
Latin - dies Martis


As you can see, all the Romance languages are named after Mars, the Roman god of war and the fourth planet in the solar system. However, English and German are different. Who or what are they named after?


In English, Tuesday is named after the Norse god Tyr, who is the Norse god of combat. So in a way, Tuesday is named after the Roman god Mars, but with a Norse twist.


In German, there is some question that it may be named after Thingus, a Latinized version of a German god who may or may not be the same as Tiw or Tyr in Norse mythology.

Monday

This post will be the first of a week long series of the history behind the names of the days of the week. Today, we will start with Monday.


Monday in some other languages:
French - lundi
Spanish - lunes
German - Montag
Latin - dies Lunae
Italian - Lunedi


What do these all have in common? Well, for one, French, Spanish, and Italian are all Romance languages (evolved from Latin), so all three look similar to the Latin word. German and English are also very similar because English is a Germanic language.


The thing that they all have in common is that they all roughly mean the same thing: day of the Moon. Monday is named after the Moon. And we will see as we go on, that most days of the week are named after celestial bodies (or something related to a celestial body).

Gravitational Waves

Gravitational waves have been observed. for the first time. LIGO, the Laser Interferometer Gravitational-Wave Observer, detected gravitational waves created when two massive black holes merged over 1.3 billion years ago. Einstein predicted that they could exist, but up until now, we did not have the technology to detect them.


What exactly are Gravitational Waves? Think of them as ripples in space-time. When you drop a pebble in a still body of water, circular waves move out from where the pebble hits. A similar thing happens when an object with large masses on either end rotate. The masses create disruptions in space-time and as the masses rotate, those distortions propagate radially from the center of mass. When the two black holes were colliding, they were rotating about their common center of mass, and the black holes themselves created the ripples. However, the size of these ripples are extremely small. So how did LIGO detect these waves?


When a gravitation wave passes through a point in space, it can distort the point perpendicularly to the direction of travel. In one direction, space is stretched and in the perpendicular direction, space is squeezed. When the next wave passes, the stretching and squeezing are reversed.

LIGO is an interferometer which is a system of telescopes that uses two or more telescopes to act effectively as a single telescope. What LIGO did to find gravitational waves was when one passed by, one arm of the interferometer was longer than the perpendicular arm. However, this difference is so small (1/10,000th the size of a proton), the precise measurements had to be made. That is why it took almost 100 years to detect gravitational waves.

February

February is named for the Latin word februum which means purification. It is the shortest month, always lasting less than 30 days. It did not actually join the calendar until 713 BC, and was actually the last month (following January) until about 450 BC when January and February were moved to the beginning of the calendar.

The number of days in February varied between 23 and 27 days to account for the precession of the equinox and did not have the length of 28 days until the Julian calendar was established under the rule of Julius Caesar. Leap days were added every four years to account for the orbit of the Earth around the Sun, which was approximately 365.25 days (it is actually 365.2425 days and created problems in the 1580s which we will discuss later).

Any Requests?

Is there something you want to learn about that I haven't covered or didn't cover enough? Let me know in the comments section.

Planet beyond Pluto?

Recently, there has been news that astronomers have found another planet beyond Pluto. At the moment, astronomers think the new planet is about 10 Earth masses and has a period of 20,000 years.

The orbit is highly elliptical with a perihelion somewhere between 200 to 300 AU and an aphelion between 600 and 1200 AU. We can also assume that since the planet is out beyond the orbit of Pluto, it has a density similar to that of Pluto, about 2000 kg/m³.

What do these assumptions mean? It could explain why it took so long for astronomers to find this planet, if it is really there. Using Kepler's laws, specifically, P²=a³, where P is the period of the orbit in Earth years and a is the semi-major axis in AU, we can determine the semi-major axis of the planet. With P at 20,000 years, we find that a is about 740 AU.

Using the density of Pluto and the mass of the new planet (10 Earth masses = 6x1025 kg), we can estimate that the radius of Planet 9 is about 41,500 km. For a perihelion of 200 AU, the angular diameter is only 0.01" (arcseconds) which is typical of a star. It is also possible that the planet has a low albedo, so it is very dim.

So, while it is possible that there is a planet beyond Pluto, it took this long to find it because it is so far away.