Global Astronomy Month

April 2012 will be the "Global Astronomy Month", the world's largest global celebration of astronomy since the unprecedented International Year of Astronomy 2009. Unlike the IYA2009 which was an official decision of UNESCO, GAM is more unofficial evens which is leaded by private people all over the world and it's center is in a great organization "astronomers without borders". The idea is that astronomy and the skies belongs to all people all over the world.

The event schedule for GAM is full, and you can have many activities to choose from, either online or at your local astronomy club, such as solar observation, lunar week, join poetry contest, or even create an event yourself! If you have a telescope, just set a date, find a suitable place, advertize a little in your local neighborhood and show people the moon. First timers of the moon is always a pleasure to hear the wow and "I can't believe it"...

During April there are already some international events, mainly April 12 with the night of Yuri, dedicated to the first man in space.
Whatever it is check the AWB website for GAM2012 and join the biggest star-party of the year

Global Astronomy Month

Twinkle twinkle little star

We all know that stars twinkles, it is also easy to notice that stars twinkle more when they are low in the skies. The reason for all the twinkles is the Earth's atmosphere and winds which cause it. When the light comes from a star the air refracts it and make it changes in position a bit. Stars are so far always that they seems as a point and even the slightest change will cause them to twinkle. Planets also twinkle but much less since they are small disc and not tiny points (see more details here).

I've learned about a great and simple technique to visualize the twinkling or in the more formal name "Scintillation" of stars. I learned it from Monika Landy-Gyebnar, an Hungarian photographer who found it by mistake when she once accidentally kicker her tripod during star photography. Instead of deleting the photo she notices that the photo looks rather strange.Monika does not sure if she "invented" the method or just "rediscovered" it but the first photos I saw of this method are her.
The technique is quite simple. Take a photograph of a star for about 2 minutes without using a tripod. Look at the result. The stars colors change dramatically. This is the scintillation at work! Do the same for a planet, the brightness might change, but not the color! I was very eager to try for myself. It works. Here is Arcturus.

Arcturus scintillation

I even got a very nice photo for Spica.

Spica scintillation

Notice how the color changes as different wavelengths of the light are refracted. For planets it doesn't happen. Here is Mars.

Mars - no scintillation

Thanks Monika for sharing your technique with us!

Venus and the Pleiades

Venus in the Pleiades (M45) 3-April-2012. This is how it looked!   Below are the instructions for seeing Venus and the Pleiades.
Here is a short video to summarize the vent

Last photo from April 4th shows that Venus is leaving M45. Compare all photos and see that Venus is a planet and it moves between the fixed stars.

Venus in the Pleiades (M45) 4-Apr-2012

Venus in the Pleiades (M45) 3-Apr-2012

Venus in the Pleiades (M45)

Venus in the Pleiades (M45)

Venus in the Pleiades (M45)

Here is how it looked a day before

Venus in the Pleiades (M45) 2-Apr-2012

Photographing it is easy. Use the longest zoom lens you have, put the camera ona Tripod and expose for 1-10 seconds see what results are best for your taste, change the ISO from 200 too 800 and more and experience it.
Read below for the full article


Venus is moving fast leaving Jupiter well below. In the following nights, look a little up from Venus and you will see the Pleiades, known also as the seven sisters from the mythology. In two weeks they will have another sister, the eight - Venus.
Start by looking west about one hour after sunset, you will see Jupiter and Venus but look further up, and use the following picture:

Venus, Jupiter M45 and Aldebaran

You might see more or less stars depending on your location but you should see Aldebaran even from major cities. Look for the Pleiades. You shall see at least 4 or five star grouped together looking like a miniature of the well known big dipper. A more formal name for this groups is M45, which designate it as the 45th object in a catalog done by Charles Messier. It is an open cluster of several hundreds stars, very close (relatively) to each other, its distance from Earth is about 360-400 light years, and most people will be able to see seven of them with the naked eye from a very dark location. This is the reason that M45 got its mythological name "the seven sisters", and it might appearing in the bible as well under the name "Chima"
On April 3th 2012, Venus will be inside M45, so there will actually be eight sisters. Of course it will be great opportunity to observe such event, especially through a small telescope. here are some points to notice and learn before such observations

1. Notice Venus orbit and how it gets each day closer to M45. Planets moves and you can see it in your own eyes
2. check in advance how many stars from M45 you can see. Try to do it from darkest place, and even inside a city find a place which is not lighted directly
3. If you have a binocular or a telescope try to count how many stars you can see through it. Even a small binocular will show many more stars
4. During the event, Venus is so bright that it will be harder to see any of the M45 stars, so count again how many stars you can see with your naked eye and any optical device you have on April 3th 2012.
5. Make a sketch of what you see. Is it look similar to the below?

Venus inside the Pleiades M45 - April 3th 2012

Although Venus is in the Pleiades, it is really very far from them, It is just in the same point in the skies. Venus distance from earth is about 100M kilometers (60M miles), The Pleiades distance from Venus (and Earth) is about 400 light years!
Venus orbital period of 224.70069 days  make 13 Venus years almost identical to 8 Earth (orbital period 365.256363004) years. So we will see Venus in the Pleiades again on the same day in April  8 years from now and so on, although the day will slowly drift toward the 4th of April. For Example in 2036, Venus will be inside the dipper.
Good luck and enjoy your observation!

Venus and Jupiter Conjuction part 2

As I wrote in Venus and Jupiter Conjunction, today, Mar 13th is the date that Venus and Jupiter are in the same height in the sky. Their actual conjunction will be between the 14th and the 15th of March, but the alignment was a great opportunity to take some great photos.

I've started with a photo from my roof. It is OK, but there is no proper background unless you call the solar water heating system a nice background.

Venus and Jupiter conjunction still in daylight

So when my wife came home, I could go and wonder on the streets finding proper angles which will add to the atmosphere. First of all I will thank my dear wife for letting me go out in the busy early evening hours. Here are the results:

The first photo is from the parking and shows the next building. This is already getting better

Venus and Jupiter conjunction

After that I've found some trees for the background, this one looks a but like a monster's face.

Venus and Jupiter conjunction looking like a face

And this one above a high palm tree

Venus and Jupiter conjunction and the tall palm tree

After that I went to the old water tower. water tower is a new word in English I learned today!

Venus and Jupiter conjunction and the old water tower

 And above it from further away.

Venus and Jupiter conjunction and the old water tower

 Are you familiar with the Jewish holiday of Hanukkah? If not, here is the explanation briefly. During Hanukkah it is a tradition to light candles in the Menorah. Many public building has an electric Menorah which operate only through the eight days of Hanukkah (The middle light, the Shamash is additional candle). Any day, one more candle is lit. Anyway This is the first Astro Menorah with Venus and Jupiter being the candles.

Venus and Jupiter conjunction Astro Menorah

 Venus is located properly but Jupiter is off a bit. Couldn't get to the proper angles as I have no wings.

Venus and Jupiter conjunction Astro Menorah

 And the last photo is an overall look. Notice the orange tint. The air is full with dust and Jupiter was hardly seen even high in the sky. Time to go home.

Venus and Jupiter conjunction

Several types of electro magnetic radiation

The photo below shows a peaceful sunset. The sun is low in the sky which are hazy, so no filter is required. A large sunspot is seen clearly and close inspection will reveal several more sunspots. The sun, like any star, is a strong source of electromagnetic radiation. The sun emits radiation in many wavelengths long ans short, and we can see only small part of it which is the visible light. In the photo you will see two more source of radiation. The power lines which are of high voltage and emit radiation in the radio wavelengths (long waves), The cellular beacon also emit radiation in the microwave range (Not as long as radio waves).

The most dangerous radiation is, however, the shortest waves, Ultra Violet, X-rays and Gamma rays, The shortest the wave, the longer the path that a particle goes along it. This makes the shortwaves much more energetic, and therefore they can harm living organism.

Day and night are NOT equal on the Equinox!

It is common knowledge that the length of the day and the night are equal on the Equinox day (after all, this is the reason that the day is called equinox in the first place). However a simple look at the calendar or almanac which gives sunrise and sunset times, reveals that this is not true. Let's check the times of sunrise and sunset on March 20 2012 in several cities. 

City          Latitude Sunrise Sunset  Day length  Day/Night difference
Quito         0        6:18    18:24   12:06       12 minutes

Tel Aviv      32       5:44    17:53   12:09       18 minutes

New York      40       6:58    19:08   12:10       20 minutes

Frankfurt     50       6:27    18:38   12:11       22 minutes 

St Petersburg 60       7:59    20:13   12:14       28 minutes   

A few quick conclusions which arise from the table above:

1. The day and night are not equal, not even at the equator!
2. The higher your latitude, the greater the difference.

Let's explain. Indeed the day and night lengths are equal in the equinox but only if you use the strict scientific definition,  which is that the times for sunset and sunrise is the hour when the CENTER of the sun crosses the horizon (either on the way up at sunrise or down at sunset).
However, this definition is not used commonly. Sunrise state is at the first moment that the top of the sun arises, and sunset state is when the last part of it sets. The sun's size is about half a degree, which takes about a minute to move from its center to its edge (the earth rotates about 1 degree in 4 minutes). This sums to two minutes (a minute for sunset and a minute for sunrise) that adds to 4 minutes in the total difference.

We see that the difference is much higher so we need to find another reason. The second reason which attribute most of the length difference is the fact that we can actually see the sun even when it is slightly below the horizon. The atmosphere of the earth works like a giant lens, and it slightly curves the sun's rays. When we look at the setting sun, the fact is that it was set already. However the times for sunrise and sunset take this extra time into account, and this makes the rest of the difference.

The sun is visible even below the horizon

We now need to explain why the difference is larger for higher latitudes. This is due to the shallow angle of the sun. When the observer is near the horizon the sun's angle is steep and it will take it less time to go below the horizon. however when the observer is in a higher latitude the angle is much shallower and it will take the sun much more time to go below the horizon. See in the illustration below. At a higher latitude (the right side) the sun's path is much longer and it will take more time (thus making a beautiful long sunset).

The ecliptic angle cause longer or shorter sunrise/sunsets

 
PS: The equinox is a point in the Earth orbit around the sun. It is not really a day, so even when using the strict scientific definitions, day and night will not be equal on the equinox day since it take time from the equinox point to the sunset and during this time Earth moved a bit!. So day and night will be equal on all Earth only if you stop the Earth movement around the sun exactly at the equinox point, and let it be there for a whole day...

PS2: If you wonder about the common myth of leveling an egg on its narrow edge during equinox, forget it. This is possible (but hard) and no different than any other day of the year.

PS3: If you wonder when the day and night are equal it will be several days before or after equinox (Depends on which equinox, and in what hemisphere you are) depending on your latitude.

Venus and Jupiter conjunction

Update! For photos of the 2012-03-13 Conjunction go to Venus and Jupiter conjunction part 2

This month it will be very easy to watch the celestial movements of the planets. Venus is moving toward Jupiter and away from it. Today (4-Mar-2012), Venus is still below Jupiter but this is going to change, and change quickly in the coming days. Just look west every day after sunset and you will see how the distance between Venus and Jupiter decreases. Most of the movement is of Venus which is an interior planet (Its path is between the Earth and the Sun) and seems to move quite fast. Jupiter is further away and slow, and moves maybe five minutes of an angle per day so for this purpose you can treat it as a star which is fixed in its position.
On 13-Mar-2012 Venus and Jupiter will be very close to each other, just 3 degrees apart. When two celestial orbs are so close to each other it is called a conjunction. Such conjunctions of two planets are not rare (but pairs of rare planets such as Neptune, Uranus and Saturn are). Jupiter and Venus are the brightest planets, and way back in the past, on June 17th, 2 BC, their conjunction made them so close together, just 40 arc-seconds apart that they seemed as a single, very bright star, which might be the origin of the "Star of Bethlehem" (although there are other astronomical theories for this star, such as a Supernova, a comet or other conjunctions). Look at the Illustration below. An observer  would see this incredible sight through his telescope at 100x magnification. Venus is closer to Jupiter than Jupiter's moons, and is just a little bit smaller than Jupiter. Jupiter angular size is 32" and Venus only 25". This is indeed a sight not often seen! An even better conjunction will be at 22-Nov-2065, when Venus will actually go in front of Jupiter, obscuring a little part of it. Unfortunately Jupiter and Venus will be only 7 degrees from the Sun so the chances to see it is very small

Illustration of Jupiter and Venus conjunction from year 2BC

In this conjunction, Venus and Jupiter will not be that close and will appear somewhat like the 2008 conjunction below, but still, it is a nice view to watch. 

The new moon, Venus and Jupiter (2008)

Moon, Venus and Jupiter conjunction (2008)

Moon, Venus and Jupiter conjunction (2008)

What will happen after the conjunction? Venus will continue to go higher until its western elongation, the point where it is furthest away from the Sun. This will happen at the end of March and after that  Venus will start to go back down toward the Sun (getting closer to Earth). Viewing Venus with a telescope will show that it is waning, becoming more and more into a thin crescent, but at the same time, as it is getting closer to Earth, the apparent size of Venus grows. This is way Venus magnitude will not change much during that time. However, as Venus gets closer to the Sun, it will be very hard to see it. The final day of Venus being an evening start will be of course at June 6 (or 5) in the coming Venus Transit. Venus will go over the face of the sun and become a morning star (As will also Jupiter which will go to the "other side" of the sun at mid May)