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Have you ever tried going to a dark spot, away from city lights to look at the sky from there? You’ll be amazed at the range of colors and brightness variations of stars in the night sky. Can you guess the number of stars you can see in a very dark sky? Do you think you can see millions of stars? No! At the most you can see about six thousand stars in the sky. That means you probably can’t see more than three thousand stars at any given time! Strange, but true!
When you look up in a dark sky you will see stars of many different hues – bluish white, bright white, bright red, orange, yellow and several other colors in between. Some stars visible to naked eye are extremely bright, while a large number of the stars are faint. But have you wondered if these stars had any names?
Most of the bright stars in the sky, that you can see even from a light-polluted city sky have proper names. In India, many of these stars were named thousands of years ago and the same names are in vogue today. The names of twentyseven asterisms (stars, or groups of stars) starting with Ashwini, ending with Revathi which are part of the twelve constellations in the zodiac have existed for more than four thousand years. By the way, many of the stars from this list of Indian asterisms are not very bright but they were named because they helped ancient Indians to formulate their calendar based on the movement of Sun and the Moon in the background of these stars.
Apart from these, names in Indian languages are available to few other bright stars outside the zodiac as well. The pole star, called ‘Dhruva’ is probably the most well known of such stars. The word ‘Dhruva’ (ध्रुव) in Samskrta means ‘constant’, ‘firm’ etc. This is a very apt name because the position of this star in the sky never changes and stays constant. The Pole star is a not an exceptionally bright star, but is a notable star because of its position it occupies in the sky. All stars in the sky appear as though they rotate around it. The Pole star never rises or sets, nor does it show any kind of movement in the sky. If you were at the North Pole, you would see the Pole star directly overhead, and all other stars go around, never rising or setting. However due to the precession of Earth’s orbit, the Pole star 4000 years ago, is not the same Pole star we have today; but tat is another discussion altogether!
Many of the star names in English are taken from their Roman or Greek names. A large number of star names in English also come from Arabic. For those stars for which there is no native Indian name, Indian stargazers use their international (English) names.
For those stars that don’t have proper names, there is another way of nomenclature. The sky is divided into 88 constellations. Constellations are imaginary star patterns in the sky. Some constellations actually resemble what they are supposed to resemble, and for some constellations, you must have an extremely eccentric imagination to relate a constellation to the figure it is supposed to mean! But that is beside the point. Any star you that you can see, belongs to one constellation or the other. The brightest star in a constellation is normally denoted by the Greek letter alpha, the second brightest beta, the third brightest gamma and so on. Thus, the brightest star in the constellation of Centaur would be called Alpha Centauri; the second brightest star in the constellation Leo would be called Beta Leonis. In this system, the Pole star would be called Alpha Ursa Minoris, because it is the brightest star in the constellation of Ursa Minor. Thus every star that has a proper name also has a name based on the constellation and the brightness of the star within the constellation it belongs to.
This method of naming although very useful has given some incorrect names too. For example, the bright red star Betelgeuse is called Alpha Orionis, meaning it is the brightest star in the constellation Orion. But if you look up the sky now to look at Orion, you will notice there is one more star that is brighter than Betelgeuse! That star is Rigel (or Beta Orionis, as you might have guessed). Betelgeuse is a variable star, meaning its brightness varies over time. There was a time when Betelgeuse might have actually looked brighter to bare eyes than Rigel, and that’s when this name must have come from and it has stayed on.
Using Greek letters as prefixes to stars would only work for a handful of stars in any constellation. When you look at the sky with a telescope, you’d see thousands of new stars, invisible to naked eye. A new problem of naming these arises. Astronomers have a very interesting way of dealing with this problem.
Just like the Earth is divided by imaginary lines called longitudes from North Pole to South Pole, the sky is also divided by imaginary lines going from the north pole of the sky to the South Pole. Just as there is a prime meridian on Earth (0 degree longitude), there is a 0 hours right ascension (RA) line in the sky. The line that goes through the First point of Aries (The point in sky where the Sun would be seen on the spring equinox) is called 0 hours RA. Any star in sky can be located by its co-ordinates – how many hours (and/or minutes) away from the first point of Aries and how far is it from the equator of the sky. This is very similar to locating a place on the Earth knowing the longitude and latitude.
Now you must be guessing how this helps in naming stars! Every star in a constellation is given a number by the order of right ascension. As an example, the star within the area marked for the constellation Virgo and with the least right ascension will be labeled 1 Virginis. The star with next higher right ascension will be 2 Virginis and so on. Here there is no correlation between the number and the brightness of the star.
The winter (in the northern hemisphere) are a treat to star gazers, wherever it is not cloudy or rainy! There are a bunch of bright stars and constellations in the eastern sky. So what are you waiting for? There are many resources on the Internet to help you identify the stars and constellations. Get out and check out those bright constellations like Orion, Taurus, Gemini, Auriga and Perseus in the winter sky. You can start with the three stars from the belt of Orion, which are unmistakable (see figure). I bet you won’t miss the bright stars like Sirius, Betelgeuse, Rigel, Aldebaran and the Pleiades cluster if you head out and watch the evening sky!
(This is the text of a Toastmaster’s speech I made a long time ago)
Last couple months we’ve seen some nice conjunctions of Jupiter and the Moon. On January 21st, they will come closest seen from the Earth. They would be seen about half a degree apart at the closest. As a comparison, the full Moon is about half a degree in diameter.
Here is a simulated view of the conjunction.
This conjunction is well placed seen from the western hemisphere, because it happens during the early part of night for this side of the Earth. The closest point being around 7:00 pm Pacific time. If you remember the Moon moves almost 13 degrees in one day,the conjunction may not appear so close from the eastern hemisphere unless you wait until late in night/early morning. In any case, don’t forget to look up at the Moon on 21st January 2013
This conjunction is also a good time to observe the movement of the Moon in the background of stars on the Ecliptic. Jupiter being farther away does not move much in a few hours. But the Moon is much closer, and also there is a the advantage of a bright Jupiter close by – So if you see the Moon at an hours interval a few times in the night, you will easily be able to see how the Moon has traveled towards East in the background of stars.
A bonus this time is the conjunction occurs in a very star-studded region of the sky – surrounded by prominent constellations such as Orion, Taurus, Auriga and Perseus. And by the way, the orange-red star close to the Moon & Jupiter is Aldebaran, also known as Alpha Tauri in sky-terminology, and is the 4th nakshatra Rohini, in the Indian lunar Zodiac.
Here is an article about Stellarium, that appeared on today’s issue of Kannada daily Samyukta Karnataka (9/27/2012). Click on the image for a enlarged view. My article is at the bottom of the page:
If the full page view is hard to read, you may choose to click on the following image, for a better resolution, but without the graphical elements:
(I wrote this article last year for ಅರಿವಿನ ಅಲೆಗಳು by Sanchaya).
By the way, I did not even notice another year has gone by for my blog. Surely, this has been the most inactive year for me on ಅಲ್ಲಿದೆ ನಮ್ಮ ಮನೆ!
By now, every kid on the internet and his or her baby-sitter know that the transit of Venus is a once-in-a-lifetime, twice-in-a-lifetime, or never-in-a-lifetime event. So, I am not going to dwell on that aspect of the transit!
In 2004, when the Venus transited the Sun, I was in the wrong part of the Earth .
Did you ask what do I mean by being “on the wrong part of the Earth”? You see, the transit is an event seen when the Sun is over the horizon. So if the planet were to go in front of the Sun during the night-time, hard luck. Just like a solar eclipse.
Transit 2004 Visibility Map from Wikipedia:
Luckily, I was in the right part of the Earth in 2012, so I did not want to miss the once-in-a-lifetime opportunity!
Transit 2012 Visibility Map from Wikipedia:
Adding to my luck, I was invited by a friend to watch the eclipse from his backyard telescope. Since Venus is so small compared to the Sun, the transit of Venus is better appreciated with an optical aid.
And here is the fantastic view through the 9-inch telescope – captured on my mobile phone.
We also looked through a welder’s glass, and it looked cool too. But could not take a picture through that. By the way, did you notice the sunspots in the picture above ? Compare them to Venus, which is about 12000 miles in diameter – and the enormous size of the Sun spots does strike you!
Yugaadi marks the beginning of the traditional lunar new year celebrated in several states of India such as Karnataka, Andhra Pradesh and Maharashtra. Literally, Yugaadi means Adi – “the beginning of” and yuga – “an era”. As per current understanding, a yuga is a measure of time, associated the term with long periods – as in Krta, Treta, Dwapara & Kali yugas, each spanning thousands of years.
However, if we go back in time for about thirty five centuries, we find Indians had a very different interpretation of the term yuga. Vedanga Jyothisha compiled by Laagadha around ~1400BC very clearly defines a yuga as a period of five years. The very opening verse of Vedanga Jyotisha has the following verse:
pa~ncha saMvatsaramayam yughAdhyakSham prajApatim |
dinartvayana mAsAngaM praNamya shirasA shuchih ||
which approximately translated to the following:
“I bow to thee, Oh Prajapati, one who has the day, season and the half-year as limbs, the over-seer of the five-year long yuga”
Vedanga Jyotisha also tells us when the five-year yuga began based on the alignment of the Sun, Moon and stars (specifically both meeting at the star Shravishta) in the sky. Also, according to the text, five years of a yuga were called samvatsara, parivatsara, idaavatsara, anuvatsara and idvatsara. Incidentally, this beginning of a new yuga took place at winter solstice, and not at (or close to) Vernal equinox as the current yugaadi is.
Things change over time. Now, we call every year a samvatsara, and the five-year long yuga is almost unknown to most people! If you are more interested on this topic, I suggest you to read this paper by B.N.Narahari Achar is a good resource.
Wishing a very happy Yugaadi to all visitors at ಅಲ್ಲಿದೆ ನಮ್ಮ ಮನೆ!