those BALLS OF FIRE are back

it's that time of the year again.And it's time for yet another display of those spectacular Leonid showers.These meteor showers(seen basically as streaks of light), and if large enough sometimes individually described as shooting stars, are basically a display of atmospheric fireworks.They are basically caused by rocky remnants left on the orbital path of earth by some other astronomical objects such as comets burning up upon encountering the earthly atmosphere.Leonids are so called as they originate ( that is enter the Earth's atmosphere) in the area of the sky demarcated by the constellation of Leo.Due to the regularity of Earth's orbital period and path, these showers (in particular, in the month of November) are caused almost always by the comet described by the name Comet 55P, Tempel-Tuttle.Thus as one would conjecture they are most prominent when the comet has just visited it's perihelion(that is it's closest approach to the Sun.),- as this would be the time that most of the cometary debris would be floating closely packed in interplanetary circumsolar space.

As the comet has not been in close proximity to the Sun for quite some time, the 2007 Leonids are expected to be a somewhat modest spectacle in comparison to the previous season's fiery display.but they are still expected to be quite a sight nonetheless.the showers peaked this last week and are still visible to the keen observer.all one requires is a comfortable place to lie down somewhere below the open sky.keeping an uninterrupted view of the whole sky while lying down is essential to the act of catching a meteor(/shooting star) doing the burning ('Great Balls of Fire') act.Binoculars are a strict no-no, as are telescopes, as this would narrow the field of observation and greatly reduce the observer's capability to spot a shooting star and also make it difficult for the observer to track it once he spots it(if he succeeds at all in spotting it using binoculars in the first place!).

as described before, focus on the constellation of Leo from where these shooting stars shall appear to streak out.do note that the shooting stars shall only appear to be streaking out from Leo and might make their brightness more apparent once they are further away from the constellation.Hence it is essential to keep a look at that entire region of sky(and not limit oneself to Leo alone) to have a proper perspective of the showers.If you have trouble locating Leo, but are comfortable identifying the planets, Leo is the (abnormally big bladed) sickle shaped constellation appearing above Saturn.
so i guess things are looking up this week, and maybe we should too.....
Surjodeb Basu (/Dev).





Some amazing images of actual Leonids in action in different parts of the world taken with different camera exposures:
(Click on them to enlarge)

the black hole in our midst

holes are generally black (or so we conjectured!).but what if the best way to detect a hole was by the brightness surrounding it?!
Such is the story of our nearest black hole.

We know that all holes in space attract.but black holes are special! These holes warp space (into holes) to such an extent that their attraction is the strongest possible.Not even light itself can escape their lure.


In the past most people used to think that Black Holes were rare objects, to be found in remote regions of the cosmos.But during the nights in the first week of November in 2004, a team of astronomers from UCLA (led by Andrea Ghez) and another team from the Max Planck Institute(led by Reinhard Genzel & Rainer Schodel) observed the supposed center of our galaxy in Sagittarius using simultaneously the Keck telescope in Hawaii and the ESO's Very Large Telescope in Chile.

Before this, The astronomical observations in the Radio spectrum had indicated that due to maximum intensity of radiation in that region in the sky, that was probably the centre of our galaxy.
We derive this conclusion logically from the facts derived and then proven by observation, based on the assumption that no ExtraGalactic source could produce a cumulative effect on radiation intensity of such a magnitude(on us) that it would overshadow the cumulative effect of radiation produced inside the galaxy.the second assumption we make in our search is that as we face the center of the galaxy we will encounter light at maximum intensity(this is because if one draws a circle and from any point inside the circle he wants to draw the longest line, it has to pass through the centre and towards the other side.this is analogous to saying, "to encounter the maximum number of stars[or in this case light], we must face the centre of our galaxy".)
knowing these two things we can them conclude that probably the light from the direction of the centre of the galaxy has to travel through the maximum number of obstacles to reach us.this then leads us to the next conclusion that obviously then efforts to search for this direction in the visible spectrum would be futile.
hence we attempt our search in the longest wavelength regions i.e. in the radio spectrum.


now, as i was saying, that week in november these 2 teams from the 2 universities upon having already previously been intimated with Harlow Shapley's work on this subject (that was done around 1918) set out observing the Centre of the Galaxy.As they had expected, brightness was at it's peak.A large number of massive stars appeared to rotate around that place.But the peculiarity of the observation was that there appeared to be nothing bright (or no BIG BRIGHT STAR) at what appeared at high resolutions, to be the exact centre of our galaxy (as everything else appeared to be rotating around it.) This was an observation that went against what one would instinctively assume to be true.and most of the members of the 2 teams were not quite happy with this observation
Something felt out of place!

The two teams, in particular the team led by Prof.Andrea Ghez from UCLA decided it best to observe this region over a period of time. and try and decide by the motion of the nearby stars around the centre, the estimated gravitational pull that would be required from the centre of the galaxy such that the nearby stars might revolve in the way they revolve around the centre.

Upon careful observation of the tracks they noticed how the nearby stars were catapulted/accelerated /swung around (using what is appropriately described as slingshot action.aka satellite motion lingo) , as they approached the centre of the galaxy.Their mathematical computations quite interestingly predicted that the mass of matter that would be required to accelerate the giant stars in the way observed, (the mass of the stars was estimated by measuring their brightness and motion), would require mass of the order of approx 3000SM(SM=Solar Mass.Number of times the mass of our own Sun) to be concentrated at the centre of our galaxy.This amazingly large amount of mass concentrated in this realtively small region of space, without being squeezed into oozing out radiation in the form of light oin the optical region led them to only oine conclusion.-THERE WAS A SUPERMASSIVE BLACK HOLE AT OUR CENTRE!

And the rest is (NOT HISTORY!) told only by the future....
Surjodeb Basu (/dev).

ps- in case u wanted to do futher reading up, the exact center is referred to as Sagittarius A.
It consists of three components, the supernova remnant Sagittarius A East , the spiral structure Sagittarius A West, and a very bright compact radio source at the centre of the spiral, Sagittarius A*. These three overlap: Sagittarius A East is the largest, West appears off-center within East, and A* is at the center of West.

U can also refer to,
http://www.mpe.mpg.de/ir/GC/index.php
http://www.astro.ucla.edu/%7Eghezgroup/gc/

I referred also to,
http://www.astro.ucla.edu/~ghez/
http://www.astro.ucla.edu/%7Eghezgroup/gc/people.shtml


I am also enlosing some pictures (from various sources) that shall help illustrate what i explained.:

What is a Full Moon Ring?

FULL MOON RINGS: Sometimes the best thing about a bright full Moon is what goes on around it. Last night in Northern Ireland, Conor McDonald photographed this beautiful moon-ring:

The correct name is "lunar aureole," cousin to the better-known lunar corona. Aureoles and coronas are caused by water droplets in clouds. When the droplets are a jumble of different sizes, they produce a straw-colored ring--an aureole. When the droplets are all of the same size they produce a rainbow-colored ring--a corona. Look for both tonight.
Surjodeb Basu (/dev)

Why is a Mercury Transit so rare and Significant?

Why are transits of Mercury so rare? Does it make sense?
The thing is Mercury's orbit is tipped with respect to Earth's and crosses the plane of our orbit at only two points. For a transit to occur, Mercury must lie near one of those points when it passes us. To meet these conditions, Mercury must slip between Earth and the Sun within 3 days of May 8 or within 5 days of November 10.

The unequal size of these "transit zones" reflects the eccentricity of Mercury's orbit, which gives us twice as many transits in November as in May. Mercury lies farther from the Sun and moves much slower in May, which reduces our chance of catching it in the right place. But Mercury's disk appears 20-percent larger during May transits because it's closer to us then.
Surjodeb Basu (/dev)