Road to Pandora

Pandora of as seen in the movie Avatar

The world famous movie Avatar invented an exomoon, which had a story that took a worldwide fame and revenue. That exomoon was Pandora, an earth-like moon that orbits around a gas giant called Polyphemus. As said in avatar, this system lies in the habitable zone (zone where liquid water can exist) of Alpha Centauri A star. Therefore the moon Pandora is teeming with exotic life as you witnessed by watching the movie.

Alpha Centauri A is one of the stars of the Alpha Centauri star system, located at a distance of 4.37 light years away from the Earth. The stars Alpha Centauri A and Alpha Centauri B are orbiting each other, getting close as Saturn to the sun and getting far as Pluto and sun. Many planetary scientists proposed the possibility of a gas giant like Polyphemus is less, because the gravitational pull of the two stars will kick out such a large planet out of the system.  Therefore a terrestrial planet orbiting a star was expected to be found.

In 2009 computer simulations showed that a planet might have been able to form within a distance of 1.1 AU (160 million km) of Alpha Centauri B, and that the orbit of that planet may remain stable for at least 250 million years. Proving close to that simulation, a team of European scientists of the ESO (European Southern Observatory) have found confirmable evidence of an earth-like planet orbiting around Alpha Centauri B star. Then, the existence of Pandora is coming quite possible due to this discovery which was revealed on 16^th October 2012.

Artist's Conception of the newly discovered planet
CREDIT : ESO\L . Calcada

This is the closest exoplanet to Earth which has been ever discovered. Also it is the least massive exoplanet that was discovered orbiting a sun-like star.  This planet is named as Alpha Centauri Bb and it has a 1.13 times the mass of the earth. But don’t expect liquid water on it. Because this one orbits around its star at a stunning distance about 3.6 million miles (6 million kilometers or 0.04 AU) and orbits a round in just 3.6 days. That means its orbit is too much closer to the star than the mercury’s orbit to our sun. The gravitational force of the Alpha Centauri A has pulled the planet much forward to the star. Because of that it has a heat-blasted surface of 1200 ⁰C and it may be covered with molten rock or lava. (Watch the video about it by ESO.)

Although closest to the earth, it took a long time to discover this planet after the discoveries of more than 840 exoplanets. Because the star system is much complex to discover clues of an exoplanet. After high accurate measurements this discovery was made using the radial velocity technique with HARPS (High Accuracy Radial velocity Planet Searcher) at La Silla Observatory, Chile. The technique used is to measure the Doppler shifts in the spectrum of a star due to the gravitational pull of a planet. The highest precision of the HARPS instrument, magnitude of 51 centimeters per second was reported to make this important discovery.   More than 450 HARPS measurements taken over four years of observing have been needed to detect the planet's signal.

Top left : Dome of the telescope
Top right: The relescope
Lower: The HARPS Spectrograph 

The discovery team is composed of Xavier Dumusque (Observatoire de Genève, Switzerland; Centro de Astrofisica da Universidade do Porto, Portugal), Francesco Pepe (Observatoire de Genève), Christophe Lovis (Observatoire de Genève), Damien Ségransan (Observatoire de Genève), Johannes Sahlmann (Observatoire de Genève), Willy Benz (Universität Bern, Switzerland), François Bouchy (Observatoire de Genève; Institut d’Astrophysique de Paris, France), Michel Mayor (Observatoire de Genève), Didier Queloz (Observatoire de Genève), Nuno Santos (Centro de Astrofisica da Universidade do Porto) and Stéphane Udry (Observatoire de Genève).

 Many low-mass planets like Alpha Centauri Bb are in a system of two, three or even up to six, seven planets.  So, this has raised the possibility of a planet in the habitable zone or goldilock zone of Alpha Centauri B, located at 65 million miles from the star that a planet would take around 200 days to orbit. Many astronomers say there are more planets in this system definitely. Dr. Dumusque has said that it would need 8 to 10 years to find a planet at 200 days by using this instrument.

So this discovery makes a landmark in the goal of exoplanet hunters, finding an earth-like exoplanet, the so-called Earth 2.0.  With the advancement of the technology in the next decade, exoplanet hunters would discover a Pandora, orbiting around one of a star or both. Even without Polyphemus, it would be a science fiction Pandora becoming a fact. Some scientists have proposed to send a probe to Alpha Centauri system even it would take 100 years or more time to reach.  It seems like our closest neighbor star system has much more mysteries than we anticipated.

The position of Pandora as depicted in the Avatar game.

Want to know how James Cameron saw Pandora. Visit here for all scientific information about Pandora. 

Astronomical Widgets

Today I’m going to introduce you a freeware which can calculate astronomical events and data. You don’t have to wait for the news to be informed about an astronomical event anymore.

Screenshot of Aciqra

This software is named as Aciqra. By this freeware you only have to set your location and time. Just like Stellarium I have introduced you before, this software generates the sky of earth with constellations, planets, asteroids with grid and all that. A cool thing in it is that it shows the position of Earth’s shadow in the sky. Something really cool that we haven’t seen yet.

Earth's shadow as positioned by Aciqra

 Even though the sky generates is not very realistic this freeware provides widgets to calculate important astronomical events and data. Under the widgets menu you can see the following items.

1. Solar System

 

You can select any number of planets in the solar system and see their real positions relative to each other. Also you can animate them to see their motion in real orbits. That is something really cool. Isn’t it?

2. Conjunction engine

Here you should select two planets to have a conjunction with earth. When you run the simulation you can get the date of conjunction where the angular separation is under zero.

3. Solar events

This is the gadget that I found most interesting. You can get the information of all astronomical events by sun in a certain time period. You can calculate the date and time of solar eclipse, lunar eclipse, transit of Mercury and transit of Venus. Based on the location you have set you can see whether the event is visible in your location. You can even simulate it.

4. Ephimerides 

Here you can get graphs of elongation, angular diameter and Phase of every visible planet over the time. It really is a very informative object to study planets visibility.

So I’m sure you want to install it in your computer. The latest version didn’t have these widgets as I saw. I use Aciqra version 1.3.3.  Although this freeware get into trouble in closing it can be ignored due to the importance of this widgets.Get it from here. 

The latest version is not very interesting as I experienced. Go to the Aciqra website to know about the latest version from here.

Stellarium - A must for every astronomy lover

Have you been ever interested in gazing at the cloudless night sky? Wondering what is out there? Or wondering what kind of a night sky would there be other planets? Well you don’t have to wonder or imagine anymore. There is free planetarium software which creates them all very realistically in your computer monitor.

This freeware is called Stellarium. By this planetarium software you can watch any sky at any time at anywhere on any major solar system body in your computer monitor screen. This view is actually a 3D realistic view. You would feel like watching cloudless clear sky by standing on a ground.  You can use your mouse to turn around just like playing a 3D PC game. And scroll the mouse to zoom in and out.Here are some screenshots of its view.

If you move the mouse pointer to the left hand side and bottom side you can see option panels as in the above screenshots.You can hide these panels if you want. Here you can set your location and time for the sky and search for objects in the left side panel. When selecting other planets to see their skies, remember to choose a suitable landscape given like Moon, Mars and Saturn to get a realistic view. You can select them by ‘Sky and viewing options window’ in the left hand side panel.

You will have to assume a clear sky in all the planets which has an atmosphere even though how cloudy or unclear it can be. Remember to turn off the atmospheric effect in the bottom side panel for locations instead of the skies of the Venus, Earth, Mars, Jupiter, Saturn, Titan, Uranus and Neptune. You could eye witness how strange a sky can be without an atmosphere.  Here you can enjoy spectacular and wonderful views of the planets from different skies. Here are the most spectacular views I got. I wish I could really experience these nights.

A view of Saturn from moon hyperion

A view of Saturn from moon Mimas

 Jupiter rising from moon Metis

A view of Uranus from moon Mimas

A view of Mars from moon Phobos

A spectacular view of Saturnian sky

If you enjoy watching stars, constellations, nebulas, star clusters,  and galaxies with a equatorial grid, Azimuthal grid and meridian all that this is the ideal software for you. You can view constellations according to western, Egyptian, Aztec or Chinese depictions clearly detailed by switching through ‘Star lore’ in ‘Sky and viewing options window’. When you select any object in the sky you can get almost every astronomical detail about it in the upper left side. Also you can have a powerful zoom on them and watch them as if you see them through a telescope.  Another cool thing is that you can study the motion of the stars and planets by increasing or decreasing the time rate. Cool! Isn’t it? You can adjust them all by using bottom side panel.

View of star constellations

Constellations with equatorial grid

With an active internet connection and ‘Satellite Hints’ selected in the bottom side panel you can view the actual positions and visibility of the artificial satellites orbiting the Earth. The orbits of major orbiters like ISS (International Space Station), HST (Hubble Space Telescope) and other major satellites will be clearly marked in the sky.

HST with orbital path live in the night sky

In the configuration window you can see plugins for databases of pulsars, quasars, supernovas, exoplanets, angle measures and all that. There are some scripts of solar eclipse, lunar eclipse, and other astronomical events which can be played as video by Stellarium. Also there are star catalogues which can be downloaded to enhance the star visibility. Hence this freeware is a must for anyone who is interested or curious in astronomy. 

So why don’t you try. To download and for more information visit http://www.stellarium.org/

Alien life on Titan?

I think you already know that Titan is the second largest moon in the solar system orbiting Saturn.  Recently, scientists have discovered clues of some sort of an alien life on Titan.

Titan has a wonderful atmosphere other than any moon in the solar system. It is 1.19 times massive as Earth’s overall and because of that its surface pressure is 1.45 times that of Earth’s. Like Earth Titan’s atmosphere is mostly nitrogen, about 95 percent near the surface whereas the Earth’s is 78 percent. The rest is methane, about 4.9 percent near the surface. Titan is far away from the sun; therefore it is in a frigid temperature of minus 179 degrees Celsius, cool enough to condense methane into liquid form.  Therefore methane condense in the atmosphere and decreases into a percentage of 1.4 in the stratosphere. Here is a comparison of Titan’s and Earth’s atmospheres.

The liquid methane rains occasionally slowly as thick brown snow and cause strong erosions on the surface. The Cassini spacecraft has even detected lakes filled by liquid methane in the polar regions as large as Caspian Sea here on the Earth.

Formation of chemical compounds

If you have learnt organic chemistry you know that methane in atmosphere is converted into other hydrocarbons by photochemical reactions due to sunlight. Therefore as calculated by the scientists the methane in Titan’s atmosphere must be converted into other complex hydrocarbons within 50 million years. But it is still out there flourishing in the atmosphere. This means that the loss of methane must somehow be resupplied by Titan itself.  Also beginning the high content of methane is also a puzzle. If titan’s atmosphere was originated from solar nebula it should be predominantly hydrogen and neon. If the origin is from cometary impacts there must be more carbon monoxide than methane. Hence many scientists have suggested that a special type of volcanoes called cryovolcanoes on Titan released methane. But there haven’t been discovered sufficient amount of cryovolcanoes to emit methane. Only one indirect surface feature called Sotra Facula is believed to be a cryovolcano.

Then what is the cause?

In June 2010,through computer models of the Titan’s atmosphere by Darrell Strobel of  Johns Hopkins University discovered a hydrogen molecule flow, about 10²⁵ molecules per second, formed as a byproduct of breaking methane and acetylene in the upper atmosphere to the surface. But surprisingly, based on the Cassini data the hydrogen gas is lost at the surface. Also even scientists expected to have large amounts of acetylene, as a layer of on the surface after falling from the upper atmosphere formed by chemical reactions. But once again based on the Cassini data acetylene was found very low levels at the surface.

Many speculations have been introduced to explain this scenario. The most interesting explanation is that a methane-based life form on Titan uses hydrogen with hydrocarbons like acetylene and ethane to produce energy. This revolutionary idea mainly came from astrobiologist Chris McKay and Heather Smith.  They suggest that while life on earth produce energy by burning glucose with oxygen resulting carbon dioxide and water according to this equation,

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + Energy

methane-based life forms on the Titan like water-based life forms on the Earth derive energy by this process using hydrogen and acetylene.

C₂H₂ + 3H₂ --> 2CH₄ + Energy

Acetylene has been used because it produces the most energy. This really is a good suggestion for the apparent loss of hydrogen and acetylene on the surface of Titan like the amount of carbon dioxide in the Earth’s atmosphere varies in spring and autumn due to flora and fauna. This is merely a recycling process of carbon just like bacteria here on the earth in the nitrogen cycle. Even though biology has yet not discovered a methane-based life form this is really hypothetical.  Chris McKay has further said that these results of hydrogen and acetylene can also be due to human error, to a meteorological process or to some mineral catalyst. But such an effective catalyst under such a frigid temperature would be a great discovery. You can get a detailed view in here.

But researchers have pointed out that in many senses, hydrocarbon solvents like methane are better than water for managing complex organic chemical reactivity. To greatly suggest life on Titan, In October 2010, Sarah Horst of the University of Arizona reported finding the five nucleotide bases which are the building blocks of DNA and RNA, among the many compounds produced when energy was applied to a combination of gases like those in Titan's atmosphere. Horst also found amino acids, the building blocks of protein. She said it was the first time nucleotide bases and amino acids had been found in such an experiment without liquid water being present.

Also recently, data from Cassini suggested that there could be liquid ammonia mixed Water Ocean under the ice surface of Titan. As this medium has been highly suggested to harbor life, there might be life in it.

There is a possibility of such life form because there is water-based microbes called methanogens, producing methane through this process.

CO₂ + 4H₂ --> CH₄ + 2H₂O + Energy

Methanogens have been found on the earth under extreme conditions on the Earth in places like kilometers under the ice. Therefore it can be anticipated that there might be such life under the ice covers of Titan.

Titan has come to the first place in the Planetary Habitability index, made by scientists in the solar system other than the Earth. Therefore one day we might discover at least microbial type of extra-terrestrial life on Titan. It would change our view of the universe about the life as we know it.

Did Galileo discover Neptune?

We all know that the farthest planet in the solar system, Neptune was discovered in 1846. French astronomer Johan Galle observed it first by using mathematical predictions in celestial mechanics done by French mathematician Urbain Le Verrier. As British mathematician, John Couch Adams also invented mathematical predictions there became a dispute over the credit of discovery. Ultimately the honor was shared.

History says that Johan Galle detected Neptune as the first time in the history of astronomy on September 23, 1846. But did you ever wonder whether any one might have at least seen it through a telescope before that day?

The answer is yes. But when and how? Neptune is even impossible to see in naked eye. Therefore even locating it in the night sky to focus a telescope is also impossible. So it must be accidental. Yes you thought right.

Our famous astronomer Galileo Galilei was very keen on observing Jupiter and its four moons discovered by him Also Jupiter was one of his favorite in the night sky. He observed a faint blue star very near to Jupiter at morning sky on December 28, 1612. Also he observed this faint blue star again just after a month at morning sky on January 27, 1613.  We know this because he took notes about these observations and it has been nearly two decades since the world have come to known about this.

Astronomers by calculations and computer simulations have found that this blue star is actually Neptune which was in conjunction with Jupiter at that time. Neptune was in a backward motion relative to earth as it had just turned retrograde motion in December 1612. It has been long speculated by astronomers that Galileo observed Neptune but he didn’t recognized it as a planet.

Do you want to see for yourself that how the sky looked like when he observed it? You don’t need to know any sort of mathematics. You just need the freeware Stellarium. Download and install it in your computer. Just set the location to Earth, Pisa and set the time to December 28, 1612. See the morning sky for yourself at about 7 AM. Bingo!! Here’s my view. I took some screenshots for you to see.

Do the same for January 27, 1613. Here are my screenshots.

In both cases you could see Neptune near Jupiter. COOL!! Isn’t it?

In July 2009 University of Melbourne physicist David Jamieson announced with evidence suggesting that Galileo was at least aware that the star he had observed had moved relative to the fixed stars.  He says that Galileo had marked the position of Neptune which he had observed on January 6 as a black dot on the notebook of his observation on January 28 1613.This black dot has been discovered as the precise position of Neptune on that day. Then he believes that as the object had moved relative to a star nearby Galileo might have thought that he had actually discovered a planet. Jamieson even decided to do a chemical analysis of the trace elements on the page of observation notes, intending to find whether he marked the January 6 observation on January 28.

So what do you think? I think that Galileo just missed his chance for being credited as the discoverer of planet Neptune.

Mercury has water-ice!!!

Mercury

The Mariner 10 space probe made three passes by the planet Mercury in 1974 and 1975. But it could only explore 45 percent of the planet surface. Therefore Scientists continued ground observations of planet Mercury.

In 1991, planetary scientists Duane Muhleman and Bryan Butler from Caltech and martin Slade from the Jet Propulsion Laboratory decided to study Mercury by radar. What they did was that they sent a beam of 8.5 GHz, 460 kW microwaves  from a half-million watt power transmitter radar system in a 70-meter dish antenna at NASA Deep Space Network , Goldstone, California targeting Mercury.  The radar waves reflected from Mercury were received by the National Radio Observatories 26 VLA (Very Large Array) antennas. Then scientists filtered and processed the returned waves and produced a map of Mercury according to the radar reflectivity of its surface .This the map they got.

Radar image in 1991

In this radar image red indicates strong reflection and yellow, green and blue progressively weaker reflection. You can see a bright red spot at the Mercury’s north pole. In 1994, the same observing team discovered similar reflection’s from the Mercury’s south pole.

Then in 1999, astronomer John Harmon at the Arecibo Observatory in Puerto Rico repeated the 1991 study. This time he used a more powerful beam of microwaves emitted by the Arecibo Radio telescope and the reflected waves were detected by the VLA radio telescope array in New Mexico. This is one of the high resolution images of Mercury’s North Pole that was made by using the data of reflected waves.

Radar image made in 1999

Scientists were surprised to see these reflections from Mercury. Their deduction was that such kind of strong reflections can never be made from a momentary “glint” off a crater wall. When studied further these characteristics of reflections were similar to the ones from the water ice on Mars and icy moons of Jupiter. Although water ice found on earth absorbs radio waves, ice at very low temperatures is a very effective reflector of radio waves. So you know what I mean. Can there be ice on the surface of such a scorching hell like Mercury? Well, scientists say why not?

We all know that Mercury is the smallest planet in the solar system and also the closest to the sun. Being so small to retain an atmosphere its surface temperature varies horribly. Therefore its day side is hot as frying 427 degrees Celsius where as its night is frigid minus 173 degrees Celsius. As the axial tilt of Mercury is nearly two degrees, some crater floors in the poles of the Mercury are in constant shade and never get sunlight, resulting a temperature below minus 170 degrees Celsius. With no atmosphere to trap heat these areas can trap cold and called as “cold traps”.   Debris or vapor drifting from interplanetary space could be permanently captured in cold traps as ever deepening rimes of frost.  

Scientists propose that meteorites in the past potentially carried large amounts of water to Mercury’s surface. Also outgassing of water from the planet’s interior could also provide a non-negligible flux of water to the surface. If any water found its way to the cold traps it would freeze and remain. Also it has been revealed that there should be several meters or more thick  at least 90 percent pure ice to give such strong reflections, indicating that each deposit was laid down in one or a small number of rapid events, such as a large comet impact.   Scientists say that to remain the ice stable there should be a thin (10-20 cm) layer of regolith (layer of dust, soil and broken rock)on them.

Considering the bright radar spots to be frozen ice deposits scientists have calculated that there could be 10¹⁴ to 10¹⁵ kg of ice. I would give a data to compare this. The Antarctic ice sheet here in the earth has a mass of about 4 x 10¹⁸ kg. That really is lot of water. Isn’t it?

   

The MESSENGER space probe, only one to visit after Mariner 10 reached the Mercury in March 2011. It created a global map of Mercury by sending back 87,000 images within its first year. Scientists examined the topographical data and created a 3D model of Mercury’s poles. Here, they could discover cold traps with permanent shade. Also by processing images in the poles they could produce the illumination maps which are given below.

An illumination map of Mercury's south pole(left), black areas are cold traps.The respective visual image(right)
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institute of Washington  

The researchers superimposed observations of radar bright patches by the Arecibo Observatory on the latest photos of Mercury's poles taken by the MDIS imaging instrument aboard Messenger.Stunningly, the areas with constant shade or cold traps perfectly matched the radar bright spots, supporting the water-ice hypothesis. But this evidence does not confirm that there is water ice. Because, sulfur has also been proposed as the cause of radar-bright spots. Therefore in order to affirm the composition of cold traps, looking for hydrogen on Mercury by examining neutrons was done by MESSENGER’s neutron spectrometer.  

Top:Mercury's north pole in visible light, Credit: NASA/JHUAPL/CIW
Bottom: Same place in Radar image, Credit: NAIC/Arecibo

Two images superimposed, yellow patches are bright radar spots,Credit:NASA

Neutrons are created when cosmic rays hit Mercury. They break atoms into their component particles. Scientists can determine the abundance of hydrogen on Mercury by mapping the relative flux of neutrons at different energy levels. Hydrogen in Mercury’s soil would slow down the particles, making them less energetic. As the most likely source of hydrogen in the solar system is water this is an interesting experiment. Currently, Scientists are still crunching the numbers of received data.

Finally we can hope that discovery and confirmation of water-ice on Mercury’s poles would be a great potential for human colonization on planet Mercury in future.