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Astro News Archives - December 2007 PDF Print E-mail
Friday, 04 January 2008 21:44

{tab=Attack on Mars?}

Attack on Mars?

     An asteroid with diameter of 50 meters is approaching towards Mars. Its close encounter with Mars will take place on January 30, 2008. It is expected to fly by Mars at a distance of 50,000 kilometers. Despite this, odds of the asteroid directly hitting Mars are as high as 1 in 75. It indicates that still there is 1.3% chance of collision. The asteroid was discovered on November 20, 2007 by Catalina Sky Survey through its telescope in Arizona, under NASA's Near Earth Object Observation Program. It is designated as 2007 WD5. When at perihelion, the asteroid  is at a distance of 1 A.U. from Sun i.e. it comes close to the orbit of Earth. At aphelion, the asteroid is 4 A.U. away from Sun, i.e. its orbit extends much beyond the orbit of Mars. The asteroid has a period of 4.1 years. It is cruising towards Mars at a speed of 45,000 kilometers per hour. It is similar in size to that which had created Barringer Crater in Arizona (U.S.). Steve Chesley, a scientist at Jet Propulsion Laboratory of NASA, says - 'If it hits Mars, it will do so at a speed of about 13.5 kilometers/second.....then there will be a tremendous explosion.....It will create a crater more than half-a-mile wide.'

Image
Oblique view of the respective orbits
(Drawing - not to the scale)

     The event and its aftermath especially with respect to dust loading and other atmospheric effects will be watched by spacecrafts like European Space Agency's Mars Express and NASA's Mars Reconnaissance Orbiter which are already settled in Martian orbits. Mars being close to Earth at present, it may be possible to record the event even with earth-based telescopes. Such events occur on Mars every thousand years or so. But whether this particular asteroid will really hit Mars or not will be clear only after the observations to be carried out in the coming weeks are over.

N.B.: Although orbit of 2007 WD5 crosses Earth's orbit also, calculations show that chances of its encounter with Earth in near future are negligible.

(See the follow-up in the month of January 2008: Mars is out of Danger)

{tab=New Target}

New target for Deep Impact...

     Spacecraft engaged in 'Deep Impact' mission had its celebrated visit to comet Tempel 1 on July 4th, 2005. It had released a probe which caused an impact on the surface of Tempel 1. This Deep Impact spacecraft has still to perform some extra tasks as its tenure is extended. It has to visit one more comet - Comet Hartley 2. This task is known as 'Deep Impact Extended Investigation programme' (DIXI). The targeted comet is a small size comet with a nucleus having diameter of about two and half kilometers. The spacecraft is already enroute to Hartley 2 since November 1, 2007. This rerouting of spacecraft involved a three-minute rocket burn. Spacecraft will fly by comet Hartley 2 at a distance of about 900 kilometers on October 11, 2010. While heading towards comet Hartley 2, the spacecraft will study many of the previously discovered exoplanets also. This task is identified as Extrasolar Planet Observation and Characterization (EPOCh). It involves investigation of planets as small as three Earth masses. It will also look for satellites, rings and atmosphere skirting these exoplanets. This new mission, comprised of DIXI and EPOCh programmes, is termed as 'EPOXI' mission.

Image
Artist's concept of EPOXI spacecraft
(Credit: NASA)

     The spacecraft was supposed to fly by comet Boethin. But track of this comet was lost and the planet could not be located. Probably the comet has disintegrated into fragments, too small to be detected. Subsequently, comet Hartley 2, which is very similar to comet Boethin, was picked out as a new target for Deep Impact. Spacecraft will study surface of Hartley 2 in detail and will also spectroscopically analyse the emanated volatiles. Spacecraft being same, instruments to be used for exploring Hartley 2 will also be same as those used for exploring Tempel 1. But there is one big difference in Deep Impact programme and this DIXI programme. There will not be any 'deep impact' on the comet Hartley 2. Because the spacecraft has already left its impactor on comet Tempel 1!

{tab=Giant Eye}

Giant Eye...

     Astronomers of the next decade will be able to watch the universe through a giant eye. This eye is going to be unprecedentedly giant. It will be nothing but the biggest telescope ever built. Primary mirror of this telescope will have a super-large diameter of 30 meters. This Thirty Meter Telescope (TMT) will be built through joint efforts of California Institute of Technology, University of California and Association of Canadian Universities for Research in Astronomy. The thirty meter mirror of TMT will have segmented design and will be constituted of 492 mirrors, each being 1.44 m wide. Secondary mirror of TMT will be 3 meters wide. This optical-infrared facility will cover wide range of light - 310 to 28000 nanometers. (Visible spectrum ranges from 400 nanometers to 800 nanometers.) Its total light collecting power will be eight times more than any of the current optical/infrared telescope.

Image
View of Thirty Meter Telescope - When completed
(Credit: TMT Project)

     Construction of TMT is expected to begin in 2009 and telescope is expected to see the first light in 2016. Although site for TMT is not yet finalised, it will be one those five locations initially selected in Chile, Hawaii and Mexico. Major portion of the funding of this 300 million dollars project will come from Gordon and Betty Moore Foundation (U.S.A.).

{tab=Invisible Stars}

Invisible Stars...

     Stars started forming in our universe about 100 million years after the Big bang. Researchers in University of Utah and  University of Michigan have concluded that these 'first' stars in the universe were invisible 'dark stars'. These stars were fluffier than normal stars. But they were very big in size - some of them much bigger than even our whole solar System. Their sizes ranged from 4 astronomical units to 2,000 astronomical units. Paolo Gondolo of Utah University says that 'dark matter' has played an important role in the evolution of these early stars.

Image
Artist's conception of Infra-red image of gaseous envelope around dark star
(Dark stars may have had gaseous envelope of hydrogen and helium)
(Credit:: University of Utah)

     About 96% of today's universe is supposed to be filled with either dark matter or dark energy, with only 4% of matter being in the visible form. Juvenile universe might have had still higher proportion of dark constituent. Dark matter annihilates occasionally and produces lot of heat energy. According to Gondolo, substantial amount heat was produced from the annihilation of this dark matter in the early universe. This heat stopped the contraction of proto-stellar clouds of hydrogen and helium. This led to formation of dark stars rather than conventional shining stars as they lacked energy-producing nuclear fusion at the core. Fate of these dark stars could be black hole or they could have evolved into conventional stars at later stage. These stars might have lived for few months, hundred years or even for billions of years after their formation. May be that some of them are still around us. We do not know. Detailed simulations are required to understand the life history of these invisible stars.

{tab=Solar Christmas}

Solar Christmas...

     "Sun is twinkling like a Christmas tree... Every day, it is Christmas for Sun " says Jonathan Cirtain of NASA's Marshall Space Flight Center. He was one of the first persons to notice this twinkling on the Sun. To obeserve this, one has to have X-ray telescope. The telescope should be sophisticated enough to capture rapid images of dynamic solar surface. Jonathan Cirtain could see it. Because he had advanced X-ray telescope aboard Japanese Hinode spacecraft at his disposal. Hinode has shown that sun is bristling with spasmodic X-ray jets. These jets are emanated practically everywhere from solar surface - from coronal hole, middle of the sunspots, or even from places where there is nothing special. Sun was known to emit X-ray jets, but just one or two per day. Hinode's X-ray telescope could detect emission of about 240 jets per day. Jonathan Cirtain who is one of the lead researchers for this discovery is rightly excited with this. Because this may prove to be a next step in our understanding of the Sun.

Image
(Credit: NASA/Hinode)

     What we see as 'surface' of the Sun is its photosphere. Temperature of the photosphere is about 5,700º C. But the Sun is enveloped in tenuous corona. Corona is the blazing portion around solar disc that we see during total solar eclipse.  Corona is known to have temperatures as high as millions of degrees. Is it that these X-ray jets are contributing to these extremely high coronal temperatures? According to Cirtain - "Super-heating of solar corona may not be wholly due to these X-ray jets, but they make an important contribution to it!'. These jets may have implication on the formation of solar wind also. Because these jets are accompanied by ejection of mass. The total mass ejected through these jets may amount to 10% to 25% of that in solar wind.

{tab=Venusian Lightning}

Venusian Lightning...

     Planet Venus is said to be a twin to Earth in certain aspects. Both the planets have more or less similar size and similar mass. Both the planets have atmosphere. They have one more thing in common. Venus also experiences lightening like Earth. Only difference is that lightening on Venus springs up through sulphuric acid clouds, and not through water clouds as on earth. Possibility of lightning occurring on Venus had been a topic of debate since long. European Space Agency's Venus Express has now confirmed this phenomenon.

Image
Artist's Conception of Lightning on Venus
(Credit: ESA)

     Lightning in atmosphere is accompanied by electrical signals, which in turn should be accompanied by magnetic signals. Venus Express which is orbiting Venus since April 2006, has detected these magnetic signals through its magnetometer. These signals last for 0.25 to 0.50 second. Lightning is taking place at an altitude of about 55 kilometers and is intra-cloud discharge. This electrical activity, which has a definite impact on the chemistry of the Venus's atmosphere, poses an interesting challenge for further exploration. But this also involves a warning to the missions of the future - Landers will have to take into account the possibility of stormy weather while descending through the Venus's atmosphere. It is predicted that Venusian lightning may be more intense than that on Earth.

{tab=Fleeing Star}

Fleeing Star...

     Chandra X-ray Observatory has detected a fleeing star in the supernova remnant 'Puppis A'. This star is a neutron star created in a supernova explosion that occurred  3,700 years ago. The star is running away from its original position at extremely high speed of about 5 million kilometers per hour. Although it has traveled only 20 light years so far, it is destined to leave our Galaxy in some millions of years. According to Robert Petre of NASA's Goddard Space Flight Center, this star has got only a one-way ticket - that is for getting out of the Galaxy. Such fast moving stars are known to astronomers but this star is one of the fastest even amongst them. Probably, the supernova explosion was asymmetrical which caused the debris to move in one direction and the neutron star in other direction.

Image
Click the image for details
(Credit: NASA/Chandra X-ray Obs/ROSAT)

     Although the star is moving with a blistering speed, its motion is not easily perceptible as the star is about 7,200 light years away from us. Nevertheless, Chandra X-ray Observatory could measure the displacement in position of this cosmic cannonball successfully. These recently published results are based on the displacement measurements carried out by Chandra X-ray Observatory in the year 1999 and 2005.

{tab=Rosettic Asteroid}

Rosettic Asteroid...!

     There are groups of astronomers who are looking for 'Near-Earth Asteroids'. Arizona based group of such astronomers discovered an asteroid on November 7, 2007. This asteroid was cruising towards Earth at a speed of about 13 km/sec. The asteroid had a brightness of magnitude 20 and a diameter of about 20 meters. The asteroid was designated as '2007VN84' by Minor Planet Centre in Massachusetts. Immediate alert notice was sent all over to observe the asteroid. Orbital calculations showed this unknown asteroid would miss Earth by about 5,600 km. It was to be one of the closest approaches of any asteroid - closer than one Earth-radius. Above information was published on November 8, 2007.

Image
Credit: Remanzacco Observatory (Italy)

     But...Oops! Denis Denisenko of Moscow's Space Research Institute soon realised that 2007VN84 is not an asteroid, but it is European Space Agency's Rosetta spacecraft. Rosetta was en route to comet 67P/Churyumov-Gerasimenko. It was performing a scheduled flyby of earth to gain sufficient velocity for its future journey. As a consequence of this, Minor Planet Centre had to announce on 9th November  that "The minor planet 2007 VN84 does not exist and the designation is to be retired." This humiliating situation had arisen due to failure in communicating the updates about the position of Rosetta by European Space Agency.

{tab=Our Uncommon Moon}

Our Uncommon Moon...

     Total number of natural satellites in our octal planetary system exceeds 160. But out of all these satellites, our Moon holds unparalleled history of evolution. This mode of formation has proved to be uncommon, not only in our planetary system but also in surrounding universe. Most of the natural satellites in our solar system were formed in the vicinity of the respective parent planets at the time when our solar system was coming into existence. Some of the satellites formed as separate entities during the formation of solar system, but were later captured by the respective parent planets. However, Moon was formed about 30 to 50 million years after the formation of Sun and planets. Accepted theory says that a Mars-size object had collided with our mother Earth, removing a big chunk from its mantle. Part of this chipped off material volatised due to the heat of impact and then recondensed in the form of our Moon. According the astronomers, this mode of formation would generate lot of dust in the vicinity of satellite-forming planets. This dust should be identifiable by infra-red telescope.

Image

     But to the surprise of our astronomers, they found that only 1 out of 400 newly borne stars was shrouded in such dust. All the stars under scrutiny were about 30 million years old, as was the Sun when Moon was formed. After narrowing down on the results, the researchers have concluded that probability of formation of satellites through a collision is only 5 - 10 percent. This has attributed a special status to our Moon which has followed a collision path. These studies were carried out by Nadya Gorlova from University of Florida and her colleagues using NASA's Spitzer Space Telescope.

{tab=ISRO's Milestone}

ISRO's Milestone...

     ISRO has successfully tested indigenously developed cryogenic stage. The test was carried out at  Liquid Propulsion Test Facility at Mahendragiri, in Tamil Nadu. This cryogenic stage will form the upper stage of India's Geosynchronous Satellite Launch Vehicle (GSLV). The test was conducted for full flight duration of 720 seconds (12 minutes). The cryogenic liquids used for this were Liquid Oxygen (LOX) and Liquid Hydrogen (LH2). This engine will be employed in the next mission of GSLV (GSLV-D3) in 2008. Successful ground test of the indigenous Cryogenic Upper Stage for the full flight duration has validated the design robustness and performance adequacy for its use in GSLV.

Image
Testing of cryogenic stage (ISRO)

 {tab=Pleiadean Planets}

Pleiadean Planets?

     Pleiades is one of the youngest clusters known to us. It is 400 light-years away. This open cluster holds about 1,400 young stars, which are formed only 100 million years ago – when our mother planet was populated by dinosaurs. One of the stars in this cluster is showing signs of planet formation. Scientists of University of California have noticed giant collisions occurring around this planet. The collisions are manifested through clouds of dust - hundreds of thousand times thicker than that around our sun. These collisions involve participation of planets or planetary embryos. When rocky bodies (like planets) are formed, some of the objects coalesce and some of them shatter into dust particles. According to the scientists, dusty surroundings of this sun-size star is a clear evidence of planet formation. These dust particles, which again coalesce to form bigger particles, are building blocks of planets. Astronomers used Gemini Observatory and the Spitzer Space Telescope for this research. While Gemini Observatory uses a ground-based 8-meter telescope installed in Hawaii, Spitzer Space Telescope is 0.85 m infra-red telescope facility orbiting our Earth.

Image

Present research work forms an extension of the work carried out earlier by the same team of scientists. They had discovered a similar dusty star, 300 light-years away, in the constellation of Aries in the year 2005. This star is 400 million years old. According to Song and Zuckerman, who are involved in all these studies, this cannot be a primordial dust but is generated through collisions. Had this dust been primordial, it would have been dissipated within first 10 million years of the formation of these stars.

Last Updated on Tuesday, 01 April 2008 16:25
 

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