{tab=Close Flyby}

Close flyby...

     A two hundred and fifty meters wide asteroid passed by Earth at a distance of 554,209 km on January 29, 2008 at 02.33 PM (IST). This distance equals 1.4 times that between Earth and Moon. There was no possibility of its collision with Earth. It passed through constellations Andromeda and Cassiopeia at a speed of about 33,300 km/hour as a tenth magnitude object.

Radar Images: Taken on 12/10/2007 and 28/01/2008 (12 hours before closest approach )
(Credit: NASA, Catalina Sky Survey, Arecibo Observatory, Greenbank Telescope)

     The asteroid bears a designation '2007 TU24' and has a period of 2.85 years. The asteroid is asymmetric in shape. When closest to the Sun,  it is at a distance of 0.95 AU. When farthest, it is at a distance of 3.1 AU. Asteroid was discovered on October 11, 2007 by Catalina Sky Survey, Arizona.  Catalina Sky Survey is aimed at discovering near-earth objects (NEOs).

{tab=Touching the sky}

Touching the sky...

     NASA has published a Braille book on cosmic images. Title of the book is "Touch the Invisible Sky". This sixty-page book has images of stars, nebulae, galaxies in it. Images include those captured by Hubble Space Telescope, Chandra X-ray Observatory, Spitzer Space Telescope and those by ground-based telescopes. Book touches the basic aspects of astronomy also. The book is authored by Noreen Grice (astronomy educator and accessibility specialist) with Simon Steel (Harvard-Smithsonian Center for Astrophysics) and Doris Daou (NASA). Raised patterns are employed to appropriately express the shapes and colours of the objects. For the blind, the book will prove to be an excellent access to the information that is normally presented only through visual images.

{tab=Ringed Ring}

Ringed Ring...

     Einstein had predicted the effect of gravitation on light. This effect has interesting consequences, one of which is gravitational lensing. Light rays diverging from a distant galaxy appear to be converging in a ring like structure, if a massive object lies between the galaxy and us. Nearly fifty of such Einstein rings, as they are called so, are known to us. But recently an interesting structure where Einstein ring, encircled by another Einstein ring, is discovered by international team of astronomers using Hubble Space Telescope. The team is led by Raphael Gavazzi and Tommaso Treu of the University of California (USA). This peculiar example of multiple gravitational lensing was found out in the constellation Leo.

 
Click the image to zoom in
(Credit: NASA)

     For such a combination to occur, there has to be three objects collinear with us. Recently discovered combination consists of a foreground massive galaxy which is at a distance of 3 billion light years from us. This galaxy is responsible for the gravitational lensing effect to cause. Behind it, there are two more galaxies one at a distance of 6 billion light years and other at 11 billion light years from us. Discovered rings are images of these two farther galaxies. This discovery is rightly described by Treu as 'hitting a jackpot'. Because probability of finding such unusual alignment is only 0.01%. In other words, you have to look for 10,000 Einstein rings to find one double ring!

{tab=Unseen Mercury}

Unseen Mercury...

     There are many things in our planetary system which have remained unseen so far. A clear example of it is half of the surface of planet Mercury. But now NASA's Messenger spacecraft has seen this unseen side and captured its images for us to view. Following photograph shows that this portion of Mercurian surface is also heavily cratered as the rest. This photograph was taken when the spacecraft was at a distance of 5,800 km from the surface. Photograph shows details as small as 100 meters in size.

 
[Click the image to enlarge it]
(Cortsey: NASA)

     It is after more than 30 years that a spacecraft is visiting Mercury. Previous spacecraft to visit Mercury was Mariner 10. Although it had flown past Mercury thrice, everytime it was the same hemisphere of Mercury which was sunlit, other half remaining dark. This made Mariner 10 spacecraft impossible to photograph half of the Mercury. However, during the Messenger's recent flyby, the unexplored side of Mercury was sunlit and could be photographed. Messenger will have 2 more flybys - one in October 2008 and other in September 2009, before it becomes a Mercurian satellite in March 2011.

{tab=Milky Way being targeted}

Milky Way being targeted...

     Our Milky Way Galaxy is being targeted! It is going to be a giant elongated hydrogen cloud which will collide with our Galaxy. The cloud is only 8,000 light years away from our Galaxy and is heading towards us at a speed of 240 km/sec. It will hit our Galaxy in 20 to 40 million years. The cloud is 11,000 light years long and 2,500 light years wide. If visible, it would have covered Orion constellation. This discovery was made by Felix J. Lockman, of National Radio Astronomy Observatory (USA) and his colleagues using radiotelescope at Green Bank (West Virginia).

Aritist's conception of Smith's Cloud (Credit:  NRAO/AUI/NSF)
(Click the image)

     This cloud is not new to our astronomers. It bears the name of Gail Smith, who discovered it in the year 1963. It holds enough hydrogen to make about a million stars. According to Lockman, it is most likely a gas cloud left over from the formation of the Milky Way. At present, this comet-shaped cloud is made up of only gas. It does not have a single star in it. But when it collides with our Galaxy, it is going to trigger a tremendous burst of star formation.

{tab=HST to be at par excellence}

HST to be at par excellence...

     Hubble Space Telescope has been scrupulously watching the universe for last seventeen years. Scientists want this to continue for few more years - at least till James Webb Space Telescope becomes operational i.e. upto the year 2013. Action will be taken to extend the lifespan of Hubble Space Telescope during its next servicing mission to be carried out by space shuttle Atlantis. Hubble Space Telescope's altitude will be raised using rockets of the Space Shuttle. This will increase 'orbital life' of the telescope by 5 to 10 years. This servicing mission is scheduled to take place in coming August.

Servicing of Hubble Space Telescope (March 2002)
(Credit: NASA)

     Astronauts visiting the space telescope will have to do various repair and maintenance jobs also. These include repair of damaged Imaging Spectrograph and Advanced Camera for Surveys. New gyroscopes will also be set up for stabilizing the telescope.  In addition to this, astronauts have to install two new instruments - Wide Field Camera and Cosmic Origins Spectrograph. These instruments will enhance the capabilities of the telescope in terms of resolution, sensitivity and field of view. Alan Stern, NASA's associate administrator for science foresees the Hubble Space Telescope to be at apex of scientific capabilities with these betterments.

{tab=New Solar Cycle begins}

New Solar Cycle begins...

     Solar scientists have bid adieu to solar cycle number 23. Scientists were eagerly waiting for the arrival of the frontiersman of the next cycle. And it has arrived...! It is a sunspot, but not an ordinary one. It has a reversed magnetic polarity. This is a clear indication of beginning of solar cycle number 24. Now, the so far quiet Sun will slowly regain its activity. The step-up of its activity will be manifested through the increase in the phenomena like solar flares, solar prominences, coronal mass ejections, etc. Solar Activity will be peaking around the year 2013. Following this 'solar maximum', the solar activity will start decreasing. By the year 2018-19 , it should be again a quiet Sun. (And with this, Cycle number 24 will end.)

Sun: White light image (Left) and magnetogram
(Click the image)
(Credit: SOHO)

     Number of sunspots is a yardstick for measuring solar activity. More active is the Sun, more will be the number of sunspots on the solar surface. These sunspots are associated with very strong magnetic field - several thousand times stronger than that of Earth. Moreover, sunspots in each solar cycle has magnetic polarity of particular type. When solar cycle changes, the magnetic polarity of the sunspots in the new cycle will be in the opposite direction compared to that in the old cycle. This reversal of magnetic polarity gets reflected in the spectrum of sunspots. When this reversal is noticed, solar scientists are assured that new solar cycle has begun. That is what it has been observed with the recent sunspot discovered on January 4, 2008...!

{tab=Underwater Telescope}

Underwater Telescope...

     There are many telescopes built atop high mountains. But telescopes built under water are not at all common. One such telescope is being constructed on a seabed at a depth of 2500 meters in Mediterranean Sea. This telescope is not a conventional telescope. It will detect neutrinos coming from various cosmic sources like quasars, active galactic nuclei, supernova remnants, etc. It will also detect the neutrinos produced during the annihilation of particles and antiparticles from dark matter. Results from Antares Telescope will shed light on processes occurring inside all such objects. The Antares telescope is being built by Antares Collaboration which has 20 European Laboratories associated with it. Although incomplete, the telescope has successfully passed maiden test for the detection of neutrinos. The construction phase of the telescope is expected to be over within few months.

Antares Telescope (Artist's rendering)
(Credit: Antares Collaboration)

     Neutrinos are chargeless and practically massless particles that easily pass through matter. Despite this, a small fraction of them interacts with medium through which they pass. This interaction yields short-lived particles called muons. These muons, in turn, emit optical light called Cherenkov light, through an interaction with the medium. This light can be quantified with appropriate instrumentation (like photomultiplier tube), thus comprising an indirect method for the detection of neutrinos. For the Antares telescope, water acts as a medium for producing Cherenkov light. Since, the neutrinos interact only weakly with matter, system has to be very large in size. Detectors and the surrounding seawater constitute the required large size telescope. Total number of photomultiplier tubes used in this telescope is 900. These tubes are mounted on vertical cables. This unusual telescope covers an area of 100,000 square meters and is about 500 meters high. Two thousand meters thick water table above the telescope absorbs exotic muons which are generated through interaction of cosmic rays with the terrestrial atmosphere. Riddance of these muons is very much necessary to reduce the background noise in the telescope.

{tab=2009: International Year of Astronomy}

2009: International Year of Astronomy

     It was in the year 1609 that Galileo observed the skies first time through his telescope. Use of telescope for the study of heavenly bodies deciphered many of the secrets of the universe. Telescope, in fact, extended the horizon farther. This laid foundation of modern astronomy. Galileo's discoveries wiped out the deep rooted ancient beliefs about nature of the universe. Copernican heliocentric theory was upheld. Galileo's findings not only revolutionised astronomy but also changed the way of thinking of humankind. He showed that science cannot be based on mere beliefs. He was truly a 'renaissance man' in science.

     To commemorate Galileo's historic endeavour of introducing telescope in the field of astronomy, sixty-second General Assembly of United Nations has proclaimed the year 2009 as International astronomical Year (IYA2009). While United Nations Educational, Scientific and Cultural Organization (UNESCO) will be the lead agency to celebrate IYA2009, International Astronomical Union (IAU) will act as the facilitating body for the same. The celebrations will be global with more than 140 nations' participation in it.

{tab=Follow up}

Mars is out of danger (See: Attack on Mars? - December 2007):
     Mars appears to be out of danger. Chances of asteroid 2007 WD5 striking Mars have turned out to be remote. Probability of collision has reduced from 1 in 75 (1.3%) to 1 in 10,000 (0.01%). This is based on recent observations from several observatories around the world. Calculations show that the asteroid will be 26,000 km away from the centre of the planet when closest to it.