{tab=Brightest Gamma Ray Burst}

Brightest Gamma Ray Burst...

     So far Triangulum Galaxy (M33) was the most distant object detectable to unaided eye. But now that record is held by a luminous afterglow of a gamma ray burst detected on March 19, 2008, in Constellation Boötes. While the Triangulum Galaxy is only 2.9 million light-years away, this source was as much as 7.5 billion light-years away from us i.e. half-way to boundary of the visible universe. The object was picked up by NASA's Swift satellite through its X-ray and Optical/Ultraviolet Telescopes. Visible component of the burst had a maximum magnitude between 5 and 6. High luminance of the source lasted for about half a minute.

Image by Swift satellite's X-ray (left) and Optical/Ultraviolet (right) telescopes
[Credit: NASA]

     Gamma ray bursts are produced when massive stars undergo gravitational collapse. Energy produced during such stellar explosion is enormous. Emitted energy heats up the surrounding gases resulting in optical afterglow. This particular afterglow turned out to be 2.5 million times more luminous than any of the earlier recorded supernovae. Incidentally, Swift satellite detected three other gamma ray bursts on the same day. Registration of four gamma ray bursts in a single day is a record for Swift satellite.

{tab=A daring flyby}

A daring flyby…

     Cassini spacecraft had been very near to Saturn’s moon Enceladus on March 12, 2008. The spacecraft passed within 50 km from the surface of this little Saturnian moon. (Enceladus has a diameter of only about 500 km.) Considering Cassini's high cruising speed of 15 km/sec (54,000 km/hr), this close approach was really a daring flyby. This flyby was specially designed for investigating icy-water geysers spewed from the surface of Enceladus. Cassini spacecraft collected samples from these rising jets. These jets spring up from the ocean which Enceladus is expected to hold underneath its frozen surface. It is not known whether the ocean contains only water or it has organics also. Analysis of the samples will reveal the nature of the underground ocean. This is very important, because Enceladus is feeding Saturn’s E-ring. These investigations will continue during the future flyby of Cassini on October 9, 2008.

Cassini’s path during the flyby
[Credit: NASA/JPL]

(See: Food for E-ring in February '08 Archives)

{tab=Space Odyssey halted}

Space Odyssey has halted! 

Arthur C. Clarke passes away...

     Arthur C. Clarke, one of the greatest visionaries in the field of science fiction writing, is no more. Arthur C. Clarke died on March 19, 2008 at the age of 90 in Sri Lanka. He was born in Somerset, England but settled in Sri Lanka (the then Ceylon) since 1956. His visionary capabilities were perfectly reflected in his books like  2001: A Space Odyssey (1968) and Rendezvous with Rama (1972).

Sir Arthur C. Clarke
[1917-2008]

     As one of the most prolific and popular science writers of all time, Arthur C. Clarke had earned a global reputation. His extremely rich contribution to fictional as well as non-fictional science writing is manifested through more than 100 books written by him. Concept of use of geostationary satellite for communication purposes is attributed to Arthur C. Clarke. He had been conferred several prestigious awards and honours. He was knighted by British Government to acknowledge his contribution to science writing. He was awarded UNESCO's Kalinga Prize for the Popularasation of Science in 1961.

{tab=Dynamic Venus}

Dynamic Venus...

     Jupiter bears a red spot on its 'surface'. It is nothing but a hurricane with gusty winds blowing across with enormous speed. Though much smaller than that on Jupiter, Venus also bears hurricanes in its polar regions. One that is sitting near the south pole of the planet is in the form of 2000 km wide vortex. This hurricane was detected in the year 1974 by Mariner 10 spacecraft. Now it is being studied carefully by Venus Express using infra-red imaging technique.

Infra-red images of hurricane taken in a total span of two days
(Yellow spot indicates South Pole of Venus)
[Credit: ESA]

     Scientists working with European Space Agency's Venus Express have found that core of the vortex is bright.  Shape of the vortex is also changing continually. The changes are so fast that the shape of the vortex will be seen different within few hours. Lot of atmospheric gases are probably moving downwards through it. Reason for the formation of the vortex is not clear. It may have something to do with the solar heating of gases near the equator. These hot gases rise through the Venusian atmosphere and move towards polar region and again sink down through the vortex. Venus's north polar region also has similar vortex which was discovered by Pioneer Venus in 1979.

{tab=Rhea 's ring}

Rhea 's ring...

     Can a natural satellite of a planet have rings around it? Yes! It can have. First of the candidates for this is interestingly Rhea, Saturn's second largest moon. Saturn itself is grandest example of a planet holding a ring system. The ring around Rhea was detected by Cassini spacecraft. This ring is in the form of a debris disc with a diameter of several thousand kilometers. In addition, there is a tenuous dust cloud accompanying the disc. The cloud extends upto about 5,900 km from the centre of Rhea. (Rhea has a diameter of about 1500 km.) Although no one had expected this long-discovered moon of Saturn to have a ring, it is not a total surprise. Numerical simulations based on Rhea's gravitational field and its orbit around Saturn have already shown Rhea's potentiality to hold a ring system. These recently published results are based on observations carried out by six different instruments.

Rhea's ring and dust cloud - faintly seen (Artist's concept)
[Credit: NASA]

     The ring  may be result of a collision of an asteroid or comet with Rhea. Gaseous material would have dissipated after the collision leaving the solids behind. The solid remnant probably contains rocks of varied size - right from pebbles to boulders. Norbert Krupp, a scientist from Cassini's team says -  “Like finding planets around other stars, and moons around asteroids, these findings are opening a new field of rings around moons!”

{tab=Avalanche on Mars}

Avalanche on Mars...

     Mars is known to have dust storms on its, otherwise, quiet terrain. Now Mars is known to have boisterous avalanches also. Recently NASA's Mars Reconnaissance Orbiter captured a live avalanche through its High Resolution Imaging Experiment camera. This camera has captured at least four such avalanches in the north polar region of Mars. Following photograph shows tan clouds uprising after the descent of dust, ice and frozen carbon dioxide over the cliff. Height of the cliff is about 700 meters high and is sloped at an angle of about 60°.

(Credit: NASA/JPL-Caltech/University of Arizona)

    Cause of the roll down is not clear. At present, spring is progressing in the northern hemisphere of Mars. Hence, it may be a change in the nature of ice or frozen carbon dioxide due to temperature variations. Or it can be a Mars-quake or even meteorite impact that has triggered the avalanche.

{tab=Farewell to Ulysses}

Farewell to Ulysses...

     Ulysses spacecraft was recently in news as it had gazed at region around North Pole of the Sun.  Now, Ulysses is again in news. But the news is bad. Death knell has started ringing for Ulysses. The equipments on Ulysses derive the required power from onboard radioactive source. This source is becoming weaker due to natural decay of radioisotope and losing its power output. This has affected functionality of not only scientific instruments but also essential facilities like heater. As the spacecraft moves away from the Sun, it will become colder. A further drop of only 2°C in the inside temperature of Ulysses will result in  freezing of hydrazine in the fuel tank. Ceasing of the supply of hydrazine will make maneuvering the path of spacecraft impossible. Attempts were made to divert the available power to heaters, by putting off the transmitter temporarily. After this attempt, unfortunately the transmitter failed to get restored to its normal active phase.

Ulysses and Sun (artist's impression)
(Credit: ESA)

     It is time to say farewell to Ulysses. This ESA-NASA mission had proved to be workhorse for solar scientists. And it continued to be so for 17 long years - about 4 times its expected lifetime! In any case, death of Ulysses was certain. ESA’s Ulysses Mission Manager Richard Marsden says - "This was going to happen in the next year or two, it has just taken place a little sooner than we hoped." Ulysses will lose its capabilities completely within a month or so.

(See: Passage to the Sun in February '08 Archives)