ASTRONOMY CORNER

Spirit stopped rolling with its base petal down, though that favorable position could change as airbags deflate.

NASA chose Spirit's landing site, within Gusev Crater, based on evidence from Mars orbiters that this crater may have held a lake long ago. A long, deep valley, apparently carved by ancient flows of water, leads into Gusev. The crater itself is basin the size of Connecticut created by an asteroid or comet impact early in Mars' history. Spirit's task is to spend the next three months exploring for clues in rocks and soil about whether the past environment at this part of Mars was ever watery and suitable to sustain life.

Spirit traveled 487 million kilometers (302.6 million) miles to reach Mars after its launch from Cape Canaveral Air Force Station, Fla., on June 10, 2003. Its twin, Mars Exploration Rover Opportunity, was launched July 7, 2003, and has landed on the opposite side of Mars on Jan. 25

http://marsrovers.jpl.nasa.gov

One of the main targets of the Mars Express mission is to discover the presence of water in one of its chemical states. Through the initial mapping of the South polar cap on 18 January, OMEGA, the combined camera and infrared spectrometer, has already revealed the presence of water ice and carbon dioxide ice.

ASPERA, a plasma and energetic neutral atoms analyser, is aiming to answer the fundamental question of whether the solar wind erosion led to the present lack of water on Mars. The preliminary results show a difference in the characteristics between the impact of the solar wind area and the measurement made in the tail of Mars. Another exciting experiment was run by the SPICAM instrument (an ultraviolet and infrared spectrometer) during the first star occultation ever made at Mars. It has simultaneously measured the distribution of the ozone and water vapour, which has never been done before, revealing that there is more water vapour where there is less ozone.
 
ESA also presented astonishing pictures produced with the High Resolution Stereo Camera (HRSC). They represent the outcome of 1.87 million km2 of Martian surface coverage, and about 100 gigabytes of processed data. This camera was also able to make the longest swath (up to 4000 km) and largest area in combination with high resolution ever taken in the exploration of the Solar System. 

On Jan. 2nd, 2004, NASA's Stardust spacecraft approached Comet Wild 2 and flew into a storm. Flurries of comet dust pelted the craft. At least half a dozen grains moving faster than bullets penetrated Stardust's outermost defenses. The craft's 16 rocket engines struggled to maintain course while a collector, about the size of a tennis racquet, caught some of the dust for return to Earth two years hence.

All that was expected.

Then came the surprise. It happened when Stardust passed by the core of the comet, only 236 km distant, and photographed it using a navigation camera. The images were intended primarily to keep the spacecraft on course. They also revealed a world of startling beauty.

At the heart of every comet lies a "dirty snowball," a compact nucleus of dust and ice that the sun vaporizes, little by little, to form the comet's spectacular tail. These nuclei are hard to see. For one thing, most are blacker than charcoal; they reflect precious little sunlight for cameras. Plus they're hidden deep inside a cloud of vaporizing gas and dust, called "the coma." Stardust's plunge into Wild 2's coma allowed it to view the nucleus at close range.

Previous flybys of Comet Halley by the European Giotto probe and Comet Borrelly by NASA's Deep Space 1 revealed lumpy cores without much interesting terrain--as expected. These comets have been sun-warmed for many thousands of years. Solar heating has melted away any sharp features

Astronomers in England have discovered a singing black hole in a distant cluster of galaxies. In the process of listening in, the team of astronomers not only heard the lowest sound waves from an object in the Universe ever detected by humans, but they've also discovered an important clue about the formation of galaxy clusters -- the largest structures in the cosmos.

Dr. Andrew Fabian and his colleagues at the Institute of Astronomy in Cambridge, England made their discovery using NASA's Chandra X-ray Observatory, an orbiting X-ray telescope that sees the Universe in X-ray light just as the Hubble Space Telescope sees it in visible light.

The black hole is situated in the center of a galaxy amid a group of thousands of galaxies collectively called the Perseus Cluster and located 250 million light years from Earth (meaning it took the light from these galaxies 250 million years to reach us). The sound waves coming from it are in the form of a single note, so rather than a song it is really a drone.

Using the piano keyboard's middle C note as a reference point for the middle of the piano key music range, Fabian's team determined the note is a B -flat. On a piano, the B-flat nearest middle C is located midway between 1/8th and 2/8th of an octave away. In musical terminology, this B flat is 1-1/2 steps from middle C.

The Perseus cluster black hole's B-flat, by contrast, is 57 octaves below middle C or one million, billion times lower than the lowest sound audible to the human ear! In terms of frequency (the time it takes a single sound wave to pass by), the lowest sounds a person can hear is 1/20th of a second. The Perseus black hole's sound waves have a frequency of 10 million years!

You may be wondering how a sound wave can travel through space. After all, sound waves require some sort of stuff to move through. This stuff, called a medium, can be air, water, or even solid rock. And space is thought of as lacking any medium because it is a vacuum.

In fact, space is not a pure vacuum but rather it contains stray bits of stuff -- gas atoms and dust of varying amounts. In the case of the Perseus cluster, the gas throughout it serves as the medium through which the sound waves coming from the central black hole travel.

The sound waves were indirectly detected using the Chandra telescope because the cluster gas is very hot and thus emits an especially energetic form of light called X rays, as well as less energetic visible light. And the gas is so hot because of the effects of the black hole.

More than an acoustic curiosity, these sound waves transport energy that keeps gas throughout the cluster warmer than it would otherwise be. These warmer temperatures, in turn, regulate the rate of new star formation, and hence the evolution of galaxies and galaxy clusters. This makes the findings far more significant for understanding the astrophysical evolution of the Universe.

The Perseus sound waves are much more than just an interesting form of black hole acoustics, said Steve Allen, also of the Institute of Astronomy and co-investigator in the study. These sound waves may be the key in figuring out how galaxy clusters, the largest structures in the Universe, grow.

The cosmic diamond is a chunk of crystallised carbon, 4,000 km across, some 50 light-years from the Earth in the constellation Centaurus.

It's the compressed heart of an old star that was once bright like our Sun but has since faded and shrunk.

Astronomers have decided to call the star "Lucy" after the Beatles song, Lucy in the Sky with Diamonds.

Twinkle twinkle

"You would need a jeweller's loupe the size of the Sun to grade this diamond," says astronomer Travis Metcalfe, of the Harvard-Smithsonian Center for Astrophysics, who led the team of researchers that discovered it.

The diamond star completely outclasses the largest diamond on Earth, the 530-carat Star of Africa which resides in the British Crown Jewels.

The huge cosmic diamond - technically known as BPM 37093 - is actually a crystallised white dwarf. A white dwarf is the hot core of a star, left over after the star uses up its nuclear fuel and dies. It is made mostly of carbon.

For more than four decades, astronomers have thought that the interiors of white dwarfs crystallised, but obtaining direct evidence became possible only recently.

The white dwarf is not only radiant but also rings like a gigantic gong, undergoing constant pulsations.

"By measuring those pulsations, we were able to study the hidden interior of the white dwarf, just like seismograph measurements of earthquakes allow geologists to study the interior of the Earth.

"We figured out that the carbon interior of this white dwarf has solidified to form the galaxy's largest diamond," says Metcalfe.

Astronomers expect our Sun will become a white dwarf when it dies 5 billion years from now. Some two billion years after that, the Sun's ember core will crystallise as well, leaving a giant diamond in the centre of the solar system.