The MOST Humble Space Telescope

Space telescopes usually thought of as huge machines. The famous Hubble Space Telescope, for example, is 13.2 meters (43.5 ft) long and 4.2 meters (14 ft) in diameter. Though not all are so large; 800 kilometers above the Earth there is a satellite that is just 65 centimeters (about 25 inches) long – not larger than a large suitcase – proving that, when it comes to science, “size doesn’t matter”.

This astonishing device is called MOST (which stands for Microvariability and Oscillations of Stars). Although being very small compared to its peers, this satellite is helping scientists answer intriguing questions about stars, planets and even the Universe itself.

The MOST Space Telescope Credit: Canadian Space Agency

Staring at the Stars

Launched on June 30th 2003, MOST is the first space telescope to be entirely designed and built in Canada. As its name suggests, it is designed to take precise measurements of variations in intensity (the brightness) of stars in order to determinate their composition and age. The larger space telescopes cannot afford the time required for this task as to measure these oscillations, is necessary to keep the lens pointed at a single target in the sky for weeks at a time, and they can’t do so because of the high demand for their time.

Usually, astronomers use expensive ground-based telescopes to measure these stellar pulsations. However, this isn’t the best way to do so, since the readings are distorted by the Earth’s atmosphere. Moreover, the day-night cycle makes impossible to scientists to observe a star for 24 hours a day. Though with its orbit above the Earth’s atmosphere MOST can avoid both problems; and is able to look at any part of the sky continuously for up to seven weeks with a minimum of distortion.

The Secret life of Stars

The technology of this incredible telescope is helping astronomers figure out some very interesting things about stars, things well beyond our expectations. One of these discoveries was made as soon as the satellite became operational.

In 2004, the MOST team reported that Procyon (the brightest star in the constellation Canis Minor) shows no pulsations at all, contradicting more than 20 years of observations. Later, in 2006, the scientists realized that they were dealing with an unknown class of stars, the “slowly pulsating B supergiants”.

Furthermore, MOST has also been used to study exoplanets in alien star systems. Indeed, this is the only telescope – in space and on Earth – able to detect the light reflected by a planet orbiting around another star. Although not designed for this purpose, MOST is giving us a hint of what the atmosphere of those planets look like. It does this by detecting subtle variations in the light from either the planet or the star itself. MOST can see changes down to levels of one part to a million – or one ten thousandth of a percent!

“MOST has been very good at seeing things in the Universe that most people never expected or thought possible,” says Jaymie Matthews.

This post is part of the Young Astronomers’ Databank Project

Origins of the Moon Challenged

The commonly accepted theory among scientists concerning Moon formation could be altered by a new study of lunar isotopes. (Variations of elements containing differing amounts of neutrons).

Luna Credit: NASA

Nearly half of the Moon was postulated to be from Theia, a planetary body, thought to have collided with Earth four point five billion years ago. The recent study by Junjun Zhang, an isotope geo-chemist at the Chicago Center for Cosmo-chemistry and his team challenged this premise. Initially, an analysis of twenty-four rocks from the lunar surface revealed a paucity of indications concerning similarities between the Moon and Earth. However, the group failed to consider the effect of cosmic rays, streams of charged particles racing through space. After amending their research on the Moon’s isotopes of titanium, they found its ratio to be in the ballpark of our planet’s chemistry.

The unlikelihood of Theia’s chemistry being nearly identical to the Earth prompted scientists to reconsider their model. They theorized, perhaps the planetary body collided and caused more joining of debris than previously suggested. This could infer, the majority of Theia’s constitution is hidden deep within the Moon, while Earth’s composition lays conspicuously on the surface.

Suggestions of a collision between a dual moon systems arose as well, inferring that one of our past satellites had a chemistry similar to the Earth. Scientists cannot know for sure, whether their ideas are correct or not, they are still theories. However, the research team plans on conducting more experiments on the isotopes of different elements found on the Moon.

You can read more about these findings at http://news.yahoo.com/moon-formation-theory-challenged-study-160608598.html

Astronomy Tech – Cassini-Huygens – Recovered

Since the beginning of the Space Age, man has sent many manned and unmanned missions into space. Very powerful telescopes, built around the world, broaden our vision and understanding of the universe. Spacecraft, whether visiting other worlds or orbiting the Earth send us images and data collected from our outer atmosphere to the outer planets and beyond.

However, all this was only possible thanks to the incredibly rapid development of technology in recent years. Only then, could the essential resources for the construction of the current generation of spaceships be developed.

So, let us talk a little about some of the most important of space exploration’s tools and its greatest discoveries in this series, called Astronomy Tech.

In this first post, let’s get to know Cassini-Huygens a bit better. It is a joint mission between NASA, the European Space Agency (ESA) and the Italian Space Agency (ISA), which has uncovering the secrets of Saturn, including its rings and moons, as its primary objective.

An artist's impression of Cassini-Huygens Credit: NASA

On October 15th, 1997, the Cassini-Huygens spacecraft – composed of NASA’s Cassini orbiter and the ESA’s Huygens probe – was launched, beginning a long and complex seven-year journey, including gravitational slingshot manoeuvres around Venus, Earth and Jupiter. After arriving at its destination, the mother ship; Cassini, began its main objective exploring Saturn, whilst the Huygens probe was lunched and landed on Titan –Saturn’s largest moon and the second largest in the Solar System, after Jupiter’s moon Ganymede.

The spacecraft’s name was a tribute to the Italian Jean-Dominique Cassini (1625-1712) – discover of the Saturnine satellites Iapetus, Rhea, Tethys and Dione. In 1675 he discovered what is known today as the ‘Cassini Division’, the narrow gap separating Saturn’s A and B rings. Christiaan Huygens (1629-1695) was a Dutch scientist who first described Saturn’s rings and, in 1655 he discovered the moon Titan.

Cassini’s “senses”

The Cassini spacecraft has a set of 12 instruments on-board. Some of them work in similar ways to our own. However, the instruments on the Cassini spacecraft are much more advanced than our own.

Cassini can “see” in wavelengths of light that the human eye cannot. The instruments on the spacecraft can “feel” things about magnetic fields and tiny dust particles that no human hand could detect. This means that Cassini can, for example ‘see the temperature’ of the objects it observes.

The magnetic field and particle detectors take direct sensing measurements of the environment around the spacecraft. These instruments measure magnetic fields, mass, electrical charges and densities of atomic particles. They also measure the quantity and composition of dust particles, the saturation of plasma (electrically charged gases), and radio waves.

Exploring the Ringed Planet

The expected return to Saturn – which hadn’t been visited by any spacecraft since Voyager 2 left Saturn’s orbit in 1981, – happened in July 2004. Since then, Cassini has made great discoveries about the Saturnine System and taken some terrific pictures, like the one below.

An Eclipse of Saturn, with the Rings Visible Credit: Cassini/NASA

A few days after reaching Saturn, Cassini released the Huygens probe to land on Titan. On January 14, 2005, during its fall, six instruments analysed Titan’s atmosphere. According to the returned data, Titan has a nitrogen rich atmosphere. It also confirmed that Titan’s orange colour is due to the presence of hydrocarbons, formed when sunlight breaks down the abundant methane molecules within the atmosphere.

These results have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many similarities to the Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.

Cassini’s mission

Isn’t over yet; every day, it sends us vast amounts of data, back to astronomers allowing them to resolve and answer questions about Saturn and our own planet.

You can see more about Cassini on its official website. If you want to hear the news first hand, you can follow Cassini on Twitter.

Potential Research at the Poles

Note from the Young Astronomers Admin Team:

This is the first by our new editor YusefK and we would all like to welcome him to the team!

When you picture the world’s best site for astronomy, places like the Gemini Observatory in Chile or the W.M. Keck in Hawaii probably come to mind. Well think again, because the new epicenter of observing could be the coldest place on earth, Antarctica. After performing a careful analysis of the continent, scientists from America and Australia have pinpointed a prime location for ground based research. Several countries have already laid claim to the icy real estate, such as China, France, Russia and South Africa. The success of these countries’ scientific bases led to the development of more stations. We could owe our future understanding of the universe to those who work and live in this region.

Antarctica Credit: NASA, Davepape

Radio astronomers have already conducted research in the polar area. It was Martin Pomerantz who postulated that Antarctica was the best place for ground based astronomy. He was correct, but only under certain wavelengths. Until now, those who wanted to see the universe were out of luck. Nevertheless, the new site found by American and Australian scientists is expected to yield images three times sharper than today’s best observatories. Those of us who spend clear nights under the stars understand the importance of certain atmospheric factors. Things like water vapor in the air, temperature changes and darkness greatly affect our observing.

The location of this new site is a frozen plateau called Ridge A. Ridge A’s atmosphere is steady enough for average instruments to perform better than today’s common observatories. Imagine the potential of an eight inch Cassegrain in perfect weather conditions and the images would be stunning, when the larger facilities are established. The night sky above the summit is perfect for astronomical observing because it is calmer, dryer and darker than any ever known. Those who study and live in Antarctica will benefit from this treasure trove of unexplored skies. However, they will have to contend with several inhospitable factors foreign to the common scientist.

Living in Antarctica seems to be a challenge taken by the very eccentric or very passionate. Generally, scientists take a plane to the Falkland Islands and then a ship to Antarctica. There, they work with several professionals in the coldest and driest place on earth. Nevertheless, I have read the quarters are comfortable and the canned food isn’t half bad, either. Scientists work with a diverse group of people for months at a time and under strange and adverse conditions. So, for all budding astronomers and researchers, consider the South Pole for future endeavors in understanding the universe.

Sources:

http://www.antarctica.ac.uk/employment/locations/antarctica/living_in_antarctica.php

http://www.nsf.gov/pubs/1997/antpanel/4past.htm

http://www.physorg.com/news170932769.html

http://www.universetoday.com/38749/astronomers-find-worlds-best-observing-site/

The International Space Station

240 miles above your head a 420 tonne satellite orbits the Earth at 17000mph. It has been there, albeit in various states of construction, for 14 years, and for the last 11 of those it has been continuously occupied.

The fantastic photo taken by Italian ESA astronaut Paolo Nespoli from a Soyuz capsule that is currently my desktop background. Source: ESA/NASA

The International Space Station is a feat of engineering like no other. Not only does it demonstrate our technical ability to construct, launch, and maintain a permanent presence in space, but also our ability to coordinate the work of five different space agencies and their operations all over the planet.

But the journey from its conception has not been an easy one, the ISS was born out of three separate national programmes: NASA’s Freedom station, proposed in the early ‘80s as a response to the Soviet space stations Mir and Salyut, the Russian (formerly Soviet) Mir-2 project designed as a replacement for the aging Mir station, and the European Columbus space station project.

Budgetary constraints brought on by post-Cold War political changes made it increasingly clear that no single national programme was going to create a fully functioning scientific outpost. Instead the suggestion to combine the three programmes into a single international one was put forward and agreed in 1993 by US Vice-President Al Gore and Russian Prime Minister Viktor Chernomyrdin.

The first component, the Russian Zarya cargo block originally intended for the Mir-2 station was launched in 1998, and since then the station has expanded, first with the addition of connecting and services modules such as NASA’s Unity and RKA’s Zvezda, and later with more specialist modules such as ESA’s Columbus laboratory and the Cupola observation module, the largest window in space. In total the ISS consists of fifteen pressurised modules, with one more, Russian research laboratory Nauka still to be added. They comprise laboratories, docks and airlocks, and living areas, and their combined volume is just less than 1,000 cubic metres.

That all of these modules fitted together perfectly is a success story in itself. Many had not been built when the first pieces were launched, and for most their mating in orbit was the first time they were put together. Though there have been a few minor problems, they have always been resolved quickly, and at no point has the station ever had to be evacuated.

The station’s unique conditions have allowed a large variety of experiments to be performed, many of which would be impossible on Earth. Research is being done into how structures such as crystals and organic cells form and develop outside the influence of the Earth’s gravity. NASA is also taking the opportunity to do closer studies on the effects of prolonged exposure to microgravity on astronauts and the possible implications on future manned missions to the Moon, asteroids, or Mars.

Until the end of the shuttle program in August of last year, crew and supplies were transported by a variety of means including the space shuttles, and the Soyuz and Progress spacecraft. The 6-man Soyuz craft operated by Roscosmos, the Russian Federal Space Agency, is now the only method of sending new crews to the station.

Each contributory nation retains ownership of and responsibility for the components that it added. This responsibility extends to the disposal of the station when it reaches the end of its operational life, which the current time frame places somewhere in the 2020s, depending on whether and for how long its decommissioning is postponed after the initial 2020 date. Given the huge amount of money that has been invested in the station as well as the later than expected completion date, it is very likely that the ISS’s operational life will be extended some way beyond that deadline. By that point it is also expected that commercial space ventures will play a much larger role in the life and upkeep of the station, so they too may play some role in its end-of-life decisions.

The Life of Discovery – Recovered

This post has been produced by VanessaG for the Young Astronomers

Discovery, with her maiden flight on 30 August 1984, with STS-41D. On the ascent she carried more than 41,000 lbs of cargo which was a record at the time. This cargo was mainly science experiments to study the effects of microgravity. Discovery was also the first shuttle to retrieve a satellite and bring it back to Earth. In 1985 Discovery was the first shuttle to fly four missions in one year.

Discovery as seen from the ISS during STS-128 Credit: NASA

On STS-51D the first sitting member of the US congress blasted off into orbit, Jake Garn, the republican senator of Utah. During the landing she suffered a blown front tire and subsequent brake damage. This then meant that all further flights for five years were directed to land at Edwards Air Force Base, California until nose wheel steering was introduced and brakes improved.

After the Challenger and Columbia disasters it was Discovery who was called upon to return the US to space again and regain their independence. The return after Columbia, STS-114 under the leadership of Eileen Collins; who earlier on STS-63 was the first female pilot. This mission was also the first to do a back flip on approach to the ISS so that the station crew could photograph the underside of the shuttle which then could be studied to check for damage. This was also the first time a repair had been made to a spacecraft while in orbit, the EVA crew removing two protruding spacers in the thermal shielding.

In April 1990, on STS-31, Discovery released the Hubble Space Telescope. This was also the highest ever flown by a shuttle at 380miles. And the ‘scope is still in use twenty years later and continues to provide valuable insights into the beginnings of the universe.

STS-60, February 1994, was the first co operative mission between the then enemies of Russia and the US. This laid the foundations for international cooperation which is one of the fundamental aspects of the International Space Station. With a Russian cosmonaut flying about the American shuttle Discovery. Discovery’s next flight, STS-63 was the first mission to be piloted by a woman, Eileen Collins, who laid further foundations into international cooperation as she piloted Discovery to within 40ft of MIR. Correcting the final approach for the first shuttle docking with the Russian space station.

Discovery has seen many other significant events in international development, the first spacewalk by an African-American, the last shuttle to visit MIR. The oldest astronaut, John Glen on board STS-95 who at the time of the flight was seventy seven, and still is the oldest person to ever fly in space.  Discovery also celebrated the 100^th shuttle fight on board mission STS-92. And on STS-120 lead by commander Pamela Melroy met Peggy Whitson, commander of Expedition 16 on board the ISS in 2007. This not only was not only the first time the ISS has been commanded by a woman but the first time two female commanders met in space.

In her 26 year lifetime Discovery has achieved many great things in the world. Not only advancing science but also cooperation and technology that you will use everyday. In total 180 people have travelled on board Discovery and a total of 150 million miles have been travelled in orbit.

Discovery Launches to Begin STS-128 Credit: NASA/Jerry Cannon, George Roberts

Japanese Solar Sail Craft with LCDs! – Recovered

This post has been produced by DeepikaG for the Young Astronomers

This is innovation at its best. Scientists at JAXA (the Japan Aerospace Exploration Agency) not only created a satellite with solar sails (something poor guys at the planetary society will probably be fuming at) but created an innovative method to control its attitude, not by using rocket motors but a simple liquid crystal display. Yes this is the same stuff used to make the displays in your calculators and watches!

The liquid crystal device on the craft is a thin-film instrument that changes the surface reflection characteristics of sunlight by turning on and off the power of the device.

Location of the LCDs on the IKAROS craft, Image Courtesy: JAXA

For the uninitiated, a solar sail works just like an ordinary wind-sail. The major difference being that instead of wind, it uses pressure generated by incident light radiation from the sun. When electromagnetic radiation is incident on a solid, it exerts a small force on the target, that may cause it to move. Solar sails ave potential application in deep space missions, as the maximum theoretical speed gained from a solar sail is the speed of light!

The difference in solar pressure is used to generate torque and re-orient the spacecraft.

The IKAROS was launched from the Tanegahima Space Center on May 21, 2010.

Related Links:

How Solar Sails work 
Planetary Society Solar Sail Initiative

Astronomy Tech – Mars Exploration Rovers – Recovered

This is an article by JansenP for the Young Astronomers

Artist's concept of a rover working on Mars. Credit: NASA

Apart from the Earth, Mars is the most explored planet in our Solar System. Since the 1960’s, dozens of spacecraft have been sent to orbit and, in some cases, land on our planetary neighbour.

Mars does not seem an interesting place at first glance: the low temperature and pressure have given the planet a very hostile environment. However, some pictures, taken by spacecraft orbiting Mars and telescopes on Earth, suggest that the early Mars was wetter and more “hospitable” than it is today. So, did Mars once have water flowing on its surface; and if so, how long ago?

To answer these questions, NASA sent two robotic rovers to the red planet– named Spirit and Opportunity – to study two different areas of the Martian surface and look for any evidence that there was once liquid water on Mars.

Getting to Mars

Spirit and Opportunity were launched separately in June 2003 and arrived at the red planet in January 2004. Nevertheless, this long trip was not the worst part: the biggest preoccupation of the mission scientists was landing the robots on Mars safely. In the video below you can see how difficult – and terrific – this task was.

Credit: NASA

Robotic geologists

As we already said, this mission has as main objective finding signs of past water on Mars. To do so, the robots are loaded with instruments to grab and analyze rocks.

Artist's rendering of one of the rovers using the RAT on Mars. Credit: NASA

Both rovers have a robotic arm with a drill – called a Rock Abrasion Tool (RAT) – that can bore into a rock and, through a camera mounted at the same arm, the scientists can check out the rock’s inner composition. This is needed because the huge amount of solar radiation striking the surface of the planet  and the Martian dust have given to rocks a kind of “rind” that covers the minerals that scientists want to study.

The robots are also equipped with nine cameras – from a microscopic imager to a high-resolution panoramic camera –, spectrometers (tools to identify the composition of a body measuring its light spectrum) and a lot more. Even the rovers’ wheels in addition to allowing mobility, are used to dig shallow trenches to evaluate soil properties.

Another interesting feature of Spirit and Opportunity is that they are autonomous, this means, they can move and control themselves. For example, when the scientists look at a rock in the landscape, they can tell the rover to “go check out that rock,” and it will drive over to that rock and examine it. This allows the rovers to be much more useful as the time lag for radio signals to travel between Earth and Mars (which varies between 3 to 30 minutes roughly) is too great for the rovers to be directly radio controlled.

Finding the traces of water

Two months after land on Mars, Opportunity found, in a thin rocks outcrop in Eagle Crater, rocks rich in sulfate-salts, evidence that salt water flowed once over them. Preliminary interpretations point to a past environment that implies this crater could have been hospitable to life and could have preserved fossil evidence of it, though these rovers are not equipped to detect life or to be fossil hunters, such duties will be carried out by future, perhaps manned missions.

This is an image of a meteorite that Opportunity found and examined in September 2010. Credit: NASAJPL

Spirit, during its primary mission (which in this case meant, the first 90 days), explored a plain strewn with volcanic rocks and pot-marked with impact craters. It found indications that small amounts of water may have found their way into cracks in the rocks and may have affected some of the rocks’ surfaces.

Unfortunately, since 2009, Spirit has been stuck in a sand dune and probably will never free itself. As Spirit’s instruments were, and are in very good health, NASA decided to turn the robot into a “Martian observatory”: to look at the stars, clouds and to study the weather and landscape of Mars.

Opportunity continues working hard. It is now located at Santa Maria Crater. There, the rover found other interesting minerals that can only form in presence of water for a long period. The next big objective for Opportunity is to head for the Endeavour Crater and to analyse the minerals present on its rim.

As of January, both rovers have completed 7 years of work on Mars – a much longer time than was expected of either them, let alone both. The primary mission was expected to be last three months after the spacecrafts’ landing, i.e. until April 2004. As the vehicles were still doing well, NASA decided to extend the mission.

So, even as you read this the Mars Exploration Rovers still looking for water on Mars and changing the way we look at the Red planet.

You can see the latest news about the twin robots at the mission’s official website.

Revolutionary Astronomical Words – Recovered

This post is by AliceS for the Young Astronomers.

Admin note: Alice would like me to note that this was the first post she produced for the Young Astronomers, and that the content is quite old. She has however made several alterations since the post was originally released.

Hello everyone, and thanks to the Young Astronomers for allowing me aboard despite being a comparatively crumbly non professional astronomer! Now, assuming I can get WordPress to bend to my will, my first post is going to be about words in astronomy that end up not meaning quite what they should, if they don’t want to be misleading. Like all sciences, astronomy is done pretty much in the dark (sorry about that) – and sometimes names stick before we know what we’re actually talking about. Here are a few.

Revolution

When we hear of revolts and revolutions, we think of noisy coup d’etats in which the angry mob displaces the, er, other angry mob – and either things improve for the country in question or they don’t, but in any case, it’s a radical change. But the word “revolution” actually means “going round in a circle”. The Earth completes one revolution round the Sun every – you got it – year. Doesn’t seem a very revolutionary word, does it?

It came from Copernicus. His revolution was, really, the ultimate revolution in Science: the recognition that we are not at the centre of the Universe; that, rather, we revolve around the Sun. The book he wrote (which was only published just before he died, as he knew it wouldn’t be popular!) was called “De revolutionibus orbium coelestium”, or “On the revolutions of the heavenly spheres”. It was a revolution, because it called into question the dogma of the day that the entire Universe was created for us.

Handmade oil painting reproduction of The Copernican System by Andreas Cellarius, devised by Nicolaus Copernicus.

(Picture credit: this online art gallery!)

Which, incidentally, led on to . . .

Planets

The word “planet” comes from Greek, and means “wandering star”. Ancient people had no way to tell a planet from a star, except for its odd motion – moving in comparison to the rest of the stars in the sky, which of course was because all planets orbit the Sun at the same distance – and the fact that they don’t twinkle the way stars do. Both basically looked like points of light, and, with a little hard (if incorrect) thinking, might just as well be fixed to “celestial spheres”. Stars, of course, give off light of their own, not reflect their star’s light as a planet does.

In fact, the Sun and the Moon were also originally called “planets”. Gradually the word “planet” came to mean “world that is not a star” – one discovery that helped this along was Galileo’s sighting of Jupiter’s moons in 1610.

But of course the definition of “planet” has changed more than once since then. People seem to feel for some reason that Pluto has been harmed by no longer being known as a planet. In fact we now know that so many different types of objects orbit the Sun in our Solar System, we need to reclassify them somehow!

So, lots of changes as science progresses. To be fair on the ancient Greeks, they couldn’t planet to happen . . .

Planetary Nebula

This is the name for beautiful nebulae such as the Cat’s Eye Nebula. They are actually nothing to do with planets, but apparently looked like them in the 18th century when telescopes were not poweful enough to tell the difference.

The Cat's Eye nebula, a "planetary nebula" from a star too small to explode as a supernova. Credit: NASA

A planetary nebula is a much more gentle and orderly shell of gas than a supernova remnant. It is created when a small or medium star, like our own Sun, puffs off its outer layers at the end of its life. It’s often very hot, ionised gas, and is therefore an emission nebula – shining with its own light. It also contains elements such as carbon and oxygen, which are essential for forming rocks, planets, and life.

The word “nebulae”, however, does at least mean clouds. Astronomers referred to “spiral nebulae” many years ago, believing these to be beautiful spiral-shaped clouds at the same sort of distances as the stars in our Galaxy. They had no idea that these were galaxies millions of light years away from our own!

Astrology/Astronomy

Once upon a time, these two words meant the same thing. In the days when it was essential to know when to expect floods or plant your crops, and indeed when there were no TVs or streetlights at night, people would have known the sky very well. It would make perfect sense to think, “When such-and-such a constellation rises above that hill, it’s time to plant this out”, or “Oh dear, that one. The weather will be bad soon.” Into the Middle Ages, royals employed professional astrologers. A British tabloid newspaper claimed that Dr Brian May, the Queen guitarist who is also an astronomer, has a PhD in astrology . . .

Any word ending in “-ology” (biology, geology etc) usually means science. However, as the science and the myths separated, they needed two different names. They now have pretty well nothing to do with each other – but a lot of people don’t believe me when I say that!

Nova

The word “nova” implies newness. However, a nova is a star so old that it’s no longer strictly a star. It’s a massive explosion caused by the accretion of gas onto a white dwarf. This explosion makes it look as if a new star has appeared in the sky, hence the name.

This white dwarf is pinching this gas from a nearby star, usually in a binary system; every so often, it acquires enough for fusion to start again. It has to reach about 20 million Kelvin to do this, as a white dwarf is made of extremely compressed material which contains no hydrogen fuel to fuse (otherwise it would still be a star!). In order to make this even simpler, novae are not to be confused with supernovae, although a Type I supernova can result from the same sort of process.

The Big Bang

Time and again I’ve been told almost angrily: “It doesn’t make sense. The Big Bang was an explosion, so how could it create such an ordered Universe?”

The term “Big Bang” was actually coined as a derogatory joke, byFred Hoyle, who preferred the steady state theory (that the Universe remains the same size and had no beginning). He said in the 1960’s on a radio program something along the lines of that he didn’t believe the Universe could have begun in one big bang. The name stuck!

We will never know what sort of noise it made – of course, even if we’d been around to hear it, it would have been so incredibly hot and violent that we’d have been smashed to bits. Certainly everything would have been bumping into each other a lot. There were no atoms and molecules as we know them, let alone solid objects or stars – everything was a seething plasma of atomic nuclei, electrons, and most of all radiation. It’s particles bumping into each other that make noise. But when the Big Bang occurred, any noise that occurred would have been inside it.

That’s because any explosion we think of today is nothing like the Big Bang at all. An explosion happens in one place, and its shock waves – flying shrapnel, for instance – fly out and damage their surroundings. The Big Bang didn’t have any surroundings. It’s easy to think of it as an expanding globe, with a centre and an edge. We think of the edge as rippling through something – perhaps the Earth! – at some point in time.

It sounds like it took place – in, well, a place. Somewhere we could go and visit. From there we’d see the evidence of destruction, perhaps everything rushing away . . .

That is everywhere and nowhere. The Big Bang happened right where you’re sitting. It happened across the room for you, and it happened on the other side of the Universe. It’s quite a mind-blowing thought. But it really wasn’t much like a bomb!

An artist's impression of the size of the Universe at the time of the Big Bang, then inflation, then its expansion. Credit: NASA / WMAP Science Team

It was really quite complex too, with inflation, and a period of darkness (because all the atomic nuclei and electrons were flying around in too disorderly a manner to let light through. This is what happens inside a cloud – there’s too much stuff in the way, so light bounces off everything in random directions and goes any old where. It also means it’s relatively dark).

And guess what else? It wasn’t big at all. It was small. It wasabsolutely tiny – smaller than the head of a needle – perhaps smaller than an atom! How did all this stuff in the Universe today come out of something so small? We don’t know. In fact, theoretically, such an object shouldn’t exist. It’s called a “singularity”, and it means, because it’s too small even to have a size, it must have infinite density. But we know there are black holes which are also singularities – and, really, when we look at the earlier Universe and see how much smaller and hotter it was, and when we do the mathematics, it’s the only conclusion we can come up with.

It’s not only how we began, but it’s an immense – and immensely complicated – puzzle. It’s odd to think that something so huge and important could have such a jokey, normal name. But Universes happen before words do!

Alice

Curiosity’s Power Source

This article was produced by JansenP for the Young Astronomers

NASA has just launched the Mars Science Laboratory (MSL) from the Kennedy Space Center, in the United States. The new rover, a car-sized robot known as Curiosity, is designed to wander around the Gale Crater, on Mars to determine if the area has – or had – the environmental conditions required to support life.

It’s scientific payload is composed of 10 instruments, and each depends on electric power to operate. The energy solution adopted by rovers until now – like Spirit and Opportunity – was to catch the energy of sunlight through solar arrays. The MSL in contrast, doesn’t have solar panels to take advantage of this energy. Instead, it has a system that converts the natural heat from the decay of a radioactive material into the electricity needed to operate the rover’s instruments, robotic arm, wheels, computers and radio.

An Artist's conception of Curiosity on Mars Credit: NASA/JPL-Caltech

Transforming Heat into Electricity

A pellet of Plutonium-238. It glows due the energy released by its radioactive decay Credit: U.S. Department of Energy

The power system, the -Multi-Missions Radioisotope Thermoelectric Generator (MMRTG), is basically a nuclear battery that transforms the heat given off by a radioactive isotope (or radioisotope) source into electricity to power the probe. The heat source chosen was a 4.8 kilogram (10.6 pounds) pellet of plutonium-238 dioxide (²³⁸PuO₂). This system is intend to generate about 110 watts of electrical power for at least 14 years – the MSL mission is expected to last two years, but this deadline may be extended.

Radioactive isotopes can be used as fuel because they have a very interesting propriety: due their instability, the nuclei of these isotopes (an isotope is a variation of an element i.e. – atoms of the same chemical element, but with different masses) can spontaneously “break”, turning the atom into a different element– this process is called radioactive decay. During the process, the atom release energy in form of heat that can be used by a thermoelectric generator to produce electric power.

To make this thermoelectric conversion, the generator uses a physical process known as Seebeck effect, discovered by the German physicist Thomas Seebeck. It consists of two plates, each made of a different metal. Joining these two plates to form a closed electrical circuit and keeping the two junctions at different temperatures produces an electric current. These pairs of junctions are called thermocouples.

To create this temperature difference, one of the plates is heated by the radioisotope’s decay, while the other one remains unheated and cooled by the environment.

The MMRTG also charges two lithium-ion batteries. They can be used when the rover’s energy demand temporarily exceeds the steady output level of the generator, this may occur depending on the activity the rover is performing.

Reliable Energy Anytime, Anywhere

The MMRTG is a new generation of radioisotope generators, very similar to others already present in several space missions, such as Galileo, Cassini, Voyager, New Horizons, Pioneer, Ulysses, Viking and even the manned Apollo missions to the moon. However, the MMRTG is designed to operate both on planetary bodies with an atmosphere – like Mars – and in the vacuum of the space. Moreover, on the MSL the temperature control system will use the waste heat from the radioactive decay to warm a fluid that will be pumped throughout the rover to keep the electronic components within their operating temperature range.

The Mars Science Laboratory's MMRTG, before being installed Credit: NASA/Kim Shiflett

Compared to the solar power alternative studied by MLS’ designers, the MMRTG proves to be lighter and smaller, providing a significantly better mobility and flexibility to the rover’s operations. Furthermore, as the system doesn’t depend on sunlight, it can deliver energy to the robot at anytime, even during the long Martain nights.

Though the  implementation of radioactive material as a fuel requires special care. Hence, the MMRTG was built with several layers of protective material designed to contain the plutonium-238 in case of a wide range of potential accidents, such as impacts or problems during a launch. Fortunately, the type of plutonium present in the radioisotope power system is different from the material used in nuclear weapons and could never explode like a bomb.

The use of these nuclear batteries have expanded the frontiers of space exploration. Thanks to radioisotope generators, we were able to visit other worlds and send missions beyond the limits of the Sun’s influence, they have enabled achievements that would otherwise not be possible. Now, this revolutionary system will allow us to go even further and explore the mystery of life on Mars.