5th June, 2006: To boldly go where no SAO student has gone before

... and I can anticipate the question that is on the tip of your tongue right now - Which subjects is Anousheh taking this semester? Well, "Exploring the Solar System" and "Studies in Space Exploration" of course - just like any budding astronaut should! :-)

We wish Anousheh a safe journey and we look forward to hearing of her experiences when she eventually embarks on this spectacular journey.

SAO student, Anousheh Ansari, on astronaut training off the coast of Sevastopol in the Black Sea.

15th May, 2006: Even old stars have wind problems

When a sun-like star reaches the final stages of its life, typically at an age of roughly 10 billion years, it expands into an enormous red giant. Over a period of a few hundred thousand years, much of the star's mass is expelled at a relatively slow speed of about 80,000 km per hour. This stellar wind creates a more or less spherical cloud around the star which is known as a planetary nebula - a confusing term which is more a description of how these object appears in small telescopes than something to do with planets.

In time, the mass loss caused by the wind eventually uncovers the star's hot core. The intense ultraviolet radiation emanating from the core heats the gas surrounding the star to ten thousand degrees and subsequently increases the velocity of the gas flowing away from the star to about 1.5 million km per hour! This high speed wind concentrate into opposing supersonic funnels, and produces elongated shapes in the early development of the planetary nebulas - the cause of the funnelling is not yet understand but is believed to be related to the strong, twisted magnetic fields near the hot stellar core. Some planetary nebula, such as in BD+30-3639, appear spherical - however other observations have shown that this is due to the alignment of the funnel to our line of sight.

Composite images of four sun-like stars nearing the end of their lives. In these images Chandra's X-ray data is shown in blue, while green and red are optical and infrared data from the Hubble Space Telescope.

Image Credit: X-ray: NASA/CXC/RIT/J.Kastner et al.; Optical/IR: BD +30 & Hen 3: NASA/STScI/Univ. MD/J.P.Harrington; NGC 7027: NASA/STScI/Caltech/J.Westphal & W.Latter; Mz 3: NASA/STScI/Univ. Washington/B.Balick

For more information see: Chandra X-ray Observatory Press Room

8th May, 2006: It's all in a days work

For most rocky planets it is a fairly trivial task to measure the length of a day - pick a feature on the surface and watch it rotate with the planet. Measure the time it takes for the feature to rotate once around the planet and you've done it - you've measured the length of a day on that planet. Gaseous planets such as Saturn, Jupiter, Uranus and Neptune, however, are a totally different story - what do you use as a point of reference? You can't see the surface and the cloud features (if any) only tell you about the rotation of the atmosphere - this is not necessarily the same as that of the core of the gaseous planet and can vary with latitude.

One method, used by NASA's Voyager spacecraft, was to use radio and plasma wave instruments to measure radio signals. Cassini used a similar method to estimate that a day on Saturn was 10 hours, 45 minutes and 45 seconds long - this was considered to be a pretty good estimate at the time. However, even since the time of Voyager's observations, scientists have noticed large changes in the period of the radio observations - it was not possible for Saturn to speed up or slow down by the amounts that they were observing. This suggested that their measurements were not a true measure of the internal rotation rate.

A new method, used by the Cassini spacecraft, looked for magnetic features and used those as a reference for determining the length of the day as they rotated with the planet. The magnetic field around Saturn is generated deep inside its liquid metallic core by flowing electric currents and so should rotate at the same rate as the core itself. Scientists observed the rotation of the magnetic field over two years and have found it to be nearly constant at 10 hours, 47 minutes and 6 seconds with an error of plus or minus 40 seconds.

The new estimates of the Saturnian day will help scientists understand the internal structure of Saturn and will improve modelling of its weather patterns. The monitoring of the magnetic field will continue over the remainder of the Cassini mission.

An image of Saturn and its moon Enceladus (visible right of centre in the plane of the ring) as taken by NASA's Cassini spacecraft. The inability to see the surface of the planet creates difficulties in determining the length of its day.

Image Credit: NASA/JPL/Space Science Institute

For more information see: NASA News Release

1st May, 2006: ESA's XMM-Newton studies the fossil that shouldn't be

Fossil groups form when large galaxies within a galaxy group gravitationally interact with neighbouring galaxies and with the surrounding dark matter. Over time, the large galaxies spiral towards the centre of the group and merge to form a single giant galaxy known as the "fossil group". The giant galaxy sits within a group-sized halo of dark matter which can be inferred by the presence of hot X-ray emitting gas.

The formation of fossil groups is driven by "dynamical friction" whereby large galaxies lose their orbital energy to the surrounding dark matter. This process is most effective for slow moving galaxies, as is normally observed in smaller groups. In larger groups, the galaxies move more quickly and so do not lose their orbital energy as effectively. As a result, this sets an upper limit for the size and mass of a fossil group - though the exact limits are complicated by factors such as the geometry and mass distribution of the group. What is particularly surprising is that models of fossil groups as large as RX J1416.4+2315 suggest that they would not have had time to form within the age of the Universe!

RX J1416.4+2315 is dominated by a single elliptical galaxy at a distance of about 1.5 billion light years and is about 500 billion times more luminous than our Sun. Analyses of X-ray, optical and infrared data have revealed a hot gas halo 3 million light years in extent and heated to about 50 million degrees Kelvin. RX J1416.4+2315 weighs around 300 trillion solar masses, with only 2 percent in the form of stars and 15 percent in the form of hot gas. The vast majority of its mass is in the form of dark matter. Of particular interest in the recent observations is the detection of highly elongated X-ray emission.

Current models of fossil groups assume that the merging galaxies move in circular orbits around the centre of the clusters mass. However, the elongated emission observed in RX J1416.4+2315 suggests that perhaps galaxies fall towards the centre of the group in an asymmetric way, such as along a filament. This may allow the cluster to form in a shorter time-scale. More sophisticated models are currently being developed to confirm whether or not these new findings can explain how fossil groups such as RX J1416.4+2315 came into existence in such a short period of time.

The fossil galaxy cluster RX J1416.4+2315 as observed by ESA's XMM-Newton.

Image Credit: ESA

For more information see: ESA News Release

24th April, 2006: If two halves make a whole, what do two holes make?

This breakthrough in computer modelling has, for the first time, allowed scientists to simulate one of the most powerful events in the Universe - the merging of two black holes. When two black holes merge, they generate gravitational waves that propagate outwards at the speed of light causing ripples in space and time. The simulations allow scientists to "see" what the gravitational waves from such an event would look like, that is, how the waves change in frequency and strength with time throughout the merger event. The signature of this event, as seen in the simulation, can provide valuable information to gravitational wave observers.

If we could observe gravitational waves we would have a totally new way of looking at the Universe. We could study violent events such as the mergers described earlier, supernovae events and perhaps even the Big Bang - all unhindered by gas and dust. On the downside, there always seems to be a downside, these waves are incredibly difficult to detect and have so far only been detected indirectly. Instruments such as LIGO (Light Interferometry Gravitational-Wave Observatory) and the proposed LISA (Laser Interferometer Space Antenna) will work at the limits of noise and sensitivity in an attempt to detect the miniscule fluctuations caused by a gravitational waves as they travel past the Earth. The black hole merger simulations being run on the Columbia supercomputer at NASA's Ames Research Centre will give some insight into what the gravitational wave observers should expect to see. The observational results will then put the gravitational wave aspect of Einstein's general theory of relativity to the test. If the observers don't see what the simulations predicted then some fundamental revisions in our understanding of gravity will be required!

A frame from a three-dimensional simulation of two merging black holes.

Image Credit: Henze, NASA

For more information see: NASA News Release

An animation of the merger simulation is also available here (size ~7.4 Mb)

17th April, 2006: The little red rover that huffed and puffed

In orbit around Mars, the Mars Odyssey spacecraft recently celebrated its fifth year of exploring Mars by taking an image of the Solar Systems largest canyon. Meanwhile, Mars Global Surveyor is still performing beautifully and even managed to show off its capabilities by taking a snapshot of NASA's Mars Exploration Rover Spirit with a resolution of 50 cm per pixel! Also in orbit around Mars, ESA's Mars Express spacecraft continues to return stunning high resolution images of the surface. It recently took this image of Crater Gralle which has been dubbed the "Happy face" on Mars (it looks suspiciously similar to the happy face I discovered on the 6th of March in the Stephan's Quintet galaxy cluster - it might be time for me to write a conspiracy theory book on this and retire happily on the royalties) :-)

As if it wasn't already crowded enough there, NASA's Mars Reconnaissance Orbiter (MRO) successfully entered orbit around Mars and started a series of aero-braking manoeuvres to shrink its orbit. On March 24th MRO took its first high resolution image of the Martian surface (see below). It's main aim is to search for water that has persisted on the surface of Mars for a long period of time and to study the history of water on Mars. It is equipped with high resolution and wide-field imagers allowing it to not only see more in any single image but also with greater clarity. The MRO will also act as a powerful communications and navigation link for future missions to the planet.

A small part of the first image of Mars taken by NASA's MRO infrared imager.

Image Credit: NASA/JPL/University of Arizona

For more information see: NASA News Release

Having been neglected for some time now, Venus has now also received its first visitor in twelve years with ESA's Venus Express spacecraft successfully entering orbit around the planet on the 11th of April. Venus Express is jam packed with instruments that will in part be used to study the composition and temperature of the planets atmosphere, look for traces of water and oxygen molecules, observe the cloud systems at different levels within the atmosphere and monitor the surface for possible volcanic activity. Venus Express was also quick on the mark in sending back its first postcard (see below).

The first images taken of Venus by ESA's Venus Express spacecraft. The image is a false colour composite of visible and infrared images showing the day side on the left and the night side on the right.

Image Credit: ESA/INAF-IASF, Rome, Italy, and Observatoire de Paris, France

For more information see: ESA News Release

Around Saturn, Cassini continues its journey of discovery by finding a new class of moonlets that resides within Saturn's rings. These moons are only about 100 metres across but may number in the millions and may help explain the origin of Saturn's rings. Much closer to home, ESA's SMART-1 spacecraft has imaged a peculiar swirling feature known as the Reiner Gamma swirls on the surface of the moon. The data obtained from SMART-1 suggest that these unusual features may have been the result of a cometary impact under unusual conditions.

With Venus Express and MRO just warming up, and with the multitude of orbiters and probes throughout the Solar System you can be sure that we're in for some pretty exciting science over the next few years. Stay tuned for more reports to come. By the way, some of you may have noticed that things have been a bit quite on the news site for the past three weeks - I apologise for that, I was off observing during this period ... nonetheless, I have put up a few "belated" articles below to make up for my absence.

10th April, 2006: The galactic dust storm in M82

The dust particles found in the newly discovered clouds are mostly composed of a smelly material known as polycyclic aromatic hydrocarbon or PAH for short. PAH molecules are also found here on Earth in tailpipes, barbecue pits and other places where combustion reactions have occurred - so it is fitting that M82 is also known as the "Cigar galaxy" (though this nickname was based more on the galaxy's shape rather than its output). Those of you that have been reading my earlier news postings may also have remembered that these molecules were found in the cloud of material ejected by deep impact after it slammed into comet Tempel 1 last year.

M82 itself is located approximately 12 million light years away and is quite an interesting target for astronomers as it is one of the nearer starburst galaxies. It is believed that an interaction with its larger galactic neighbour M81, sometime in the past, initiated an intense burst of star formation, the greatest being in its nuclear region. The dust imaged by Spitzer is believed to be produced by stars formed during this burst and blown out by their intense stellar winds. Surprisingly, the dust seems to be all over the galaxy rather than in the cone-shaped clouds that would be typical if it had originated from the nuclear starburst region. The surprising conclusion that can be drawn from these new observations is that stars throughout the galaxy, not just in the nuclear region, are spraying the dust out - why this is so still remains to be answered.

An infrared image of M82 taken by NASA's Spitzer Space Telescope. It shows smoky dust particles being blown into space (red) by the galaxy's hot stars (blue).

Image Credit: NASA/JPL-Caltech/University of Arizona

For more information see: NASA News Release

4th April, 2006: The search for more alcohol

The new discovery was made with the UK's recently upgraded MERLIN radio telescope while observing a star formation region known as W3(OH). The observations revealed giant masing filaments of gas forming giant bridges between previously observed maser 'spots' in W3(OH) - masers are the microwave equivalent of lasers and occur naturally under special conditions. Up until this observation it was believed that masers were point-like objects or very small bright hotspots surrounded by halos of fainter emission. However, some of the maser filaments in the MERLIN observation are almost 500 billion kilometres long and so challenge previously accepted views held in astronomical maser research.

The sensitive MERLIN maser observations have allowed astronomers to observe the motion of the W3(OH) star formation region in 3-dimensions. The observations also allow astronomers to measure physical properties such as gas temperature and pressure and the strength and direction of magnetic fields. All of these properties provide important tests for star formation theories.

The process of massive star formation itself is still not very well understood because the star formation centres are normally shrouded by clouds of gas and dust. The only radiation that can escape is at radio wavelengths and so radio observations such as the ones described above are critical to gaining a better understanding of the process of massive star formation. In particular, observations of masers at other frequencies can give some insight into the types of molecular interactions that occur within these regions. More of such observations are currently planned for and it is hoped that they will provide the pieces needed to solve this puzzle.

Radio continuum emission in W3(OH) at 23.7 GHz (left) and 8.4 GHz (right). The images are superimposed with methanol maser spots (white dots), OH maser filaments (red contours) and extended methanol filaments (green contours).

Image Credit: JIVE

For more information see: RAS News Release

27th March, 2006: Jupiter from a different perspective

The image below shows an image stitched together from 36 individual images using computer software. The resulting image shows details as small as 120 kilometres across and quite clearly shows cloud features such as the Great Red Spot, reddish-brown and white bands, chaotic regions, white ovals and small vortices.

A mosaiced image of Jupiter's south pole as seen by the Cassini spacecraft on December 11th and 12th, 2000.

Image Credit: NASA/JPL/SSI

For more information see: Cassini News Release

20th March, 2006: Seeing the Universe through (very deep) rose coloured polaroids

Inflation theory was first proposed 25 years ago by Alan Guth to solve a number of problems associated with the Big Bang theory at the time - in particular the flatness problem, the horizon problem and the monopole problem. Although it did a good job at solving these problems, or at least sweeping them under the carpet, a number of competing variations of the theory quickly arose. The WMAP polarisation data has for the first time allowed scientists to test these competing models.

Previous WMAP observations focused on minute temperature variations in the CMB radiation. From this, astronomers were able to determine an accurate age of the universe and were also able to gain insights into the geometry and composition of the Universe. The latest observations not only give a more detailed map of the temperature distribution, with an accuracy of finer than a millionth of a degree, but also give the first full-sky map of the polarisation of the CMB. By resolving features in the CMB, based on polarisation, WMAP can determine how the light was changed by the environment through which it passed. This can help us compare the brightness of broad features to compact features in the CMB and this in turn gives us an understanding of what happened in the early Universe. The data has already shot down one long-held prediction that the brightness would be the same for features of all sizes. In fact, the relative brightness decreased for smaller features - a trend favouring the simplest versions of inflation theory - go, Occam, go!

The early Universe as seen by WMAP. Red indicates warmer spots, blue indicates cooler spots and the white bars show the polarization direction of the oldest light.

Image Credit: NASA/WMAP Science Team

For more information see:

13th March, 2006: Water Geysers on Enceladus

While other moons in the solar system are suspected of harbouring liquid water many kilometres below their surface, Enceladus appears to have water no more than tens of metres below its surface - why this is the case and why it is currently so active remains a mystery. Nonetheless, the discovery of the geyser does explain the presence of oxygen atoms which seem to fill the Saturnian system. It is believed that water molecules spewed out by the geyser break down into their main constituents and in the process provide a constant supply of oxygen to the system.

Most intriguingly, the presence of liquid water may also provide conditions suitable for living organisms to survive. This makes Enceladus, along with Titan, a high priority target for exploration. Cassini will take another close look at the moon early 2008 when it approaches within 350 km of the moon.

A monochrome and enhanced colour-coded image taken by the Cassini spacecraft. The image reveals a plume of icy material extended above the southern polar region of Saturn's moon Enceladus

Image Credit: NASA/JPL/Space Science Institute

For more information see: JPL News Release, a NASA movie is also available here (~ 13 Mb).

6th March, 2006: A Shocking Quintet

As the name suggests, Stephan's Quintet is composed of five galaxies - they appear as bright yellow-pink knots inside a blue halo of stars in the image below. Four of the five galaxies are involved in a violent collision which has left their interiors almost totally stripped of hydrogen gas. The collision of one of these galaxies, NGC 7318b, with the gas spread throughout the cluster heats hydrogen in the shock wave to produce the green glow observed in the image (NGC 7318b is the left of two small bright regions in the middle right of the image).

A composite image showing the Stephan's Quintet galaxy cluster. The image is composed of near-infrared (blue) and H-alpha (green) images from ground-based optical telescopes in Spain and 8-micron infrared data from NASA's Spitzer Space Telescope (red).

Image Credit: NASA/JPL-Caltech/Max-Planck Institute/P. Appleton (SSC/Caltech)

Spectral data obtained with the Spitzer Space Telescope has shown that the gas in the shock wave is extremely turbulent, causing atomic hydrogen to pair-up and form molecular hydrogen in the wake of the shock wave. Unlike atomic hydrogen, the molecular form gives off most of its energy through vibrations that emit in the infrared. While the degree of turbulence was particularly surprising to astronomers, even more so was the strength of the emission - why the emission is so strong is still a mystery.

For more information see: Spitzer Space Telescope Newsroom

Side Note: Personally, I believe something even more sinister is going on here and whoever is responsible has left a cheeky mark there as evidence:

27th February, 2006: Welcome to SAO Teaching Period 2, 2006

Welcome to SAO Teaching Period 2, 2006!

Welcome to another fun-packed semester of SAO! As with most recent semesters I have begun with a review of news that you might have missed during the break. This semester is no exception and I will bring you all the new news highlights with new types of stars, new types of explosions, new planets, new moons, new missions and other new discoveries - but I guess you already knew that?

Let's begin close at home with the discovery of three new moons around Pluto. The moons were first discovered by the Hubble Space Telescope (HST) back in May of last year and recent HST images have confirmed their existence (see image below). This is sure to add even more confusion to the "Is Pluto Really a Planet?" debate.

The Hubble Space Telescope helps to discover three new moons for Pluto.

Image Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team

The Parkes radio telescope (A.K.A. "The Dish") has helped to discover a new type of star, or more accurately a type of pulsar, and even more accurately a Rotating Radio Transient or RRAT. Normally pulsars emit periodic trains of radio pulses many times per second, however, these new sources emit flashes that last for 2-30 milliseconds and then remain silent for times ranging between 4 minutes and several hours.

NASA's Swift satellite has also made a recent discovery of a new type of cosmic explosion. The explosion appears very similar to a gamma-ray burst but is about 100 times closer and lasts about 100 times longer. Most gamma-ray bursts last between a few milliseconds to a few tens of seconds - this new explosion lasted for about half an hour! It is believed that this burst may be the precursor of a supernova event and so astronomers are eagerly monitoring this source to see what happens next.

The exoplanet search continues unabated with Spitzer discovering a hot extrasolar planet orbiting a star only 63 light-years from Earth. Spitzer has also discovered potential solar systems surrounding two massive stars. The discovery is a surprise because stars as big as these generate intense solar winds that should sweep away material in the disk before planets would have a chance to form. These stars' disks are bloated and spread more than 60 times further than Pluto's orbit around the Sun. This Kuiper-like belt may contain 10 times more material than our own Kuiper belt and provide sufficient material to form an icy planet. The VLA has also been used to uncover a bizarre planetary system about 500 light-years away in which the inner planets are going in one direction and the outer planets are going in the opposite direction. The discovery hints that the process of forming planets from planetary disks is much more complex than previously thought. An icy exoplanet has been discovered around a red dwarf using microlensing techniques, life's building blocks have been discovered in a planet forming disk, cometary dust has been detected around a white dwarf and Kuiper-like belts have been detected around two nearby stars. It's all happening!

The past few months have also seen the launch of a number of missions throughout the solar system. Mars Reconnaissance Orbiter was successfully launched August 12th last year and is now approaching the most critical period when it must initiate a 27 minute firing of its engines on March 10 in order to enter orbit around Mars. On November 9th last year Venus Express was successfully launched to visit our other neighbour Venus and on January 19th the New Horizons probe was launched to send the first probe to Pluto. Meanwhile, the Stardust probe successfully returned to Earth on January 15th with a valuable payload of comet dust that is being analysed as I type.

Meanwhile, Cassini continues to return stunning images of Saturn and its moons. Whilst on Mars Opportunity and Spirit continue to scour the Martian landscape looking for interesting geology, meteorology and astronomical phenomena. Also around Mars, the MARSIS instrument of ESA's Mars Express, has begun to return information about features under the Martian surface. The Japanese "underdog" probe Hayabusa however faced a series of unfortunate failures and it appears that even if it did eventually retrieve samples from the asteroid Itokawa it might not be able to return back to Earth until 2010 - if at all. Nonetheless, there are plenty of probes and instruments to keep us thrilled over the next few months, so stay tuned!