Posted on by Fraser Cain

Investigation Into One of Mars Express’ Instruments

Artist’s impression of Mars Express. Image credit: ESA Click to enlarge
ESA has started a technical investigation into the Planetary Fourier Spectrometer (PFS) on board Mars Express, after a problem developed in the instrument a few months ago.

Vibration effects (induced by spacecraft activities) have been suggested as a cause for the observed behaviour. However no source has yet been identified and other causes internal to the instrument cannot be fully ruled out.
In order to establish the exact cause of the problem, ESA?s Mars Express team is setting up an investigations board involving experts from the Mission Science Working Team, ESA, industry and the Italian Space Agency (ASI).

This could lead to resuming scientific observations using modified procedures but, until all existing data and a number of additional measurements currently being planned have been examined, it is too early to draw a conclusion on the operational status of the PFS instrument.

The PFS instrument has performed without any such problems for almost two years, following the launch of Mars Express in June 2003. In this period, the instrument has provided much new information on the global composition and movement of the Martian atmosphere.

Even if it is found that PFS is no longer fully functional, it is only one element in the scientific package on board Mars Express. The other six instruments (HRSC, OMEGA, ASPERA, SPICAM, MARSIS, MaRS) are all currently working well and are providing new insights into the Red Planet and its evolution. These remaining instruments will continue the scientific success of the Mars Express mission.

Original Source: ESA Portal

Posted on by Fraser Cain

Giant Jet Streams

Jupiter. Image credit: NASA/JPL Click to enlarge
Turbulence driven by sunlight and thunderstorm activity may explain the multiple east-west jet streams on Jupiter and Saturn and even produce strong winds extending hundreds or thousands of kilometers into the interior, far below the altitudes where the jets are driven.

Scientists have been trying to understand the mechanisms that form the jet streams and control their structure since the first high-resolution images of Jupiter were returned by the Pioneer and Voyager spacecraft in the 1970s.

On Earth, the jet streams — narrow currents of air flowing from west to east in the midlatitudes — form a major component of our planet’s global circulation, and they control much of the large-scale weather experienced by the United States and other countries outside of the tropics. Similar east-west jet streams dominate the circulation of the giant planets Jupiter, Saturn, Uranus, and Neptune, reaching up to 400 miles per hour on Jupiter and nearly 900 miles per hour on Saturn and Neptune. The question of what causes these jet streams and how deep they extend into the interior of the giant planets remain some of the most important unsolved problems in the study of planetary atmospheres.

Adam Showman and Yuan Lian of The University of Arizona in Tucson and Peter Gierasch of Cornell University in Ithaca, New York, explained how cloud-layer turbulence can drive deep jets at the 37th annual meeting of the Division of Planetary Sciences of the American Astronomical Society, held in Cambridge, England.

Lian, Showman, and Gierasch performed computer simulations showing that horizontal temperature contrasts — generated by sunlight or differences in thunderstorm activity — can produce multiple jet streams that penetrate deep into the interior of a giant planet. In the simulations, the temperature contrasts induce deep-penetrating circulation cells that in turn drive the deep jets. The study, which uses an advanced three-dimensional computer model, is among the first that allows an assessment of how jets formed near the top of the atmosphere interact with the interior.

Most planetary scientists have assumed that jets pumped near the top of the atmosphere will remain confined to those shallow layers, and we’ve shown that this is not a valid assumption,” Showman said.

NASA’s Galileo Probe, which parachuted through Jupiter’s atmosphere in 1995, was intended in part to help answer the question of how deep the jet streams extend. The probe found strong winds extending at least 150 kilometers (almost 100 miles) below the clouds. Planetary scientists have widely interpreted this measurement as evidence that the jets are driven from deep inside Jupiter’s interior. The new study challenges this interpretation.

“We still don’t know whether the jets on the giant planets are driven from the top or within the deep interior,” Showman said. “But our study shows that the deep winds measured by the Galileo probe could just as easily result from shallow cloud-layer turbulence as from turbulence deep inside Jupiter’s interior.”

“This result contradicts a long-standing assumption on the part of many planetary scientists.”

The new study also shows that, under realistic conditions, the turbulence can produce not only numerous jet streams but a strong eastward flow at the equator, as observed on Jupiter and Saturn. Such flows are notoriously difficult to produce in atmospheric models, Showman noted.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

The Risk of a Comet Strike is Low

Comet. Image credit: NASA/JPL Click to enlarge
The chances of the Earth being hit by a comet from beyond Pluto ? ? la Deep Impact ? are much lower than previously thought, according to new research by an ANU astronomer.

Using computer simulations and data from an American military telescope, Dr Paul Francis, from the ANU Research School of Astronomy and Astrophysics at Mt Stromlo, has found there are seven times fewer comets in our solar system than previously thought.

?I calculate that small comets, capable of destroying a city, only hit the Earth once every 40 million years or so,? Dr Francis said. ?Big continent-busting comets, as shown in the movie Deep Impact, are rarer still, only hitting once every 150 million years or so. So I don?t lose sleep over it, but you?re still more likely to be killed by a comet than to win the Lotto jackpot.?

Previous estimates of the number of comets were based on the work of amateur astronomers, who for hundreds of years have been scanning the skies, looking for new comets.

Previously, it was believed that these amateur astronomers were only spotting three per cent of the comets passing close to the Earth: the rest were thought to be missed because they were in the wrong part of the sky or were too faint.

But Dr Francis found that the amateurs were doing better than anyone had realised ? they were actually spotting 20 per cent of comets. There are therefore far fewer undiscovered comets.

?The new data allowed us to count the number of faint and far-away comets that the amateurs had missed. And we found that they were pretty rare,? Dr Francis said.

These results apply to comets coming from beyond the orbit of Pluto, which is where most comets live. The Earth is still at risk of being hit by asteroids, and by so-called short-period comets ? ones that come past repeatedly, like Halley?s comet.

?But asteroids and short-period comets come past again and again, so if we?re clever enough we can find them all and predict which, if any, will hit the Earth,? said Dr Francis. ?If we find one on a collision course with the Earth, we would normally have hundreds of years warning in which to do something about it, like deflecting the asteroid.

?The comets coming from beyond Pluto, so called long-period comets, are nastier, as they are totally unpredictable, and if we see one on a collision course we?d have at best one or two years warning ? not long enough to do anything.?

Dr Francis? research has been accepted for publication in the Astrophysical Journal. It was based on computer simulations, published data from the Lincoln Near Earth Asteroid Research Project at White Sands Missile Range in New Mexico, and on data from amateur astronomers around the world.

Original Source: ANU News Release

Posted on by Fraser Cain

Hubble’s View of the Boomerang Nebula

Boomerang Nebula. Image credit: STScI/AURA Click to enlarge
The Hubble Space Telescope has “caught” the Boomerang Nebula in these new images taken with the Advanced Camera for Surveys. This reflecting cloud of dust and gas has two nearly symmetric lobes (or cones) of matter that are being ejected from a central star. Over the last 1,500 years, nearly one and a half times the mass of our Sun has been lost by the central star of the Boomerang Nebula in an ejection process known as a bipolar outflow. The nebula’s name is derived from its symmetric structure as seen from ground-based telescopes. Hubble’s sharp view is able to resolve patterns and ripples in the nebula very close to the central star that are not visible from the ground.

Astronomers are uncertain of the cause of bipolar outflow in this, and many other, young nebulae like the Boomerang. It may be that a disk of slow-moving material is situated around the equator of the star, thereby blocking more rapidly moving ejected material there, and allowing only matter closer to the poles to be ejected. Another consideration may be that magnetic fields are responsible for constraining the material and thus causing the double-lobed shape of the nebula.

Bipolar outflows are seen to occur both from very young stars (“protostars”) that are still in the process of collapsing and forming, and from old stars nearing the ends of their lives that have become bloated red giants. The Boomerang is believed to be the ejected outer layers from an old red giant. Each lobe of the Boomerang Nebula is nearly one light-year in length, making the total length of the nebula half as long as the distance from our Sun to our nearest neighbors- the Alpha Centauri stellar system, located roughly 4 light-years away.

These images of the Boomerang were taken in early 2005 with the Advanced Camera for Surveys onboard Hubble. A visible light filter was used in combination with a series of polarization filters. Similar to polarizing sunglasses that are used to reduce the amount of scattered light that enters our eyes on a sunny day, the telescope’s polarizing filters allow only light of a specific polarization angle to pass through to the camera’s detector. By combining images taken at different polarization angles, astronomers can study light scattering in the nebula and the properties of the small dust particles responsible for the scattering. Colors were assigned to represent different polarization components, and then those colors were adjusted to accentuate features in the nebula, resulting in the multi-hued composite image.

The Boomerang Nebula is located about 5,000 light-years from Earth in the direction of the Southern constellation Centaurus. Submillimeter radio measurements made in 1995 show the deep interior of the nebula to have a temperature of only one degree Kelvin above absolute zero, with absolute zero equal to nearly -460 degrees Fahrenheit. This makes the inner regions of the Boomerang Nebula one of the coldest known places in the universe.

Original Source: Hubble News Release

Posted on by Fraser Cain

Solar Storms Can Shift Dangerous Areas in Space

Astronaut on the Moon surface. Image credit: NASA Click to enlarge
A breakthrough by a team of British, US and French scientists will help protect astronauts, spacecraft and satellites from radiation hazards experienced in space.

Reporting in the journal Nature this week, the team describe how their study of rare and unusual space storms provided a unique opportunity to test conflicting theories about the behaviour of high energy particles in the Van Allen radiation belts* – a volatile region 12000 miles (19,000 km) above the Earth.

Lead author, Dr Richard Horne of the British Antarctic Survey (BAS) says

?Solar storms can increase radiation in the Van Allen belts to levels that pose a threat to spacecraft. As modern society relies increasingly on satellites for business, communications, and security, it is important to understand the environment that spacecraft operate in so that we can help protect our space investment.

?For a long time scientists have been trying to explain why the number of charged particles inside the belts vary so much. Our major breakthrough came when we observed two rare space storms that occurred almost back-to-back in October and November 2003. During the storms part of the Van Allen radiation belt was drained of electrons and then reformed much closer to the Earth in a region usually thought to be relatively safe for satellites.

? When the radiation belts reformed they did not increase according to a long-held theory of particle acceleration. Instead, by using scientific instruments in Antarctica and on the CLUSTER mission satellites, we showed that very low frequency radio waves caused the particle acceleration and intensified the belts.

?This new information will help spacecraft operators and space weather forecasters who must predict when satellites and missions are most at risk from radiation events allowing them to take measures to protect instruments and systems from damage, and astronauts from risks to their health.?

Original Source: BAS News Release

Posted on by Fraser Cain

Progress 19 Brings Spare Parts to the Station

A Progress supply ship. Image credit: NASA Click to enlarge
An unpiloted Russian Progress cargo ship docked to the aft port of the International Space Station (ISS) Zvezda module today at 10:42 a.m. EDT, as the Station flew 220 miles above Central Asia near northern Kazakhstan. The 19th Progress spacecraft to visit the ISS is carrying more than 5,000 pounds of supplies for the crew.

Expedition 11 Commander Sergei Krikalev and Flight Engineer John Phillips will check for leaks before opening the hatch to the Progress later today. They’ll begin unloading the cargo tomorrow.

The supplies include food, fuel, oxygen and air, clothing, experiment hardware, Russian spacesuit components and spare parts for the Vozdukh carbon dioxide removal system. A new water circulation liquids unit is onboard the supply ship. This unit is for the station’s Elektron oxygen-generating system which is inoperable. The unit will be installed next week to try to bring Elektron back into service.

The remainder of the Progress payload includes 1,763 pounds of propellant for the Russian thrusters; 242 pounds of oxygen and air in tanks as a backup supply for the oxygen generated by Elektron; and 463 pounds of water to augment the supplies left by the Space Shuttle Discovery during the STS-114 mission.

Some of the clothing and personal effects delivered to the station include items for the next resident crew, Expedition 12 Commander Bill McArthur and Flight Engineer Valery Tokarev. They are scheduled to launch from the Baikonur Cosmodrome in Kazakhstan Oct. 1 in the Soyuz TMA-7 capsule.

Information about the crew’s activities on board the station, future launch dates, and sighting opportunities is available on the Web at: http://www.nasa.gov/station

Original Source: NASA News Release

Posted on by Fraser Cain

Podcast: The Fate of the Universe

How will the Universe end? Right now cosmologists have two equally distressing scenarios mapped out for the long term fate of the Universe. On the one hand, gravity might slow down the expansion of our Universe so that it coasts to a stop and possibly even collapses back down into a Big Crunch. On the other hand, the expansion of the Universe could continue indefinitely thanks to the acceleration of dark energy. We would face a cold, lonely future as other galaxies fade away into the distance. My guest today is Eric Linder from the Lawrence Berkeley National Laboratory and he’s proposing experiments that could help us learn which of these two fates await us.
Continue reading “Podcast: The Fate of the Universe”

Posted on by Fraser Cain

What’s Up This Week – September 12 – September 18, 2005

The Moon, captured by Apollo 11 astronauts. Image credit: NASA. Click to enlarge.
Monday, September 12 – If you’re up before sunrise this morning, be sure to step outside with a pair of binoculars and check out how close Saturn is to the M44. You should be able to see them both in the same field of view!

Today in 1959, the USSR’s Luna 2 scored a mark as it became the first manmade object to hit the moon. The successful mission landed in the Paulus Putredinus area, and tonight we’ll go there.

The most outstanding feature will be mid-placed Copernicus. Head northeast for Eratosthenes caught on the “tail” of the Apennine Mountains. To the northeast you will see prominent crater Archimedes with smaller craters Aristillus and Autolycus to the east. South of this pair, and caught along the mountain range, you will spy a dark grey, heart-shaped area known as the “Rotten Swamp” – Paulus Putredinus. Apollo 15 landed near Mons Hadley on its northeastern shore, but Luna 2 beat it there. Look at the area between the southern Autolycus and Archimedes. Spaseba!

Before we call it a night, why not point your scope toward the star in the northeast corner of the diamond of Delphinus? Its name is Gamma and it is one of the best double stars in this area for a small optics. Discovered by Struve in 1880, this 100 light year distant pair will show a slight yellow tinge in the fourth magnitude primary, and perhaps a little green in the fifth magnitude secondary. Enjoy it tonight…

Tuesday, September 13 – Today in 1922, the highest air temperature ever recorded at the surface of the Earth occurred. The measurement was taken in Libya burned in at a blistering 136?F, but did you know that the temperatures in the sunlight on the Moon double that? Tonight let’s take a look at a sunlit feature as we head for the bright point of crater Euler.

Beginning towards the north in the mostly disclosed Mare Ibrium region, look for this small, but conspicuous crater near the terminator. Note that it is roughly the same size as its two attendant craters to the east – Lambert and Pytheas, but has a noticeably central peak. If timing is right, you may be able to see the peak of Mons Vinogradov peeking above the terminator to its west.

For viewers in New Zealand, you will have the opportunity to watch the Moon occult Tau Sagittarius on this universal date. Please check this IOTA webpage for details.

If that’s not “hot” enough for you, then take a look straight overhead at brilliant star Vega. It is a “Sirian type” star and with a surface temperature of about 9200 degrees Kelvin, it’s twice as hot as our own Sun. At around 27 light years away, our entire solar system is moving towards Vega at a speed of 12 miles per second, but don’t worry… It will takes us another 450,000 years to get there. If we were to arrive tonight, we’d find that Vega is around 3 times larger than Sol and that it also has a 10th magnitude companion that can often be resolved in mid-sized scopes. It’s one of the first stars to ever be photographed. Back in 1850, that simple star – Vega – took and exposure time of 100 seconds through a 15″ scope. How times have changed!

Wednesday, September 14 – If you have a clear western horizon, take the time after the Sun sets to look at how far the evening planets have now moved apart. With Venus still blazing, Jupiter is becoming harder and harder to spot as it has moved a handspan away to the west. It’s almost gone…

Before we head off into the night, let’s take a look at the lunar surface. While outstanding Gassendi will catch the eye, there are more craters along the shores of Mare Humorum that deserve some attention! South of Gassendi and along the west shore is Class III crater Mersenius. Perhaps the terminator will be dividing it at the time of your viewing at it will appear like a “bite” taken out of the edge. Perhaps it will be well lit and you will see a cruciform structure of mountains and craters. Tonight its features look quite high, but by tomorrow, it will be totally washed out.
Due south of Gassendi across Mare Humorum is Doppelmeyer, who’s eroded walls have left it nothing more than a ghost of its former self – yet you can still see an upsweep in its interior landscape. If skies are stable, power up and see if you can spot Rimae Doppelmeyer to the west or the faded ruins of Puiseux on its eastern flank.

Thursday, September 15 – Head’s up, Eastern Europe! Tonight you have a chance to watch the Moon occult Epsilon Capricornii. Please check this IOTA webpage for details in your area.

Tonight on the lunar surface, we’ll visit the far north as well look towards our guidepost, Sinus Iridum. Head north once again to spot the rather unusual rectangle shape of crater Babbage. This ancient, shallow enclosure has many younger craters within it, and Babbage A will be quite clear. Heading northeast about twice the length of Babbage, you will spot a rather deformed “heart shape” that marks crater Anaximander. This will be part of a group of five overlapping craters, and the name is given essentially to the whole complex. Look for younger crater Carpenter as a black ellipse with a bright border intruding in its walls.

While you’re out, stop to look up at Beta and Gamma Lyrae, the lower two stars in the “Harp”. Beta is actually a quick changing variable which drops to less than half the brightness of Gamma in around 12 days. For a few days the pair will seem of almost equal brightness and then you will notice the star closest to Vega fades away. Beta is one of the most unusual spectroscopic stars in the sky, and it is possible that its eclipsing binary companion may be the prototype of the “collapsar”, (yep. a “black hole”!) rather than a true luminous body.

Friday, September 16 -The Moon rises shortly before Sun sets tonight amidst the difficult to see stars of the constellation Aquarius. Believe it or not, Uranus is only about 3 degrees away, but it will be next to impossible to pick the distant planet out with the lunar glare. So why ignore the Moon? Let’s do some exploring and we can start just as easily as identifying the grey oval of Grimaldi.

Just north of Grimaldi is Class V Hevelius. It will show as a bright oval, similar to Grimaldi, but will contain an off-center mountain peak. Its north wall is broken by Class I Calaverius, a narrow, bright ellipse with a thin, black border to the east. Only 100 kilometers away from here on the edge of Oceanus Procellarum lay the remains of the very first successful lunar landing. It was here on February 3, 1966 that the Soviet probe – Luna 9 – touched down. The man-sized craft sent back panoramic television images to a waiting Earth, revealing the uneven, jagged surface covered with dust. So good were the probe’s images, that scientists were even able to discern small depressions and protrusions only millimeters in size.

Saturday, September 17 – On this day in 1789, Sir William Herschel discovered Saturn’s moon Mimas. And indeed the Moon will be on our mind as tonight is “Harvest Moon”.

At exactly 10:01 p.m. EDT, the Moon will become Full and it will be the closest to the Autumnal Equinox. Because the orbit is more horizontal with the eastern horizon, it will rise a dusk for the next several nights in a row. On the average, the Moon rises about 50 minutes later each night, but at this time of year it’s around 20 minutes later for mid-northern latitudes and even faster farther north. Because of this added extra light, the name “Harvest Moon” came about because it allowed farmers more time to work in the fields.

Often times we perceive the “Harvest Moon” as being more orange than any other time of the year. The reason is not only scientific enough – but true. Coloration is caused by the scattering of the light by particles in our atmosphere. When the Moon is low, like now, we get more of that scattering effect and it truly does appear more orange. The very act of harvesting itself produces more dust and often times that coloration will last the whole night through. And we all know the size is only an “illusion”…

So, instead of cursing the Moon for hiding the deep sky gems tonight, enjoy it for what it is… A wonderful natural phenomena that doesn’t even require a telescope! Is that Mars following behind it?

Sunday, September 18 – If you’re up before dawn this morning, why not take the opportunity to step outside and look at how much the sky has changed. The winter constellation of Orion has now well risen and the harbinger of the Winter – Sirius – has now appeared.

Once again, the Moon will play a major role in tonight’s sky, but why not take the time to enjoy some of its incredible features? With just your eye you can identify Mare Crisium to the northeast, and Mare Fecundatitus to the southeast. Mare Frigorus is the long, dark stretch that runs across the northern section and the expanse of Mare Ibrium and Oceanus Procellarum dominate the northwest quadrant. Can you spot the dark oval of Mare Humorum to the southwest or Nubium to its east?

Those of you with sharp eyes might be able to make out the small dark oval of crater Plato to the north or Grimaldi to the west. Can you see the bright point of Tycho? Just north of central is the very round, grey Mare Serenitatis and south of it, Mare Tranquillitatis. Using binoculars, trace out the bright rays of Proculus in the east and Tycho to the south. Aristarchus and Kepler shine like beacons in the northwest and while the southwest is far more muted, look for the bright point of Euclides.

Hang tough. A few more days and darker skies will be on our side! Until then? May all your journeys be at light speed…. ~Tammy Plotner

Posted on by Fraser Cain

Join the Bad Astronomy/Universe Today BOINC Team

Several years ago, scientists at University of California, Berkeley came across a situation in which more data was being gathered by a radio telescope than could be analyzed by any single computer. The solution to this problem was to use the idle time of personal computers all around the world. This resulted in the creation of SETI@Home, a downloadable application that would do some calculations on a very small piece of the gathered data. The results would then be returned to SETI@Home’s servers to be combined back with results from other computers all around the world. This later branched into BOINC, a project that allows one to choose from multiple projects such as SETI@Home and run many projects on one computer. The user can even allot how much time is spent on each project. BOINC runs at a low priority on one’s computer, which means when other programs (Word, Internet Explorer, etc.) request the processor, BOINC hands it over and allows the program to do as it wishes. When the program is done, BOINC picks up where it left off.

The Bad Astronomy/Universe Today forum currently has a team for four of the BOINC projects. The team is named BABB, but that will soon change when the BAUT forum name is finalized. The name will change to reflect the BAUT name. Though the team is named after the forum, those who are not a part of the forum are welcome to join.

The Einstein@Home project searches for spinning neutron stars known as pulsars by searching for gravity waves in data from the LIGO and GEO gravitational wave detectors. Anyone wishing to sign up for Einstein@Home can do so here and can sign up for the Bad Astronomy/Universe Today team by clicking join here.

The LHC@Home project allows for the simulation of a particle travelling through a large particle accelerator that is due to be completed by 2007 by CERN known as the LHC (Large Hadron Collider). Anyone wishing to sign up for Einstein@Home can do so here and can sign up for the Bad Astronomy/Universe Today team by clicking join here.

The SETI@Home project searches for evidence of extraterrestrial intelligence through radio waves received from the Arecibo Observatory. Anyone wishing to sign up for SETI@Home can do so here and can sign up for the Bad Astronomy/Universe Today team by clicking join here.

The orbit@home project will take data from observations of asteroids and calculate their orbits. This will assist in the search for any asteroids in an eventual collision course with the Earth, as well as catalogue the orbits of the asteroids. This project is not running yet, but soon will be in the test phase. Member creation is shutdown for the time being. The project will have to be tested for a while before it goes online.

The team has a web page and member stats. Any questions regarding this project can be asked at this thread on the BAUT forum or sent to [email protected].

Posted on by Mark Mortimer

Book Review: Voyages to the Stars and Galaxies

Texts on general courses need to fulfill two goals; they must explain the details, and they must capture the imagination. Those contemplating sticking their toe into the pool of astronomy could understandably get nervous. This field has contributions made from most of the greatest thinkers of our species. In addition, our primitive five senses are woefully inadequate to peel back the shrouds of astronomical mystery. Today, professionals tell tales of trying to contact aliens, go through a spacetime continuum, or detect dark energy. They rely on state-of-the-art technology using ultimate processing power and quirky algorithms to make sense of what the uninitiated would consider random patterns. Yet, in starting from the beginning and keeping the information succinct, an introductory text can supply adequate elucidation and perhaps entice another neophyte to continue past the general level.

The team of Fraknoi, Morrison and Wolff, in their textbook, meet both these goals. For astronomy, they offer completeness. To start, there’s the perspective of astrology based solidly in history. Then they proceed down the chronological path bringing in each contributor and the significant contributions. Orbits, geocentricity, eclipses and tides lay the ground work. However, the text quickly proceeds to the electromagnetic spectrum, radio telescopes, nuclear chemistry and the basis of today’s observation, that is, star types, distances and life attributes. The end brings the reader to current perceptions on relativity, cosmology, and astrobiology. There is no doubt that the authors explain the details, though for the most part they focus on data rather than on rationale.

Trying to capture an imagination without knowing the person is much more nebulous a task. Clearly, the authors assume the reader has no technical background. The powers of ten mathematics notation is the most complex math and has two solid descriptions, one in the text and the other in the appendices. Photographs, diagrams, historical vignettes and charts ease the way forward for those not used to contemplating quantitative descriptions. Analogies appear throughout. For example, did you know the density of a neutron star is similar to squeezing all the people on Earth into the volume of a single rain drop? Lastly, the accompanying CD, with the student edition of The Sky, gives many opportunities to take the data in the text and compare it to night time observations for any latitude or longitude within a time of 10 000 years. If the student truly has interest in astronomy, then this text should capture their imagination, at least until the end of the course.

As a text, this book aims solidly for course work. Each significant subject of astronomy has its own chapter. The chapter layout starts with the history, emphasizing the practitioners, next the current activity emphasizing the equipment, and then ends with expectations emphasizing the research thrusts. At the conclusion of each chapter, a summary, list of group activities, review questions and contemplative questions provide lots of study material. In a unique step, the authors have set up an adoption program whereby they keep all registered users up to date on new material. They also have a help hot line (actually email line) where they promise to quickly answer any (student or lecturer) question regarding this course work.

Given that this version is the third edition, it should and does flow smoothly. Chapters stand on their own. Different styles emerge, likely due to the different authors, but no problems result. The information is current, though it can be necessarily vague, such as the topic on our universe’s size. Also, like most texts, the contents revolves around data and is perfect for digesting and regurgitation. The sparse amount of theory is appropriate for a general introductory text.

September is the time for school and the show of Sagittarius in the night sky. School has surprises but so does Sagittarius. Did you know that within the boundaries of this constellation there lies a galaxy that’s about to get eaten up by our own Milky Way? Read the book Voyages to the Stars and Galaxies by Andrew Fraknoi, David Morrison, and SidneyWolff to learn about the constellations, stars and their marvellously unique and sometimes hungry properties. Anthropic or not, you’ll see that we’re in one amazing universe.

Review by Mark Mortimer

Read more reviews online, or purchase a copy from Amazon.com.