Macc Astroheader

“From chaos, Lord, I came alive, My thirst to chaos goes And, of repose once born, I strive To go back to repose!” Hyperion, you out of chasm Arise with worlds of grace! Ask not for wonder or phantasm That has no name or face…”
Mihai Eminescu From the poem “Luceafarul”

What lies at the bottom of Hyperion’s strange craters? Nobody knows. To help find out, the robot Cassini spacecraft now orbiting Saturn swooped past the sponge-textured moon again and took an image of unprecedented detail. That image, shown above, shows a remarkable world strewn with strange craters and a generally odd surface. The slight differences in colour possibly show differences in surface composition. At the bottom of most craters lies some type of unknown dark material. Inspection of the image shows bright features indicating that the dark material might be only tens of metres thick in some places. Hyperion is about 250 kilometres across, rotates chaotically, and has a density so low that it might house a vast system of caverns inside.
Cassini Imaging Team, SSI, JPL, ESA, NASA.

When is a moon not a moon?

Earth has a second moon, of sorts, and could have many others, according to three astronomers who did calculations to describe orbital motions at gravitational points in space, that temporarily pull asteroids into bizarre orbits near our planet. The 3-mile-wide (5-km) satellite, which takes 770 years to complete a horseshoe-shaped orbit around Earth, is called Cruithne and will remain in a suspended state around Earth for at least 5,000 years.

The finding is based on work by 18th century French mathematician Joseph-Louis Lagrange, whose name is given to the five points of equilibrium that occur between the gravitational forces of planets and the sun. (As illustrated in the last edition of “What’s Up”).

Cruithne approaches the Earth, and when it gets close enough, it turns around and retreats, only to repeat its performance on the other side. This unusual arrangement, in which close encounters with a planet do not result in impacts or strong distortion of the asteroids orbit is termed a ‘horseshoe’ orbit because of its shape. The asteroid doesn’t really go around the Earth, but rather shares the Earth’s orbit with it. (Another way to think of this horseshoe is to consider a three-lane, circular race track. The Earth is a large truck moving at a constant speed down the centre lane and the asteroid is a car. When in the outer lane, the car is going a bit slower than the truck, and the truck starts to catch up. But just when the truck is about to pass, the car switches to the inner lane and speeds up. It then starts to pull away from the truck, but because the track is circular, the car will eventually catch up with the truck from behind. When it gets close, the car again switches to the outer lane and slows down. Then the whole cycle repeats. This is what is happening in a simple horseshoe. Both vehicles share the same highway, but in a co-ordinated fashion so as to avoid collision. In reality, the delicate co-ordination of the asteroid and the Earth is performed by the laws of celestial mechanics, and requires just the right conditions.)

Cruithne was first discovered in 1986, but scientists working at Queen Mary and Westfield College in London were intrigued enough with its wanderings to develop mathematical models to describe its path. That led them to suggest that ‘co-orbital dynamics’ could explain the movement of other objects captured at the Lagrangian points. “We found new dynamical channels through which free asteroids become temporarily moons of Earth and stay there from a few thousand years to several tens of thousands of years. Eventually these same channels provide the moons with escape routes. So the main difference between the moon (we’ve always known) and the new moons is that the latter are temporary --they come and go, but they stay for a very long time before they leave.” said Fathi Namouni, one of the researchers, now at Princeton University.

Astronomers have become very aware of the large numbers of asteroids that inhabit the solar system. Most orbit the sun in a belt between Mars and Jupiter, but a handful cross Earth’s orbit.

Cruithne takes 770 years to complete its horseshoe orbit. Every 385 years, it comes to its closest point to Earth, some 9.3 million miles (15 million kilometres) away. Its next close approach to Earth comes in 2285. Cruithne’s orbit is exceedingly strange. “With respect to the Earth it moves very slowly,” said Namouni’s colleague Apostolos Christou. “At specific points in its orbit, it reverses its rate of motion with respect to Earth so it will appear to go back and forth.”

What is a moon?

Namouni and his colleagues believe that co-orbital motions probably describe the orbits of many objects at the Lagrange points, but are these objects moons? A moon is usually defined as an object whose orbit encompasses a planet rather than the sun.

In the view of Carl Murray, who worked with Namouni and Christou on the research, there are three classes of moons -large moons in near-circular orbits around a planet, that formed soon after the planet; smaller fragments that are the products of collisions; and outer, irregular moons in odd orbits, or captured asteroids like Cruithne. In the past year, astronomers have reported finding such objects around Uranus.

So where does our ‘real’ moon fit into this classification, given that scientists think it is the result of a Mars-sized object slamming against our planet soon after it formed? Murray speculates that our own moon is in many ways unique and its formation seems like a one-off event.

There are almost certainly more temporary moons of Earth and other planets, waiting to be discovered. As scientists get better at discovering asteroids, they will find more that have orbits that will keep them close to Earth for a long period of time. But some of those objects are very small. We are beginning to redefine our understanding both of ‘planets’ and ‘moons’.

Namouni does not think of Cruithne as a real ‘moon’ because it moves around the Earth at this time but may not forever. Earth is causing Cruithnes present trajectory, but it could eventually escape.

So its not a true moon of Earth, but it might become one. The researchers found that Cruithne is likely to use the new dynamical channels to become a real moon of the Earth and remain so for 3,000 years. Their finding throws into question the current official counts of moons around the planets, since there may be dozens of unknown asteroids circling each planet in temporary or permanent orbits due to gravitational balance points.

For now, Namouni believes there should be a new category of moons -temporary moons that are captured for a few thousand to several tens of thousands of years.

Dave Ogden
(Compiled from several www sources)

Stephen Baxter

The strange asteroid Cruithne, described above, figures largely in a novel written by one of our forthcoming speakers. The novel, “Time” by Stephen Baxter, relates a mysterious series of events in which the asteroid is of primary importance. Stephen will be speaking to us in the new year.

Stephen Baxter was born in Liverpool in 1957. He is a trained engineer with degrees from Cambridge (mathematics) and Southampton Universities (doctorate in aero engineering research). He worked as a teacher of mathematics and physics, and for several years in information technology. In 1991 he applied to become a cosmonaut, aiming for the spot on Mir eventually taken by Helen Sharman. Stephen has been a full time author since 1995.

He is the author of over 30 books, all published in the US and UK, and several in Germany, Japan, France, and other countries. His novel “Voyage” was dramatised by for BBC Radio in 1999. His TV and movie work includes development work on the BBC’s “Invasion Earth” and the script for the Episode 3 of “Space Island One”, broadcast on Sky One in January 1998. His non-fiction includes the books Deep Future and Omegatropic.

He has won many awards for his novels. Several of his short stories have won prizes, including the “Writers of the Future” contest. He is a lifetime supporter of Liverpool FC.


Astronomers have discovered (as reported in one of our recent workshops) that Pluto may have not one, but three moons, which will make it the first body in the Kuiper Belt known to have more than one satellite. The candidate moons, provisionally designated S/2005 P1 and S/2005 P2, are approximately 27,000 miles away from Pluto --in other words, two to three times as far from Pluto as Charon. They are tiny, with estimated diameters between 40 and 125 miles. Charon, for comparison, is about 730 miles in diameter, while Pluto itself has a diameter of about 1410 miles. The team plans to make follow-up Hubble observations in February to confirm that the newly discovered objects are truly Pluto’s moons. Only after confirmation will the International Astronomical Union consider permanent names for the objects.

The Hubble telescope’s ‘advanced camera for surveys’ observed the two new candidate moons on May 15. Three days later, Hubble looked at Pluto again. The two objects were still there and appeared to be moving in orbit around Pluto. A re-examination of older Hubble images taken on 2002 June 14 has confirmed the presence of both P1 and P2 near the predicted locations based on the 2005 Hubble observations. The team looked long and hard but unsuccessfully for other potential moons around Pluto.


Astronomers using the Keck II telescope report the discovery of a second satellite of the transneptunian object 2003 EL61. The satellite is more than four magnitudes fainter than the primary and appears to have a circular orbit with a 34.1-day period. 2003 EL61 is the third-brightest Kuiper-belt object, after Pluto and 2005 FY9. About 10% of Kuiper-belt objects have satellites, but until recently no other object in the Kuiper belt was known to have more than one.


NASA has published plans for the next generation of spacecraft to take people back to the Moon and on to Mars and other destinations. The study makes specific design recommendations for a vehicle to carry crews into space, a family of launch vehicles to take them to the Moon and beyond, and a ‘lunar mission architecture’ for landing on the Moon. It also recommends the technologies that NASA should pursue in the near term. The study will assist NASA in achieving President Bush’s ‘vision for space exploration’, which calls for the agency to return the space shuttle to safe flight, complete the International Space Station, return to the Moon, and continue exploration to Mars and beyond.

America’s next-generation spacecraft will use an improved, blunt-body crew capsule, and will accommodate up to six people. The spacecraft will be built upon the foundation of the proven designs and technologies used in the Apollo and space shuttle programmes, while having far greater capability. It will be able to carry larger and heavier cargoes into space and allow more people to stay on the Moon for longer periods of time. The new spacecraft will be able to be configured either to support human explorers or fly unpiloted to carry cargo. Its design allows the flexibility to ferry crews of three astronauts, plus additional supplies, to and from the International Space Station, take four crew members to lunar orbit, and eventually maintain up to six astronauts on a mission to Mars. Crews and cargo will be carried into orbit by a launcher consisting of a solid-propellant booster and an upper stage powered by a Shuttle main engine that can lift 25 metric tons. The spacecraft is intended to be safer than the space shuttle because of its in-line design and launch-abort system.


Images returned during Cassini’s recent fly-by of Titan show evidence of what appears to be a shoreline cutting across the southern hemisphere, dividing a distinct bright and dark region roughly 1,700 kilometres long by 170 kilometres wide. Next to an area that is bright and possibly rough is one that is very dark and smooth. Patterns in the dark area indicate that it may once have been flooded with liquid that may now have partially receded. Bay-like features also lead scientists to speculate that the bright--dark boundary is most likely a shoreline.

New Scientist

The Andromeda galaxy is thought to have at its core a super-massive black hole that the Hubble telescope now finds to be surrounded by a disc of young stars. The newly discovered disc is composed of over 400 very hot, young blue stars, orbiting like a planetary system very close to the black hole. That puzzles astronomers because the black hole’s intense gravitational field should have torn apart any clouds of matter long before they could coalesce to form new stars. The stars form a very flat disc that is only one light-year across. An elliptical disc of older red stars surrounds it, spanning about five light-years. Since the two discs appear to be in the same plane, they are probably related, but no one understands how either disc came into being. Spectroscopic observations made by Hubble suggest that the disc of blue stars is only about 200 million years old, while the Galaxy itself is far older. They also allowed astronomers to determine the movement of the blue stars and thereby estimate the black hole’s mass. It really IS super-massive, with a mass 140 million times that of our Sun.


A team of astronomers using the VLT has discovered a large population of distant galaxies observed when the Universe was only 10 to 30 per cent of its present age. A total sample of about 8,000 galaxies selected only on the basis of their observed brightness in red light was found to include almost 1,000 bright and vigorously star-forming galaxies that were formed between 9 and 12 billion years ago, i.e. about 1,500 to 4,500 million years after the Big Bang. The galaxies had been missed because previous surveys had selected objects in a much more restrictive manner. While observations and models had previously indicated that the Universe had not yet formed many stars in the first billion years of cosmic time, the discovery calls for a significant revision, since it now seems that stars formed two to three times more quickly than some astronomers had thought.

The Register

The European Space Agency is planning a mission to see how well current technology could deal with the threat of an asteroid impact. For a rehearsal deflection mission, dubbed Don Quixote, the agency has selected asteroids 2002 AT4 and (10302) 1989 ML as possible mission targets, but the final decision will be made when the launch date has been fixed. The mission will see two spacecraft travel to the chosen asteroid. The first, called Sancho, will arrive several months in advance of the second, Hidalgo. When Hidalgo arrives to smash into the asteroid, Sancho will be there to observe any changes to the asteroid’s orbit.


Astronomers have discovered that one of the most distant galaxies ever seen is unusually massive and mature. The galaxy, named HUDF-JD2, appears to have built up amazingly quickly, within the first few hundred million years after the Big Bang. It put about eight times more mass into stars than there is in our own Milky Way today, and then, just as suddenly, it stopped forming new stars. The galaxy was identified among approximately 10,000 others in a small patch of sky called the Hubble Ultra Deep Field. It represents an era when the Universe was only 800 million years old, about five per cent of its present age. Scientists studying the Ultra Deep Field found the galaxy in Hubble’s infrared images. They expected it to be young and small, like other known galaxies at similar distances. Instead, they found evidence that the galaxy is remarkably mature and much more massive. Its stars appear to have been in place for a long time. Moreover the galaxy looks even brighter in longer-wavelength infrared images from the Spitzer space telescope. Spitzer is sensitive to the light from older, redder stars, which should make up most of the mass in a galaxy. The infrared brightness of the galaxy suggests that it was already comparable in mass to present-day large galaxies.

BBC News

European Space Agency member states have approved funding for the ExoMars mission --a key milestone in the Aurora programme, ESA’s vision to send spacecraft and eventually astronauts to the Moon and Mars. In the near term, it focuses on robotic missions --ExoMars in 2011, followed by an international Mars sample-return mission. Science minister Lord Sainsbury said that, as a major contributor, the UK will have a leading role in the programme, which should improve our understanding of Mars and the Solar System. The bulk of the money will be used to develop ExoMars, with the rest being used for basic research into future missions to the Moon and Mars. The UK is contributing £73m out of a total subscription of around £508m. That should give British industry a considerable share of the work, perhaps allowing it to regain confidence lost as a result of the ill-fated Beagle 2 mission.


The Mars Express spacecraft, which has been orbiting, Mars since 2003 has been granted a mission extension of one Martian year (nearly two Earth years). Mars Express has helped to give us a more complete view of the planet, including evidence for atmospheric methane, a frozen sea and ‘geological’ activity. But one of its instruments may now have stopped working, and deployment of its radar was delayed for a year. The Marsis (Mars Advanced Radar for Subsurface and Ionosphere Sounding) was finally deployed in the middle of this year after fears that one or both of its 20m-long booms might hit the spacecraft after opening out. The mission extension should allow Marsis to restart its search for water reservoirs beneath the planet’s surface. Other instruments have been measuring the composition and characteristics of the Martian surface and atmosphere, and have suggested that volcanic and glacial processes have occurred much more recently than had been supposed.


The twin Mars rovers have successfully explored the surface of the planet for a full Martian year (687 Earth days). The rovers’ original mission was scheduled for only three months. Both rovers keep finding new variations of bedrock in the areas that they are exploring on opposite sides of Mars. The geological information that they have collected suggests that ancient Martian environments included periods of wet conditions. Aided by a power supply from batteries charged by Spirit’s solar cells, researchers have been using one of the rovers at night for astronomical observations. One experiment watched the sky during a meteor shower as Mars passed through the debris trail left by a passage of Halley’s comet.


The Earth’s north magnetic pole is drifting away from North America and toward Siberia at such a speed that Alaska might lose its spectacular Northern Lights in the foreseeable future. In spite of accelerated movement over the past century, the possibility that Earth’s modestly fading magnetic field will collapse is remote, but the shift could mean that aurorae might become more visible in more southerly areas of Siberia and Europe. The magnetic poles mark the axis of the magnetic field generated by liquid iron in the Earth’s core and are far from coinciding with the geographical poles. Scientists have long known that the magnetic poles migrate, and that at long intervals they exchange places, although why they do so is unknown. Previous studies have shown that the strength of the field has decreased by 10% over the past 150 years; during the same period, the north magnetic pole has wandered about 685 miles out into the Arctic. The rate of movement has increased in the last century in comparison with the fairly steady movement of the previous four centuries.


Observations of Comet 9P/Tempel 1 made by the Rosetta spacecraft after the Deep Impact collision suggest that, if Tempel 1 is at all typical, comets are ‘icy dirtballs’ rather than ‘dirty snowballs’ as previously believed. In July this year, the Deep Impact mission sent an impactor probe to hit Tempel 1. The collision was expected to excavate a crater with a diameter of about 100-125 metres and to eject cometary material. It vaporised 4500 tons of water, but surprised the investigators by releasing even more dust. At a distance of about 80 million kilometres from the comet, Rosetta observed before and after the impact and measured the water vapour content and the cross-section of the dust created by the impact. The scientists could then work out the corresponding dust/ice mass ratio, which is larger than one, so it looks as if Tempel 1 is composed more of dust held together by ice, rather than made of ice contaminated with dust. The scientists did not find evidence of enhanced outburst activity of Tempel 1 in the days after the impact, suggesting that impacts of meteoroids are not the cause of cometary outbursts, at least in the case of Tempel 1.


The Japan Aerospace Exploration Agency (JAXA) has reported that a miniature robot, released by the Japanese space probe Hayabusa in the course of its investigation of the small asteroid Itokawa, was lost before it was able to land on the asteroid’s surface. Itokawa, a 600m-long asteroid that travels in an orbit that takes it between the Earth and Mars, is named after Hideo Itokawa, the father of Japan’s space exploration programme. It is currently around 290 million km away from the Earth. Hayabusa, which was launched on 2003 May 9, has been hovering over Itokawa for almost two months. Minerva, a 10-cm-long can-shaped robot, was designed to gather information on Itokawa as part of a rehearsal for Hayabusa’s own landing, scheduled for November 19.

Minerva’s landing was to have been the first attempt by Japan to send information-gathering equipment to an extra-terrestrial object. Equipped with a camera and thermometers, Minerva was meant to hop around Itokawa and send data such as surface temperatures and images back to Earth via Hayabusa. A previous attempt to land Minerva earlier this month was aborted owing to technical problems.


The Spitzer telescope has detected for the first time the building blocks of planets around brown dwarfs, suggesting that such failed stars probably operate the same planet-building process as proper stars are supposed to do. There are tiny crystals and dust grains circling five brown dwarfs located 520 light years away in the constellation Chamaeleon. The crystals, composed of a green mineral commonly found on Earth and known as olivine, are thought to be the building blocks of planets.


Scientists using the Spitzer space telescope say that they have detected light that may be from the earliest objects in the Universe. A 10-hour observation of an area in the constellation Draco by Spitzer’s infrared array camera showed a diffuse glow that may be from Population III stars, a hypothesised class of stars thought to have formed before all others. Theorists say that some of the first stars may have been over a hundred times as massive as the Sun and extremely hot, bright, and short-lived, each lasting only a few million years. The ultraviolet light that they emitted would by now have been shifted into the infrared by the Universe’s expansion. The Spitzer observation confirms a result from the Cosmic Background Explorer satellite in the 1990s that suggested that there might be an infrared background that could not be attributed to known stars. It also supports a 2003 estimate, made by users of the Wilkinson Microwave Anisotropy Probe, that stars first ignited 200--400 million years after the Big Bang.


An international team of astronomers has used the Hubble Space Telescope to observe the spectrum of the white dwarf Sirius B. The new results allow the white dwarf’s mass to be determined from the red shift caused in the spectrum by its intense gravitational field. Scattered light from the very bright Sirius A, only a few seconds of arc away, has presented great difficulties for Earth-based observers. Sirius B has a diameter of 7,500 miles, less than the size of the Earth, but it is enormously dense. Its gravitational field is 350,000 times greater than ours. The new measurements show that Sirius B has a mass that is 98% of that the Sun; Sirius itself has a mass twice that of the Sun and a diameter of 1.5 million miles.

Bulletin compiled by Clive Down
© 2005 the Society for Popular Astronomy

When fact and fiction meet

The concept of cheaper and more easily accessible space flight is another interesting feature of the Stephen Baxter novel “Time” mentioned earlier in this issue. In the novel, a maverick “privateer” launches a cheap and cheerful space probe from the Mojave desert towards the asteroid Cruithne. The following article may ring some bells for those who have read the novel.

Virgin Galactic and the New Mexico Spaceport

Leonard David
The first purpose-built commercial spaceport for the personal space flight industry is to be constructed in New Mexico, a deal struck between the state and Virgin Galactic, the private spaceline firm created by British billionaire, Sir Richard Branson. Details of the partnership were unveiled this month in a Santa Fe, New Mexico gathering of state officials led by Governor Bill Richardson, spaceport planning officials, and leaders of Virgin Galactic, including Branson. Richardson announced that he will work with the state legislature to secure a three year commitment for a total of $100 million for the state’s share of the funding to build the world’s first commercial spaceport to be built in southern New Mexico. The Governor’s funding package will be the cornerstone of a larger $225 million financial construction package that includes local, state and federal funding to build New Mexico’s spaceport in Upham, New Mexico. In announcing the partnership, Richardson emphasised that New Mexico wants to be on the ground floor of public space travel. He said that today’s announcement will “change the face of the state and change the face of the world.” Calling it a very simple, but highly significant agreement, Richardson explained that the state of New Mexico “will build the first spaceport and Virgin Galactic will locate their mission and headquarters right here in New Mexico.” “I would be interested in being the first New Mexican, flying the first time out of the New Mexico spaceport,” Richardson said in a post-announcement press briefing. Rick Homans, New Mexico Spaceport Authority Chairman and New Mexico Economic Development Department Secretary said that construction of the spaceport will begin as early as 2007 and be completed by 2009 or 2010.

To boldly go.....

Branson explained that with the historic partnership, “New Mexico will be known around the world as the launch pad of the new space industry.” He said that within a few years “…we intend to take two to three flights a day to space from New Mexico.” “We’re going where no one has gone before. There’s no model to follow, nothing to copy. That is what makes this so exciting,” Branson explained. “We might even be able to allow those aliens who landed at Roswell 50 years ago in a UFO a chance to go home.” Will Whitehorn, president of Virgin Galactic, said that his company believes the future of space doesn’t lie in just ground-based rocketry. Rather, air-launched spaceships are the way to establish safe, affordable, mass transportation into space. Whitehorn said that it has taken governments four decades to get 500 people to space. “We hope to do that in year one…and eventually be carrying up to 10,000 people a year by the later years of the project,” he said.

Environmentally-friendly spaceport

Prior to commercial space treks from New Mexico, Whitehorn said that Mojave, California is the site for an extensive test program of some 50 to 60 flights of SpaceShipTwo. That craft is now under development by aerospace designer, Burt Rutan and his team at Scaled Composites based in Mojave, California. Current conceptual views of the spaceport, Whitehorn said, are tied to making it “the most environmentally-friendly spaceport/airport type structure that’s been built.” Largely to be fabricated underground, the New Mexico spaceport, for example, would use solar energy and an advanced water collection system. Spotlighting the natural beauty of New Mexico, Whitehorn said that spaceport facilities will be underground as much as possible, “actually hidden from the ground, but visible when you’re in space and coming back to the Earth.” Present at the spaceport announcement was movie actress Victoria Principal. She has already purchased a $200,000 Virgin Galactic ticket. “I am thrilled about the first Virgin Galactic civilian flight scheduled for 2008 and I look forward to being on it,” Principal told the audience. “We’re on an era of a new form of transportation and a way of life that we’ve never known before,” she said.

Five spaceship systems are on order

In a statement from Rutan’s Scaled Composites today, the group congratulated Virgin and New Mexico on their spaceport plans. On October 4, 2004, Rutan’s SpaceShipOne rocketed into history, becoming the first private piloted spacecraft to exceed an altitude of 62 miles (100 kilometres) twice in as many weeks, thus claiming the X Prize Foundation’s $10 million dollar Ansari X Prize. SpaceShipOne’s development was bankrolled by Microsoft’s co-founder, Paul Allen. In July, Branson and Rutan announced their signing of an agreement to form The Spaceship Company to build a fleet of commercial suborbital spaceships and launch aircraft. Under license from Paul Allen’s Mojave Aerospace Company, The Spaceship Company will adopt the “care-free reentry” concept and the “cantilevered-hybrid” rocket motor technology developed for the Ansari X Prize-winning SpaceShipOne. Scaled’s development work on the commercial suborbital spaceliner design will be performed in its current Mojave, California facilities. The Spaceship Company production is also planned to take place at the Mojave Spaceport. The Scaled statement today noted that Virgin Galactic has ordered five spaceship systems and has options on more. Following delivery of the Virgin Galactic ships, The Spaceship Company “will supply flight hardware to additional commercial spaceline operators.”


Thanks to all who contributed to this edition. If you have contributions for future editions, please send them, if possibe, by email to dogden<AT>ntlworld<DOT>com Dave Ogden.

Sky map

The array of colourful stars in this South facing view is well worth studying. From east to west, Regulus in Leo is a spectral type B star. Saturn appears slightly higher as a yellowish colour. Next, with spectral type F, comes pale yellow Procyon, 8th brigtest star in the sky. Lower to the west, and unmistakably the brighest and whitest, at mag -2.1, is Sirius a type A star. Betelgeuse is a red M supergiant star. Its brightness varies from 0.4 mag to 1.3 mag with no set period. During pulsations the diameter varies from 300 to 400 times the diameter of the sun. Rigel, a blue-white B type giant of 0.08 mag is sixth brightest star in the sky. Aldebaran is an orange K type giant star, with a diameter about forty times the Sun's. Finally for comparison is the clear orange glow of Planet Mars. All colours will be more apparent when viewed through a pair of binoculars, e.g. 10x50. Try defocussing the image.

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