A Down to Earth Guide to the Cosmos

There is, however, a more pressing concern for the Earth, although it is still thought to be a billion years away. The Sun is considered to be stable currently but it is slowly increasing in luminosity and temperature, by about 10 per cent every billion years. It is likely that in another billion years the Earth will be too hot for liquid water to exist, and if liquid water does not exist then entire ecosystems will break down and it will be much more difficult for life to thrive or even survive.

It is quite probable that it will be the evolution of the Sun that ultimately brings about the demise of life on Earth and one day in the future completely destroys it, but it is not just the Sun we should be keeping an eye on as there is more an imminent threat from silent, dark and potentially deadly asteroids. You only have to look at objects in the Solar System – the Moon, Mercury, Mars and even the Earth – to see the effects of pieces of rock flying around unchecked. The Moon has countless examples of tiny impacts where small rocks have crashed into it, leaving dents that we see as the craters pockmarking its surface. By studying the distribution and formation of the craters on the Moon we can see that impacts happened with more frequency during the Solar System’s early history. The Earth is moderately protected from such events by its atmosphere, which tends to destroy the rocks as they fall to Earth as meteors or shooting stars. We are generally safe from smaller impacts, but what about larger ones? Those are the ones we need to keep a lookout for.

We can see evidence of large impact events, where much larger rocks tear through the atmosphere and make it to the surface, throughout Earth’s history. The most famous of these are the asteroids that crashed to Earth causing the extinction of the dinosaurs, or the asteroid around 60m in diameter that exploded about five kilometres over Tunguska, Russia, in 1908, flattening trees and breaking windows for hundreds of kilometres around. Over time it is possible that we will be getting safer, as many of the larger rocks should have hit by now but even if they have, there may still be others which could pose a threat.

There are around 9000 near-Earth asteroids, as they are known, with orbits which take them close to or, in some cases, across the orbit of Earth. These orbits are very well understood and there are none that pose a significant danger in at least the next few hundred years. It is not the ones we know about that should worry us though, but the ones we have not discovered yet, and there may be plenty out there. The asteroid belt between Mars and Jupiter occasionally ejects objects through collisions between asteroids but the greater concern is the Kuiper Belt, beyond the orbit of Neptune, where there are thousands of pieces several hundred kilometres across. Generally they are dark and difficult to spot and it is left to a mere handful of automatic sky surveys such as LINEAR (Lincoln Near Earth Asteroid Research) and NEAT (Near Earth Asteroid Tracking) and whole armies of amateur astronomers around the world to scour the skies. The task is daunting, however, and is rather like looking for a needle in a haystack at night, but fortunately other automated searches are being developed to identify risks early enough to allow some sort of defensive action to be taken.

In reality the asteroid threat is unlikely to destroy the Earth completely but there is a very good chance that a large-scale impact could erase life from its surface. Impacts of this type thankfully do not come along that often but, when they do, they cause worldwide devastation. The last mass extinction caused by asteroid impact was 65.5 million years ago and it brought with it the demise of the dinosaurs and 75 per cent of all species, but on average the Earth sees impacts from asteroids at least 5km in diameter every 10 million years. With impacts of this scale, millions of kilograms of debris can be thrown into the atmosphere, blocking light from reaching the surface and plunging the Earth into a global winter that might last hundreds if not thousands of years. Tsunamis, earthquakes and extreme geological activity are just some of the effects of such large-scale impacts and it could take several million years for life to recover.

There is another risk to the sustainability of life on Earth and it is thought to come either from the collision of two collapsed stars or from the collapse of a supermassive, fast-rotating star at the end of its life. This event is seen as a brief burst of gamma radiation which can last from fractions of a second to a few minutes. It is believed that a highly focused beam shoots out into space, and if you are in the line of sight, you see the burst. Following the initial blast, known as a gamma ray burster, there is an afterglow which can last several hours longer and is seen in different wavelengths. The process is still not fully understood but these events are observed roughly once a day and are thought to emit 10 quadrillion times more energy than the Sun, making them the most luminous and violent events ever observed.

The bursters were first discovered in the 1960s by satellites that were designed to detect gamma radiation bursts from nuclear weapons testing. With the detection of a burst in July 1967 more accurate satellites were launched to investigate further, and an additional fifteen GRBs were picked up. By analysing the timings and positions it was possible to find an approximate location which ruled them out as man-made in origin. The closest burster, GRB031203, was detected in December 2003 in the constellation of Puppis at a distance of 1.3 billion light years, but to date none have been observed in our galaxy. Fortunately, at those distances they are nothing more than a scientific curiosity, but if one occurs closer to home then we might be in trouble.

Most of the stars that can be seen with the naked eye are no more than just a few thousand light years away, so if a gamma ray burster went off among the stars it might be bad news for life on Earth. We can tell if a star is near the end of its life and a candidate for such an event, but we may be unable to detect a binary star system on the brink. If one did go off within a couple of thousand light years from us and send the burst of radiation in our direction then it is likely that it would outshine the Sun for a brief moment and the initial burst would fry the atmosphere, creating elements that would destroy the ozone layer. With no ozone layer the full force of ultra-violet radiation from the Sun would make its way to the surface of our home, cause severe cases of skin cancer, kill off the plankton at the bottom of the food chain and destroy oxygen-creating plants. The result would be catastrophic.

Whether the end of the world is considered to be Earth’s complete destruction or it being left in an uninhabitable state, there is no dispute that the ultimate end must be finally and irreversibly defined by the end of the Universe itself. As we have seen, the discovery by Edwin Hubble that the Universe is expanding led to the conclusion that it formed in the Big Bang, but its fate is a little harder to pin down. It may continue to expand for ever or eventually stop expanding and collapse back in on itself. The answer will be found by identifying how much matter is in the Universe, or more accurately its density. Density is a term that refers to the amount of matter (mass) per unit volume and measuring the density of the Universe has proven to be quite tricky. Of course, it is impossible to actually measure the density of the entire Universe so, instead, calculations of the volume and mass of a small portion of space are made and used to extrapolate the overall density.

If we measure the speed of the expansion of the Universe it is possible to determine what the density of the Universe needs to be in order for there to be enough matter and hence gravity to arrest the expansion. We can visualize how matter interacts with the Universe by way of gravity by imagining a sheet of rubber. If a large heavy object were placed on the sheet it would sink into it making a depression. In this analogy, the heavy object could represent a star and the sheet, the fabric of space. The depression would represent gravity and any object travelling through it or close by would get drawn towards the massive object.

The critical density is a term used to define how much material is needed for there to be enough gravity to halt the expansion, and its value is 1 million trillion trillionth of a gram per centimetre. This is an incredibly small amount of material but it is the average density that is important and, of course, in some regions of space, such as in the centre of a star, the density is significantly higher. If it turns out that the actual average density is less than the critical density then the force of gravity will not be enough to halt the expansion and the Universe will continue to expand for all eternity. It may be that the density is more than the critical density, in which case gravity will ultimately overcome the expansion, stop it and a period of contraction will follow. There is a third option where the density of the Universe is exactly the same as the critical density, in which case the Universe is considered ‘flat’ and it will continue expanding, but at a slowly decelerating rate, yet will never actually stop.

If all of the visible matter in the Universe is added up it seems to fall far short of the quantity needed to halt the expansion, yet some theories suggest there should be just enough matter to produce a flat Universe that is locked in an ever-decreasing rate of expansion. One possible explanation for this lies with a rather strange and exotic material mentioned in Chapter 10, called dark matter, which was first discussed by Jan Oort in 1932. His theory, which suggested there was a new type of material that would be hard to directly detect, was in response to the observed orbital speed of stars in the Milky Way and other galaxies, which was higher than expected – in fact, the stars should have been flung out of the galaxy at the speed they were travelling yet they clearly were not. As we touched upon briefly in February’s sky guide, gravitational lenses are another phenomenon which hints at the presence of more material than we are able to detect. These natural lenses are visible to us when a massive galaxy or galaxy cluster distorts the light from a more distant object, creating a lensed image of it. By measuring the amount of distortion, it is possible to calculate the mass of the object doing the lensing and observations have shown that there is significantly more matter than we can see directly. The exact nature of dark matter is still not well understood but it is now thought to make up 83 per cent of the matter in the Universe.

There is one further twist in the search for the end of the Universe and it relates back to observations in 1988 of supernovae in distant galaxies. Specifically, type 1a supernovae are thought to result from the violent explosion of a white dwarf star in a binary star system and, due to the nature of the event, will always give off the same amount of energy and shine with a very specific brightness. Comparing the apparent brightness in the sky with the actual brightness allows the distance to be calculated. Another technique for measuring vast distances in space relies upon studying the spectrum of the object and calculating the apparent shift in the position of characteristic lines in the spectrum. Doing this allows us to determine the speed away from us and with a little mathematics we can determine the distance of the object, as we saw in Chapter 5. When this was done for the supernovae, there was a problem: they were found to be 15 per cent further away than they should have been. There are a few explanations for this, all but one of which have now been discounted: that the rate of expansion of the Universe is accelerating.

The acceleration is explained by a concept called dark energy, which exerts a pushing force on the Universe in competition to the pulling force of gravity. There are two key theories to explain dark energy, one of which has its origins in the very early stages of the evolution of the Universe. A few fractions of a second after the Big Bang there was a brief period when gravity effectively became repulsive causing the Universe to expand faster than the speed of light. It is thought that dark energy may be the aftermath of this ‘inflationary’ period.

Another possible explanation is that the apparently empty ‘space’ that fills the gaps between the galaxies is far from empty and, instead, is full of new, temporary particles that constantly appear and disappear. When this theory is investigated it seems there is far too much dark energy than is required to drive the expansion we see in the Universe. The alternative to these two theories is simply that our theory of gravity is plain wrong. An uncomfortable statement to make, but science is as much about proving things to be wrong as it is proving them to be right, so maybe, just maybe, we need to look at the theory of gravity in more detail. Taking into account the observations of the expansion of the Universe and the estimates of matter that we can see in the sky, it seems that dark energy must represent 70 per cent of the Universe with dark matter making up 25 per cent and what we amusingly class as ‘normal matter’ a mere 5 per cent.

Whether the Universe continues expanding or not will determine its ultimate fate and looking at the latest observations it looks like it will expand indefinitely. If it does continue to expand for ever it could face a fate known as ‘the Big Freeze’. As it continues to expand without end, it would cool, ultimately reaching a temperature that is too cold for life to exist. But it gets more gloomy than that. Slowly, over billions of years, the formation of new stars would cease, and the remaining stars would run out of fuel and, one by one, would die. The Universe would get darker and darker as fewer and fewer stars were present to light its distant corners. They might all eventually end up inside black holes, which themselves might slowly radiate energy off into space until they too dissolved and the Universe reached a cold, uniform temperature, dark and bleak. If this is to be the fate of the Universe, then it is thought this state will be encountered in around 1 million billion years (the current age of the Universe is 13.7 billion years).

It is quite easy, yet perhaps saddening, to think of the Universe ending in this way, but an alternative theory comes from research into dark matter and quantum mechanics. It suggests the Universe might be oscillating, which means that the current period of expansion may eventually be halted until reversed into a period of contraction. The Universe would shrink down to a point just before it becomes a singularity, a point with zero volume and infinite density where gravity may briefly become repulsive enough to kick-start another Big Bang. The idea of the oscillating Universe goes quite some way to resolving the unanswered question of what happened before the Big Bang, yet it does leave the rather unpalatable possibility that we could be held in an infinite loop of Big Bang followed by expansion, contraction and then a big crunch before the cycle continues.

The idea of an oscillating Universe is a step on from the idea of a big crunch, where the Universe collapses back into a singularity, ending at this point. This is not a popular idea among many scientists as it leaves the awkward questions of what happened before and what happens after. There are other equally unpopular theories to explain the fate of the Universe, such as the big rip, whereby the rate of expansion accelerates further until all matter, large or small, is ripped apart into individual particles; or the multiverse theory, in which an infinite number of Universes exist, popping in and out of existence as they are all formed in a big bang and destroyed in a big crunch.

Regardless of how the Universe will end, it seems our home, the planet Earth, is ultimately doomed. In billions of years’ time, the Sun will die, expanding to colossal proportions as a red giant and possibly swallowing up the Earth. Even if the Earth survives the fiery death of the Sun it will join the rest of the matter in the Universe in a common fate. Exactly what form that fate will take is, as yet, a matter for conjecture, but the answer will be found in a deeper understanding of the nature of matter and energy. One of Einstein’s famous equations explains that energy and matter are interchangeable and it seems certain that the Universe started, and will end, as energy. For a period of time, that energy was transformed into matter through some beautiful and quite elegant processes, but understanding the fate of the matter we see in the night sky today will undoubtedly keep scientists busy for centuries to come.

December: Northern Hemisphere Sky

The northern and southern hemisphere skies share a very well-known constellation this month, Orion. The great hunter straddles the celestial equator with his shoulders and head in the northern hemisphere sky and his belt and feet in the southern hemisphere. The best place to start this star guide is from Orion’s famous three-star belt, which lies just south of the celestial equator.

Just to the north of the belt lie two prominent stars which mark the shoulders of the hunter, Betelgeuse to the east and Bellatrix to the west. The two stars are very different: as we have seen, Betelgeuse is a red supergiant with a surface temperature of only 3500 degrees, in comparison to Bellatrix, a blue giant with a surface temperature over six times higher at 21,500 degrees. Unlike most stars, which we see as points of light, Betelgeuse actually appears in the sky as a measurable disc, second in size only to the Sun. As with most stars of this type, Betelgeuse’s light output varies, and it has a regular change in diameter, from about 500 to 900 times that of the Sun, which causes the variation. This instability is seen because it is an ageing star, leading some astronomers to believe it may go supernova and die violently within the next 1000 years. Bellatrix, to the west of Orion, can expect a different fate in a few million years, when it will evolve into a smaller red giant and then quietly lose its outer layers into space, leaving behind a white dwarf star.

Between Betelgeuse and Bellatrix and a little to the north is a tiny, faint grouping of three stars with the brighter one, by the name of Lambda Orionis, marking the hunter’s head. The remainder of the northern part of the constellation depicts a club being held aloft from Betelgeuse, marked by Mu Orionis to the north-east, and then two pairs of stars, each of which is roughly parallel with the celestial equator and heads to the north from Mu Orionis. A shield is then depicted by a curve of faint stars centred on Pi Orionis to the west of Bellatrix.

Another prominent red star, Aldebaran, can be seen to the north-west of Orion and is the brightest star in the constellation of Taurus. A great way to confirm that you have found Aldebaran is to follow a line extending north-west from the three-star belt of Orion, which points straight to it. Its colour, which is similar to that of Betelgeuse, tells us that it is a star nearing the end of its life, and at a distance of 65 light years it is likely to be the best candidate for observing what may be the fate of our Sun.

As we have seen, Aldebaran sits in a prominent ‘V’ shape of stars known as the Hyades cluster, though the cluster is not related in any way to Aldebaran, which is almost 100 light years closer to us. It is a group of around 400 stars that have been shown to share the same motion through space and have formed at the same time out of the same molecular cloud. At 625 million years old, the Hyades Cluster is one of the oldest known open clusters since most tend to disperse before 50 million years. Only those clusters a good distance from the gravitational disturbance of the galactic centre appear to survive for longer, although it does seem to be losing the odd star, such as one now in the constellation of Horologium in the southern hemisphere sky.

Extending the southern half of the ‘V’ of the head of Taurus towards the east leads to Zeta Tauri. Elnath, the brighter star to its north, and Zeta Tauri together represent the horns of the bull. Zeta Tauri is a hot blue giant star with a temperature of 22,000 degrees and spins at such a rate that it is losing matter to the surrounding space, forming an accretion disc. Elnath is cooler at just 13,500 degrees.

Zeta Tauri is a particularly well-known star because it acts as a useful guide for finding the Crab Nebula, or M1, which is the remnant of a star that exploded as a supernova in 1054. It is easily found after locating Zeta Tauri because it is just 1 degree to the north-west. When the original star exploded as a supernova it gave off so much light that it was visible to the naked eye during daylight. The light has now faded to a much fainter 8th magnitude, which means small telescopes are needed to pick it up. From dark sites on a moonless night it is just possible to see it as a misty patch with a pair of 10x50 binoculars but a telescope is definitely the best instrument for this object, a 15cm aperture giving a reasonable view. Even then, it will only look like a slightly misshapen oval with a hint of dark and light patches. The nebulosity is all that is left now of the outer layers of the star which exploded, although deep in the core of the nebula is a pulsar, a stellar corpse spinning thirty times every second.

Elnath, the star marking the northern tip of the horn, is on the border of the constellation of Auriga further north. Auriga appears in the sky as a slightly squashed pentagon and lies in a dark portion of the Milky Way. Directly north of Elnath is Capella, the brightest star in the constellation and a well-known binary star system. The two stars are similar to the Sun and have comparable surface temperatures, although both are about ten times its size. They lie about 96 million kilometres apart and at a distance of 42 light years amateur telescopes will not separate them visually.

To the south of Capella is a tiny triangle of three stars known as the Kids and marked by Epsilon Aurigae at the northern tip and Eta and Zeta Aurigae at the triangle’s base. Epsilon Aurigae is a peculiar eclipsing binary star whose main star is a yellow supergiant about twenty times the mass of the Sun. As an eclipsing binary we can tell it is orbited by another star, or, more accurately, that together they orbit a common centre of gravity. These eclipses are strange because they happen every 27.1 years and last for almost two years. Current theory suggests that the companion is surrounded by a dust ring which is also eclipsing the main star. This means the eclipses last much longer than they would normally do if just the star was blocking the light.

South of the Kids grouping is Al Kab, the third-brightest star in the constellation of Auriga, to the east of Capella is Menkalinan and to its south is Theta Aurigae. Within the lines formed by these stars are two open star clusters, M36 and M38, which we saw briefly in January’s sky guide. M38 can be located on a line between Theta Aurigae and Al Kab and at 6th magnitude is visible to the naked eye when viewed from a dark site. There are about a hundred or so stars in this cluster, many of which can be seen through a modest telescope against the background of stars from the Milky Way. It lies at a distance of 4200 light years, making it a little more distant than its companion, M36.

Also known as the Pinwheel Cluster, M36 can be found around 2 degrees to the south-east of M38 and is fractionally brighter. It is also a little smaller than M38 and contains only about sixty stars, all of which seem to be hot young stars compared to M38, which surprisingly for an open cluster has its share of ageing red giant stars. One other cluster is prominent in Auriga, M37, and it is considered by many to be the best open cluster in the sky. It has around 500 member stars, covering an area about the size of the full moon, and of the three clusters in Auriga is the most distant, at 4600 light years. It is also the oldest of the three clusters, at an age of 300 million years, and like M38 some of its stars have already evolved into red giants. M37 is found slightly to the east of the line between Theta Aurigae and Elnath and about halfway along.

December: Southern Hemisphere Sky

Orion is prominently placed in the December sky and is found right on the celestial equator with his head and shoulders to the north and famous belt and legs to the south. For southern hemisphere observers, the hunter appears upside down in the sky but the belt stars make a fantastic easily recognized starting point for this month’s guide.

Orion’s three-star belt is marked from east to west by Mitaka, Alnilam and Alnitak.

Directly south of Alnilam is Orion’s sword, made up of three faint stars. The central star looks a little fuzzy to the naked eye and is one of the most famous deep-sky objects, the Great Orion Nebula, which is an area where hot young stars are forming. Nebulae actually surround all three stars in the sword but it is the portion in the centre, surrounding Theta Orionis, which is most spectacular. The area is a vast cloud of mostly hydrogen gas and dust and, over many millions of years, gravity has caused the cloud to contract. Eventually the pressure inside the cloud became so intense that nuclear fusion started and stars were born. Inside the Orion Nebula, even small telescopes will reveal a tiny cluster of stars called the Trapezium which were formed out of its material 100,000 years ago. Images of the area show the nebulosity as a red colour, which is because the stars within have caused the gas to glow and give off its own light. Telescopes of 10cm and above reveal not only the Orion Nebula and its many dark rifts and knots, but also M43 to its north. Nebulosity can be detected around some of the other stars in the sword and will appear blue in images. These are reflection nebulae, so called because they shine by reflecting starlight rather than emitting their own.

To the north-east of the sword lies the eastern foot of Orion, marked by the bright white supergiant star Rigel. It is thought that Rigel is one of the most luminous stars in this region of the Milky Way and it shines with a brightness equivalent to around 50,000 Suns. Like many high-mass stars, Rigel has evolved quickly and has already started to run out of hydrogen in its core so is now fusing helium into carbon. Marking the western foot is the sixth-brightest star in Orion, Saiph, a hot blue-white supergiant a little over twice as hot as Rigel at around 26,000 degrees.

South of Orion is a relatively faint constellation known as Lepus with its two brightest stars, Arneb and Nihal, which can both be seen to the south-east of Saiph and form a line that points broadly to the south, almost at right angles to the celestial equator. Of the two, Arneb is the pale yellow star to the north and nearest to Orion, and Nihal is the more orange-coloured star further south.

A rather inconspicuous jewel of the sky lies on the eastern border of Lepus and is found by drawing a line between Arneb and Mu Leporis (the star to the east of Arneb by a little over 5 degrees). Extend the line beyond Mu Leporis by about 10 degrees and at this location is a beautiful red star, named Hind’s Crimson Star, which is such a deep red colour that it has often been said to resemble a drop of blood against the blackness of space. Even Betelgeuse in Orion or Aldebaran in Taurus are no competition. This star, also known as R Leporis, is a variable star which takes about 430 days to slowly change its brightness from its faintest at magnitude 11.7, requiring a telescope to detect it, to its brightest at 5.5, making it just visible to the naked eye from a dark site and an easy target with binoculars. Its maximum brightness also seems to vary over a period of about forty years, from 5.5 to 6.5. The intensity of the red colour appears to increase as the star becomes fainter through its 430-day cycle.

The reason for the variability is that R Leporis is a carbon star, i.e. it brings carbon to its outer atmosphere through convection currents that build up to a thick carbon envelope through which the starlight must travel. The nature of carbon and its interaction with light means that it absorbs blue light and allows red light through so the star appears particularly red. Every so often, usually at intervals of just over a year, the carbon build-up is ejected from the star by some means, restoring the star to its usual visibility of around 6th magnitude. It lies at a distance of about 1100 light years and is thought to be 250 times the diameter of the Sun. Eventually its outer layers will escape into space, turning the star into a planetary nebula and seeding the galaxy with heavy elements that will ultimately lead to a new generation of stars. It is from stars like R Leporis, which have a high carbon content, that star systems with rocky planets form and provide the basis for life to evolve.

Using Arneb as a starting point again, extend a line southwards through Nihal and about the same distance on is M79, a very nice 8th magnitude globular cluster. It is best viewed through at least a 20cm telescope so that many of the stars in the cluster can be seen individually. Anything smaller than this will struggle to resolve the stars and so will show no more than just a mottled patch of light. M79 is in an area of sky that does not seem to have many globular clusters, which has perplexed astronomers as most clusters seem to be located around the central bulge of our galaxy. It is believed that this cluster and a couple of others may be impostors, having been brought to the Milky Way by the Canis Major Dwarf Galaxy, which is in the process of merging with us.

The next-brightest star seen heading further south from Lepus is Alpha Columbae, which is also the brightest star in the constellation of Columba. Columba lies between Lepus and the bright star Canopus in the constellation of Carina to the south-west, the second-brightest star in the sky. It is easy to spot and cannot be mistaken as it is rivalled in brightness only by Sirius to its north. Just a couple of degrees to the south-east of Alpha Columbae is the orange star Epsilon Columbae and a line between the two extended by about 5 degrees marks the location of NGC1851, one of the other globular clusters thought to have been brought to the Milky Way by the Canis Major Dwarf Galaxy. At 7th magnitude it is easily picked up with binoculars but appears as nothing more than a fuzzy star.

To the west of Columba is the constellation Puppis, which is home to GRB031203, the nearest gamma ray burster to us, which lasted for just twenty seconds back in 2003. To the east of Columba is the small, faint constellation of Caelum, which has no stars brighter than magnitude 5, making it a challenge from all but the darkest sites. Moving further south leads to Pictoris, which looks like a shallow triangle to the south-east of Canopus, with its brightest star, Alpha Pictoris, to its south. About 5 degrees to the east of Canopus is Beta Pictoris, which was the first star discovered to display a protoplanetary disc. These discs ultimately form planets and are evidence that the process of planetary formation is common in the Universe.

One of the showpieces of the sky this month is the Large Magellanic Cloud (LMC), which can be found to the south of Pictoris and looks like a detached part of the Milky Way. As we have seen, it was once thought that the LMC and the Small Magellanic Cloud to its east were galaxies that orbited our own, but it has since been discovered that they are travelling too fast to be gravitationally bound to the Milky Way. In a few billion years’ time, they will depart our region of space and slowly fade in brightness. The LMC is 157,000 light years away and covers an area of sky significantly larger than the full moon. On the western edge of the galaxy is one of the largest areas of star formation in our local group of galaxies, the Tarantula Nebula. It can be seen as a 5th magnitude nebula and shows up well with binoculars, although widefield, low-power telescopes will give the best view.