Are We Inside a ‘Galactic Transport System’?

Wormhole simulation - Credits Davide and Paolo Salucci.

Wormhole simulation – Credits Davide and Paolo Salucci.

In theory, the Milky Way could be a “galactic transport system”

Based on the latest evidence and theories our galaxy could be a huge wormhole (or space-time tunnel such as the one depicted in the recent film Interstellar) and, if that were true, it would be “stable and navigable”. This is the hypothesis put forward in a study published in Annals of Physics and conducted with the participation of SISSA in Trieste [citation below]. Read More →

Researchers Discover Four New Galaxy Clusters

Caption: Perseus galaxy cluster. [D. W. Hogg/M. Blanton/SDSS Collaboration].

Caption: Perseus galaxy cluster. [D. W. Hogg/M. Blanton/SDSS Collaboration].

Four unknown galaxy clusters each potentially containing thousands of individual galaxies have been discovered some 10 billion light years from Earth.

An international team of astronomers, led by Imperial College London, used a new way of combining data from the two European Space Agency satellites, Planck and Herschel, to identify more distant galaxy clusters than has previously been possible. The researchers believe up to 2000 further clusters could be identified using this technique, helping to build a more detailed timeline of how clusters are formed. Read More →

Prawn Nebula and New Stars in High Resolution

The glowing jumble of gas clouds visible in new image make up a huge stellar nursery nicknamed the Prawn Nebula. Taken using the VLT Survey Telescope at ESO’s Paranal Observatory in Chile, this may well be the sharpest picture ever taken of this object. It shows clumps of hot new-born stars nestled in among the clouds that make up the nebula. This image also contains information from images of this object taken by Martin Pugh.

The glowing jumble of gas clouds visible in new image make up a huge stellar nursery nicknamed the Prawn Nebula. Taken using the VLT Survey Telescope at ESO’s Paranal Observatory in Chile, this may well be the sharpest picture ever taken of this object. It shows clumps of hot new-born stars nestled in among the clouds that make up the nebula. This image also contains information from images of this object taken by Martin Pugh.

A glowing jumble of clouds nicknamed the Prawn Nebula containing clumps of hot new-born stars is visible in a new, sharp image taken with the European Southern Observatory’s (ESO) VLT Survey Telescope in Chile as part of a public survey led by University of Hertfordshire astronomers. Read More →

A Universe of New Worlds to Discover & Explore


In 1992, scientists made one of the most significant discoveries in the history of astronomy; the first confirmed detection of an extrasolar planet. For many decades, it had been widely believed that planets existed around stars other than our own, but it was not until the discovery of two planets orbiting a distant star some 1000 light years away (1 light year = about 6 trillion miles) that their existence was proven beyond doubt. As detection methods advance, particularly thanks to the highly successful Kepler Space Telescope launched in 2009, new alien worlds are being discovered almost every week. Read More →

Newborn Stars and their Effect on the Universe

Star Cluster

When galaxies form new stars, they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the early Universe, but are rarer in nearby galaxies. Read More →

A Celestial Primer


Understanding Space – Celestial Objects

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Space is a big, fascinating, and stunningly beautiful place. The universe is full of stars, galaxies, nebulae, planets, moons and much more. Ranging from lifeless rocky worlds such as Mercury to vast galaxies tens of thousands of light-years across, space is home to truly awesome displays of nature. Celestial objects, also known as astronomical objects, comprise the physical entities that make up the universe.

The universe has a hierarchal structure. On the smallest scales of astronomical objects, there is the Earth and our moon. The Earth is part of our solar system of eight planets while, in turn, our solar system is one of billions in the Milky Way galaxy. The Milky Way is one of 54 galaxies in the Local Group, a part of one of many superclusters that make up the universe – everything that exists.

The following guide, roughly in order from the smallest to the largest celestial objects, will help you to understand the scale of the universe, its hierarchal structure and some of the many fascinating things that lie beyond the borders of our world.

1 – Meteors

MeteoriteMeteors are small, rocky debris floating around in the vacuum of space ranging in size from grains of sand to massive boulders. When these enter the atmosphere of Earth or any other celestial body, they are called meteoroids. These bombard us constantly, but the vast majority of them burn up as they descend into the Earth’s atmosphere. This is precisely what shooting stars are – small, burning debris making brief streaks of light in the night sky as they are vaporized. If a meteoroid is either large enough or travelling fast enough to make it through the atmosphere without being annihilated, it will make it to the ground, becoming a meteorite.

Fun Facts about Meteors

  • The largest known meteorite is the Hoba meteorite in Namibia weighing about sixty tons. It is the worlds heaviest naturally occurring chunk of iron and it is believed to have hit Earth’s surface about 80,000 years ago.
  • The best-known meteor showers are the Perseids and Leonids that fall every year in August and November respectively.
  • Some meteorites on Earth originated from Mars, such as the famous Allan Hills 84001 meteorite. This one attracted a great deal of attention due to the presence of possible fossilized remains of Martian bacteria.

2 – Comets

CometComets are small, icy celestial bodies composed of a nucleus, coma and tail. The nucleus comprises the solid bulk of the comet and ranges in size from a hundred meters to a few dozen kilometers. Comets are characterized by spectacular comas and tails, leaving a long trail of bright matter behind them. There are over 4,000 known comets in the solar system and some have been known since ancient times. Many comets have enormous, elliptical orbits around the sun, many reaching maximum distances far beyond the orbit of Pluto.

Fun Facts about Comets

  • Extremely bright comets typically appear no more than once every decade. These are known as the Great Comets and are visible to the naked eye.
  • One of the most famous comets, Halley’s Comet (shown above) may have been the Star of Bethlehem referred to in the Bible. Halley’s Comet makes an appearance every 75 years.
  • The Great Comet of 1811 was clearly visible for almost nine months. It had a coma fifty percent longer than the diameter of the sun – up to 1,000,000 miles long!

3 – Asteroids

Asteroid MissionAsteroids are small celestial bodies of which there are many millions around the Solar System. Asteroids orbit the Sun just like planets do, but they are far smaller. Because of this, they also have negligible gravitational pulls and no atmospheres to speak of. Also, because of their lack of size and gravity, smaller asteroids are irregularly-shaped rather than near-perfect spheres like planets and dwarf planets. The majority of known asteroids are located in the Asteroid Belt between the orbits of Mars and Jupiter. Asteroids are also found in the Kuiper Belt beyond the orbit of Pluto.

Fun Facts about Asteroids

  • An asteroid impact may have been what wiped out the dinosaurs in the Cretaceous-Palaeogene extinction event 65.5 million years ago.
  • Some asteroids have moons (satellites), such as 243 Ida and its tiny moon, Dactyl. Until its discovery, it was thought that only planets had moons.
  • Asteroids may one day be used for mining thanks to their abundance of valuable metals and materials.

4 – Dwarf Planets

Dwarf PlanetDwarf planets are characterized as small planets that are massive enough to have gravitational forces great enough make them spherical in shape. They also orbit the sun directly. Most notably, Pluto is a dwarf planet that was reclassified as such in 2006, until which point it had, since its discovery in 1930, been described as the Solar System’s ninth planet. All of the five known dwarf planets are considerably smaller than the Earth’s Moon. Dwarf planets may also have their own moons. Pluto, for example, has at least five. Dwarf planets are too small and do not have a high enough gravitational pull to be able to retain any more than a trace atmosphere.

Fun Facts about Dwarf Planets

  • Ceres, in spite of being the smallest known dwarf planet, was the first one discovered due to the fact that it is the largest non-planetary body in the inner solar system. It was discovered in 1801.
  • All other dwarf planets are found in the Kuiper Belt extending beyond the orbit of Pluto.
  • In 2015, NASA’s New Horizons space probe will visit the dwarf planet Pluto and take the first ever photos of its surface.

5 – Moons

Europa - MoonMoons, known as natural satellites in the scientific community, are objects ranging in size from tiny asteroids to bodies larger than the planet Mercury. They are gravitationally bound to their host planets, just as the Moon is to Earth. Earth, of course, has only one moon, but some of the other planets in the Solar System have dozens. In total, there are at least 176 moons in the Solar System. Mercury and Venus have none as far as we know, while Mars has two and the gas giant planets have dozens. The first moons discovered around other planets were the four Galilean moons of Jupiter in 1610 by Galileo.

Fun Facts about Moons

  • Many smaller moons are captured asteroids, pulled into the orbit of planets by powerful gravitational pulls. The two Martian moons, Phobos and Deimos are two such moons.
  • One of Saturn’s moons, Titan, is the only moon in the Solar System known to have a thick atmosphere. Because of this and other factors, it remains one of the first places in the Solar System to search for extraterrestrial life.
  • Jupiter has more moons than any other planet in the Solar System with a total of 67! The four largest of these are Io, Europa (shown on right above), Ganymede, and Callisto. Ganymede is actually larger than the planet Mercury. These four moons are known as the Galilean moons.

6 – Planets

PlanetsThere are a total of eight planets in our solar system. Our solar system is comprised of the inner planets and the outer planets. The inner planets, in order of distance from the Sun, are Mercury, Venus, Earth, and Mars. Far beyond the orbit of Mars lie the outer planets, Jupiter, Saturn, Neptune and Uranus. These four planets are gas giants and, thanks to their size and gravitational influence, they each have numerous moons. Gas giants have no known solid surface. The planets of the Solar System vary dramatically. Mercury is a lifeless rock, Venus is a hellish inferno, Earth is home to the only forms of life that we know of and Mars still remains our first candidate in the search for extraterrestrial life either long dead or still present. Since 1995, many hundreds of planets have been discovered orbiting other stars as well. These are known as extrasolar planets.

Fun Facts about Planets

  • There are more than 850 planets orbiting stars other than our own (the Sun), and more are being discovered every week in large part due to the work of the Kepler Space Telescope.
  • Venus is the hottest planet in the Solar System with surface temperatures high enough to melt lead and air pressures as high as those one kilometer under the sea.
  • Water, a key ingredient for life as we know it, is common throughout the Solar System. Water ice is widely distributed on Mars and exists on the Moon, many comets and asteroids, and on various other astronomical bodies.

7 – Stars

StarStars form the center of solar systems, just like our own star, the Sun, is the center of our own Solar System. When you look up at the sky on a clear night, you can start to grasp the vastness of space and the countless trillions of stars in the universe. The vast majority of stars are far more massive than even the largest planets, with the smallest ones being considerably larger the Jupiter and the largest ones being hundreds times bigger than the Sun. The Sun is nothing special as far as stars go and, in fact, there are billions of other stars just like it in our galaxy alone. Just like the Sun, many other stars host planetary systems, some of which may be very much like our own (and possibly home to extraterrestrial life). Stars are classified by spectrum types and are designated by letters. Our sun is a class G star.

Fun Facts about Stars

  • The largest known star is the red hypergiant called VY Canis Majoris. 3 billion kilometers (about 1.86 billion miles) in diameter, the star would extend further than Saturn’s orbit if placed in our Solar System.
  • Our own star, the Sun, is approximately 1.4 million kilometers (nearly 870,000 miles) in diameter.
  • The nearest star to Earth other than the Sun is the triple-star system, Alpha Centauri, 4.3 light-years away. 4.3 light-years equates to approximately 40,000,000,000,000 kilometers. Travelling at 252,800 km/h, the speed of the fastest man-made object, the Helios 2 space probe, would take around 18,000 years to reach it.

8 – Galaxies

GalaxyStars make up galaxies such as our own galaxy, the Milky Way. The Milky Way is one of many billions of galaxies in the known universe. The Milky Way alone contains between 100 and 400 billion stars. Galaxies are vast, gravitationally bound systems containing not only stars, but also nebulae, rogue planets (planets without a host star) and various other celestial bodies. They fall into three broad classes described as elliptical, spiral and lenticular galaxies. Our own galaxy is a barred spiral galaxy characterized by an extremely bright and dense center of stars surrounded by swirling arms. Our own star system lies in one of the arms of the Milky Way orbiting the galactic center at a distance of 26,000 light-years (each light-year is roughly 6 trillion miles). The nearest proper galaxy beyond the Milky Way is Andromeda, about 2.5 million light-years away across a virtually empty void.

Fun Facts about Galaxies

  • The most distant galaxies tell us about the history of the universe. This is because we see them as they were when the light left them – effectively, we are looking back in time.
  • There are only three galaxies visible to the naked eye from Earth. These are the dwarf galaxies known as the Small and Large Magellanic Clouds and the Andromeda Galaxy.
  • There are at least 100 billion galaxies in the known universe, but there may be dozens times more than that.

9 – The Universe

Universe2The observable universe comprises absolutely everything that we can see from Earth. Anything that is further away than the edge of the observable universe is invisible to us due to the fact that the light has not yet completed the long journey to Earth. The furthest we can see is approximately 13.75 billion light-years. The universe is made up of superclusters containing clusters of galaxies such as the Local Cluster where our own Milky Way galaxy is located. What lies beyond the observable universe is not known, although the universe is still generally thought to be finite. The universe is believed to have been created by the Big Bang and has been rapidly expanding ever since.

Fun Facts about the Universe

  • The universe is approximately 93 billion light-years in diameter, but due to the fact that the universe is expanding, we can still see things that are too far away, because we are seeing them as they were when they were closer to us.
  • The largest known object in the universe is the Sloan Great Wall, an enormous wall of galaxies about 1.38 billion light-years in length.
  • The size of the universe and the number of galaxies and stars in them suggest that life-supporting worlds, although clearly rare, could easily number in the billions.

Honorable Mention – Black Holes

Black HoleBlack holes are perhaps the most fascinating and bizarre of all the objects in space. Sometimes, when a star dies, it starts to collapse, the matter of which it is composed becoming more and more densely packed. Eventually, the star is so massive that its gravitational pull becomes so great that the escape velocity reaches the speed of light. When not even light is able to escape the surface, the star becomes invisible and only detectable by its influence on the surrounding area. The black hole is composed of an event horizon that marks the point of no return. Additionally, black holes have a gravitational singularity in the center that is infinitely dense, yet has no volume. At this point, the laws of physics simply break down, making black holes the most enigmatic objects in existence. Black holes are thought to exist in the center of many galaxies, including the Milky Way.

Image Credits: NASA/JPL

Reaching E.T. Through Standardized Protocols

Image Credit: SPDO/TDP/DRAO/Swinburne Astronomy

Image Credit: SPDO/TDP/DRAO/Swinburne Astronomy

Choosing a single telecommunications protocol has always been difficult for engineers on Earth, so it’s especially difficult for those who want to communicate with beings from another star system. While it’s nice to imagine that extraterrestrial beings would be able to interface with whatever protocol humans decide to encode a message in, that’s not a realistic way to think. Humanity has developed countless electronic communication technologies since the 19th century. There’s no reason to believe that extraterrestrial beings haven’t done the same thing.

SETI and METI organizations have developed a single protocol for sending messages to potential examples of intelligent life. There’s no way of knowing if another civilization could ever actually interpret these signals but the odds are at least a little better with standardized systems.

Imagine an engineer trying to decode a data transmission that no one had ever encountered before. They’d probably try to compare it to other transmissions sent with the same protocol, and then look for the symbols that appear the most. These symbols are probably encoding the most common glyphs in the written language that the transmission represents.

Now imagine that each transmission that the engineer encounters is in a different code. There’s no way for them to compare different messages, because there aren’t any similarities between the different protocols. By using a single system, Earthlings are giving extraterrestrial cultures a chance to decode messages by comparing them to one another. It wouldn’t have been possible for international communications to be achieved on Earth if everyone decided to use their own technology standards.

In fact, poor choices in the past have hampered many types of technological developments. If standardization had occurred between Earthbound transmission sites years ago, these problems would never have reared their ugly head. For that matter, extraterrestrials might very well have been able to intercept numerous types of incidental transmissions. If signals are as weak as one might expect them to be, every little bit matters when we’re talking about communicating across the universe.

If standardization is important, the types of signals sent are equally important (if not more so). Most scientists agree that radio waves are the best way to communicate with other planets/stars given our current level of knowledge. This is due to the fact that radio waves are able to traverse the vast distances involved in actually reaching other stars/planets outside the Milky Way galaxy. Even the closest stars are about 6 light-years away (each light-year is roughly 6 trillion miles). This means that any signals we send their way have to cut through enormous amounts of gas and other obstructions found in space. Radio waves are able to do this effectively (as opposed to say, lightwaves) while traveling vast distances at the speed of light. I have read the work of some scientists that believe lasers may be a good way to reach extraterrestrials as well. I personally feel this is a great alternative to microwaves alone.


While standardization and appropriate signal types are invaluable, they’re also practical because they help to reduce costs. While practicality isn’t something that most people like to discuss, it’s actually pretty necessary in the world of SETI/METI. Many of these organizations, such as the SETI Institute (SETI Institute listens for signals vs. transmitting signals), survive on public donations. They need to maximize what they get out of the financial resources that they’re given to work with. Developing a single standard algorithm helps to reduce the amount of money spent on research while maximizing the chances of success (choosing the right type of signal to send) are crucial to long-term survival. It also means that different pieces of equipment will always interface properly. This means that expensive converts/integrations won’t ever be necessary as long as everyone adheres to the existing standard.

From an engineering standpoint, these groups might want to look at their antennas and transmission sites next (in terms of standardization). Once protocols are standardized, they can begin to improve in other areas as well. Each little bit matters when trying to talk to someone that may exist on a planet that is trillions of miles away.


Atri, D., DeMarines, J., & Haqq-Misra, J. (2011). A protocol for messaging to extraterrestrial intelligence Space Policy, 27 (3), 165-169 DOI: 10.1016/j.spacepol.2011.01.001

Edmondson, W. (2010). Targets and SETI: Shared motivations, life signatures and asymmetric SETI Acta Astronautica, 67 (11-12), 1410-1418 DOI: 10.1016/j.actaastro.2010.01.017

Will We Ever Really Travel to the Stars?

Image Credit: Paramount

Image Credit: Paramount

Interstellar space travel is one of the most common themes of science fiction, but the question is, will it ever become reality?

With our current understanding of physics, propulsion methods and the limits of our technology, there is currently no practical way to travel to other stars and solar systems. NASA terminated its Breakthrough Propulsion Physics Program in 2003, stating that no further breakthroughs appeared to be imminent. What this ultimately means is that we should not be expecting to see travel to other stars become reality any time soon, if ever. NASA did recently announce that they will begin work on a Warp Drive…whether anything will come of that, only time will tell. I personally would like to see this happen in the private-sector but that’s certainly unlikely for the immediate future.

In most sci-fi stories, starships zip around the galaxy at speeds far exceeding that of light, the universal speed limit of roughly 186,000 miles per second. The problem however is that the laws of physics state that absolutely nothing in the universe can travel faster than this (even though folks are trying to prove otherwise).

The Primary Issue – Distance

We know our own star simply as the Sun. The Sun is a star no different to billions of others in the Milky Way galaxy. To provide some important figures for reference, the Sun lies 93 million miles from away from Earth and it takes light eight minutes and twenty seconds to reach us.

Source: NASA

Source: R. Mewaldt & P. Liewer, JPL

The nearest star to Earth, other than the Sun, is Proxima Centauri of the Alpha Centauri triple-star system. It lies 4.24 light-years away, meaning that it takes 4.24 years for the star’s light to reach us.

The fastest launch speed achieved by mankind was that of the New Horizons robotic spacecraft which was launched at 36,373 miles per hour on its mission to the dwarf planet Pluto. The fastest man-made object is currently the Helios 2 solar space probe, travelling at 157,100 miles per hour. This speed was achieved by using gravitational assistance from the Sun. If the Helios 2 solar probe were to be sent directly towards Proxima Centauri, it would reach the star in approximately 18,000 years.

How Fast Can We Go?

There are technologies that exist which can achieve far greater speeds than those of space probes like Helios 2 or New Horizons.

One of these is nuclear pulse propulsion which basically uses nuclear explosions to power a rocket to incredibly high speeds. It seems plausible that such a spacecraft could reach speeds of around 5 percent of the speed of light, yet this would still take about 85 years to reach the nearest star. As demonstrated by the Project Orion effort of the mid-twentieth century, it is possible using only currently available technology. Of course, this speed is still too low, making it highly impractical. It is generally considered that, if a journey cannot be completed in considerably less than a human lifetime, it should not be started at all.

The only thing that is possible is to send out radio waves, traveling at the speed of light, to the stars. This allows us to send a message to Proxima Centauri for example, which would arrive in 4.24 years. Perhaps some day we will be able to send physical objects there at this rate.

Faster-than-Light (FTL)

Image Source: Nextbigfuture

Image Source: Nextbigfuture

Nothing can travel faster than light, as dictated by Einstein’s theories on relativity. Roughly 186,000 miles per second is the absolute speed limit. If practical interstellar travel is ever to become a possibility, we need to find a way around this speed limit.

To get around the FTL issue, sci-fi shows/movies/books often use things like warp drives that are capable of warping spacetime in such a way that it folds space. If this were possible, it would effectively enable FTL travel between two points. The Alcubierre drive, proposed in 1994, is the only serious attempt at theorizing a starship which travels faster than light. It does this by expanding space behind it and contracting space before it. The spacecraft travels in its own bubble at speeds slower than light. To put this in perspective, imagine a piece of paper with a point marked at each end. The shortest distance between these two points is a straight line, unless you fold the paper in half so that the two points meet each other directly.

The Alcubierre drive is highly theoretical and has one deal-breaking flaw – it requires something called exotic matter with negative mass, and this isn’t even known to exist.

The Bottom Line

Space Travel ConceptIf you could go back in time to the mid-nineteenth century and tell people that humanity was going to land on the moon in 1969, they would probably laugh at you. Since then, we have launched probes all over the Solar System and landed robotic spacecraft on the surfaces of Venus, Mars and Saturn’s moon, Titan. One thing is clear: Humanity’s potential is immense and science and technology are full of surprises. Interstellar travel may seem like a very long way off, but it will never become a reality if we don’t try.

One thing that is preventing many scientists from taking interstellar travel seriously is also the fact that we don’t really know where to start. There are countless stars out there, but until something truly interesting and worth visiting shows up, interstellar travel will remain a thing of science fiction. That being said, more than 850 planets have been discovered orbiting other stars and more are being confirmed every week. We are now learning that every star “up there” likely has a number of planets rotating around them (the same thing that happens in our neck of the universe). That’s a very, very large number of planets. It is likely just a matter of time before we find an Earth-like world out there in the lonely depths of space. Perhaps that will truly give humanity something to aim for resulting in a renewed interest in reaching the stars.


Ford, L., & Roman, T. (2000). Negative Energy, Wormholes and Warp Drive Scientific American, 282 (1), 46-53 DOI: 10.1038/scientificamerican0100-46

Hill, J., & Cox, B. (2012). Einstein’s special relativity beyond the speed of light Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 468 (2148), 4174-4192 DOI: 10.1098/rspa.2012.0340

González-Díaz, P. (2000). Warp drive space-time Physical Review D, 62 (4) DOI: 10.1103/PhysRevD.62.044005

Hansson, A. (2003). Project Orion: The Atomic Spaceship 1957–1965 Space Policy, 19 (2), 149-150 DOI: 10.1016/S0265-9646(03)00011-0

Endl, M., & Kürster, M. (2008). Toward detection of terrestrial planets in the habitable zone of our closest neighbor: proxima Centauri Astronomy and Astrophysics, 488 (3), 1149-1153 DOI: 10.1051/0004-6361:200810058

Herschel and Keck take Census of the Invisible Universe

Image Credits: ESA–C. Carreau/C. Casey (University of Hawai’i); COSMOS field: ESA/Herschel/SPIRE/HerMES Key Programme; Hubble images: NASA, ESA

By combining the observing powers of ESA’s Herschel space observatory and the ground-based Keck telescopes, astronomers have characterised hundreds of previously unseen starburst galaxies, revealing extraordinary high star-formation rates across the history of the Universe. Read More →

Capturing the Stars [Product Review]

Fans of the Siebert Monocentric ID series of eyepieces certainly have a lot to fall in love with. Since they have a wider and flatter field of view, they tend to be much easier to look into. The manufacturer claims that they are color corrected at 100 percent across their field of view. While they might not be quite as perfect as the company claims, they really do turn those globular clusters into a thing of beauty.

Amateur astronomers with driven mounts will find the Siebert Monocentric ID design to be more attractive than those with traditional telescopes. Several off-axis aberrations in the eyepiece are caused by the fast focal ratio scopes. This means that individuals who stick to using regular systems won’t be able to keep objects on-axis very easily. Anyone with a motor should fawn over the Siebert optics, however.

While it might not be the best design for individuals who don’t care to put work into their viewing sessions, this Siebert model will produce impressive details for those who are ready to experiment. Siebert eyepieces have a homemade appearance that illustrates the fact that they’re made by a small company. One might say that astronomers make them for their fellow astronomers.