Tag Archives: astronomy

161. The Month Ramadan

Welcome to Ramadan.

What does a month of religious observations, in what is very much a minority religion in America, have to do with a blog which is largely about science fiction? A great deal, as it turns out.

Beyond simple humanity, an interest in those whose view of the universe is not identical to most Americans, and a sense of fairness that impels us to look at Islam as a full fledged way of life, there are also non-religious, even scientific aspects of this season. When you realize that Ramadan cycles around the year, it becomes apparent that there is a lot of astronomy behind this month of observance.

So first, what is a month?

A month is the time it takes for the moon to orbit once around the Earth – oh, if it were only that simple.

For a start, science recognizes five kinds of months. A sidereal month of 27.3 days and the tropical month, also of 27.3 days, refer to one passage past a “fixed star” and an equinox point respectively. An anomalistic month is the time from perigee to perigee, 27.5 days, and a draconic month is the time from a node to the same node, about 27.2 days. A node is a point where the plane of the moon’s orbit crosses the plane of the Earth’s orbit.

Astronomy was not one of my fields of study. Every time I look up something like this my head spins, but no wonder. Everything in astronomy consists of measuring moving objects in reference to other moving objects.

The synodic (aka normal) month is the only one non-astronomers worry about. At 29 and a half days, it is the time it takes to go through one cycle of new to new moon. It is a little over two days longer than the others because it also includes chasing the Earth through roughly one twelfth of its orbit.

If that wasn’t complicated enough, none of the months come out in a even number of days and none of them divide evenly into the length of a year. If we were using a lunar calendar, as Muslims do in their religious life, our months would cycle around the calendar and only appear in the same season every (?) years. I didn’t give you a number there, because there are dozens of varieties of lunar calendar.

That works fine for religious observances, and it worked fine in the Arabian desert where the Islamic calendar got its start, but it doesn’t work in a globally connected world or in agricultural societies. You need to plant or harvest during the same month each year, and you need a common calendar to schedule happenings outside your area.

Non-Muslims who know anything about Ramadan, know that it is a month of fasting. It is more than that, and of course it doesn’t mean no one eats for a month. Fasting takes place during the daylight hours. A meal is taken just before sunrise, and another just after sunset, and fasting is not required of the ill, pregnant women, children below a certain age – there is a list, although it varies by sect.

In the mid-latitudes, when Ramadan falls during winter, the fasting hours are short; when it falls in summer, fasting if more arduous. There are special rules for those who live near the Arctic and Antarctic circles, otherwise they would have to fast nearly twenty four hours of each day when Ramadan falls in the land of the midnight sun.

111. Our Neighborhood in Fiction

Gordon Dickson’s list of works is huge, but for some of us they all boil down to the Childe Cycle, known to us mortals as the Dorsai books. At some future date I plan a series of posts in appreciation of them, but for now the issue is his use of the local stellar neighborhood.

Dickson provided us with fifteen extrasolar planets circling seven nearby stars. His primary interest wasn’t in planet building, but he had an ability to paint a planet with a broad brush, then close in and give telling details about those local scenes where the action was taking place. It worked; it was just enough world building to carry each story forward.

Since the Childe Cycle consumed twelve novels over forty-seven years, there was plenty of time to visit each world at some time during the series. Some of the worlds, the Dorsai world in particular, were instrumental in shaping the character of the actors, but for the most part, Dickson’s focus was on a larger issue.

Even though the Childe Cycle featured a form of FTL almost from the first, Dickson’s characters never ventured beyond the local neighborhood. The overarching story he was telling concerned man’s early venturing into space, which led to the formation of three splinter cultures, and the semi-mystical forces which were attempting to reintegrate them into the mainstream.

(Yes, Dorsai Irregulars, I know that is an inadequate rendering, but you try putting fifty years of another man’s sophisticated thoughts into one sentence.)

The Friendlies (religious fanatics or men of faith, depending on who was writing the description, and not really that friendly at all) inhabited the planets Harmony and Association under Epsilon Eridani. The Exotics (scientists of the mind, following a believable mash-up of psychology and zen) inhabited Mara and Kultis under Procyon. Dorsai, the warrior world, lay under Fomalhaut. Incidentally, the phrase under (a star’s name) was one Dickson used often. I find it charming, and presume he was exporting to the stars the notion that there is “nothing new under the sun”.

The rest of his planets were well thought out and inhabited by humans who were not of one of the splinter cultures.

Wikipedia has a nice summary of the Childe Cycle, including a full list of Dickson’s planets. Better still go to your used bookstore and start reading.


At the risk of arrogance – a risk any author is always willing to take – I’ll add my own fictional view of the local neighborhood.

My first science fiction novel, Jandrax, used a sabotaged FTL drive to set things in motion, stranding a group of colonists on an unknown planet. The only thing they – or I –  knew about their location was that it was far beyond the limits of exploration, and that none of them were ever going to return.

Cyan was going to be different. I wanted it to exploit the plot possibilities of relativistic flight, and to be a part of the exploration of the local neighborhood. I worked out this backstory as I wrote:

Early in this century, science makes a discovery that allows total conversion of matter to energy, providing the power to reach the stars at relativistic speeds. A multi-ship expedition to Alpha Centauri finds that the planet around Alpha Centauri A which should have been in the habitable zone, actually has an orbit so erratic that it is alternatively fried and frozen. However there is a barely habitable planet circling Alpha Centauri B. They name it Cinder and begin limited colonization.

Every novel of my childhood found an Earth-like planet around Alpha Centauri A; I had to break the pattern.

The second expedition, to Sirius, finds an Earth sized planet in a reasonable orbit for life, but this time the planet Stormking has a Uranian inclination. There is life, but it is basically uninhabitable. This sets up a future novel with an orbiting civilization made up of refugees from the inhabitants of Earth’s asteroid belt. They have chosen Sirius because it doesn’t have a habitable planet. They use Stormking as a prison, which set up the moral basis of the plot.

Three third-generations starships are built in orbit. The first two set out, one for Epsilon Eridani and one for Tau Ceti. A year later, the third set out for Procyon. This is the voyage which is the focus of the novel Cyan. When the explorers return to Earth, they find that the other two expeditions have both found prime planets, Haven and Elysium. Preparations to colonize them are taking all Earth’s resources; Cyan is not to be colonized, which sets up the events of the second half of the novel.

The starship which carried explorers to Cyan now goes on with a new crew to explore Epsilon Indi, before events which I can’t (spoiler alert) tell you about bring this stage of human exploration to a close.

Check out Cyan, due for release in a month or so, for details.

110. Our Stellar Neighborhood (post 2)

In the science fiction books of my youth, no one ever mentioned heading out into the universe already knowing what planets would be circling the stars they would visit. Even when I began Cyan, no one was thinking like that, so the first thing my explorers do is to map Procyon’s solar system and discover the eponymous planet which they will explore.

Alpha Centauri A is a near twin of our sun, as well as the closest to us. It used to be logical to assume that we will visit there first. That is no longer true. By the time we find the breakthroughs that will allow even relativistic speeds, we will probably have a full inventory of the nearby cosmos, and our first star journeys are likely to be to relatively well known destinations.

I really hate that. What fun would Columbus have had, if he had seen the National Geographic special first?

Where were we? Ah, the neighborhood.

Ignoring the various stellar specks out there, these are the stars we might have interest in, in order of closeness to Earth.

Alpha Centauri – luminosity 1.0 – 4.4 light years from Earth – already covered yesterday.

Sirius – luminosity 23.0 – 8.6 light years from Earth – is the brightest star in the night sky, as seen from Earth, due both to its inherent brightness and to its closeness to us. Sirius is a binary star. Sirius A is extremely bright and hot; Sirius B is a white dwarf.

Epsilon Eridani – luminosity 0.25 -10.5 light years from Earth – is the closest star which has a reasonably well confirmed planet, a giant thought to be about 3.4 AUs out. An AU (astronomical unit) is the distance from the Earth to the Sun, making it ideal for a quick mental picture of distance. The presence of a giant planet at that distance leaves us free to postulate smaller, more human-friendly planets closer in.

Procyon – luminosity 5.8 – 11.4 light years from Earth – is another binary. Procyon A is hot and white (but nowhere nearly as bright at Sirius) with an even fainter white dwarf companion, Procyon B.

Epsilon Indi – luminosity 0.12 – 11.8 light years from Earth – has three-fourths the mass of the sun and a much lower luminosity. Any human-habitable planets would be close in, with a very short year. If it has a decent tilt, its seasons could go by quite rapidly, leading to interesting story possibilities.

Tau Ceti – luminosity 0.36 (newer figures suggest .55) – 11.8 light years from Earth – Tau Ceti is a slightly smaller Sol type star. It is the nearest single star to so resemble our sun.

When I worked out the backstory for Cyan, I only considered stars within 5 parsecs; I will add two more to this list because Gordon Dickson used them in his version of the neighborhood, which we will see in tomorrow’s post.

Altair – luminosity 11 – 16.7 light years from Earth – is a slightly variable blue white star with a rapid rotation (about 9 hours, compared to the sun’s 25 days) which gives a pronounced equatorial bulge.

Fomalhaut – luminosity 16.6 – 25 light years from Earth – is also blue-white with one known planet called Dagon. The size, nature and composition of Dagon is highly controversial, but it seems to be visible to the Hubble telescope only because it is surrounded by a dust cloud many times larger in diameter than the planet itself.

109. Our Stellar Neighborhood (post 1)

FTL is the break point of science fiction. Without a faster than light drive, exploration is restricted to the local area, and that’s fine with me. I take satisfaction in building planets within the constraints of known stars. But beware, the party is nearly over. We now have the capacity to discover extrasolar planets, and new ones are found every year. Fortunately for latecomers to the planet builders guild, megaplanets are easier to find that Earth sized ones, and NASA keeps cutting funding. Still, it won’t be too many years before you can’t decide for yourself where, within the limits of orbital mechanics, you want the planets of Alpha Centauri or Procyon to be.

When I began world building, the prime reference was How to Build a Planet by Poul Anderson. I also had an article from Sky and Telescope titled Stars Nearer than Five Parsecs. Today the internet provides an embarrassment of riches, including planet building apps. Apps? Where’s the fun in that?

What I am about to present will be old knowledge to some of you, so forgive me. Not everybody can be a nerd on everything. There are plenty of people, including would-be science fiction writers, who only want a primer on the local neighborhood, because their passions lie elsewhere.

What is the star closest to Earth? The sun. That’s a gotcha riddle among middle school students. The sun’s luminosity is generally given as 1.0, which makes the luminosities of other stars easy to understand by simple comparison.

Okay, what star is next closest, Alpha Centauri or Proxima Centauri? The P- word gives it away, but it isn’t really that simple.

Alpha Centauri isn’t a star, it only seems to be one to the naked eye. A moderate telescope resolves that dot in the sky into three dots. Alpha Centauri is a triple star, or maybe  a double star with a third star wandering through the area. Astronomers haven’t decided yet.

Alpha Centauri is the largest “star” in the constellation Centaurus. Centaurus has moved southward since the ancients named it, so that Alpha Centauri is no longer visible from the northern hemisphere. I had to wait decades to see it, on my first trip to Australia. There you don’t look for Centaurus, you look for the Southern Cross, a kite shaped constellation within Centaurus.

Alpha Centauri is just a dot in the sky, but I was thrilled to finally see the star which was the setting for so many science fiction stories from my youth.

The two stars of the binary pair are named Alpha Centauri A and Alpha Centauri B. The third star is sometimes called Alpha Centauri C, but more often Proxima Centauri because it it slightly closer to Earth. Beta Centauri is something entirely different. The second brightest dot in Centaurus, Beta Centauri is a star system 525 light years from Earth – not in the local neighborhood at all. Beginners sometimes say Beta Centauri when they should be saying Alpha Centauri B.

The naming convention is widespread, but not universal. Many stars have names given to them by the ancients. Many more are simply alpha-numeric designations, following the conventions of published star charts or inventories by observatories.


Click here for a Wikipedia article that will list 56 of the nearest stars, followed by maps. The first map will give you some idea of where these stars lie in relation to each other.

Tomorrow we can look at some of the rest of the nearby stars, concentrating on those which might have planets useful for human real estate.