CONJUNCTION

GREAT CONJUNCTION:
      A great conjunction in the east south east sky tonight. Perfect visibility here in Winnipeg with Jupiter slightly to the left and above the waxing Moon. Gotta get out there with binoculars, 41 below windchill or not.
Frozen but happy in Winnipeg.

AMATEUR ASTRONOMY:
THE BLUE MOON THAT ENDS THE DECADE:
Tonight, as the decade ends, we will have the unusual event of a "blue moon" to ring out the old year. The term doesn't actually refer to the moon appearing blue in colour, though this can occur given certain atmospheric conditions. If there is sufficient dust in the air then light of a longer wavelength, ie red, is scattered away from the eyes of the observer, and the light that gets through is shifted to the blue end of the spectrum. this sort of lunar colouration was most prominent after the explosion of Krakatoa in 1883, but it also occurred in the 1950s after large forest fires in Canada and Sweden. It was also reported after the eruption of Mount Pinatubo in the Philippines in 1991, and there were even reports of "blue suns" in that year (see here). I do not recall it being so, and neither do I recall any change in the colour of the Moon after this year's extensive forest fires in BC. I do recall being able to spot the atmospheric haze after the eruption at Mount St. Helen's in 1980. Does anyone else have any memories or references ?

The origin of the phrase "blue moon" event goes as far back as 1528 when it was used in an anti-clerical English pamphlet entitled "Rede Me and Be Not Wrothe" where the author mocks the clergy saying that, if they declared the moon to be blue then they would expect others to believe it. The use of the term to describe a rare event, as in "once in a blue Moon", dates from 1824 (see here). There is some dispute about the origin of the term in relation to an "extra moon". Some say that the Old Farmer's Almanac began to use the term to refer to an extra full moon in a season in the 1800s, while others claim that the Farmers' Almanac didn't begin using the term this way until the 1930s. In any case the usage of the term as referring to two full moons in a month is of even more recent vintage. It's generally accepted that this way of using the phrase began in 1946 when a writer for Sky and Telescope Magazine misinterpreted the Farmers' Almanac rule of an extra moon in a season as being an extra moon in a month. For more on the history of the term see the Wikipedia article on blue moons.




Today's (tonight's) blue Moon takes place at 19:13 UT. Here in the Central time Zone this translates as 13:13. We obviously can't observe the exact instant of the Moon's fullness here in Manitoba at a little after 1:00 in the afternoon. In Australia and East Asia the event doesn't actually occur until tomorrow, January 1, and it is January rather than December that will have a 'blue Moon' there. The actual "blue Moon" will, however, be the second full Moon of January, not the first. The time of an "exact" full Moon is, of course, an instant rather than a night in duration. If you wish to find the exact time of the full moon and to convert it to your own local time consult the Time and Date.Com site where there is a wealth of other information such as sunrise/sunset and moonrise/moonset data. For those who would like a visual representation of the Moon's phases I could suggest the Moon Phase Calender at the Moon Connection site. A "blue Moon" in the sense of a second full Moon in a month occurs about once every 2.72 years.




There is also a partial eclipse of the Moon visible in Australia, Asia, Europe and Africa tonight, though it is not visible in the western hemisphere. This event has already passed , as maximum totality happened at 19;23 UT.



For those interested in matters lunar a couple of years ago Molly featured a series of articles that were a "leisurely cruise" through the various most prominent visible features of the Moon. If you're interested just type the item that you might want to read about (such as 'Mare Criseum', sea of Tranquility, etc..) in the search function of this blog and read all about it. See you in the New Year. It's been an interesting year and an interesting decade.

AMATEUR ASTRONOMY:

THE CATALOG OF EXOPLANETS:

Here's an interesting item that Molly just received today in her inbox from the Planetary Society. In the past few years the number of planets found orbiting stars other than our Sun has blossomed into a list of hundreds, and yet more are due to be discovered. If you are interested the Planetary Society has set up a Catalog of Exoplanets to keep track of the discoveries- and also to explain more about the science behind them. Here's the announcement.

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Catalog of Exoplanets:

Ever since the first exoplanet was discovered in the mid-1990s, we’ve had an explosion of discoveries, revealing hundreds of strange worlds orbiting faraway stars. Slowly but surely, as detection techniques improve, scientists are closing in on the exoplanet we are all waiting for: a world like our own, a distant "Earth" orbiting an alien star.

In order to share with you all that has been found to date, The Planetary Society -- with support from our members -- created the Catalog of Exoplanets. Here you will find a regularly updated database of all known exoplanets.

Our catalog is designed with resources for every level of study whether you are a professional, amateur, teacher, student, or simply want to find out what the buzz is about the latest exoplanet discovery.

Find essential information about each exoplanet, such as...

**What is the planet's location and home star?
**What is its mass, and how does it compare to planets in our own solar system?
**How long does it take it to complete each orbit ?
**How was it detected?
**When was it discovered?
**How many other known planets are orbiting its star?

Each planet can be seen in a dynamic animation showing the planet in its orbit around its star as well as the orbits of any other known planets in the system. For example, one animation below shows a sample exoplanet system (GJ 876) and one shows the outer planets in our solar system (Jupiter through Neptune; the inner planets would be too hard to see on the same scale).
Explanation of Animations

And there is more, find out about...

**The different methods used to detect exoplanets.
**Advantages and shortcomings of each detection method.
**Notable exoplanets, those that stand out from the crowd.

The idea for this catalog started when The Planetary Society funded the planet hunting group of Geoff Marcy at UC Berkeley, Paul Butler of the Carnegie Institution, Steven Vogt and Debra Fischer of San Francisco State University to analyze years of data and publish updated parameters such as planetary mass for a whole host of exoplanets. Their results were published by Butler et al. in the Astrophysical Journal, targeted at professional astronomers, and covering a subset of exoplanets. In creating our online catalog, The Planetary Society includes all known exoplanets in a manner intended to be friendly to students and the general public, as well as amateur and professional astronomers.
Enjoy learning about the search for distant worlds!

AMATEUR ASTRONOMY:

EVIDENCE FOR EARLY LIFE ON EARTH-ON THE MOON !!!:

The following is a thought provoking article from Space.Com.

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Bits of Ancient Earth Hidden on the Moon

By John Ruley

Some scientists believe that at least one meteorite found in Antarctica preserves evidence of ancient life on Mars. Now, work by a team of English scientists reinforces an earlier suggestion that evidence of life on the early Earth might be found in meteorites on the moon.

The original idea was presented in a 2002 paper by University of Washington astronomer John Armstrong, who suggested that material ejected from Earth during the Late Heavy Bombardment (a period about four billion years ago when the Earth was subjected to a rain of asteroids and comets) might be found on the moon.

Armstrong's suggestion was interesting, but whether a meteor ejected from the Earth might arrive intact on the moon remained an open question.

New research by a team under Ian Crawford and Emily Baldwin of the Birkbeck College School of Earth Sciences used more sophisticated means to simulate the pressures any such terrestrial meteorites might have experienced during their arrival on the lunar surface. This confirmed Armstrong's hypothesis. In many cases, the pressures could be low enough to permit the survival of biological markers, making the lunar surface a good place to look for evidence of early terrestrial life.

Any such markers are unlikely to remain on Earth, where they would have been erased long ago by more than three billion years of volcanic activity, later meteor impacts, or simple erosion by wind and rain.
Crash landings
Given that material from early Mars has been found in meteorites on Earth, it certainly seems reasonable that material from the early Earth could be found on the moon. Indeed, Armstrong's paper estimated that tens of thousands of tons of terrestrial meteorites may have arrived there during the Late Heavy Bombardment.

However, there is a problem: The moon lacks any appreciable atmosphere. Meteorites arriving on Earth are decelerated by passing through our atmosphere. As a result, while the surface of the meteorite may melt, the interior is often preserved intact. Could a meteorite from Earth survive a high-velocity impact on the lunar surface?

Crawford and Baldwin's analysis, based on commercially available software called AUTDYN, used finite element analysis to simulate the behavior of two different types of meteors impacting the lunar surface.

Armstrong's group performed a crude calculation indicating that pressures experienced by a terrestrial meteorite arriving on the moon probably would not be enough to melt it. Crawford and Baldwin's group simulated their meteors as cubes, and calculated pressures at 500 points on the surface of the cube as it impacted the lunar surface at a wide range of impact angles and velocities.

In the most extreme case they tested (vertical impact at a speed of some 11,180 mph, or 5 kilometers per second), Crawford reports that "some portions" of the simulated meteorite would have melted, but "the bulk of the projectile, and especially the trailing half, was subjected to much lower pressures."

At impact velocities of 2.5 kilometers per second or less, "no part of the projectile even approached a peak pressure at which melting would be expected." He concludes that biomarkers ranging from the presence of organic carbon to "actual microfossils" could have survived the relatively low pressures experienced by the trailing edge of a large meteorite impacting the moon.
Hard to find
Finding terrestrial meteorites on the moon will be challenging. Crawford suggests that the key to finding terrestrial material is to look for water locked inside. Many minerals on Earth are formed in processes involving water, volcanic activity, or both. By contrast, the moon lacks both water and volcanoes.

Minerals formed in the presence of water, called hydrates, can be detected using infrared (IR) spectroscopy. Crawford and his co-authors believe that a high-resolution IR sensor in lunar orbit could be used to detect any large (over one meter) hydrate meteorites on the lunar surface, while a lunar rover with such a sensor "could search for smaller meteorites exposed at the surface."

Other planetary astronomers view the issue more conservatively. Dr. Mike Gaffey of the University of North Dakota Space Studies department argues that while "debris from a large terrestrial impact could have reached the moon ... it's highly unlikely that it would be in sufficient concentrations to be seen" using orbital instruments.

He believes that the meteorites would be shattered into small pieces by the impact, and then subjected to a form of lunar weathering due to the solar wind and a continuous rain of micro meteoroids that hit the moon. Instead, he suggests that any surviving material from Earth would be fractured into small pieces embedded in ancient lunar soils, some of which might be exposed at the surface by later meteor impacts.

Crawford concedes that point, and suggests that it might be necessary to dig below the surface to find terrestrial meteorites. He adds that collecting samples, observing them on the lunar surface, and picking those that warrant a return to Earth for detailed analysis "would be greatly facilitated by a human presence on the moon."

The last U.S. astronaut to set foot on the moon, Dr. Harrison Schmitt, was a geologist. If current NASA plans for a return to the moon later in this century are fulfilled, perhaps Dr. Schmitt's successors will search for hydrated rocks, which might unlock the mystery of how life began on the Earth.

HOLIDAYS:

WELCOME TO SUMMER !!!!

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HAPPY SUMMER SOLSTICE (AND MIDSUMMER YET TO COME):

Today was the day of the summer solstice in the northern hemisphere (winter solstice south of the equator). The term "solstice" may refer to either the exact time of the sun's furthest point away from the equator or it may refer to the day on which this occurs. In the first sense the solstice is already well past. It occurred at 23:59 UTC (Greenwich Mean Time). Here in Winnipeg this would have been at about 18:59 (ie 6:59 pm. If you are interested about when the event occurred in your locality look it up on the Time And Date.Com site. This site also provides information on such things as sunrise, sunset, phases of the moon and even weather.

The cause of the seasons, of which the solstices and equinoxes are the arbitrary dividing points, is the fact that the angle of rotation of the Earth is about 23.44 degrees from the perpendicular to its orbital path. It keeps this orientation throughout its orbit with the result that at any given time (except the equinoxes) one or the other hemisphere will be tilted towards the sun and hence be warmer than the other.

At the time of the northern solstice the sun appears to be directly overhead for all places 23.44 degrees north of the equator, known as the Tropic of Cancer, while during the southern solstice the same is true for any point 23.44 degrees south of the equator, known as the Tropic of Capricorn. The points in between this latitudes are known as the "tropics". The names for the tropics are actually misnomers as they stand for the constellations from ancient times when astrology was formulated. Due to precession the Sun is now in Taurus during the northern solstice and in Sagittarius during the southern one. The change of constellations makes the names more one of convenience than anything bearing any relation to reality.

The severity of seasonal change fluctuates over long time periods (thousands of years) because the axial tilt of the earth varies from 22.1 degrees to 24.5 degrees. The greater the tilt the more dramatic the seasonal changes.

In East Asia most calenders divide the year into 24 "solar terms". "Xiazhi" (Ha chi) is the 10th solar term. It begins when the sun reaches the celestial longitude(the highest point the sun reaches in the sky) of 90 degrees and ends when it reaches 105 degrees. Xiazhi literally translated is "summer solstice". In our calender this corresponds roughly to the period from June 21st to July 7th.

The time of the "northern sun" during the summer solstice can only be seen from places north of 66.56 degrees north, the Arctic Circle. At exactly this latitude the Sun touches the horizon at midnight but never truly sets. At the north pole the Sun would appear to rise and set in exactly the same place at the time of the solstice- in the south. But don't forget that all directions are south at the pole. The Sun would indeed appear to reverse course across the sky, but it wouldn't appear the same as if it did so at lower latitudes.

There are two interesting terms related to the twilight as one approaches the poles during midsummer. When one reaches latitude 50 degrees north the Sun never gets further than 16.56 degrees below the horizon. this is known as "astronomical twilight" when it is impossible for astronomers to do any work with any great precision. It is also called the "grey nights". Above 60 degrees latitude the Sun never gets more than 6.56 degrees away from the horizon at the summer solstice. This is known as "civil twilight" or "the white nights".

MIDSUMMER CELEBRATIONS:
Many traditional holidays clustered around the times of both the summer and winter solstices. The time of most of the summer festivals in western cultures, however, is no longer June 21st but rather June 24th. The difference is due to the calendar reform of Pope Gregory XIII. The old Julian calendar moved the date of the solstice forward about 3 days every four centuries. The Gregorian calendar, on the other hand, moves a little bit from year to year but only advances on the average a day for every 3,000 years. The old pagan solstice festivals had been Christianized as the Feast of St John the Baptist, and this day kept its separation from the actual solstice at the time of the Gregorian reform.

The Feast of St. John is unique is that it is celebrated on the presumed date of the Saint's birthday. All other saints' days are celebrated on the day of their presumed death. The Roman Catholic Church has declared St. John's day as "Solemnity", the highest designation of a feast day. For more on St. John the Baptist and his celebration see the article in the Catholic Encyclopedia. Many of the European customs that surround Midsummer Day derive from older pagan customs, but far less is known about these than many modern "mythologizers" imagine. The actual reconstruction of verifiable rather than fanciful knowledge about pagan European religions is rather austere and sparse compared to the free flights of fantasy engaged in by many people who imagine they are recreating said religions. It's doubtless true that there were midsummer bonfires and, in some countries, midsummer trees (like the Yule trees, the spring trees or the maypole at different times of the year). The Romans had the feast of the Vestalia when married women were allowed to enter the shrine of Vesta, Goddess of the Hearth, where only the vestal virgins were allowed to enter at other times. Yet, even for the names of ancient deities, let alone detailed accounts of the religious practices of preChristian Europeans there are few reliable sources, and these are vastly outnumbered by the endless tomes of pop-religion in the New Age sections of bookstores today. As a matter of fact you'll rarely find them on the shelves of any bookstore. Tacitus, Bede and Caesar simply don't have the "pizzazz" that modern carbonated pop-religion delivers.

The religious practices of Native Americans are known a little better, and some of their midsummer festivals have been described in much greater and more accurate detail than those of ancient Europe. Native Americans have also left perhaps even more stone structures (some are known as "medicine wheels") that are just as accurate astronomical calculators as the better known megalithic structures of Europe such as Stonehenge. As an interesting sidelight June 21st has been officially known as 'National Aboriginal Day' in Canada since 1996.

In France La Fete de Saint-Jean is a Catholic festival held in June 24th (midsummer) and features large bonfires. The first Canadian celebration took place in New France in 1638, according to the Jesuit Relations. Ludger Duvernay, the Quebecois editor of La Minerve began the campaign to have this day declared the official holiday of French Canada in 1834. Pope Pius X declared St. John the Baptist to be the official patron of French Canadians in 1908. June 24th became an official holiday in Quebec in 1925, and in 1977 it was renamed the National Holiday of Quebec, though it is still usually referred to as St Jean-Baptiste Day.

Midsummer festivals in Portugal are actually held at various times depending upon the area. Lisbon, for instance, celebrates it on St. Anthony's Day (June 13th), but other places hold to June 24th. In Brazil, however, June 24th is the universally celebrated day, and it has become much more popular there than back in Portugal. The "Festa Juanina" is particularly popular in northeastern Brazil, actually rivalling Carnival in popularity.Two cities in the northeast of the country, Caruara and Camina Grande, are in competition with each other for the title of "Biggest St. John's Festival in the World". Caruara presently holds the Guinness title.

In Ireland many towns hold midsummer festivals on the weekend nearest to the 24th. In Italy the day is particularly popular in Florence (lasting from June 21st to June 24th) as he is the patron saint of Florence. In Poland, especially in the north, midsummer is celebrated on June 23rd. It begins at 8:00pm and lasts all night. Traditionally wreaths were thrown into the Baltic or into rivers and lakes.

The name for St. John in Russia is Ivan Kupala. It is celebrated on June 23rd (Gregorian calendar) and July 6th (Julian calendar) in both Russia and Ukraine. As in Poland wreaths are thrown into bodies of water and bonfires were/are lit as well. Mussorgsky's 'Night on Bald Mountain' was actually inspired by Ivan Kupala day festivals rather than Halloween. Bonfires were also traditional in the Baltic countries of Latvia, Estonia, and Lithuania, despite Soviet disapproval in the case of the latter country. Wreaths in Latvia were worn rather than tossed into water. In Latvia this is known as the Feast of Jani. In Estonia bonfires are once more featured and the festival is very similar to that of Finland to the north (Estonian and Finnish are related languages). Finland also features the ever present bonfires and also a summer pole tradition borrowed from Sweden. Before the conversion to Christianity the day was known as Ukon juhla, after the Finnish god Ukko. The day is known as Juhannus in Finnish and "midsommer" for the Swedish minority in Finland.

I n Sweden Midsommarafton (Midsummer Eve) and Midsommardagan (Midsummer Day) are celebrated beginning on the Saturday that falls between June 20th and June 26th. It may rival Christmas in importance in this country. A "maypole" is raised on the Friday following the beginning of the festival , decorated with flowers and greenery, and dances are held around this pole. The years first potatoes,pickled herring sour cream and (hopefully) strawberries would be on the traditional menu. Old traditions about decorating houses and barns with greenery persist even though the old superstitions about this bringing luck are mostly forgotten. Midsummer in Sweden is considered the start of the summer holidays, something like the May long weekend in Canada and is a great time to party. In Norway the day called "Jonsok" or "Sankthansaften" is celebrated on June 23rd. Once more there is the midsummer bonfires.

The Danish name for St. John's Eve is "Sankt Hans aften", and it takes place on the evening of June 23rd. Once more it is time of bonfires and parties even though it is no longer an official holiday. Midsummer festivals in Great Britain gradually petered out during the Reformation and in subsequent centuries. Midsummer bonfires are still being lit in some places in Cornwall, however, and neo-pagans have their annual get together at Stonehenge, though, as previously mentioned, this has little connection with traditional midsummer festivals.

Sorta a great loss to Molly's point of view even if she has little sympathy with the necromancy of trying to revive that which is dead and dolling it up in the illusion that it is a recreation of the past. Better to create entirely new traditions without pretense.
Anyways, merry solstice and a happy midsummer.

AMATEUR ASTRONOMY:

THE RESURRECTION OF "PLANET X":

The search for planets beyond the traditional 6 visible planets has usually been guided by observations of gravitational anomalies. From the hypothetical Vulcan, supposedly orbiting between Mercury and the Sun and consigned to oblivion by Einstein's theory of relativity to the discovery of Neptune (1846) and Pluto (1930) this general picture has held true, even if the previous discovery of Uranus (first observation 1690 and description as a planet in 1781) was made by regular observation. Today the discovery of trans-Plutonian objects such as Sedna- relies more on regular observation once more. The long standing quest for "Planet X" has pretty well fallen by the wayside since the discovery of Pluto and the explaining of orbital anomalies that Pluto couldn't account for. The existence or non-existence of the presumed red or brown dwarf companion of the Sun nicknamed 'Nemesis' (because of its hypothetical role in mass extinctions) remains an open question. But now it seems that the quest for Planet X has opened up once again, not because of planetary orbitals but because of features of the Kuiper Belt in which Pluto and Sedna orbit. Here's the story from Space.Com. Keep on dreaming sci-fi fans.

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Large 'Planet X' May Lurk Beyond Pluto

An icy, unknown world might lurk in the distant reaches of our solar system beyond the orbit of Pluto, according to a new computer model.

The hidden world -- thought to be much bigger than Pluto based on the model -- could explain unusual features of the Kuiper Belt, a region of space beyond Neptune littered with icy and rocky bodies. Its existence would satisfy the long-held hopes and hypotheses for a "Planet X" envisioned by scientists and sci-fi buffs alike.

"Although the search for a distant planet in the solar system is old, it is far from over," said study team member Patryk Lykawka of Kobe University in Japan.

The model, created by Lykawka and Kobe University colleague Tadashi Mukai, is detailed in a recent issue of Astrophysical Journal.

If the new world is confirmed, it would not be technically a planet. Under a controversial new definition adopted by the International Astronomical Union (IAU) last week, it would instead be the largest known "plutoid."

The Kuiper Belt contains many peculiar features that can't be explained by standard solar system models. One is the highly irregular orbits of some of the belt's members.

The most famous is Sedna, a rocky object located three times farther from the sun than Pluto. Sedna takes 12,000 years to travel once around the Sun, and its orbit ranges from 80 to 100 astronomical units (AU). One AU is equal to the distance between the Earth and the Sun.

According to the model, Sedna and other Kuiper Belt oddities could be explained by a world 30 to 70 percent as massive as Earth orbiting between 100 AU and 200 AU from the sun.

At that distance, any water on the world's surface would be completely frozen. However, it might support a subsurface ocean like those suspected to exist on the moons Titan and Enceladus, said Mark Sykes, director of the Planetary Science Institute in Arizona.

"The interesting thing for me is the suggestion of the kinds of very interesting objects that may yet await discovery in the outer solar system," said Sykes, who was not involved in the study. "We are still scratching the edges of that region of the solar system, and I expect many surprises await us with the future deeper surveys."

ASTRONOMY:

DO WE HAVE A CLOSER NEIGHBOUR THAN WE THINK ?

It has long been famous that Alpha Centauri is our closest stellar neighbour. At 4.36 light years away this star system is the closest to our own system. Alpha Centauri, the brightest star in the southern constellation Centaurus is actually a triple star system, consisting of Alpha Centauri A and B and Proxima Centauri. While not visible in our northern hemisphere Alpha Centauri is famous as the outermost "pointer" to the Southern Cross. The closest part of this system, Proxima Centauri is only 4.22 light years away. Proxima is a red dwarf that orbits the primary A and B system. Alpha Centauri A is slightly larger and brighter than the Sun while B is slightly smaller and dimmer. The two orbit each other in a period of just under 80 years. See this wikipedia article for a fuller description of this system. This article also describes the possibility of Earth-like planets around the stars of this system.

What caught Molly's interest was a recent article in Space.Com on this system and the possibility of Earth-like planets so close to our neighbourhood. I reproduce the article below....

Nearest Star System Might Harbor Earth Twin

By Andrea Thompson

Earth may have a twin orbiting one of our nearest stellar neighbors, a new study suggests.
University of California, Santa Cruz graduate student Javiera Guedes used computer simulations of planet formation to show that terrestrial planets are likely to have formed around one of the stars in the Alpha Centauri star system, our closest stellar neighbors.

Guedes' model showed planets forming around the star Alpha Centauri B (its sister star, Proxima Centauri, is actually our nearest neighbor) in what is called the "habitable zone," or the region around a star where liquid water can exist on a planet's surface.
The model also showed that if such planets do in fact exist, we should be able to see them with a dedicated telescope.
"If they exist, we can observe them," Guedes said.
Guedes' study has been accepted for publication in the Astrophysical Journal.

A likely candidate
Astronomers have for some time pinned the Alpha Centauri system as one that was likely to form planets, said study co-author Gregory Laughlin, a UCSC professor.

"I think that there's been a good line of evidence over the past decade or so," Laughlin told SPACE.com.

Several factors mark the system, particularly Alpha Centauri B as friendly to planet formation, Laughlin said. The metallicity of Alpha Centauri B (or how much of its matter is made up of elements heavier than hydrogen and helium) is higher than our Sun's, so there would be plenty of heavier-mass material for planets to form from, he said.

Also, because the planet is a triple star system, the processes that form large Jupiter-mass gas giants, which account for most of the extrasolar planets found so far, would be suppressed. So it would be more likely for the system to produce terrestrial planets.

Laughlin also noted that a number of factors make Alpha Centauri B a good candidate for astronomers to actually detect an Earth-sized terrestrial planet.
Training telescopes
The Doppler detection method, which has revealed the majority of the 228 known extrasolar planets, measures shifts in the light from a star to detect the tiny wobble induced by the gravitational tug of an orbiting planet.

Because Alpha Centauri B is so bright and nearby, detecting a small terrestrial planet's minuscule wobble would be that much easier. Also, its position high in the sky of the Southern Hemisphere means it is observable for most of the year, just as the Big Dipper is observable for most of the year in the Northern Hemisphere.

According to Laughlin, five years of observations using a dedicated telescope would be needed to detect an Earth-like planet around Alpha Centauri B. If astronomers do dedicate substantial resources to detecting an Earth-like planet, this is the star to focus on, he added.

"We're advocating that there's a strong possibility a planet could be there," he said.

Other stars are thought to harbor Earth-like planets, and solar systems like ours are starting to be found. Astronomers announced last month the discovery of a solar system with striking similarities to ours.

If such a planet is found, spacecraft, such as the proposed Terrestrial Planet Finder, could be launched to find out more information about the world, such as whether or not it had water on its surface, Laughlin said.

Study co-author Debra Fischer of San Francisco State University is leading an observational program to intensively monitor Alpha Centauri A and B using the 1.5-meter telescope at the Cerro Tololo Inter-American Observatory in Chile. The researchers hope to detect real planets similar to the ones that emerged in the computer simulations.

"I think the planets are there, and it's worth a try to have a look," Laughlin said.

HOLIDAYS:

HAPPY CHINESE NEW YEAR !!!

Today is Chinese New Year, the most important festival in the Chinese calender. The year we are entering is the Year of the Rat, or , more properly, the year of the Earth Rat. Because the Chinese calender is a combined lunar/solar calender the length of each year doesn't correspond to that of the Gregorian calender. This year will last from Today until January 25, 2009 when we will enter the Year of the Earth Ox. The Chinese years, which occur in a cycle of 60 years are often named for a corresponding element (Earth, Metal, Water,Wood and Fire) and then with one of the 12 animals of the Zodiac with their corresponding Chinese names. These are as follows:

1)zi (rat)

2)chou (ox)

3)yin (tiger)

4)mao (hare,rabbit)

5)chen (dragon)

6)si (snake)

7)wu (horse)

8)wei (sheep)

9)shen (monkey)

10)you (rooster)

11)xu (dog)

12)hai (pig)

The Chinese signs of the Zodiac obviously don't correspond with those we know here in the West. As an interesting side note traditional Chinese astronomy recognized only 28 constellations. For more on Chinese astronomy see HERE. Because of the discrepancy between a lunar year and a solar year the Chinese calender uses "leap months" to reconcile the difference. A regular month has either 29 or 30 days. Every 2nd or third year a "leap month" is added. This has the same number as the preceding month. Thus it ends up that a "regular year may have either 353, 354 or 355 days. A leap year has either 383, 384 or 385 days.

There is some argument about exactly which year this is in the Chinese calender. The most popular theory is that it is year 4705. This stems from the idea that the calender was instituted by Emperor Huang Di in the 61st year of his reign (2637 BCE). Others date the calender from the first year of his reign (2697 BCE). Because these dates are exactly 60 years apart they make no difference in terms of the naming of the years.

CHINESE SEASONS:

The Chinese Zodiac is used only for calculating years and has no reference to the months of a year. In Chinese astronomy seasons begin and end not at the solstices and equinoxes but at the midway point between these msolar events (see diagram at the left). The months of the year are usually simply numbered, with zhengyue ("principal month") being the first, and the others simply following the numbers ie "eryue" (second month), "sanyue" (third month),etc.. They can alternatively be named partially after plants. The list is as follows:

1)First Month

2)Apricot blossoms

3)Peach blossoms

4)Mei ripens

5)Pomegrnate blossoms

6)Lotus blossoms

7)Orchid blossoms

8)Osmanthus blossoms

9)Chrysanthemum blossoms

10)Good month

11)Hiermal month

12)Last month

The celebrations of Chinese New Year begin today and continue on (for a variable amount of time depending on the country) until the Lantern Festival (this year on february 21). For the "days of Chinese New Years" and other information on thgis holiday season please see the archives at this blog for February 2007. Included there are 'Happy Chinese New Year' (Feb. 18/2007), 'The Days of Chinese New Years' (Feb. 19,2007) and 'More on Chinese New Years'(Feb. 24,2007). For a reference that shows you how to convert from Chinese to Gregorian calender dates see HERE.

Finally, here's the story of how the months got their names. Supposedly the animals were quarreling over who should get precedence in the naming of the 12 years of the cycle. The gods decided to hold a contest to determine the order. The animals lined up on a river bank, and their order in the calender would be determined by the order in which they swam to the other side. The cat was, understandably, disturbed by this contest because he feared water. The ox, meanwhile, wondered how he could find the other shores because he had poor eyesight. The sneaky rat suggested that he and the cat jump on the ox's back and guide him across. On thye way over the rat pushed the cat off into the water. Just as the ox was to come ashore the rat jumped off and became the first to reach the shore. Thus the first month was named after hi. The ox finished second. The lazy pig came in last. The cat finished too late to have any place in the calender. from this point forward the cat vowed to be the eternal enemy of the rat.

HARVEST MOON TODAY:

AND EQUILUX TOO:

Today is the day of this year's Harvest Moon. The exact time of the event is when the Moon reaches the spot in the sky where it is precisely opposite the Sun. This will occur at 19:45 Universal/Greenwich time today (7:45 pm). This will be 14:45 (2:45 pm) here in Central Daylight Time. To find the timing for your own time zone see the Time and Date website.

All of the full moons of the year have popular names that differ from place to place. See HERE, HERE and HERE for three different lists. Other names for the Harvest Moon include the Wine Moon, the Singing Moon, the barley Moon, the Fruit Moon and the Elk Call Moon.

The Harvest Moon is the most common name. The Harvest Moon is defined as the full moon that falls closest to the Fall Equinox which occurred three days ago on September 23rd. This moon can actually occur earlier than the equinox, and in about one year out of four it occurs in October. This happened last year but will not occur again until 2011.

The popular belief that the Harvest Moon stays in the sky longer than other full moons is false. But farmers traditionally did have more time to work by moonlight at this time of year. This is because of the variation in time of moonrise from day to day as the seasons change. Usually the Moon rises about 50 minutes later each day. When the Moon is, however, travelling in the sky near the path of the ecliptic, as it does in September, October and November, the day-to-day difference is foreshortened. The effect depends upon latitude. The further north you are the shorter the daily difference between moonrises. In Miami, for instance, the Moon rises an average of 37 minutes later from day to day at this time of year. At the latitude of Edmonton, Alberta, however, the average difference is only 12 minutes. This meant that on successive nights during the harvest season that farmers would indeed have more time to work the fields by moonlight on each day of the harvest. The same is true for the next moon of the year, usually known as the Hunter's Moon. In the southern hemisphere the situation is reversed, and the Moon rises more than 50 minutes later from day to day at this time of year.

The Harvest Moon is also neither brighter nor of a different colour than other full moons of the year. People who go out early to observe moonrise around the time of the Harvest Moon may be fooled by what is known as the 'Moon Illusion' into thinking that the Harvest Moon is bigger. Any moon, or any other sky object for that matter, always looks bigger when it is near the horizon. This is despite the fact that it occupies exactly the same angular diameter in the sky. The difference in size is a trick of perception rather than any real physical effect. Similarly the rising Harvest Moon is no redder than any other rising Moon. Refraction of light due to Earth's atmosphere gives all objects near the horizon a reddish hue. Think of the rising or setting Sun.

As mentioned previously on Molly's Blog (See 'Welcome to Autumn' last weekend) today is also the day of the equilux. This is the time when daylight and nighttime are most exactly equal. There will be another such day next spring. Til then...

WELCOME TO FALL:

THE AUTUMNAL EQUINOX:

Tomorrow morning at 4:51 am CDT (9:51 UT) the fall equinox will arrive.You can convert this to your own time zone using the Time and Date site. The equinox is defined as the time when the Sun is directly above the Earth's equator. This usually occurs around March 20th (the Vernal Equinox) and September 22nd (the Autumnal Equinox). At this time the Sun crosses celestial equator. The equinox is also the time of year when the celestial equator intersects with the ecliptic. The equinox is a point in time, not the name of a day. The day when daylight and nighttime are "most nearly equal" is referred to as the Equilux. while the equinox falls on September 23rd this year the equilux will actually be September 26th.

The time of the equinox isn't fixed. Each year they fall about 6 hours later. This is partially corrected by the leap year every four years which resets the time of the event. The reset isn't perfect however, and there is a slow drift of the time of the equinoxes (and solstices) to earlier times in the year. The shift amounts to a full day over the course of about 70 years. This shift is largely compensated by the century leap year rule of the Gregorian calender.

As we approach the equinox the rate of change in the length of a day increases. If you follow the time periods of daylight you will notice that they change most slowly around the times of the solstices but change most rapidly at the equinoxes. At the poles this means that the rate of change is instantaneous. The equinox marks the transition from 24 hrs sunlight to 24 hrs darkness. The further you travel from the poles the slower the rate of change. At the equator the rate of change is mere seconds per day. This apparent "midnight sun" in its full effect can be seen up to 100 kms from the poles. The time from the solstice in June to the September equinox is 94 days. The time from the December solstice to the March/Vernal equinox is only 89 days. This discrepancy arises because the orbit of the Earth is elliptic rather than perfectly circular. This means that the rate at which the Earth orbits the Sun also varies. It is faster towards the spring(northern hemisphere) when the Earth is closer to the Sun.

The actual times of daylight and night are not equal at the time of the equinox. This is not just because the equinox is a point in time. It is also due to other factors that contribute to the day being longer than the night at this time of year. First of all, the Sun is not a point source of light. It is a disc, and sunrise and sunset are defined from the point of view of the upper edge of the disc. The discrepancy is at least a minute on both ends of the day. There is also the effect of light refraction when the Sun is near the horizon. This makes the Sun seem to be a little bit more above the horizon at both sunrise and sunset. This effect adds almost seven minutes to the daylight. If you take twilight into account the "day" at the time of the Equinox would be almost an hour longer than the night. As you go towards the poles this difference increases, and the time of the equinox has much more day than night.

INTERESTING EQUINOX FACTOIDS:

There are a number of other interesting things about the equinoxes:

*Equinoxes have a temporary disruptive effect on geostationary communications satellites. This happens because there is a point in time at the equinoxes when the Sun is directly behind the satellite from the point of view of receiving stations on Earth. The Sun's radiation overwhelms the much weaker signal from the satellite with noise. The duration of this effect varies. it may last only a few minutes, but it may persist up to an hour.

*There are a number of other names for the two equinoxes rather than spring/Vernal equinox and autumnal/fall equinox. These names suffer from the fact that they are obvious references to matters only in the northern hemisphere. South of the equator the situation of the seasons is precisely the opposite. Some have proposed using 'March Equinox' and 'September Equinox'. This is familiar to those who use the western solar based calender, but lunar calenders such as the Jewish or Muslim calenders have the equinoxes falling in different months from year to year. The equinoxes were once named in astrology as the 'First Point of Aries' and the 'First Point of Libra'. Because of precession these astrological signs are no longer the constellations where the equinoxes actually occur. Today they are the 'Pisces Equinox' and the 'Virgo Equinox'. One hardly ever hears such terms in common usage. Finally, there are the 'Northward Equinox' and the 'Southward Equinox', referring to the direction of the apparent motion of the Sun at each equinox. These terms are also rarely used.

*There is a persistent folk legend that the equinoxes are the only time of the year when you can stand an egg on end. This myth has been thoroughly debunked by the owner of the Bad Astronomy Blog who devotes a lot of his efforts to exposing hoaxes, myths and misconceptions in the area of astronomy. In actual fact you can stand an egg on end at any time of year. It just takes a little practice and skill. See the article at http://www.badastronomy.com/bad/misc/egg_spin.html

*Because the Sun is not a point source of light it actually takes the Sun about two and 1/2 days to cross the equator. The equinox is defined as the time when the midpoint of the Sun's disc is over the equator.

*A couple of good references on things equinoxal:

1)Details about the length of day and night at the equinoxes.

2)Calculation of length of day.

3)Table of times for equinoxes, solstices, perihelion and aphelion in 2000-2020.

COMING SOON AT MOLLY'S BLOG: SHINE ON HARVEST MOON: WEDNESDAY,SEPTEMBER 26TH

EQUINOXES:

At the time of the Spring (Vernal) Equinox this year Molly posted on matters concerning equinoxes in general. To read this before the upcoming event go to http://mollymew.blogspot.com/2007/03/welcome-to-spring-today-at-0007.utc.html .

As I said, more later.

FALL EQUINOX:

WELCOME TO AUTUMN:

The Fall Equinox will arrive this Sunday, September 23rd at 4:51 am. The Equinox is the exact time when daylight and nighttime are exactly equal or rather when the Sun is directly overhead at the equator.The "day" of closest equality of night and day is actually something quite different-the "equilux". This day is about three days later than the equinox in the fall and three days earlier than the spring equinox.The autumn equinox is a time for celebration and a "gathering-in". Stay tuned to Molly's Blog for more on this event.

AURIGID METEOR SHOWER REPORTS:

The online space news site Space.Com has published a story written by Peter Jenniskens of the airborne Multi-Instrument Aircraft Campaign. This event was witnessed by only twp observers in 1994 and one in 1986. This year far more people, perhaps thousands, managed to catch the shower due to the predictions of the time based on modelling by Jenniskens' team. Observers in the eastern USA, Brazil and Europe, while unable to directly see the meteors, detected them by listening for distant radio signals. The peak rate at 4:04 PDT detected by the airborne observers was about 100/hour, and the airborne crew saw around 120 meteors each. This meant that they outshone the August Perseids, even if only for a very brief time (see blogs on this post for August and September for more about both the Perseids and the Aurigids). Further details on the results can be found at the above link and also at http://aurigid.seti.org/ . The latter link also gives details on what was seen by ground observers who lived where the shower was visible that night.

PARTIAL SOLAR ECLIPSE COMING UP ON SEPT 11:

VISIBLE ONLY FROM SOUTH AMERICA:

On Tuesday, September 11th the second partial solar eclipse will be visible from points in southern South America and in Antarctica. The maximum extent of the eclipse, about 75%, will only be visible on the high seas in the Drake Passage. Still, residents of Peru, Bolivia, Paraguay, Brazil, Uruguay, Argentina and Chile will be able to view varying amounts of the event. The eclipse will begin at 10:25:46 UT and end at 14:36:33 UT. If you are resident in South America see the Time and Date website to convert these times to your local time.

There will be no totality during this eclipse because the Moon's umbra will pass into space about 802 kilometers below the South Pole.

To learn more about this event and other upcoming eclipses both solar and lunar and to get local times go to NASA's Eclipse Home Page. Click on the figure to the left to get an enlarged view of the path of this eclipse.

OCCULTATION OF THE PLEIADES TONIGHT:

As Molly mentioned yesterday (see Sept. 1- 'Lunar Occultation of the Pleiades Tomorrow') tonight the Moon will occult 5 of the "seven sisters" that make up the Pleiades star cluster. The event will begin shortly after midnight here in Central Daylight Time. For the time in other time zones visit the Time and Date.Com website. For a forecast of visibility conditions in numerous places across North America see the Clear Dark Sky website.

OPEN CLUSTERS:

The Pleiades are an "open star cluster". These are star groups which were formed by the same interstellar molecular cloud and are still loosely gravitationally bound to each other. This is in contrast to "globular clusters" where the stars are tightly bound to each other. Open clusters form only in spiral or irregular galaxies, and are usually less than a few hundred million years old. This is because they are gradually disrupted by encounters with other objects in their home galaxy as well as by close encounters within the cluster itself. Over time radiation pressure drives the remaining gas within the cloud from which the stars form away from the cluster. Typically only about 10% of the material ends up condensing into stars. Star clusters are important for the study of stellar evolution because they are a 'control group' that are quite similar in age and chemical composition.

Some star clusters such as the Pleiades have been known since ancient times. Others appear merely as fuzzy patches to the naked eye. Globular clusters are more common towards the centre of galaxies, and consist of thousands of stars in a regular spherical distribution. Open clusters are found in any direction in the sky and have a much sparser stellar population. They do, however, form almost only in the plane of galaxies such as the Milky Way, and hence they are sometimes referred to as galactic clusters.

Stars always form in groups because only a cloud of gas containing the mass of many stars has enough matter to collapse under gravity. Many things such as shock waves from nearby supernovae or the graviational influence of other bodies may initiate the process of collapse. Several thousand stars are usually formed in the process. In the Milky Way such formations are estimated to occur every few thousand years. Once the process is underway the hottest and largests stars, of class O and B, emit radiation sufficient to ionize the surrounding gas, producing what is known as an H II region. The radiation from these ultrahot stars and the first few supernovae both act to expell the remaining gas from the area of the cluster, and in afew tens of millions of years there will no be enough to support further star formation.

Clusters can be classified by the Trumpler system devised by Robert Trumpler in 1930. The Roman numberals I to IV indicate the "concentration" of stars in the cluster, from highly concentrated to weakly concentrated). The arabic numerals 1 to 3 indicate the range of brightness of the stars, from a small to a large range. The letters "p", "m" or "r" are added to say if the cluster is poor, medium or rich in stars. The letter "n" is added if the cluster lies with enough gas to produce a visible nebula. By this method the Pleiades are an I3rn system. The Pleiades are one of over 1,000 known open star clusters in our galaxy. There are probably many times more yet to be discovered. As mentioned above open star clusters are found only in spiral or irregular galaxies. In elliptical galaxies star formation has essentially ceased many millions of years ago, and hence the young stars found on open clusters are not present.

Open clusters are essentially unstable. In many the average speed of the individual stars formed is greater than the escape velocity from the cluster. The stripping away of extrastellar gas alluded to above also reduces the mass of the cluster and hence its gravitational pull. Those clusters with enough mass to avoid early dispersal may remain in existence for tens of millions of years, but eventually processes both internal (close encounters between stars) and external (encounters with molecular gas clouds) lead to the disruption of the cluster.

Because the stars in an open cluster are of about the same age, the same distance from Earth and of roughly the same material they are useful in studying and testing models of stellar evolution. They are also useful in determining astronomical distance scales. Some clusters such as the Pleiades are close enough that their distance can be measured directly by parallex (the small change in apparent position when the Earth is at one or the other side of the Sun during a year. Many cluster distances have been determined by the Hipparcos satellite using this method. Another method is to use the "proper motion" of members of the cluster which converge on a "vanishing point". This along with the radial velocity from the Doppler shift of the stars and the angle from the cluster to its vanishing point give the distance by simple trignometry. Distances to clusters too far to estimate by these methods can be estimated by comparing a Hertzprung Russell diagram from a cluster of a known distance to a close fit for the more distant cluster of interest. A comparison of the apparent magnitude of stars in the distant cluster to the absolute magnitude of stars whose distance is known allows an estimate of distance to be made.

THE PLEIADES:

The Pleiades comprise not just the "seven sisters" but also stars named after their mythological parents, Atlas and Pleione(see diagram at the top of this page). You can find the Pleiades by looking down towards the horizon from the constellation Perseus (see articles in the August archive of this blog about the Perseid meteor shower). Both the Pleiades and Perseus are just above a line drawn due east from the two upper stars of the "Big Dipper". As the year advances the Pleiades will gradually come to lie more east than down from Perseus. You have to have good eyesight to distinguish individual stars in the Pleiades, but ancient people were able to distinguish at least 6 of the "7 sisters". Many cultures, both European and Native American, used the Pleiades as a sort of celestial eye-chart. The keenness of your vision could be estimated by how many stars you could see in the group.

This star group is prominant in many cultures across the world. In Japan the group is known as Subaru which gave its name to the car manufacturing company which uses the stars in its logo. In China they are the Hairy Head of the white Tiger of the West. In India they are known as the Kuttika which means "the cutters". They are also called the star of fire and are associated with the Vedic God Agni, the fire god. Other Hindu myths say they are the six mothers of the war god Skanda who developed six faces for each one of them. The star group is mentioned in both Homer's Illiad and Odyssey, as well as in Hesiod's Works and Days. They mentioned three times in the Bible (Job 9:9, 38:31 and Amos 5:8), and some Muslim scholars believe that they are the Star of Najm mentioned in the Koran.

Indiginous Australians have many myths about the group. One of these is that the Pleiades is a woman who escaped being raped by the 'Man in the Moon'. Another myth is that they are seven sisters who are being pursued by a man named Jilbi Tjapaltjarri. They were transformed into stars to escape his pursuit. In return Jilbi trandformed himself into one of the stars in Orion's belt so that he could continue his pursuit across the sky.

The Vikings referred to them as Freyja's hens , and their name in many European languages compares them to a hen with chicks. To the Celts the stars were associated with mourning and funerals. This was because during the Bronze Age this cluster rose in the eastern sky just as the Sun was setting in the west at the time of Samhain (our modern Halloween), the festival of remembrance of the dead. Because of precession this no longer holds true, but it held true long enough to become embedded in Celtic mythology.

In Africa the Pleiades are known as kilimia in the Swahili language. This translates as the "digging stars" as it was time to start digging as the onset of the annual rains was near when they were visible. In southern Africa the Basotho people call the Pleiades seleme se setshehadi , the "female planter" because their disappearance in april and the appearance of the star Achernar signals the beginning of the cold season. Most peoples in southern Africa associated the visibility of the Pleiades with the time of agriculture and plenty.

In the New World the Seris of northwestern Mexico call the Pleiades Cmaamc ie women as they are supposed to be seven women giving birth. Mayan cultures in Guatemala used the Pleiades and also the star Eta Draconis as references for astronomy. The Pleiades were believed to be their original home by some Mayans. The Aztecs of Mexico borrowed this method of reckoning, and based their calender on these stars. Their year began when they were first observed the heliacal rising in the east just before being obliterated by the rising Sun. This was generally in our month of June. Both the Maoris of New Zealand and the original Hawaians also set their new year by this method.

THE PLEIADES:THE MYTH AND THE STARS:

The modern names of the stars in this cluster are taken from Greek mythology. According to this story the "seven sisters" are the daughters of the titan Atlas and the sea-nymph Pleione (see the diagram for the stars named after this pair). They were also sisters to other figures from Greek mythology including Calypso, Hyas, the Hyades and the Hesperides. The Pleiades were nymphs in the service of the goddess Artemis, and along with the Hyades served as the nursemaids and tecahers of the infant god Bacchus. As the story goes when Atlas was forced to hold the world on his shoulders Orion began to pursue them. To help them escape Zeus first changed them into doves, and then,when this proved insufficient, into stars. orion the hunter is said to still pursue them through the sky.

The star Atlas is a blue giant star about 290 lys from Earth. His consort Pleione is blue subgiant about 95 light years (lys) away. Atlas has a magnitude of 3.6, and Pleione shines at magnitude 5.1. Their daughters mated with several of the gods and produced a number of children.

The eldest of the seven sisters was Maia. She mated with Zeus to give birth to the god Hermes. Maia is another blue giant that lies about 390 lys from Earth and has an apparent magnitude of 3.9. Electra became the wife of Corythus but was seduced by Zeus and gave birth to Darnanus (the Dardanelles) who became the founder of the city of Troy. Electra is a blue giant as well, lieing about 390 lys away and shining with a 3.7 magnitude. Alcyone is yet another blue giant star 240 lys distant and with a magnitude of 2.9- the brightest of this star group. She mated with Poseidon and bore him many children.

Taygete was raped by Zeus on Mount Taygetos where she was in attendance on Artemis. The goddess changed her into a doe to escape the god's pursuit, but Zeus continued anyways. The issue of this union was supposed to have been Lacedaemon, the mythical founder of Sparta. Taygete is a blue main sequence star about 360 lys away with an apparent magnitude of 4.3. Another of the stars is Celaeno. She married Poseidon and bore him several children.Celaeno is a blue subgiant about 590 lys away and has an apparent magnitude of 5.5. Sterope mated with the god Ares and produced the son Oenomaus. This star Sterope, also called Asterope, is a blue main sequence star about 490 lys away and has an apparent magnitude of 5.8. The final star in the cluster Merope was the only one of the sisters who escaped divine attention. She was the wife of sisyphus and bore him one son, Glaucus. This star is a blue main sequence star about 390 lys away and has an apparent magnitude of 4.2.

As Molly mentioned yesterday only 5 of the seven sisters are being occulted tonight. The Moon will pass above the stars Alcyone and Merope, as well as Atlas and Pleione. These will be visible throughout the occultation. Have fun and see if you can identify each star in this group.

COMING LATER TONIGHT:

MORE ON THE AURIGID METEOR SHOWER, EARLY MORNING SEPT 1:

TELLING MORE ABOUT THE 'MAYBE METEOR SHOWER':

Molly has blogged previously (see Aug. 29 'The Aurigid Meteor shower' and Aug 11 'The Perseids are Coming') on the subject of the "possible" meteor shower that will occur later this night, towards dawn tomorrow morning. If it does occur the shower will appear to originate from the constellation Auriga with a peak time at about 11:36 GMT. This will translate into a peak time of 4:36 PDT and slightly earlier in the central Pacific and Alaska. Auriga will be about two thirds up in the northeastern sky on the west coast at this time, but in Alaska and the central Pacific it will be considerably lower towards the horizon. This means that the shower will not be visible in east Asia because Auriga will not have risen at the peak time of the shower- and because the shower has a very short viewing time as compared to other annual meteor showers.

The possibility of an outstanding sight during this year's Aurigid time frame was first proposed 7 years ago by California astronomer Peter Jenniskens and Finnish amateur astonomer Esko Lyytinen. Jenniskens has since collaborated with Jeremie Vaubaillon of Caltech to produce a forecast of an extraordinarily intense meteor shower this night. Another forecast by astronomer Danielle Moser of NASA agrees with the timing but predicts a much less intense number of meteors observable. Only the event will tell which one is right.

The meteors from long period comets which are irregular in appearance are rather unique. Because the comets that produce them are such infrequent visitors to the inner solar system the meteors that they produce contain rather "pristine" materials from the early days of the solar system. They are low in sodium, often penetrate deeper into the atmosphere than usual and at higher speeds (producing more brilliant displays) . The colour of the meteors produced will give clues to their elemental composition. Past observations suggest that the remnants of "pristine cometary crust" will give a greenish hue to many of the meteors observed.

On August 11th Molly mentioned the 'Aurigid Meteor Shower Observing Campaign' that astronomers on the west coast of the USA are mounting to observe this once in a lifetime event. The people involved in this research are looking for the collaboration of amateur astronomers to supplement their own observations. To learn more about this campaign, to participate in the research or to generally learn more about the Aurigid meteor shower go to http://aurigids.seti.org or see our August 11th post.

Happy viewing. Molly won't see this event, but good luck to all the people out in BC.

See also on this blog:

August 29: 'The Aurigid Meteor Shower'.

August 11: 'The Perseids Are Coming'

"CLEAR DARK SKY"

AN INTRODUCTION:

Many amateur observers of the night sky can be more than slightly frustrated by the local weather forecasts available to them. The usual Environment Canada forecasts, for instance, lack both specificity and accuracy. It does you little good if you want to see if an event that will happen around 5:00 am to know that the forecast for that night is "variably cloudy". Very nice. Molly has mentioned a website previously that provides a much better forecast for those who are interested in viewing conditions. This is the ClearDarkSky site. It is the creation of two Ottawa amateur astronomers, Attilla Danko and Allan Rahill. The latter works for the Canadian Meteorological Centre in Ottawa and has put his weather forecasting talents to work on this website. Danko created the computer programs that allowed Rahill's weather maps to be translated into viewing forecasts for specific localities. To read a general overview of their collaboration and the result see http://www.astronomytoday.com/astronomy/interview7.html .

WHAT IS 'CLEAR DARK SKY' ?:

Stated succinctly the ClearDarkSky site is a web resource that can give amateur astronomers very specific, hour by hour, forecasts for 48 hours of a number of viewing conditions that affect you ability to see what is in the skies. The data provided is much more specific than that provided by the usual weather forecasts. There are a total of 3188 'Clear Sky Clocks' for various locations across North America, 547 Canadian, 14 Mexican, 1 Bahamian and 2626 American sites. In many cases the data presented has a very much finer "resolution" than that presented by the usual weather forecast. Forecasts are delivered for points as close as 25kms apart. The forecast is also arranged as an "hour by hour" presentation.

What is presented in the forecasts ? Once more a lot more than the usual weather forecast. The colour coded bar presentations present forecasts for cloud cover, transparency, seeing (a composite measure that depends on many conditions), darkness, wind, humidity and temperature. All of these may affect either what you can see or your simple comfort in observing. All that Molly could think of adding would be a biting insect forecast. The only complaint that Molly has about the site is that the colour coding can be a little hard to read. I find myself sticking my face about 8 inches in front of the computer screen to try and see exactly what colour each hour block is, particularly in the "cloud cover" row. But that quibble is minor in light of how valuable such a well defined forecast is.

MORE FROM THE SITE:

The ClearDarkSky site is not just a viewing forecast aid, though that would be a treasure in itself. Each locality listed has links to Sun and Moon data, road, topological and satellite maps, a star map link and even a "Clear Sky Alarm clock" that can alert anybody at that locality about upcoming clear sky viewing conditions. The main site has links to North American astronomy clubs, planetariums, museums, observatories, the Royal Astronomical Society of Canada and its various branches, star parties and other things that might be of interest to the serious amateur astronomer such as dark sky preserves, astronomy villages, campgrounds and wildlife centres.

There is even an invitation to participate in Allan Rahill's ongoing project to improve the "seeing" forecast with more and more real data from collaborators across the continent. This is the North American Seeing Observation Program. Astronomy is an area of science that actually has a large input from the non-academic amateur, and this is one of the many projects that are ongoing in the field.

So...drop by ClearDarkSky for a real treat.