lunar calendar Archives

December 12, 2017April 17, 2022 by Matt Williams

86 Stars Just got Official Names from the IAU

The two brightest stars of the Centaurus constellation - (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri. Credit: Wikipedia Commons/Skatebiker

What springs to mind when we think of the most commonly-known stars in the night sky? Chances are, it would be stars like Sirius, Vega, Deneb, Rigel, Betelgeuse, Polaris, and Arcturus – all of which derive their names from Arabic, Greek or Latin origins. Much like the constellations, these names have been passed down from one astronomical tradition to another and were eventually adopted by the International Astronomical Union (IAU).

But what about the astronomical traditions of Earth’s many, many other cultures? Don’t the names they applied to heavens also deserve mention? According to the IAU, they do indeed! After a recent meeting by the Working Group on Star Names (WGSN), the IAU formally adopted 86 new names for stars drawn largely from the Australian Aboriginal, Chinese, Coptic, Hindu, Mayan, Polynesian, and South African peoples.

The WGSN is an international group of astronomers tasked with cataloging and standardizing the star names used by the international astronomical community. This job entails establishing IAU guidelines for the proposals and adoption of names, searching through international historical and literary sources for star names, adopting names of unique historical and cultural value, and maintaining and disseminating the official IAU star catalog.

*Star map painting by Senior Wardaman Elder Bill Yidumduma Harney, featuring the Milky Way, the Moon, and ancestor spirits. Credit: IAU*

Last year, the WGSN approved the names for 227 stars. With these latest additions, the catalog now contains the names of 313 stars. Unlike standard star catalogs containing millions or billions of stars designated using strings of letters and numbers, the IAU star catalog consists of bright stars with proper names derived from historical and cultural sources. As Eric Mamajek, chair and organizer of the WGSN, indicated in an IAU press release:

“The IAU Working Group on Star Names is researching traditional star names from cultures around the world and adopting unique names and spellings to avoid confusion in astronomical catalogues and star atlases. These names help ensure that intangible astronomical heritage from skywatchers around the world, and across the centuries, are preserved for use in an era of exoplanetary systems.”

A total of eleven Chinese star names were incorporated into the catalog, three of which are derived from the “lunar mansions” of traditional Chinese astronomy. This refers to vertical strips of the sky that act as markers for the progress of the Moon across the sky in the course of a year. In this sense, they provide a basis for the lunar calendar in the same way that the zodiac worked for Western calendars.

Two names were derived from the ancient Hindu lunar mansions as well. These stars are Revati and Bharani, which designate Zeta Piscium and 41 Arietis, respectively. In addition to being a lunar mansion, Revati was also the daughter of King Kakudmi in Hindu mythology and the consort of the God Balarama – the elder brother of Krishna. On the other hand, Bharani is the name for the second lunar mansion in Hindu astronomy and is ruled by Shurka (Venus).

*Position of the Hindu Nakshatra Mandala, the “lunar mansions” in Hindu mythology. Credit: Wikipedia Commons/ Kishorekumar 62*

Beyond the astronomical traditions of India and China, there are also two names adopted from the Khoikhoi people of South Africa and the people of Tahiti – Xamidimura and Pipirima. These names were approved for Mu¹ and Mu² Scorpii, the stars that make up a binary system located in the constellation of Scorpius. Xamidimura is derived from the Khoikhoi name for the star xami di mura – literally “eyes of the lion.”

Pipirima refers to the inseparable twins from Tahitian mythology, a boy and a girl who ran away from their parents and became stars in the night sky. Then you have the Yucatec Mayan name Chamukuy, a small bird that now designates the star Theta-2 Tauri, which is located in the Hyades star cluster in Taurus.

Four Aboriginal Australian star names were also added to the catalog, including the Wardaman names Larawag, Ginan, and Wurren and the Boorong name Unurgunite. These names now designate Epsilon Scorpii, Epsilon Crucis, Zeta Pheonicis, and Sigma Canis Majoris, respectively. Given that Aboriginal Australians have traditions that go back as far as 65,000 years, these names are some of the oldest in existence.

The brightest star to receive a new name was Alsephina, which was given to the star previously designated as Delta Velorum. The name stems from the Arabic name al-safinah (“the ship”), which refers to the ancient Greek constellation Argo Navis (the ship of the Argonauts). This name goes back to the 10th-century Arabic translation of the Almagest, which was compiled by Ptolemy in the 2nd century CE.

*Artist’s concept of exoplanets orbiting a red dwarf star. Credit: NASA/JPL-Caltech*

The new catalog also includes Barnard’s Star, a name that has been in common usage for about a century but was never an official designation. This red dwarf star, which is less than six light-years from Earth, is named after the astronomer who discovered it – Edward Emerson Barnard – in 1916. It now joins Alsafi (Sigma Draconis), Achird (Eta Cassiopeiae), and Tabit (Pi-3 Orionis) as being one of four nearby stars whose proper names were approved in 2017.

One of the hallmarks of modern astronomy is how naming conventions are moving away from traditional Western and Classical sources and broadening to become more worldly. In addition to being a more inclusive, multicultural approach, it reflects the spirit of modern astronomical research and space exploration, which is characterized by international cooperation.

Someday, assuming our progeny ever go forth and begin to colonize distant star systems, we can expect that the stars and planets they come to know will have names that reflect the diverse astronomical traditions of Earth’s many cultures.

Further Reading: IAU

June 1, 2016June 2, 2016 by David Dickinson

This Friday: The Moon Meets Mercury in the Dawn Sky

The waxing crescent Moon setting over Cadiz, Spain. Image credit: Dave Dickinson

So, have you been following the path of the waning Moon through the dawn sky this week? The slender Moon visits some interesting environs over the coming weekend, and heralds the start of Ramadan across the Islamic world next week.

First up, the planet Mercury rises an hour before the Sun in the dawn this week. Mercury reaches greatest elongation west of the Sun on Sunday, June 5^th at 9:00 Universal Time (UT).

The Moon meets Mercury on the morning of June 3rd. Image credit: Stellarium.

The slender waning crescent Moon passes less than one degree from +0.8 magnitude Mercury (both 24 degrees from the Sun) on the morning of Friday, June 3^rd at 10:00 UT. While this is a close shave worldwide, the Moon will actually occult (pass in front of) Mercury for a very few observers fortunate enough to be based on the Falkland Islands in the southern Atlantic.

The Moon is 5.2% illuminated and 41 hours from New during the occultation. Meanwhile, Mercury shines at magnitude +0.8 and displays an 8.6” 33.5% illuminated disk during the event. Also, watch for ashen light or Earthshine faintly lighting up the nighttime side of the Moon. You’re seeing sunlight, bounced off of the land, sea and (mostly) cloud tops of the fat waxing gibbous Earth back on to the lunar surface, one light-second away. The Big Bear Solar Observatory has a project known as Project Earthshine which seeks to measure and understand the changes in albedo (known as global dimming) and its effects on climate change.

The Moon occults Mercury three times in 2016. Occultations of the innermost planet are especially elusive, as they nearly always occur close to the Sun under a daytime sky. This week’s occultation occurs less than 48 hours from greatest elongation; the last time one was closer time-wise was March 5^th, 2008, and this won’t be topped until February 18^th, 2026, with an occultation of Mercury by the Moon just 18 hours prior to greatest elongation. And speaking of which, can you spy +0.8 magnitude Mercury near the crescent Moon on Friday… during the daytime? Use binocs, note where Mercury was in relation to the Moon before sunrise, but be sure to physically block that blinding Sun behind a building or hill!

Mercury reaches greatest elongation six times in 2016: three in the dusk (western), and three in the dawn (eastern).

The Moon also passes less than five degrees from the planet Venus on June 5^th at 2:00 UT, though both are only 2 degrees from the Sun. Fun fact: the bulk of the Sun actually occults Venus for 47 hours as seen from the Earth from June 6^th through June 8th.

You can observe the passage of Venus through the 15 degree wide field of view of SOHO’s LASCO C3 camera over the next few weeks until July 5th.

Venus reaches superior conjunction on the far side of the Sun 1.74 astronomical units (AU) from the Earth at 21:00 UT on Monday, June 6th.

New Moon occurs at 4:00 UT on Sunday, June 5^th, marking the start of lunation 1156.

The Moon and Ramadan

The first sighting of the slim crescent Moon also marks the start of the month of Ramadan (Ramazan in Turkey) on the Islamic calendar. Unlike the western Gregorian calendar, which is strictly solar-based, and the Jewish calendar, which seeks to reconcile lunar and solar cycles, the Islamic is solely based on the 29.5 synodic period of the Moon. This means that it moves forward on average 11 days per Gregorian year. The hallmark of Ramadan is fasting from dawn to dusk, and Ramadan 2016 is an especially harsh one, falling across the northern hemisphere summer solstice (and the longest day of the year) on June 20th. The earliest sunrise occurs on June 14th, and latest sunset on June 27th for latitude 40 degrees north. Finally, the Earth reaches aphelion or its farthest point from the Sun on July 4th at 1.01675 AU or 157.5 million kilometers distant.

In 2016, the Moon will first likely be spotted from the west coast of South America on Sunday night June 5^th, though many locales worldwide may not see the Moon until June 6^th. There can be some disparity as to just when Ramadan starts based on the first sighting of the crescent Moon. The Islamic calendar is also unique in that it still relies on direct observation of the waxing crescent Moon. Other calendars often use an estimated approximation in a bid to keep their timekeeping in sync with the heavens. The computus estimation (not a supervillain, though it certainly sounds like one!) used by the Catholic Church to predict the future date of Easter, for example, fixes the vernal equinox on March 21^st, though it actually falls on March 20^th until 2048, when it actually slips to March 19th.

Ramadan has been observed on occasion in space by Muslim astronauts, and NASA even has guidelines stipulating that observant astros will follow the same protocols as their departure point from the Earth (in the foreseeable future, that’s the Baikonur Cosmodrome in Kazakhstan.

Can you see the open cluster M35, just six degrees north (right) of the thin crescent Moon on the evening of Monday, June 6^th?

We think its great to see direct astronomical observation still having a hand in everyday human affairs. This also holds a special significance to us, as we’re currently traveling in Morocco.

Don’t miss the meeting of Mercury and the Moon on Friday morning, and the return of the Moon to the dusk skies next week.

August 7, 2013December 23, 2015 by David Dickinson

Ancient Astronomical Calendar Discovered in Scotland Predates Stonehenge by 6,000 Years

A wintertime rising gibbous Moon. (Image credit: Art Explosion).

A team from the University of Birmingham recently announced an astronomical discovery in Scotland marking the beginnings of recorded time.

Announced last month in the Journal of Internet Archaeology, the Mesolithic monument consists of a series of pits near Aberdeenshire, Scotland. Estimated to date from 8,000 B.C., this 10,000 year old structure would pre-date calendars discovered in the Fertile Crescent region of the Middle East by over 5,000 years.

But this is no ordinary wall calendar.

Originally unearthed by the National Trust for Scotland in 2004, the site is designated as Warren Field near the town of Crathes. It consists of 12 pits in an arc 54 metres long that seem to correspond with 12 lunar months, plus an added correction to bring the calendar back into sync with the solar year on the date of the winter solstice.

Diagram... — A diagram of the Warren Field site, showing the 12 pits (below) and the alignment with the phases of the Moon plus the rising of the winter solstice Sun. Note: the scale should read “0-10 metres.” (Credit: The University of Birmingham).

“The evidence suggests that hunter-gatherer societies in Scotland had both the need and sophistication to track time across the years, to correct for seasonal drift of the lunar year” said team leader and professor of Landscape Archaeology at the University of Birmingham Vince Gaffney.

We talked last week about the necessity of timekeeping as cultures moved from a hunter-gatherer to agrarian lifestyle. Such abilities as marking the passage of the lunar cycles or the heliacal rising of the star Sirius gave cultures the edge needed to dominate in their day.

For context, the pyramids on the plains of Giza date from around 2500 B.C., The Ice Man on display in Bolzano Italy dates from 3,300 B.C., and the end of the last Ice Age was around 20,000 to 10,000 years ago, about the time that the calendar was constructed.

“We have been taking photographs of the Scottish landscape for nearly 40 years, recording thousands of archaeological sites that would never have been detected from the ground,” said manager of Aerial projects of the Royal Commission of Aerial Survey Projects Dave Cowley. “It’s remarkable to think that our aerial survey may have helped to find the place where time was invented.”

The site at Warren Field was initially discovered during an aerial survey of the region.

Vince Gaffney professor of Landscape and Archaeology at University of Birmingham in Warren Field, Crathes, Aberdeenshire where the discovery was made. — Vince Gaffney, professor of Landscape and Archaeology at University of Birmingham in Warren Field, Crathes, Aberdeenshire where the discovery was made. (Credit: The University of Birmingham).

The use of such a complex calendar by an ancient society also came as a revelation to researchers. Emeritus Professor of Archaeoastronomy at the University of Leicester Clive Ruggles notes that the site “represents a combination of several different cycles which can be used to track time symbolically and practically.”

The lunar synodic period, or the span of time that it takes for the Moon to return to the same phase (i.e., New-to-New, Full-to-Full, etc) is approximately 29.5 days. Many cultures used a strictly lunar-based calendar composed of 12 synodic months. The Islamic calendar is an example of this sort of timekeeping still in use today.

However, a 12 month lunar calendar also falls out of sync with our modern Gregorian calendar by 11 days (12 on leap years) per year.

The familiar Gregorian calendar is at the other extreme, a calendar that is strictly solar-based. The Gregorian calendar was introduced in 1582 and is still in use today. This reconciled the 11 minute per year difference between the Julian calendar and the mean solar year, which by the time of Pope Gregory’s reform had already caused the calendar to “drift” by 10 days since the 1^st Council of Nicaea 325 AD.

Artist’s conception of the Warren Field site during the winter solstice. (Credit: The University of Birmingham). Credit: The University of Birmingham

Surprisingly, the calendar discovered at Warren Field may be of a third and more complex variety, a luni-solar calendar. This employs the use of intercalary periods, also known as embolismic months to bring the lunar and solar calendar back into sync.

The modern Jewish calendar is an example of a luni-solar hybrid, which adds an extra month (known as the 2^nd Adar or Adar Sheni) every 2-3 years. This will next occur in March 2014.

The Greek astronomer Meton of Athens noted in 5^th century B.C. that 235 synodic periods very nearly add up to 19 years, to within a few hours. Today, this period bears his name, and is known as a metonic cycle. The Babylonian astronomers were aware of this as well, and with the discovery at Warren Field, it seems that ancient astronomers in Scotland may have been moving in this direction of advanced understanding as well.

It’s interesting to note that the site at Warren Field also predates Stonehenge, the most famous ancient structure in the United Kingdom by about 6,000 years. 10,000 years ago would have also seen the Earth’s rotational north celestial pole pointed near the +3.9^th magnitude star Rukbalgethi Shemali (Tau Herculis) in the modern day constellation of Hercules. This is due to the 26,000 year wobble of our planet’s axis known as the precession of the equinoxes.

The precession of the north celestial pole over millenia. (Credit: Wikimedia Commons graphic under a Creative Commons Attribution 2.5 Generic license. Author: Tau'olunga). — The precession of the north celestial pole over millennia. (Credit: Wikimedia Commons graphic under a Creative Commons Attribution 2.5 Generic license. Author: Tau’olunga).

The Full Moon nearest the winter solstice also marks the “Long Nights Moon,” when the Full Moon occupies a space where the Sun resides during the summer months and rides high above the horizon for northern observers all night. The ancients knew of the five degree tilt that our Moon has in relation to the ecliptic and how it can ride exceptionally high in the sky every 18.6 years. We’re currently headed towards a ‘shallow year’ in 2015, where the Moon rides low in relation to the ecliptic. From there, the Moon’s path in the sky will get progressively higher each year, peaking again in 2024.

Who built the Warren Field ruins along the scenic Dee Valley of Scotland? What other surprises are in store as researchers excavate the site? One thing is for certain: the ancients were astute students of the sky. It’s fascinating to realize how much of our own history has yet to be told!