Happy Birthday Carl Sagan

Carl Sagan was a towering figure in science. He was born on November 9, 1934, in Brooklyn, New York, and died following a long battle with cancer on December 20, 1996, in Seattle, Washington. In between, in just 62 years, he reshaped public understanding of physics, astronomy, and space exploration. More than this, he was a leader in exploration and discovery, involved in many of the scientific teams behind truly ground-breaking space missions in the 1960s and 1970s, including the Apollo moon landings and the Viking missions to Mars.

I first started to encounter Carl Sagan as a popularizer of science while an undergraduate at University of Guelph, and wrote a couple of columns mentioning him for The Ontarion, the university’s newspaper, in the early 1980s. I briefly thought of pursuing grad work on exobiology but ended up continuing along with evolutionary ecology instead, at Guelph for a few more years. His influences are still all around us.

Visit the Carl Sagan Portal to experience a little of this amazing gentleman’s life and contributions: http://www.carlsagan.com/

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Get ready for AstroCATS 2014: Canada’s Astronomy Trade Show!

The Royal Astronomical Society of Canada – Hamilton Centre is presenting the second annual Canadian Astronomy Trade Show, AstroCATS, on 3-4 May, 2014!

The web site for this exciting event is: http://www.astrocats.ca/

The big show will open at 10 AM on Saturday 3 May, and close at 6. On Sunday it opens again at 10 and closes at 4. AstroCATS 2014 will be held in the David Braley Athletic & Recreation Centre at Mohawk College, 135 Fennell Ave. West, Hamilton L9C 1E9.

Visit the web site to find lists of vendors, special speakers, and all of the exciting highlights planned for the show in May. Hope to see you there!

Happy Birthday Tycho Brahe

Tycho Brahe (14 December 1546 – 24 October 1601) is commemorated in one of my favourite craters on the moon (crater Tycho) and he’s well worth remembering. Tycho made many observations of the positions of the planets and stars in the days just before the invention of telescopes. By observing new stars – we call now them novas – and showing by their position observed over time that they must lay outside of the atmosphere, Tycho proved that they were not atmospheric phenomena. Thus, he proved that the realm of the stars was not immutable.

Perhaps his greatest contribution to astronomy was in fact sharing his observations with his protégé Johannes Kepler, who then used the detailed location information for the planets in the developing of his laws of planetary motion.

He was a complex and colourful character. For more details, take a look at the profile of his life and contributions on Wikipedia: http://en.wikipedia.org/wiki/Tycho_Brahe

Betelgeuse: A Supergiant To Love

In the evening hours of late winter and early spring in the northern mid-latitudes like Ontario, the constellation Orion is a very familiar friend. The brightest star in Orion, Betelgeuse, is itself endlessly fascinating.

If you can picture the constellation then you can find Betelgeuse right away. It’s the orange-shaded bright star at the “right shoulder” of Orion – or on the left as we see the asterism. The other stars in Orion don’t have a noticeable colour most of the time, but Betelgeuse is decidedly reddish-orange.

Consellation Oroion rising over a surbab street in Burlington, Ontario, on the evening of 2013 March 26. Betelgeuse, the brightest star in Orion, is in the middle of the frame and about 1/8th of the way down from the top.

Constellation Orion rising over a suburban street in Burlington, Ontario, at about 9:45 PM on the evening of 2013 March 26. Betelgeuse, the brightest star in Orion, is in the middle of the frame and about 1/8th of the way down from the top.

Betelgeuse has been known as an interesting star since antiquity, but what astronomers have learned in the past 20 or more years make it all the more fascinating. For one thing, we don’t know how far away it is too much in the way of accuracy. Betelgeuse is relatively close to earth – somewhere between 400 and 700 light years away, or only about half as far as the Great Nebula in Orion, which we see with our naked eyes as the third “star” in the sword hanging from Orion’s belt. The lack of accuracy is no indication of lack of trying. For stars of this distance, astronomers often use a triangulation method called parallax to work out distances. Betelgeuse is hard to pin down this way because it is not in fact a “point” of light in the sky. The star is so big and so close that it actually has been photographed as a disk by the Hubble Space Telescope in 1995 (Gilliland & Dupree. 1996). It has a complex outer envelope that is changing its size and shape, and makes the parallax method no better than about 1 part in 5 for accuracy. The star is about 640 light years away, but that’s plus & minus 140 light years!

The size of this star is also staggering. Its diameter is approximately the same as the diameter of the orbit of Saturn in our own solar system. It’s also shining about 100,000 times as bright as our own sun. It’s likely a relatively young star compared to our own sun, and some time in the near future (in astronomical terms) it will likely explode as a supernova.

Recent scientific papers on Betelgeuse have gathered together more observations of the star itself and have tried to interpret various areas that look brighter to us as either bright patches on a darker background, or possibly  as bright areas areas showing up through overlaying dark features.

This star is also moving quickly toward a linear “wall” of material that is part of the local stellar environment. Betelgeuse has a shell of glowing material thought to be part of the material blown off of the surface of the star in the past. This shell will hit the wall in about 5,000 years, followed by the star itself about 12,000 years later (Decin et al. 2012). Don’t wait up for it.

Sources

Decin et al. 2012. The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure. Astronomy and Astrophysics 548, A113 (http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/full_html/2012/12/aa19792-12/aa19792-12.html).

Gilliland & Dupree. 1996. HST imaging of Betelgeuse. Stellar surface structure: proceedings of the 176th Symposium of the International Astronomical Union, held in Vienna, Austria, October 9-13, 1995. Edited by Klaus G. Strassmeier and Jeffrey L. Linsky. International Astronomical Union. Symposium no. 176, Kluwer Academic Publishers, Dordrecht, p.165 (http://adsabs.harvard.edu/full/1996IAUS..176..165G)

Copyright © 2013 David Allan Galbraith

 

 

Happy New Year! But Why January 1st?

Have you ever wondered why January 1st is the first day of the New Year?

Vintage New Years Card

Vintage Happy New Years Card Celebrates the Turn of the Year

Our present everyday calendar is pretty much taken for granted, and it works fairly well. It has 365 days in it (more or less), given the adjustment of an extra day every four years (more or less). Most people know that the two equinoxes and the two solstices (natural events) fall more or less within a day or so of the same date each year, so it must have some synchronization with celestial events.

Many people may also be aware that the present calendar used by most of the world (and there are still some others in use, by the way), is called the Gregorian Calendar, and they may even know that it’s named after Pope Gregory XIII. As readers of the Pine River Observatory blog, I hope you might already have that information! But did you know that the Gregorian calendar was created by one of the most respected astronomers and mathematicians of his day, and that one of the largest craters on the moon is named in his honour?

I’m getting ahead of myself. First, we have to consider the matter of calendars themselves, what they do, and then we can see how January became the beginning of the year we now mark.

Calendars are tools that allow people to keep track of time and plan when things are going to take place. Calendars started, and are still, astronomical tools. Although we are used to having one calendar in the west today, there are three different cyclical celestial events that are all involved: the cycle of the earth’s revolution around its polar axis (defining one day), the cycle of the moon’s orbit around the earth (defining one lunar month) and the cycle of the earth’s orbit around the sun (defining one year). Making up a calendar would be easy if these things were strongly related to each other – but they aren’t.

The earliest antecedents of today’s calendar can be traced to Italy roughly 3,000 years ago, with a calendar consisting of ten months of around 30 days each, which began each year in March. About 700 BC January and February were added to the calendar, making the Roman Calendar. About three hundred years later, January was designated as the first month of the year – and thus we have the first of January being considered as the beginning of the year – around 450 BC. Further adjustments were made up to 46 BC, but the passing of the seasons – and the “annual” cycle of the sun – still didn’t align with the calendar. Julius Caesar instigated a further refinement by the astronomer Sosigenes of Alexandria that brought things closer together. This calendar, the Julian Calendar, was aligned only to the solar year. Any attempt to synchronize the annual calendar with lunar cycles was abandoned.

For something close to 1,600 years the Julian Calendar was used by the western world. However, by then errors had accumulated to the point where the calendar date of the equinoxes had crept forward by 13 days, seriously throwing off things like the Christian celebration of Easter. Pope Gregory XIII put into motion the reformation of the calendar in 1582. A Jesuit astronomer and mathematician from Germany, Christopher Clavius (1538–1612), was the person responsible for working out the details of the new calendar. It worked much better than the Julian Calendar in matching up with the solar year’s accounting of days, and it’s the calendar we still use. However, it was not universally adopted; it was another 200 years before it was taken up in England and he United States, for example. And, there are other calendars still in use in various societies around the world, and for various purposes.

So, the convention of starting the year on the first of January has remained in place in the descendants of the Roman Calendar – including our own. Like many things, the convention of having the year start on the first of January is just that – a convention. It is the result of a long history of changes that led to a calendar that works pretty well, but it’s also a compromise.

Both Sosigenes of Alexandria and Christopher Clavius are memorialized in the names of craters on the moon.

Crater Clavius is in the southern highlands of the moon. At 230 km across (and with 18 associated smaller craters) Clavius is one of the largest craters on the moon; remembering for whom it was named is a link to the story of the calendar most of us use today, 430 years after his re-alignment of the days of the year. Crater Sosigenes (17 km across) is located along the western edge of Mare Tranquillitatis (as are three satellite craters, Sosigenes A, B and C), to the east of a larger crater named for Julius Caesar (90 km, with 10 smaller associated craters). Rimae Sosigenes, a lunar rille, stretches to the east of the crater. Apollo 11’s lunar module landed about 280 km south east of this area.

Sources

Information on the history of calendars: Kaler, J. B. 1996. The Ever-Changing Sky: A Guide to the Celestial Sphere. Cambridge University Press. Cambridge, UK. Pg 174-175.

Lunar feature names: International Astronomical Union (IAU)  Working Group for Planetary System Nomenclature (WGPSN). Gazetteer of Planetary Nomenclature. Available on line at: http://planetarynames.wr.usgs.gov/

Public domain vintage Happy New Years Card: http://webclipart.about.com/od/New_Year_Clip_Art/ss/Vintage-Happy-New-Year-Moon.htm

Four Hundred Years Ago Today Galileo Discovered Neptune – Almost

The discovery of the planet Neptune – the eighth and most distant major planet from our sun – nearly took place on December 27th and 28th, 1612 – four hundred years ago today. Most text books record that it was formally discovered over 230 years later.

On that day, Galileo Galilei turned his telescope toward Jupiter, and made detailed notes on the four moons now called the Galilean moons. He also recorded a “fixed star in his notes.” He was actually looking at the planet Neptune. He saw it again a month later, recording its position accurately in meticulous diagrams in his notebooks.

Of course, Galileo doesn’t need any additional discoveries to add to his fame, but historians are always looking over the notes of notable scientists to see what they actually recorded. Standish and Nobili (1997, below) believe that Galileo actually recorded the position of Neptune a total of four times while making notes about Jupiter and the four moons that, as a group, are named after him

What happened two hundred years later was a more complex story than just a recording of an observation. By 1821 astronomers had compiled tables of the motions of all of the planets out as far as Uranus, the seventh planet in the solar system, Between 1844 and 1846 both British and French astronomers made calculations based on the orbital information of Uranus and started a hunt for an unknown, but predicted, 8th planet. Credit for actually spotting Neptune and realizing what he was seeing goes to Johann Gottfried Galle in Berlin in 1846. He was working with predictions from Urbain Le Verrier in France (who was right about where a new planet should be to within about 1° in the sky) and John Couch Adams in Britain (who was a little further off, at 12°, but both predictions were amazing considering the times).

Sources

© 2012, David Allan Galbraith