Looking Forward – And Up – For 2017!

There are a lot of exciting things happening in 2017. Many are covered in detail on large astronomy web sites like Sea and Sky: http://www.seasky.org/astronomy/astronomy-calendar-2017.html

Here are just a few highlights to consider.

11 February 2017 – Lunar Eclipse

Following on from the full moon earlier on the same day, the moon will pass into the edge of the Earth’s shadow for a “penumbral lunar eclipse.” We should be in a great position to see the moon darkening in Ontario.  Here’s a link to a NASA PDF on the event: https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2017Feb11N.pdf

1 April 2017 – Mercury at Greatest Eastern Elongation

The tiny planet Mercury will be visible in the evening sky in early spring; on 1 April it reaches its greatest eastern elongation, and will be visible in the evening sky at sunset.

7 April 2017 – Jupiter at Opposition

On 7 April the Earth will pass directly between Jupiter and the sun. The planet will be very bright in the night sky, rising at sunset. Even a small telescope should reveal the four Galilean moons of our solar system’s largest planet.

15 June 2017 – Saturn at Opposition

In mid-June Saturn and its magnificent rings will be as bright as possible this year. Like Jupiter in April, at opposition the Earth lies directly between Saturn and the sun. Rising at sunset, the planet will appear as a fully-illuminated disk through a modest telescope, nestled within its amazing rings.

cassini_saturn_orbit_insertion

Saturn will be worth watching in 2017 on another front. The Cassini mission is drawing to a close. Throughout the year, NASA mission controllers are swinging the wonderful car-sized spacecraft through Saturn’s rings for the first time, willing to take risks at the tail end of the voyage. Launched 20 years ago (1997), Cassini reached Saturn in 2004 and has been performing nearly flawlessly ever since. Later in 2017 the mission will be brought to an end and the spacecraft will be plunged into Saturn itself, a fiery demise to ensure that the environments of Titan and the other moons of Saturn are not contaminated. The feature image on this post is an artist’s rendering of Cassini and its attached Huygens probe undergoing the orbital insertion maneuver over Saturn in 2004 (Public Domain image; source NASA: http://photojournal.jpl.nasa.gov/catalog/PIA03883).

21 August 2017 – The Great Eclipse

Perhaps one of the big events in 2017 will be the “Great Eclipse” – a total solar eclipse that will cross the continental United States from west to east coasts. On Monday 21 August 2017 the moon will pass directly between the Earth and the Sun, casting a vast circular shadow and giving millions of people a chance to see a true natural spectacle. Totality will pass through states like Kentucky and Tennessee, but from Ontario we will still see a great partial eclipse in the afternoon. Here’s NASA’s posting for eclipse information: http://eclipse.gsfc.nasa.gov/SEplot/SEplot2001/SE2017Aug21T.GIF

13 November 2017 – Close Conjunction of Venus and Jupiter

Just before sunrise Venus and Jupiter will be very close to each other in the sky – just 0.3 degrees apart, or less than the diameter of the full moon.

I hope you can get out and enjoy these and other exciting sky events in 2017! As we get closer to each I will post additional information on viewing – and when possible taking pictures of – these events.

 

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The Equinox is coming. So is the Equilux. So what’s the difference? About four days.

A term from astronomy that has entered common use is Equinox, which translated from its Latin roots roughly means “Equal Night.” Most people think that the Spring (or Vernal) Equinox and the Fall (or Autumnal) Equinox are the days when the length of the daylight and the length of the night are equal. Close, but not quite right.

As the days lengthen from winter toward summer, there certainly is a day during which the length of time we see sunlight and the length of time it’s dark are roughly the same. Technically, however, the timing of each Equinox is defined as the moment when the earth passes a particular point in its orbit around the sun. It’s not defined by the local length of the day.

We have extended our imaginations into space, and covered it with geometric patterns. One of those patterns is an imaginary circle that runs around the entire sky and is called the ecliptic. This is the circle that marks the apparent position of the sun throughout each year, relative to the background stars. It’s called “ecliptic” because of its importance in determining the dates of eclipses. For a lunar or a solar eclipse to take place, the sun, moon, and earth all have to be in alignment with the ecliptic.

Because much of the solar system is in a pretty flat configuration, most of what happens in the solar system also happens near the ecliptic. The orbits of the earth, Mars, Venus, Jupiter, and many other things in the solar system lie in more or less the same plane. So, when you are able to spot any of the planets you’re seeing, approximately, where the ecliptic lies in the sky.

Another similar geometric pattern or circle that is projected into the sky for practical reasons is defined by the earth’s own equator. Astronomers can plot a line across the sky which corresponds, in the “up” direction, to where the equator is on earth. If that’s a little hard to envision, just consider the North Star, Polaris. By accident it sits within a degree of the place in the sky directly above the earth’s north pole (the rotational pole, not the magnetic pole. They’re different things, for another day). From Polaris the celestial equator is 90 degrees south in all directions.

Right. So, two circles projected up in the sky (Picture an orange with two rubber bands around its middle that cross each other as viewed from the inside). They are tilted with respect to each other by the same amount as the earth’s rotation is tilted relative to the position of the sun – around 23 degrees. Each Equinox is defined as the time at which the earth passes the place where the two lines cross. At that moment, the terminator – the place where the sunlit side of the earth and the night side of the earth meet – is at right angles to the earth’s equator.

Now, you’d think that this perpendicular arrangement would mean day and night are of equal length, and geometrically it’s true. However, what we actually see is much more complicated. The apparent length of daylight and night differs from place to place on earth. One of the big factors is the bending effect of the earth’s atmosphere. We sit under an ocean of air, and one of the consequences of our atmosphere is that light is bent as it comes in from space; air acts like a huge lens. The closer an object is to the horizon (like the sun at sunset or sunrise) the more the bending is apparent. This is because the light at these low angles must pass through much more air to reach us. It acts as a thicker lens closer to the horizon.

The consequence of this bending of sunlight is that the time something actually happens in the sky is not necessarily the time we see it happening from our vantage point under the atmosphere. In fact, this bending is enough that at the horizon it’s enough to make the sun appear to be more than its own diameter “earlier” in rising than it would without the atmosphere there. A staggering thought – when we see the sun just getting up over the horizon in the morning, it’s actually still below the horizon geometrically!

The other factor is the apparent size of the sun. From the earth’s perspective the sun is about a half a degree across, compared to the whole 360 degrees of the sky. Sunrise and sunset do not happen instantaneously. Sunrise is defined as the moment that the sun’s disk just appears on the horizon for any particular morning. Sunset is defined as the moment when the last bit of the sun just disappears past the horizon from any particular location.

These two things combined are enough of an effect that the Equilux, the day that has equal hours and minutes of sun above and below the horizon, is about four days before the Vernal Equinox and about four days after the Autumnal Equinox in the area of Hamilton, Ontario. The timing of the Equilux may be different in your location. In 2013 the Spring Equilux – the date that daylight and nighttime hours are closest to being 12 and 12 – falls on 16 March. The corresponding Equinox this year takes place about 7:02 AM on 20 March.

In September 2013 the Autumnal Equinox, marking the official beginning of fall, is at 4:44 PM on the 22nd. The Fall Equilux, however, for Hamilton is on 25 September.

Sources:

  • Thanks to the on-line calendar of the Hamilton Amateur Astronomers for the Equilux and Equinox dates and times for 2013. http://amateurastronomy.org/
Copyright © David Allan Galbraith 2013

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

Looking Forward to 2013

There are always lots of things happening in astronomy. Here are some anticipated highlights for 2013.

In the Sky

On 28 April 2013 the planet Saturn will be at opposition – the closest approach that the ringed planet makes to us during the mutual orbits of earth and Saturn. Will be the best time during the year to look at Saturn with a telescope. There’s also a partial (“penumbral”) lunar eclipse on the 18th of October, which might be visible in Ontario.

Nice meteor showers show up every year, assuming that the weather cooperates. Here are some of the more prominent ones:

  • Just after New Year, on January 3-4, the Quadrantids Meteor Shower is at its peak. A dark location after midnight is recommended; find the constellation Bootes to find the expected radiant point.
  • In August, the Perseids Meteor Shower presents its peak on the 12th and the 13th. This is always a favourite meteor shower, with as many as 60 meteors per hour showing up.
  • November has the Leonids Meteor Shower, peaking on the 17th and 18th. This shower looks like it’s originating in the constellation Leo, and will be best viewed after midnight.
  • In December, weather permitting, the Geminids Meteor Shower has its peak December 13-14. Best viewing will be after midnight, in the east.

Perhaps the most anticipated sights in 2013 are two comets expected to make interesting – and possibly spectacular – shows. Comet 2014 L4 (PanSTARRS) is currently being watched by astronomers in the southern hemisphere, but by March it should reach its greatest brightness and be visible up here in the north (http://cometography.com/lcomets/2011l4.html). 2014 L4 (PanSTARRS) is predicted to peak at a magnitude near -0.5 between 8-12 March 2013 (like a very bright star). Like the vast majority of comets, it will come no where near to the earth, never getting any closer than 0.3 AU – a third of the distance from the earth to the sun. By late May it should be very high in the night sky in the north – perhaps 5 degrees from Polaris – but will be much fainter too.

Great Comet of 1680.

A German engraving of the Great Comet of 1680. Some sources are prediction that Comet C/102 S1 (ISON) will be as spectacular… but only time will tell.

Also eagerly anticipated is Comet C/2012 S1 (ISON), (http://cometography.com/lcomets/2012s1.html). It was discovered this past September and might (emphasis might) be one of the greatest comets of recent memory. It will dip very close to the sun – about 0.1 AU or one tenth of the way from the earth to the sun – and may reach its maximum brightness on 28 November 2013. While very hard to predict, the size and orbit of the comet has some astronomers predicting a magnitude (brightness) of -13 for this beast. That’s brighter than the full moon! It may also have a very long tail. As comets are best described as irregular, big dirty snowballs, just how they behave when the sun starts to heat them up and generate their tails and other features is impossible to predict with precision. I’ll post updates (as will everyone interested in the sky, I’m sure!) as they become available.

(source of 17th C. illustration: http://ksj.mit.edu/tracker/2012/10/kehouflop-redux-out-near-saturn-monster).

On the Ground

This year the Hamilton Amateur Astronomers is hosting ASTROCATS 2013: The Canadian Astronomy Telescope Show, May 25th & 26th at the Sheridan College Athletics Centre, Oakville, Ontario. Unfortunately yours truly can’t attend, but it should be a great show, with a lot of vendors representing the best in astronomy gear (come to think of it, it’s likely a GOOD THING I can’t go. The national debt couldn’t take the strain): http://astrocats.ca/.

SkyFest is the annual three-day event put on by the North York Astronomical Association. August 8-11, 2013, held at River Place Park, RR 3, Ayton, Ontario (northwest of Mount Forest). It’s Canada’s biggest star party: http://www.nyaa.ca/index.php?page=/sf13/sf.home13.

Enjoy Winter Solstice 2012!

It’s the moment of the Winter Solstice, an event that has both cultural relevance around the world and is an element of a real science (Astronomy). Read something meaningful today, like Ann Druyan and Carl Sagan’s “The Demon-Haunted World: Science as a Candle in the Dark.” (http://books.google.ca/books/about/Demon_Haunted_World.html?id=5QpLlsPPM_YC&redir_esc=y)

Today (21 December 2012) was hyped onto a cottage industry of world-wide catastrophe by a few self-interested charlatans who prayed on the gullible. It’s a very, very old story. Carl Sagan has been quoted as saying that extraordinary claims require extraordinary evidence. The whole proposition that an ancient Mayan calendar foretold that today would be the end of the world was based on less than evidence – just a misinterpretation of an ancient document. This was not the first time, or the last time, that whole industries will be built on taking ancient texts and cooling up some baloney about their inferred meaning for the future.

There is only one knowledge system that can make evidence-based predictions about the future, and that’s science. Furthermore, the method of science is dependent on putting out predictions and then testing them against nature. In science, a failed prediction just means that the hypothesis upon which it was based was falsified – it didn’t work, and we try again. In chicanery a failed prediction has no consequences, except that it’s further evidence that, as is attributed (without evidence that he said it) to P. T. Barnum, “There’s a sucker born every minute.” It’s sad. The universe is beautiful, mysterious, and rich beyond the imaginings of any of us, modern or ancient. Get to know it for itself. Look for yourself, ask questions for yourself. Get to understand. Reject what doesn’t work. And – surprise – you will be applying the scientific method yourself. It’s not about believing in anything except that the evidence you can trust is evidence that has passed the test of being put up against the touchstone of nature.

© 2012, David Allan Galbraith