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Archive for February, 2016

02/29/2016 – Ephemeris – Yea! It’s the Leap Day.

February 29, 2016 Comments off

Ephemeris for Monday, February 29th.  The Sun will rise at 7:21.  It’ll be up for 11 hours and 8 minutes, setting at 6:29.   The Moon, 1 day before last quarter, will rise at 1:19 tomorrow morning.

Today is one of those special days that only occur once every 4 years.  It’s the intercalary or leap day that compensates for that fact that the earth takes 365 and nearly a quarter day to orbit the sun.  That orbit is a year, and those quarter days are accumulated and added as the last day of February on years divisible by 4.  The Gregorian reform makes a slight adjustment on most century years, making century years not divisible by 400 ordinary years to keep the calendar in sync with the seasons.  The Romans, from who we’ve gotten our calendar considered the month of February as unlucky, and so shortened it.  Enjoy your extra day today, too bad it’s a Monday.  My bobmoler.wordpress.com blog post from yesterday explains it in more detail.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

 

02/28/2016 – Ephemeris Extra – The years of our lives

February 28, 2016 1 comment

The continuing story of a small planet revolving around its star

Updated from the originally published in the January 1997 Stellar Sentinel, the monthly newsletter of the Grand Traverse Astronomical Society and republished in the February 2016 edition.

This year, 2016, is a leap year.  In leap years we have the US presidential elections, the Summer Olympic Games, and February has 29 days.  So what exactly is a leap year, and why am I writing about this earthly phenomenon in an astronomical society newsletter?  Well it’s astronomical of course. And if you think a year is a year is a year, well think again.
The calendar we use today is based on the Sun.  In ancient times the calendars of the Babylonians, Jews and many other ancient civilizations were based on the Moon, using the lunation, the period of about 29.5 days between new moons, as the basis for the calendar.  Lunar calendars tended to have months alternating 29 and 30 days, and years of 12 or 13 months to keep the whole scheme roughly in sync with the seasonal year.  There are vestiges of this system today in the various folklore of planting by the Moon.

The ancient Egyptians actually used two calendars.  The first was one based close to the sun and had 365 days.  It had 12 months of 30 days, each containing three 10 day decans.  There were 5 days at the end of the year that were holidays, and belonged to no month.  This civil calendar was used for state and accounting purposes.  The agricultural calendar was based on the Moon.  These two calendars were reconciled every 25 civil years which equaled 209 lunations, divided into 16 ordinary 12 month years, and 9 ‘great’ years of 13 months.  Still, since the Egyptian civil year is nearly a quarter of a day a year short, the civil calendar shifted slowly in relation to the seasons.  The Egyptian agricultural year started with the flooding of the Nile, which in those days was coincident with the heliacal rising of the brightest night time star Sirius, which they called Sothis.  A heliacal rising is when a star or planet is first visible in the morning twilight.  This heliacal rising occurs at a mean interval of 365.2507 days.  Thus the Egyptian civil calendar would be in sync with the agricultural year every 1460 years, a period called the Sothic Cycle.

The ancient Greek calendars were lunar ones.  Early on, each locality had their own calendar.  Starting in the 6th century BC the calendar situation got better when a cycle synchronizing lunar calendars with the sun was discovered.  It is the Metonic Cycle, probably discovered in Babylon.  Here 19 years of 365.25 days equal almost exactly 235 lunations.  That’s 12 ordinary 12 month years and 7 ‘great’ years of 13 months.  We find remnants of the Metonic Cycle with the Golden Number for the year given in almanacs, a number ranging from 1 to 19.  This year’s Golden Number is 3.  The year 1 BC was 1.  Under the old Julian calendar it was use to help determine the date of Easter.

The Julian Calendar is named for Julius Caesar who instituted it as a part of calendar reform he instituted in 46 BC.  The old Roman calendar was a lunar one, but in the earlier years of Julius Caesar’s reign the adjustments, called intercalations, such as 13th months in some years to keep the calendar roughly attuned to the sun, were neglected.  To straighten all this our, the year 46 BC was made 445 days long.  Starting in 45 BC the new calendar was instituted using the year of length 365.25 days.  Each 4 years an intercalary day was added.  This was February 29th, giving a 366 day year.  This we call a leap year.  Year 45 BC was a leap year, but due to some misunderstanding about the calendar reform, the one leap year in every four, was not kept.  In fact too many leap years were added, so in Caesar Augustus’ reign leap years from 8 BC to AD 8 were omitted to get back on track.

The western world ended up adopting the Julian calendar, and it was humming along just fine with leap years every 4 years.  However the Catholic Church and Pope Gregory XIII became alarmed that Easter was in danger of no longer being a spring feast.  The early church, adopted the Julian calendar rather than the Jewish lunar calendar.  But the most important feasts, the Crucifixion and Easter were tied to the Jewish feast of Passover, a spring feast starting in the middle of the month at full moon time.  Part of the problem was that the Vernal Equinox for ecclesiastical purposes was assumed to fall on March 21st, whether it actually did or not.  The first Sunday after the first full moon was Easter.

The problem is that the seasonal or tropical year is 11 minutes and 14 seconds shorter than the Julian year of 365.25 days.  In 400 years this amounts to about 3 days error.  So the easy correction is to eliminate 3 leap years out of 400 years.  The formula is simple.  All years divisible by 4 are leap years except century years which are not also divisible by 400.  Thus the year 1900 was not a leap year, but 2000 was, and 2100 will not be.

The other part of the reform was harder to swallow.  It was the elimination of 10 days because the real Vernal Equinox was by the 16th century falling on March 11th.  The Church was able to have this adopted in Catholic countries right away, so in the calendar of 1582 ten days were omitted between October 4th and 15th.  Protestant countries generally followed suit later.  England and the American Colonies converted to this new Gregorian Calendar in 1752 when by then 11 days were omitted between September 2nd and 14th.  The last to convert to the Gregorian Calendar was Greece and Orthodox Christianity who also made further improvements for the future.

I had once investigated how Microsoft Excel spreadsheets store dates.  It’s stored as a consecutive date starting with date 1 on January 1, 1900.  I had to convert dates downloaded from an IBM AS400 computer into a format compatible with Excel.  The dates came one day off.  It turns out that Microsoft or whoever devised the Excel dating scheme forgot that the year 1900 was not a leap year in the Gregorian calendar.  For my astronomical research I use dates both far in the past I use dating algorithms that use the Julian and Gregorian calendars where appropriate and takes into account the Gregorian discontinuity of 1582 into account.  These algorithms convert calendar dates to another type of consecutive day scheme called Julian Day Numbers of Julian dates for short, and back again.  In astronomy we see cycles of planetary orbits, variable star periods, etc.  They don’t fit into our hodgepodge of different month and year lengths.  We just want to know how many days between event A and event B.  Julian dates work for us.  The Julian dates start on January 1, 4713 of the Julian calendar, which predates any known historical date.  Oh by the way:  Julian dates start at noon Universal Time (UT) or Greenwich Mean Time (GMT), and fractional days are decimal.
I didn’t even touch when the year begins.  In Great Britain when the 1752 reforms took place they also changed the start of the year from March 25th to January 1st.

Bibliography

  • The Exact Sciences in Antiquity by O.  Neugbauer. Dover Publications
  • Explanatory Supplement to the Ephemeris H.M. Nautical Almanac Office

02/26/2016 – Ephemeris – The lion roars into the evening sky

February 26, 2016 Comments off

Ephemeris for Friday, February 26th.  The Sun will rise at 7:26.  It’ll be up for 10 hours and 59 minutes, setting at 6:25.   The Moon, half way from full to last quarter, will rise at 10:27 this evening.

Besides the advancing sunset times, there is another sign that spring is coming.  That’s the appearance of the constellation Leo the lion rising in the east in the evening.  The front of this beast is a backward question mark of stars with the bright star Regulus as the dot at the bottom.  That’s his head, mane and chest.  His haunches are a triangle of stars to the lower left, the last star is in the east above brilliant planet Jupiter. just clearing the horizon at 9 p.m.  One way to find Leo is to remember that cat’s aren’t supposed to like water, though mine have always had a certain fascination with the toilet.  Find the Big Dipper standing on its handle and imagine drilling a hole in the bottom of the bowl.  The water, falling from the north, will fall on Leo’s back.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Finding Leo

How to find Leo with Jupiter and the Big Dipper. At 10 p.m. on February 26, 2016. Created using Stellarium and GIMP.

02/25/2016 – Ephemeris – The Crab and the Beehive

February 25, 2016 Comments off

Ephemeris for Thursday, February 25th.  The Sun will rise at 7:27.  It’ll be up for 10 hours and 56 minutes, setting at 6:24.   The Moon, 3 days past full, will rise at 9:29 this evening.

At 9 this evening, the faint constellation, and member of the Zodiac, Cancer the crab will be located in the southeastern sky half way between the bright stars Castor and Pollux of the constellation Gemini, high in the south and the bright star Regulus in Leo the lion and Jupiter in the east.  Cancer is very dim, looking like an upside-down Y.  In the center of Cancer is a fuzzy spot to the unaided eye.  In binoculars or a low power telescope this fuzzy spot becomes a cluster of stars.  It is Messier 44 or the Beehive star cluster.  At 577 light years away, it is one of the closest star clusters, but more distant than the Pleiades and Hyades the face of Taurus the bull.  Of the three the Pleiades is the youngest at 100 million years.  The Beehive is 7 times older.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cancer Finder Chart

Cancer Finder Chart. Created using Stellarium.

The Beehive

The Beehive star cluster, M44, a great binocular object. Its ancient name was the Praesepe or manger when glimpsed by the naked eye as a fuzzy spot. Created using Cartes du Ciel (Sky Charts)

02/24/2016 – Ephemeris – The planets are all hanging out in the morning for another 2 weeks

February 24, 2016 Comments off

Ephemeris for Wednesday, February 24th.  The Sun will rise at 7:29.  It’ll be up for 10 hours and 53 minutes, setting at 6:23.   The Moon, 2 days past full, will rise at 8:31 this evening.

Let’s check out the whereabouts of the bright naked eye planets.  All the classical planets visible from antiquity are officially now in the morning sky.  Though Mercury is too close to the Sun to be spotted.  Jupiter will rise at 7:25 p.m., in the east.  Jupiter is still a morning planet since it’s not up at sunset.  It’s among the stars of Leo.  Mars will rise next at 1:12 a.m. in the east-southeast.  It’s seen against the stars of Libra now.  Saturn will rise at 2:49 a.m. in the east-southeast.  It’s above the stars of Scorpius, actually in Ophiuchus.  Venus will rise at 6:27 a.m. again in the east-southeast.  Comet Catalina is up all night and is a telescopic object and fading fast.  At 10 p.m. is above the constellation of Cassiopeia and right of Perseus.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter and the Moon

Jupiter, the Moon in the official constellation boundaries as set up by the International Astronomical Union at 10 p.m. February 24, 2016. Created using Stellarium.

Telescopic Jupiter

Jupiter and its moons as they would be seen in a telescope, at 10 p.m. February 24, 2016. Jupiter has an apparent diameter of 44.2″ Created using Stellarium.

Moon in binoculars

The Moon as it might be seen in binoculars at 10 p.m. February 24, 2016. Created using Stellarium.

Morning planets

The morning planets with constellation boundaries at 7 a.m. February 25, 2016. Created using Stellarium.

Telescopic Mars

Mars in a telescope at high power. It’s apparent diameter is 8.4″. At 7 a.m. February 25, 2016. Created using Stellarium.

Telescopic Saturn

Saturn and its large satellite Titan and other moons as they should appear in a telescope in the morning of February 25, 2016. The planet is 16.4″ in diameter while the rings span 38.2″. Created using Stellarium.

The telescopic planet images are not to the same scale.  Use the diameters in seconds of arc (“) as a way to compare the sizes.

Comet Catalina has become too faint to be seen in binoculars as it heads out of the solar system.  To follow the comet further go to Seiichi Yashida’s Weekly Bright Comets page. Comet Catalina is n longer the brightest comet on the list, and is currently listed second.  Click on it [C/2013 US10 ( Catalina )] for finder charts and other information.

Planets in the morning and the evening

This is a chart showing the sunrise and sunset skies for February 24, 2016 showing the location of the planets and the Moon at that time. Created using my LookingUp program.

Some of these images above are shown smaller than actual size.  Image expansion lately hasn’t worked.  If you are using Firefox, right-click on the image, and then click on View Image.

02/23/2016 – Ephemeris – The king of the planets is planning to conquer the evening sky. Tonight its enlisting help from the Moon.

February 23, 2016 Comments off

Ephemeris for Tuesday, February 23rd.  The Sun will rise at 7:31.  It’ll be up for 10 hours and 50 minutes, setting at 6:21.   The Moon, 1 day past full, will rise at 7:32 this evening.

Rising with the Moon tonight will be the planet Jupiter which will appear to the left of the Moon as they rise, to the upper left of the  Moon at 10 p.m. and above the Moon at midnight.  NASA’s Juno spacecraft, launched in 2011, is planned to arrive at Jupiter on July 4th this year.  No, it’s not a coincidence.  It will orbit the planet for nearly two years.  It’s the only solar-powered spacecraft that can operate as far from the Sun as Jupiter, which is 5 times farther from the Sun as the Earth, which gets one 5th squared or one twenty-fifth the intensity of sunlight.  It has 3 huge solar panels making the spacecraft 66 feet wide.  It’s mission is about Jupiter, its internal structure, atmosphere and magnetic and radiation fields.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter and the Moon

Jupiter and the Moon animation. Note their change in position relative to each other at 8 p.m., 10 p.m. and midnight. Created using Cartes du Ciel (Sky Chart) and GIMP.

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Closeup of Jupiter and the Moon

Closeup of Jupiter and the Moon at 10 p.m., February 23, 2016. The Moon is a whole lot brighter, and Jupiter dimmer than what’s shown here. Created using Stellarium.

Juno Spacecraft

The Juno spacecraft. Credit: NASA.

02/22/2016 – Ephemeris – Actual gravitational waves detected!

February 22, 2016 Comments off

Ephemeris for Monday, February 22nd.  The Sun will rise at 7:32.  It’ll be up for 10 hours and 47 minutes, setting at 6:20.   The Moon, at full today, will rise at 6:32 this evening.

On February 11th the LIGO team announced the discovery of gravitational waves coming from two black holes merging over a billion light years away.  LIGO stands for Laser Interferometry Gravitational-wave Observatory.  Two interferometers, one in the state of Washington, and the other in Louisiana detected the same signal milliseconds apart.  An interferometer sends a split light beam onto two paths 90 degrees apart to strike mirrors and return to interfere with itself.  A minute change in the length either light path will show up as a change in the interference.  The maximum change was one-one thousandths of the diameter of the proton subatomic particle.  This is a greater discovery than the Higgs Boson of a few years ago.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Lousiane LIGO Detctor

A view of the LIGO detector near Livingston, LA. Credit LIGO.org.

Gravitational Waves Detected

The chirp heard ’round the world and indeed the universe. Credit: LIGO/Abbot et al. 2016. Hat tip: Phil Plait, the Bad Astronomer.

02/19/2015 – Ephemeris – Jupiter is beginning to take its rightful place as king of the evening sky

February 19, 2016 Comments off

Ephemeris for Friday, February 19th.  The Sun will rise at 7:37.  It’ll be up for 10 hours and 38 minutes, setting at 6:16.   The Moon, 3 days before full, will set at 6:10 tomorrow morning.

Jupiter is becoming noticeable in the evening sky in the east after 8 p.m.  The heavy atmosphere near the horizon make telescopic observations difficult because the planet and its satellites will appear fuzzy and have color fringes top and bottom.  Wait an hour or two for the planet to rise higher into quieter and thinner air to get the best telescopic views.  Jupiter is accompanied by four moons in telescopes.  Tonight they’re on one side of Jupiter, with Io closest, then Europa and Ganymede close to each other, while Callisto as usual appears to be the farthest satellite.  The face of Jupiter itself is crossed by dark belts and light zones that run in the same direction as the satellites orbit.  The moons change position from night to night.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter, the Moon and stars tonight

Jupiter, the Moon and stars tonight at 10 p.m., February 19, 2016. Created using Stellarium.

This image is shown smaller than actual size.  Image expansion lately hasn’t worked.  If you are using Firefox, right-click on the image, and then click on View Image.

Jupiter Tonight

Jupiter and its moons tonight, 10 p.m. February 19, 2016. Created using Stellarium.

Jupiter and moons

Jupiter and its four Galilean moons. The planet has to be over exposed to pick up the moons. But the eye can handle the brightness difference with no problem. This is one of my old pictures I do believe.

Jupiter with its Great Red Spot

Jupiter with its Great Red Spot November 18, 2012 by Scott Anttila.

The above image by Scott Anttila is actually much better that the image seen in small telescopes.  Advances in digital photography and processing allow the stacking and averaging of many images to create better pictures by  amateur astronomers with modest equipment than the best telescopes of a quarter century ago.

02/18/2016 – Ephemeris – Castor and Pollux

February 18, 2016 Comments off

Ephemeris for Thursday, February 18th.  The Sun will rise at 7:39.  It’ll be up for 10 hours and 35 minutes, setting at 6:14.   The Moon, 3 days past first quarter, will set at 5:28 tomorrow morning.

The star Pollux is at the head of the same named brother of Gemini the twins.  Castor is the  slightly dimmer star right above it.  Pollux is about 34 light years away.  It’s twice as massive as the Sun, and has run out of hydrogen in its core and is in the process of evolving into a red giant star.  One planet, twice as massive as Jupiter has been detected around it.  Castor is at 51 light years away.  There are 6 stars in its system.  The brightest three are visible in telescopes.  Each is a spectroscopic binary, meaning that the companion stars are detected by the Doppler shifts of the lines in their spectra as the stars orbit each other.   The Doppler shift is just one of the many pieces of information revealed by the spectroscope.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Castor and Pollux

Castro and Pollux with the bright Moon and other bright stars and constellations of winter. 9 p.m. February 18, 2016. Created using Stellarium.

Castor star system

The Castor star system exploded in this JPL/NASA infographic.

The entire infographic is here.

Categories: Ephemeris Program, stars Tags: , ,

02/17/2016 – Ephemeris – All the bright planets are in the morning sky, but two of them are trying to sneak out

February 17, 2016 Comments off

Ephemeris for Wednesday, February 17th.  The Sun will rise at 7:40.  It’ll be up for 10 hours and 32 minutes, setting at 6:13.   The Moon, 2 days past first quarter, will set at 4:39 tomorrow morning.

Let’s check out the whereabouts of the bright naked eye planets.  All the classical planets visible from antiquity are officially now in the morning sky.  Though Mercury is too close to the Sun to be spotted.  Jupiter will rise at 7:57 p.m., in the east.  Jupiter is still a morning planet since it’s not up at sunset.  Mars will rise next at 1:24 a.m. in the east-southeast.  It’s brighter than the bright star Spica growing even farther to the right of it..  Saturn will rise at 3:40 a.m. in the east-southeast.  Venus will rise at 6:27 a.m. again in the east-southeast.  Mercury is too deep in the twilight glare to be seen.  Comet Catalina is up all night and is a binocular object and fading fast.  At 10 p.m. is above the constellation of Cassiopeia and right of Perseus.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter and he Moon

Jupiter, the Moon and the bright winter stars at 10 p.m. February 17, 2016. Created using Stellarium.

The Moon

The Moon as it might be seen in binoculars at 10 p.m. February 17, 2016. Created using Stellarium.

Jupiter and Moons

Jupiter and its moons as they would be seen in a telescope, at 10 p.m. February 17, 2016. Jupiter has an apparent diameter of 43.9″ Created using Stellarium.

Morning planets

Morning planets and the bright s tar preview of summer. Mercury, though labeled can’t compete with the bright twilight. Observers south of here may have better luck. At 7 a.m. February 18, 2016. Created using Stellarium.

Telescopic Mars

Mars in a telescope at high power. It’s apparent diameter is 7.9″. At 6 a.m. February 18, 2016. Created using Stellarium.

Saturn and its moons

Saturn and its large satellite Titan and other moons as they should appear in a telescope at 6 a.m. February 18, 2016. The planet is 16.2″ in diameter while the rigs span 37.8″. Created using Stellarium.

Comet Catalins track

Comet Catalina’s path for the next week. Note that it is fading fast. It will take binoculars or a small telescope to spot the comet which will not show a tail visually. Created using Stellarium.

Planets at sunrise and sunset

This is a chart showing the sunrise and sunset skies for February 17, 2016 showing the location of the planets, the Moon and Comet Catalina at that time. Created using my LookingUp program.

Some of these images above are shown smaller than actual size.  Image expansion lately hasn’t worked.  If you are using Firefox, right-click on the image, and then click on View Image.