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12/03/2020 – Ephemeris Interruptus – I’m in the hospital for tests

December 3, 2020 1 comment

Yesterday I developed some symptoms of the stroke I had last January and my daughter took me to the ER where I had a CT scan. I’m waiting on a early am MRI. I should be home later today. I hope to be finishing up my Zoom program In Search of the Star of Bethlehem. If you’re interested go to http://www.gtastro.org Friday. The program will start ar 8 pm EST, though you can join earlier with the GTAS business meeting in progress. I might get the 12/03 post up later in the day.

The audio Ephemeris programs will run on Interlochen Public Radio through Monday regardless of my health issues. They’re already in the can, so to speak.

11/17/2020 – Ephemeris – The Pleiades in legends from different cultures

November 17, 2020 Comments off

This is Ephemeris for Tuesday, November 17th. Today the Sun will be up for 9 hours and 29 minutes, setting at 5:12, and it will rise tomorrow at 7:44. The Moon, 2 days past new, will set at 7:23 this evening.

Let’s look at how some other cultures saw the Pleiades, the star cluster that is seen in the eastern sky these evenings. To the Anishinaabe native peoples around here the Pleiades is the “Hole in the Sky” or the seven stones that are heated for the sweat lodge ceremony. To the Kiowa these were sister stars that had been whisked into the sky from the top of Devils Tower in Wyoming where they were threatened by a huge bear. In Norse mythology these were the goddess Freya’s hens. The name we know them by has rather misty origins. Some think the Greek name is from the mother of the seven sisters, Pleione. The Greek word for sail is similar to Pleiades, and it seems the appearance of the Pleiades in the morning sky saw the best sailing weather in the Mediterranean.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Devil's Tower

Seven maidens being attacked by a giant bear, having fled to the top of Devil’s Tower in Wyoming. Painting by Herbert Collins, https://www.nps.gov/deto.

The Pleiades, about what you'd see in binoculars.

The Pleiades, about what you’d see in binoculars, more than the 6 or 7 stars visible to the naked eye. The brighter stars are Freya’s Hens and also the Seven Sisters and Indian maidens. Credit Bob Moler.

Pleiades finder animation

Pleiades finder animation looking east about 8 pm in mid-November. Created using Stellarium.

02/17/2020 – Ephemeris Extra – The Moon will cover the planet Mars in morning twilight tomorrow, Tuesday the 18th.

February 17, 2020 Comments off

Sorry, I missed this until now. Tomorrow morning the 18th Mars will be occulted by the Moon. For Northern Lower Michigan Mars will disappear shortly after 7:10 a.m. The exact time depends on your location, so I can’t be more specific.  At that time the Moon and Mars will be in the southeastern sky. Mars is now first magnitude, but will fare poorly in the morning twilight, so I’d suggest finding the Moon and Mars at least 15 minutes earlier with binoculars or telescope. Mars will reappear at the Moon’s unlit side around 8:37 a.m. This is after sunrise, so a telescope will be required to spot it.  Hoping for clear skies, though the weather forecast isn’t promising.

Occultation map

A map of where the occultation of Mars will be visible. Created using Occult4.

Mars Occultation Start

Where Mars will disappear at the Moon’s sunlit edge. Created using Stellarium.

Mars Occultation End

Mars will reappear at the Moon’s unlit edge around 8:36 a.m. give or take. Created using Stellarium.

02/10/2020 – Ephemeris Extra – Back again

February 10, 2020 4 comments

I’m now back home and will continue my therapy at home or as an outpatient.  I can now walk unaided but they’d prefer that I use a walker.  I want to thank the doctors, nurses, therapists and assistants at Mary Free Bed Rehabilitation at Munson Medical Center in Traverse City, MI for getting me back this far so fast.  I also want to thank those who called and wrote to Interlochen Public Radio about missing the program.  I missed it too.  The programs will air again starting tomorrow with a look at Mercury in the evening.  Also to those who wrote comments on this blog, I thank you.  It means a lot to me.

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01/20/2020 Ephemeris Extra – Ephemeris will be on a short hiatus

January 20, 2020 3 comments

On January 11th I suffered a stroke. It affected my left side and scrambled my brains a bit. I’m in Mary Free Bed Rehabilitation at Munson Medical Center in Traverse City, for a bit to get my left side talking better to my brain. I hope to be back in a month or so. Thanks for the messages of concern sent here and to Interlochen Public Radio.

Bob Moler

p.s. Yesterday’s SpaceX Crew Dragon inflight abort test looked pretty cool!

Categories: Ephemeris Extra

Ephemeris Extra – The Great Star Story of Autumn

September 18, 2019 Comments off
Autumn Star Story Constellations

The constellations of the great star story of autumn. Looking southeast on October 31 at 10 p.m. Created using Stellarium.

The great star wheel of the sky rolls on. In the evening sky gone are the stars of spring, and going are the southern stars of summer. In the morning sky before sunrise the stars of an early winter evening.

A constant in both skies are the stars of autumn: rising in the evening and setting in the morning. In no other part of the sky do so many constellations take part in a single story

The constellations, as seen above are Cepheus, Cassiopeia, Andromeda, Perseus, Pegasus, and Cetus. And their story goes like this:

In distant Ethiopia a crisis was brewing. King Cepheus and Queen Cassiopeia were at wits end as how to stop it. A giant sea monster named Cetus was ravaging the country’s coastal cities destroying them and devouring the inhabitants.

The king and queen consulted the temple oracle as to what happened and what could be done to save their country. The oracle intoned gravely that the fault was Cassiopeia’s. Suddenly the queen knew what happened. Cassiopeia was very beautiful and she had vainly boasted to all who could hear that she was more beautiful than even the sea nymphs, the lovely daughters of the sea god Poseidon.

The sea nymphs had heard of Cassiopeia’s boast and complained to their father. Poseidon, like any father, was angered, and being a god was able to do something about. Being a god means never having to say your sorry when you do something really mean. He loosed the monster Cetus upon the Ethiopians.

The oracle said that to appease the monster and Poseidon Cassiopeia would have to sacrifice her daughter the Princess Andromeda to the monster. That is how young Andromeda was chained to the rocks on the sea shore to await her doom…

Far away in ancient Greece a wedding was about to take place between the beautiful Princess Danaë and King Polydectes. Danaë’s son Perseus, fathered by Zeus, but that’s another story, wasn’t too happy about the proposed union, and Polydectes wanted the boy gone.

When Perseus asked Polydectes what he wanted for a wedding gift, he said, “I want the head of Medusa.” The boy immediately and foolhardedly agreed to get it for him.

Merdusa, it turns out, was one of three sisters, the Gorgons, who had snakes for hair. They were so ugly that one glimpse of them would turn the beholder to stone. Medusa was the only mortal one.

Luckily Perseus had the favor of the god Hermes and Athene. They armed him with Hermes’ winged sandals, a helmet that made him invisible, a pouch that would expand to hold an object of any size, a shiny mirror shield, and a sword.

Thus armed Perseus was told to find the Graiae or the gray women, who could tell him where the lair of the Gorgons was. They were three in number and shared but one eye and one tooth among them which they passed from one to another to use.

The Graiae refused to help Perseus. But he was able to force them to help by snatching their one eye while it was being passed from one to another. They told him that the Gorgons dwelt in the shore of the river Ocean at the edge of the world in perpetual twilight.

In approaching the lair of the Gorgons Perseus put on the helmet of invisibility. He approached Medusa stepping backwards, cautiously peering only at Medusa’s indistinct image in his shield. Perseus then swept his sword in a backhanded way and managed to sever Medusa’s head. It is said that Athene guided his hand.

Amazingly, springing full grown from Medusa’s blood was the winged white stallion Pegasus. After placing Medusa’s head in the pouch, Perseus mounted Pegasus for the trip home.

Cruising high in the sky over the Ethiopian coast Perseus spotted a horrific sight. There far below the beautiful Andromeda, in chains; her screams reaching his ears. Then he spotted why she was screaming. A short distance away, crawling out of the surf was the monster Cetus, heading towards Andromeda. Perseus immediately sizes up the situations and swooped with Pegasus down to a spot between Andromeda and the monster. Then, burying his head in his shoulder drew out the head of Medusa from the pouch and held it in front of Cetus. The head was as lethal in death as in life, and the monster was promptly turned to stone. Replacing the head in the pouch, Perseus freed Andromeda. They flew off to, well supposedly, live happily ever after.

Oh yes. Perseus did present the head of Medusa to his step father Polydectes. He, of course, was also turned to stone when he laid eyes on it.

There you have it a story connecting the autumn constellations of Cepheus, Cassiopeia, Andromeda, Perseus, Pegasus and Cetus.

Cepheus is a dim church steeple of a constellation. Its dim star Delta is a variable star, the prototype of an important class of distance measuring stars called Cephieds in its honor. Cassiopeia is the famous W shaped constellation that along with Cepheus doesn’t set at our latitude.

Perseus looks to me more like the cartoon roadrunner than a hero. As the ancients saw him, he is holding the head of Medusa, whose still glittering eye is the star Algol, a variable star which ghastly winks at us every 2 days and 21 hours.

Andromeda’s modern claim to fame is the great galaxy that lies beyond her stars, the Great Andromeda Galaxy which has the designation M31. The galaxy is faintly visible to the unaided eye on dark nights. The farthest you can see without optical aid. The galaxy lies some 2.5 million light years away.

Pegasus can be easily found by the square of stars the form his body. It’s called the Great Square of Pegasus.

What can be said about Cetus. It now represents a whale, not a monster. Its star Mira, which means “Wonderful”, slowly varies in brightness over 330 days from a star barely visible in binoculars to a 2nd or 3rd magnitude star.

Look up on an autumn evening and recapture the wonder the ancients had as they looked upward at the stars.

09/16/2019 – Ephemeris Extra – I’ll be giving my presentation “Apollo and the Moon Race” tonight

September 16, 2019 Comments off

I’ll be giving my illustrated talk Apollo and the Moon Race tonight at 7 p.m. at the Traverse Area District Library on Woodmere Avenue in Traverse City.  The 1960s were a heady time with the space race between the US and the USSR in achieving space firsts.  I will look at the competition, and the incremental steps that had to be made to finally send astronauts to the surface of the Moon on July 20th 1969.

If you miss this presentation, there will be another on Friday September 27, at 7 p.m. at the Betsie Valley District Library in Thompsonville.

Both events will have viewing of the skies with the Grand Traverse Astronomical Society including Jupiter and Saturn afterward if it’s clear.

 

 

Announcement: I’m offering to present Apollo and the Race to the Moon to schools, libraries and non-profits

July 2, 2019 Comments off

Apollo and the Race to the Moon is the story of the space race from Sputnik to Apollo 17 between the United States and the Soviet Union that traces the United States’ incremental steps and the Soviets’ rather disorganized approach that allowed the US to be the first on the Moon.  The presentation by yours truly will be illustrated by images and a short video.

I will be giving this presentation as a NASA/JPL Solar System Ambassador.  The presentation will be given free of charge for non-profit groups, libraries and schools.  I can be reimbursed for expenses if traveling over 50 miles from Traverse City, MI.  The presentation lasts a bit over an hour depending on the number of questions, which I welcome.

Apollo and the Race to the Moon Title

Apollo and the Race to the Moon Title slide

I’ve been an avid amateur astronomer and space enthusiast since before the launch of Sputnik, so I have lived through all these events.  For more information on me click on the About link above.  There’s even a timeline of my astronomy activities here.  The About link above contains a contact form where you can reach me.

 

Categories: Ephemeris Extra

05/06/2019 – Ephemeris Extra – The Eta Aquariids – Halley’s Comet never really left

May 5, 2019 Comments off

In 1986 Halley’s Comet swam through our skies for the 28th time since the Chinese first recorded it in 240 BCE. It was not especially impressive, considering the week when my family met a group of Leelanau School students in the Florida Keys the week in April 1986 to view and photograph the comet at it’s closest to the Earth of 44 million miles. It turned out that that week the comet lost its tail, probably due to a coronal mass ejection from the Sun. Halley’s Comet was much more impressive a month later. I’ve seen more impressive comets before and since.

Comet Halley's path thru the inner solar sstem

Comet Halley’s path through the inner solar system in 1985-86. Created using my LookingUp program.

Halley’s Comet has been swinging around the Sun countless times before the Chinese first recorded it. The illustration above shows the last time the comet entered the inner solar system in 1986. The comet’s path is from upper right to lower left. When the comet passes within about 3 astronomical units of the Sun, that is 3 times the Earth’s distance from the Sun, the ices in the comet begin to sublimate, escaping from the comet’s nucleus which liberates dust and larger solid material. The gasses and dust form the comet’s ion and dust tails. The larger material, gravel sized bits, end up in and around the comet’s orbit, and over time are spread out around and near the comet’s orbit. Halley’s orbit crosses the Earth’s orbit twice, inbound and outbound. In both cases these crossings are close enough to the plane of the Earth’s orbit to produce meteor showers.

On the inboard leg of the orbit it produces the Orionid meteor shower that peaks on October 22nd. A meteor shower is generally named for the point in the sky they seem to come from, be it a constellation or star. The point, called the radiant, moves during the days or weeks the shower is visible. The Orionids are named for the constellation Orion. The radiant is near his upraised arm.

The center of the outbound meteoroid stream crosses the Earth’s orbit where the Earth is on May 6th. Though they have a broad peak of about 5 days. This meteor shower is visible from April 19th to May28th. During that period the radiant points drifts quite a bit to the east. There are several meteor shower radiants in Aquarius, so they are named for the nearest star at peak.

Motion of Eta Aquariid Radiant

Motion of the Eta Aquariid radiant from April 20 to May 25. The triangle with the star near the center near May 05 is the asterism the Water Jar, a part of Aquarius. Eta Aquarii is the triangle star to the left. Source: PDF version of the International Meteor Organization 2019 Meteor Shower Calendar: https://www.imo.net/resources/calendar/

Though the Moon is new for this shower, the meteoroids are coming from near the direction of the Sun, so there is only an hour where the Eta Aquariids are best seen. For Northern Michigan the radiant rises at 3:30 a.m. on May 6th. Astronomical twilight begins at 4:30 a.m. when the sky begins to brighten. This meteor shower is best seen from the southern hemisphere.

02/02/2019 – Ephemeris Extra – Groundhog Day and other seasonal days

February 2, 2019 Comments off

Note:  I wrote this article as part of the Grand Traverse Astronomical Society’s Stellar Sentinel for February 2019.

Groundhog day coming this month got me to thinking about the seasons and those special seasonal days, like solstices, equinoxes and cross-quarter days. February 2nd is a cross-quarter day, supposedly when winter is half over. Below is a table I created of the seasons for one year starting with last December’s winter solstice.

I took the date and times from Astronomical Tables of the Sun, Moon and Planets, Third edition by Jean Meeus. TD is Dynamical Time, used to calculate the positions of bodies in the solar system, is about 68 seconds fast compared to Universal Time (UT), which is tied to the Earth’s rotation. The difference is slowly changing at less than a second a year and doesn’t enter into the calculations. The Julian Date is a consecutive date starting on January 1, 4713 BC at noon UT. It’s used by astronomers to calculate date differences. like the length column in the table above without worrying how many days months have or how many leap years are in the interval. If you want to convert a calendar date to a Julian date or a Julian date to calendar date go to the Naval Observatory web page here: https://aa.usno.navy.mil/data/docs/JulianDate.php.

Note that the seasons are of different lengths. This is because the Earth’s orbit is slightly elliptical. It reached perihelion, its closest to the Sun, this year on January 3rd, and it will reach aphelion, its farthest, on July 4th. The Earth or any planet moves fastest when near perihelion. And with perihelion 14 days into winter, makes winter the shortest season. Autumn is the second shortest season 90 days compared to winter’s 89 days. Summer at nearly 94 day’s length is 4.7 days longer than winter. However we’re too far north to really notice it. Spring is second with nearly a 93 day length.

The rest of this article is based quite a bit on the web page: Common Holidays in Relation to Equinoxes, Solstices & Cross-Quarter Days – https://www.naic.edu/~gibson/cal/. It’s a cool list. Naic.edu is the website of the Arecibo Observatory in Puerto Rico. Apparently it was someone’s (Gibson’s) personal post.

The equinoxes and solstices are quarter days, for the four seasonal quarters of the year. The table above has Mid-Season and Date for the half way point in the season. The Cross-Quarter Days column are the dates which are more or less celebrated down throughout history.

The first celebrated cross-quarter day is February 2nd, Groundhog Day Which the famous weather prognosticating rodent in Punxsutawney, PA forecasts the length of winter based on if he sees his shadow. Supposedly, if he sees his shadow winter will last for six more weeks, if he doesn’t then spring is just around the corner. Actually from February second to the vernal equinox is six and a half weeks. If we had a winter like last year with a snowy April, winter lasted until the second cross-quarter day. The actual first cross-quarter day this year is February 4th. February 2nd, 40 days after Christmas, is also celebrated as Candlemas Day, when candles are blessed for the year, and the Feasts of the Purification of the Virgin Mary and The Presentation of the Child Jesus by the Catholic and some other Christian Churches.

The first quarter day is the vernal equinox, which occurs in our time zone on March 20th. The Ides of March, the 15th is pretty close to the vernal equinox and was the start of the year for a time with the Romans. It was the date in 44 BC that Julius Caesar was assassinated. March, named after the god Mars was also for a long time the first month of the year. They, for a time had 10 months, and consigned the winter months to ?. Later they added two months in front of March, which is why our 9th through 12th months are named September (7), October (8), November (9) and December (10).

The second cross-quarter day to be celebrated is May 1st, May Day. The actual 2nd cross-quarter day this year is May 6th.

The second quarter day, the summer solstice is on June 21st. It’s near midsummer day, the 24th, the feast of St. John the Baptist. It’s a big deal in Europe. If you had a midsummer’s night dream it would be on the night of June 23-24. Of course if that date was really midsummer, summer would have to start in early May.

The third cross-quarter day is August 1st, Lughnasadh. This is Celtic. It was the wedding day of Lugh, their sun god with the goddess of the Earth. This causes the crops to ripen in time to harvest in the fall. The actual date this year is August 7th.

The third quarter day is the autumnal equinox. This year it’s on September 23rd.

The fourth cross-quarter day is celebrated on October 31st, Halloween. It is the day before All Saints Day, and Day of the Dead in Mexico. The actual cross-quarter day this year is November 7th.

The fourth quarter day is the winter solstice, December 21st. This is in the midst of festivals ancient and modern around the time the Sun starts heading north again. Festivals of light, like Saturnalia, Yule, Christmas, and Hanukkah

There you have the days of our seasons.

Categories: Ephemeris Extra, Seasons