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03/08/2019 – Ephemeris – International Women’s Day

March 8, 2019 1 comment

Ephemeris for International Women’s Day, Friday, March 8th. Today the Sun will be up for 11 hours and 31 minutes, setting at 6:39, and it will rise tomorrow at 7:06. The Moon, 2 days past new, will set at 8:43 this evening.

On this International Women’s Day let’s take a look in my favorite fields of astronomy and space. There’s Hypatia of Alexandria who was murdered by an ignorant mob in 415 AD, Caroline Herschel sister to William Herschel and among other things discovered 8 comets, Maria Mitchell, whose comet discovery rocketed her to fame in the United States in the 1800s, Annie Jump Cannon, who classified stars, Henrietta Leavitt who found how to find distances to far away galaxies, and Vera Rubin who helped discover dark matter. In space there’s Sally Ride, Mae Jamison, and Peggy Whitson, who holds the American space flight time, and EVA time records regardless of gender. And that’s just scratching the surface.

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

Addendum

Ten female astronomers everyone should know:  https://www.mnn.com/leaderboard/stories/10-female-astronomers-everyone-should-know.

My favorite astronomer on Twitter is astrophysicist Dr. Katherine J Mack @AstroKatie.

 

 

12/20/2019 – Ephemeris – The Star of Bethlehem, the problem of when

December 20, 2018 Comments off

Ephemeris for Thursday, December 20th. The Sun will rise at 8:16. It’ll be up for 8 hours and 48 minutes, setting at 5:04. The Moon, 2 days before full, will set at 6:46 tomorrow morning.

In looking at the possible origin of the Star of Bethlehem, the latest Jesus could have been born is before the death of Herod the Great. The Jewish historian Josephus says that Herod died between a lunar eclipse and Passover, with most Star investigators pointing to the partial eclipse of March 13, 4 BC, one month before Passover that year. Problem is that Josephus devotes 4 chapters of the 17th book of Jewish Antiquities to the events in that span. I think they chose that eclipse to fit in with the triple conjunction of Jupiter and Saturn in 7 BC that was the big favorite for the star. There is another, better total lunar eclipse on January 10, 1 BC that is 3 months before Passover that would better fit Josephus’ narrative and a different Star possibility. More Monday.

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

Addendum

The passage about Herod’s death from the eclipse of the Moon to Passover is in Josephus’ Antiquities of the Jews is in Book 17, Chapter 6, Paragraph 4 through Chapter 9, paragraph 3.

In doing some additional research since recording the program, the footnotes in William Whiston’s translation suggests a period between the eclipse and Passover at 13 months.  Antiquities of the Jews can be found here: https://www.gutenberg.org/files/2848/2848-h/2848-h.htm.  Of course I could extend the time frame of Herod’s death for the 1 BC eclipse to the Passover 16 months later.  That would solve one of the problems I had with the timing of the visit of the Magi.  But you’ll have to wait until Monday to find out what that is.

07/24/2018 – Ephemeris – What about those martian canals

July 24, 2018 Comments off

Ephemeris for Tuesday, July 24th. The Sun rises at 6:20. It’ll be up for 14 hours and 57 minutes, setting at 9:17. The Moon, 3 days before full, will set at 4:25 tomorrow morning.

The greatest mystery of the late 19th and early 20th century of Mars was the discovery of fine linear marking seen by visual observers of Mars. They were first reported by an Italian astronomer Giovanni Schiaparelli in 1871 as grooves, canali in Italian. It was turned into canals by the English language newspapers of the day. Canals are artificial constructions. Thus one Percival Lowell of Massachusetts built an observatory in Flagstaff Arizona to observe and map Mars for himself, dying in 1916 still believing in an ancient martian civilization bringing water from the polar caps to the equatorial region by canals in order to survive. Alas, there are no canals. Mars is a barren world, whose secrets we now probe below its red dust.

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

Addendum

The source if the images below is the talk “Mars 2018” I gave at the Betsie Valley District Library, July, 20, 2018.

Shiaparelli

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07/23/2018 – Ephemeris – The importance of Mars in determining the nature of the solar system

July 23, 2018 Comments off

Monday, July 23rd. The Sun rises at 6:19. It’ll be up for 14 hours and 59 minutes, setting at 9:18. The Moon, half way from first quarter to full, will set at 3:41 tomorrow morning.

The accurate observational positions of Mars by Tycho Brahe allowed Johannes Kepler in the early 17th century to discover his three laws of planetary motion. Tycho was the last and greatest of the naked eye astronomers. Kepler befriended Tycho who jealously guarded his observations. It was only after his death in 1601 that Kepler took possession of Tycho’s data. Until then it was believed that planets moved with uniform circular motion, even though they didn’t look like it. Astronomers added circle after circle, called epicycles, to attempt to make their system work. Mars was the worst case. Kepler finally determined that Mars, and indeed all the planets, orbited the Sun in elliptical orbits. That was his first law of planetary motion.

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

Addendum

The source if the images below is the talk “Mars 2018” I gave at the Betsie Valley District Library, July, 20, 2018.

Tycho and Kepler

Tycho and Kepler. Artist for Tycho: Eduard Ender (1822-1883). Artist for Kepler, unknown. Source: Wikipedia.

Mars and Earth's orbits

Mars’ and Earth’s orbits to scale and positions of the Earth and Mars July 20, 2018, one week before opposition. Note that Mars’ orbit is decidedly not circular. Credit my LookingUp program.

Retrograde Mars Path 2018

Created using Cartes du Ciel (Sky Charts).

Retrograde motion explained

Created using Cartes du Ciel (Sky Charts).

06/24/2018 – Ephemeris Extra – Mars Summers

June 24, 2018 Comments off

This is a reprint of “Mars Summer” which I wrote for the Grand Traverse Astronomical Society newsletter Stellar Sentinel’s June 2018 issue.

The planet Mars has oppositions from the Sun about every 26 months more or less. These oppositions are a time when Mars is closest to the Earth for its position in orbit. It’s distance at these times range from 34.6 to almost 63 million miles, a range of almost 2 to 1. This is because Mars has a very elliptical orbit as can be seen below.

Mars closest approaches

Mars closest approaches to the Earth from August 27, 2003 to July 31, 2018. Diagram created using Bob Moler’s LookingUp program.

Especially close approaches to the Earth occur every 15 or 17 years in the latter half of summer in those years. My first close approach was September 7, 1956. It was a famous one for the time. Professional astronomers of that time were pretty sure that Mars didn’t have canals, features that were ‘discovered’ by Giovanni Schiaparelli in 1877. To him the features were grooves or channels. Unfortunately the Italian word for them was canali. The world press proclaimed that there were “canals” on Mars. Canals by definition are artificial and require canal builders, Martians by inference.

Like I said, professional astronomers had discounted them by 1956. But science fiction read by young impressionable amateur astronomers like myself talked about old races of Martians hoarding every last drop of water. So maybe we believed. With my 5 inch reflector I observed the polar cap and the large dark feature Syrtis Major.

My next close approach of Mars was August 12, 1971. That summer I was working out of town and in the midst of a move from Grand Rapids to Traverse City, so was unable to observe Mars properly.

In the summer and autumn of 1973 I was able to do an observing program of Mars when it was almost as close as in 1971, drawing its features. I found out that to really observe a planet it takes time to educate the eye and brain to see faint, fuzzy detail. And since I didn’t believe in canals by this time, I didn’t see them.

The next close approach was September 22, 1988. The first “Mars Night” held by the society. We had a great turnout. But Mars was tiny as seen in telescopes. At best it was 23.81 seconds of arc in diameter. The Moon and Sun are about 1,800 seconds in diameter. It would be a bit larger than half the apparent diameter of Jupiter at average distance.

On August 27, 2003 Mars came closer than at any time in 50,000 years some astronomers said. The society held its second “Mars Night” at the Rogers Observatory, and wow, the lines of people ran down the drive and onto the shoulder of the road. As in 1988, I was stationed on the lawn at the front of the observatory with the portable Celestron 11 telescope, which actually gave clearer views than the 14 inch telescope in the dome. (Hot bodies in dome make for lousy seeing.)

2003 is also memorable or rather infamous for the “Mars Hoax” email. Proclaiming that Mars would appear as large as the Moon on August 27th. This hoax has been propagated every two years since. I expect 2018 to be a banner year for the resurrection of the hoax.

We come to this year, 2018, 15 years after the 2003 closest approach. Mars will reach opposition on July 27th. It’s closest approach to the Earth will be on July 31st, at the distance of 35,784,000 miles. The reason the dates aren’t the same is that Mars will still be a month before reaching perihelion, its closest to the Sun, so it’s getting even closer than at the time of opposition.

The Mars oppositions of October 2020, December 2022, January 2025 and February 2027 will be of increasing distances up to 63.0 million miles. This will be followed by oppositions of decreasing distances in March 2029, May 2031, and July 2033 leading to another close approach on September 11, 3035 at 35.4 million miles.

However by 2035 there may be humans on Mars waving back at us. It’s odd that anyone on Mars at the time probably wouldn’t be able to see the Earth at that time. Martian oppositions for us, are the time of inferior conjunctions of Earth with the Sun. We’d be lost in the Sun’s glare.
For the very closest views of Mars get on the Internet and search for Mars Curiosity, Mars Opportunity and Mars Hirise. No telescope required.

05/21/2018 – Ephemeris – 408 years ago Galileo discovered that Jupiter had moons

May 21, 2018 Comments off

Ephemeris for Monday, May 21st. Today the Sun will be up for 15 hours and 2 minutes, setting at 9:10, and it will rise tomorrow at 6:07. The Moon, at first quarter today, will set at 2:55 tomorrow morning.

Jupiter is the bright star-like object in the southeast in the evening. In telescopes and even in binoculars the observer can spot up to four stars nearby. These aren’t stars, but moons or satellites of Jupiter. Galileo discovered them 408 years ago with his small telescope. Jupiter has 69 satellites in all at last count, but the rest are tiny objects. Of the four ‘Galilean’ satellites all but one is larger than the Moon. They are, in order from Jupiter Io, a volcano riddled world which is constantly resurfacing itself. Next is Europa an icy moon with a good probability of a salty ocean beneath. Giant Ganymede is next, larger than Mercury, it is also icy with the possibility of an ocean. Last is Callisto a dark moon with bright craters.

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

Addendum

Galileo's moons

Multiple night sightings of Jupiter’s moons by Galileo.

Jupiter and its moons tonight

Jupiter and its moons tonight, May 21, 2018. Created using Cartes du Ciel (Sky Charts).

05/04/2018 – Ephemeris – Tonight I present Venus from the mists of time to today

May 4, 2018 Comments off

Ephemeris for Friday, May 4th. The Sun rises at 6:28. It’ll be up for 14 hours and 23 minutes, setting at 8:51. The Moon, 3 days before last quarter, will rise at 1:15 tomorrow morning.

The planet Venus is our evening star now. I’ve been talking about it on this program lately. Want to hear and see more? Tonight at 8 p.m. at the May meeting of the Grand Traverse Astronomical Society at Northwestern Michigan College’s Rogers Observatory, I will be giving an illustrated talk: Venus from the mists of time to today. To the early Greeks it was two planets. To the Maya it was a calendar. In the 18th century it was a way to measure the size of the solar system. Today, it could be what our future looks like. After the meeting, at 9 p.m. the society will host a star party to view the planets Venus and Jupiter. The observatory is located south of Traverse City on Birmley Road between Garfield and Keystone roads.

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

Addendum

Venus section of the Dresden Codex

5 Pages of the Dresden Codex produced by the Maya tracking Venus’ appearances in the skies over the Yucatan. for 104 years. The Dresden Codex is one of only 4 surviving Mayan Codices.