01/12/2021 – Ephemeris – The celestial river Eridanus

This is Bob Moler with Ephemeris for Tuesday, January 12th. Today the Sun will be up for 9 hours and 7 minutes, setting at 5:25, and it will rise tomorrow at 8:17. The Moon, 1 day before new, will rise at 8:58 tomorrow morning.

One of the more obscure constellations around is Eridanus, which depicts a river. The river starts near the lower right corner of Orion, near the bright star Rigel and flows to the right then down near the southwestern horizon, then it meanders along the horizon to the south before turning below the horizon. One has to travel to the far south to see the southern terminus of the river, the bright star Achernar. Writers over the ages have seen here the Nile and the Earth circling river Ocean of the flat earth days. Achernar is actually two stars, the brightest was discovered to be the flattest star known, due to its rapid spin. The dimensions of Achernar A has been determined to be twice as wide across its equator than from pole to pole. It’s 139 light years away.

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

Addendum

An animation of the constellation Eridanus which is a river that flows from Rigel in Orion to the star Achernar below our southern horizon at latitude 45 degrees north. Create using Stellarium and GIMP.

12/07/2020 – Ephemeris – Looking forward to the best of winter: Orion

This is Ephemeris for Monday, December 7th. Today the Sun will be up for 8 hours and 55 minutes, setting at 5:02, and it will rise tomorrow at 8:07. The Moon, at last quarter today, will rise at 12:25 tomorrow morning.

Orion, the central constellation of the winter evening sky will be completely risen by 9 this evening. Then it can be seen low in the east-southeast it’s upright rectangle of stars tilted to the left. The topmost star to the left in this rectangle is the famous red giant star Betelgeuse, which is reportedly dimming again. It’s in Orion’s shoulder. In his other shoulder is Bellatrix, a name known to Harry Potter fans. In his knees are Rigel, a blue-white giant star and Saiph. In the center of the rectangle are three stars in a straight line, now almost vertically arranged, Orion’s belt. And below his belt what seem to be three more stars, his sword. In the center of the sword stars can be found, with binoculars or telescope, Orion’s most famous feature, the Great Orion Nebula.

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

Addendum

Orion early December finder animation for 9 pm December 7th. Created using Stellarium and GIMP.

Orion’s named stars including the belt stars. Cursa, though named belongs to the neighboring constellation Eridanus the river. Created using Stellarium.

01/11/2019 – Ephemeris – The bright star in Orion’s knee: Rigel

Ephemeris for Friday, January 11th. The Sun will rise at 8:18. It’ll be up for 9 hours and 4 minutes, setting at 5:23. The Moon, 3 days before first quarter, will set at 10:55 this evening.

Yesterday I talked about the star Betelgeuse the bright red star in the top left of Orion’s upright rectangle. Orion is seen in the southeast at 9 in the evening. The blue-white star in Orion’s opposite corner is usually brighter. It is Rigel whose longer Arabic name of which Rigel is the first part means “Left Leg of the Giant”. Rigel is a giant itself, actually a super giant star, which is more a measure of its mass than its size, that of 23 solar masses. Its surface temperature is more than twice as hot as the sun. It is 120 thousand times as bright as the sun and 100 times its diameter. Its distance is around 860 light years. Those with telescopes might be able to spot a close companion star to Rigel, just at the edge of the bright arc light image of Rigel itself.

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

Addendum

Orion’s brightest stars with their names for 9 p.m. January 7, 2019. Click on the image to make Orion a giant hunter. Created using Stellarium..

Rigel with its companion star as photographed through a telescope. No attribution. Source: http://washedoutastronomy.com/content/urban-orion?page=1

01/08/2019 – Ephemeris – The river at Orion’s feet

Ephemeris for Tuesday, January 8th. The Sun will rise at 8:19. It’ll be up for 9 hours exactly, setting at 5:19. The Moon, 3 days past new, will set at 7:55 this evening.

One of the more obscure constellations around is Eridanus, which depicts a river. The river starts near the lower right corner of Orion, near the bright star Rigel and flows to the right then down near the southwestern horizon, then it meanders along the horizon to the south before turning below the horizon. One has to travel to the far south to see the southern terminus of the river, the bright star Achernar. Writers over the ages have seen here the Nile and the earth circling river Ocean of the flat earth days. Achernar is actually two stars, the brightest was discovered to be the flattest star, due to its rapid spin. The dimensions of Achernar A has been determined to be twice as wide across its equator than from pole to pole. It’s 139 light years away.

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

Addendum

An animation of the constellation Eridanus which is a river that flows from Rigel in Orion to the star Achernar below our southern horizon at latitude 45 degrees north. Create using Stellarium and GIMP.

01/07/2019 – Ephemeris – The stars of Orion

Ephemeris for Monday, January 7th. The Sun will rise at 8:19. It’ll be up for 8 hours and 59 minutes, setting at 5:18. The Moon, 2 days past new, will set at 6:57 this evening.

The seven bright stars of Orion now shine in the southeastern sky in the evening. Two shoulder stars, Betelgeuse, and Bellatrix, Two knee stars Saiph, and Rigel, In between are the three belt stars in a row, Alnitak, Alnilam, and Mintaka. Betelgeuse and Rigel are first magnitude stars, among the brightest in the sky, while the others are second magnitude. As far as brightness goes it puts the Big Dipper to shame with its six second magnitude and one third magnitude stars. Of course we in northern Michigan have the Big Dipper always, because it never sets. Orion, only about six months. Due to its position straddling the equator of the sky, Orion is seen by all the people of the world. Parts of him are even seen at the north and south poles.

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

Addendum

Orion’s brightest stars with their names for 9 p.m. January 7, 2019. Click on the image to make Orion a giant hunter. Created using Stellarium..

 

02/22/2018 – Ephemeris – The blue-white star at Orion’s knee

Ephemeris for Thursday, February 22nd. The Sun will rise at 7:32. It’ll be up for 10 hours and 49 minutes, setting at 6:21. The Moon, 1 day before first quarter, will set at 1:46 tomorrow morning.

The bright star at the bottom right corner of the big upright rectangle that is the giant hunter Orion’s body in the south-southeast is Rigel. It is a white star with a bluish tinge. It compares in brightness with Betelgeuse at the opposite end of Orion’s rectangle, though it’s usually a bit brighter. The mismatch in color makes brightness comparisons difficult. Rigel is about 860 light years away, It’s 23 times the mass of the Sun, 120 thousand the times brighter than the Sun, and a diameter almost the size of the orbit of Mercury. It’s age is thought to be about 8 million years. It has a visual companion star that can be seen in amateur telescopes. It’s not that dim, but suffers by being close to the arc light brightness of Rigel.

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

Addendum

Orion’s named stars including the belt stars. Created using Stellarium.

Rigel with its companion star as photographed through a telescope. No attribution. Source: http://washedoutastronomy.com/content/urban-orion?page=1

02/12/2018 – Ephemeris – The Winter Circle

Ephemeris for Monday, February 12th. The Sun will rise at 7:47. It’ll be up for 10 hours and 19 minutes, setting at 6:07. The Moon, 3 days before new, will rise at 6:29 tomorrow morning.

The winter skies are blessed with more first magnitude stars than any other season. Six of these stars lie in a large circle centered on the seventh, It’s called the Winter Circle. This circle is up at 9 p.m. Starting high overhead is yellow Capella in Auriga the charioteer. Moving down clockwise is orange Aldebaran in the face of Taurus the Bull. Then down to Orion’s knee we find blue-white Rigel. Down and left is the brightest star of all the brilliant white Sirius the Dog Star in Canis Major, lowest of these stars in the south-southeast. Moving up and left is white Procyon in Canis Minor, Above Procyon is Pollux in Gemini the twins. All these are centered, well not quite, on Betelgeuse the bright red star in Orion’s shoulder.

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

Addendum

The bright stars of winter arrayed in a circle (well almost). Created using Stellarium.

02/08/2018 – Ephemeris – The wonderfully named stars of Orion

Ephemeris for Thursday, February 8th. The Sun will rise at 7:53. It’ll be up for 10 hours and 8 minutes, setting at 6:01. The Moon, 1 day past last quarter, will rise at 3:09 tomorrow morning.

The constellation of Orion the hunter is visible in the south at 9 p.m. The stars of Orion are interesting in themselves. Starting at the top left of the seven bright stars of Orion’s torso is Betelgeuse the bright red star, whose name means something like “Armpit of the Giant”. The star in Orion’s other shoulder is Bellatrix the “Amazon Star”. Below are the three stars of Orion’s belt, from left to right; Alnitak, Alnilam and Mintaka. Their names mean “Girdle”, “Belt of Pearls”, and “Belt” respectively. Down to Orion’s knees we look on the left to the star Saiph pronounced ‘safe’ which means “Sword”, though it is some ways from the stars of Orion’s sword. Finally there’s the bright blue-white star Rigel whose name means “Left Leg of the Giant”.

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

Addendum

The named stars of Orion. Created using Stellarium.

Betelgeuse, pronounced Beetlejuice is the name of a 1988 movie, where Betelgeuse (spelled properly) is a particularly mischievous demon.  Don’t say his name three times, or he’ll come and ‘help’ you.  Oops, I did.  It is a red giant star near the end of its life.

Bellatrix, is now known to most of us now as the first name as the first name of Bellatrix Lestrange from J. K. Rowling’s Harry Potter book and movie series.  Other members of the Black family have astronomical names, such as Regulus (Leo) Black, and Sirius (Canis Major) Black.

The names of the belt stars were taught to me by Evelyn Grebel of the Grand Rapids Public Museum in the late 1950s.  She was one of the founders of the Grand Rapids Amateur Astronomical Association.  The names Alnitak, Alnilam and Mintaka have stuck with me ever since.  It was through her that I was able to worm my way into working at the museum’s new then unnamed planetarium.  I also remember being in her office with her, listening to the radio as Alan Shepard made his historic suborbital flight on May 5th, 1961.

Rigel is a hot blue-white star, and will probably become a red giant star like Betelgeuse.  There is another bright star named Rigel, but most don’t know it.  It’s Rigel Kentaurus, the leg of the centaur of Centaurus.  It’s better known as Alpha Centauri, a catalog designation, and the nearest star to the solar system.

12/11/2017 – Ephemeris – Orion rising

Ephemeris for Monday, December 11th. The Sun will rise at 8:09. It’ll be up for 8 hours and 52 minutes, setting at 5:02. The Moon, 1 day past last quarter, will rise at 2:22 tomorrow morning.

Off in the east-southeast at 9 in the evening the great constellation of Orion will be seen. This is the most famous of all constellations world-wide. We think the Big Dipper is a big deal. It’s not even a constellation, being the hind end of the great bear Ursa Major. Also it’s invisible if one travels far enough south of the equator. Orion is now a rectangle of stars tilted to the left as he rises. With three stars in a straight line in the center, his belt. They are aligned nearly vertically. Orion is a giant hunter. The rectangle depicts his shoulders and knees. Among its other bright stars Orion contains two of the brightest. The upper left star is the famous red giant star Betelgeuse. The lower left star is the blue-white super giant Rigel.

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

Addenda

Orion fully risen in the east-southeast a 9 p,m, approximately 4 hours after sunset, December 11. Created using Stellarium and GIMP.

Note to Blog readers

As you probably know these posts are transcripts of my Ephemeris program.  The length of the program is exactly 59 seconds, and the first paragraph takes approximately 14 of those seconds.  So I don’t have much time for the topic at hand.  Therefore I dole out information in rather small spoonfuls.  I’ll be revisiting Orion many times over the winter, talking about the other stars, and wonders found among its stars, also its mythology.   If you can’t wait, type Orion in the search bar for all the past programs on Orion.  Don’t be surprised that much of the programs don’t change much from year to year.  I post the week’s worth of Ephemeris program MP3s on my monthly website http://ephemeris.bjmoler.org/ under the Audio link.

Sunday night and into the wee hours of Monday morning is the time I usually write and record the programs for Tuesday through the next Monday.  Blog postings are prepared the night before the air date.

 

11/20/2017 – Ephemeris – The Moon is near Saturn tonight and the approaching signs of winter

Ephemeris for Monday, November 20th. The Sun will rise at 7:46. It’ll be up for 9 hours and 23 minutes, setting at 5:09. The Moon, 2 days past new, will set at 7:04 this evening.

Tonight the two day old Moon will appear near Saturn. The ringed planet will appear to the left and a bit below the thin crescent Moon before they set about an hour later. The approaching winter season and the resumption of standard time have dropped sunset to 5:09 in the Interlochen/Traverse City area. Our sunset will drop another 11 minutes before slowly recovering 19 days from now. Two to three hours later another sign of the approaching winter season will appear, as the constellation of the giant hunter Orion rises in the east. He is resplendent with his nearly vertical belt of three stars rising, framed to the left and right by the bright stars reddish Betelgeuse and bluish Rigel. He will dominate our evening skies until April.

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

Addendum

The Moon and Saturn at 6 p.m. November 20, 2017. Created using Stellarium.

Finder chart for the rising Orion at 9 p.m., November 30, 2017. Created using Stellarium and GIMP.