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06/03/2021 – Ephemeris – Arcturus in the Bible.

June 3, 2021 Comments off

This is Ephemeris for Thursday, June 3rd. Today the Sun will be up for 15 hours and 23 minutes, setting at 9:23, and it will rise tomorrow at 5:58. The Moon, 1 day past last quarter, will rise at 3:30 tomorrow morning.

Arcturus is a bright orangish star that’s high in the south at 11 pm. It’s also found by following the arc of the handle of the Big Dipper, which is the ridiculous tail of Ursa Major the Great Bear. It was considered the “Guardian of the Bear”, It is in the base of the kite shaped constellation of Boötes, the herdsman or the Bear Chaser. The latter story I recounted earlier this year. The name from the Greek has been confused with the bear itself. Thus, in the King James version of the Bible Arcturus, not the Bear, meaning the Great Bear, is mentioned in the 38th chapter of Job. This has been corrected in the newer versions I’ve seen. Arcturus has a rich history in literature, mostly by being confused with the Great Bear.

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

Addendum

Arcturus, Bootes and Ursa Major

Arcturus, Boötes and Ursa Major can be seen by looking overhead while facing the west-southwest at 11 pm in early June. Created using Stellarium. Lines and figures not included.

Biblical translations

King James Version of Job 38:31-32

31 Canst thou bind the sweet influences of Pleiades, 
   or loose the bands of Orion?

32 Canst thou bring forth Mazzaroth in his season?
   or canst thou guide Arcturus with his sons?

New International Version of Job 38:31-32

31 
“Can you bind the chains of the Pleiades?
Can you loosen Orion’s belt?
32 
Can you bring forth the constellations in their seasons
or lead out the Bear with its cubs?

No one is sure what a Mazzaroth is.

04/09/2021 – Ephemeris – Follow the arc to Arcturus

April 9, 2021 Comments off

This is Bob Moler with Ephemeris for Friday, April 9th. Today the Sun will be up for 13 hours and 12 minutes, setting at 8:20, and it will rise tomorrow at 7:06. The Moon, 2 days before new, will rise at 6:57 tomorrow morning.

The fourth or fifth brightest night-time star, depending on whose list you see, is now up in the east in the evening. It is Arcturus, a bright star with an orange hue. It can be found otherwise by finding the Big Dipper and tracing out and extending the curve of the handle and “Follow the arc of the handle to Arcturus”, to remember the name of the star and how to find it. Arcturus is about 37 light years from us and is moving quite rapidly across the sky, compared to most stars, though one would not notice it to the naked eye in one’s lifetime. Arcturus is slightly more massive than our Sun, and about 7 billion years old, and is entering its red giant stage of life after using all the hydrogen fuel in its core. Our Sun, being slightly less massive will survive on hydrogen a bit longer.

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

Addendum

How to find Arcturus
How to find Arcturus. In the early spring Arcturus is low in the east in the evening. The Big Dipper is high in the northeast standing on its handle. To find and remember the name of this star simply follow the arc of the handle to Arcturus. Created using Stellarium and GIMP.

I’ll be talking more about Arcturus and the constellation it’s in Boötes the herdsman, a kite shaped constellation that’s currently laying on its side. He’s not herding, but chasing the Great Bear. But that’s another story.

03/11/2021 – Ephemeris – The Guardian of the Bear is rising

March 11, 2021 Comments off

This is Ephemeris for Thursday, March 11th. Today the Sun will be up for 11 hours and 42 minutes, setting at 6:44, and it will rise tomorrow at 7:00. The Moon, 2 days before new, will rise at 7:09 tomorrow morning.

The brightest star of spring is Arcturus which will be visible by 9 pm low in the east-northeast. Arcturus can most famously be found by following the arc of the handle of the Big Dipper, which resides fairly high in the northeastern sky to it. “Follow the arc of the handle to Arcturus.” It’s the fourth or fifth brightest star in the sky, depending on the list. It was regarded as the “Guardian of the Bear”, meaning the Great Bear, Ursa Major, of which the Big Dipper is its hind end. Apparently it’s guarding its rear. Arcturus will stay in our evening sky until the end of summer and has a fascinating story of its own aside from its ancient mythology, which I’ll talk about when it’s higher in the sky. It’s located at the base of a kite shaped constellation called Boötes, which is now horizontal and too close to the horizon to be appreciated.

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

Addendum

Arcturus rising finder animation

Arcturus rising finder animation for 9 pm tonight, March 11, 2021. Created using Stellarium and GIMP.

03/02/2021 – Ephemeris – Sirius and the Pup

March 2, 2021 Comments off

This is Ephemeris for Tuesday, March 2nd. Today the Sun will be up for 11 hours and 14 minutes, setting at 6:32, and it will rise tomorrow at 7:16. The Moon, halfway from full to last quarter, will rise at 10:51 this evening.

Sirius is the brightest night-time star and is located in the south at 9 p.m. below and a bit left of Orion the Hunter. We’ve visited Sirius a month ago. But there is another star in the Sirius system that is practically invisible due to Sirius’ dazzling glare. Its name is Sirius B, nicknamed the Pup, alluding to Sirius’ Dog Star title. The tiny star was suspected as far back as 1834 due to Sirius’ wavy path against the more distant stars in the sky. Sirius and the Pup have 50-year orbits of each other. The Pup was first seen in 1862. It was the first of a new class of stars to be discovered, white dwarfs. The Pup is a dying star with the mass of the Sun, collapsed down to the size of the Earth after running out of hydrogen fuel in its core.

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

Addendum

Sirius finder

A Sirius finder animation for late January/early February at around 8 pm. Even in bright moonlight the seven bright stars of Orion can be seen. The three stars of Orion’s belt make a great pointer to Sirius. Created using Stellarium, GIMP and Libreoffice (for the arrow).

Sirius' path

Sirius A & B’s path in the sky showing the wobble that betrayed the Pup’s presence. Credit Mike Guidry, University of Tennessee.

Two views of Sirius and the Pup

Sirius A and B imaged by two different space telescopes, revealing dramatically different views! Hubble’s image (left) shows Sirius A shining brightly in visible light, with diminutive Sirius B a tiny dot. However, in Chandra’s image (right) tiny Sirius B is dramatically brighter in X-rays! The “Universe in a Different Light” activity highlights more surprising views of some familiar objects: http://bit.ly/different-light-nsn NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester) (left); NASA/SAO/CXC (right).

 

 

02/11/2021 – Ephemeris – The Winter Triangle

February 11, 2021 Comments off

This is Ephemeris for Thursday, February 11th. Today the Sun will be up for 10 hours and 17 minutes, setting at 6:06, and it will rise tomorrow at 7:47. The Moon is new today, and won’t be visible.

I usually talk about the Winter Circle of bright stars, but some other astronomers talk about the Winter Triangle. The stars involved are Betelgeuse in the hunter Orion, Sirius in Canis Major, Orion’s large hunting dog, and Procyon in Canis Minor, his other small hunting dog. These three stars enclose a rather blank piece of sky with the faint Milky Way running through it and the almost invisible constellation of Monoceros the unicorn. The Summer Triangle has three bright stars with no other close competition. The Winter Triangle has four other bright stars near it. Any three of these would make a nice triangle. One of these constellations Canis Minor is tiny, with Procyon and one other star. It makes me think of a dachshund, or maybe, if I’m hungry, a hot dog.

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

Addendum

Winter triangle finder animation

Winter Triangle finder animation. It shows the star field, named first magnitude stars, then their constellations, then the Winter Triangle and constellations of the three stars. Click on the image to enlarge. Created using Stellarium and GIMP.

01/29/2021 – Ephemeris – Let’s get Sirius

January 29, 2021 Comments off

This is Ephemeris for Friday, January 29th. Today the Sun will be up for 9 hours and 42 minutes, setting at 5:47, and it will rise tomorrow at 8:03. The Moon, 1 day past full, will rise at 6:49 this evening.

In the early evening the great constellation of Orion the hunter can be seen in the southeast. Its large rectangle of bright stars is easily visible, even with a full moon. The three stars in a straight line, his belt, tilt downward to the left to a very bright star merrily twinkling lower in the sky. This star is called Sirius, also known as the Dog Star because it’s in the heart of Orion’s larger hunting dog, Canis Major. It is an arc light white star as seen in binoculars or telescope. It is the brightest star in the night sky, and a neighboring star, just twice the distance of the closest star to the Sun at 8.6 light years. It’s name, Sirius, has nothing to do with a dog, but is from the Greek meaning scorching for its brightness or sparkling, due to its intense twinkling.

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

Addendum

Sirius finder

A Sirius finder animation for late January/early February at around 8 pm. Even in bright moonlight the seven bright stars of Orion can be seen. The three stars of Orion’s belt make a great pointer to Sirius. Created using Stellarium, GIMP and Libreoffice (for the arrow).

I’ll come back to Sirius several times this winter. Or search for Sirius for other times I’ve talked about this brightest of the night-time stars.

01/26/2021 – Ephemeris – A look at the bright red giant star Betelgeuse

January 26, 2021 Comments off

This is Ephemeris for Tuesday, January 26th. Today the Sun will be up for 9 hours and 35 minutes, setting at 5:43, and it will rise tomorrow at 8:06. The Moon, 2 days before full, will set at 7:38 tomorrow morning.

At 8 pm the constellation of Orion the hunter is in the southeastern sky. The bright reddish star at the top left of Orion’s distinctive seven-star pattern is Betelgeuse a star near the end of its life. Being a single bright star, its distance is not well determined and is estimated to be about 550 light years away with an uncertainty of up to 20 percent, which make other estimates that uncertain too, like its mass and diameter. It’s somewhat less than 20 times the mass of the Sun, and a diameter possibly as large as Jupiter’s orbit of the Sun. It is old for a star of its mass, probably 8 million years old, with up to a million years to go on the outside before it will probably explode as a supernova and grace our skies as bright as the Moon for the better part of the better part of a year.

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

Addendum

Orion

The seven brightest stars of Orion in the south-southeast at 8 p. in late January.

Betelgeuse drawing

“This artist’s impression shows the supergiant star Betelgeuse as it was revealed thanks to different state-of-the-art techniques on ESO’s Very Large Telescope, which allowed two independent teams of astronomers to obtain the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. The scale in units of the radius of Betelgeuse as well as a comparison with the Solar System is also provided.” Credit: ESO/L. Calçada (ESO is the European Southern Observatory)

12/17/2020 – Ephemeris – Betelgeuse, Betelgeuse… Nope not saying it again

December 17, 2020 Comments off

This is Bob Moler with Ephemeris for Thursday, December 17th. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:03, and it will rise tomorrow at 8:15. The Moon, 3 days past new, will set at 8:18 this evening.

The constellation Orion the hunter will have completely risen by 8 pm this evening. The leftmost bright red star in his shoulder is Betelgeuse. It’s phonetically spelled name (Beetle Juice) made the title of a movie in 1988. A year ago it’s dramatic dimming for a while caused some to wonder that it was about to explode in a supernova. Betelgeuse does normally vary a bit in brightness, but that was the most ever recorded. It’s a red giant star with a mass of 16 to 19 times the Sun’s. Its distance is thought to be about 550 light years away. It is difficult to measure the distance of single bright stars, even with satellites. Its age is maybe 8 to 8 ½ million years old out of a life expectancy of 10 million years, compared to the Sun’s 10 billion year life expectancy.

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

Addendum

Orion

Orion at 8 pm or about 3 hours after sunset in mid December. Its seven brightest stars make an unmistakable pattern with only Betelgeuse and Rigel labeled. Created using Stellarium.

Betelgeuse before and after dimming

This comparison image shows the star Betelgeuse before and after its unprecedented dimming. The observations, taken with the SPHERE instrument on ESO’s Very Large Telescope in January and December 2019, show how much the star has faded and how its apparent shape has changed. Credit: ESO/M. Montargès et al.

Betelgeuse's dust plume

An image of the star Betelgeuse taken in infrared shows it’s surrounded by a vast cloud of dust that erupted from the surface (the bright star itself is masked out, though an image of it has been superposed there for scale — the star is about the size of the orbit of Jupiter, over a billion km wide). Credit: ESO/P. Kervella/M. Montargès et al., Acknowledgement: Eric Pantin via Phil Plait’s Bad Astronomy blog on syfy.com.

Categories: Ephemeris Program, Stars Tags: ,

09/18/2020 – Ephemeris – A closer look at Cepheus the king’s most famous star

September 18, 2020 Comments off

This is Ephemeris for Friday, September 18th. Today the Sun will be up for 12 hours and 20 minutes, setting at 7:46, and it will rise tomorrow at 7:27. The Moon, 1 day past new, will set at 8:52 this evening.

There’s a faint constellation in the northeast above the W shaped constellation of Cassiopeia. It’s a nearly upside down church steeple of a constellation called Cepheus the king, and husband of queen Cassiopeia. Cepheus’ claim to astronomical fame is that one of its stars, Delta (δ) Cephei, is the archetype for the important Cepheid variable stars. Delta is the bottom most of a trio of stars at the right corner of the constellation. In the early 20th century Henrietta Leavitt discovered that Cepheids in the nearby galaxy the Large Magellanic Cloud varied in brightness with a period that was related to their average brightness. This meant that Cepheids could be used as standard candles to measure the great distances to other galaxies.

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

Addendum

Cassiopeia and Cepheus finder animation

Cassiopeia and Cepheus finder animation looking in the northeast at 9 pm or about an hour after sunset in mid-September. Created using Stellarium and GIMP.

Delta Cephei (circled) finder for mid-September at 9 pm or about an hour after sunset looking northeast. The brighter stars are marked by their Bayer Greek letters. Numerical designations are Flamsteed numbers. Created using Cartes du Ciel (Sky Chart).

Delta_Cephei_lightcurve

Light Curve of Delta Cephei. The pulsation period is 5.367 days. Credit: ThomasK Vbg – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13887639

07/06/2020 – Ephemeris – The southernmost star of the Summer Triangle, Altair

July 6, 2020 Comments off

This is Bob Moler with Ephemeris for Monday, July 6th. Today the Sun will be up for 15 hours and 25 minutes, setting at 9:30, and it will rise tomorrow at 6:05. The Moon, 1 day past full, will rise at 11:02 this evening.

The southernmost star of the Summer Triangle is Altair, high in the east-southeast. The other two stars of the triangle are Vega nearly overhead in the east, and Deneb high in the east-northeast. Altair is the closest of the three at a distance of 16.7 light years away. One light year is nearly 6 trillion miles. Altair is 10 times the brightness of the Sun. If seen at Altair’s distance, the Sun would only be as bright as one of the two stars that flank it. What is rather different about Altair is its rapid rotation. While it’s almost twice the sun’s diameter, it rotates once in about 9 hours, The CHARA Interferometer at Mt. Wilson has actually imaged its squashed disk in the infrared. Our Sun’s a slow poke, taking nearly a month to rotate once.

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

Addendum

Summer Triangle. Created using Stellarium.

Summer Triangle. Created using Stellarium.

Altair

Lines added to show the rotation axis. Credit: Zina Deretsky, National Science Foundation.