04/23/2018 – Ephemeris – The Ursa Major Association

April 23, 2018 Leave a comment

Ephemeris for Monday, April 23rd. The Sun rises at 6:45. It’ll be up for 13 hours and 52 minutes, setting at 8:37. The Moon, 1 day past first quarter, will set at 4:15 tomorrow morning.

The usual impression is to think that the stars of a constellation are actually located close together. This is usually not true. The stars of a constellation can be at vastly different distances. The Big Dipper is different. The five stars, excepting the two end stars of the dipper and 12 other dimmer stars in the general area are of similar distance and have the same motion through space. The group is called the Ursa Major Moving Cluster or Ursa Major Association, and is moving about 9 miles per second relative to the solar system to the east and south. An association is a rather loose, sparse star cluster. This association lies about 75 light years away. If it were five times farther away, it would be the same distance as the Pleiades.

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

Addendum

The Big Dipper

Craig Brown’s drawing of where the stars of the Big Dipper are and are heading. Click on the image to go to Craig’s WordPress post.

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04/20/2018 – Ephemeris – Astronomy Day and the Lyrid meteor shower this weekend

April 20, 2018 Leave a comment

Ephemeris for Friday, April 20th. The Sun rises at 6:50. It’ll be up for 13 hours and 44 minutes, setting at 8:34. The Moon, 2 days before first quarter, will set at 1:50 tomorrow morning.

Tomorrow is Astronomy Day. The Grand Traverse Astronomical Society will celebrate with a star party at Northwestern Michigan College’s Rogers Observatory. Tomorrow April 21st, from 9 p.m. to 11 p.m. There will also be activities inside the observatory, so clear or cloudy there will be something to see or do for all ages. The Lyrid Meteor Shower will be active this weekend and reach a peak Sunday. The meteors from this shower will seem to come from near the constellation of Lyra the harp, a small and narrow parallelogram of stars with the bright star Vega near it. The best viewing will be for a few hours in the wee morning hours after the Moon sets Sunday or Monday mornings.

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

Addendum

Lyrid meteor shower radiant

All sky view at 4 a.m. Sunday or Monday morning with the Lyrid radiant. Created using Stellarium.

The additional radiants showing in the image above are the (sigma) σ-Scorpids which will reach peak on April 28th, a minor shower and (eta) η-Auqariids which will reach peak on May 6th.  Both these meteor showers have severe interference by the Moon.

04/19/2018 – Ephemeris – The Big Dipper’s stars Mizar and Alcor

April 19, 2018 Leave a comment

Ephemeris for Thursday, April 19th. The Sun rises at 6:51. It’ll be up for 13 hours and 41 minutes, setting at 8:32. The Moon, 3 days before first quarter, will set at 12:47 tomorrow morning.

The most interesting star in the Big Dipper is Mizar and its dim companion Alcor. It is the second star from the end of the handle, where the bend in the handle takes place. Folks with good vision can see the dimmer star right next to Mizar. In ancient times it was used as an eye test for visual acuity for warriors as such it was known as the “Horse and the Rider”.

Mizar is second magnitude, in the second rank of star brightness invented by the Greek astronomer Hipparchus in the 2nd century BC. He ranked stars in 6 classes, from first magnitude for the brightest to 6th for the dimmest visible to the naked eye. Alcor comes in at 4th magnitude. It does suffer a bit by being close to Mizar which is 6 times brighter.

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

Addendum

The Big Dipper with Mizar & Alcor

The Big Dipper, almost overhead at 10 p.m. April 19 with Mizar and Alcor pointed out. Created using Stellarium.

Telescopic Mizar and Alcor

A view of Mizar and Alcor as seen in a telescope. Mizar is itself a binary star. In actuality both components of Mizar and Alcor are spectroscopic binaries, which are too close to split, but their presence is detected by their Doppler motions with spectrographs. Created using Stellarium.

04/18/2018 – Ephemeris – It’s Wednesday, do you know where the bright planets are?

April 18, 2018 Comments off

Ephemeris for Wednesday, April 18th. The Sun rises at 6:53. It’ll be up for 13 hours and 38 minutes, setting at 8:31. The Moon, 3 days past new, will set at 11:38 this evening.

It’s Wednesday again and time to look for the bright planets. One bright planet is in the evening sky, the brightest, Venus. It will be visible low in the Western twilight from about 8:40 p.m. until it sets at 10:34. Venus is blindingly bright in binoculars or a small telescope.

Jupiter will rise late this evening at 10:23 p.m. That doesn’t make it an evening planet. It has to rise before sunset to be an evening planet. Saturn will rise at 2:17 a.m., while Mars will rise at 2:52 a.m. At 6 tomorrow morning these three planets will be strung across the southern sky. Bright Jupiter will be in the southwest, dimmer Mars and Saturn will be in the south-southeast, with Mars to the left of Saturn in the morning twilight.

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

Addendum

Venus and the Moon in evening twilight

Venus and the Moon in evening twilight at 9 p.m, tonight April 18, 2018. The Moon is shown at 3 times its actual size for clarity. Click on the image to enlarge. Created using Stellarium.

Binocular Moon

The Moon as it might be seen in binoculars at 9 p.m. April 18, 2018. Earth shine should be visible. Created using Stellarium.

Morning planets

The morning planets at 6 a.m. April 19, 2018. Click on the image to enlarge. Created using Stellarium.

The morning planets as seen in a telescope using the same magnification. A magnified image of Mars is inset showing some of the features that may be visible under higher magnification. The large dark area below right of center on Mars is Syrtis Major “The Great Swamp”. It sounds so much better in the original Latin. Of course there probably hasn’t been a swamp on Mars in 3 billion years, give or take. Today the disc of Mars attained a diameter of 9.9 seconds of arc. Created using Cartes du Ciel (Sky Charts).

Planets and the Moon at sunset and sunrise of a single night

Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on April 18, 2018. The night ends on the left with sunrise on the 19th. Click on the image to enlarge. Created using my LookingUp program.

04/17/2018 – Ephemeris – The Moon will appear near the planet Venus tonight

April 17, 2018 Comments off

Ephemeris for Tuesday, April 17th. The Sun rises at 6:55. It’ll be up for 13 hours and 35 minutes, setting at 8:30. The Moon, 2 days past new, will set at 10:27 this evening.

This evening, while viewing Venus the Moon will be to the left and below our evening star. It will be a thin sliver of a crescent and in the twilight there will be the suggestion that there is more than the thin sliver of the Moon visible. Binoculars will confirm that the entire disk of the Moon will be visible. The effect is called earthshine. The nearly full Earth is illuminating the Moon to a much greater degree than the full Moon illuminates the Earth. The ancients had a more beautiful way to put it: “The old Moon in the new Moon’s arms.” There is the same effect in the morning of the few days prior to the new Moon. The instant of new Moon occurred at 9:57 p.m. Eastern Daylight Time Sunday night the 15th. That’s the 16th according to Universal time. What does your calendar say?*

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

Addendum

Venus and the Moon

Venus and the Moon at 9 p.m. April 17, 2018. The Moon’s image has been enlarged two and a half times to show the earth shine and hint at the sliver of a crescent. Created using Stellarium.

* About the new moon this month.  I have two wall calendars.  One by NASA showing that the new moon occurred on April 16th based on Universal Time.  Universal Time (UT) used to be known as Greenwich Mean Time (GMT).  My other wall calendar is from the Old Farmers Almanac.  It shows the new moon to be on the 15th.  The almanac’s calendar pages are based on the location of Boston and the Eastern Time zone, standard or daylight saving.  The calendar seems to be similarly based.

The Moon phase calculations for these programs are created by a DOS version of my LookingUp program, which is by now over 20 years old.  I calculate them up a year at a time for the next year.  These are based, of course on the Eastern Time zone.

04/16/2018 – Ephemeris – The Virgo cluster of galaxies

April 16, 2018 Comments off

Ephemeris for Monday, April 16th. The Sun rises at 6:56. It’ll be up for 13 hours and 32 minutes, setting at 8:29. The Moon, 1 day past new, will set at 9:16 this evening.

The stars around the constellation Leo and Virgo below and left of it feature relatively few stars, compared to those around Orion and the other winter constellations. That isn’t just a lot of blank sky, but beyond what can be seen with the naked eye in the region of southwestern Virgo, just to the lower left of the tail star Denebola of Leo is a vast cluster of galaxies that outnumber the stars of the same brightness in that direction. It is the Virgo Galaxy Cluster. Astronomers shorten the name to the Virgo Cluster. Two centuries ago the comet hunter Charles Messier swept this region with his small telescope and found many fuzzy bodies that could be confused with comets. He didn’t know what they were, but they sure weren’t comets, because they didn’t move against the stars.

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

Addendum

Brighter members of the Virgo Cluster. Created using Stellarium.

Brighter members of the Virgo Cluster. Created using Stellarium. Open circles are galaxies, circles with crosses are globular star clusters, outlying members of our Milky Way galaxy. This image is from a few years ago – Saturn, above Spica, has moved on.

04/13/2018 – Ephemeris – Regulus, in Leo the lion, the “Little King” star.

April 13, 2018 Comments off

Ephemeris for Friday, April 13th. The Sun will rise at 7:01. It’ll be up for 13 hours and 23 minutes, setting at 8:25. The Moon, 2 days before new, will rise at 6:42 tomorrow morning.

The brightest star in the constellation Leo, which is high in the south these evenings is Regulus, whose name means “Little King”. It is appropriate due to its position in the heart of the king of beasts Leo the lion. Regulus is dead last in brightness of the 21 first magnitude stars, the brightest night-time stars. Even so, it is much brighter than the Sun. It is 79 light years away. The Sun would require a telescope to be spotted at that distance. Regulus appears to be a quadruple star system. The bright star itself is really two stars with a bright star orbited by a much dimmer star every 40 days. There are two dimmer stars much further out that share Regulus’ motion through space. There are an infinite variety of star system arrangements in the galaxy and beyond.

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

Addendum

Regulus in Leo the Lion

The naked eye stars of Leo, including Regulus at 10 p.m. April 13, 2018. Note that Algieba is a binary star that can be seen in small telescopes. The yellow line that passes Regulus is the ecliptic the apparent path of the Sun. The Moon and planets also hang out near that line. Created using Cartes du Ciel (Sky Charts).

Note:  The original scheduled topic for today was the announcement of a star party at the Sleeping Bear Dunes National Lakeshore tomorrow, April 14th.  It seems the weather gods have a different plan.  There’s a winter storm watch from late Friday night (tonight) to noon Sunday with 3-6 inches of slushy snow.