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10/05/2022 – Ephemeris – Let’s search for the naked-eye planets for this week

October 5, 2022 Leave a comment

This is Ephemeris for Wednesday, October 5th. Today the Sun will be up for 11 hours and 30 minutes, setting at 7:15, and it will rise tomorrow at 7:46. The Moon, 3 days past first quarter, will set at 3:33 tomorrow morning.

Let’s search for the naked-eye planets for this week. The waxing gibbous Moon will be visible near Saturn tonight, with the ringed planet right and above our Moon. Super bright Jupiter is to the far right of the Moon at 9 pm in the east southeast, the brightest star-like object in the sky. Jupiter is seen against the stars of Pisces the fish, while Saturn is spotted in the eastern end of Capricornus the sea goat. I don’t think the stars will be visible with the bright Moon. One star in their direction may be visible and low on the horizon and in line tonight with Saturn and the Moon. It’s Fomalhaut, normally the loneliest star in the sky. Before seven tomorrow morning, the red planet Mars will be high in the south, above the winter constellation of Orion. At that hour, Mercury can also be spotted low in the east.cc

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Evening planets and the Moon tonight

Evening planets and the Moon tonight, October 5, 2022, at 9 pm. Click on the image to enlarge it. Created using Stellarium.

Annotated Gibbous Moon Animation for tonight

Annotated Gibbous Moon Animation for tonight, October 5, 2022, as it might in binoculars or a small telescope. Created using Stellarium, LibreOffice Draw and GIMP.

Translations of some lunar feature names according to Virtual Moon Atlas

Mare Crisium – Sea of Crises
Mare Fecunditatis – Sea of Fertility
Mare Frigoris – Sea of Cold
Mare Imbrium – Sea of Showers
Mare Nectaris – Sea of Nectar
Mare Nubium – Sea of Clouds
Mare Serenitatis – Sea of Serenity
Mare Tranquillitatis – Sea of Tranquility
Mare Vaporum – Sea of Vapors
Montes Apenninus – Apennines Mountains
Sinus Asperitatis – Golfe des Asperites
Sinus Iridium – Bay of Rainbows
Sinus Medii – Bay of the Center

Craters are generally named after astronomers, people of science, or explorers

Note that Mare is pronounced Mar-é

Morning planets Mars and Mercury at 7 am tomorrow

Morning planets, Mars and Mercury with the winter stars and Orion at 7 am tomorrow morning, October 6, 2022. Click on the image to enlarge it. Created using Stellarium.

Telescopic views of Saturn Jupiter and Mars

Telescopic views of Saturn Jupiter and Mars (north up) as they would be seen in a small telescope, with the same magnification. The image doesn’t show it, but the white north polar cap will appear at the top or north limb of Mars. Saturn and Jupiter are shown at 9 pm, Mars at 6 am. I do not show planets less than 10 seconds of arc in diameter. Apparent diameters: Saturn 18.00″, its rings 41.91″; Jupiter 49.69″. Mars 12.44″. Mars’ distance is 69.7 million miles (112.2 million kilometers). Mercury, which isn’t shown, is 7.51″ in diameter and 40.8% illuminated. The ” symbol means seconds of arc (1/3600th of a degree.) Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).

Planets and the Moon on a single night

The naked-eye planets and the Moon at sunset and sunrise on a single night, starting with sunset on the right on October 5, 2022. The night ends on the left with sunrise on the 6th. Click on the image to enlarge it. Created using my LookingUp program and GIMP.

10/03/2022 – Ephemeris – There’s something on the Moon that’s straight and not circular

October 3, 2022 Leave a comment

This is Ephemeris for Monday, October 3rd. Today the Sun will be up for 11 hours and 36 minutes, setting at 7:19, and it will rise tomorrow at 7:44. The Moon, 1 day past first quarter, will set at 12:55 tomorrow morning.

On this program, I try to talk about celestial objects one can see or find with the naked eye. Once found, I do talk about what they would look like in binoculars or small telescope. For those wanting more information, consult my blog bobmoler.wordpress.com where my scripts are posted with more information, illustrations and charts. The thing I’m talking about today is a feature on the Moon that’s visible only two nights a month. The day after first quarter, and the day after last quarter. It’s the straightest thing on the Moon, called the Straight Wall, that’s 67 miles (110 km) long and 900 feet (300 m) high. It is close to the terminator, the Moon’s sunrise line, about halfway from the center of the Moon to the south edge. It’s the thinnest dark line you can imagine.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

The Straight Wall or, officially in Latin, Rupes Recta, is a rectilinear fault. It isn’t really a wall, but a 7 degree slope. Once the Sun rises past seven degrees in that location of the Moon, it disappears. Near local sunset, a day after last quarter, the low sun in its sky shines more on it than the flat ground, so it shows up bright. Click on the image to enlarge it. The information and images were created from Virtual Moon Atlas, which is free software for MS Windows. I have a link to it on this page.

09/29/2022 – Ephemeris – Previewing October skies

September 29, 2022 Comments off

This is Ephemeris for Thursday, September 29th. Today the Sun will be up for 11 hours and 48 minutes, setting at 7:26, and it will rise tomorrow at 7:39. The Moon, 3 days before first quarter, will set at 9:20 this evening.

Let’s take an early look at the skies for the month of October. Tomorrow I’ll talk about local observing events for Saturday, both afternoon and evening. Back to October. The Sun will still be moving south rapidly. Daylight hours in the Interlochen/Traverse City area and will drop from 11 hours and 42 minutes on Saturday the 1st to 10 hours, 13 minutes at month’s end. The altitude of the Sun above the southern horizon at local noon will be 42 degrees Saturday in the Interlochen area, and will descend to 31 degrees on Halloween. For the Straits of Mackinac area, the Sun will be a degree lower, and the daytime hours will be a bit shorter. The Orionid meteor shower, bits of Halley’s Comet, won’t be bothered by the bright Moon until the early morning on the 21st.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

October Evening Star Chart

October

Star Chart for October 2022 (9 p.m. EDT, October 15, 2022). Click on image to enlarge it. Created using my LookingUp app.

The planets and stars are plotted for the 15th at 9 p.m. EDT in the evening and 6 a.m. for the morning chart. These are the chart times. Note that Traverse City is located approximately 45 minutes behind our time meridian, West 75° longitude. (An hour 45 minutes behind our daylight saving time meridian during EDT). To duplicate the star positions on a planisphere you may have to set it to 1 hour 45 minutes earlier than the current time.

October Morning Star Chart

October morning star chart

Star Chart for October mornings, 2022 (6 a.m. EDT, October 15, 2022). Click on image to enlarge. Created using my LookingUp app.

For a list of constellation names to go with the abbreviations, click here.

  • Pointer stars at the front of the bowl of the Big Dipper point to Polaris, the North Star.
  • Leaky dipper drips on Leo.
  • Follow the arc of the handle of the Big Dipper to the star Arcturus.
  • The Summer Triangle is in red.
  • DracR – Draconid Radiant – Peaks the 8th – Zenithal Hourly Rate < 10 with rare outbursts of a thousand an hour. It’s hindered this year by the full moon.
  • OriR – Orionid Radiant – Peak 21st – Zenithal Hourly Rate = 20

Twilight Limits, Nautical and Astronomical

EDT
Morning Twilight Evening Twilight Dark Night Moon
Date Astro. Nautical Nautical Astro. Start End Illum.
2022-10-01 6h09m 6h43m 20h29m 21h04m 22h45m 6h09m 0.41
2022-10-02 6h10m 6h44m 20h28m 21h02m 23h45m 6h10m 0.53
2022-10-03 6h11m 6h46m 20h26m 21h00m 6h11m 0.64
2022-10-04 6h13m 6h47m 20h24m 20h58m 0h56m 6h13m 0.75
2022-10-05 6h14m 6h48m 20h22m 20h56m 2h14m 6h14m 0.84
2022-10-06 6h15m 6h49m 20h20m 20h54m 3h34m 6h15m 0.91
2022-10-07 6h16m 6h50m 20h18m 20h52m 4h52m 6h16m 0.97
2022-10-08 6h18m 6h52m 20h17m 20h51m 6h08m 6h18m 0.99
2022-10-09 6h19m 6h53m 20h15m 20h49m 1
2022-10-10 6h20m 6h54m 20h13m 20h47m 0.98
2022-10-11 6h22m 6h55m 20h11m 20h45m 0.94
2022-10-12 6h23m 6h57m 20h10m 20h43m 0.88
2022-10-13 6h24m 6h58m 20h08m 20h42m 20h42m 21h00m 0.81
2022-10-14 6h25m 6h59m 20h06m 20h40m 20h40m 21h38m 0.73
2022-10-15 6h26m 7h00m 20h05m 20h38m 20h38m 22h24m 0.64
2022-10-16 6h28m 7h01m 20h03m 20h37m 20h37m 23h18m 0.55
2022-10-17 6h29m 7h03m 20h01m 20h35m 20h35m 0.45
2022-10-18 6h30m 7h04m 20h00m 20h33m 20h33m 0h18m 0.36
2022-10-19 6h31m 7h05m 19h58m 20h32m 20h32m 1h23m 0.27
2022-10-20 6h33m 7h06m 19h57m 20h30m 20h30m 2h29m 0.19
2022-10-21 6h34m 7h08m 19h55m 20h29m 20h29m 3h37m 0.12
2022-10-22 6h35m 7h09m 19h53m 20h27m 20h27m 4h45m 0.06
2022-10-23 6h36m 7h10m 19h52m 20h26m 20h26m 5h54m 0.02
2022-10-24 6h37m 7h11m 19h50m 20h24m 20h24m 6h37m 0
2022-10-25 6h39m 7h12m 19h49m 20h23m 20h23m 6h39m 0.01
2022-10-26 6h40m 7h14m 19h48m 20h21m 20h21m 6h40m 0.04
2022-10-27 6h41m 7h15m 19h46m 20h20m 20h20m 6h41m 0.1
2022-10-28 6h42m 7h16m 19h45m 20h19m 20h40m 6h42m 0.17
2022-10-29 6h44m 7h17m 19h43m 20h17m 21h37m 6h44m 0.27
2022-10-30 6h45m 7h19m 19h42m 20h16m 22h46m 6h45m 0.38
2022-10-31 6h46m 7h20m 19h41m 20h15m 6h46m 0.49

Twilight calendar was generated using Cartes du Ciel (Sky Charts).

See my blog post: Twilight Zone for the definitions of the different periods of twilight here: https://bobmoler.wordpress.com/2018/09/27/.

NASA Calendar of Planetary Events

Oct  1 	Sa            Venus: 5.8° W
     2  Su   3:32 pm  Moon South Dec.: 27.4° S
     2  Su   8:14 pm  First Quarter
     4  Tu   1:01 pm  Moon Perigee: 369,300 km
     5  We  11:51 am  Moon-Saturn: 4.1° N
     8  Sa   2:06 pm  Moon-Jupiter: 2.1° N
     8  Sa   4:59 pm  Mercury Elongation: 18° W (Morning elongation)
     9  Su   4:55 pm  Full Hunter's Moon
    11  Tu   5:49 pm  Moon Ascending Node
    12  We  11:46 pm  Moon-Pleiades: 2.9° N
    15  Sa  12:28 am  Moon-Mars: 4° S
    16  Su   2:12 am  Moon North Dec.: 27.5° N
    17  Mo   6:21 am  Moon Apogee: 404300 km
    17  Mo  11:41 am  Moon-Pollux: 2° N
    17  Mo   1:15 pm  Last Quarter
    21  Fr   1:39 pm  Orionid Shower: ZHR = 20
    22  Sa   4:47 pm  Venus Superior Conjunction. Enters evening sky
    25  Tu   6:49 am  New Moon
    25  Tu   7:00 am  Partial Solar Eclipse (Parts of Europe, Africa and Asia) 
    26  We   2:30 am  Moon Descending Node
    27  Th  10:48 pm  Moon-Antares: 2.3° S
    29  Sa  10:48 am  Moon Perigee: 368300 km
    29  Sa   9:04 pm  Moon South Dec.: 27.5° S
Nov  1  Tu            Venus: 2.6° E

All event times are given for UTC-4 hr: Eastern Daylight Saving Time.

Sky Events Calendar by Fred Espenak and Sumit Dutta (NASA’s GSFC),
http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html.

If you go to the above site, you can print out a list like the above for the entire year or calendar pages for your time zone.

Sun and Moon Rising and Setting Events

LU              Ephemeris of Sky Events for Interlochen/TC
October 2022          Local time zone: EDT
+-----------------------------------------------------------------------+
| DATE |  SUN     SUN  DAYLIGHT|   TWILIGHT*    |MOON  RISE OR    ILLUM |
|      |  RISE    SET    HOURS |  END    START  |PHASE SET** TIME FRACTN|
+=======================================================================+
|Sat  1| 07:40a  07:23p  11:42 | 08:26p  06:37a |      Set  10:44p   39%|
+------+-----------------------+----------------+-----------------------+
|Sun  2| 07:42a  07:21p  11:39 | 08:24p  06:39a |F Qtr Set  11:44p   50%|
|Mon  3| 07:43a  07:19p  11:36 | 08:22p  06:40a |      Set  12:55a   61%|
|Tue  4| 07:44a  07:17p  11:33 | 08:20p  06:41a |      Set  02:14a   72%|
|Wed  5| 07:45a  07:15p  11:30 | 08:18p  06:42a |      Set  03:33a   82%|
|Thu  6| 07:46a  07:14p  11:27 | 08:16p  06:43a |      Set  04:52a   90%|
|Fri  7| 07:48a  07:12p  11:24 | 08:15p  06:45a |      Set  06:08a   96%|
|Sat  8| 07:49a  07:10p  11:20 | 08:13p  06:46a |      Set  07:22a   99%|
+------+-----------------------+----------------+-----------------------+
|Sun  9| 07:50a  07:08p  11:17 | 08:11p  06:47a |Full  Rise 07:19p  100%|
|Mon 10| 07:51a  07:06p  11:14 | 08:09p  06:48a |      Rise 07:39p   99%|
|Tue 11| 07:53a  07:05p  11:11 | 08:08p  06:50a |      Rise 08:02p   95%|
|Wed 12| 07:54a  07:03p  11:08 | 08:06p  06:51a |      Rise 08:28p   90%|
|Thu 13| 07:55a  07:01p  11:05 | 08:04p  06:52a |      Rise 08:59p   83%|
|Fri 14| 07:57a  06:59p  11:02 | 08:02p  06:53a |      Rise 09:37p   75%|
|Sat 15| 07:58a  06:58p  10:59 | 08:01p  06:54a |      Rise 10:23p   66%|
+------+-----------------------+----------------+-----------------------+
|Sun 16| 07:59a  06:56p  10:56 | 07:59p  06:56a |      Rise 11:17p   57%|
|Mon 17| 08:00a  06:54p  10:53 | 07:58p  06:57a |L Qtr Rise 12:18a   47%|
|Tue 18| 08:02a  06:52p  10:50 | 07:56p  06:58a |      Rise 01:22a   38%|
|Wed 19| 08:03a  06:51p  10:47 | 07:54p  06:59a |      Rise 02:29a   29%|
|Thu 20| 08:04a  06:49p  10:44 | 07:53p  07:01a |      Rise 03:36a   20%|
|Fri 21| 08:06a  06:48p  10:41 | 07:51p  07:02a |      Rise 04:44a   13%|
|Sat 22| 08:07a  06:46p  10:38 | 07:50p  07:03a |      Rise 05:53a    7%|
+------+-----------------------+----------------+-----------------------+
|Sun 23| 08:08a  06:44p  10:36 | 07:48p  07:04a |      Rise 07:04a    3%|
|Mon 24| 08:10a  06:43p  10:33 | 07:47p  07:06a |      Rise 08:18a    0%|
|Tue 25| 08:11a  06:41p  10:30 | 07:45p  07:07a |New   Set  06:53p    0%|
|Wed 26| 08:12a  06:40p  10:27 | 07:44p  07:08a |      Set  07:21p    3%|
|Thu 27| 08:14a  06:38p  10:24 | 07:42p  07:09a |      Set  07:55p    8%|
|Fri 28| 08:15a  06:37p  10:21 | 07:41p  07:10a |      Set  08:39p   16%|
|Sat 29| 08:16a  06:35p  10:18 | 07:40p  07:12a |      Set  09:36p   25%|
+------+-----------------------+----------------+-----------------------+
|Sun 30| 08:18a  06:34p  10:16 | 07:38p  07:13a |      Set  10:45p   36%|
|Mon 31| 08:19a  06:32p  10:13 | 07:37p  07:14a |      Set  12:02a   47%|
+-----------------------------------------------------------------------+
* Nautical Twilight
** Moonrise or moonset, whichever occurs between sunrise and sunset

Generated using my LookingUp for DOS program.

09/28/2022 – Ephemeris – Searching for the naked-eye planets for this week

September 28, 2022 Comments off

This is Bob Moler with Ephemeris for Wednesday, September 28th. Today the Sun will be up for 11 hours and 51 minutes, setting at 7:28, and it will rise tomorrow at 7:38. The Moon, 3 days past new, will set at 8:51 this evening.

Let’s search for the naked-eye planets for this week. The thin sliver of a waxing crescent Moon may be visible very low in the southwest at 8 pm. We’re back to two naked-eye planets in the evening sky. Jupiter was in opposition from the Sun on Monday, and closest to the Earth. As it gets darker, Jupiter will be seen first low in the east. At that time, Saturn can be seen in the southeast. Jupiter is seen against the stars of Pisces the fish, while Saturn is spotted in the eastern end of Capricornus the sea goat. At 6:45 tomorrow morning, Mars will be high in the south, above the winter constellation of Orion, and Jupiter will be very low in the west. Venus will rise in the east at 7:02 into bright twilight.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Three day old Moon in twilight

What the three-day-old Moon might look like in binoculars in twilight at 8 pm tonight, September 28, 2022. Illumination of the night part of the Moon will be provided by the bright gibbous Earth in its sky. The phenomenon is called earth shine. Created using Stellarium.

Evening planets finder animation

Evening planet finder animation by showing Jupiter and Saturn with and without the constellation lines. For 9 pm this evening, September 28, 2022. Click on the image to enlarge it. Created using Stellarium and GIMP.

Morning planets and bright winter stars

Morning planet Mars with the last gasp of the new evening planet Jupiter and bright winter stars at 6:45 tomorrow morning, September 29, 2022. Click on the image to enlarge it. Created using Stellarium.

Telescopic views of Saturn Jupiter and Mars

Telescopic views of Saturn, Jupiter and Mars (north up) as they would be seen in a small telescope, with the same magnification. The image doesn’t show it, but the white north polar cap will appear at the top or north limb of Mars. Saturn and Jupiter are shown at 10 pm, Mars at 6 am. Apparent diameters: Saturn 18.17″, its rings 42.33″; Jupiter 49.86″. Mars 11.01″. Mars’ distance is 73.8 million miles (118.7 million kilometers). The ” symbol means seconds of arc (1/3600th of a degree.) Created using Cartes du Ciel (Sky Charts).

One surprising thing about Mars in a telescope is how bright it is. That’s because it’s much closer to the Sun than Jupiter or Saturn, even thought it has a lower albedo (reflectance) than those planets.

Planets and the Moon on a single night

The naked-eye planets and the Moon at sunset and sunrise on a single night, starting with sunset on the right on September 28, 2022. The night ends on the left with sunrise on the 29th. Click on the image to enlarge it. Created using my LookingUp program and GIMP.

09/27/2022 – Ephemeris – Finding the constellation of Perseus the hero

September 27, 2022 Comments off

This is Ephemeris for Tuesday, September 27th. Today the Sun will be up for 11 hours and 54 minutes, setting at 7:30, and it will rise tomorrow at 7:37. The Moon, 2 days past new, will set at 8:28 this evening.

Close to the horizon, but rising in the northeast in the evening, is the constellation of Perseus the Greek hero, holding as his prize the severed head of Medusa. To me, the stars don’t seem to match the figure in the stars. It’s either the Greek letter pi (π) tilted to the left or the cartoon roadrunner running up the sky. Perseus’ brightest star is Mirfak in the middle of the top of the letter π, or back of the roadrunner. Using a pair of binoculars to look towards Mirfak, one can see many more stars, just below naked eye visibility near it. It’s a very loose star cluster called the Alpha (α) Persei Association, α Persei being a catalog designation for Mirfak. And Mirfak is actually in the association. Unlike some bright stars, who are just foreground stars.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

For my take on the mythology featuring Perseus, see The Great Star Story of Autumn. It’s way too long for my short radio program. For Hollywood’s treatment of the story, see Clash of the Titans.

Perseus finder animation

Perseus finder using the animated GIF to show the star field, constellation lines and names, and Perseus as art. Cassiopeia is included as a means to find the dimmer Perseus below it on autumn evenings. Algol, another important star and the second-brightest star of Perseus, is also labeled. I normally cover it around Halloween, but if you can’t wait, type Algol in the search box at the upper right. Created using Stellarium, LibreOffice Draw, and GIMP.

Alpha Persei Association

The Alpha Persei Association. The brightest star is Mirfak (Alpha Persei). This is a small section of a photograph taken February 18, 2017, Canon EOS Rebel T5, 121 seconds, f/3.5, 18 mm fl., ISO 3200. Credit Bob Moler.

09/20/2022 – Ephemeris – Finding the constellation of Pegasus the flying horse

September 20, 2022 Comments off

This is Ephemeris for Tuesday, September 20th. Today the Sun will be up for 12 hours and 16 minutes, setting at 7:43, and it will rise tomorrow at 7:28. The Moon, 3 days past last quarter, will rise at 2:33 tomorrow morning.

Rising about a third of the way up the sky in the east as it gets dark around 9 pm can be found one of the great autumn constellations: Pegasus the flying horse of Greek myth. Its most visible feature is a large square of four stars, now standing on one corner. This feature, called the Great Square of Pegasus, represents the front part of the horse’s body. The horse is quite aerobatic, because it is seen flying upside down. Remembering that fact, the neck and head is a bent line of stars emanating from the right corner star of the square. Its front legs can be seen in a gallop extending to the upper right from the top star of the square. From the left star extend, not hind legs but the constellation of Andromeda, the princess rescued with the help of Pegasus.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Pegasus-Andromeda finder

Pegasus & Andromeda animated finder chart for 9 pm in mid-September. To the upper left are most of the stars of the “W” shape of Cassiopeia the queen, Andromeda’s mother. Created using Stellarium and GIMP.

Pegasus, Andromeda and Cassiopeia plus other constellations are characters in the great star story of autumn which I relate here.

09/19/2022 – Ephemeris – Finding the constellation Cepheus

September 19, 2022 Comments off

This is Ephemeris for Monday, September 19th. Today the Sun will be up for 12 hours and 19 minutes, setting at 7:45, and it will rise tomorrow at 7:27. The Moon, 2 days past last quarter, will rise at 1:30 tomorrow morning.

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 modern 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 astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). 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. Also labeled is Delta (δ) Cephei. Created using Stellarium and GIMP.

Delta_Cephei_lightcurve

Light Curve of Delta Cephei. The pulsation period is 5.367 days. Note the Magnitude vertical axis, the lower the magnitude the brighter the star is. Blame that on the Greek astronomer Hipparchus, 2nd century BC. It’s like golf scores; the lower the score, the better the golfer, and for magnitudes, the brighter the star. Credit: Thomas K Vbg – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13887639.

09/16/2022 – Ephemeris – Alberio: a double star that showcases star colors

September 16, 2022 Comments off

This is Ephemeris for Friday, September 16th. Today the Sun will be up for 12 hours and 28 minutes, setting at 7:51, and it will rise tomorrow at 7:24. The Moon, 1 day before last quarter, will rise at 11:03 this evening.

Alberio is the name given to the star that is in the head of the constellation of Cygnus the swan, which is high in the east these evenings. It is also at the foot of the asterism or informal constellation of the Northern Cross. To the naked eye Albireo looks like a single star, however even in small telescopes its true nature is revealed. It’s a double star whose individual star colors are strikingly different Its brightest star is yellow, and the dimmer star is blue. While star colors are subtle, these two, due to their apparent closeness, make an obvious color contrast. Unlike what your interior decorator says: In stars, blue is hot, yellow, orange and red are cool. The two stars are too far apart to be considered a binary star system, but appear to move together in space. It is what is called an optical double, though they’re both around 430 light years away.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Albireo finder animation

Animated Albireo finder chart. Albireo is located in the head of Cygnus the swan, or at the base of the Northern Cross. Tagged stars are, beside Albireo, the stars of the Summer Triangle: Deneb, Vega and Altair plus the star at the junction of the upright and crosspiece of the cross, Sadr. Created using Stellarium.

Albireo photographed in a telescope

Albireo, captured at high magnification by the staff of the Smithsonian Institution. Informally, at star parties, I call it the U of M Star because it displays the University of Michigan’s Maize and Blue colors.

A note about star colors

The color of a star is dependent on its surface temperature. The term surface is a misnomer, because stars do not have a surface, at least not a solid one, being gaseous in nature. The only exception I can think is a neutron star, which is packed with neutrons. We consider the Sun’s photosphere synonymous with “surface”. The photosphere of the Sun is where the energy transport from the core changes from convection to radiation. The color of the Sun is a measure of the temperature of the photosphere. The color sequence from the coolest to the hottest is: red, orange, yellow, white and blue. The light emitted by a star is not a pure color, but a distribution of colors, whose peak shifts along that range. There is much more to tell, but that’s beyond the scope of this post.

09/15/2022 – Ephemeris – Finding Cassiopeia this time of year

September 15, 2022 Comments off

This is Ephemeris for Thursday, September 15th. Today the Sun will be up for 12 hours and 31 minutes, setting at 7:53, and it will rise tomorrow at 7:22. The Moon, 2 days before last quarter, will rise at 10:30 this evening.

In the northeastern sky is a letter W shaped constellation of Cassiopeia, the queen of Greek myth. I can’t say Cassiopeia is rising in the northeast, because it never sets for us in northern Michigan. This time of year it skirts above the northern horizon during the daytime. One of Cassiopeia’s claims to historical astronomical fame is that it’s the location of Tycho’s Star, a supernova discovered in 1572 by Danish astronomer Tycho Brahe, the last of the great astronomers prior to the invention of the telescope. Tycho was able to prove that the temporary phenomenon was actually a star in the heavens, disproving the Greek notion that the heavens were changeless and perfect. The Chinese had already known that, calling them Guest Stars.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Cassiopeia finder animation

Cassiopeia finder animation for 10 pm tonight, September 15th. One cannot miss the distinctive W. Created using Stellarium.

Tycho's Supernova 1574A

Tycho’s Supernova 1574A, as simulated in Stellarium for mid-November 1572.

Tycho's Supernova remnant seen in x-rays

Tycho’s Supernova remnant, seen in x-rays by the orbiting Chandra X-ray Observatory. Credit: NASA / Chandra

09/08/2022 – Ephemeris – We are going to have an early Harvest Moon this year

September 8, 2022 Comments off

This is Bob Moler with Ephemeris for Thursday, September 8th. Today the Sun will be up for 12 hours and 53 minutes, setting at 8:06, and it will rise tomorrow at 7:14. The Moon, 2 days before full, will set at 5:54 tomorrow morning.

We are going to have an early Harvest Moon this year, on the early morning of Saturday the 10th, this Saturday coming up. The Harvest Moon is the closest full moon to the autumnal equinox, which is on the 22nd. The earliest a Harvest Moon can fall is on the 8th of September. The reason that the Harvest Moon is so famous is that at sunset the Moon’s path, in the sky, is shallow to the horizon. So it rises much less than its average 50 minutes later each night. This effectively lengthens the amount of useful twilight, allowing more time to harvest the crops. It compensated for the rapid retreat of the daylight hours this time of year. It’s not so important now, but back before electric lights it definitely was.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Harvest Moon Rising ala The Harvest Moon rising as seen in StellariumStellarium

The Harvest Moon rising as seen in Stellarium. The planetarium program Stellarium, which I use a lot, also colors the rising and setting Moon and Sun. It also reproduces the effect of atmospheric refraction, which makes objects close to the horizon look higher than they are. Thus, extended objects close to the horizon appear squashed a bit vertically.

 

The Harvest Moon Effect diagram

The Harvest Moon effect is a phenomenon where the Moon’s nightly advance in rising times become much shorter than the average 50 minutes. This has the effect of extending the bright part of twilight for up to a week near the Harvest Moon. Complicating effects this year are the fact that the Harvest Moon is a supermoon, being a bit brighter than normal, and also moving faster than normal, negating the harvest moon effect somewhat. The Moon’s perigee was on the 7th, so the Moon is slowing down*, which shows in the delay numbers. Also helping to shorten the delay is that the path of the Moon is a bit shallower than the ecliptic. The Moon is south of the ecliptic, heading northward to its ascending node.

The Moon moves fastest in its orbit at perigee, and its slowest at apogee, at its farthest from the Earth.