Archive
06/16/2023 – Ephemeris – Twilight is longer near the summer solstice
This is Ephemeris for Friday, June 16th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:30, and it will rise tomorrow at 5:56. The Moon, 2 days before new, will rise at 5:04 tomorrow morning.
Not only does the Sun set later this time of year, but twilight lasts longer too. As of tonight the end of astronomical twilight, when the last vestiges of twilight are gone is, for the Traverse City/Interlochen area, 12:01 am, That’s two and a half hours of evening twilight. I feel that for most purposes that the end of nautical twilight, when navigators on ships could no longer see the horizon for their sextant readings, is dark enough to view most stars, and brighter objects beyond the solar system, what we call deep sky objects. That happens at 10:56 pm, or about an hour and a half after sunset. Twilight of both kinds are a third shorter around the equinoxes. These times are dependent on our latitude, and the Sun’s declination which is equivalent to latitude.
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
Check out my September 27, 2018 post about the different twilight periods.
06/15/2023 – Ephemeris – Today we have the earliest sunrise of the year
This is Ephemeris for Thursday, June 15th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:30, and it will rise tomorrow at 5:56. The Moon, 3 days before new, will rise at 4:28 tomorrow morning.
Today is the day of the earliest sunrise, though the time will stay within the same minute for a few days. In six days the Sun will reach it’s farthest north in our sky. And be above the horizon for fifteen hours and thirty four minutes. That’s the summer solstice for those living in the north hemisphere. It’s also known as the longest day. The retired computer programmer in me likes to take things literally, so no, June 21st, the summer solstice is not the longest day. It’s 24 hours long, like any other day, however it has the longest daylight hours. Daylight hours being defined as the time interval from sunrise to sunset, which, in Interlochen and Traverse City, is 15 hours 34 minutes. Five or six days later, we’ll have the latest sunset.
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
If the Earth had no axial tilt and had a circular orbit of the Sun, The earliest sunrise and latest sunset would occur on the summer solstice. But since that is not the case the Earth’s axial tilt and elliptical orbit cause the the earliest sunrise and latest sunset to differ from each other and the summer solstice.
06/14/2023 – Ephemeris – Let’s find out where the naked-eye planets have wandered off to this week
This is Bob Moler with Ephemeris for Flag Day, Wednesday, June 14th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:29, and it will rise tomorrow at 5:56. The Moon, half way from last quarter to new, will rise at 3:59 tomorrow morning.
Let’s find out where the naked-eye planets have wandered off to this week. Venus is our blazing Evening Star seen in the west all evening. It will set after midnight. The red planet Mars is seen left of and a bit higher than Venus by six and a half degrees, or a bit more than half the width of one’s fist held at arm’s length. Venus is closing the gap between them, but will never quite reach Mars while they are in the evening sky. The closest they will get is three and a half degrees or seven moon diameters apart, before Venus pulls back toward the Sun faster than Mars will. Both Mars and Venus are in Cancer. In the morning, Saturn will be visible low in the south-southeast at 5 am. Jupiter will be very low in the east at that hour.
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
06/13/2023 – Ephemeris – Messier 13, the Great star cluster in Hercules
This is Bob Moler with Ephemeris for Tuesday, June 13th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:29, and it will rise tomorrow at 5:56. The Moon, 3 days past last quarter, will rise at 3:34 tomorrow morning.
About a third of the way between the bright stars Vega which is high in the east and Arcturus, high in the south, can be found the Keystone of Hercules, a four-star box wider at the top than at the bottom. Along the right edge, a third of the way down is what looks like a faint star to someone with really good vision. In binoculars the star becomes fuzzy. One needs a larger telescope probably six or eight inches in diameter to begin to see some stars among the fuzziness. That is a globular star cluster containing hundreds of thousands of stars. This is the Great Hercules Globular Star Cluster. It’s beautiful if seen in a large telescope, such as the one brought out to the star parties at the Sleeping Bear Dunes, especially in August and September.
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
Dan’s image is rotated from Scott’s. The bright star at the lower left of Scott’s image is the same as the one at the lower left of Dan’s.
Globular star clusters are uniformly very old. M 13 is estimated to be between 11 and 12 billion years old, more than twice as old as our Sun and the solar system. As I say in my talks: “They don’t make them like that any more.” Globular clusters form a spherical distribution around the Milky Way galaxy with an increasing concentration toward the center. Do they reveal the original spherical shape of the galaxy before the gas and dust collapsed into the disk of the galaxy we see today? The star clusters that form today lie in the disk, and contain a few hundreds or a thousand stars. They are called open or galactic star clusters. The Pleiades is the most famous example of this type of star cluster.
06/12/2023 – Ephemeris -Finding Hercules among the stars
This is Ephemeris for Monday, June 12th. Today the Sun will be up for 15 hours and 31 minutes, setting at 9:28, and it will rise tomorrow at 5:56. The Moon, 2 days past last quarter, will rise at 3:13 tomorrow morning.
Orion, the hard luck mythical Greek hunter, gets a splashy constellation in the winter sky, but the greatest hero of all, Hercules, gets a dim group of stars on the border between the spring and summer stars. At 11 p.m. Hercules is high in the east-southeast. It is located above and right of the bright star Vega, in the east. Hercules’ central feature is a keystone shaped box of stars, called, of course, the Keystone of Hercules tilted to the left, which represents the old boy’s shorts. From the top and left corner stars extend lines of stars that are his legs, from the bottom and right stars, the rest of his torso and arms extend. So in one final indignity, he’s upside down in our sky. For those with a telescope, Hercules contains the beautiful globular star cluster Messier 13.
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
06/09/2023 – Ephemeris – How to find Corona Borealis, the Northern Crown
This is Bob Moler with Ephemeris for Friday, June 9th. Today the Sun will be up for 15 hours and 29 minutes, setting at 9:27, and it will rise tomorrow at 5:57. The Moon, 1 day before last quarter, will rise at 2:13 tomorrow morning.
High in the southeast at 11 p.m. can be found a small but easily spotted constellation of Corona Borealis, the Northern Crown. It is located just east or left of the kite shaped constellation of Boötes, with its bright star Arcturus at the bottom. The Northern Crown is a three-quarters circle of stars, like a tiara, with a brighter star Alphecca at the bottom. Alphecca in Arabic means “Bright star of the broken ring of stars”. According to Greek mythology it belonged to Princess Ariadne, daughter of King Minos of Crete who helped Theseus escape from the Labyrinth of the Minotaur, only to be abandoned by him on an island. To the Native Chippewa and Ottawa of our area it is the Sweat Lodge.
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
Next Monday I will post about Hercules.
06/08/2023 – Ephemeris – The first stars that appear tonight
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06/07/2023 – Ephemeris – Let’s find where the naked-eye planets have wandered off to this week
This is Bob Moler with Ephemeris for Wednesday, June 7th. Today the Sun will be up for 15 hours and 27 minutes, setting at 9:25, and it will rise tomorrow at 5:57. The Moon, 3 days before last quarter, will rise at 1:18 tomorrow morning.
Let’s find where the naked-eye planets have wandered off to this week. Venus is our blazing Evening Star seen in the west all evening. It will set after midnight. The red planet Mars is seen left of and a bit higher than Venus by eight and a half degrees, or a bit less than the width of one’s fist held at arm’s length. Venus is closing the gap between them, but will never quite reach Mars while they are in the evening sky. The closest they will get is three and a half degrees or 7 moon diameters apart, before Venus pulls back toward the Sun faster than Mars will. Both Mars and Venus are in Cancer. In the morning, Saturn will be visible low in the southeast at 5 am, rising at 1:53 am. Jupiter is low in the east at that hour, rising at 3:57 am.
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
06/06/2023 – Ephemeris – Venus: sister planet or evil twin?
This is Ephemeris for Tuesday, June 6th. Today the Sun will be up for 15 hours and 26 minutes, setting at 9:25, and it will rise tomorrow at 5:57. The Moon, 3 days past full, will rise at 12:39 tomorrow morning.
Venus has been called Earth’s sister planet, because it is nearly the same size as the Earth, only 5% smaller. It has also been called Earth’s evil twin. That was suspected as far back as 1962 when NASA’s Mariner 2 spacecraft flew past the planet and observed the planet in the infrared and microwaves. It found that though the cloud tops were relatively cool, the surface was extremely hot, averaging 867 ° Fahrenheit (464° Celsius). Venus cloud tops are featureless visually, but do show variation in the infrared and ultraviolet. Radar observations from Arecibo, and spacecraft have penetrated the clouds, showing a bleak landscape of volcanoes and lava flows. After many tries the Soviet Union successfully landed probes on it.
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
06/05/2023 – Ephemeris Extra – Venus prepares to leave the evening sky
Based on the article of the same name printed in the Grand Traverse Astronomical Society’s June Stellar Sentinel newsletter.
Venus will not only leave the evening sky in dramatic fashion, but will enter the morning sky in an even more dramatic fashion in the latter half of August. Venus takes 225 days to orbit the Sun, but from an Earth also orbiting the Sun, the period from successive inferior or superior conjunctions of the Sun take 584 days or 19.2 months (1 year 7.2 months), or 9.6 months in the evening and morning skies respectively.
The interval from greatest eastern elongation, and inferior conjunction, when Venus passes between the Sun and the Earth is around 70 days. On June 4th, Venus will be at its greatest eastern elongation. The sight line from the Earth to Venus will be tangent to Venus’ orbit. Any Venusians, floating above their clouds, would see the Earth at quadrature, that is 90 degrees from the Sun.
Venus, at greatest eastern elongation, is heading straight toward us, so it will grow rapidly in apparent size. Venus begins the month with an apparent diameter of 22.9”. (” means seconds of arc. 1 second of arc = 1/3600 of a degree). At the end of the month Venus will have increased in apparent size to 33.5”, as can be seen with the illustration below. For comparison, Jupiter’s average apparent diameter is around 41”.
Sometime in July Venus will appear large enough to be able to detect it’s crescent phase in seven power binoculars. At inferior conjunction its apparent size will grow to 57.8”. Pity there won’t be a transit of Venus of the Sun to see it. By the way, if you missed the transits of 2004 and 2012, you won’t see another, unless you are a small child now, and will live to a very old age. There won’t be another transit of Venus until 2117.
The Mayan culture of Central America and the Yucatan Peninsula based one of their calendars on the Venus Cycle. It turns out that five Venus cycles equals a period just shy of eight years. That’s why we had 2 Venus transits eight years apart, June 8, 2004 and June 6, 2012. The next transits will be December 11, 2117 and December 8, 2125.
The Dresden Codex is one of only a handful of surviving Mayan books. It has a whole section on the Venus Cycle and how it fits into an 8 year Sequence. 13 eight year sequences equals 104 years, a Venus Round. Well, not quite, 103.91 years actually.
Venus has been ignored by NASA since the Magellan mission in the 1990s which mapped the surface through the clouds with radar. Recent reexamination of the results have suggested that there may have been relatively recent volcanism on the planet, even during the period that Magellan was imaging the surface of the planet.
NASA plans two missions to the planet toward the end of this decade. VERITAS stands for “Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy” it’s a satellite map the surface in much greater detail than Magellan did. It will also map infrared emissions from Venus’ surface to map rock types.
DAVINCI+ stands for “Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging” and will drop through the atmosphere taking measurements, and will take images of the surface like the Huygens probe did on Saturn’s largest moon Titan back in 2005.
In the past the Soviet Union sent landers and floated balloons in Venus’ atmosphere. The only active spacecraft that I know of orbiting Venus now is Japan’s Akatsuki, which is studying its atmosphere. However spacecraft using Venus as a gravity assist to get to Mercury or close to the Sun, have turned their instruments to Venus as they passed by.
Major Venusian events for the rest of 2023 (Eastern Time)
- June 4, 6:59 am – Venus at greatest eastern elongation 45.4°
- June 13, 7:05 am – Venus 0.5° north of the Beehive cluster
- June 21, 8:47 pm – Venus 4.1° south of the Moon
- July 1, 2:48 am – Venus in a quasi-conjunction with Mars, separation 3.6°
- July 7 – Greatest brilliancy, magnitude -4.7 (~36 days before inferior conjunction)
- July16, 3:49 am – Venus in a quasi-conjunction with Regulus
- July 27, 7:00 am – Mercury 5.1° north of Venus
- August 13, 7:10 am – Venus at inferior conjunction, 7.4° south of the Sun
- September 19 – Greatest brilliancy. Magnitude -4.8
- October 9, 2:10 am – Venus 2.3° south of Regulus
- October 23, 5:59 pm – Venus greatest western elongation 46.4°
- November 9, 4:28 am – Venus 1.1° south of the Moon
- November 29, 5:29 am – Venus 4.2°north of Spica
- December 9, 11:53 am – Venus 3.9° north of the Moon
Created from NASA’s SKYCAL Sky Events Calendar.
Bob Moler's Ephemeris Blog 