Archive
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.
06/05/2023 – Ephemeris – Venus was it’s farthest apparent distance from the Sun yesterday
This is Ephemeris for Monday, June 5th. Today the Sun will be up for 15 hours and 25 minutes, setting at 9:24, and it will rise tomorrow at 5:58. The Moon, 2 days past full, will rise at 11:47 this evening.
Yesterday, Venus was as far away from the Sun as it gets in this evening appearance of Venus. The event is called greatest eastern elongation, meaning it’s as far to the east of the Sun as it gets. Both Venus and Mercury have these events, because they orbit the Sun inside of the Earth’s orbit, they never stray far from the Sun. In less than two and a half months, Venus will leave the evening sky, pass between the Earth and Sun in inferior conjunction, and enter the morning sky. Until then Venus will get larger in telescopes and become a thinner and thinner crescent, as we see more of its night side and less of its day side. By mid July, Venus should appear large enough to see its tiny crescent in a pair of binoculars.
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
05/31/2023 – Ephemeris – Let’s find where the naked-eye planets have wandered off to this week
This is Bob Moler with Ephemeris for Wednesday, May 31st. Today the Sun will be up for 15 hours and 19 minutes, setting at 9:20 pm, and it will rise tomorrow at 6 am. The Moon, 3 days before full, will set at 4:19 am tomorrow.
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 has moved into Cancer, and is seen above and left of Venus by 12 degrees, or a bit more 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. In the morning, Saturn will be visible low in the southeast at 5 am, rising at 2:28 am. Jupiter makes its morning appearance and is low in the east-northeast at that hour, rising at 4:27 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
05/30/2023 – Ephemeris – The Terminator… No, not Arnold Swartzenegger
This is Ephemeris for Tuesday, May 30th. Today the Sun will be up for 15 hours and 17 minutes, setting at 9:19, and it will rise tomorrow at 6:01. The Moon, 3 days past first quarter, will set at 3:59 tomorrow morning.
The Moon tonight is getting to be a fatter and fatter gibbous phase, until Saturday, when it will be full. The Moon will be blindingly bright in telescopes of low magnification. As always the case with the Moon, the most detail is seen near the terminator. The terminator, in the case of the waxing moon, is the sunrise line. After full moon, the terminator becomes the sunset line. This is where the shadows are longest, showing the detail of the craters. Farther from the terminator, where the Sun is higher in the Moon’s sky, shadows are short or nonexistent. Giving the surface a flat appearance. Even lacking wind and water, there is still erosion on the Moon, coming from meteoroid and asteroid impacts and their ejecta. And the breakdown of rocks due to the extreme day-night temperature swings.
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
05/29/2023 – Ephemeris – Sinus Iridium, a hook into night
This is Bob Moler with Ephemeris for Memorial Day, Monday, May 29th. Today the Sun will be up for 15 hours and 16 minutes, setting at 9:18, and it will rise tomorrow at 6:01. The Moon, 2 days past first quarter, will set at 3:41 tomorrow morning.
Let’s look at the Moon tonight. One of my favorite formations is coming into light. It is called Sinus Iridium or Bay of Rainbows. Sorry, there’s no color here. But if caught at right time, and tonight’s the night, this ruined crater will appear as a hook out into night off the upper left edge of the moon. Officially it’s a bay to the Sea of Showers or Mare Imbrium. The north edge of the bay are mountains called the Jura Mountains. The south edge disappears into Mare Imbrium. The floor of the Sinus Iridium is about twelve hundred feet lower than Mare Imbrium. The transition is gradual because it isn’t very noticeable. The formation is large enough to be seen in binoculars. Sinus Iridium is 242 miles wide, a good tenth the diameter of the Moon itself.
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
05/24/2023 – Ephemeris – Let’s find where the naked-eye planets have wandered off to this week
This is Ephemeris for Wednesday, May 24th. Today the Sun will be up for 15 hours and 7 minutes, setting at 9:13, and it will rise tomorrow at 6:05. The Moon, 3 days before first quarter, will set at 1:59 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 will appear below the Moon tonight. It has moved into Cancer, and is seen above and left of Venus by 14 degrees, or one and a half times 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. In the morning, Saturn will be visible and low in the southeast at 5 am, rising at 2:47 am. Jupiter makes its morning appearance and is very low in the east-northeast 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
Evening planets and the Moon at 10 pm tonight, May 24, 2023. Created using Stellarium, LibreOffice Draw and GIMP.
5 day old Moon with selected features labeled for May 24, 2023, at 10 pm. Created using Stellarium, LibreOffice and GIMP.
Saturn and Jupiter in early morning twilight at 5:00 am tomorrow, May 25, 2023. Created using Stellarium.
Telescopic Venus, Saturn and Jupiter (north up) as they would be seen in a small telescope, with the same magnification. Apparent diameters: Venus 21.03″ and is 55.4% illuminated; Saturn 16.96″, its rings 39.52″; Jupiter 34.07″. Mars, too small to be represented here, is 4.81″ in diameter. The ” symbol means seconds of arc (1/3600th of a degree.) Created using Cartes du Ciel (Sky Charts).
The naked-eye planets and the Moon at sunset and sunrise on a single night, starting with sunset on the right on May 24, 2023. The night ends on the left with sunrise on the 25th. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.
05/22/2023 – Ephemeris – Exploring the three-day-old Moon
This is Ephemeris for Monday, May 22nd. Today the Sun will be up for 15 hours and 4 minutes, setting at 9:11, and it will rise tomorrow at 6:06. The Moon, 3 days past new, will set at 12:43 tomorrow morning.
Tonight we will see the three-day-old moon low in the west. It may exhibit earthshine. That is, its night side will be illuminated by the Earth’s day side. Just as the earthly night is illuminated by moonlight, especially when the Moon is near full, the night side of the Moon, when near new, is illuminated by earthlight. In binoculars or telescope, the large dark spot, on the Moon’s right edge, is Mare Crisium, or Sea of Crises. The large crater below and a bit left of that sea is Langrenus, named after a 17th century Belgian engineer and mathematician who produced the first lunar map with nomenclature. Langrenus appears as a bright spot as the Sun rises higher for it. Also check out the south end of the cusp of the crescent for a lone mountain peak catching the Sun.
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
An annotated three old Moon as it might appear in binoculars or a small telescope tonight, May 22, 2023, at 10 pm. Click or tap on the image to enlarge it. Created using Stellarium, LibreOffice Draw and GIMP.
05/18/2023 – Ephemeris – Spica, the bluest first magnitude star
This is Bob Moler with Ephemeris for Thursday, May 18th. Today the Sun will be up for 14 hours and 55 minutes, setting at 9:07, and it will rise tomorrow at 6:10. The Moon, 1 day before new, will rise at 5:56 tomorrow morning.
In the south at 11 p.m. is the bright star Spica, which can be found from all the way back overhead to the Big Dipper. Follow the arc of the handle of the Big Dipper to the bright star Arcturus high in the southeast. Then straighten the curve of the arc to a straight spike which points to Spica, the brightest star in Virgo the virgin. Arcturus is much brighter than Spica and has an orange tint to Spica’s bluish hue. In fact, Spica is the bluest of the 21 first magnitude stars. That means that it has a really hot surface temperature. Actually, Spica is really two blue stars orbiting each other in 4 days. Spica is 250 light years away. It also was an important star to the ancient Greeks. One temple was built, and aligned to its setting point.
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
Finding Virgo from the Big Dipper at 10:30 pm, May 18th. There are no planetary interlopers this year. The small + sign marks the zenith, and the image faces south. Created using my LookingUp app, with captions added using LibreOffice Draw.
05/17/2023 – Ephemeris – Let’s find where the naked-eye planets have wandered off to this week
This is Bob Moler with Ephemeris for Wednesday, May 17th. Today the Sun will be up for 14 hours and 53 minutes, setting at 9:06, and it will rise tomorrow at 6:11. The Moon, 2 days before new, will rise at 5:30 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 has moved into Cancer, left of the namesake stars of the Gemini twins, with Pollux closest to Mars and Castor farther right. Mars is above and left of Venus by 18 degrees, or a bit less than two times 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. In the morning, Saturn will be visible, low in the east-southeast by 5 am, rising at 3:18 am. This morning, the Moon is covering or occulting Jupiter. Daylight is making this a telescopic event.
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 with the stars at 10 pm tonight, May 17, 2023. Created using Stellarium and LibreOffice Draw.
Saturn in morning twilight at 5:30 am tomorrow, May 18, 2023. Created using Stellarium.
Telescopic Venus and Saturn (north up) as they would be seen in a small telescope, with the same magnification. Apparent diameters: Venus 19.65″ and is 58.9% illuminated; Saturn 16.77″, its rings 39.05″. Mars, too small to be represented here, is 4.96″ in diameter. Created using Cartes du Ciel (Sky Charts).
The naked-eye planets and the Moon at sunset and sunrise on a single night, starting with sunset on the right on May 17, 2023. The night ends on the left with sunrise on the 18th. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.
05/16/2023 – Ephemeris – Regulus, the Little King Star
This is Ephemeris for Tuesday, May 16th. Today the Sun will be up for 14 hours and 51 minutes, setting at 9:05, and it will rise tomorrow at 6:12. The Moon, 3 days before new, will rise at 5:08 tomorrow morning.
Regulus is the brightest star in the constellation of Leo, the lion at the bottom of the backward question mark that is the head and mane of Leo. It’s in the southwest at 10 pm. Alluding to the lion’s status in the animal kingdom, Regulus is the little king star. It is dead last in order of brightness of the 21 brightest first magnitude stars, 1/13th the brightness of Sirius the brightest nighttime star, now lost in the evening twilight glow. To the Babylonians it was the king, the 15th of their constellations, that marked the passage of the Sun. Regulus is about 79 light years away, and 288 times the brightness of the sun. It is a rapidly spinning ellipsoid 3 times the sun’s diameter, rotating in just under 16 hours.
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
Regulus and Leo and the other stars and planets in the western sky at 11 pm, May 16, 2023. Created using Stellarium.
