Ephemeris Extra – Transit of Mercury
Transit of Mercury – May 9, 2016*
Monday, May 9th the planet Mercury will cross in front the Sun in an event called a transit. Transits of Mercury are not as rare as those of Venus. No one alive who saw that last transit of Venus, will see the next in 2117. The last transit of Mercury was in 2006, and the next will be in 2019, though it’s a long jump to the transit after that in 2032.
Occult4’s geocentric ingress time is 7:12 a.m. (11:12 UT) at position angle 83.1° Farthest penetration onto the Sun’s face is 10:57 a.m. (14:57 UT) Egress time is 2:42 p.m. (18:42 UT) at position angle 224.4°. Position angle is measured from the North point on the Sun counterclockwise.
The track of Mercury across the face of the Sun. Mercury will travel from upper left to lower right. Mercury will not be visible until it impinges upon the disk of the Sun. Credit IOTA’s program Occult4.
Looking at the Sun normally from northern Michigan, Mercury’s ingress point is close to the 8 o’clock point on its edge, since the Sun will rise tilted to the left nearly 45°. Mercury is tiny, 6.8 seconds of arc in diameter, and will be very hard to spot, smaller than most sunspots. Venus was nearly 58 seconds of arc in diameter when it transited the Sun in 2012.
Since Mercury is invisible before the transit starts. Checking out the Sun in the telescope and moving it in right ascension and declination or altitude and azimuth and altitude so the ingress point can be determined. Newtonian telescopes give an upside down image, actually rotated 180°. Refractors and Schmidt or Maksutov telescopes generally give a mirror reversed image due to the diagonal mirror that the eyepiece is placed into. The image is right side up or upside down depending on the rotation of the diagonal.
The use of a Hydrogen Alpha solar telescope allows an early peek at the transit. These telescopes look at the Sun’s chromosphere, a layer of gas 6,000 miles thick directly above the photosphere. Since the chromosphere is twice as thick as the diameter of Mercury. This should give you a few minutes heads up before white light telescopes can spot the start of the transit. I noticed the effect with the transit of Venus in 2012.
Parts of the Earth facing the Sun at the start of the transit (Left) and the end of the transit (Right). At the start of the transit Michigan is near the limb of the Earth at the upper left. The transit starts about 51 minutes after sunrise in norther Michigan. From Occult 4.
The only way to view the transit in white light is with a telescope with a front mounted solar filter. Using an eyepiece to project an unfiltered telescope image with an eyepiece may work, but Mercury is very small and projecting the Sun’s image in the ambient light doesn’t give a contrasty image.
To help everyone out the Grand Traverse Astronomical Society will have telescopes in two locations: The NMC Rogers Observatory and the Dune Climb at the Sleeping Bear Dunes National Lakeshore. Since the transit lasts 6 ½ hours the usual cancellation rules won’t be in effect. If it’s cloudy at the start, it could clear up later on. I’ll be stationed at the Dunes and will be there for the duration, so if we have an all day rain I’ll still be out there, hoping it’ll clear up. Check bobmoler.wordpress.com for the latest on viewing conditions there.
* Based on my article in the May 2016 edition of the Stellar Sentinel, the monthly publication of the Grand Traverse Astronomical Society.
05/06/2016 – Ephemeris – Learn about Monday’s transit of Mercury tonight
Ephemeris for Friday, May 6th. The Sun rises at 6:25. It’ll be up for 14 hours and 29 minutes, setting at 8:54. The Moon is new today, and won’t be visible.
Learn more about next Monday’s transit of Mercury across the Sun at tonight’s meeting of the Grand Traverse Astronomical Society at 8 p.m. at the Northwestern Michigan College’s Rogers Observatory, on Birmley Road, South of Traverse City. Afterward at 9 p.m., there will be another program and weather permitting there will be viewing of Jupiter, and later Mars. On Monday the Society will host transit viewing at two locations. The transit runs 6 ½ hours from 7:12 a.m. to 2:42 p.m. The Rogers Observatory will be open for that period. Also telescopes with be stationed at the Dune Climb at the Sleeping Bear Dunes National Lakeshore by yours truly to view the transit. The event is not visible to the naked eye and dangerous to even attempt it.
The program will also preview the coming opposition of Mars and closest approach since 2003 on the 30th.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
I posted these yesterday, but here they are again:
Transit visibility map with added captions to make it more readable. Credit United States Naval Observatory, The Astronomical Almanac Online.
The track of Mercury across the face of the Sun. Mercury will travel from upper left to lower right. Mercury will not be visible until it impinges upon the disk of the Sun. Credit IOTA’s program Occult4.
From IOTA’s Occult4 program
Transit of Mercury on 2016 May 9 (TT)
{'+' => next day; '-' => previous day }
Overhead at
Geocentric Event UTC P.A. Long Lat
h m s o o o
[1] Exterior Ingress 11 12 16 83.1 11 17
[2] Minimum Separation 14 57 38 -45 18
[3] Exterior Egress 18 42 23 224.4 -102 18
Minimum sepn 318.5"; Radii - Sun 950.4", Mercury 6.0"
delta T = 68.2 secs, Ephemeris = DE0
Note: These timings are geocentric. Occult4 has timings for various cities of the world. Occult4.0.2 can be downloaded here. They can vary by several minutes for different cities due to parallax.
I will post more information on the transit in an Ephemeris Extra tomorrow.
05/05/2016 – Ephemeris – Previewing Monday’s transit of Mercury
Ephemeris for Thursday, May 5th. The Sun rises at 6:26. It’ll be up for 14 hours and 26 minutes, setting at 8:53. The Moon, 1 day before new, will rise at 6:38 tomorrow morning.
Next Monday, the 9th, the tiny planet Mercury will be seen to cross that face of the Sun. Astronomers call such an event a transit. The last time a planet crossed the face of it Sun, it was Venus on June 5th, 2012, almost 4 years ago. Very few, who were alive in 2012 will be around to see the next transit of Venus in 2117. Transits of Mercury are more frequent. Mercury will cross the face of the Sun from 7:12 a.m. to 2:42 p.m. on Monday. Mercury is too small to see with eclipse filters or with the naked eye. The latter could cause blindness. Only telescopes with solar filters that fit over the front of the telescope are safe to use. Mercury will be a tiny black dot, smaller than most sunspots. Tomorrow I’ll have information about where to go to see it.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Transit visibility map with added captions to make it more readable. Credit United States Naval Observatory, The Astronomical Almanac Online! 2016
The track of Mercury across the face of the Sun. Mercury will travel from upper left to lower right. Mercury will not be visible until it impinges upon the disk of the Sun. Credit IOTA’s program Occult4.
From IOTA’s Occult4 program
Transit of Mercury on 2016 May 9 (TT)
{'+' => next day; '-' => previous day }
Overhead at
Geocentric Event UTC P.A. Long Lat
h m s o o o
[1] Exterior Ingress 11 12 16 83.1 11 17
[2] Minimum Separation 14 57 38 -45 18
[3] Exterior Egress 18 42 23 224.4 -102 18
Minimum sepn 318.5"; Radii - Sun 950.4", Mercury 6.0"
delta T = 68.2 secs, Ephemeris = DE0
Note: These timings are geocentric. Occult4 has timings for various cities of the world. Occult4.0.2 can be downloaded here. They can vary by several minutes for different cities due to parallax.
05/04/2016 – Ephemeris – There are three bright planets out by midnight
Ephemeris for Wednesday, May 4th. The Sun rises at 6:27. It’ll be up for 14 hours and 24 minutes, setting at 8:52. The Moon, 2 days before new, will rise at 5:59 tomorrow morning.
Let’s see what the bright naked eye planets are up to. Mercury is too close to the Sun to be seen. However next Monday it will be so close to the Sun that we’ll see it cross the Sun’s face. Jupiter is in the south in the early evening, and will pass due south at 9:49 p.m., and will set at 4:23 a.m. It’s below the stars of Leo this year. Binoculars can make out some of Jupiter’s moons, but a telescope is required to see all four bright moons and Jupiter’s cloud features. Mars will rise at 10:33 p.m. in the east-southeast. It’s still above its look-a-like star Antares, whose name means Rival of Mars. Mars is getting closer to the Earth now, only 52.2 million miles. 5 and a half million miles to go. Saturn will rise at 11:06 p.m. in the east-southeast. It’s just left of Mars.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter, Mars and Saturn at midnight 12:00 a.m. May 5, 2016. Created using Stellarium.
Jupiter and its moons as they might be seen through a telescope at 12 midnight May 5, 2016. It’s 40.3″ in diameter. Created using Cartes du Ciel (Sky Charts).
Mars as it might be seen in a large telescope with high power at midnight May 5, 2016. Mars apparent diameter is 16.7″. The central meridian will be 26.77 degrees. Syrtis Major is the large feature in the north near the polar cap. Created using Cartes du Ciel (Sky Charts).
Saturn and its moons at midnight May 5, 2016. The apparent diameter of the planet will be 18.2″. The rings span 42.4″, a bit larger than the apparent diameter of Jupiter. Created using Cartes du Ciel (Sky Charts).
Planets at Sunrise and Sunset of a single night starting with sunset on the right on May 4, 2016. The night ends on the left with sunrise on May 5. I’ve also plotted the Eta Aquariid meteor shower radiant. If using Firefox right-click on the image and select View Image to enlarge the image. That goes for all the large images.
05/03/2016 – Ephemeris – Halley’s Comet is back… In little bitty pieces
Ephemeris for Tuesday, May 3rd. The Sun rises at 6:29. It’ll be up for 14 hours and 21 minutes, setting at 8:50. The Moon, 3 days before new, will rise at 5:23 tomorrow morning.
There’s a meteor shower happening this week that’s a tough one for observers as far north as we are. It’s the Eta Aquariids: seeming to come from the Water Jar asterism of the constellation Aquarius the water bearer. It will reach peak on Thursday the 5th, however the radiant point rises around 3:30 a.m., and twilight starts an hour and a half later. The radiant is also low in the southeastern part of the sky. The meteors are fast-moving and many of them are bright. They are bits shed by Halley’s Comet and left in its orbit. The Earth passes close to Halley’s orbit twice a year: In late October as the particles come in from the outer solar system, and again in early May as they head back out again. We’ll see souvenirs of Halley’s Comet before it returns in 2061.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Eta Aquarid radiant at the peak of the shower. The radiant moves slowly to the east with time. Credit: Bob Moler’s LookingUp program.
This meteor shower is low for us in the Northern Hemisphere, but it will be great for those Down Under. The Moon is even cooperating this year, by getting out of the way. The active dates for the shower are April 19th to May 28th. The velocity of the meteoroids that strike the atmosphere is 66 km/s. Halley’s Comet, and thus its debris is traveling in a retrograde orbit, going the wrong way in a one way solar system, which is why the speed of the particles is so high.
04/29/2016 – Ephemeris – Let’s preview the merry skies of May
Ephemeris for Arbor Day, Friday, April 29th. The Sun rises at 6:34. It’ll be up for 14 hours and 10 minutes, setting at 8:45. The Moon, at last quarter today, will rise at 3:01 tomorrow morning.
Sunday starts the month when the promise of spring is finally fulfilled. Daylight hours in the Interlochen/Traverse City area will increase from 14 hours and 16 minutes Sunday to 15 hours 20 minutes on the 31st. The altitude, or angle, of the Sun above the southern horizon at local noon will ascend from 60 degrees Sunday to 67 degrees at month’s end. The altitude of the sun in the Straits area will be a degree lower than that but your daylight will be a few minutes longer. The big event of May will be the transit of the tiny planet Mercury across the face of the Sun on May 9th. I’ll have more on that next week. Also Mars will be in opposition from the Sun on the 22nd which due to its elliptical orbit will actually be closest to us 8 days later on the 30th at 46.779 million miles (75.284 million km).
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
May Star Chart
Star Chart for May 2016. Created using my LookingUp program. To enlarge in Firefox Right-click on image then click View Image.
The planets and stars are plotted for the 15th at 11 p.m. EDT. That is chart time. Note, Traverse City is located approximately 45 minutes behind our time meridian. (An hour 45 minutes behind our daylight saving time meridian.) To duplicate the star positions on a planisphere you may have to set it to 1:45 earlier than the current time.
Evening nautical twilight ends at 10:00 p.m. EDT on the 1st, increasing to 10:43 p.m. EDT on the 31st.
Morning nautical twilight starts at 5:20 a.m. EDT on the 1st, and decreasing to 4:38 a.m. EDT on the 31st.
Add a half hour to the chart time every week before the 15th and subtract a half hour for every week after the 15th. Before the 13th also subtract an hour for Standard Time.
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
- A leaky Big Dipper drips on Leo
- Follow the arc of the handle of the Big Dipper to the star Arcturus
- Extend the ac to a spike to point to Spica
Calendar of Planetary Events
Credit: Sky Events Calendar by Fred Espenak and Sumit Dutta (NASA’s GSFC)
To generate your own calendar go to http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html
Times are Eastern Time. Some additions made to aid clarity.
Date Time Event
May 01 Su Venus: 9.8° W
02 Mo 9:27 p.m. Moon Descending Node
04 We 2:45 p.m. Eta Aquarid Shower: ZHR = 60
06 Fr 12:14 a.m. Moon Perigee: 357800 km
06 Fr 3:30 p.m. New Moon
08 Su 4:21 a.m. Moon-Aldebaran: 0.5° S
09 Mo 7:12 a.m. Mercury transit begins
09 Mo 10:57 a.m. Mercury mid-transit
09 Mo 2:42 p.m. Mercury transit ends
09 Mo 5:54 p.m. Moon North Dec.: 18.4° N
13 Fr 1:02 p.m. First Quarter
14 Sa 3:06 a.m. Moon-Regulus: 2.5° N
15 Su 5:30 a.m. Moon-Jupiter: 2.2° N
15 Su 4:39 p.m. Moon Ascending Node
18 We 6:06 p.m. Moon Apogee: 405900 km
21 Sa 5:15 p.m. Full Moon
22 Su 7:15 a.m. Mars Opposition
22 Su 5:59 a.m. Moon-Saturn: 3.5° S
24 Tu 7:16 a.m. Moon South Dec.: 18.5° S
29 Su 8:12 a.m. Last Quarter
30 Mo 12:45 a.m. Moon Descending Node
30 Mo 5:36 p.m. Mars closest to the Earth 0.50321 AU
Jun 01 We Venus: 1.5° W
Transit of Mercury
May 9, 2016 7:12 a.m. (11:21 UT) to 2:42 p.m. (18:42 UT)
The track of Mercury across the face of the Sun. Mercury will travel from upper left to lower right. Mercury will not be visible until it impinges upon the disk of the Sun. Credit IOTA’s program Occult4.
The map showing where the transit is visible in whole or in part. If using Firefox enlarge the map by right clicking on it and select View Image.
04/28/2016 – Ephemeris – The adventures of Corvus, Apollo’s pet crow
Ephemeris for Thursday, April 28th. The Sun rises at 6:36. It’ll be up for 14 hours and 8 minutes, setting at 8:44. The Moon, 1 day before last quarter, will rise at 2:20 tomorrow morning.
The small constellation of Corvus the crow is located low in the south at 11 this evening. It’s made of 5 dim stars, but the pattern is a distinctive distorted box with two stars at the upper left marking that corner. To the right is a fainter constellation of a thick stemmed goblet called Crater. Both appear above the long constellation of Hydra the water snake who is slithering just above the southern horizon.. In Greek mythology Corvus, then white, was the god Apollo’s pet. Apollo once bid Corvus to take a cup and fetch him some water. Corvus however dallied and waited for a green fig to ripen. Corvus grabbed a snake and returned with a story as to how the snake had delayed him. The angry Apollo turned the crow and all crows to this day black.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Corvus the crow, Crater the cup and Hydra the water snake along with Jupiter and the other spring stars at 10 p.m. April 28, 2016. Created using Stellarium.
04/27/2016 – Ephemeris – Mars is closing in on its rival, but backs off for now
Ephemeris for Wednesday, April 27th. The Sun rises at 6:38. It’ll be up for 14 hours and 5 minutes, setting at 8:43. The Moon, 2 days before last quarter, will rise at 1:36 tomorrow morning.
Let’s see what the bright naked eye planets are up to. Mercury is in the west-northwest, very low to the horizon, setting at 10:12 p.m. Mercury is really fading now. Jupiter is in the southeast in the early evening, and will pass due south at 10:17 p.m., and will set at 4:51 a.m. It’s below the stars of Leo this year. Binoculars can make out some of Jupiter’s moons, but a telescope is required to see all four bright moons and Jupiter’s cloud features. Mars will rise at 11:11 p.m. in the east-southeast. It’s now almost bu not quite directly north of its look-a-like star Antares, whose name means Rival of Mars. Saturn will rise at 11:40 p.m. in the east-southeast. It’s just left of Mars. Its rings are a telescopic treat. Venus is invisibly close to the Sun now.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter and the spring stars animation. Set for 10 p.m. April 27, 2016. Created using Stellarium.
Jupiter and its moons as they might be seen in a telescope at 10 p.m., April 27, 2016. Jupiter’s apparent diameter is 41.2″ According to the Project Pluto web site the Great Red spot will cross Jupiter’s central meridian at 9:16 p.m., a half hour after sunset. If so, the position of the spot in this chart is incorrect. Created with Cartes du Ciel (Sky Charts).
Mars, Saturn and the Moon at 5:30 a.m. April 28, 2016. Created using Stellarium.
Mars as it might be seen in a large telescope with high power at 5:30 a.m., April 28 2016. Mars apparent diameter is 15.7″. The central meridian will be 169.90 degrees. Created using Cartes du Ciel (Sky Charts).
Saturn and its moons at 5:30 a.m., April 28, 2016. The apparent diameter of the planet will be 18.1″. The rings span 42.1″, a bit larger than the apparent diameter of Jupiter. Created using Cartes du Ciel (Sky Charts).
The Moon as it might appear in binoculars at 5:30 a.m. on April 28, 2016. Created using Stellarium.
The retrograde tracks of Mars and Saturn as we pass both planets this year. The tracks start on February 14, 2016 and run to September 13, 2016 plotted at 4 day intervals and labeled every 20 days. I noticed when producing the Mars, Saturn & Moon plot above that Mars was not due north of Antares on the 27th. Mars actually became stationary and started it’s retrograde loop a few days ago before it got that far. However when Mars doubles back, it will have a much closer pass of Antares on August 27th. Saturn’s plots are so close together that they appear as a fat line. Created using Cartes du Ciel (Sky Charts).
Retrograde motion of the planets are caused when the Earth is either passing a superior planet (Mars, Jupiter, Saturn, etc.), or when being passed by an inferior planet (Venus and Mercury). It was a big problem with the old Earth center solar system, before Copernicus and Kepler.
Planets at sunrise and sunset of a single night starting with sunset on the right on April 27, 2016. The night ends on the left with sunrise on April 28. If you are using Firefox right-click on the image and select View Image to enlarge the image. That goes for all the large images.
04/26/2016 – Ephemeris – Arcturus, just passing through
Ephemeris for Tuesday, April 26th. The Sun rises at 6:39. It’ll be up for 14 hours and 2 minutes, setting at 8:42. The Moon, 3 days before last quarter, will rise at 12:48 tomorrow morning.
Arcturus is an orange-colored giant star, 37 light years away. We see it high in the east and pointed to by following the arc of the handle of the Big Dipper. Arcturus is a rapidly moving star. It’s velocity is about 76 miles per second (122 km/s). It’s almost at its nearest to the Sun now. In the next 2,000 years it will move about one degree, twice the width of the Moon toward Spica. Arcturus may be part of a dwarf galaxy being assimilated by the Milky Way which may account to its odd motion. Arcturus is thought to be close to 8% more massive than the Sun and about 6 to 8 ½ billion years old. It has entered its red giant stage after running out of hydrogen in its core. It may be a glimpse of what the sun will look like in 5 billion years.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The constellation Bootes and the 4th brightest star in the night sky. The thin line extending to the right from Arcturus is the distance it will travel in the next 2,000 years. That line is nearly one degree ling, or 2 Mon diameters. Created using Cartes du Ciel (Sky Charts)
04/25/2016 – Ephemeris – Arcas and Callisto
Ephemeris for Monday, April 25th. The Sun rises at 6:41. It’ll be up for 13 hours and 59 minutes, setting at 8:40. The Moon, 3 days past full, will rise at 11:56 this evening.
Appearing mid way up the sky in the east at 10 p.m. is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom of the kite, pointed to by the arc of the handle of the Big Dipper, above it. In one story Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief of the Greek gods. Zeus’ wife Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into an ugly bear. Arcas, unaware of the events surrounding his mother’s disappearance was about to kill the bear when Zeus intervened and placed them both in the sky to save her. To this day Boötes continues to chase the great bear Ursa Major around the sky each night.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.
Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center
