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05/06/2019 – Ephemeris – The Eta Aquariid meteor shower

May 6, 2019 Comments off

Ephemeris for Monday, May 6th. Today the Sun will be up for 14 hours and 27 minutes, setting at 8:53, and it will rise tomorrow at 6:24. The Moon, 2 days past new, will set at 10:52 this evening.

The Earth is now passing through a stream of bits of rock that were shed from Halley’s Comet on its many previous passes of the inner solar system. The Earth gets to pass through this stream twice, Once in late October as the stream passes the Earth’s orbit heading in, and in early May as the stream is departing. The peak of this meteor shower, the Eta Aquariids, lasts several days. But since the meteoroids are coming from nearer the direction of the Sun, there is only a short period when these meteors are visible. Actually only an hour between 3:30 a.m. and 4:30 a.m. or a little bit later in the Grand Traverse region as twilight begins to interfere with the display. The radiant, from where the meteors will seem to come will stay low in the east-southeast, but they will be seen all over the sky.  The farther south one is on the earth the longer each morning the meteors will be visible.  We’re at a disadvantage being 45º north latitude.

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

Addendum

Eta Aquarid Radiant

The sky at 4 a.m. tomorrow looking eastward at the Eta Aquariid radiant. Click on the image to enlarge. Created using Stellarium.

 

05/06/2019 – Ephemeris Extra – The Eta Aquariids – Halley’s Comet never really left

May 5, 2019 Comments off

In 1986 Halley’s Comet swam through our skies for the 28th time since the Chinese first recorded it in 240 BCE. It was not especially impressive, considering the week when my family met a group of Leelanau School students in the Florida Keys the week in April 1986 to view and photograph the comet at it’s closest to the Earth of 44 million miles. It turned out that that week the comet lost its tail, probably due to a coronal mass ejection from the Sun. Halley’s Comet was much more impressive a month later. I’ve seen more impressive comets before and since.

Comet Halley's path thru the inner solar sstem

Comet Halley’s path through the inner solar system in 1985-86. Created using my LookingUp program.

Halley’s Comet has been swinging around the Sun countless times before the Chinese first recorded it. The illustration above shows the last time the comet entered the inner solar system in 1986. The comet’s path is from upper right to lower left. When the comet passes within about 3 astronomical units of the Sun, that is 3 times the Earth’s distance from the Sun, the ices in the comet begin to sublimate, escaping from the comet’s nucleus which liberates dust and larger solid material. The gasses and dust form the comet’s ion and dust tails. The larger material, gravel sized bits, end up in and around the comet’s orbit, and over time are spread out around and near the comet’s orbit. Halley’s orbit crosses the Earth’s orbit twice, inbound and outbound. In both cases these crossings are close enough to the plane of the Earth’s orbit to produce meteor showers.

On the inboard leg of the orbit it produces the Orionid meteor shower that peaks on October 22nd. A meteor shower is generally named for the point in the sky they seem to come from, be it a constellation or star. The point, called the radiant, moves during the days or weeks the shower is visible. The Orionids are named for the constellation Orion. The radiant is near his upraised arm.

The center of the outbound meteoroid stream crosses the Earth’s orbit where the Earth is on May 6th. Though they have a broad peak of about 5 days. This meteor shower is visible from April 19th to May28th. During that period the radiant points drifts quite a bit to the east. There are several meteor shower radiants in Aquarius, so they are named for the nearest star at peak.

Motion of Eta Aquariid Radiant

Motion of the Eta Aquariid radiant from April 20 to May 25. The triangle with the star near the center near May 05 is the asterism the Water Jar, a part of Aquarius. Eta Aquarii is the triangle star to the left. Source: PDF version of the International Meteor Organization 2019 Meteor Shower Calendar: https://www.imo.net/resources/calendar/

Though the Moon is new for this shower, the meteoroids are coming from near the direction of the Sun, so there is only an hour where the Eta Aquariids are best seen. For Northern Michigan the radiant rises at 3:30 a.m. on May 6th. Astronomical twilight begins at 4:30 a.m. when the sky begins to brighten. This meteor shower is best seen from the southern hemisphere.

01/03/2019 – Ephemeris – The Quadrantid meteor shower will reach its peak this evening

January 3, 2019 Comments off

Ephemeris for Thursday, January 3rd. The Sun will rise at 8:20. It’ll be up for 8 hours and 54 minutes, setting at 5:14. The Moon, 2 days before new, will rise at 7:01 tomorrow morning.

Of the three most active meteor showers, year after year, the Quadrantids of January, Perseids of August, and Geminids of December, only the Quadrantids are not affected by a bright Moon this year. The Quadrantids, which will reach peak at 9:20 this evening have their radiant about due north at that time, only a few degrees above the horizon. The peak is rather narrow, 4 hours to achieve at least half maximum, which is 120 meteors an hour if the radiant was overhead. The radiant, from which the meteors will come from is very low, so will be the numbers. However a low radiant means that the meteor streaks all over the sky will be longer as the meteoroids strike the atmosphere overhead at a shallow angle.

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

Addendum

Quadrantid radiant at peak

The location of the Quadrantid radiant, off the handle of the Big Dipper, at 9:20 p.m. January 3, 2019 for the peak of the meteor shower. Click on the image to enlarge. Created using Stellarium.

 

 

12/13/2018 – Ephemeris – The Geminid meteors will reach their peak numbers overnight

December 13, 2018 Comments off

Ephemeris for Thursday, December 13th. The Sun will rise at 8:11. It’ll be up for 8 hours and 50 minutes, setting at 5:02. The Moon, 2 days before first quarter, will set at 11:05 this evening.

Tonight through the morning hours we will have the chance to see the peak of the Geminid meteor shower. The meteors will be most numerous tomorrow morning. This shower is currently besting the Perseid meteor shower of August with a predicted 120 meteors per hour at the peak. The problems for us in viewing this fabulous shower are the cold temperatures and usually cloudy skies. However the Moon will be a problem until it sets after 11 p.m. The source of the Geminids was discovered in 1983. It is a burnt out comet with the asteroid designation (3200) Phaethon which swoops down to only 13 million miles of the Sun, but last year passed only 6.4 million miles from Earth. The Geminids were first seen in 1862.

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

Addendum

Geminid meteor shower radiant

The area of the Geminid meteor shower radiant near the star Castor at 4 a.m. December 14, 2018. There are other very minor radiants that provide only a handful of meteors per hour. The Geminids will provide up to 120 meteors per hour. Created using Stellarium.

11/19/2018 – Ephemeris – The Leonids’ comet 55P/Tempel-Tuttle

November 19, 2018 Comments off

Ephemeris for Monday, November 19th. The Sun will rise at 7:45. It’ll be up for 9 hours and 25 minutes, setting at 5:10. The Moon, half way from first quarter to full, will set at 4:29 tomorrow morning.

We have another day in this year’s extended Leonid meteor peak. In past years, usually every 33 years the Leonid meteors have a super peak, called a meteor storm, where thousands of meteors streak through the skies. These appear for a brief period over a rather small geographic area. In 1966 it occurred principally over the Rocky Mountains. The comet responsible is Comet Tempel Tuttle, independently discovered by two astronomers Tempel and Tuttle in 1865 & 1866. The comet had a 33 year orbit of the Sun, and its orbit crosses very close to the Earth’s orbit. Comets are notorious litter bugs, shedding gas, dust and pebble sized debris as they come close to the warming rays of the Sun.

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

Addendum

Entire orbit of Comet Tempel-Tuttle
Entire orbit of Comet Tempel-Tuttle projected on the plane of the Earth’s orbit.. Credit C2A Planetarium program, copied from TransientSky.com
The comet's orbit and debris stream
The comet’s orbit and debris stream where it intersects the Earth’s orbit. Credit Katie Peek, Popular Science.

11/16/2018 – Ephemeris – The Leonid meteor shower will have several peaks in the next few days

November 16, 2018 Comments off

Ephemeris for Friday, November 16th. The Sun will rise at 7:41. It’ll be up for 9 hours and 32 minutes, setting at 5:13. The Moon, 1 day past first quarter, will set at 1:19 tomorrow morning.

We are coming into an extended period where the Leonid meteor shower will be at its peak, or rather there is a chance of up to maybe four peaks as the Earth passes through the debris left by Comet Tempel-Tuttle on past trips through the inner solar system. We are having a pretty bright Moon now, but the best displays of the meteors are going to be occurring in the early morning hours after the Moon sets. The meteors will appear to come from the top of a backward question mark that is the head of the constellation Leo the lion. They will be seen all over the sky, but can be traced back to that point, if it’s a Leonid meteor. The Leonids are most numerous about every 33 years, which is about 15 years from now. Otherwise we get about 15 meteors an hour at peak.

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

Addendum

Leonid radiant
The constellation of Leo the lion and the Leonid radiant for about 5 a.m.  Click on image to enlarge.  Created using Stellarium.

11/06/2018 – Ephemeris – The Taurid meteor showers

November 6, 2018 Comments off

Ephemeris for Election Day, Tuesday, November 6th. The Sun will rise at 7:27. It’ll be up for 9 hours and 57 minutes, setting at 5:24. The Moon, 1 day before new, will rise at 7:09 tomorrow morning.

We are in the midst of two showers of meteors that seen to come from the constellation of Taurus the bull. These are the Southern and Northern Taurids respectively. They only produce a handful of meteors per hour, but there seems to be some discrepancy in their peak dates. The International Meteor Organization has the Southern group peak October 10th. Other sources have it peak November 5th. The Northern group peaks on the 10th or 12th of November depending on the source. Anyway these are bits shed by Comet 2P/Encke, which has only a 3 year orbit of the Sun. Encke’s orbit also comes close to the Earth’s orbit where the Earth is at the end of June. I’ve always wondered if it was a piece of Encke’s nucleus that hit Siberia on June 30, 1908?

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

Addendum

Taurid Radiants at midnight in early November
The Southern and Northern Taurid meteor shower radiants at around midnight in early November. Created using Stellarium.

The radiants are not as nearly defined as shown here