The Perseid meteors are coming! Many consider the Perseids to be the best shower of the year. Mild summer weather and occasional hourly rates exceeding 100 make observing the Perseids a delight. Perseids are bright and fast. Meteors are tiny bits of dust and cosmic debris. Most are the size of grains of sand.

We encounter the dust trail of comet Swift Tuttle each year from late July through mid August. It is these flecks of dust and grains of sand which are responsible for the Perseid shower. The debris from comet Swift Tuttle is a dust trial left on visits to the inner solar system in 441, 1479 and 1862. This will be a good year for the Perseids because the Moon will set shortly after sunset. Lunar glare will not be a concern. The Moon was new on Tuesday, August 10.

The shower will peak on Wednesday and Thursday nights. The best to watch is Thursday night between 10pm and dawn local time Friday morning. One prediction expects a spike in activity at 0045 UT (8:45 pm EDT) Thursday night Friday morning. This spike favors observers in Europe and Scandinavia. Another spike is expected at 1202 UT Friday morning (8:02 am EDT). This spike will favor observers in the Pacific and Asia. See predictions from Mikhail Maslov here. These predictions call for an overall peak in activity between 18 UT 12 August and 7 UT 13 August.

Here is the forecast from Robert Lunsford of the International Meteor Organization:

The Perseids (PER) are active from a radiant located at 02:03 (031) +55. This position lies in western Perseus, twelve degrees north of the famous second magnitude double star Almach (Gamma Andromedae). The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. Current rates would be two to three per hour at best, as seen from the northern hemisphere. Activity from this source is not visible south of 40 degrees south latitude. With an entry velocity of 61 km/sec., most activity from this radiant would be swift

You won’t need binoculars or a telescope. Find the darkest spot available and make yourself comfortable on a blanket or lawn chair. Watch the darkest part of the sky. Meteor activity is generally greatest in the hours just before dawn because observers in that part of the world are moving through space on Earth’s “front bumper”. Over the past few nights I’ve popped outside between 3 and 6am for a few minutes. Saturday morning I saw two Perseids in 5 minutes.

This shower is called the Perseids because the meteors appear to originate from a radiant in the northern part of the constellation Perseus which rises to the northeast around 12:30 am at this time of year. See the chart. If you’d care to join me and members of the LAS contact me through the link above.

A European group of astronomy enthusiasts will be Tweeting their meteor counts here

IMO Twitter

Other links:

MeteorWatch

Observing and timing a lunar eclipse is a very subjective exercise. According to Westfall “the exact times you observe the four “eclipse contacts” depend on your eyesight, judgement, the characteristics of the umbra’s fuzzy edge and local sky conditions”. The historical application of such observations is at the heart of this exercise. In past centuries, naked eye timings of lunar eclipse contacts were one of the few ways that navigators and explorers could determine their longitude on earth.

In his Astronomical Calendar, Guy Ottewell presents an excellent treatise on observing and estimating the brightness or darkness of a lunar eclipse. Quoting Ottewell: “The penumbra is very faint. This is not surprising: from all parts of it, at least some part of the brilliant Sun would be visible, so it is essentially like early-morning daylight on the Earth. The outer part of the penumbra is imperceptible to the eye, so the beginning of penumbral eclipse is an academic event. The inner half or more of the penumbra is perceptible as a slight graying.”

For our eclipse timing exercise the first contact of the umbra is the first event timing of interest. Ottewell continues: “The umbra, by contrast, begins with an edge that is almost hard, and noticeably part of a circle (thus proving to the ancient Greeks that the Earth is a globe). Though the umbra is the “total shadow,” from within which no part of the Sun can be seen directly, it is generally not plain black, because sunlight is refracted into it through the atmosphere all around the Earth around the continuous ring of the sunrise-and-sunset line. The amount by which the light is reduced and reddened depends on clouds, volcanic ash, pollution, etc, all around this geographical band; so it varies from eclipse to eclipse and from part to part of the Moon. The standard way to record and compare these variations is to use this scale, proposed by Andre Danjon, and intended to apply if possible to the middle of the eclipse. L stands for luminosity”.

L=0: Very dark eclipse, Moon almost invisible, especially in mid-totality.

L=1: dark eclipse, gray or brownish coloration, details distinguishable only with difficulty.

L=2: deep red or rust colored eclipse, umbra usually having a very dark center and relatively bright outer rim.

L=3: brick-red eclipse, umbra usually having a yellow or bright gray rim.

L=4: strikingly bright copper-red or orange eclipse, with very bright bluish tint where umbra and penumbra meet.

Fractional estimates can be used, such as 1.3; and different parts of the Moon may have different values. Observers often make reports such as “Probably 2, but the Mare Crisium was invisble and there was a very bright patch along the southern edge”

Listen to our interview with Dr. John Westfall and learn how to time the four eclipse “contacts” and participate in the visual timing experiment. Click on the link above.

To learn more about determining one’s position on Earth read “Precision Geolocation Using Lunar Occultation”, Ingalls, Scientific American, January 1955. This article was re-published in 2001 in “Scientific American: The Amateur Astronomer”, by Shawn Carlson. Publisher: John Wiley & Sons. ISBN: 0-471-38282-5

Comet 8P/Tuttle is expected to peak in visual magnitude 6.0 in late December and early January. The comet will reach Perigee (nearest Earth) on New Year’s Day and Perihelion (nearest the Sun) on 26 January. This is expected to be the best sighting and closest pass since Horace Tuttle re-discovered the comet in 1858. The path of this comet will take it south through Andromeda, Pisces and Cetus. It will glide by M33, the Triangulum galaxy, on 30 December. Since 8P/Tuttle will be only 25 million miles from Earth on 1 January it will sweep southward about 4 degrees per day.

While we’re discussing comets, be alert to the possibility of a second brightening and spike in the visual magnitude of Comet 17P/Holmes. Holmes had such an outburst during it’s apparition of 1892-93. This comet is currently drifting through eastern Perseus and will pass within 10 arcminutes of the bright variable star Algol on the night of 22 January.

Will a recently discovered asteroid impact Mars? The asteroid, which has been designated 2007 WD 5, was discovered in early November. Astronomers at NASA’s Jet Propulsion Laboratory estimate this asteroid to be 150 feet across and currently predict a 1-in-25 (4%) chance that it will impact Mars early on the morning of 30 January, 2008. Likely the asteroid will miss the red planet by about 15,000 miles.

The Planets in January

Mercury will make it’s first appearance of 2008 in the evening skies of late January. Watch for Mercury about 30 minutes after sunset 10 degrees above the west-southwest horizon from January 19th-26th. The tiny planet reaches maximum eastern elongation 23 January.

Venus pre-dawn show continues, but it appears a bit lower in the sky each successive morning. January 4-6th the waning crescent Moon dances through Scorpius past Antares and Venus. Each morning Venus and Jupiter will draw “closer” to each other until the two brightest planets reach their nearest conjunction, less than a degree apart, on 1 February.

Mars continues to be visible nearly all night long being just past opposition and it’s nearest approach to Earth in mid-December. We’re moving away from the red planet now but observing will still be very good through the month of January. Look for it this month retrograde through Gemini and Taurus.

Jupiter starts January too low to be observable before dawn but will climb to meet Venus for a spectacular conjunction by month’s end. Look for it above the southeastern horizon in Scorpius before dawn.

Saturn is rising around 9pm as the new year begins. Best time to observe the ringed planet this month will be after midnight in constellation Leo.

Neptune will be difficult to see in the evening twilight this month. Catch Uranus quickly after sunset low in the southwest in Aquarius.

Earth reaches perihelion, closest to the Sun for 2008, at 23:50 UT (6:50pm EST) January 2nd

The latest sunrise of the year for the northern hemisphere occurs the morning of 5 January

New Moon 8 January First Quarter Moon 15 January

Full Moon 22 January Last Quarter Moon 30 January

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