# Portal:Astronomy/Events/May 2005

May 2005 | |
---|---|

5 May |
Eta Aquariids meteor shower: up to 60 meteors per hour |

8 May, 08:46 |
New moon |

15 May, 11:01 |
Mars lies only 1°06' from Uranus |

23 May, 20:19 |
Full moon |

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< Portal:Astronomy | Events

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May 2005 | |
---|---|

5 May |
Eta Aquariids meteor shower: up to 60 meteors per hour |

8 May, 08:46 |
New moon |

15 May, 11:01 |
Mars lies only 1°06' from Uranus |

23 May, 20:19 |
Full moon |

RELATED RESEARCH TOPICS

1. Meteor shower – A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of debris called meteoroids entering Earths atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate, intense or unusual meteor showers are known as meteor outbursts and meteor storms, which may produce greater than 1000 meteors an hour. The Meteor Data Centre lists about 600 suspected meteor showers of which about 100 are well established, the first great storm in modern times was the Leonids of November 1833. American Denison Olmsted explained the event most accurately, after spending the last weeks of 1833 collecting information he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, and January 1836. Work continued, however, coming to understand the nature of showers though the occurrences of storms perplexed researchers. In the 1890s, Irish astronomer George Johnstone Stoney and British astronomer Arthur Matthew Weld Downing, were the first to attempt to calculate the position of the dust at Earths orbit. They studied the dust ejected in 1866 by comet 55P/Tempel-Tuttle in advance of the anticipated Leonid shower return of 1898 and 1899, Meteor storms were anticipated, but the final calculations showed that most of the dust would be far inside of Earths orbit. The same results were independently arrived at by Adolf Berberich of the Königliches Astronomisches Rechen Institut in Berlin, although the absence of meteor storms that season confirmed the calculations, the advance of much better computing tools was needed to arrive at reliable predictions. In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of showers for the Leonids. A graph from it was adapted and re-published in Sky and Telescope and it showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. In 1985, E. D. Kondrateva and E. A. Reznikov of Kazan State University first correctly identified the years when dust was released which was responsible for several past Leonid meteor storms, in 1995, Peter Jenniskens predicted the 1995 Alpha Monocerotids outburst from dust trails. In anticipation of the 1999 Leonid storm, Robert H. McNaught, David Asher, in 2006 Jenniskens has published predictions for future dust trail encounters covering the next 50 years. Jérémie Vaubaillon continues to update predictions based on each year for the Institut de Mécanique Céleste et de Calcul des Éphémérides. Because meteor shower particles are all traveling in parallel paths, and at the same velocity and this radiant point is caused by the effect of perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks. Meteor showers are almost always named after the constellation from which the appear to originate. This fixed point slowly moves across the sky during the due to the Earth turning on its axis. The radiant also moves slightly from night to night against the stars due to the Earth moving in its orbit around the sun

2. Zenithal hourly rate – In astronomy, the Zenithal Hourly Rate of a meteor shower is the number of meteors a single observer would see in an hour of peak activity. The rate that can effectively be seen is nearly always lower and decreases the closer the radiant is to the horizon. The formula to calculate the ZHR is, Z H R = H R ¯ ⋅ F ⋅ r 6.5 − l m sin where H R ¯ = N T e f f represents the rate of the observer. N is the number of meteors observed, and Teff is the observation time of the observer. Example, If the observer detected 12 meteors in 15 minutes, F =11 − k This represents the field of view correction factor, where k is the percentage of the observers field of view which is obstructed. Example, If 20% of the field of view were covered by clouds. The observer should have seen 25% more meteors, therefore we multiply by F =1.25, R6.5 − l m This represents the limiting magnitude correction factor. For every change of 1 magnitude in the magnitude of the observer. Therefore we must take this into account. Example, If r is 2, and the limiting magnitude is 5.5, we will have to multiply their hourly rate by 2. Sin This represents the factor for altitude of the radiant above the horizon. The number of meteors seen by an observer changes as the sine of the radiant height in radians, list of meteor showers North American Meteor Network

3. New moon – In astronomy, new moon is the first phase of the Moon, when it orbits not seen from the Earth, the moment when the Moon and the Sun have the same ecliptical longitude. The Moon is not visible at this time except when it is seen in silhouette during a solar eclipse when it is illuminated by earthshine, see the article on phases of the Moon for further details. A lunation or synodic month is the time from one new moon to the next. In the J2000.0 epoch, the length of a lunation is 29.530588 days. However, the length of any one month can vary from 29.26 to 29.80 days due to the perturbing effects of the Suns gravity on the Moons eccentric orbit. In a lunar calendar, each corresponds to a lunation. Each lunar cycle can be assigned a unique Lunation Number to identify it, the length of a lunation is about 29.53 days. Its precise duration is linked to many phenomena in nature, such as the variation between spring and neap tides, an approximate formula to compute the mean moments of new moon for successive months is, d =5.597661 +29. For all new moons between 1601 and 2401, the difference is 0.592 days = 14h13m in either direction. The duration of a lunation varies in this period between 29.272 and 29.833 days, i. e. −0. 259d = 6h12m shorter, or +0. 302d = 7h15m longer than average. This range is smaller than the difference between mean and true conjunction, because during one lunation the periodic terms cannot all change to their maximum opposite value, see the article on the full moon cycle for a fairly simple method to compute the moment of new moon more accurately. These are now outdated, Chapront et al. published improved parameters, quadratic term, In ELP2000–85, D has a quadratic term of −5. 8681T2, expressed in lunations N, this yields a correction of +87. 403×10–12N2 days to the time of conjunction. The term includes a contribution of 0. 5×. The most current estimate from Lunar Laser Ranging for the acceleration is, therefore, the new quadratic term of D is = -6. 8498T2. Indeed, the polynomial provided by Chapront et alii provides the same value and this translates to a correction of +14. 622×10−12N2 days to the time of conjunction, the quadratic term now is, +102. 026×10−12N2 days. For UT, analysis of historical observations shows that ΔT has an increase of +31 s/cy2. Converted to days and lunations, the correction from ET to UT becomes, the theoretical tidal contribution to ΔT is about +42 s/cy2 the smaller observed value is thought to be mostly due to changes in the shape of the Earth. Because the discrepancy is not fully explained, uncertainty of our prediction of UT may be as large as the difference between these values,11 s/cy2