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|Eclipses | Comets | Meteor Showers | Near-Earth Objects, Asteroids & Comets | Planets |Man-made Objects | Solar Flares & Sun spots | Geomagnetic Storms | Galaxy Collision | Glossary
See Calendars at:
Astronomical Events - Discover Eclipses, Meteor Showers, ... (space.about.com) | Central Coast Astronomical Society - CCAS,
Solar - Moon passes between the earth and the sun.
Lunar - Earth passes between the sun and moon.
Upcomming total eclipses:
A relatively small object which is composed of dirt and ices. Comets are characterised by dust and gas tails pointing away from the sun. The ones that we have seen have large elipitical orbits extending to the outer solar system and beyond. They range in size from 1/2 to 5 mi. Astronomers estimate there are 100 billion of these objects in the Oort Cloud beyond Pluto.
A comet's apparent brightness as seen from Earth depends on both its distance from the Sun and its distance from Earth. A comet may seem brighter on one appearance than another because of the position of the earth in its orbit brings it closer to the comet. A comet also grows brighter as it comes closer to Sun and its water and ice vaporizes ever more vigorously.
(2) Chiron is categorized as both an Asteroid and Comet.
(3) Calculations indicate Hyakutake original period was close to 10,000 yrs. and the future period will be about 18,000 years due to perturbations by planets during the present passage.
Fragments of Comet Shoemaker-Levy 9 collided with Jupiter between July 16 and July 22, 1994.
Periodic or short-period comets: Any comet with an orbital period of less than 200 years. These comets are indicated by a "P/" before the names. For example, P/Halley is Halley's comet or more properly known as periodic Comet Halley.
See: Gary W. Kronk's cometography.com
An average of 7 sporadic (not associated with a shower) meteors per hour can be seen from one place on a normal clear night. 200 million visible meteors reach the earth each day. (Source: The Astronomical Companion, by Guy Ottewell)
A meteor shower is caused by a trail of particles left by a comet as it revolves around the Sun or a broken up asteroid. These particles can remain suspended in space for decades. Meteor showers produce 50 or more visible meteors per hour. The Perseids were one of the most exciting meteor showers during the 1990s, with outbursts of 400+ meteors per hour in 1991 and 1992. Rates from this peak decreased to 100-120 by the late 1990s, and since 2000, it has failed to appear.
Most meteors from a common meteor shower are parallel to one another. But they appear to emerge from the same point in the sky called the "radiant" and they travel in all directions from this point.
The friction between the meteor and earth's atmosphere, generates enough heat (up to 3,000 degrees Fahrenheit, or 1649 degrees Celsius) to raise the meteoroid's surface to its boiling point, so the meteoroid is vaporized, layer by layer, creating a vapor of sodium, iron and magnesium atoms. In subsequent collisions, electrons are knocked into orbits at larger mean distances from the nucleus of the atoms. When the electrons fall back to their rest positions, light is emitted. This is the same process as in gas discharge lamps.
1. ZHR for Leonids in 1998 just after the Tempel-Tuttle comet passed was several hundred.
2. Earth encountered this 2000-year-old dust in 1935, 1986, 1994 and 2007.
It was only recently speculated that comet 2003 EH1 was responsible for the Quadrantids meteor shower. The orbit of this comet seems to vary over time due to encounters with Jupiter or an asteroid.
2007 Meteor Shower Calendar at IMO
Sky Watch, The International Meteor Organization - IMO,
Impact Events and Explosions :
Most extraterrestrial objects like meteoroids burn up in the atmosphere creating shooting stars or meteor showers.
However larger astroids and comets which enter the earth will create large explosions in the atmosphere (5-20 miles high) or hit the earth. The energy released by an impactor depends on diameter, density, velocity, and angle.
The meteor which exploded over Chelyabinsk, Russia in 2013 created a blast equivalent to about 600 kilotons of TNT.
(30 times the energy than the atomic bomb that destroyed Hiroshima in 1945 which exploded with an energy impact of 16 kilotons of TNT.)
It was the largest airburst since the 1908 Tunguska event in Siberia (10-15 megatones).
A low angle of entry will probably result in an explosion in the atmosphere vaporizing most of the astroid and breaking the rest into small particles. They found a coffee-table-size chunk of the Chelyabinsk meteorite weighing about 1,430 pounds in a lake.
Stony asteroids with a diameter of 4 meters (13 ft) impact Earth approximately once per year. Asteroids with a 1 km (0.62 mi) diameter strike Earth every 500,000 years on average.
The most famous meteor strike is the one that theoretically caused the extinction of the dinosaurs 65 million years ago. Many believe it would have been a six-mile wide asteroid which created the 110 mile wild Chicxulub Crater in Yucatan, Mexico. Skeptics say the crater predates the extinction of dinosaurs by 300,000 or so years.
In 2014, scientists reported finding evidence of the largest impact event to date in South Africa. They estimated the impact occurred about 3.26 billion years ago and that the impactor was approximately 23-36 miles wide. The crater from this event, if it still exists, has not yet been found.
Some memorable impacts:
Chelyabinsk fireball shows meteor threat bigger than originally thought, scientists say | National Post
The giant impact hypothesis states that the Moon was formed out of the debris left over from an indirect collision between the Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago.
These asteroids hit the earth at about 12 miles per second (about 60 times the speed of sound or 10 times the muzzle velocity of a rifle bullet).
There are 30-40,000 of these giant rocks floating in their own individual orbits between Mars and Jupiter. There are several hundred known asteroids that regularly cross the orbit of the Earth. They are known as Earth-crossing asteroids. They range in size from 1 to 600 miles (1/4 the size of our moon). Smaller objects are called meteoroids.
(3) Not to be confused with a moon of Jupiter with the same name.
See: Potentially Hazardous Asteroids (PHAs) at the Asteroids page.
Geomagnetic or Solar Storms
A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs from the solar wind
The largest storms that result from these conditions are associated with solar coronal mass ejections (CMEs) where a billion tons or so of plasma from the sun, with its embedded magnetic field, arrives at Earth. CMEs typically take several days to arrive at Earth, but have been observed, for some of the most intense storms, to arrive in as short as 18 hours.
In 1997, such a storm shut down an AT&T Telstar 401 satellite that provided television broadcasts. The following year another storm disrupted a Galaxy IV satellite that supported automated cash machines and airline tracking systems.
Such storms are also known to affect mobile phone operations and may disrupt wireless internet services.
Recent Space Weather events: (Alerts, Watches and Warnings | NOAA) 2015 May 6, - ALERT: Geomagnetic K-index of 5 2015 May 6, - WARNING: Geomagnetic K-index of 5 expected 2015 May 6, - SUMMARY: Geomagnetic Sudden Impulse 2015 May 5, - SUMMARY: X-ray Event exceeded X1 2015 May 5 - ALERT: Type II Radio Emission 2015 Apr 30 - WARNING: Geomagnetic K-index of 4 expected 2015 Apr 24 - ALERT: Electron 2MeV Integral Flux exceeded 1000pfu 2015 Apr 23 - ALERT: Type II Radio Emission 2015 Apr 23 - ALERT: Geomagnetic K-index of 4 2015 Apr 23 - ALERT: Geomagnetic K-index of 4 expected 2015 Apr 21 - WARNING: Geomagnetic K-index of 5 expected 2015 Apr 19 - WATCH: Geomagnetic Storm Category G1 Predicted 2015 Apr 16 - WATCH: Geomagnetic Storm Category G2 Predicted 2015 Apr 16 - ALERT: Geomagnetic K-index of 6 2015 Apr 16 - WARNING: Geomagnetic K-Index of 6 expected 2015 Apr 16 - ALERT: Electron 2MeV Integral Flux exceeded 1000pfu 2015 Apr 15 - WARNING: Geomagnetic K-Index of 6 expected 2015 Apr 14 - WARNING: Geomagnetic K-index of 5 expected 2015 Apr 12 - ALERT: Type II Radio Emission 2015 Apr 12 - SUMMARY: 10cm Radio Burst 2015 Apr 11 - WARNING: Geomagnetic K-index of 5 expected 2015 Apr 10 - WATCH: Geomagnetic Storm Category G1 Predicted 2015 Apr 10 - WARNING: Geomagnetic K-Index of 6 expected 2015 Apr 7 - WATCH: Geomagnetic Storm Category G1 Predicted 2015 Apr 7 - ALERT: Type IV Radio EmissionCauses:
Solar flares are associated with Coronal Mass Ejections (CMEs) which can ultimately lead to geomagnetic storms.
Coronal Mass Ejections (CME) CMEs, an expanding bubble of charged particles, travel outward from the Sun typically at speeds of about 300 kilometers per second, but can be as slow as 100 kilometers per second or faster than 3000 kilometers per second. The fastest CMEs erupt from large sunspot active regions, powered by the strongest magnetic field concentrations on the Sun. These fast CMEs can reach Earth in as little as 14-17 hours.
Historical records of solar events suggest that a reasonable range for the average return period for an
extreme geomagnetic storm like the Carrington event in 1859, is 100-500 years.
A Carrington-class flare today would be devistating.
A huge solar flare on August 4, 1972, knocked out long-distance telephone communication across Illinois. That event, in fact, caused AT&T to redesign its power system for transatlantic cables.
In 1989, a geomagnetic storm energized ground induced currents which disrupted electric power distribution throughout most of the province of Quebec and caused aurorae as far south as Texas.
A Carrington-class flare today would be devistating.
A solar flare is an explosion on the Sun that happens when energy stored in twisted magnetic fields (usually above sunspots) is suddenly released. Flares produce a burst of radiation across the electromagnetic spectrum, from radio waves to x-rays and gamma-rays.
Follow activity with your mobile phone:
Five planets (The 3 inner planets, Mercury, Venus and Mars, plus the first two outer planets, the gas giants, Saturn and Jupiter) are visible with the naked-eye.
What many people call the morning or evening star is actually a planet, usually Venus but sometimes Jupiter, Saturn, or Mars. When one of them appears close to the Sun as viewed from Earth, sunset or sunrise watchers are treated to starlike brilliance.
Because Mars orbit is slightly eliptical it may be closer some years. On August 27, 2003 Mars was closer to the earth than at any time in the past 60-70,000 years. See www.spaceweather.com/delights/mars2003_View.html
On June 8, 2004 venus' orbit took it between the earth and sun.
Man-made Objects (Satellites, Space Shuttle, Space Station)
See Also: The Astronomical Companion, by Guy Ottewell
The University of Leicester Astronomy Society
Solar Flares & Sun spots
Universal Time (UT) Table (UT is the time in the Greenwich time zone)
Near Earth Objects
Fundamentals of Meteor Science (Journal of the IMO)
Homepage | NOAA / NWS Space Weather Prediction Center
Coronal Mass Ejections | NOAA / NWS Space Weather Prediction Center
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