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, ... ( | Central Coast Astronomical Society - CCAS,
Astronomical Calendar 2004, by Guy Ottewell.

Solar - Moon passes between the earth and the sun.
Lunar - Earth passes between the sun and moon.
Upcomming total eclipses:
  • 2005 April 8 - Total solar eclipse visable in a populated area:
    Total eclipse visible from northern South America (Venezuela, Columbia, Panama). Partial visible from southern US and western South America. (see map (PDF))
  • 2004 May 4 - Total Lunar eclipse - Visible in Asia, Europe except western region, Africa except northwestern part, Indonesia, Australia, New Zealand, the eastern South Atlantic Ocean, the Indian Ocean, and the western Pacific Ocean;
  • 2004 October 28 - Total Lunar eclipse - The beginning of the umbral phase visible in Africa, Europe, Greenland, the Arctic region, North America except the extreme northwest, Central America, South America The end visible in North America, the Arctic region, Greenland, Central America, South America, Europe.
More at the eclipse page.
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.
Name Last Next
2P/Encke 20002003 December 29 4
C/2002 T7 (LINEAR) 2004 April 23 1-2
C/2003 T3 (Tabur) 2004 April 28 8
C/2001 q4 (NEAT) 2004 May 15 1-2
C/2003 K4 (LINEAR) 2004 October 13 5-6
Halley1986 2061
Chiron (2) 19962046
C/2014 Q2 Lovejoy 20142633? 4.5
C/1996 B2 (Hyakutake) 199610-18,000 (3)
Hale-Bopp 19975500
Tempel-Tuttle 19982031
Swift-Tuttle 19922122
Thatcher 18612276
(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 at U. of Arizona
Comets |
Comets currently Visable and Great Comets in History at NASA.
Comets, Meteors, And Asteroids

Meteor Showers
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.

The main meteor showers in 2007 are:
Name Dates ZHR * Comet Period
Quadrantids (QUA) 1 to 5 of January 120 2003 EH1 † 5-7  
Lyrids (LYR) 16 to the 25 of April 15 Thatcher 415 2276
Eta-Aquarids (ETA) April 19 to May 28 60 Halley 75 2061
Southern Delta-Aquarids (SDA) July 12 to August 19 20 unknown    
Orionids (ORI) Oct 2 to Nov 7 23 Halley 75 2061
Perseids (PER) July 17 to August 24 100 Swift-Tuttle 130 2122
Aurigids 2 Sept 1 200 Kiess 1905 2122
Leonids (LEO) 10 to 23 of November 15+ (1) Tempel-Tuttle 33.2 2031
Geminids (GEM) 7 to 17 of December 120 Asteroid
Taurids Nov 10 Encke 3.3 2010
Ursids (URS) 17 to 26 Dec 10 8P/Tuttle 13.5 2008
* ZHR: Zenithal Hourly Rate - a calculated maximum number of meteors an ideal observer would see in perfectly clear skies with the shower radiant overhead.

1. ZHR for Leonids in 1998 just after the Tempel-Tuttle comet passed was several hundred.
(Note: Hourly Rate (ZHR) will drop off over time until the comet that left the particles reappears. This can be from a few years to hundreds of years.)

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.

Viewing Tips at
Perseid Meteor Shower

2007 Meteor Shower Calendar at IMO

Sky Watch, The International Meteor Organization - IMO,
and The Central Coast Astronomical Society - CCAS
Meteor Showers List at
Annual Meteor Showers: Where and When to Look at

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.
See Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast | American Geophysical Union (

Some memorable impacts: <
Year what/where explosion yield
1859 Airburst Tom's River, NJ ?
1908 Airburst Tunguska, Siberia 10-15 Megatonnes
1963Off the coast of South Africa 176-356 kilotonnes
2006 Egypt 10-20 killotones
2009 South Sulawesi, Indonesia 30-50 Killotonnes
2012 Sutter's Mill meteorite.
Lotus, California
4 Killotones
2013 Chelyabinsk Russia 600 killotones
See many more at List of meteor air bursts - Wikipedia.
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).

HowStuffWorks "10 Memorable Meteor Crashes"
Impact event - Wikipedia
List of meteor air bursts - Wikipedia
Asteroid impacts on Earth: Skyfalls | The Economist

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.
  • 2003 Hermes is an asteroid with an orbit that brings it into the inner solar system. Orbital Period is about 2 yrs. Last visit was Nov. 4, 2003.
  • On Monday, 12 February 2001, the NEAR spacecraft touched down on asteroid Eros
  • Ceres is large enough to be viewed with binoculars at certain times.
  • Asteriods may be the remnants of larger "planetoids" that collided with each other between the orbits of Mars and Jupiter.
10 Largest
Name Diameter
Ceres 621.86
Pallas 376.96
Vesta 333.56
Hygeria 279
Euphrosyne 229.4
Interamnia 217
Davida 200.26
Cybele 191.58
Europa (3) 179.18
Patienta 171.12
Chiron (2) 100-150
(2) Chiron is categorized as both an Asteroid and Comet.
(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.
Solar activity follows an 11-year cycle, with the most intense events occurring near the cycle peak. For the current Cycle 24, the geomagnetic storm risk is projected to peak in early 2015.

The largest solar flare recorded was in November 2008

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. Causes:
Solar flares are associated with Coronal Mass Ejections (CMEs) which can ultimately lead to geomagnetic storms.

See Solar Flare and Sun Spots

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.
The Carrington event (a solar flare) caused auroras all over planet Earth so brilliant that newspapers could be read as easily as in daylight. Telegraph systems worldwide went haywire. Spark discharges shocked telegraph operators and set the telegraph paper on fire.

A Carrington-class flare today would be devistating.
a recent paper estimates potential damage to the 900-plus satellites currently in orbit could cost between $30 billion and $70 billion. The best solution, they say: have a pipeline of comsats ready for launch.
Spacewalking astronauts might have only minutes after the first flash of light to find shelter from energetic solar particles following close on the heels of those initial photons.

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.
Flares are characterized by their brightness in X-rays (X-Ray flux), the GEOS (Geostationary Earth Orbit Satellite) Class

Follow activity with your mobile phone:
Spaceweather Text is an astronomy alert service from the creators of Sign up for our service and we'll text you when things are happening in the sky. $7/mo.
Solar Monitor iOS app $10
Solar Alert app 3.5 (41) Free Interplanetary 3D Sun (i3dsun) app from NASA

Solar Flare and Sun Spots
Solar and Geomagnetic Data (last month)
Magnetic storms online |
Homepage | NOAA / NWS Space Weather Prediction Center
BBC NEWS | Science/Nature | Solar flare confirmed as biggest
Solar storm Risk to the north American electric grid
Geomagnetic storm - Wikipedia
Solar Storms, Flares, CMEs, Geomagnetic Storms, Vulnerable Grid
How to Protect Your Home from Solar Flares and Solar Storms | Today's Homeowner

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.
A planet might be a "morning star" at one time of the year and "evening star" at other times.

Every twenty-six months, the Earth passes between Mars and the sun. Astronomers call this moment "opposition" because, as seen from Earth, Mars lies opposite the sun in the sky. This is the time when Mars lies closest to us, shines at its brightest and appears largest in a telescope.

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

On June 8, 2004 venus' orbit took it between the earth and sun.

Mars 2003
5 brightest planets allign every 18 years
Glossary for planets
The nine planets at U. Arizona
Planet Visibility

Man-made Objects (Satellites, Space Shuttle, Space Station)
Large satellites, e.g. The International Space Station (ISS) and The Space Shuttle and some with relatively low orbits e.g. Iridium satellites, can be seen with the naked eye or with the aid of binoculars.

j-Pass at NASA
SatPasses - Satellite Passes Over North American Cities at

Galaxy Collision
6 billion years or so from now our Milky Way Galaxy and our neighboring Andromeda galaxy may collide. Galaxies are mostly empty space (the nearest star to the sun is 4 light years away), so there will not be a lot star/planet collisions.

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)
UT 0 3 6 9 12 15 18 21
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

Return to Don's Home.

last updated 6 May 2015