Idaho Skies

January 2008

Vol.5 No.1

Idaho Skies is a column for beginning amateur astronomers and those interested in astronomy. Suggestions about the column are gladly accepted by the columnist, at paul.verhage@boiseschools.org

This month look for the star Alcyone, the brightest star in the open cluster, the Pleiades. The Japanese name the cluster, Subaru, so look carefully at the next Subaru you see. The symbol on the car is a stylized diagram of the Pleiades star cluster. The Pleiades goes by the name of M-45 and the Seven Sisters (although most people only see six stars without optical aid). The seven sisters were daughters of the titan, Atlas and his wife, Pleione. The names of the six stars most people see, in order of brightness, are Alcyone, Electra, Maia, Atlas, Merope, and Taygeta. The next three fainter stars are named after the their mother and the two remaining sisters, Pleione, Celaeno, and Asterope The first known mention of the Pleiades is by the Greek writer Hesiod around 1000 BC.

The Pleiades through 10X50 binoculars

In 10X50 binoculars, the brightest portion of the Pleiades occupies about 1/5^th of the field of view. When you include the fainter surrounding stars, the Pleiades occupies closer to 1/4^th of the field of view. In moderately light polluted skies, I could easily see 20 stars though my binoculars. In the diagram above, Alcyone, the brightest Pleiad is the star in the center.

The Pleiades are 440 light years away. Therefore, if you were born in 1567, the Pleiades are your birthday stars this year! There are some 500 stars in this galactic cluster. They formed from the same cloud of dust and gas about 100 million years ago. This means they were born during the middle of the Cretaceous period, or during the hey day of the dinosaurs. In time, the stars of the Pleiades will drift a part, as their combined gravity is too weak to hold the cluster together. There are too few stars spread too far a part to hold the cluster together. In long duration exposures, there’s a blue cloud of dust visible surrounding the stars. The stars and bright blue-white frosting makes the Pleiades look like some fantastic piece of jewelry. The cloud is not the remains of the dust and gas from which the Pleiades formed. It happens to be a separate cloud that the cluster is currently drifting through. Recent findings have discovered that the cloud of dust is actually two separate clouds that are passing each other just as the Pleiades are passing through the same area.

January 1 – 7

Our blue world is at perihelion on the 3^rd. Since the Earth orbits the Sun in an elliptical orbit, there are two times when the Earth is at its closest and farthest points from the Sun. Perihelion is the name for the point in Earth’s orbit that is closest to the sun. Perihelion has an insignificant effect on Earth’s climate and certainly is not the cause of the season. Today we are 91,375,384 miles from the Sun, or 98.3% of our average distance which astronomers call the Astronomical Unit (AU).

Also today, the moon is also at apogee, or its greatest distance from Earth. Measured from center to center, Earth and the moon are 251,681 miles apart on the 3^rd.

The Quadrantid meteor shower reaches its peak on the morning of the 4^th, just after midnight in fact. The moon is two days from new and 13% illuminated, so it will rise near sunrise (5:20 AM) and reflect very little interfering light. With the dark skies and peak shower occurring just before the shower’s radiant rises, this year’s Quadrantid meteor shower promises to be good. Your best views should begin around 1:00 AM and the meteors will appear to originate from the low northeast. This will be a shower to watch because the next meteor shower worth watching doesn’t occur until late April.

Isaac Newton celebrates his 365^th birthday on the 4^th. When Newton was born in 1643, the Western world was still using the Julian calendar, which pushed his birthday back to Christmas Day. Newton is best known for his discovery of how gravity works. In the 1660’s, while on break from the university because of the plaque running through London that year, Newton observed an apple fall from a tree and wondered if the force of gravity that brought it to the ground was a force that could explain the movement of the Moon around the Earth. Physicists wondered if gravity dropped in strength with the square of the distance between object. In other words, if the distance between two objects doubled, would the strength of the gravity between them be only 1/4^th as strong. Using an estimate of the distance between the Earth and Moon and the Moon’s orbital period around the Earth, Newton estimated how fast the Moon must be falling towards the Earth. The amount was a close agreement for a force that dropped off by the square of the distance. Today we call such forces 1/R² forces and they include the force of magnetism and electric fields. The same year Newton made his gravitational discovery, he developed a method of mathematical calculation called Calculus that proved that planets would move in elliptical orbits under a 1/R² force. He also discovered the spectrum of light. Anyone using a reflecting telescope is using a design first developed by Isaac Newton. Happy birthday, Isaac.

Forty years ago on the 6^th, NASA launched Surveyor 7 for the Moon. Surveyor was a program of seven unmanned spacecraft targeted for unmanned soft landings on the Moon and a prelude to the manned Apollo landings. Surveyor 7 made the fifth successful American landing on the Moon, two previous Surveyors, numbers 2 and 4, made it to the Noon, but crashed during their landing attempts. After landing on the 10^th, Surveyor 7 returned over 21,000 pictures of the lunar surface, dug trenches, moved rocks, and sampled the lunar surface with its alpha backscatter experiment. Since other Surveyors had successfully landed in lunar maria, NASA targeted Surveyor 7 for a highlands area near the crater Tycho. Surveyor 7’s experiments discovered the lunar highlands were not as rich in iron and iron-loving elements as the lunar maria.

January 8 – 14

The moon is new on the 8^th. If you’re looking for dark skies, this is your night. From our perspective, the Moon passes 5-1/2 degrees south of the Sun, or eleven times the Sun’s diameter as seen from Earth.

The 8^th is the 35^th anniversary of the Soviet’s launch of Luna 21. From the name of the spacecraft, you can guess its target was the Moon. Luna 21 was a soft landing attempt, but this time, the spacecraft carried a passenger, a rover. Lunokhod 2 was a four foot tall moon buggy controlled by a team of five drivers back on Earth. The rover weighed 1,850 pounds and was solar powered. Its eight wheels each had their own motor that drove at two speeds, roughly 0.6 and 1.2 mph. Television cameras provided its Earth-crew a 360 degree panorama around the rover. The solar array powering the rover was located on the inside surface of a closing lid. During the long and cold lunar night, drivers commanded the lid to close for insulation, allowing the rover’s internal radioactive to keep its interior warm enough to prevent damaging freezing. Lunokhod 2 traveled nearly 22 miles across the lunar surface, returned 80,000 television pictures, measured the lunar magnetic field, and tested the strength of the lunar soil, or regolith. Onboard the Soviets placed a French built laser retro-reflector to allow observatories on Earth measure the distance between the Earth and Moon.

Here’s a chance to find the last planet of the solar system, that’s right, Neptune. On the 10^th, the moon will lead you so close to the planet that you should see it in binoculars if you have dark skies. The only difficulty is that the moon will be in the low southwest when it gets dark, so you need a clear horizon and dark skies. In binoculars, you’ll see the scene illustrated below. The other two stars in the diagram are comparable in brightness to Neptune.

January 15 – 21

The Moon reaches the first quarter phase on the 15^th. The first quarter phase is the best phase to go moon watching because the moon is up in the evening (as opposed in the morning) and the shadows along the r lunar terminator show the greatest amount of detail.

Close to the sun, the first Mercury flyby of the MESSENGER spacecraft occurs on the 15^th. MESSENGER stands for MErcury Surface, Space Environment, GEochemistry, and Ranging. MESSENGER is an American spacecraft developed by the Johns Hopkins Applied Physics Laboratory and launched by NASA. It left Earth on 3 August 2004 (just over three years ago) and is finally reaching Mercury for the first time. The reason it has taken so long for MESSENGER to reach Mercury is that will eventually the spacecraft will go into orbit around Mercury. However, to do so, it had to lose a lot of speed. Rather than lose payload for fuel, the MESSENGER spacecraft has been playing a game of cosmic billiards with Earth and Venus. Each pass by these planets has sapped some of its speed and dropped it into a lower orbit around the sun. After three passes of Mercury, the spacecraft will have just the right speed to use its thrusters to enter into a Mercurian orbit in March 2011. Above Mercury, MESSENGER will photograph nearly the entire surface of this planet and map its composition. You can read about this mission at its webpage, http://messenger.jhuapl.edu/.

The moon passes close enough to the Pleiades star cluster on the night of the 17^th that both are visible together in your binoculars. Just look overhead after it gets dark, the Pleiades will be to the moon’s lower left

On the 19^th, the moon is at the perigee of its orbit around Earth. The distance between the center of the earth and moon is 227,689 miles today. It would take the average adult 8 years and 8 months to walk this distance. Lucky then that this is space and tennis shoes won’t wear out on the walk.

Also on the 19^th, the red planet, Mars, is to the upper right of the waning gibbous moon. Look for them after it gets dark. Mars will appear as the bright orange star. Mars is not really red; it’s more brown or orange.

January 22 – 31

The moon is full on the 22^nd. The Full Moon in January is often called the Old Moon. If you wanted to see faint objects in the sky, this is not your night.

Look for the moon on the night of the 22^nd. Six lunar diameters above it, or three degrees, is the Beehive star cluster. That’s close enough that both will easily fit within your binoculars. You’ll see more stars in the cluster if you move the moon out of your binoculars field of view.

Saturn is to the moon’s upper left on the evening of the 24^th. Their distance a part is just under half the field of view of your binoculars

Fifty years ago on the 31^st, the United States entered the space age with the launch of Explorer 1. The Jet Propulsion Laboratory in Pasadena, California designed and built Explorer 1. The 31 pound, 81 inch long, and 7 inch diameter spacecraft was launched on top a Juno rocket. Juno was a variation of the Redstone missile developed by von Braun’s team in Huntsville, Alabama. President Eisenhower gave the US Army the go ahead to launch an American spacecraft into orbit when it appeared the Navy would be unable to do it with project Vanguard. Approximately half of Explorer 1 was taken up by its final engine, so the top have contained its experiments, Geiger counters, a microphone, temperature gauge, and radio. If you’ve seen footage of the launch, you’ll notice the top of the rocket is spinning before the main engines fire. The spinning kept the satellite pointed in the correct direction in case the solid fuel boosters (Sergeant rockets) of the second, third, and fourth stages miss-fired. Explorer 1 was the third spacecraft in Earth orbit and the one to discover a belt of radiation surrounding Earth above its equator. Since physicist James van Allen built the Geiger counters that discovered this radiation, we call the belts the Van Allen belts today. Explorer 1 entered a 224 by 1575 mile orbit and remained in Earth orbit until 1972 when air friction finally brought it back to Earth.

This Month’s Topic

Getting Help with Your New Telescope

So did you get a telescope for Christmas? If so, you can get help using it from one of Idaho’s three astronomy clubs. The clubs meet monthly and the members will be very happy to help you out. Even if you didn’t get a telescope, or don’t have a telescope, visit your local astronomy club and see what’s happening in the night sky.

A List of Idaho Astronomy Clubs

Boise Astronomical Society

Boise

http://www.boiseastro.org

The BAS meets on the second Friday of the month at the Discover Center of Idaho. Meetings are usually held in the back classroom and begin at 7:30 PM. BAS holds a beginner’s astronomy class. Check the website for the start of the next class.

Idaho Falls Astronomical Society

Idaho Falls

http://www.allidaho.net/users/skygaz/ifas/ifas.html

The IFAS meets the fourth Wednesday of the month at the Idaho Falls public library. Meetings begin at 7:00 PM.

Magic Valley Astronomical Society

Twin Falls

http://members.tripod.com/mvas/

http://www.mvas.net

The MVAS meets on the second Saturday of the month at the Herrett Center classroom. Meetings begin at 7:00 PM and are followed observation time in the Centennial Observatory.

Pocatello Astronomical Society

Pocotello

The PAS meets the fourth Wednesday of the month at the Pocatello public library. Meetings begin at 7:00 PM.

If you’re in Kansas, try:

Northeast Kansas Amateur Astronomers League

Topeka

www.nekaal.org

The NEKAAL meets on the fourth Thursday of the month at Washburn University, Stoffer Science Hall, Room 103. NEKAAL operates Farpoint Observatory and it’s open to the public.

This Month’s Sources

The Royal Society of Canada, Observer’s Handbook 2008

Baalke, Ron, Space Calendar, 30 Oct 2007, <www.jpl.nasa.gov/calendar/>

Kaler, James, Stars, <www.astro.uiuc.edu/~kaler/sow/>

Night Sky Explorer (software)

Kronk, Gary W., Quadrantids, 30 Oct 2007, <http://meteorshowersonline.com/quadrantids.html>

Wikipedia, Isaac Newton, 28 Oct 2007, 30 Oct 2007, <http://en.wikipedia.org/wiki/Isaac_Newton>

NASA, Surveyor 7, 10 Oct 2005, 30 Oct 2007, <http://nssdc.gsfc.nasa.gov/nmc/tmp/1968-001A.html>

NASA, Luna 21, 30 Oct 2007, http://nssdc.gsfc.nasa.gov/nmc/tmp/1973-001A.html

Hart, Douglas, The Encyclopedia of Soviet Spacecraft, 1987

Gatland, Kenneth, Space Technology, Salamander Books Ltd, 1981

Dark Skies and Bright Stars,

Your Interstellar Guide