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Welcome again to our monthly newsletter with features on exciting celestial and earth science events, product reviews, tips & tricks, and a monthly sky calendar. We hope you enjoy it!
Astro-tourism has become increasingly popular in recent years. Beyond the traditional solar eclipse tours, we now have Venus transit tours, aurora tours, and many others. However, any trip can become an astro-tour if you're on the lookout for attractions with an astronomical theme. Starry Night becomes an aid to planning your itinerary and even finding your way around “foreign” skies, when you load it onto your laptop.
I recently spent a couple of weeks in Arizona, a Mecca for astro-tourists. This was my third visit to Arizona, and over the years I've sampled many of the astronomical tourist sights.
Flagstaff is my favorite astro destination. Its greatest treasure is Lowell Observatory, which sits atop Mars Hill on the western edge of the city <www.lowell.edu>. This makes an interesting day tour, but the greatest treat comes on the nights when its famous 24-inch Alvan Clark refractor is in operation. This is the telescope with which Percival Lowell made his famous observations of the “canals” of Mars. Don't let that put you off: it's one of the finest visual telescopes in the world. Flagstaff is also the home of the US Naval Observatory <www.nofs.navy.mil>, not generally open to the public.
A day trip east of Flagstaff takes you to the Barringer Meteor Crater <www.barringercrater.com>. This is not the largest meteor crater on Earth, but is one of the most recent. Much of the original formation is still well preserved, making it look as “fresh” as the craters on the Moon. When I first visited Barringer, it was possible to walk all the way around the rim of the crater; in fact we pushed our young son in his stroller all the way around. Perhaps because of abuses like ours, it's no longer possible to walk the full rim.
The more serious observatories are located in the southern part of the state. The jewel in the crown is Kitt Peak National Observatory, located on the land of the Tohono O'odham Nation (formerly known as the Papago) <www.noao.edu/kpno/>. This has the world's largest collection of optical telescopes, including the 4-meter Mayall Telescope and the McMath-Pierce Solar Telescope, which looks like a huge piece of modern sculpture <nsokp.nso.edu>. Most interesting to the astro-tourist are the nighttime observing programs offered year-round <www.noao.edu/outreach/kpoutreach.html>.
Another interesting observatory is located in the mountains to the northeast of Tucson: Mount Graham Observatory <mgpc3.as.arizona.edu/Visitor.htm>. It is possible to tour the observatory during the day, but no observing is offered to the public at night.
When traveling, use the internet to find out when and where local clubs will be holding their meetings or star parties <skyandtelescope.com/community/organizations>. This is an excellent opportunity to meet the locals and visit the best observing locations. For example, in Arizona there are large and active astronomy clubs in all the major cities, including Phoenix, Tucson, and Flagstaff.
A different kind of astronomical experience is offered by some bed and breakfasts which cater to amateur astronomers. There are several of them in Arizona (and many other parts of the world). Try Googling “astronomy B&B.”
No matter where you are in Arizona, if you have traveled south to escape the northern winter, there will be objects visible in the sky that you can't see from home. Even in northern Arizona, say visiting Canyon de Chelly National Monument (which I chose because it has a nice panorama in Starry Night), some of the glorious “southern” deep sky objects will be nicely visible. Here is the view looking south over Canyon de Chelly in early April 1 just after midnight.
Two of the finest southern objects just clear the horizon, due south of Spica. Centaurus A, so named because it's a powerful radio source, is the famous “hamburger galaxy”: two galaxies in a colossal collision. Omega Centauri is the largest brightest globular cluster in the sky; some astronomers believe that is actually the remnant of a galaxy cannibalized by the Milky Way Galaxy. Both are bright objects in binoculars, and Omega Centauri is actually visible to the naked eye.
I've also indicated the location of the Southern Pinwheel Galaxy, Messier 83. Most northern observers consider this one of the most difficult of the Messier objects, but that is mainly because it is down low on the murky horizon across Canada, the northern United States, and Europe. Seen from further south, it is one of the glories of the night sky, again easily visible in binoculars.
This is just an example of how Starry Night can be used to plan astronomical viewing when you are traveling. If you are going to the Southern Hemisphere, you will be experiencing a whole new sky, and even experienced stargazers will find themselves lost when confronted with southern skies. Starry Night will make you feel right at home wherever you are.
The Layered Earth makes it easy to capture student attention by examining the geological forces at work behind current events. Here we assemble some useful tools for teaching about the March 11, 2011 Japan earthquake and tsunami in the classroom.
On Friday, March 11, 2011, Japan experienced a catastrophic earthquake at 2:46:23 pm local time (12:46:23 am EST). The earthquake occurred off the coast of the island of Honshu, approximately 80 miles (129 km) east of the community of Sendai.
The 9.0 Richter magnitude earthquake and the resulting tsunami have provoked the largest crisis that Japan has encountered since the end of World War II. The Honshu earthquake was the world's fourth largest earthquake since 1900 and the largest in Japan since modern instrumental recordings began 130 years ago. About 1,500 earthquakes strike the island nation every year. Minor tremors occur on a nearly daily basis.
For graphics, video and PDF downloads visit a special site we have developed at The Layered Earth...
The 9th magnitude Tōhoku Region earthquake that struck Japan on March 11th, 2011 was the largest in the country's recorded history. That's saying something when you're talking about Japan; this is a country where architects design tall buildings to sway rather than break, where coastal cities have strong walls in the event of a tsunami, and where children practice earthquake drills in school from a young age.
Conservation of angular momentum
It's a mouthful but the concept isn't too difficult to understand – if something is spinning, and its mass suddenly gets pulled closer to its center, it will start to spin faster. It has to have the same amount of momentum before and after the collapse, so when the radius gets smaller the spin has to speed up. Picture a figure skater spinning – when she pulls her arms in she'll start to spin faster.
A subduction zone is a place where one of the Earth's tectonic plates – the giant “puzzle pieces” that make up the Earth's crust – slides underneath another one. That's what's happening east of Japan, and all around the Pacific ocean in a plate boundary called the Ring of Fire. The quake in March 2011 was caused by the Pacific plate sliding underneath the Okhotsk and Eurasian plates, causing them to spring upwards and send a massive tsunami crashing ashore.
Enough of the Pacific plate slid underneath that it had the effect of a figure skater pulling her arms in – some of the Earth's mass moved inwards, and the rotation sped up a bit. How much did it speed up? Not very much – each day is now about 1.8 microseconds (millionths of a second!) shorter than before the quake.
By comparison, there are occasional fluctuations in the Earth's rotation speed, caused by the movement of material in the mantle and outer core. When dense stuff falls inwards, the rotation speeds up. These variations result in changes in the length of day equal to a few milliseconds every decade.
The tidal forces between the Earth and the Moon play a part in slowing down the Earth's rotation gradually over time. This gravitational drag results in a lengthening of the day by two milliseconds every hundred years.
Even weather systems can affect the rotation. During the northern hemisphere's winter and southern hemisphere's summer, the rotation slows so that an entire millisecond is added to the length of the day over six months – and at the other end of the year that extra millisecond is taken away by faster rotation. This is all due to the interactions between the oceans, atmosphere, and land.
How do we know this stuff?
The speed of the Earth's rotation can be measured very precisely by careful observations of quasars, which are some of the most distant objects we can see in the universe. Measuring their position in our sky tells us how fast a point on the earth is moving relative to the background sky.
The Tōhoku quake had severe and tragic effects on humanity; however, the shortening of the day is not something that anyone has to worry about.
Brenda M. Shaw
On March 10 -12, 2011 Starry Night attended the National Science Teachers Association conference in San Francisco. In addition to the California sunshine, we enjoyed interacting with teachers at our booth and during our workshops.
At our booth, teachers were able to get hands-on experience with Starry Night High School, Starry Night Middle School, Starry Night Elementary, Starry Night College and our new geology program The Layered Earth. Of special interest was our live feed from the US Geological Survey showing the many aftershocks of the Japan earthquake.
You can learn more about this quake and download a pictorial lesson from here:
Our workshops featured in-depth demonstrations of The Layered Earth and presentations of Journey to the Center of the Milky Way and The Sky through the Ages using Starry Night High School.
In our Journey to the Center of the Milky Way, we set out from the Earth and stopped to explore lessons dealing with the Moon, the planets and stars from those offered in Starry Night High School. You can download some sample lessons using the following link.
In the Sky through the Ages, we looked up at the night sky at specific times in the past. Our first stop was somewhere in Europe around 50 000 BC.
Looking north we see the familiar constellation Ursa Major and its asterism, the Big Dipper. But look what stellar motion has done to the familiar shape! Compare it with the present-day outline below and you can easily see that stars do indeed move relative to each other even though it takes a long time for that motion to become apparent.
We also looked at the night sky seen by the builders of the pyramids, an ancient solar eclipse and the view from Berlin Observatory on the evening of September 23, 1846. It was then that a new planet was discovered -- Neptune, the last of the giant planets in our solar system.
To discover Neptune yourself, load the file Neptune.snf and search with the mouse pointer until you find the very faint Neptune. If you have difficulty finding the planet, step time forward several times and Neptune will reveal itself by its motion relative to the background stars. Can you find another planet in the field?
It's instructive using Starry Night to see what the night sky looked like on other historical occasions. Load the file 1912.snf to answer the following questions:
Answer to last month's question:
Q: What is the relationship between sidereal and solar time?
A: Sidereal time is based on the rotation of the Earth relative to the stars. Solar time is based on the rotation of the Earth relative to the mean Sun. Solar days are about 4 minutes longer than sidereal days.
In addition to the 88 standard constellations, the night sky contains a number of other easily recognizable patterns of bright stars. These patterns—called asterisms—may be part of a single constellation or consist of stars from different constellations. The Big Dipper, for example, is part of the constellation of Ursa Major. The Summer Triangle includes stars from several different constellations.
Don't let the scale of the diagram above fool you: Hydra is the largest constellation, and covers some 90° of sky. At this time of year, from mid-northern latitudes, it lies along the southern horizon at midnight.
To start, M83 is an impressive barred spiral galaxy that, from our vantage point in space, lies almost face-on. Even small scopes should pick up its obvious structure.
M68 is a nice globular cluster, 33,000 lightyears away. It's visible in binoculars but a telescope brings out the individual suns.
NGC 3242, the Ghost of Jupiter, is one of the finest planetary nebulae in the sky. It's a full magnitude brighter than the more famous Ring Nebula (M57) in Lyra. A small telescope reveals a pale blue disc with diffuse edges and the prominent 11th magnitude star. Due to its high surface brightness, this target takes high magnification quite well: try 200x or 250x to see the football-shaped interior and faint shell.
NGC 3115, the Spindle Galaxy, is actually in Sextans. In contrast to M83, this galaxy is seen almost edge on. It's a lenticular galaxy, meaning it's a disc galaxy with very little spiral structure.