Category: Astronomy

After 16 days in space and 250 orbits of the Earth, space shuttle Endeavour touched down at Wednesday evening at NASA’s Kennedy Space Center in Florida, bringing the STS-123 mission to a flawless end. The mission launched in darkness on March 11, and returned home with a rare night landing – and both were spectacular sights. For those of you keeping score at home, Endeavour’s main gear touchdown took place at 8:39:08 p.m. EDT at a mission elapsed time of 15 days, 18 hours, 10 minutes and 55 seconds.

Mission managers said the crew was in good health and spirits. “I got to talk to the crew, and the crew was just having a fantastic time reflecting on their mission and looking up at their vehicle that just landed,” said Shuttle Launch Director Mike Leinbach. “They were glad to be home, very proud of the work they did, and we’re very proud of the work they did, too.”

On board Endeavour were Mission Specialists Takao Doi of the Japan Aerospace Exploration Agency, Robert L. Behnken, and Rick Linnehan; Pilot Gregory H. Johnson; Commander Dominic Gorie; and Mission Specialist Mike Foreman, as well as European Space Agency astronaut Léopold Eyharts, who returned to Earth aboard Endeavour after almost 50 days in space on the International Space Station. The 16 day mission was one of the longest space shuttle missions, with 5 spacewalks for station construction that included attaching a Japanese Pressurized Module and putting together Dextre, a robotic handyman that will be available to assist in station construction and maintenence tasks.

If you missed seeing the landing last night, here’s a link to video from NASA

With the current shuttle mission going so well, this news is a little depressing. Future space shuttle missions may be delayed because a backlog of work is developing on external fuel tanks for the shuttles. The tank used by Endeavour for the current mission was the last in the inventory of ET’s built before the 2003 Columbia disaster. The next shuttle flight, scheduled for late May, will use the first of the new design of tanks that include improvements to help eliminate foam shedding. But production issues with subsequent tanks may force delays for future missions, including Atlantis’ STS-125 mission to service the Hubble Space Telescope, currently targeted for August 28. If the delays amount to more than a couple of months, it’s possible the Hubble could give out before the shuttle could get there because of failing batteries and gyroscopes.

Since for the Hubble mission, the shuttle wouldn’t be going to the International Space Station, there would be no safe haven option for Atlantis’ crew if major heat shield damage occurs. The station and Hubble are in different orbits and the shuttle does not have the ability to move from one to the other. As a result, NASA approved plans to have a second shuttle, Endeavour, ready for launch on a rescue mission just in case.

That means NASA needs two ready-to-fly external tanks for the Hubble mission. One should be ready, no problem, but the second one is the issue. Manpower and production issues are the main problems. The people at Michoud had to redo much of the work on existing fuel tanks, and then they took a direct hit from Hurricane Katrina in 2005. Some workers moved elsewhere, and the program has not been at peak production since. Additional unplanned work has also caused delays, such as the upgrade to the fuel sensors that plagued the last shuttle tank, used for the STS-122 mission.

For now, the Hubble mission remains officially scheduled for August 28, but some sources say the mission could be delayed to October. More on this as the picture becomes clearer and the story develops.

Original News Source: CBS News Space Place

Spring officially arrives for everyone, including astronomers on March 20. The word “Equinox” literally means “equal night”. It’s all about the balance of light – not the myth of balancing eggs. On Thursday, both the day and night are the same length. But what’s so special about it? It’s a date that most of us recognize as symbolic of changing seasons. North of Earth’s equator we welcome Spring, while people south of the equator are gearing up for the cooler temperatures of Autumn.

These all too brief, but monumental moments in Earth-time, owe their significance to the slightly more than 23 degree tilt of the Earth’s axis. Because of our planetary angle, we receive the Sun’s rays most directly during the Summer. In the Winter, when we are tilted away from the Sun, the rays pass through the atmosphere at a greater slant, bringing lower temperatures. If the Earth rotated on an axis perpendicular to the plane of the Earth’s orbit around the Sun, there would be no variation in day lengths or temperatures throughout the year, and we would not have seasons. At Equinox, the midway between these two times in Spring and Autumn, the spin axis of the Earth points 90 degrees away from the Sun.

If your head is spinning from all of this, sit and ponder for a moment. Now is a great time to choose a marker and observe what’s happening for yourself. Trying a real science experiment for equinox is much better than the myth of balancing eggs. Just place a stake of some type into the ground (or use a fencepost or signpost) and periodically over the next few weeks measure the length of the shadow when the Sun is at its highest and write down your measurements. It won’t take long before your marker’s shadow length changes and you notice how the Sun’s position changes in the sky, and with it the ecliptic plane.

In the language of astronomy, an equinox is either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. The Vernal Equinox is also known as “the first point of Aries” – a the point at which the Sun appears to cross the celestial equator from south to north. The equinoxes are not fixed points on the celestial sphere but move westward along the ecliptic, passing through all the constellations of the zodiac in 26,000 years. This is what’s known as the precession of the equinoxes – a motion first noted by Hipparchus roughly in 120 B.C. But what causes it?

The precession is caused the gravitational attraction of both the Moon and Sun on the equatorial bulge of the Earth. Imagine the Earth’s axis patterning itself in a cone as it moves, like a spinning top. As a result, the celestial equator, which lies in the plane of the Earth’s equator, moves on the celestial sphere, while the ecliptic, which lies in the plane of the Earth’s orbit around the Sun, is not affected by this motion. The equinoxes, which lie at the intersections of the celestial equator and the ecliptic, now move on the celestial sphere. Much the same, the celestial poles move in circles on the celestial sphere, so that there is a continual change in the star at or near one of these poles.

After a period of about 26,000 years the equinoxes and poles lie once again at nearly the same points on the celestial sphere. Because the gravitational effects of the Sun and Moon aren’t always the same, there is some wobble in the motion of the Earth’s axis called nutation. This wobble causes the celestial poles to move, not in perfect circles, but in a series of S-shaped curves with a period of 18.6 years that was first explained by Isaac Newton in 1687.

Go ahead and balance eggs for fun… But believe in science!

P.S. The Bad Astronomer Phil Plait has a tutorial video on his website, teaching you how to stand an egg on end, any time of the year. Click here to watch it.

If you’re watching the gibbous Moon cross the sky on the evening of March 19th, you’re likely to notice a yellowish looking star nearby. That’s not a star. It’s the planet Saturn. For those of you who missed Saturn’s close appearance to last month’s eclipsing Moon, you’ll have another chance to see the pair.

Right now Saturn is making its home in the constellation of Leo, a backwards question marked asterism of stars. If your eyes are sharp and the sky isn’t too bright, you’ll also notice Leo’s brightest star, Regulus, near Saturn as well. Now is a great time to view all three through binoculars. When Galileo first saw Saturn in 1610, his crude telescope couldn’t full resolve Saturn’s rings. He thought Saturn was a blurry triple system – two small orbs on either side of a large one. He reports read, “I have observed the highest planet to be triple.” Yet, the view you’ll get tonight will be the same as when Galileo wrote, “Has Saturn swallowed his children?” the current tilt of Saturn’s rings will be virtually invisible to binoculars.

If you’re thinking this is quite similar to last month’s eclipsing Moon/Saturn appearance, you’d be correct – only this time the pair meet up two days before the Moon reaches full. Saturn takes 29 and a half years to orbit our Sun and its progress through the constellations of the zodiac is very slow. It takes about 2 and half years for it to move from one constellation to the next. Do the math and you’ll find the last time Saturn was in Leo was 1979 and the last time Saturn and the Moon paired was only about 28 days ago.

You won’t have to wait long for the next event, though. For those living in New Zealand and Eastern Australia, be aware that the universal date of March 19th also means a lunar occultation event of Regulus for you! For example those living in Auckland will catch the event starting at 6 11 53 UT and those in Christchurch will see it at 6 28 13 UT. For detailed information on times and locations, go visit the International Occultation Timing Association (IOTA).

Wishing you clear skies…