The space shuttle Atlantis touched down at NASA’s Kennedy Space Center on Friday completing an 11-day mission to upgrade the International Space Station. During their time in orbit, the seven shuttle astronauts completed 4 spacewalks and installed over $1 billion in equipment, including a 13.5 ton metal beam which will serve as the backbone for future modules on the station. Astronaut Jerry Ross made history with this flight, becoming the first person to go into space seven times.
Planets Line Up in Spectacular Show
Image credit: Harvard
During late April and May you’ll get an opportunity to see the five brightest planets lined up in a single evening. Look West in the early evening sky and you’ll be able to see Mercury, Venus, Mars, Jupiter, and Saturn grouped up. The grouping is fairly rare and won’t be seen again until 2040.
Comet Hale-Bopp dazzled us for weeks. The Perseid meteor shower thrilled us for one night. But the world hasn’t seen anything like the planetary traffic jam that’s going to occur the last week of April and the first two weeks in May!
Inching across the sky like bumper-to-bumper commuters on their way to work, a rare planetary alignment will allow sky observers to see every planet in our solar system in a single evening! “There will be other opportunities in the future to see the planets in different configurations,” says Philip Sadler, Director of the Science Education Department at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA, ” but it won’t be anything like this for at least another 70 years. This is truly a once-in-a-lifetime experience.”
In the past, many different configurations of planetary alignments have been seen from Earth. They occur due to the random positions of the planets in their eccentric orbits around the Sun. In the early 1980s and in May of 2000, the planets stacked up directly behind the Sun. Many people thought the combined gravitational pull might create havoc here on Earth resulting in giant earthquakes, sweeping tidal waves or erupting volcanoes. But, the collective gravitational pull was so insignificant, nothing happened. What was the reason? The other planets are simply too small or too far away in space to affect us back on Earth. To see just how insignificant the gravitational pull of the planets can be, let’s do what many good, red-blooded Americans like to do. Let’s go shopping!
Imagine if we stood in the produce section of a grocery store and held up a big yellow grapefruit representing the Sun. The planet Mercury would be the size of a small grain of salt orbiting around it 18 feet away. Venus would be somewhat larger, like a grain of sugar you get in those little brown packets at the coffee shops, 34 feet away. Earth, also a grain of sugar, would be located 50 feet away. Mars also would be the size of a grain of salt 75 feet away. As for the rest of the planets: Jupiter, a cherry-sized tomato, would be found at 240 feet; Saturn, the size of a green grape, at 420 feet; Uranus, a frozen green pea, at 300 yards; Neptune, also the size of a frozen pea, at 470 yards; and Pluto, represented by a speck of dust, would orbit our grapefruit-sized Sun at a distance of 475-600 yards. As you’ve probably guessed, not much gravitational pull is exerted on the Earth by these grocery store lightweights!
In early May, when the planets line up, they will not be arranged behind one another or the Sun. Instead, they will present a beautiful line across the sky from horizon to near zenith. For a period of a little more than three weeks, anyone looking west at sunset will be able to see the planets Mercury, Venus, Mars, Saturn and Jupiter. A few hours later at 4 A.M., armed with a large-size amateur telescope, they can continue their grand tour by observing Uranus, Neptune, and Pluto. By quickly glancing down at the ground, they will have completed their grand tour of the solar system.
Looking at the planets spread out across the sky during this alignment also demonstrates, better than any book, how our solar system formed 4 billion years ago; something astronomers just recently have begun seeing around other distant stars in space. “Our solar system condensed out of a nebular dust cloud that flattened down into a giant disk that resembled a big pizza pan,” says CfA astrophysicist David Wilner. “Utilizing instruments like the Hubble Space Telescope and data from the Infrared Astronomical Satellite, we are now witnessing the formation of new solar systems spread out into flattened discs of gas and dust. We are even detecting large lumps of material in the dust disks that may be the signatures of planets in formation. Astronomers are now assembling snapshots of our own past frozen in time billions of years ago.”
This pathway of planets, or the ecliptic as astronomers call it, is what remains after our dust cloud coalesced into planets. Tracing the path of this ancient dust ring across the sky is easy. Stand sideways facing south with your right hand extended and pointing to where the Sun recently set along the western horizon. Now, extend your arm up to point at the Moon or a bright planet overhead. Connecting these two points together, continue to sweep your arm in an arc until it reaches the opposite horizon. Bingo! You have just traced out the ecliptic. All the planets will be found along this line and nowhere else. And this is where the traffic jam will occur.
“Coincidentally,” says Sadler,” have you ever wondered why the zodiac sign were chosen? Why someone you know wasn’t born under the sign of Hercules or Orion?”
To the Greeks and Romans, the ecliptic was the Highway of the Gods or the path the planets and Moon moved across at night and the Sun traveled during the daytime. “Located directly behind this highway were the twelve special constellations the Gods passed by as they moved across the sky. They constituted the signs of the zodiac. This was the basis for astrology – religious beliefs and basic sky observations mixed together. It should not be confused with the science of astronomy that emerged centuries later,” says Sadler. Today, it is widely held by many historians and planetarium directors that a conjunction of the planets, similar to the one on May 5, accounts for the Star of Bethlehem that sent the Magi on their way to seek the Christ child. Certainly the timing was right. An almost identical triangular alignment of Saturn, Mars and Venus did take place on April 1, 2 B.C. And the planets Jupiter, Saturn and Mars also formed a triangular conjunction in 6 B.C., in the constellation Pisces, the sign of the Christians. However, renowned astronomical historian Prof. Owen Gingerich of the CfA disagrees. “The very, very short duration of a grouping of planets was not the Star of Bethlehem,” he states. “A conjugation like this would have meant nothing to the Magi. It was not part of their astrological tradition. It really wasn’t until Kepler became fascinated with the harmony of the planets in the 16th century that the idea of a planetary conjunction came about to try to attach a scientific explanation to this event. In fact, Kepler even went so far as to add an imaginary supernova to the conjunction of planets in 6 B.C. to try to make it even more spectacular to catch the Magi’s attention. ”
Will this event be religiously significant or just an astronomical oddity? Is it the most dramatic way to visualize how our solar system formed? Or, is it an exciting challenge for amateur astronomers to conduct their only whirlwind tour of the solar system in just one evening? Answering yes to any or all of the above makes the alignment of late April and early May something not to be missed. Nothing like it will occur again in our lifetime. At the very least, it presents a wonderful opportunity for friends and family to come together and share an experience beyond the daily routine. It also may be an opportunity to ponder our fragile existence on this tiny blue world racing around an ordinary yellow star with eight other planetary companions and maybe help us, just a little bit, bring our own world back into perspective.
Headquartered in Cambridge, Massachusetts, the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists organized into seven research divisions study the origin, evolution, and ultimate fate of the universe.
Original Source: CfA News Release
Ariane Launches Communications Satellite
An Ariane 44L rocket lifted off from the Guiana Space Center in Kourou on Tuesday evening at 2302 GMT (7:02 EDT). Twenty one minutes later the rocket deployed a Lockheed Martin-built NSS-7 telecommunications satellite which will provide Internet and data relay services to the Americas, Europe and Africa.
Hubble Searches for More Plutos
Image credit: NASA
The Hubble Space Telescope’s latest task is to track down elusive Pluto-like objects that lurk at the very edge of our Solar System – many of which seem to travel in pairs like Pluto and its moon Charon. These objects are classified as Kuiper Belt Objects (KBO) and can be found in a vast belt past Neptune. So far, 1% of KBOs have been found to be binary systems, a fact which puzzles astronomers.
NASA’s Hubble Space Telescope is hot on the trail of an intriguing new class of solar system object that might be called a Pluto “mini-me” ? dim and fleeting objects that travel in pairs in the frigid, mysterious outer realm of the solar system called the Kuiper Belt.
In results published today in the journal Nature, a team of astronomers led by Christian Veillet of the Canada-France-Hawaii Telescope Corporation (CFHT) in Kamuela, Hawaii, is reporting the most detailed observations yet of the Kuiper Belt object (KBO) 1998 WW31, which was discovered four years ago and found to be a binary last year by the CFHT.
Pluto and its moon Charon and countless icy bodies known as KBOs inhabit a vast region of space called the Kuiper Belt. This ‘junkyard’ of material left over from the solar system’s formation extends from the orbit of Neptune out to 100 times as far as the Earth is from the Sun (which is about 93 million miles) and is the source of at least half of the short-period comets that whiz through our solar system. Only recently have astronomers found that a small percentage of KBOs are actually two objects orbiting around each other, called binaries.
“More than one percent of the approximately 500 known KBOs are indeed binary: a puzzling fact for which many explanations will be proposed in what is going to be a very exciting and rapidly evolving field of research in the coming years,” says Veillet.
Hubble was able to measure the total mass of the pair based on their mutual 570-day orbit (a technique Isaac Newton used 400 years ago to estimate the mass of our Moon). The ‘odd-couple’ 1998 WW31 together are about 5,000 (0.0002) times less massive than Pluto and Charon.
Like a pair of waltzing skaters, the binary KBOs pivot around a common center of gravity. The orbit of 1998 WW31 is the most eccentric ever measured for any binary solar system object or planetary satellite. Its orbital distance varies by a factor of ten, from 2,500 to 25,000 miles (4,000 to 40,000 kilometers). It is difficult to determine how KBOs wind up traveling in pairs. They may have formed that way, born like twins, or may be produced by collisions where a single body is split in two.
Ever since the first KBO was discovered in 1992, astronomers have wondered how many KBOs may be binaries, but it was generally assumed that the observations would be too difficult for most telescopes. However, the insights to be gained from study of binary KBOs would be significant: measuring binary orbits provide estimates of KBO masses, and mutual eclipses of the binary allow astronomers to determine individual sizes and densities. Assuming some fraction of KBOs should be binary – just as has been discovered in the asteroid belt – astronomers eventually began to search for gravitationally entwined pairs of KBOs.
Then, finally, exactly a year ago on April 16, 2001, Veillet and collaborators announced the first discovery of a binary KBO: 1998 WW31. Since then, astronomers have reported the discoveries of six more binary KBOs. “It’s amazing that something that seems so hard to do and takes many years to accomplish can then trigger an avalanche of discoveries,” says Veillet. Four of those discoveries were made with the Hubble Space Telescope: two were discovered with a program led by Michael Brown of the California Institute of Technology in Pasadena, CA, and two more with a program led by Keith Noll of the Space Telescope Science Institute in Baltimore, MD. The sensitivity and resolution of Hubble is ideal for studying binary KBOs because the objects are so faint and so close together.
The Kuiper Belt is one of the last big missing puzzle pieces to understanding the origin and evolution of our solar system and planetary systems around other stars. Dust disks seen around other stars could be replenished by collisions among Kuiper Belt-type objects, which seems to be common among stars. These collisions offer fundamental clues to the birth of planetary systems.
Original Source: Hubble News Release
Atlantis Undocks from the Station, Prepares for Landing
Image credit: NASA
After a week of successful construction work, the 7-astronaut crew of the space shuttle Atlantis said their goodbyes to the crew of the International Space Station, closed the hatch, and undocked. During their time at the station, the crew of Atlantis installed $790 million in equipment, including a new girder and railcar which will support future expansion of the station. The shuttle is expected to land back in Florida on Friday.
Now separated from the International Space Station by about 85 statute miles and moving away at about 12 miles with each orbit of the Earth, Atlantis crewmembers turn their attention today to preparing for a return trip home.
The crew ? Commander Mike Bloomfield, Pilot Steve Frick, Mission Specialists Ellen Ochoa, Rex Walheim, Lee Morin, Jerry Ross and Steve Smith ? was awakened at 2:44 a.m. to ?Somewhere Over the Rainbow,? performed by Bloomfield?s daughter.
Bloomfield, Frick and Ochoa will test fire the reaction control system jets and flight control surfaces that will be used to guide Atlantis through the atmosphere on Friday morning. Atlantis is scheduled to return to the Kennedy Space Center in Florida at 11:26 a.m. CDT Friday where preliminary weather forecasts for landing are favorable.
Crewmembers will take a break from their on orbit work today to talk with media representatives from CNN, WDIV-TV in Detroit and the Fox News Network this morning in an interview beginning at 9:14
Atlantis? orbital maneuvering jets will be fired twice today. Once will be for scientists to look at the exhaust?s effects on radar echoes and effects of orbital kinetic energy on the ionosphere. The other firing will reduce the cross range for Friday?s backup landing opportunity in Florida. Walheim, Morin, Ross and Smith will continue to pack away equipment and supplies onboard the shuttle and prepare the cabin for landing.
On board the International Space Station the Expedition 4 crew ? Commander Yury Onufrienko and Flight Engineers Dan Bursch and Carl Walz ? was awakened at 3 a.m. They are preparing for their next visitors, a Soyuz taxi crew slated to arrive April 27. Onufrienko, Walz and Bursch, will board the current Soyuz spacecraft and move it from its location on the Zarya docking port to the Pirs docking compartment on Saturday to make room for the replacement Soyuz.
The crew of Atlantis will begin a scheduled eight-hour sleep period at 6:14 p.m. today, waking just after 2 a.m. Friday to prepare for reentry and landing of Atlantis concluding a successful mission to the station.
Original Source: NASA News Release
New Girder Bolted to Station
Atlantis astronauts Jerry Ross and Lee Morin completed a seven hour spacewalk on Saturday to finish bolting the newly installed S0 truss to the International Space Station. Dubbed the Silver Team because of their age (both are grandfathers), the two astronauts found some of the 54 bolts they tightened were a little sticky. The truss will hold the station’s giant solar wings and serve as a track for the Canadarm 2 to travel across the station.
Third Spacewalk Successful
Astronauts Steven Smith and Rex Walheim spent a productive day in space on Sunday as they continued to extend the International Space Station. During their six and a half hour spacewalk, the astronauts released a clamp that held the Mobile Transporter to the newly installed S0 truss. They also hooked up a set of connectors which will allow the Canadarm 2 to move along the truss and help out future construction.
Looking for Asteroids in the Earth’s Blindspot
Lately it seems that astronomers are discovering potentially harmful asteroids after they nearly miss our planet. This is because they’re coming from our planet’s “blind spot” – the space directly between the Earth and the Sun – and we can only see them after they pass. The European Space Agency is developing a new space-based observatory called Gaia, which will be able to see close to the Sun’s disk and detect many more of these previously unseen asteroids. Gaia is expected to launch in 2010.
New Railcar Has a Few Glitches
After installing their new railcar on the International Space Station yesterday, NASA wanted to take it for a spin. The railcar – which will be used in future phases of the station’s construction – rolled along the track for a few minutes but then it stalled. Controllers suspect the car drifted slightly in the low gravity causing its magnetic sensors to break contact with the aluminum rails.
Astronomers Find Five Double Asteroid Systems
Image credit: Cornell
According to researchers from Cornell University, binary asteroids – where a small asteroid orbits a larger one – are actually pretty common in Earth crossing orbits. In fact, they think that gravitational interactions with the Earth might actually help to cause the arrangement. The researchers estimate that 16% of asteroids larger than 200 metres in diameter have a companion – so far they’ve found five using two of the world’s largest radio telescopes.
Binary asteroids — two rocky objects orbiting about one another — appear to be common in Earth-crossing orbits, astronomers using the world’s two most powerful astronomical radar telescopes report. And it is probable, they say, that these double asteroid systems have been formed as a result of gravitational effects during close encounters with at least two of the inner planets, including Earth.
Writing in a report published by the journalScience on its Science Express web site (April 11, 2002), the researchers estimate that about 16 percent of so-called near-Earth asteroids (NEAs) larger than 200 meters (219 yards) in diameter are likely to be binary systems, with about a three-to-one relative size of the two encircling bodies. To date, five such binary systems have been identified by radar, says lead researcher Jean-Luc Margot, an O.K. Earl postdoctoral fellow in the Division of Geological and Planetary Sciences at the California Institute of Technology.
Margot, who at the time of the observations was a research associate in the planetary studies/radar group at the National Science Foundation’s (NSF) Arecibo Observatory in Puerto Rico (managed at Cornell University), says that theoretical and modeling results show the binary asteroids appear to be formed extremely close to Earth — within a distance equal to a few times the planet’s radius (6,378 kilometers or 3,963 miles). “The fact that one out of every six large NEAs is a binary and that they typically survive on the order of 10 million years, implies that these close encounters must happen frequently compared to the lifetime of the binary asteroids,” says Margot.
The Science article, “Binary Asteroids in the Near-Earth Object Population,” is coauthored by Michael Nolan, research associate at Arecibo; Lance Benner, Steven Ostro, Raymond Jurgens, Jon Giorgini and Martin Slade at the Jet Propulsion Laboratory (JPL); and Donald Campbell, professor of astronomy at Cornell. The observations were made at the 70-meter Goldstone NASA tracking telescope in California and at Arecibo Observatory.
NEAs are formed in the asteroid belt, between the orbits of Mars and Jupiter, and nudged by the gravitational attraction of nearby planets, largely Jupiter, into orbits that allow them to enter the Earth’s neighborhood. Most of the asteroids are the remnants of the initial agglomeration of the inner planets.
Astronomers have long speculated about the existence of binary NEAs, based in part on impact craters on Earth. Of about 28 known terrestrial impact craters with diameters greater than 20 kilometers, at least three are double craters formed by impacts of objects about the same size as the newly discovered binaries. Astronomers also have noted the changes in brightness of reflected sunlight for some NEAs, indicating a double system was causing an eclipse or occultation of one by the other.
In 2000, Margot and his co-researchers, using measurements from the Goldstone radar, found that a small, roughly 800-meter-diameter (half-a-mile) asteroid, 2000 DP107 (discovered only months before by a team from the Massachusetts Institute of Technology), was a binary system. Observations over eight days last October with the much more sensitive Arecibo telescope clearly established the physical characteristics of DP107’s two asteroids as well as their orbit about each other. The smaller object called the secondary, it was found, is about 300 meters (1,000 feet) in diameter and is orbiting the larger asteroid, the primary, every 42 hours at a distance of 2.6 kilometers (1.6 miles). The two asteroids appear to be locked in synchronous rotation, with the smaller always with the same face oriented to the larger.
Since that observation, says Margot, four more binary NEAs have been discovered, all in Earth-crossing orbits and each with a main asteroid significantly larger than the smaller body. “The primary is rotating much faster than most NEAs in all five binaries that have been discovered,” says Cornell’s Campbell. The Science Express article speculates that the most likely way the binaries are created is by close encounters of asteroids with the inner planets Earth or Mars. Of the five binary NEAs discovered to date, none has an orbit that brings it as close to the sun as Venus or Mercury.
NEAs, basically piles of rubble held together by gravity, are on trajectories that bring them within a few thousand miles of the planets, where tidal forces —- essentially the pull of gravity — can increase the spin rate of the asteroid, causing it to fly apart. The ejected rubble then reforms in orbit around the larger asteroid.
“The asteroid is already rotating very quickly as it approaches the planet. A little extra boost from tidal forces can be enough to exceed its breakup limits, and it sheds mass. This mass can end up forming another object in orbit around the asteroid. Right now this seems the most likely explanation,” says Margot.
There is an important reason for studying binary asteroids, says JPL’s Ostro: their potential for colliding with Earth. Knowing the density of so-called PHAs (for potentially hazardous asteroids), he observes, “is an extremely important input to any mitigation plans.” He says, “Getting NEA densities from radar is dirt cheap compared with getting a density with a spacecraft. Of course, the most important thing to know about any PHA is whether it is two objects or one, and this is why we want to observe these binaries with radar whenever possible.”
Margot notes, “Radar gives us very precise measurements of the size of the objects and their shape. The radar measurements of the distance and velocity of each component allows us to obtain precise information on their orbits. From this we can obtain the mass of each of the objects allowing, for the ?rst time, measurements of NEA densities, a very important indicator of their composition and internal structure.”
Arecibo Observatory is operated by the National Astronomy and Ionosphere Center at Cornell under a cooperative agreement with the NSF. The research was supported by the NSF, with NASA providing additional support for the planetary radar program at Arecibo.
Original Source: Cornell News Release