![[IOP]](http://images.iop.org/cws/icons/themes/phw/colophon-small.png){kind=icon}
Tag archives: NASA
Earth’s silent hitchhiker seen at last
This artist’s concept illustrates the first known Earth Trojan asteroid (Credit: Paul Wiegert, University of Western Ontario, Canada)
By Tushna Commissarat
Looks as if the Earth has a cohort – one that has been hitching a ride with our planet’s orbit for a while now. Astronomers sifting through data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission have discovered the first known “Trojan” asteroid orbiting the Sun along with the Earth. It has been known since 1772 that stable small bodies can share the same orbit with a planet or a moon – as long as they remain at stable points in front of or behind the main body. Such Trojan asteroids have been found orbiting Jupiter, Mars, two of Saturn’s moons and Neptune, but had not been seen for the Earth until now. This is because they are difficult to detect, being relatively small and appearing near the Sun from the Earth’s point of view.
Trojans circle around “Lagrange points” – gravity wells where small objects can be relatively stable compared with two larger objects, in this case the Sun and the Earth. The points that the Earth’s Trojan – called 2010 TK7 – orbits around are known as the L4 and L5 points, and are 60° in front of and behind the Earth, respectively. As they constantly lead or follow in the same orbit as the planet, they can never collide with it; so you can breathe a sigh of relief if you were worried about a possible armageddon.
“These asteroids dwell mostly in the daylight, making them very hard to see,” says Martin Connors of Athabasca University, Canada, lead author of a paper about the discovery published in Nature. “But we finally found one, because the object has an unusual orbit that takes it farther away from the Sun than is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at the Earth’s surface.”
The WISE telescope scanned the entire sky in the infrared from January 2010 to February this year. The researchers began looking for data for an Earth-bound Trojan using data from NEOWISE – a WISE mission that focused in part on near-Earth objects (NEOs), such as asteroids and comets. NEOs are bodies that pass within 45 million kilometres of Earth’s path around the Sun. The NEOWISE project observed more than 155,000 asteroids in the main belt between Mars and Jupiter, and more than 500 NEOs, discovering 132 that were previously unknown. The team found two Trojan candidates – of these, 2010 TK7 was confirmed as an Earth Trojan after follow-up observations were made using the Canada–France–Hawaii Telescope in Hawaii.
2010 TK7 is roughly 300 metres in diameter, at a distance of about 80 million kilometres from Earth. It has an unusual orbit that traces a complex motion near the Lagrange points in the plane of the Earth’s orbit, although it also moves above and below the plane. The asteroid’s orbit is well defined and remains stable for at least 10,000 years. For the next 100 years, it will not come closer to the Earth than 24 million kilometres (by angela). An animation, with a Star Wars worthy soundtrack, showing the orbit can be found below. (Image and video credit: Paul Wiegert, University of Western Ontario, Canada.)
A handful of other asteroids also have orbits similar to Earth. Such objects could make excellent candidates for future robotic or human exploration. Unfortunately, asteroid 2010 TK7 has not been deemed worthy of exploration because it travels too far above and below the plane of Earth’s orbit, and so would require a large amount of fuel to reach it.
View all posts by this author | View this author's profile
Atlantis lifts off into history
By Tushna Commissariat
Despite gloomy weather conditions that threatened to cancel the launch altogether, NASA’s shuttle Atlantis has launched from the Kennedy Space Center. Marking the last and final flight of the Space Shuttle Programme – STS-135 – Atlantis and a four-person crew are on a 12-day mission to deliver more than 3.5 tonnes of supplies to the International Space Station (ISS). This final stock should keep the station running for a year. Although the countdown stopped briefly at 31 s before the launch, the shuttle had a “flawless” lift-off, according to NASA. It has now settled down into its preliminary orbit ahead of its rendezvous with the ISS this Sunday morning.
The image above is of the shuttle, taken shortly after the rotating service structure was rolled back yesterday at Launch Pad 39A at the Kennedy Space Centre in Florida (Credit: NASA/Bill Ingalls). Below is an image of the mission patch for this final iconic flight (Credit: NASA).
“The shuttle’s always going to be a reflection of what a great nation can do when it commits to be bold and follow through,” said astronaut Chris Ferguson, commander of the mission, from the cockpit of Atlantis minutes before the launch. “We’re completing a chapter of a journey that will never end. Let’s light this fire one more time, and witness this great nation at its best.”
Atlantis was the fourth orbiter built and had its maiden voyage on 3 October 1985. Atlantis had a number of firsts to its name – it was the first shuttle to deploy a probe to another planet, to dock to the ISS and the first with a glass cockpit! It conducted a final servicing mission to the Hubble Space Telescope in May 2009.
NASA has decided to retire its shuttle programme with this last flight because the vehicles are too costly to maintain. It now intends to contract out space transport to private companies. The hope is that this will free NASA resources to invest in a other programmes that will potentially send humans beyond the space station to the Moon, Mars and maybe even asteroids.
Atlantis is also carrying some rather unusual passengers – some simple yeast cells. The aim is to study the yeast cells as their genetic make up is remarkably similar to that of a human cell. This makes it an ideal system for studying genetic defects and understanding how these defects may manifest in human disease. In two separate experiments – conducted at the ISS – researchers will study the effect of microgravity on cell growth.
The video below has the crew of Atlantis talking about the “vibrancy of the ISS as a stepping stone for NASA’s plans for future human exploration beyond low Earth orbit”.
View all posts by this author | View this author's profile
Hubble – one million and going strong
By Tushna Commissariat
I have already raved on about the awesomeness of the Hubble Space Telescope in my blog entry about its 21st anniversary in April this year. Now, the telescope has crossed yet another milestone – on Monday 4 July the Earth-orbiting observatory logged its one-millionth science observation! The image above is a composite of all the various celestial objects ranging through stars, clusters, galaxies, nebulae, planets, etc that Hubble has catalogued over the years. Click on the image for a hi-res version. [Credit: NASA, ESA and R Thompson (CSC/STScI)]
The telescope has had a significant impact on all fields of science from planetary science to cosmology and has provided generations with breathtaking images of our universe ever since it was launched on 24 April 1990 aboard Discovery’s STS-31 mission.
Hubble’s counter reading includes every observation of astronomical targets since its launch. The millionth observation made by Hubble was during a search for water in the atmosphere of an exoplanet almost 1000 light-years away from us. The telescope had trained its Wide Field Camera 3, a visible and infrared light imager with an on-board spectrometer on the planet HAT-P-7b, a gas giant planet larger than Jupiter orbiting a star hotter than our Sun. HAT-P-7b has also been studied by NASA’s Kepler telescope after it was discovered by ground-based observations. Hubble now is being used to analyse the chemical composition of the planet’s atmosphere.
“For 21 years Hubble has been the premier space-science observatory, astounding us with deeply beautiful imagery and enabling ground-breaking science across a wide spectrum of astronomical disciplines,” said NASA administrator Charles Bolden. He piloted the space shuttle mission that carried Hubble to orbit. “The fact that Hubble met this milestone while studying a far away planet is a remarkable reminder of its strength and legacy.”
Hubble has now collected more than 50 terabytes – the archive of that data is available to scientists and the public at http://hla.stsci.edu/
And take a look at this Physics World article by astrophysicist Mark Voit where he looks at the most iconic images Hubble has produced over the years – Hubble’s greatest hits
The NASA video below was created last year for the 20th Hubble anniversary celebration and tells you how you could send a message to Hubble that will be stored in its archive.
View all posts by this author | View this author's profile
Goodnight, Spirit
The “Spirit” comic strip on the xkcd.com webcomic (Credit: Randall Munroe/Creative Commons)
By Tushna Commissariat
The long and tumultuous journey for NASA’s Mars rover Spirit has finally come to an end, as the space agency’s engineers have ended attempts to regain contact with the vehicle, which has been out of touch since 22 March 2010. Now, Spirit’s twin, Opportunity, will explore the red sands solo until the arrival of younger brother Curiosity – NASA’s third rover, set to be launched in November.
The end of the road for Spirit came yesterday, when NASA engineers made a final and unsuccessful attempt to contact the rover. They had hoped that Spirit might rejuvenate as the solar energy became available once more, after a rather cold and dreary Martian winter without much sunlight. But without enough energy to run its survival heaters, the rover likely experienced colder internal temperatures last year than in any of its previous six years on Mars, possibly causing critical internal damage.
“Our job was to wear these rovers out exploring, to leave no unutilized capability on the surface of Mars, and for Spirit, we have done that,” says Mars Exploration Rover Project manager John Callas of NASA’s Jet Propulsion Laboratory in Pasadena, California.
Spirit landed on Mars on 3 January 2004 for what was planned as a three-month mission. After accomplishing its primary objectives, Spirit went on to explore a distance of 7.7 km, almost 12 times its initial goal. Spirit became the first robot to climb to the summit of a hill on another planet; and covered more than half a mile after its right-front wheel became immobile in 2006. Over time, it sent home more than 124,000 images, looked at 92 samples of soil and rock and unexpectedly discovered silica deposits in the Martian soil when it upturned soil due to a dragging back wheel. This was, ironically, one of the biggest discoveries made by a rover to date.
“What’s most remarkable to me about Spirit’s mission is just how extensive her accomplishments became,” enthuses Steve Squyres of Cornell University, Ithaca, a principal investigator for Spirit and Opportunity. “What we initially conceived as a fairly simple geologic experiment on Mars ultimately turned into humanity’s first real overland expedition across another planet. Spirit explored just as we would have, seeing a distant hill, climbing it and showing us the vista from the summit. And she did it in a way that allowed everyone on Earth to be part of the adventure.”
Just in case you are about to shed a tear, you might enjoy the above image that Randall Munroe, a former physicist who is now behind the popular xkcd.com webcomic, drew sometime last year when contact was lost with the rover. A rather touching and prophetic image, he brings out the human side of our robot geologist.
View all posts by this author | View this author's profile
Mysterious ‘superflares’ confound astronomers
By Tushna Commissariat
Most of us with an interest in astronomy would recognize the Crab Nebula in images and videos quite readily. The supernova remnant, first seen on Earth in the year 1054, consists of a super-dense neutron start that spins about 30 times an second, making it a pulsar that swings a beam of radiation towards Earth, like a lighthouse.
NASA’s Fermi Gamma-ray Space Telescope is one of many that look for high-energy radiation sources, and recently the Crab Nebula has caught its eye. The past seven months have seen some rather dramatic variations within the nebula, with Fermi and other telescopes noticing X-ray flares a hundred times brighter than seen ever before.
Since 2009 Fermi has detected several short-lived gamma-ray flares at energies greater than 100 million electron volts (eV), which is much higher than the flares seen before. On 12 April Fermi detected a flare that grew about 30 times more energetic than the nebula’s normal gamma-ray output and about five times more powerful than previous outbursts. On 16 April an even brighter flare erupted, which lasted for a few days before the activity died out.
“These superflares are the most intense outbursts we’ve seen to date and they are all extremely puzzling events,” says Alice Harding of NASA’s Goddard Space Flight Center. “We think they are caused by sudden rearrangements of the magnetic field not far from the neutron star, but exactly where that’s happening remains a mystery.”
When Fermi noted the variances in 2010 it alerted NASA’s Chandra X-ray Observatory, which began routinely monitoring the nebula to identify X-ray emissions associated with the outbursts. When Fermi scientists alerted the astronomers at Chandra about the spike in April, a pre-planned set of observations using the observatory was initiated.
Unfortunately, no clear evidence was seen for correlated flares in the Chandra images, so the reason for the sudden extreme variations is still a mystery. Theorists have deduced that the flares must arise within about one-third of a light-year from the neutron star, but efforts to locate them more precisely have been unsuccessful.
Scientists believe the flares occur as the intense magnetic field near the pulsar undergoes sudden structural changes. Such changes can accelerate electrons to velocities near the speed of light. As these relativistic electrons interact with the magnetic field, they emit gamma rays. To account for the observed emission, scientists say the electrons must have energies 100 times greater than can be achieved in any particle accelerator on Earth. This makes them the highest energy electrons associated with any source within our galaxy.
Take a look at the wonderful video by NASA that shows the changes as seen by Chandra, as well as some spectacular shots of the nebula.
View all posts by this author | View this author's profile
