VOA慢速英語:科學家計劃制作一張銀河系3D地圖
From VOA Learning English, this is Science in theNews. I’m June Simms.
And I’m Jim Tedder. Today on the program, we tellabout developments in space exploration. We tellabout an American decision to extend the life of theInternational Space Station. We also tell about theAmerican space agency’s Mars rover Opportunity andnew findings from the red planet. We have a reportabout what appear to be high energy particles fromoutside our solar system. But first, we report on plansfor an unusual map.
A man-made satellite called Gaia started a long trip latelast year. The satellite was designed to travel morethan a million kilometers from Earth. Scientists are hoping that Gaia will takepictures of our galaxy, the Milky Way. They plan to use the pictures to createthe first three-dimensional -- or 3-D -- map of the Milky Way. It will show theheight, depth and width of stars and other large, recognizable objects.
The satellite weighs two tons. It was launched on a Russian Soyuz rocketlast December from the European Space Agency’s center in French Guiana. Gaia rose quickly and soon began orbiting the Earth. It then deployed a 10-meter-large circular sunshield. The device is keeping instruments on thesatellite -- including two telescopes – cool on the long trip.
The scientists hope to use the telescope to study distant stars. Gaia wasdesigned to be mechanically stable. That is why the satellite has so fewmoving parts. In addition, its temperature must not change very much.
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Andromeda galaxy photo taken by the Hubble Space Telescope. |
Mark McCaughrean is the chief scientist for the Gaia mission. He says theinformation Gaia gathers will help scientists understand how our galaxydeveloped, how it looks today, and how it may change.
“It will measure the positions of a billion stars but also their speeds, theirmotions. And with that we can run a movie of the Milky Way. We can run itforwards, into the future, how the Milky Way will develop by looking at all thestars and how they move. But we can run it backwards as well, and we cansee how the Milky Way actually formed in the first place.”
Gerard F. Gilmore is with the Institute of Astronomy at England’s CambridgeUniversity. He says the 3-D images will one day show half of the Milky Way. He says the map will provide new knowledge about what keeps the galaxytogether.
“And the particular interest that I have in here, locally, is in the nature of darkmatter. What is dark matter made of? Dark matter is most of the weight in the Milky Way. It is dark matter that holds the Milky Way together. If thereweren’t all this dark material, our sun would fly off away from the galaxy. Thewhole galaxy would fall apart.”
Scientists expect the satellite to operate for five years in an area about 1.5million kilometers from Earth. It will take about 70 pictures of each of the onebillion stars in the Milky Way. The mission is expected to cost about $1.3billion.
The United States’ space agency has announced plans to keep theInternational Space Station operating until 2024. The $100 billion spacestation has already been in service for 15 years. It was supposed to haltoperations in 2020.
The space agency and the Obama administration say extending the life of thespace station will help the US and its international partners meet severalgoals. These include scientific research and giving private businesses time tofully take responsibility for transporting shipments and crew to low-Earth orbit.
One of the private companies is Orbital Sciences Corporation. It sent asupply flight to the space station in early January. The space agency retiredthe last of its space shuttles in 2011. Since then, it has been using OrbitalSciences and another company -- SpaceX -- to transport supplies to thespace station. It has also been getting support from Russia. Flight crews arebrought to the space station on Russian Soyuz spacecraft.
More Opportunities for Scientific Study on Mars
The US space agency says its Mars rover vehicle “Opportunity” is still workingmore than 10 years after arriving on the red planet. Opportunity landed onMars on January 24, 2004 -- several weeks after another rover vehicle, called“Spirit.”
NASA, the National Aeronautics and Space Administration, says one ofOpportunity’s six wheels and two instruments stopped working long ago. Butthose are minor problems when you think about how long the project wassupposed to last: just three months. Spirit stopped sending signals in 2010after getting stuck in sand.
Opportunity has travelled about 39 kilometers on the planet’s surface. NASAscientists say the rover continues making new discoveries. It recentlyoverturned a rock, so that its bottom was exposed to the Martian atmospherefor the first time in perhaps billions of years.
Early discoveries by the two rovers showed the planet may have at one timebeen much warmer and wet. And recently, Opportunity found geologicevidence of water in an area called the Endeavour Crater. Scientists believethe discovery could help them find places other than the Earth where simplelife forms could have survived.
New research shows mineral-eating organisms could have lived on Mars. Scientists say this is the best evidence yet that the planet could once havesupported life forms.
Last year, scientists reported evidence of water on Mars. In the latestresearch, the Mars rover vehicle “Curiosity” found two minerals -- iron andsulfur -- in different chemical states at the bottom of a former lake. The findingis important because the different states suggest that electrons could movearound in that environment. Scott McLennan is a professor of geoscience atStony Brook University in New York.
“If you can move electrons around you have basically got food.”
Professor McLennan is part of the Mars rover team that made the discovery.
“In principle, you would have microbes that could eat the rocks and eat theminerals. And that is very common on Earth. They are primitive life forms butthey are very, very well-known and very well-characterized.”
Such life forms are found in dark caves and deep-sea thermal vents on Earth. These areas do not get the sunlight that is the root of all life on our planet’ssurface.
Hap McSween is a planetary science professor at the University ofTennessee. He says recent research papers claimed there could be life onMars. But he says this was the first time he has been persuaded of it.
Professor McSween was not involved in the recent study. He says it is not thefirst time researchers have found water or important minerals on Mars.
“But never the whole package. And this place really does seem to have thewhole package.”
The materials were found near the place where Curiosity landed. The areaappears to have been a lake about four billion years ago. Professor McSweennotes that was around the time life was appearing on Earth.
“It could be that the two planets had emerging but very, very simplified life at the same time. But we are a long way from figuring out that this interestinglake deposit actually has any evidence for life.”
Sensing equipment buried deep in the Antarctic ice has found evidence of highenergy particles from outside our solar system.
IceCube is the name of a device operating in Antarctica. It has more than5,000 light sensors buried as deep as two kilometers below the surface. IceCube has been called, the world’s largest particle detector searching for “neutrinos”.
Neutrinos are unimaginably small particles. They travel from the sun orEarth’s own atmosphere at near light speed. Billions of them pass through usevery second. But these are low energy neutrinos. They are not what interestthe 250 scientists from 11 countries working with information from IceCube.
Francis Halzen is the lead investigator on the project and a physics professorat the University of Wisconsin. He says IceCube is looking in the ice for high-energy neutrinos from outside the solar system.
“What we want to see is a handful of events sent to us by the universe. We’ve finally discovered those.”
When the neutrinos mix with atoms inside the deep ice instrumentss, theysometimes give off small amounts of light. In 2010, scientists discovered twohigh-energy neutrinos. Two years later, they found 26 more -- including themost-energetic neutrinos ever observed.
Nathan Whitehorn is a physicist at the University of Wisconsin. He also isworking on the IceCube project. He says the discovery of the 26 neutrinosafter finding the first two was very important.
“It was almost impossible, without more data and data at lower energies, to besure that these two neutrinos that we found were part of a larger patternindicating an extraterrestrial population, instead of some statistical fluke.”
Neutrinos have almost no mass or weight, and no electric charge. That iswhy the Earth’s magnetic fields have no effect on them. Neutrinos movequickly and in a straight line through the solar system. That movement is verydifferent from electrically-charged cosmic rays. Professor Whitehorn saysthe lack of an electric charge in neutrinos means they can help scientists findwhere cosmic rays came from.
“We expect that anything that is making high-energy cosmic rays -- the mostenergetic phenomenon in the universe -- whatever they are, will makeneutrinos at the same time and if we are able to identify the origin of thesehigh-energy neutrinos, they will provide some very powerful clues about theorigin of the highest-energy cosmic rays.”
Scientists have been attempting to solve this mystery for more than acentury. They hope these extraterrestrial messengers will help them do that.
This Science in the News was written and produced by Christopher Cruise. I’m Jim Tedder.
And I’m June Simms. Join us again next week at this time for more newsabout science on the Voice of America.
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