[ti:NASA Shares First Evidence of Planet Outside Our Galaxy]
[by:www.21voa.com]
[00:00.00]更多听力请访问21VOA.COM
[00:00.04]Astronomers say they have found evidence for the first time
[00:05.88]of a planet orbiting a star outside our Milky Way galaxy.
[00:13.64]The evidence was observed by a telescope operated
[00:18.32]by the American space agency NASA.
[00:22.52]It is called the Chandra X-ray Observatory.
[00:27.56]NASA says the orbiting observatory
[00:31.48]is the world's most powerful X-ray telescope.
[00:37.00]NASA recently announced that the observatory
[00:41.08]might have discovered a new planet
[00:44.32]in the galaxy known as Messier 51 or M51.
[00:51.64]The galaxy is popularly known as the "Whirlpool" galaxy.
[00:58.44]The research recently appeared
[01:01.12]in the publication Nature Astronomy.
[01:05.48]The possible planet is considered an exoplanet.
[01:10.76]These are planets that orbit a star
[01:14.40]outside of our own solar system.
[01:18.80]NASA says that so far, more than 4,500 exoplanets
[01:25.96]have been discovered and are considered "confirmed."
[01:31.36]Thousands of other "candidate" exoplanets
[01:35.04]have been detected, but require additional study.
[01:39.92]But all of these have been observed in the Milky Way galaxy.
[01:46.00]And NASA says almost all of them
[01:49.60]are "less than about 3,000 light-years from Earth."
[01:54.00]Scientists estimate that an exoplanet in the M51 galaxy
[02:01.12]would be much farther, about 28 million light-years away.
[02:08.24]Exoplanets are hard for telescopes to identify.
[02:13.24]This is because the bright light of the stars they orbit can hide them.
[02:20.60]The identification process involves searching
[02:24.52]for drops in the light levels of stars.
[02:28.64]Such drops could be caused by a planet
[02:32.60]passing in front of a star.
[02:36.04]This method has been used in past observations
[02:40.52]by NASA telescopes to confirm the presence of planets
[02:45.76]crossing in front of stars.
[02:48.96]These movements -- of planets partly blocking light
[02:53.32]from stars -- are called "transits."
[02:57.72]NASA's latest finding is based on a transit
[03:02.08]detected by the Chandra X-ray Observatory.
[03:07.04]But unlike other NASA telescopes
[03:10.32]which search for drops in observable light,
[03:13.96]Chandra is designed to detect X-rays.
[03:19.00]The observatory "searched for drops
[03:22.32]in the brightness of X-rays received
[03:25.88]from X-ray bright binaries," NASA said in a statement.
[03:31.80]These binaries are defined as bright systems
[03:36.44]that usually contain a neutron star or black hole
[03:41.52]pulling in gas from a closely orbiting star.
[03:46.60]A neutron star is the unimaginably dense result
[03:51.44]of a supergiant star that has collapsed on itself.
[03:57.68]The researchers said the activity of binaries
[04:02.20]causes the material near the neutron star or black hole
[04:07.20]to become superheated and glow in X-rays.
[04:13.08]However, the area producing the X-rays is small.
[04:17.92]It is so small that a planet passing in front of it
[04:22.00]could block most or all the X-rays, they added.
[04:27.76]This method could permit exoplanets
[04:31.28]"to be detected at much greater distances"
[04:35.12]than other light-searching systems that depend
[04:39.32]on optical telescopes, the NASA statement said.
[04:43.92]Rosanne Di Stefano is an astrophysicist
[04:49.28]at the Center for Astrophysics, Harvard & Smithsonian
[04:54.44]in Cambridge, Massachusetts.
[04:57.68]She said in a statement that the research team
[05:01.84]is seeking "to open up a whole new arena
[05:06.00]for finding other worlds by searching
[05:09.56]for planet candidates at X-ray wavelengths."
[05:14.84]Such methods could be used in the future
[05:18.52]to discover other new planets
[05:21.16]in distant galaxies, Di Stefano added.
[05:26.12]The researchers say more data will be needed
[05:30.36]to confirm the observation as an actual "extragalactic exoplanet."
[05:37.92]They say one problem is that the planet candidate
[05:42.04]has a large orbit.
[05:44.20]This means it is not expected
[05:47.56]to pass in front of its binary partner for at least 70 years,
[05:53.44]blocking any confirmation attempts anytime soon.
[05:59.28]However, one co-writer of the study
[06:02.76]said the team is very confident with its findings.
[06:07.96]"We know we are making an exciting and bold claim,
[06:12.40]so we expect that other astronomers will look at it very carefully,"
[06:18.24]said Julia Berndtsson of Princeton University in New Jersey.
[06:24.64]She added: "We think we have a strong argument,
[06:28.88]and this process is how science works."
[06:33.00]I'm Bryan Lynn. 更多听力请访问21VOA.COM
END OF TRACK. "END OF TRACK." The two men bowed. "Whoever was that person you were talking to?" she enquired, as soon as they stood together. The took of triumph faded from her eyes, she had grown worn and weary. The roses were wilting on the walls, the lights were mostly down now. Hetty, looking in to see if anything was wanted, found herself driven away almost fiercely. I only saw Master Jervie once when he called at tea time, The year 1747 was opened by measures of restriction. The House of Lords, offended at the publication of the proceedings of the trial of Lord Lovat, summoned the parties to their bar, committed them to prison, and refused to liberate them till they had pledged themselves not to repeat the offence, and had paid very heavy fees. The consequence of this was that the transactions of the Peers were almost entirely suppressed for nearly thirty years from this time, and we draw our knowledge of them chiefly from notes taken by Horace Walpole and Lord Chancellor Hardwicke. What is still more remarkable, the reports of the House of Commons, being taken by stealth, and on the merest sufferance, are of the most meagre kind, sometimes altogether wanting, and the speeches are given uniformly under fictitious names; for to have attributed to Pitt or Pelham their[112] speeches by name would have brought down on the printers the summary vengeance of the House. Many of the members complained bitterly of this breach of the privileges of Parliament, and of "being put into print by low fellows"; but Pelham had the sense to tolerate them, saying, "Let them alone; they make better speeches for us than we can make for ourselves." Altogether, the House of Commons exhibited the most deplorable aspect that can be conceived. The Ministry had pursued Walpole's system of buying up opponents by place, or pension, or secret service money, till there was no life left in the House. Ministers passed their measures without troubling themselves to say much in their behalf; and the opposition dwindled to Sir John Hinde Cotton, now dismissed from office, and a feeble remnant of Jacobites raised but miserable resistance. In vain the Prince of Wales and the secret instigations of Bolingbroke and Doddington stimulated the spirit of discontent; both Houses had degenerated into most silent and insignificant arenas of very commonplace business. "It certainly will be. Miss Widgeon," answered Maria, with strictly "company manners." "One who has never had a brother exposed to the constant dangers of army life can hardly understand how glad we all feel to have Si snatched from the very jaws of death and brung back to us." "Just plug at 'em as you would at a crow, and then go on your way whistlin'?" persisted Harry. "Hurroo!" echoed Hennessey; "that's the ticket." "Come forward, keeper," continued the baron, "and state how these arrows came into your hands!" "Yes." HoMEJULIA京香2018下载
ENTER NUMBET 0015baxiuk.com.cn
www.yzkqfd.com.cn
www.bbssq.net.cn
www.waihuitouzi.net.cn
xmhd888.com.cn
www.btcoin.net.cn
www.8686688.com.cn
1token.com.cn
www.sx12530.com.cn
heqiao.net.cn