[ti:Scientists Explain Unusual Motion of Comet from Another Solar System]
[by:www.21voa.com]
[00:00.00]更多听力请访问21VOA.COM
[00:00.04]‘Oumuamua is the first object
[00:04.84]found visiting our solar system
[00:08.56]from another solar system.
[00:12.76]It is a comet
[00:14.56]that was first discovered in 2017.
[00:20.08]Scientists observed the comet accelerate
[00:24.64]in an unusual way
[00:27.52]as it moved away from the sun.
[00:31.96]Scientists have offered different theories
[00:36.44]for this unexpected behavior.
[00:40.72]Among the theories is the idea that the object
[00:45.44]is an alien spaceship.
[00:49.36]But a new study has offered
[00:52.40]a clearer explanation –
[00:55.28]that ‘Oumuamua's increase in speed
[01:00.20]was caused by the release of hydrogen gas
[01:04.96]as the comet warmed up in the sunlight.
[01:10.08]‘Oumuamua lacks the tail of gas
[01:14.48]and particles common in many comets.
[01:20.16]It has been described
[01:22.28]as being shaped like a tube
[01:24.68]but now is thought to be thin,
[01:27.96]round, and flat.
[01:30.88]It is smaller than first estimated.
[01:34.64]It is now thought to be around
[01:38.20]115 meters by 111 meters,
[01:44.56]with a thickness of about 19 meters.
[01:49.96]Researchers said it appears that
[01:53.40]‘Oumuamua was born like many other comets
[01:58.92]as what is called a planetesimal.
[02:04.08]A planetesimal is a small object formed
[02:09.20]in the early period of planet formation.
[02:14.80]Researchers described ‘Oumuamua
[02:19.04]as a large, icy space rock.
[02:23.44]The comet then somehow left
[02:26.20]the solar system where it formed.
[02:30.68]Scientists said the comet's chemistry changed
[02:35.72]as it received high-energy radiation
[02:40.20]traveling through interstellar space.
[02:45.24]The radiation changed
[02:47.68]some of the comet's ice
[02:50.12]into hydrogen gas
[02:52.64]that became trapped.
[02:55.88]‘Oumuamua then warmed up
[02:59.40]as it passed through our inner solar system.
[03:04.84]The heating caused the comet's ice structure
[03:09.04]to release the trapped hydrogen gas.
[03:13.80]That accelerated ‘Oumuamua
[03:17.52]as it headed away from the sun.
[03:21.76]The release of this hydrogen
[03:24.64]in a process called outgassing
[03:28.00]would not cause an observable tail.
[03:32.68]Jenny Bergner is a University of California,
[03:37.68]Berkeley astrochemist.
[03:41.92]She is the lead writer of the research
[03:45.72]published recently in Nature.
[03:50.36]She said the important finding
[03:53.56]is that ‘Oumuamua
[03:56.36]might have started as an icy planetesimal
[04:01.64]with a lot of water,
[04:03.96]similar to comets in our own solar system.
[04:09.44]She added that this model
[04:12.16]can explain the strange behavior
[04:15.60]of ‘Oumuamua without needing
[04:19.64]to use unusual physics or chemistry.
[04:24.56]Darryl Seligman of Cornell University
[04:29.16]also helped write the study.
[04:33.32]He said, "The simplest explanation,
[04:37.40]and exactly what we would expect
[04:40.72]for an interstellar comet,
[04:43.24]fits all of the data with no fine-tuning."
[04:48.88]The name ‘Oumuamua
[04:51.56]comes from the Hawaiian language
[04:54.96]and means a messenger
[04:57.76]arriving from a great distance.
[05:02.56]It was first discovered
[05:05.28]by the University of Hawaii's
[05:09.08]Pan-STARRS1 telescope.
[05:13.20]Bergner said,
[05:14.68]"We don't know its place of origin
[05:18.48]but it was probably traveling through
[05:22.44]interstellar space
[05:24.68]for less than 100 million years.
[05:29.44]It had a reddish color
[05:31.88]consistent with the colors
[05:34.20]of many small bodies in the solar system.
[05:39.36]It is currently past Neptune
[05:42.56]on its way out of the solar system."
[05:47.04]A second interstellar object
[05:49.88]was discovered visiting our solar system
[05:54.36]in 2019.
[05:57.52]It is a comet called 2I/Borisov.
[06:03.16]Its behavior has been more like a usual comet.
[06:08.72]These alien visitors
[06:11.00]may be more common
[06:13.20]than had been thought.
[06:16.20]The researchers said one to two
[06:20.16]interstellar objects might be discovered
[06:24.28]every year in our solar system
[06:27.28]once a new astronomy center in Chile
[06:32.04]begins operations as planned next year.
[06:37.36]I'm Gregory Stachel. 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
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