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A Search for Exozodiacal Dust and Faint Companions Near Sirius,Procyon,and Altair with the NICMOS Coronagraph 1Marc J.Kuchner Palomar Observatory,California Institute of Technology,Pasadena,CA 91125Michael E.Brown 2Division of Geological and Planetary Sciences,California Institute of Technology,Pasadena,CA 91125ABSTRACT We observed Sirius,Altair,and Procyon with the NICMOS Coronagraph on the Hubble Space Telescope to look for scattered light from exo-zodiacal dust and faint companions within 10AU from these stars.We did not achieve enough dynamic range to surpass the upper limits set by IRAS on the amount of exo-zodiacal dust in these systems,but we did set strong upper limits on the presence of nearby late-type and sub-stellar companions.Subject headings:binaries:visual —circumstellar matter —interplanetary medium —stars:individual (Altair,Procyon,Sirius)—stars:low mass,brown dwarfs 1.Introduction
Several main sequence stars are close enough that a large telescope operating at the di?raction limit can resolve the terrestrial planet-forming region within 10AU from the star (Kuchner,Brown &Koresko 1998).We used the NICMOS coronagraph to image three of the nearest main-sequence stars in the near-infrared to look for circumstellar material—exozodiacal dust and faint companions—in this relatively uncharted circumstellar region.
Any dust orbiting close to one of our targets must have been generated recently by some population of larger bodies,since dust near a star quickly spirals into the star due to Poynting-Robertson drag(Robertson1937).Ten micron diameter dust3AU from a G star spirals into the star on time scales of～105years;for brighter stars,this timescale is shorter.Around the sun,zodiacal dust forms when asteroids collide and when comets outgass;a search for exozodiacal dust is therefore implicitly a search for extra-solar asteroid or comet-like bodies that make dust.
Several disks around nearby main-sequence stars appear to have exozodiacal components.Some,such as the disk associated with Beta-Pictoris,reveal their warm dust as a silicate emission feature at10microns(Telesco&Knacke1991).Others,like the disk around HR4796,show resolved emission at10microns that is interpreted as exozodiacal (Koerner et al.1998).Dust clouds like these,which have～1000times as much warm dust as our sun,emit thermal radiation substantially in excess of the stellar photospheric emission,and can often be detected photometrically by studying the spectral energy distribution of the star in the mid-infrared.However,many less massive exozodiacal clouds may never be detectable photometrically because no stellar spectrum is known to better than～3%in the mid-infrared(Cohen et al.1996).We have begun to search for disk that are too faint to be detected photometrically by spatially resolving the critical regions less than10AU from nearby stars.
Coronagraphic images can also reveal faint companions to nearby stars.Such companions can go undetected by radial velocity surveys because of their small masses
or long orbital periods.Siruis and Procyon both have white dwarf companions whose orbits are well studied,but analyses of the orbital motion in these systems leave room for additional low mass companions.
The Sirius system in particular,so prominent in the night sky,has spurred much debate in the last century over its properties.Three analyses of the proper motion of Sirius have suggested that there may be a perturbation in the orbit of Sirius B with a～6year period(Volet1932;Walbaum&Duvent1983;Benest&Duvent1995).These analyses do not indicate whether the perturbing body orbits Sirius A or B,and dynamical simulations indicate that stable orbits exist around both Sirius A and B at circumstellar distances up to more than half the binary’s periastron separation(Benest1989).If such a companion were in a simple face-on circular orbit it would appear at a separation of4.2AU(1.6arcsec)from Sirius A or a separation of3.3AU(1.3arcsec)from Sirius B assuming that the masses for Sirius A and B a are2.1and1.04M⊙respectively(Gatewood&Gatewood1978).Benest &Duvent(1995)do not derive a mass for the hypothetical companion from observations of the system,but they estimate that a perturber much more massive than0.05M⊙would
rapidly destroy the binary.
Perhaps the most interesting debate about Sirius is whether or not the system appeared red to ancient observers～2000years ago.Babylonian,Graeco-Roman and Chinese texts from this time period have separately been interpreted to say that Sirius was a red star (Brecher1979;Schlosser&Bergman1985,Bonnet-Bidaud&Gry1991).Tang(1986),van Gent(1984)and McCluskey(1987)have attacked some of these reports,claiming that they represent mistranslations or misidenti?cations of the star.However,if the Sirius system did indeed appear red,the existence of a third star in the group interacting periodically with Sirius A could explain the e?ect(Bonnet-Bidaud1991).
The low mass companions(<0.1M⊙)that we could hope to detect with NICMOS are late-type stars or warm brown dwarfs,shining with their own thermal power in the near-infrared.Schroeder and Golimowski(1996)recently imaged Sirius,Procyon and Altair at visible wavelengths with the Planetary Camera on HST in a search for faint companions. Our observations are more sensitive to late-type companions because of the high dynamic range of the NICMOS coronagraph,and because these objects are brighter in the infrared than the optical.
2.Observations
We observed our target stars with the NICMOS Camera2coronagraph on?ve dates during1999October.We used the F110?lter,the bluest available near-infrared?lter,with an e?ective wavelength of1.104microns,to take advantage of the higher dynamic range the coronagraph has at shorter wavelengths.We took images of Sirius and Procyon at two di?erent orientations,rolling the telescope about the axis to the star by15?between them. When we searched for faint companions in the images,we subtracted the images taken at one roll angle from the images taken at the other angle to cancel the light in the wings from the image of the occulted star.We planned to image Altair at a second roll angle,but on our second visit to the star the telescope’s Fine Guidance Sensors failed to achieve?ne lock on the guide star due to“walkdown”failure.
At each roll angle we took50short exposures in ACCUM mode,lasting0.6seconds each,and we co-added them,for total integration times of30seconds.Even though we used the shortest available exposure times,our images saturated interior to about1.9 arcseconds for Sirius,1.4arcseconds for Procyon,and0.7arcseconds for Altair.The actual coronagraphic hole is only0.3arcseconds in radius.Table1summarizes the timing and orientations of our observations.
Figure1shows an image of Sirius taken at one roll angle.The white dwarf Sirius B appears to the left of Sirius A,at a separation of3.79arcseconds.We derived photometry of Sirius B at1.1microns from the roll subtracted image of Sirius using a prescription from Rieke(1999).We measured the?ux in circular apertures with radii7.5pixels around the positive and negative images and multiplied the?ux in those regions by an aperture correction of1.110to extrapolate to the total?ux.Then we used a factor of1.996×10?6 Jy/ADU/Sec to convert from ADU to Janskys.In this manner,we measured the?ux in Sirius B to be0.503±0.15Jy.Procyon also has a white dwarf companion,Procyon B, that has been previously detected by HST(Provencal et al.1997).It is not visible in our images,because it is currently at a separation of～5arcseconds from Procyon A.
3.Exozodiacal Dust
We compared our observations of Sirius,Procyon and Altair to a simple model for what our zodiacal cloud would look like if it were placed aound these stars.Kelsall et al. (1998)?t an88-parameter model of the zodiacal cloud to the maps of the infrared sky made by the Di?use Infrared Background Experiment(DIRBE)aboard the Cosmic Background Explorer(COBE)satellite.We used the smooth component of this model,which has a face-on optical depth of7.11×10?8(r/1AU)?0.34,and extrapolated it to an outer radius of10AU.We used a scattering phase function consisting of a linear combination of three Henyey-Greenstein functions that Hong(1985)?t to visible light observations of the zodiacal cloud with the Helios Satellite,and we assumed an albedo of0.2,from the Kelsall et al.(1998)?t to the1.25micron DIRBE maps.
For this part of our search,we could not use roll-subtraction to cancel the light in the images of our target stars,because this approach would also cancel most of the light from an exozodiacal disk,even if the disk were edge-on.Instead we subtracted images of Altair from the images of Procyon and Sirius,with the assumption that all three of our stars would not have identical circumstellar structures.We used the IDP3data analysis software (Lytle et al.1999)to perform sub-pixel shifts on the images of Altair before we subtracted them from our images of Sirius and Procyon to compensate for the slightly di?erent relative alignments of the three stars and the coronagraphic hole.
Figures2a and3a show our images of Sirius and Procyon minus our image of Altair. Software masks hide the regions where the images are saturated and the four main
di?raction spikes.The bright horn just above the masked area in the Procyon image is a well known NICMOS artifact.
Figures2b and3b show the same images plus synthesized images of exozodiacal clouds seen in scattered light.The models are brightest immmediately to the left and the right of the circular masked regions.The symmetry planes of the model disks are inclined30?from edge-on.The dust densities in these have been enhanced to>105×solar levels so they are marginally discernible from the residuals from the PSF subtraction.We used these models for the sake of comparison with the solar zodiacal cloud;real disks with this much dust would be severely collisionally depleted in their centers,unlike the solar cloud.Despite the high dynamic range of the NICMOS coronagraph and our e?orts at PSF calibration,we were not able to improve upon photometric detection limits for exozodiacal dust around these stars;if the stars actually had this much circumstellar dust,the thermal emission from the dust would have been seen as a photometric excess by IRAS.
Our study demonstrates the di?culty of detecting exozodiacal dust in the presence of scattered light from a bright star in a single-dish telescope.Faint companions can be di?erentiated from the wings of the telescope PSF by techniques like roll subtraction, but if exozodiacal clouds resemble the solar zodiacal cloud,light from these clouds will resemble the PSF wings.Even though coronagraphs can suppress the PSF wings from an on-axis source by as much as an order of magnitude,the dynamic range obtainable with a coronagraph on a large,di?raction-limited telescope in the near-infrared is far from that required to probe dust levels comparable to the solar cloud.
4.Faint Companions
For our faint companion search we created roll-subtracted images of Sirius and Procyon using the IDP3software.To?nd the detection limits for faint companions among the non-gaussian PSF residuals,we tested our abilities to see arti?cial stars added to our images.We examined roughly350copies of the PSF-subtracted images of each of Sirius, Procyon and Altair with help from a few of our patient colleagues.To?ve-sixths of the images,we added images of arti?cial stars,copied from our image of Sirius B,at random positions and magnitudes that were unknown to the examiner.The other images were left unaltered and mixed with the images that contained arti?cial stars.The examiners were shown each image one at at time,and asked whether they could say con?dently that the image they were shown had an arti?cial star.Only2%of the time did an examiner claim to see an arti?cial star when none had been added to the image.We quote as our detection limit the threshold for?nding90%of the arti?cial companions;that is,the examiners reported90%of the arti?cial companions brighter than our detection limit at a given separation.Figure4shows these detection limits.For comparison,we plot the expected
magnitudes of two kinds of possible companions to these objects:an L0dwarf like2MASP J0345432+254023(Kirkpatrick et al.1999)and a cool brown dwarf,Gl229B(Matthews et al.1996).
Our apparent detection limits for Procyon are somewhat better than our detection limits for Sirius because Procyon is almost a magnitude fainter in the the near infrared; the two sets of observations yielded about the same dynamic range.Although Altair is fainter than Procyon,our absolute detection limits for faint companions to Altair are not much better than our detection limits for companions around Procyon because we have only exposures at only one roll angle for Altair.Based on?gure4,we can rule out the existence of M dwarf companions farther than1.4arcseconds from Altair,1.6arcseconds from Procyon and1.8arcsecons from Sirius at greater than the90%con?dence level.It should be noted,however,that the coronagraph hole is only3.5arcseconds from the edge of the chip,and that arti?cial faint companions that were behind one of the four main
di?ration spikes at one roll angle were harder to detect than arti?cial companions at other position angles;?gure4is averaged over position angle.If we compare our upper limits to the J magnitude of T Dwarf Gl229B(Matthews et al.1996),we?nd that we can rule out dwarfs hotter than this object—including all L dwarfs—farther than2.3arcseconds from Procyon and～3.0arcseconds from Sirius and Altair.For comparison,note that Gl229B was discovered7.7arcseconds from a M1V star with an intrinsic luminosity5magnitudes fainter than Sirius in the J band(Nakajima et al.1995).
We do not see any evidence for previously undetected faint companions in our images. If there were a low-mass companion orbiting Sirius at4.2AU we could not detect it because it would lie in the saturated parts of our images.However,we did survey a large fraction of the space where a companion orbiting Sirius B might be found,and we could have detected a brown dwarf like Gl229B throughout most of this zone.If there is a third object in the Sirius system,and it orbits Sirius B with a6year orbit,it is probably fainter than a brown dwarf.
We thank Glen Schneider and Aaron Evans for help with the data reduction,and Edo Berger,John Carpenter,Micol Christopher,Ulyana Dyudina,David Frayer,Roy Gal, Pensri Ho,Matthew Hunt,Shardha Jogee,Olga Kuchner,Charlie Qi,Michael Santos,Alice Shapley and David Vakil for searching for arti?cial stars in our data.
This research made use of the Simbad database,operated at the Centre de Donnees de Strasbourg(CDS),Strasbourg,France.
Support for this work was provided by NASA through grant number GO-07441.01-96A from the Space Telescope Science Institute,which is operated by AURA,Inc.,under NASA
contract NAS5-26555.
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Fig. 1.—A coronagraphic image of the Sirius system.The white dwarf Sirius B,appears to the left of the residual light from Sirius A.Even though we used the shortest available exposure time,the region<1.9arcsec from Sirius A is saturated.
Fig.2.—a)An image of Sirius made using our coronagraphic image of Altair to cancel the wings of the occulted PSF.The saturated regions of the image are hiden with a software mask.b)The same image plus a model of the scattered light from an exozodiacal cloud similar to the solar zodiacal cloud but2.5×105times as bright.
Fig.3.—a)An image of Procyon using Altair as a PSF calibrator.b)The same image plus a model of the scattered light for an exo-zodiacal cloud7×105times as bright as our own zodiacal cloud.
Fig.4.—Detection limits for faint companions around our three target stars as a function of separation from the stars.The magnitudes of some representative cool objects,GL229B and an L0dwarf,are shown for comparison.
Table1.Observations
Target Spectral Type Distance(pc)a J b UT Date Orientation
a From the Hipparcos Catalogue(Perryman et al.1997)
b From the SIMBAD online database
AN EXCITING JOB I have the greatest job in the world. I travel to unusual places and work alongside people from all over the world. Sometimes working outdoors, sometimes in an office, sometimes using scientific equipment and sometimes meeting local people and tourists, I am never bored. Although my job is occasionally dangerous, I don't mind because danger excites me and makes me feel alive. However, the most important thing about my job is that I help protect ordinary people from one of the most powerful forces on earth - the volcano. I was appointed as a volcanologist working for the Hawaiian V olcano Observatory (HVO) twenty years ago. My job is collecting information for a database about Mount Kilauea, which is one of the most active volcanoes in Hawaii. Having collected and evaluated the information, I help other scientists to predict where lava from the volcano will flow next and how fast. Our work has saved many lives because people in the path of the lava can be warned to leave their houses. Unfortunately, we cannot move their homes out of the way, and many houses have been covered with lava or burned to the ground. When boiling rock erupts from a volcano and crashes back to earth, it causes less damage than you might imagine. This is because no one lives near the top of Mount Kilauea, where the rocks fall. The lava that flows slowly like a wave down the mountain causes far more damage because it
八年级下学期全部长篇课文 Unit 1 3a P6 In ten years , I think I'll be a reporter . I'll live in Shanghai, because I went to Shanfhai last year and fell in love with it. I think it's really a beautiful city . As a reporter, I think I will meet lots of interesting people. I think I'll live in an apartment with my best friends, because I don' like living alone. I'll have pets. I can't have an pets now because my mother hates them, and our apartment is too small . So in ten yers I'll have mny different pets. I might even keep a pet parrot!I'll probably go skating and swimming every day. During the week I'll look smart, and probably will wear a suit. On the weekend , I'll be able to dress more casully. I think I'll go to Hong Kong vacation , and one day I might even visit Australia. P8 Do you think you will have your own robot In some science fiction movies, people in the future have their own robots. These robots are just like humans. They help with the housework and do most unpleasant jobs. Some scientists believe that there will be such robots in the future. However, they agree it may take hundreds of years. Scientist ae now trying to make robots look like people and do the same things as us. Janpanese companies have already made robts walk and dance. This kond of roots will also be fun to watch. But robot scientist James White disagrees. He thinks that it will be difficult fo a robot to do the same rhings as a person. For example, it's easy for a child to wake up and know where he or she is. Mr White thinks that robots won't be able to do this. But other scientists disagree. They think thast robots will be able t walk to people in 25 to 50tars. Robots scientists are not just trying to make robots look like people . For example, there are already robots working in factories . These robots look more like huge arms. They do simple jobs over and over again. People would not like to do such as jobs and would get bored. But robots will never bored. In the futhre, there will be more robots everwhere, and humans will have less work to do. New robots will have different shapes. Some will look like humans, and others might look like snakes. After an earthquake, a snake robot could help look for people under buildings. That may not seem possibe now, but computers, space rockets and even electric toothbrushes seemed
高中英语选修 6 Unit 1 A SHORT HISTORY OF WESTERN PAINTING Art is influenced by the customs and faith of a people. Styles in Western art have changed many times. As there are so many different styles of Western art, it would be impossible to describe all of them in such a short text. Consequently, this text will describe only the most important ones. Starting from the sixth century AD. The Middle Ages(5th to the 15th century AD) During the Middle Ages, the main aim of painters was to represent religious themes. A conventional artistof this period was not interested in showing nature and people as they really were. A typical picture at this time was full of religious symbols, which created a feeling of respect and love for God. But it was evident that ideas were changing in the 13th century when painters like Giotto di Bondone began to paint religious scenes in a more realistic way. The Renaissance(15th to 16th century) During the Renaissance, new ideas and values gradually replaced those held in the Middle Ages. People began to concentrate less on
英语选修六课文翻译 第五单元
英语选修六课文翻译第五单元 reading An exciting job I have the greatest job in the world. travel to unusual places and work alongside people from all over the world sometimes working outdoors sometimes in an office sometimes using scientific equipment and sometimes meeting local people and tourists I am never bored although my job is occasionally dangerous I don't mind because danger excites me and makes me feel alive However the most important thing about my job is that I heIp protect ordinary people from one of the most powerful forces on earth-the volcano. I was appointed as a volcanologist working for the Hawaiian Volcano Observatory (HVO) twenty years ago My job is collecting information for a database about Mount KiLauea which is one of the most active volcanoes in Hawaii Having collected and evaluated the information I help oyher scientists to predict where lava from the path of the lava can be warned to leave their houses Unfortunately we cannot move their homes out of the way and many houses have been covered with lava or burned to the ground. When boiling rock erupts from a volcano and crashes back to earth, it causes less damage than you might imagine. This is because no one lives near the top of Mount Kilauea, where the rocks fall. The lava that flows slowly like a wave down the mountain causes far more damage because it buries everything in its path under the molten rock. However, the eruption itself is really exciting to watch and I shall never forget my first sight of one. It was in the second week after I arrived in Hawaii. Having worked hard all day, I went to bed early. I was fast asleep when suddenly my bed began shaking and I heard a strange sound, like a railway train passing my window. Having experienced quite a few earthquakes in Hawaii already, I didn't take much notice. I was about to go back to sleep when suddenly my bedroom became as bright as day. I ran out of the house into the back garden where I could see Mount Kilauea in the distance. There had been an eruption from the side of the mountain and red hot lava was fountaining hundreds of metres into the air. It was an absolutely fantastic sight. The day after this eruption I was lucky enough to have a much closer look at it. Two other scientists and I were driven up the mountain and dropped as close as possible to the crater that had been formed duing the eruption. Having earlier collected special clothes from the observatory, we put them on before we went any closer. All three of us looked like spacemen. We had white protective suits that covered our whole body, helmets,big boots and special gloves. It was not easy to walk in these suits, but we slowly made our way to the edge of the crater and looked down into the red, boiling centre. The other two climbed down into the crater to collect some lava for later study, but this being my first experience, I stayed at the top and watched them.
高二英语教学设计 Book6 Unit 5 Reading An Exciting Job 1.教学目标（Teaching Goals）: a. To know how to read some words and phrases. b. To grasp and remember the detailed information of the reading material . c. To understand the general idea of the passage. d. To develop some basic reading skills. 2.教学重难点: a.. To understand the general idea of the passage. b. To develop some basic reading skills. Step I Lead-in and Pre-reading Let’s share a movie T: What’s happened in the movie? S: A volcano was erupting. All of them felt frightened/surprised/astonished/scared…… T: What do you think of volcano eruption and what can we do about it? S: A volcano eruption can do great damage to human beings. It seems that we human beings are powerless in front of these natural forces. But it can be predicted and damage can be reduced. T: Who will do this kind of job and what do you think of the job? S: volcanologist. It’s dangerous. T: I think it’s exciting. Ok, this class, let’s learn An Exciting Job. At first, I want to show you the goals of this class Step ⅡPre-reading Let the students take out their papers and check them in groups, and then write their answers on the blackboard (Self-learning) some words and phrases：volcano, erupt, alongside, appoint, equipment, volcanologist, database, evaluate, excite, fantastic, fountain, absolutely, unfortunately, potential, be compared with..., protect...from..., be appointed as, burn to the ground, be about to do sth., make one’s way. Check their answers and then let them lead the reading. Step III Fast-reading 这是一篇记叙文，一位火山学家的自述。作者首先介绍了他的工作性质，说明他热爱该项工作的主要原因是能帮助人们免遭火山袭击。然后，作者介绍了和另外二位科学家一道来到火山口的经历。最后，作者表达了他对自己工作的热情。许多年后，火山对他的吸引力依然不减。 Skimming Ⅰ.Read the passage and answer: (Group4) 1. Does the writer like his job?( Yes.) 2. Where is Mount Kilauea? (It is in Hawaii) 3. What is the volcanologist wearing when getting close to the crater? (He is wearing white protective suits that covered his whole body, helmets, big boots and
Unit5 Reading An Exciting Job 说课稿 Liu Baowei Part 1 My understanding of this lesson The analysis of the teaching material:This lesson is a reading passage. It plays a very important part in the English teaching of this unit. It tells us the writer’s exciting job as a volcanologist. From studying the passage, students can know the basic knowledge of volcano, and enjoy the occupation as a volcanologist. So here are my teaching goals: volcanologist 1. Ability goal: Enable the students to learn about the powerful natural force-volcano and the work as a volcanologist. 2. Learning ability goal: Help the students learn how to analyze the way the writer describes his exciting job. 3. Emotional goal: Make the Students love the nature and love their jobs. Learn how to express fear and anxiety Teaching important points: sentence structures 1. I was about to go back to sleep when suddenly my bedroom became as bright as day. 2. Having studied volcanoes now for more than twenty years, I am still amazed at their beauty as well as their potential to cause great damage. Teaching difficult points: 1. Use your own words to retell the text. 2. Discuss the natural disasters and their love to future jobs. Something about the S tudents: 1. The Students have known something about volcano but they don’t know the detailed information. 2. They are lack of vocabulary. 3. They don’t often use English to express themselves and communicate with others.
我的工作是世界上最伟大的工作。我跑的地方是稀罕奇特的地方，我见到的是世界各地有趣味的人们，有时在室外工作，有时在办公室里，有时工作中要用科学仪器，有时要会见当地百姓和旅游人士。但是我从不感到厌烦。虽然我的工作偶尔也有危险，但是我并不在乎，因为危险能激励我，使我感到有活力。然而，最重要的是，通过我的工作能保护人们免遭世界最大的自然威力之一，也就是火山的威胁。 我是一名火山学家，在夏威夷火山观测站（HVO）工作。我的主要任务是收集有关基拉韦厄火山的信息，这是夏威夷最活跃的火山之一。收集和评估了这些信息之后，我就帮助其他科学家一起预测下次火山熔岩将往何处流，流速是多少。我们的工作拯救了许多人的生命，因为熔岩要流经之地，老百姓都可以得到离开家园的通知。遗憾的是，我们不可能把他们的家搬离岩浆流过的地方，因此，许多房屋被熔岩淹没，或者焚烧殆尽。当滚烫沸腾的岩石从火山喷发出来并撞回地面时，它所造成的损失比想象的要小些，这是因为在岩石下落的基拉韦厄火山顶附近无人居住。而顺着山坡下流的火山熔岩造成的损失却大得多，这是因为火山岩浆所流经的地方，一切东西都被掩埋在熔岩下面了。然而火山喷发本身的确是很壮观的，我永远也忘不了我第一次看见火山喷发时的情景。那是在我到达夏威夷后的第二个星期。那天辛辛苦苦地干了一整天，我很早就上床睡觉。我在熟睡中突然感到床铺在摇晃，接着我听到一阵奇怪的声音，就好像一列火车从我的窗外行驶一样。因为我在夏威夷曾经经历过多次地震，所以对这种声音我并不在意。我刚要再睡，突然我的卧室亮如白昼。我赶紧跑出房间，来到后花园，在那儿我能远远地看见基拉韦厄火山。在山坡上，火山爆发了，红色发烫的岩浆像喷泉一样，朝天上喷射达几百米高。真是绝妙的奇景！ 就在这次火山喷发的第二天，我有幸做了一次近距离的观察。我和另外两位科学被送到山顶，在离火山爆发期间形成的火山口最靠近的地方才下车。早先从观测站出发时，就带了一些特制的安全服，于是我们穿上安全服再走近火山口。我们三个人看上去就像宇航员一样，我们都穿着白色的防护服遮住全身，戴上了头盔和特别的手套，还穿了一双大靴子。穿着这些衣服走起路来实在不容易，但我们还是缓缓往火山口的边缘走去，并且向下看到了红红的沸腾的中心。另外，两人攀下火山口，去收集供日后研究用的岩浆，我是第一次经历这样的事，所以留在山顶上观察他们
英语选修六课文翻译第五单元 reading An exciting job I have the greatest job in the world. travel to unusual places and work alongside people from all over the world sometimes working outdoors sometimes in an office sometimes using scientific equipment and sometimes meeting local people and tourists I am never bored although my job is occasionally dangerous I don't mind because danger excites me and makes me feel alive However the most important thing about my job is that I heIp protect ordinary people from one of the most powerful forces on earth-the volcano. I was appointed as a volcanologist working for the Hawaiian Volcano Observatory (HVO) twenty years ago My job is collecting information for a database about Mount KiLauea which is one of the most active volcanoes in Hawaii Having collected and evaluated the information I help oyher scientists to predict where lava from the path of the lava can be warned to leave their houses
新目标英语七年级下册课文Unit04 Coverstion1 A: What does your father do? B: He＇s a reporter. A:Really?That sounds interesting. Coverstion2 A:What does your mother do,Ken? B:She＇s a doctor. A:Really?I want to be a doctor. Coverstion3 A:What does your cousin do? B:You mean my cousin,Mike? A:Yeah,Mike.What does he do? B:He is as shop assistant. 2a,2b Coverstion1 A: Anna,doesyour mother work? B:Yes,she does .She has a new job. A:what does she do? B: Well ,she is as bank clerk,but she wants to be a policewoman. Coverstion2 A:Is that your father here ,Tony?
B:No,he isn't .He's working. B:But it's Saturday night.What does he do? B:He's a waiter Saturday is busy for him. A:Does he like it? B:Yes ,but he really wants to be an actor. Coverstion3 A:Susan,Is that your brother? B:Yes.it is A:What does he do? B:He's a student.He wants to be a doctor. section B , 2a,2b Jenny:So,Betty.what does yor father do? Betty: He's a policeman. Jenny:Do you want to be a policewoman? Betty:Oh,yes.Sometimes it's a little dangerous ,but it's also an exciting job.Jenny, your father is a bank clerk ,right? Jenny:Yes ,he is . Sam:Do you want to be a bank clerk,too? Jenny:No,not really.I want to be a reporter. Sam: Oh,yeah?Why? Jenny:It's very busy,but it's also fun.You meet so many interesting people.What about your father ,Sam. Sam: He's a reporter at the TV station.It's an exciting job,but it's also very difficult.He always has a lot of new things to learn.Iwant to be a reporter ,too
人教版选修Unit 5 The power of nature阅读课教学设计 Learning aims Knowledge aims: Master the useful words and expressions related to the text. Ability aims: Learn about some disasters that are caused by natural forces, how people feel in dangerous situations. Emotion aims: Learn the ways in which humans protect themselves from natural disasters. Step1 Leading-in 1.Where would you like to spend your holiday? 2.What about a volcano? 3.What about doing such dangerous work as part of your job ? https://www.doczj.com/doc/037751038.html, every part of a volcano. Ash cloud/volcanic ash/ Crater/ Lava /Magma chamber 【设计意图】通过图片激发学生兴趣，引出本单元的话题，要求学生通过讨论, 了解火山基本信息，引出火山文化背景，为后面的阅读做铺垫。利用头脑风暴法收集学生对课文内容的预测并板书下来。文内容进行预测，培养学生预测阅读内容的能力。同时通过预测激起进一步探究 Step2. Skimming What’s the main topic of the article?
Unit1 SectionA 1a Canada, France ,Japan ,the United States ,Australia, Singapore ,the United Kingdom,China 1b Boy1:Where is you pen pal from,Mike? Boy2:He's from Canada. Boy1:Really?My pen pal's from Australia.How about you,Lily?Where's your pen pal from? Girl1:She's from Japan.Where is Tony's pen pal from? Gril2:I think she's from Singapore. 2b 2c Conversation1 A: Where's you pen pal from, John? B: He's from Japan, A:Oh,really?Where does he live? B: Tokyo. Conversation2 A: Where's your pen pal from, Jodie? B: She's from France. A: Oh, she lives in Pairs. Conversation3 A: Andrew, where's your pen pal from? B: She's from France. A: Uh-huh. Where does she live? B: Oh, She lives in Paris.