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The Electromagnetic Spectrum header
The Electromagnetic Spectrum header graphic
RADIO WAVES | MICROWAVES | INFRARED | VISIBLE LIGHT | ULTRAVIOLET | X-RAYS | GAMMA RAYS
X-rays
X-ray range of the spectrum.
As the wavelengths of light decrease, they increase in energy. X-rays have smaller wavelengths and therefore higher energy than ultraviolet waves. We usually talk about X-rays in terms of their energy rather than wavelength. This is partially because X-rays have very small wavelengths. It is also because X-ray light tends to act more like a particle than a wave. X-ray detectors collect actual photons of X-ray light - which is very different from the radio telescopes that have large dishes designed to focus radio waves!
X-rays were first observed and documented in 1895 by Wilhelm Conrad Roentgen, a German scientist who found them quite by accident when experimenting with vacuum tubes.
A week later, he took an X-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Roentgen called it "X" to indicate it was an unknown type of radiation. The name stuck, although (over Roentgen's objections), many of his colleagues suggested calling them Roentgen rays. They are still occasionally referred to as Roentgen rays in German-speaking countries. Roentgen's wife's hand.
The Earth's atmosphere is thick enough that virtually no X-rays are able to penetrate from outer space all the way to the Earth's surface. This is good for us but also bad for astronomy - we have to put X-ray telescopes and detectors on satellites! We cannot do X-ray astronomy from the ground.
How do we "see" using X-ray light?
What would it be like to see X-rays? Well, we wouldn't be able to see through people's clothes, no matter what the ads for X-ray glasses tell us! If we could see X-rays, we could see things that either emit X-rays or halt their transmission. Our eyes would be like the X-ray film used in hospitals or dentist's offices. X-ray film "sees" X-rays, like the ones that travel through your skin. It also sees shadows left by things that the X-rays can't travel through (like bones or metal).
Woman in dentist's chair. D When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you. At a dentist, the film is put inside your mouth, on one side of your teeth, and X-rays are shot through your jaw, just like in this picture. It doesn't hurt at all - you can't feel X-rays.
X-ray of a tooth D Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays - can you see the filling in the image of the tooth?
X-ray of one-year old showing a pin. D When the Sun shines on us at a certain angle, our shadow is projected onto the ground. Similarly, when X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film.
This is an X-ray photo of a one year old girl. Can you see the shadow of what she swallowed?
We use satellites with X-ray detectors on them to do X-ray astronomy. In astronomy, things that emit X-rays (for example, black holes) are like the dentist's X-ray machine, and the detector on the satellite is like the X-ray film. X-ray detectors collect individual X-rays (photons of X-ray light) and things like the number of photons collected, the energy of the photons collected, or how fast the photons are detected, can tell us things about the object that is emitting them.
To the right is an image of a real X-ray detector. This instrument is called the Proportional Counter Array and it is on the Rossi X-ray Timing Explorer (RXTE) satellite. It looks very different from anything you might see at a dentist's office!
One of RXTE's X-ray detectors.D
What does X-ray light show us?
Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets!
The Earth glows in many kinds of light, including the energetic X-ray band. Actually, the Earth itself does not glow - only aurora produced high in the Earth's atmosphere. These aurora are caused by charged particles from the Sun.
X-ray image of EarthD
Credit: Polar, PIXIE, NASA
To the left is the first picture of the Earth in X-rays, taken in March, 1996 with the orbiting Polar satellite. The area of brightest X-ray emission is red. The energetic charged particles from the Sun that cause aurora also energize electrons in the Earth's magnetosphere. These electrons move along the Earth's magnetic field and eventually strike the Earth's ionosphere, causing the X-ray emission. These X-rays are not dangerous because they are absorbed by lower parts of the Earth's atmosphere. (The above caption and image are from the Astronomy Picture of the Day for December 30, 1996.)
An X-ray image of a comet. D Recently, we learned that even comets emit X-rays! This image of Comet Hyakutake was taken by an X-ray satellite called ROSAT, short for the Roentgen Satellite. (It was named after the discoverer of X-rays.)
The X-ray Sun D The Sun also emits X-rays - here is what the Sun looked like in X-rays on April 27th, 2000. This image was taken by the Yokoh satellite.
Artist's conception of a binary systemD Many things in deep space give off X-rays. Many stars are in binary star systems - which means that two stars orbit each other. When one of these stars is a black hole or a neutron star, material is pulled off the normal star. This materials spirals into the black hole or neutron star and heats up to very high temperatures. When something is heated to over a million degrees, it will give off X-rays!
The above image is an artist's conception of a binary star system - it shows the material being pulled off the red star by its invisible black hole companion and into an orbiting disk.
Multiwavelength supernova remnantD
Credit: X-ray (NASA/CXC/SAO);
Optical (NASA/HST);
Radio: (CSIRO/ATNF/ATCA)
This image is special - it shows a supernova remnant - the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The false-colors show what this supernova remnant looks like in X-rays (in blue), visible light (green) and radio (red).
X-ray image of same remnant.D
Credit: NASA/CXC/SAO
This is the same supernova remnant but this image shows only
RADIO WAVES | MICROWAVES | INFRARED | VISIBLE LIGHT | ULTRAVIOLET | X-RAYS | GAMMA RAYS
X-rays
X-ray range of the spectrum.
As the wavelengths of light decrease, they increase in energy. X-rays have smaller wavelengths and therefore higher energy than ultraviolet waves. We usually talk about X-rays in terms of their energy rather than wavelength. This is partially because X-rays have very small wavelengths. It is also because X-ray light tends to act more like a particle than a wave. X-ray detectors collect actual photons of X-ray light - which is very different from the radio telescopes that have large dishes designed to focus radio waves!
X-rays were first observed and documented in 1895 by Wilhelm Conrad Roentgen, a German scientist who found them quite by accident when experimenting with vacuum tubes.
A week later, he took an X-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Roentgen called it "X" to indicate it was an unknown type of radiation. The name stuck, although (over Roentgen's objections), many of his colleagues suggested calling them Roentgen rays. They are still occasionally referred to as Roentgen rays in German-speaking countries. Roentgen's wife's hand.
The Earth's atmosphere is thick enough that virtually no X-rays are able to penetrate from outer space all the way to the Earth's surface. This is good for us but also bad for astronomy - we have to put X-ray telescopes and detectors on satellites! We cannot do X-ray astronomy from the ground.
How do we "see" using X-ray light?
What would it be like to see X-rays? Well, we wouldn't be able to see through people's clothes, no matter what the ads for X-ray glasses tell us! If we could see X-rays, we could see things that either emit X-rays or halt their transmission. Our eyes would be like the X-ray film used in hospitals or dentist's offices. X-ray film "sees" X-rays, like the ones that travel through your skin. It also sees shadows left by things that the X-rays can't travel through (like bones or metal).
Woman in dentist's chair. D When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you. At a dentist, the film is put inside your mouth, on one side of your teeth, and X-rays are shot through your jaw, just like in this picture. It doesn't hurt at all - you can't feel X-rays.
X-ray of a tooth D Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays - can you see the filling in the image of the tooth?
X-ray of one-year old showing a pin. D When the Sun shines on us at a certain angle, our shadow is projected onto the ground. Similarly, when X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film.
This is an X-ray photo of a one year old girl. Can you see the shadow of what she swallowed?
We use satellites with X-ray detectors on them to do X-ray astronomy. In astronomy, things that emit X-rays (for example, black holes) are like the dentist's X-ray machine, and the detector on the satellite is like the X-ray film. X-ray detectors collect individual X-rays (photons of X-ray light) and things like the number of photons collected, the energy of the photons collected, or how fast the photons are detected, can tell us things about the object that is emitting them.
To the right is an image of a real X-ray detector. This instrument is called the Proportional Counter Array and it is on the Rossi X-ray Timing Explorer (RXTE) satellite. It looks very different from anything you might see at a dentist's office!
One of RXTE's X-ray detectors.D
What does X-ray light show us?
Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets!
The Earth glows in many kinds of light, including the energetic X-ray band. Actually, the Earth itself does not glow - only aurora produced high in the Earth's atmosphere. These aurora are caused by charged particles from the Sun.
X-ray image of EarthD
Credit: Polar, PIXIE, NASA
To the left is the first picture of the Earth in X-rays, taken in March, 1996 with the orbiting Polar satellite. The area of brightest X-ray emission is red. The energetic charged particles from the Sun that cause aurora also energize electrons in the Earth's magnetosphere. These electrons move along the Earth's magnetic field and eventually strike the Earth's ionosphere, causing the X-ray emission. These X-rays are not dangerous because they are absorbed by lower parts of the Earth's atmosphere. (The above caption and image are from the Astronomy Picture of the Day for December 30, 1996.)
An X-ray image of a comet. D Recently, we learned that even comets emit X-rays! This image of Comet Hyakutake was taken by an X-ray satellite called ROSAT, short for the Roentgen Satellite. (It was named after the discoverer of X-rays.)
The X-ray Sun D The Sun also emits X-rays - here is what the Sun looked like in X-rays on April 27th, 2000. This image was taken by the Yokoh satellite.
Artist's conception of a binary systemD Many things in deep space give off X-rays. Many stars are in binary star systems - which means that two stars orbit each other. When one of these stars is a black hole or a neutron star, material is pulled off the normal star. This materials spirals into the black hole or neutron star and heats up to very high temperatures. When something is heated to over a million degrees, it will give off X-rays!
The above image is an artist's conception of a binary star system - it shows the material being pulled off the red star by its invisible black hole companion and into an orbiting disk.
Multiwavelength supernova remnantD
Credit: X-ray (NASA/CXC/SAO);
Optical (NASA/HST);
Radio: (CSIRO/ATNF/ATCA)
This image is special - it shows a supernova remnant - the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The false-colors show what this supernova remnant looks like in X-rays (in blue), visible light (green) and radio (red).
X-ray image of same remnant.D
Credit: NASA/CXC/SAO
This is the same supernova remnant but this image shows only
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Đồ họa tiêu đề phổ điện từSÓNG VÔ TUYẾN | LÒ VI SÓNG | HỒNG NGOẠI | ÁNH SÁNG KHẢ KIẾN | TIA CỰC TÍM | X-QUANG | TIA GAMMAX-quangX-quang các phạm vi của quang phổ.Như các bước sóng của ánh sáng giảm, chúng làm tăng năng lượng. Chụp x-quang có bước sóng nhỏ hơn và cao hơn do đó năng lượng hơn so với sóng cực tím. Chúng tôi thường nói về x-quang trong điều khoản của năng lượng của họ chứ không phải là bước sóng. Đây là một phần vì chụp x-quang có bước sóng rất nhỏ. Nó cũng là do ánh sáng tia x có xu hướng hành động giống như một hạt hơn một làn sóng. Thiết bị dò tia x thu thập thực tế photon của ánh sáng tia x - là rất khác nhau từ kính viễn vọng radio có các món ăn lớn được thiết kế để tập trung đài phát thanh sóng!Chụp x-quang lần đầu tiên được quan sát và tài liệu vào năm 1895 của Wilhelm Conrad Roentgen, một nhà khoa học Đức đã tìm thấy chúng khá do tai nạn khi thử nghiệm với ống chân không.Một tuần sau đó, ông đã lấy một bức ảnh chụp x-quang của bàn tay của vợ mà rõ ràng cho thấy nhẫn cưới của cô và xương của cô. Bức điện khí hoá khu vực chung và đánh thức tuyệt vời khoa học quan tâm chung trong các hình thức mới của bức xạ. Roentgen gọi nó "X" để cho biết nó là một loại không biết của bức xạ. Tên khó khăn, mặc dù (qua phản đối của Roentgen), nhiều người trong số đồng nghiệp của ông đề nghị gọi điện cho họ Roentgen tia. Họ vẫn thỉnh thoảng được gọi là Roentgen tia trong nước nói tiếng Đức. Roentgen của vợ của tay.Khí quyển của trái đất là dày đủ mà hầu như không có x-quang có thể xâm nhập từ không gian bên ngoài đến bề mặt trái đất. Điều này là tốt cho chúng tôi, nhưng cũng có hại cho thiên văn học - chúng ta phải đặt kính thiên văn chụp x-quang và thiết bị dò trên vệ tinh! Chúng tôi không thể làm thiên văn học X-ray từ mặt đất.Làm cách nào chúng tôi "xem" bằng cách sử dụng ánh sáng tia x?Những gì nó sẽ là như xem x-quang? Vâng, chúng tôi sẽ không thể xem thông qua quần áo của mọi người, không có vấn đề gì các quảng cáo cho x-quang kính nói với chúng tôi! Nếu chúng ta có thể thấy chụp x-quang, chúng tôi có thể nhìn thấy những điều mà phát ra tia x hoặc ngăn chặn của truyền. Mắt của chúng tôi sẽ như bộ phim x-quang, được sử dụng trong bệnh viện hoặc văn phòng của Nha sĩ. Phim x-quang "nhìn thấy" x-quang, như những người đi du lịch thông qua làn da của bạn. Nó cũng nhìn thấy bóng tối lại bởi những điều mà các tia x không thể đi du lịch thông qua (như xương hoặc kim loại).Người phụ nữ trên ghế của Nha sĩ. D khi bạn nhận được một x-quang chụp tại một bệnh viện, x-quang nhạy cảm phim đặt một bên của cơ thể của bạn và x-quang được bắn qua bạn. Tại một nha sĩ, bộ phim được đặt bên trong miệng của bạn, trên một mặt của răng của bạn, và chụp x-quang được bắn qua hàm của bạn, giống như trong ảnh này. Nó không đau ở tất cả - bạn không thể cảm thấy chụp x-quang.X-quang của một chiếc răng D vì xương và răng của bạn dày đặc và hấp thụ tia x thêm sau đó làn da của bạn, bóng của xương hoặc răng của bạn là trái trên phim x-quang trong khi làn da của bạn xuất hiện trong suốt. Kim loại hấp thụ tia x hơn - bạn có thể xem việc làm trong hình ảnh của răng?X-quang của một - năm tuổi đang hiển thị một mã pin. D khi mặt trời tỏa sáng trên chúng tôi ở một góc độ nhất định, bóng tối của chúng tôi chiếu lên mặt đất. Tương tự như vậy, khi chụp x-quang ánh sáng tỏa sáng trên chúng tôi, nó đi qua da của chúng tôi, nhưng cho phép bóng tối của xương của chúng tôi để được chiếu lên và bị bắt bởi phim.Đây là một ảnh chụp x-quang của một cô gái một tuổi. Bạn có thể nhìn thấy bóng tối của những gì cô nuốt?Chúng tôi sử dụng vệ tinh với thiết bị dò tia x vào chúng để làm thiên văn học X-ray. Trong thiên văn học, điều mà phát ra tia x (ví dụ, lỗ đen) như máy chụp x-quang của Nha sĩ, và các máy dò trên vệ tinh là giống như bộ phim x-quang. Thiết bị dò tia x thu thập cá nhân chụp x-quang (photon của ánh sáng tia x) và những thứ như số lượng photon được thu thập, năng lượng của photon được thu thập, hoặc làm thế nào nhanh chóng các photon được phát hiện, có thể cho chúng tôi những điều về các đối tượng mà phát ra chúng.Ở bên phải là một hình ảnh của một máy dò tia x thực sự. Nhạc cụ này được gọi là tỉ lệ số lượt truy cập mảng và nó là trên vệ tinh Rossi tia x thời gian Explorer (RXTE). Nó trông rất khác nhau từ bất cứ điều gì bạn có thể thấy tại văn phòng của Nha sĩ!Một số thiết bị dò tia x của RXTE.DNhững gì hiện x-quang ánh sáng cho chúng ta?Nhiều điều trong không gian phát ra tia x, trong số đó là lỗ đen, sao neutron, Hệ thống sao đôi, tàn tích siêu tân tinh, sao, mặt trời, và thậm chí một số sao chổi!Glows trái đất trong nhiều các loại ánh sáng, bao gồm cả ban nhạc X-ray tràn đầy năng lượng. Trên thực tế, trái đất không sáng - chỉ aurora sản xuất cao trong khí quyển của trái đất. Aurora được gây ra bởi tính hạt từ mặt trời. X-quang hình ảnh của EarthDTín dụng: Vùng cực, PIXIE, NASABên trái là hình ảnh đầu tiên của trái đất trong chụp x-quang, chụp tháng 3, năm 1996 với vệ tinh quay quanh Bắc cực. Khu vực phát xạ tia x sáng nhất là màu đỏ. Các hạt năng lượng điện từ mặt trời gây ra aurora cũng thêm nghị lực electron trong quyển từ của trái đất. Các điện tử di chuyển cùng của trái đất từ trường và cuối cùng tấn công tầng điện ly của trái đất, gây ra sự phát thải x-quang. Các tia x là không nguy hiểm bởi vì họ được hấp thụ bởi phần thấp hơn của khí quyển của trái đất. (Chú thích và hình ảnh trên là từ hình ảnh thiên văn học của ngày 30 tháng 12, 1996.) Một hình ảnh chụp x-quang của một sao chổi. D mới, chúng tôi đã học được rằng thậm chí sao chổi phát ra tia x! Hình ảnh này của sao chổi Hyakutake được thực hiện bởi một vệ tinh chụp x-quang được gọi là ROSAT, ngắn cho vệ tinh Roentgen. (Nó được đặt tên theo các phát hiện của x-quang.)X-quang Sun D mặt trời cũng phát ra tia x - đây là những gì mặt trời trông giống như trong chụp x-quang ngày 27 tháng 4 năm 2000. Hình ảnh này được chụp bằng vệ tinh Yokoh. Quan niệm của nghệ sĩ của một systemD nhị phân nhiều điều trong không gian sâu cho ra chụp x-quang. Nhiều ngôi sao nằm trong hệ thống sao đôi - có nghĩa là hai ngôi sao quỹ đạo lẫn nhau. Khi một trong những ngôi sao là một lỗ đen hoặc một sao neutron, vật liệu kéo ra khỏi ngôi sao bình thường. Này thiên hà xoắn ốc tài liệu vào lỗ đen hoặc sao neutron và nóng lên đến nhiệt độ rất cao. Khi một cái gì đó được đun nóng đến hơn một triệu độ, nó sẽ cho ra tia x!Hình ảnh trên là một nghệ sĩ quan niệm của hệ sao đôi - nó cho thấy các tài liệu được kéo ra khỏi các ngôi sao màu đỏ bằng đồng hành vô hình lỗ đen của mình và vào một đĩa quay quanh.Siêu tân tinh multiwavelength remnantDTín dụng: X-quang (NASA/CXC/SAO); Quang học (NASA/HST);Đài phát thanh: (CSIRO/ATNF/ATCA)Hình ảnh này là đặc biệt - nó cho thấy một tàn tích siêu tân tinh - tàn tích của một ngôi sao phát nổ trong một thiên hà gần đó được gọi là các đám mây Magellan nhỏ. Sai màu sắc Hiển thị những gì tàn tích siêu tân tinh này trông giống như trong chụp x-quang (trong màu xanh), ánh sáng khả kiến (xanh) và đài phát thanh (màu đỏ).X-quang các hình ảnh của cùng dấu tích.D Tín: NASA/CXC/SAOĐây là cùng một tàn tích siêu tân tinh nhưng hình ảnh này cho thấy chỉ
đang được dịch, vui lòng đợi..
The Electromagnetic Spectrum header graphic
RADIO WAVES | MICROWAVES | INFRARED | VISIBLE LIGHT | ULTRAVIOLET | X-RAYS | GAMMA RAYS
X-rays
X-ray range of the spectrum.
As the wavelengths of light decrease, they increase in energy. X-rays have smaller wavelengths and therefore higher energy than ultraviolet waves. We usually talk about X-rays in terms of their energy rather than wavelength. This is partially because X-rays have very small wavelengths. It is also because X-ray light tends to act more like a particle than a wave. X-ray detectors collect actual photons of X-ray light - which is very different from the radio telescopes that have large dishes designed to focus radio waves!
X-rays were first observed and documented in 1895 by Wilhelm Conrad Roentgen, a German scientist who found them quite by accident when experimenting with vacuum tubes.
A week later, he took an X-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Roentgen called it "X" to indicate it was an unknown type of radiation. The name stuck, although (over Roentgen's objections), many of his colleagues suggested calling them Roentgen rays. They are still occasionally referred to as Roentgen rays in German-speaking countries. Roentgen's wife's hand.
The Earth's atmosphere is thick enough that virtually no X-rays are able to penetrate from outer space all the way to the Earth's surface. This is good for us but also bad for astronomy - we have to put X-ray telescopes and detectors on satellites! We cannot do X-ray astronomy from the ground.
How do we "see" using X-ray light?
What would it be like to see X-rays? Well, we wouldn't be able to see through people's clothes, no matter what the ads for X-ray glasses tell us! If we could see X-rays, we could see things that either emit X-rays or halt their transmission. Our eyes would be like the X-ray film used in hospitals or dentist's offices. X-ray film "sees" X-rays, like the ones that travel through your skin. It also sees shadows left by things that the X-rays can't travel through (like bones or metal).
Woman in dentist's chair. D When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you. At a dentist, the film is put inside your mouth, on one side of your teeth, and X-rays are shot through your jaw, just like in this picture. It doesn't hurt at all - you can't feel X-rays.
X-ray of a tooth D Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays - can you see the filling in the image of the tooth?
X-ray of one-year old showing a pin. D When the Sun shines on us at a certain angle, our shadow is projected onto the ground. Similarly, when X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film.
This is an X-ray photo of a one year old girl. Can you see the shadow of what she swallowed?
We use satellites with X-ray detectors on them to do X-ray astronomy. In astronomy, things that emit X-rays (for example, black holes) are like the dentist's X-ray machine, and the detector on the satellite is like the X-ray film. X-ray detectors collect individual X-rays (photons of X-ray light) and things like the number of photons collected, the energy of the photons collected, or how fast the photons are detected, can tell us things about the object that is emitting them.
To the right is an image of a real X-ray detector. This instrument is called the Proportional Counter Array and it is on the Rossi X-ray Timing Explorer (RXTE) satellite. It looks very different from anything you might see at a dentist's office!
One of RXTE's X-ray detectors.D
What does X-ray light show us?
Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets!
The Earth glows in many kinds of light, including the energetic X-ray band. Actually, the Earth itself does not glow - only aurora produced high in the Earth's atmosphere. These aurora are caused by charged particles from the Sun.
X-ray image of EarthD
Credit: Polar, PIXIE, NASA
To the left is the first picture of the Earth in X-rays, taken in March, 1996 with the orbiting Polar satellite. The area of brightest X-ray emission is red. The energetic charged particles from the Sun that cause aurora also energize electrons in the Earth's magnetosphere. These electrons move along the Earth's magnetic field and eventually strike the Earth's ionosphere, causing the X-ray emission. These X-rays are not dangerous because they are absorbed by lower parts of the Earth's atmosphere. (The above caption and image are from the Astronomy Picture of the Day for December 30, 1996.)
An X-ray image of a comet. D Recently, we learned that even comets emit X-rays! This image of Comet Hyakutake was taken by an X-ray satellite called ROSAT, short for the Roentgen Satellite. (It was named after the discoverer of X-rays.)
The X-ray Sun D The Sun also emits X-rays - here is what the Sun looked like in X-rays on April 27th, 2000. This image was taken by the Yokoh satellite.
Artist's conception of a binary systemD Many things in deep space give off X-rays. Many stars are in binary star systems - which means that two stars orbit each other. When one of these stars is a black hole or a neutron star, material is pulled off the normal star. This materials spirals into the black hole or neutron star and heats up to very high temperatures. When something is heated to over a million degrees, it will give off X-rays!
The above image is an artist's conception of a binary star system - it shows the material being pulled off the red star by its invisible black hole companion and into an orbiting disk.
Multiwavelength supernova remnantD
Credit: X-ray (NASA/CXC/SAO);
Optical (NASA/HST);
Radio: (CSIRO/ATNF/ATCA)
This image is special - it shows a supernova remnant - the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The false-colors show what this supernova remnant looks like in X-rays (in blue), visible light (green) and radio (red).
X-ray image of same remnant.D
Credit: NASA/CXC/SAO
This is the same supernova remnant but this image shows only
RADIO WAVES | MICROWAVES | INFRARED | VISIBLE LIGHT | ULTRAVIOLET | X-RAYS | GAMMA RAYS
X-rays
X-ray range of the spectrum.
As the wavelengths of light decrease, they increase in energy. X-rays have smaller wavelengths and therefore higher energy than ultraviolet waves. We usually talk about X-rays in terms of their energy rather than wavelength. This is partially because X-rays have very small wavelengths. It is also because X-ray light tends to act more like a particle than a wave. X-ray detectors collect actual photons of X-ray light - which is very different from the radio telescopes that have large dishes designed to focus radio waves!
X-rays were first observed and documented in 1895 by Wilhelm Conrad Roentgen, a German scientist who found them quite by accident when experimenting with vacuum tubes.
A week later, he took an X-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Roentgen called it "X" to indicate it was an unknown type of radiation. The name stuck, although (over Roentgen's objections), many of his colleagues suggested calling them Roentgen rays. They are still occasionally referred to as Roentgen rays in German-speaking countries. Roentgen's wife's hand.
The Earth's atmosphere is thick enough that virtually no X-rays are able to penetrate from outer space all the way to the Earth's surface. This is good for us but also bad for astronomy - we have to put X-ray telescopes and detectors on satellites! We cannot do X-ray astronomy from the ground.
How do we "see" using X-ray light?
What would it be like to see X-rays? Well, we wouldn't be able to see through people's clothes, no matter what the ads for X-ray glasses tell us! If we could see X-rays, we could see things that either emit X-rays or halt their transmission. Our eyes would be like the X-ray film used in hospitals or dentist's offices. X-ray film "sees" X-rays, like the ones that travel through your skin. It also sees shadows left by things that the X-rays can't travel through (like bones or metal).
Woman in dentist's chair. D When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you. At a dentist, the film is put inside your mouth, on one side of your teeth, and X-rays are shot through your jaw, just like in this picture. It doesn't hurt at all - you can't feel X-rays.
X-ray of a tooth D Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays - can you see the filling in the image of the tooth?
X-ray of one-year old showing a pin. D When the Sun shines on us at a certain angle, our shadow is projected onto the ground. Similarly, when X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film.
This is an X-ray photo of a one year old girl. Can you see the shadow of what she swallowed?
We use satellites with X-ray detectors on them to do X-ray astronomy. In astronomy, things that emit X-rays (for example, black holes) are like the dentist's X-ray machine, and the detector on the satellite is like the X-ray film. X-ray detectors collect individual X-rays (photons of X-ray light) and things like the number of photons collected, the energy of the photons collected, or how fast the photons are detected, can tell us things about the object that is emitting them.
To the right is an image of a real X-ray detector. This instrument is called the Proportional Counter Array and it is on the Rossi X-ray Timing Explorer (RXTE) satellite. It looks very different from anything you might see at a dentist's office!
One of RXTE's X-ray detectors.D
What does X-ray light show us?
Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets!
The Earth glows in many kinds of light, including the energetic X-ray band. Actually, the Earth itself does not glow - only aurora produced high in the Earth's atmosphere. These aurora are caused by charged particles from the Sun.
X-ray image of EarthD
Credit: Polar, PIXIE, NASA
To the left is the first picture of the Earth in X-rays, taken in March, 1996 with the orbiting Polar satellite. The area of brightest X-ray emission is red. The energetic charged particles from the Sun that cause aurora also energize electrons in the Earth's magnetosphere. These electrons move along the Earth's magnetic field and eventually strike the Earth's ionosphere, causing the X-ray emission. These X-rays are not dangerous because they are absorbed by lower parts of the Earth's atmosphere. (The above caption and image are from the Astronomy Picture of the Day for December 30, 1996.)
An X-ray image of a comet. D Recently, we learned that even comets emit X-rays! This image of Comet Hyakutake was taken by an X-ray satellite called ROSAT, short for the Roentgen Satellite. (It was named after the discoverer of X-rays.)
The X-ray Sun D The Sun also emits X-rays - here is what the Sun looked like in X-rays on April 27th, 2000. This image was taken by the Yokoh satellite.
Artist's conception of a binary systemD Many things in deep space give off X-rays. Many stars are in binary star systems - which means that two stars orbit each other. When one of these stars is a black hole or a neutron star, material is pulled off the normal star. This materials spirals into the black hole or neutron star and heats up to very high temperatures. When something is heated to over a million degrees, it will give off X-rays!
The above image is an artist's conception of a binary star system - it shows the material being pulled off the red star by its invisible black hole companion and into an orbiting disk.
Multiwavelength supernova remnantD
Credit: X-ray (NASA/CXC/SAO);
Optical (NASA/HST);
Radio: (CSIRO/ATNF/ATCA)
This image is special - it shows a supernova remnant - the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The false-colors show what this supernova remnant looks like in X-rays (in blue), visible light (green) and radio (red).
X-ray image of same remnant.D
Credit: NASA/CXC/SAO
This is the same supernova remnant but this image shows only
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