The light from stars looks white to us, but when you pass this light through a prism, you can see a rainbow of colours. These colours represent different wavelengths of light. Red wavelengths are longer than blue ones.

Light also comes in other "colours" that we can't see, and each has its own wavelength. The wavelength tells us what type of energy is being emitted. The longest wavelengths produce radio waves, and the shortest ones produce gamma rays. In between, we find microwaves, infrared radiation, visible light, ultraviolet radiation, and X-rays. All these types of energy together make up the electromagnetic spectrum.
The light from stars looks white to us, but when you pass this light through a prism, you can see a rainbow of colours. These colours represent different wavelengths of light. Red wavelengths are longer than blue ones.

Light also comes in other "colours" that we can't see, and each has its own wavelength. The wavelength tells us what type of energy is being emitted. The longest wavelengths produce radio waves, and the shortest ones produce gamma rays. In between, we find microwaves, infrared radiation, visible light, ultraviolet radiation, and X-rays. All these types of energy together make up the electromagnetic spectrum.

© Canadian Heritage Information Network, 2003

The Electromagnetic Spectrum

The Electromagnetic Spectrum

NASA

© NASA


How do astronomers manage to learn so much about stars and galaxies that are so far away? The answer is found in rainbows. The light from stars can be separated into a spectrum-the rainbow of the light’s component colours. By studying this spectrum, astronomers have learned almost everything they know about the universe.

Astronomers study the spectra of stars to understand the stars’ physical properties. For example, chemicals in a star’s atmosphere may absorb some of the star’s energy, but dark lines in the coloured spectrum show where energy was absorbed. Every chemical has a unique pattern of lines, so a star’s spectrum reveals its chemical make-up.

Spectroscopy-the analysis of the spectra of stars-is probably the single most important tool that astronomers have. By carefully analyzing spectral lines, astronomers can learn the chemical composition, temperature, magnetic fields and velocities of stars, nebulae and galaxies.
How do astronomers manage to learn so much about stars and galaxies that are so far away? The answer is found in rainbows. The light from stars can be separated into a spectrum-the rainbow of the light’s component colours. By studying this spectrum, astronomers have learned almost everything they know about the universe.

Astronomers study the spectra of stars to understand the stars’ physical properties. For example, chemicals in a star’s atmosphere may absorb some of the star’s energy, but dark lines in the coloured spectrum show where energy was absorbed. Every chemical has a unique pattern of lines, so a star’s spectrum reveals its chemical make-up.

Spectroscopy-the analysis of the spectra of stars-is probably the single most important tool that astronomers have. By carefully analyzing spectral lines, astronomers can learn the chemical composition, temperature, magnetic fields and velocities of stars, nebulae and galaxies.

© Canadian Heritage Information Network, 2003

Absorption Spectrum

The elements in a star absorb certain sections of the spectra, or rainbow of a star. Where these black lines appear tell us what the star is made of.

National Research Council of Canada.

© National Research Council of Canada.


An instrument called a spectrograph spreads the light from celestial objects so that it can be studied. The Gemini North telescope in Hawaii uses a sophisticated instrument called the Gemini Multi-Object Spectrograph (GMOS).

The Gemini Multi-Object Spectrograph (GMOS) is a sophisticated new instrument on the Gemini North telescope on Mauna Kea, Hawaii. GMOS works by breaking down starlight into its component colours for analysis. From that light, astronomers can learn the chemical composition of stars and galaxies, their mass and how fast they're moving towards us or away from us.

GMOS was developed by the Herzberg Institute of Astrophysics (Canada), the Astronomy Technology Centre (U.K.) and the University of Durham (U.K.).
An instrument called a spectrograph spreads the light from celestial objects so that it can be studied. The Gemini North telescope in Hawaii uses a sophisticated instrument called the Gemini Multi-Object Spectrograph (GMOS).

The Gemini Multi-Object Spectrograph (GMOS) is a sophisticated new instrument on the Gemini North telescope on Mauna Kea, Hawaii. GMOS works by breaking down starlight into its component colours for analysis. From that light, astronomers can learn the chemical composition of stars and galaxies, their mass and how fast they're moving towards us or away from us.

GMOS was developed by the Herzberg Institute of Astrophysics (Canada), the Astronomy Technology Centre (U.K.) and the University of Durham (U.K.).

© Canadian Heritage Information Network, 2003

Galaxy NGC 628

The first image captured by GMOS was the large galaxy NGC 628 in Pisces. It has been called the "perfect spiral galaxy" due to its nearly ideal form.

Gemini North

© Gemini North


GMOS

Although GMOS weighs two tons, it is sensitive enough to measure motions as small as one micron (one-millionth of a metre). Astronomers need this level of precision to measure changes in galaxies that are millions, or billions, of light-years away.

Gemini Observatory

© Gemini Observatory


When starlight passes through our atmosphere, it gets distorted by turbulence (the mixing of warm and cold air). This is why stars twinkle when you look at them. Telescopes only magnify this distortion, so stars can end up looking like shimmering blobs instead of pinpoints of light.

With technology called adaptive optics, astronomers can correct this distortion to get a clearer image. Adaptive optics takes a sample of starlight and calculates how it has been distorted by the atmosphere. It then straightens the light with a flexible mirror that changes shape about 1 000 times per second.

Gemini North Telescope

With a new adaptive optics system on the Gemini North telescope on Mauna Kea, Hawaii, astronomers hope to peek into the heart of stellar nurseries-or watch the birth of galaxies that formed 10 billion years ago. This adaptive optics system, called Altair, was built by Canada’s Herzberg Institute of Astrophysics.

Altair uses an integrated computer to calculate the distortion caused by the atmosphere. Tiny mechanical devices mounted behind the flexible mirror make thousands of adjustments per second to sharpen the telescope& Read More
When starlight passes through our atmosphere, it gets distorted by turbulence (the mixing of warm and cold air). This is why stars twinkle when you look at them. Telescopes only magnify this distortion, so stars can end up looking like shimmering blobs instead of pinpoints of light.

With technology called adaptive optics, astronomers can correct this distortion to get a clearer image. Adaptive optics takes a sample of starlight and calculates how it has been distorted by the atmosphere. It then straightens the light with a flexible mirror that changes shape about 1 000 times per second.

Gemini North Telescope

With a new adaptive optics system on the Gemini North telescope on Mauna Kea, Hawaii, astronomers hope to peek into the heart of stellar nurseries-or watch the birth of galaxies that formed 10 billion years ago. This adaptive optics system, called Altair, was built by Canada’s Herzberg Institute of Astrophysics.

Altair uses an integrated computer to calculate the distortion caused by the atmosphere. Tiny mechanical devices mounted behind the flexible mirror make thousands of adjustments per second to sharpen the telescope’s focus.

© Canadian Heritage Information Network, 2003

Altair

Altair mounted on the Gemini North telescope.

Gemini North

© Gemini North.


Adaptive Optics

See how adaptive optics works

One of the instruments in the Gemini instrument cluster is the adaptive optics module. Adaptive optics actually allows us to remove distortions to star light caused by turbulence in the Earth’s atmosphere. Here, we see a model of an adaptive optics system complete with a monitor for watching a demonstration image. After reflecting off of another small mirror, starlight enters the adaptive optics system and a number of things happen. First, the light beam is converted from a cone, to a column of light. It then reflects off a special mirror to a beam splitter, which sends a longer wave-length infrared light to the left to form an image on the monitor. The starlight is really made up of light waves which can be visualized as wave fronts that have been distorted by turbulence in our atmosphere and resemble potato chips and result in a blurry, fuzzy, image. However, the waves of visual light that pass through the beam splitter are analyzed by a device called a wave front sensor, which, with the help of a very fast computer determine the shapes of the waves. This information is sent to the deformable mirror which changes shape up to one thousand times per second to exactly counteract the deformed waves to make them perfectly flat, just as they were before they entered the Earth’s atmosphere. When this light is focused, it forms a nearly perfect image.

Canadian Heritage Information Network

© Canadian Heritage Information Network, 2003


Learning Objectives

The learner will:

  • Develop enthusiasm and continuing interest in the study of science
  • Describe the fundamentals of the light spectrum, and appreciate how this basic knowledge of physical science is being applied to research in astronomy
  • Describe some of the key advances in astronomical technology and their impact on our knowledge of space

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