Albert Einstein published his General Theory of Relativity in 1916. One aspect of the theory predicted that light passing near a massive object would be deflected slightly in direction. Light originating from a distant bright source such as a quasar could travel by a massive object such as a galactic center and change direction. The observer would see the image of the distant source in slightly different places.
Not to scale.
Of course, such a prediction deserved to be tested. In 1919, astronomer Arthur Stanley Eddington headed a team to observe a star closely aligned with the Sun that would be visible only during a total eclipse. The star’s known position should be shifted according to the theory. Their observations confirmed that Einstein was correct.
What is an Arp? Good question. Arp is the last name of Halton Arp. He compiled the Atlas of Peculiar Galaxies containing 338 entries published in 1966 by the California Institute of Technology. A goal was to show images of the peculiar structures found among some galaxies.
Among the billions of galaxies known, a few are in some stage of collision with another. Such a rare event disrupts the original shapes of the colliding galaxies. Collisions take a long time to occur. This image of atlas entry number 220 shows the result of two galaxies in collision. The brown dust lanes hide much of the detail behind the dust. It is a chaotic scene.
Hubble Legacy Archive | My version
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Hubble telescope imaged a small part of the Carina Nebula in the southern skies. My color rendition here used 3 grey-scale images from the Hubble Legacy Archive. It outlines the edge of a very small part of the nebula.
Hubble Legacy Archive | NGC 3324 | My version
Like many people these days, I have a lot of spare time. One project I enjoy is taking three grey-scale images from the Hubble Telescope archive and combining them to produce color versions. The Hubble Legacy Archive (HLA) collects the vast array of images from the telescope into a searchable site available to the public. Knowing the name of the object or keywords, one can search for images made by a variety of instruments and filters.
The oval object below is an unusual galaxy called the Cartwheel. It was imaged with a grey-scale sensor as the light passed through a green wavelength filter. Imaging was also done with red and blue wavelength filters not show here. But, they look similar.
Hubble Legacy Archive
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The sun’s output in the visible spectrum peaks around yellow. Our eyes are most sensitive to that part of the visible spectrum. The sun also radiates in a broad range of other wavelengths invisible to our eyes. Each comes from dynamics taking place on the surface and in the atmosphere of the sun.
I’ve written about NASA’s Solar Dynamics Observatory (SDO) earlier in a previous post. SDO observes and images the sun several times a minute at ten different wavelengths to give a more complete picture of the activity at and near the surface. A description of those wavelengths is available here. I used the images from the SDO site to render this image of the sun at those ten wavelengths. The yellow center represents the sun’s surface. Each ring of color is at a higher altitude and temperature in the atmosphere of the sun.
Original images used from: NASA/GSFC/Solar Dynamics Observatory
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