Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: hamdani yusuf on 21/04/2020 06:16:10
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(https://physicsworld.com/wp-content/uploads/2020/04/Eta-Carinae-635x644.jpg)
https://physicsworld.com/a/hubbles-best-shots-eta-carinae/
Hidden beneath the expanding lobes of gas and dust in this multi-wavelength view is one of the most massive and volatile stars in the Milky Way. Eta Carinae was just another nondescript star until 1843, when it underwent a dramatic outburst and briefly became the second-brightest star in the night sky. It’s unclear exactly what prompted this explosive episode, but we do know that Eta Carinae – actually a double star system concealed at the epicentre of the two lobes – shed an enormous amount of mass from its outer layers in the process.
Hubble’s false-colour image combines visible light observations by its Wide Field Camera 3 with ultraviolet-light data from the its Ultraviolet Imaging Spectrograph. It shows the presence of gas – magnesium in blue, and shocked nitrogen gas presented here in red – that could have been ejected by the star shortly before its outburst, and which could therefore provide clues as to what caused the tumultuous eruption.
In the picture above we can see a lens flare effect with some sort of interference pattern. What causes this? is it because of some defect in Hubble's lens?
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lens flare effect
Are you referring to the blue-ish "star" shape around the stars?
A cross shape around stars in telescope images is fairly common - there is often a cross-shaped brace to hold the primary-focus mirror in a reflector telescope like Hubble.
- Despite attempts to make this brace as "black" as possible, light still refracts around it, leading to the cross shape.
- But this shape looks more complex than a simple cross.
This might be due to the ultraviolet imager, which probably has lower resolution than Hubble's visible-light telescope.
- I image that in aligning the visible-light and ultraviolet images, they would have used a "sharpening" filter on the ultraviolet images to improve the resolution closer to the visible-light image
- But sharpening leaves behind artifacts
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I think the cross is, as you say, from the spider that holds the mirror in place.
And I suspect that much of the distortion of the stars is due to diffraction.
https://en.wikipedia.org/wiki/Airy_disk
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And I am still under the impression of the “Pillar of Creation” picture better than we could even dream of.
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And I am still under the impression of the “Pillar of Creation” picture better than we could even dream of.
Do you have any particular reason or is it just a gut feeling?