Author Topic: Interferometric imaging  (Read 717 times)

Online savuporo

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Interferometric imaging
« on: 09/02/2017 06:57 PM »

https://www.eso.org/public/usa/news/eso1726/

Quote
Using ESO’s Very Large Telescope Interferometer astronomers have constructed the most detailed image ever of a star — the red supergiant star Antares. They have also made the first map of the velocities of material in the atmosphere of a star other than the Sun, revealing unexpected turbulence in Antares’s huge extended atmosphere. The results were published in the journal Nature.

To the unaided eye the famous, bright star Antares shines with a strong red tint in the heart of the constellation of Scorpius (The Scorpion). It is a huge and comparatively cool red supergiant star in the late stages of its life, on the way to becoming a supernova [1].

A team of astronomers, led by Keiichi Ohnaka, of the Universidad Católica del Norte in Chile, has now used ESO’s Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile to map Antares’s surface and to measure the motions of the surface material. This is the best image of the surface and atmosphere of any star other than the Sun.

The VLTI is a unique facility that can combine the light from up to four telescopes, either the 8.2-metre Unit Telescopes, or the smaller Auxiliary Telescopes, to create a virtual telescope equivalent to a single mirror up to 200 metres across. This allows it to resolve fine details far beyond what can be seen with a single telescope alone.

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Online KelvinZero

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Re: Interferometric imaging
« Reply #1 on: 09/03/2017 10:32 PM »
Wow. That is awesome. Are we soon going to be seeing the round disks of planets passing in front of stars?

Im not sure if this is related, but I was looking for somewhere to ask if something like Interfeometry could detect the direction of motion of a planet's shadow. Or if you could just have two normal telescopes far enough apart that they detect dimming at slightly different instants.

Of course if you are actually seeing the disk of the star, and the disk of the planet passing in front, you have gone well beyond this.

Online savuporo

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Re: Interferometric imaging
« Reply #2 on: 09/03/2017 10:57 PM »
Wow. That is awesome. Are we soon going to be seeing the round disks of planets passing in front of stars?

That does appear to be the hope
http://spie.org/newsroom/6504-kilometer-baseline-optical-intensity-interferometry-for-stellar-surface-observations

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Offline Bynaus

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Re: Interferometric imaging
« Reply #3 on: 09/04/2017 06:26 AM »
Im not sure if this is related, but I was looking for somewhere to ask if something like Interfeometry could detect the direction of motion of a planet's shadow. Or if you could just have two normal telescopes far enough apart that they detect dimming at slightly different instants.

Challenging. Shadows of transiting planets travel at superluminal speeds (and no, we cannot use this to send signals with superluminal speeds ;) ). Say you have an Earth analogue orbiting a sun-like star 30 LY out. Then, the planet moves at about 30 km/s at 1 AU from its star, but translated to 30 LY away (= ~2 M AU), this corresponds to ~200 c! So in other words, even if the two telescopes were the width of the Earth's disk apart (12'756 km), so the shadowing would start about 0.04 ms apart. Now remember that transits are typically noisy, ingress into and egress from a transit typically take a few minutes, and that the time of integration (even for the short-cadence data of Kepler) is at least a minute, and you know what I mean by "challenging".

Edit: edited because the Earth's disk is of course not 40'000 km wide. Doesn't change the argument though.
« Last Edit: 09/06/2017 06:11 AM by Bynaus »

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