A marriage made in CLEO: astronomy/physics and photonics

My love for the stars is not new to some of you. So the tone of this post should not be a surprise.

At CLEO amongst other talks and sessions was a special symposium on

Advances and opportunities in Astro Photonics, JF1N. There were two particular talks that really caught my attention:

The first invited talk (JF1N.1) was by Olivier Guyon titled, “Where are our closest neighbours? Looking for life in nearby exo-planets”.

Exo-planets! Do you need to say even one word more to catch the interest of the people? For sure I was hooked by the title alone and the talk delivered. Some interesting facts that was thrown up in the talk included that about 10% of stars have potentially habitable planets around them. By habitable we mean a mass similar to the Earth and distance that is similar to the Earth from the sun, placing these planets in the habitable zone because that temperature would allow life and may enable liquid water to exist on the planet surface as well.

As the speaker pointed out the question is not if there is life out there but how close it is to us so we know where to look so we know where to look.

He then went on to talk about diff to talk different planet detection techniques: those that are indirect such as astrometry and radial velocity based and those that are direct.

The trouble with direct detection via telescopes on Earth is that the planets are so close to the star (angular separation over this huge distance is very small) that the light from the star far outshines the light reflected by the planet making it virtually invisible. This means we need other more clever ways of finding planets which obviously do not emit their own light.

Radial velocity has thus far been the most successful indirect technique in detecting exoplanets. It relies on the fact that a star also feels the gravitational tug of the planet/s orbiting it and executes motion along an orbit. The change (blue/red) shift of its spectral lines due to the Doppler effect in this orbital motion can be used to detect the presence of the exoplanet.

This technique would detect large planets close to the star in a short orbit, causing a wobble that is detectable. But such large planets close to the star are unlikey to host life. So other techniques are needed to detect smaller planets in the habitable zone.

Astrometry the second technique discussed is where photonics will come in! The technique  relies on the motion of the star changing (a slight wobble if we plot the  projection of its motion around its centre of mass) and detecting this wobble. This would be of the order of a few micro arc seconds while ground based telescopes have detection capability of say half an arcsecond. Theoretically increasing the diameter of a telescope would make it capable of measuring smaller wobbles, but atmospheric turbulence decreases this. Use of adaptive optics is one way to combat it! As well as use of interference with astrometry in the VLTI.

I will blog about the second talk another day. Meanwhile happy reading on astrometry and astrophotonics!!

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By artiagrawal Posted in General

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