European Extremely

Large Telescope (E-ELT)

Natali Kuzkova

13th January 2015, Ph.D. seminar

The E-ELT will be the largest optical/infrared telescope in the world is the world's biggest

eye on the sky and will gather 13 times more light than the largest optical telescopes

existing today. The E-ELT will be able to correct for the atmospheric distortions from the

start, providing images 16 times sharper than those from the Hubble Space Telescope.

Currently being built by the European Southern Observatory (ESO) on top of Cerro

Armazones in the Atacama Desert of northern Chile.

The design comprises a reflecting telescope with a 39.3-metre-diameter segmented

primary mirror, a 4.2-metre-diameter secondary mirror, and will be supported by adaptive

optics and multiple instruments.

It is expected to allow astronomers to probe the earliest stages of the formation of

planetary systems and to detect water and organic molecules in proto-planetary discs

around stars in the making.

Bild

Construction start: July 2014

Planned completion: 2022

First light: 2024

Introduction

Four Centuries of the Telescope —

Four Centuries of Discovery

Over the last 60 years, astronomers have developed telescopes that are able to observe right across the

electromagnetic spectrum. Space observatories have allowed observations to be pushed to shorter wavelengths, into the ultraviolet, X-ray and gamma-ray regimes. This opening up of the high energy frontier generated a further flood of discoveries such as X-ray stars, gamma-ray bursts, black hole accretion discs, and other exotic phenomena. Previously unknown physical processes were taking place in the Universe around us. These discoveries led to a number of Nobel Prizes in Physics (in 1974, 1978, 1993, 2002 and 2006) and to giant leaps in our understanding of the cosmos. The first exoplanets were detected, and the current generation of 8–10-metre class telescopes even allowed us to take the first pictures of a few of these objects.

• In 1669, a few decades after the invention of the refracting

telescope, a design based on lenses, Isaac Newton

introduced the first practical reflecting telescope, using

mirrors. Over the following 300 years, these two telescope

design concepts competed and evolved into ever more

powerful research facilities. Refractor technology peaked

towards the end of the 19th century with the big Lick and

Yerkes Refractors, which used lenses of 90 centimetres and 1

metre in diameter, respectively. However, these lenses and

their supports proved to be the largest that could practically

be constructed, and thus reflecting telescopes finally won the

day.

• Reflecting telescopes in the 19th century suffered from the

poor reflectivity and thermal properties of their mirrors.

Despite this limitation, William Herschel and William Parsons,

the third Earl of Rosse, were able to build reflectors with

diameters ranging from 1.25 to 1.80 metres, with which they

discovered more planets and moons in the Solar System,

expanding the boundaries of the then known Universe further.

E-ELT compared to other ELTs ) )

) ) ) )

Diameter: 24 m

Collecting Area: 400 m2

Diffraction limit at 1μm: 9 mas

Planned in 2020

Diameter: 24 m

Collecting Area: 400 m2

Diffraction limit at 1μm: 9 mas

Planned in 2020

Diameter: 30 m

Collecting Area: 600 m2

Diffraction limit at 1μm: 7 mas

Planned in 2020

Diameter: 30 m

Collecting Area: 600 m2

Diffraction limit at 1μm: 7 mas

Planned in 2020

Diameter: 40 m

Collecting Area: 1000 m2

Diffraction limit at 1μm: 5 mas

Planned in 2020

Diameter: 40 m

Collecting Area: 1000 m2

Diffraction limit at 1μm: 5 mas

Planned in 2020

Existing Very Large Telescope (VLT) is a complex of four separate 8.2-meter optical

telescopes. Discoveries with ground-based telescopes such as ESO’s VLT and its

VLTI, and other 8–10-metre class telescopes will have prepared the scene for further

fascinating discoveries with the E-ELT.

) )

Diameter: 4 x 8.2-metre Unit

Telescopes, plus 4 x 1.8-metre

moveable Auxiliary Telescopes

Operating since 2012

Diameter: 4 x 8.2-metre Unit

Telescopes, plus 4 x 1.8-metre

moveable Auxiliary Telescopes

Operating since 2012

Evolution of the telescopes • Comparison of nominal sizes of primary mirrors of some notable

optical telescopes:

The star symbols mark refracting telescopes, asterisks

stand for speculum reflectors, circles for glass reflectors. http://www.eso.org/sci/facilities/eelt

European Extremely Large Telescope

Name: European Extremely Large Telescope

(E-ELT)

Site: Cerro Armazones

Altitude: 3060 m

Enclosure: Hemispherical dome

Type: Optical/near-infrared Giant Segmented

Mirror Telescope

Optical design: Five-mirror design: three-mirror on-axis

anastigmat + two fold mirrors used for

adaptive optics

Diameter. Primary

M1:

39 m (798 hexagonal 1.4 m mirror

segments)

Diameter. Secondary

M2:

4 m

Diameter. Tertiary

M3:

3.75 m

First Light date: Early 2020s

Active Optics: Yes

Adaptive Optics: 2.60 m adaptive M4 using 6 Laser

Guide Stars

Open questions for E-ELT

Extra-solar planets

Discovering and characterizing planets and proto-

planetary systems around other stars will be one of

the most important and exciting aspects of the E-

ELT science programme.

This will include not only the discovery of planets

down to Earth-like masses using the radial velocity

technique but also the direct imaging of larger

planets and possibly even the characterization of

their atmospheres.

The E-ELT will be capable of detecting reflected light

from mature giant planets (Jupiter to Neptune-like)

and may be able to probe their atmospheres through

low resolution spectroscopy.

The radial velocity technique, which measures the induced Doppler

shift of features in the spectrum of the parent star, can only find certain

kinds of planets. With the current generation of telescopes, this

technique is limited both by the precision and the stability of the

velocity measurements: current measurements have pushed the limit

down to an already impressive ~1 m/s precision retained over several

years. The radial velocity technique — reaching 1 cm/s accuracy.

More than 400 exoplanets have been found so far. With the E-ELT,

the sensitivity of the radial velocity method will be improved by a

factor of 1000.

Open questions for E-ELT

Cosmology and fundamental physics

The discovery that the expansion of the Universe

has recently begun to accelerate, presumably driven

by some form of dark energy, was arguably one of

the most important as well as mysterious scientific

breakthroughs of the past decade.

The E-ELT will help us to elucidate the nature of dark

energy by helping to discover and identify distant

type Ia supernovae. These are excellent distance

indicators and can be used to map out space and its

expansion history.

In addition to this geometric method the E-ELT will

also attempt, for the first time, to constrain dark

energy by directly observing the global dynamics of

the Universe: the evolution of the expansion rate

causes a tiny time-drift in the redshifts of distant

objects and the E-ELT will be able to detect this

effect in the intergalactic medium. This

measurement will offer a truly independent and

unique approach to the exploration of the expansion

history of the Universe.

A simulation of the accuracy of the redshift drift

experiment, which will be achieved by the E-ELT. The

results strongly depend on the number of known bright

quasars at a given redshift.

The ultra-stable high resolution spectrograph proposed for the E-ELT will essentially remove the systematic uncertain-

ties due to the wavelength calibration which plague current measurements. It will improve the constraints on the stability

of fundamental constants by two orders of magnitude. These fundamental quantities include the fine structure constant,

α, and the strong interaction coupling constant, μ.

Resolved stellar populations in a representative

sample of the Universe

The E-ELT offers the exciting prospect of reconstructing the

formation and evolution histories of a representative sample of

galaxies in the nearby Universe by studying their resolved stellar

populations.

A galaxy's stellar populations carry a memory of its entire star

formation history, and decoding this information offers detailed

insights into the galaxy's past. However, studying stellar

populations requires the capability of resolving and measuring

individual stars and so up until now such studies have been

limited to our own Galaxy and its nearest neighbours. In

particular, no examples of large elliptical galaxies are within

reach of current telescopes for this type of study.

With its superior resolution and photon collecting power the E-

ELT will allow us to perform precise photometry and

spectroscopy on the stellar populations of a much more

representative sample of galaxies, reaching out to the nearest

giant ellipticals at the distance of the Virgo cluster.

Thus, the E-ELT will provide detailed information on the star

formation, metal enrichment and kinematic histories of nearby

galaxies, showing us how they were formed and built-up over

time.

Open questions for E-ELT