Mountaintop and Extremely Large Telescope

[eigoya]

Article on the E-ELT going up in Andes and wondered if anyone knowledgeable could comment on the parallels to oThe Big Island's TMT. http://www.theguardian.com/science/2014/...?CMP=fb_gu

[TomK]

That's a very open-ended question, but in case you are worried the TMT will not be blowing up the summit of Mauna Kea. There are very different rules here compared to Chile.

[eigoya]

Yes I kept the question broad because I don't know much. Will these be looking for/at the same things? I was surprised at the timeline, 2024, which seems a long way out to the non-physicist. Are they the same size? How will they complement or compete? I didn't think we'd take off our mountain or there'd be even more uproar than we have currently.

[Derrick Barnicoat]

What boggles my mind is if the telescope is seeing light from millions of years ago can it actually show signs of current life on other planets? Or is it showing signs of life that happened millions of years ago?

[pahoated]

E-ELT is at less than 10,000 feet, Mauna Kea is 14,000 feet. E-ELT is in the Atacama desert, far south of the equator, so its field of view is the southern sky. This is an important development because most astronomy has been done from the northern hemisphere due to previous telescopes being in northern industrial areas.

While deep space astronomy will go on, the heightened interest is to actually image planets in other solar systems, mainly searching for earth-like planet around a yellow star. This search is visual, so it has to be for nearby star systems. It hasn't been determined if there is a rocky planet around Alpha Centauri B (4.5 light-years)due to the binary star system making confirmation difficult. Beyond that is Barnard's star (6 light-years) and it's been confirmed there is no earth-like planet there. The next closest star with a confirmed planet is Epsilon Eridani (10.5 light-years). The star is slighty smaller and older than Sol, and a gas giant planet has been confirmed, with good chances for having smaller rocky planets in inner orbits.

That E-ELT is a massive engineering project in a remote location, that is why it will take 10 years to build it. The Thirty Meter Telescope TMT should be finished first by a couple years.

"This island Hawaii on this island Earth"

[TomK]

Eigoya - as ever with projects like the TMT and ELT, the answers are complex. Both telescopes will have similar capabilities and both are designed to work in the same wavelength regime, i.e., visual and infrared light. The ELT will be slightly larger than the TMT resulting in a much larger collecting area for light. Usually that means the telescope will result in more sensitive observations and being able to detect fainter objects, although it isn't as simple as that. Despite being smaller, the TMT will win out on looking at single objects because of its optics whereas the ELT will win out looking at several objects in one go. So it depends on what science project is actually being done and that makes saying which is better very complicated.

The ELT will be built on a site that has slightly better seeing in visual light compared to Mauna Kea. Seeing is a measure of the detail you can resolve or see in images so it should win out there. On the other hand, the ELT will be at a lower altitude than the TMT, which means there will be more water in the atmosphere above the TMT and water makes infrared observations harder. In that case the TMT should win out - Mauna Kea is probably the second best currently used astronomical site for infrared observing. Only Antarctica is better.

ELT will be in the southern hemisphere, TMT in the north, so they will have access to different parts of the sky although there will be some overlap. The southern hemisphere is better for Galactic observations, the northern for extra-galactic. The telescopes will also only have access to their use to certain countries although there will be, no doubt, collaborations set up that will use both telescopes.

In summary, they are similar telescopes, with pros and cons for each if you're talking about competing, but will also complement each other because although they will be concentrating on some different areas of science, they will be doing slightly different ways of doing the same science. Unfortunately it will take time to build them, remember these are enormous instruments yet have to be built with a precision of microns on remote sites in difficult environmental conditions.

Personally I'm glad we will have two large telescopes, one in the south and one in the north. Imagine only one being built, say in Chile, and then some remarkable astronomical event happens in the northern sky, e.g., a Galactic supernova (we've been waiting for one of those for a long time now). Although we have several telescopes in the north, a large telescope like the TMT or ELT would be able to observe it like no other telescope has before (we're talking 15 times better resolution than the Hubble Space Telescope). It'd be a shame to miss that opportunity to understand our Universe just a little better.

[TomK]

Derrick - I'm not really sure what your question is, but no telescope has yet detected signs of life on other planets. However, light takes a finite time to get here from other stars and planets, so whatever is detected happened some time ago, and that time is dependent on how far away the light started its journey toward us.

[rainyjim]

Derrick, I think what you are referring to is the potential for G type stars (like our Sun)to have orbiting planets in the "goldie-locks" zone.

So far we have no way of knowing for sure. But you should read up on NASA's findings of potentially possible life on Titan one of Saturn's moons.

It is much closer and we can observe what is happening on the surface a lot easier than say Tau Ceti or Alpha Centari (other G - type stars)

[Derrick Barnicoat]

Yes I have heard about how planets in the "goldie locks " zone can be detected by the wobble of stars but in the article linked above they are saying that this telescope will be used to detect life on other planets, perhaps they mean potential for life on other planets, but it also says talks about seeing light from the earliest stars.

Here's the quote:

"That is large enough to see the faintest light from the earliest stars, and pick up signs of life on planets far beyond our solar system."

Anyway, I was thinking this sounds strange, being that anything this telescope is picking up probably occurred thousands if not millions of years ago and in actuality some of those planets or stars may not even exist currently because anything could happen in that kind of time frame. Anyway, I guess they are just trying to get people excited about the telescope. The truth is they are really just looking for the potential for life on other planets.

[pahoated]

The astronomers are talking about being able to resolve visually to the atmosphere resolution with the new telescopes, only for those possible rocky planets a relatively short distance away. So, the time lag is generally going to be less than 100 light-years, not millions of light-years. Take the Sun, put it at an imaginary center, the new telescopes will be sweeping in a spherical distance area, possibly out to 200 light years. This will only be for their planet searching job, they will have a universe full of other jobs. And it will be great that TMT will be north of the equator and E-ELT will be south of the equator. That has to increase the sweep area by a huge amount.

E-ELT faces some huge construction hurdles. They don't have EIS to deal with but those mirrors are made out of sections, unbelievably precise and fragile. They have to be shipped in to the nearest port, then trucked all the way into some of the most remote area on the planet, driven up to the top of the mountain and final assembly requiring precision to the thousandths of a millimeter. They have over 270 sections. Would not want to be in charge of that job.

"This island Hawaii on this island Earth"