1. Liquid Telescopes

[rickyjames] Dr. Ashley, it’s a pleasure and an honor to have you as our guest here on SciScoop; thanks for your particiption. I have a couple of questions about specific telescope types; here’s one.

I’ve been very interested in reading over the years about so-called
liquid mirror telescopes, which as you probably know are
revolving circular disks that contain a small amount of
liquid mercury which then spreads out into a near-perfect telescope mirror surface. Their ease of setup and relative low cost is apparently offset by the fact that they can only point stright up and depend on the Earth’s rotation to bring targets into view. Two specialty areas I’ve read about where they might be useful are orbital debris census and extremely deep-field faint-magnitude cosmological surveys.

Questions: What’s your opinions of Liquid Metal Telescopes? Any plans to build one as a permanent observatory to do serious work that you know of? What extra challenges are posed by trying to operate one in cold temps like a mountaintop or someplace like Dome C? Wouldn’t heating them to keep the mercury fluid cause the air to have thermal atmospheric distortions around the mirror?

You might be interested to know that I did some work about 10 years ago for Boeing looking at how to separate minerals from lunar soil and I came up with the idea (never patented, and now I guess it never will be because with this article it’s public domain!) of using a liquid selenium bath on the mooon to separate different mineral grains in lunar regolith. Because of the densities of selenium and the various mineral types, some would sink and some would float. The vapor pressure would be low enough where the system should work in vacuum. Anyway, maybe there’s a future for LMTs based on selenium on the moon someday!

[Ashley] Liquid-mirror telescopes have been imagined for many years, and there are
clever people working on them, e.g., Paul Hickson of the University of
British Columbia who has a concept known as LAMA (Large-Aperture Mirror
Array) made from spinning mercury mirrors (see

http://www.astro.ubc.ca/LMT/lama/index.html). I understand that 6 meter
aperture mirrors have been successfully demonstrated.

Mercury is problematic in Antarctica, of course, since it freezes at about
-39C, whereas the ambient temperature gets down to -80C. If the mirror
were to freeze, it would certainly lose its optical properties. Keeping
the mirror warm would, as you suggest, lead to unacceptable local
turbulence. I believe that some people are thinking about mirrors using
non-metalic fluids that don’t freeze at Antarctic temperatures, and are
covered with a thin reflective layer. To take advantage of the
extraordinarily good astronomical seeing at Dome C we need mirrors of
superlative optical quality, and my impression is that liquid mirrors
won’t be able to meet the specifications.

It is interesting that you mention the moon. Roger Angel gave a plenary
talk at the recent SPIE meeting in Glasgow where he speculated about 20
meter aperture liquid-mirror telescopes on the moon. On the moon you have
the advantage that the lack of atmosphere eliminates the self-generated
winds that otherwise disturb the service of the mirror (see
http://caao.as.arizona.edu/publications/2004%20spie%20plenary%20final%202.pdf).

2. Astronomers: The Next Generation

[rickyjames] Do you think hands-on experience before becoming a professional astronomer is still a major career motivator? If not, what do you think is the current motivator for new youngsters to enter your field of observational astronomy? So much of astronomy now is number-crunching instead of pretty pictures – has this shift changed the kind of people who now take up astronomy as a career? And if someone is going to crunch numbers, why would you say a prospective student should do it for astronomy and not do it for a biotech or drug company that gives stock options?

I ask these questions because I believe the past motivators are becoming increasingly obsolete. Light pollution has dramatically decreased the pool of people who see the wonders and feel the awe of the night sky for themselves, and pictures from Hubble and NASA planetary probes easily available on the internet can make anything an amateur can obtain or see for themselves through a personal telescope seem rather paltry…

[Ashley] There are all sorts of reasons why people go into astronomy as a career, and I don’t really have a good feel as to how this has changed over the
last couple of decades. I followed the “grind an 8-inch mirror, build a
telescope, amateur astronomer” route, and have always had an interest in
the more instrumental side of the subject. While many astronomers do spend
a lot of time crunching numbers, we have the luxury of occasionally
travelling to spectacular places (Chile, Mauna Kea, Antarctica) and using
$100 million telescopes to collect our data. I do worry about the rise in
automated and robotic telescopes, since there is less need to visit the
observatory, so you lose the hands-on experience and you don’t strike up
random collaborations with astronomers that you meet on the mountain.

You are right that light pollution reduces the pool. I am reminded me of a
Japanese astronomy postgraduate student that I drove from Sydney airport
to Siding Spring Observatory some years ago – having spent most of his
life in Tokyo he was staggered by the night sky when we arrived at the
observatory around midnight with the Galactic Center passing right
overhead.

The one motivator that keeps people coming to astronomy is that there
remain lots of big questions to be answered, and there are clearly many
questions that we do not yet know how to formulate. It is not as if we are
just dotting the i’s and crossing the t’s on our understanding of the
universe; we are still scratching the surface of what nature can surprise
us with. Personally, I hope that some of the speculation in Stephen
Wolfram’s recent book “A new kind of science” concerning the computational
nature of reality turns out to be true.

3. Dome A

[Sweetwind] The letter in Nature states “Although it is expected that the turbulence conditions at Dome A, the highest point on the Antarctic plateau at an altitude of 4,200 m, will be superior even to Dome C, the complete lack of infrastructure at this site (it has never been visited) means that Dome C may be a preferable location.” What’s your WAG (wild-ass guess) of the seeing at Dome A? The AASTINO seems to be self-sufficient – it doesn’t rely on any infrastructure from the Concordia station structures – could a Dome A project be done simply (hah!) by moving AASTINO to Dome A?

[Ashley] My suspicion is that Dome A will have similar, perhaps slightly better, seeing to Dome C; I don’t think there is much room left for further
dramatic improvements. The higher altitude of Dome A will certainly lead
to less precipitable water vapour, so the atmosphere will be more
transparent, which is a particular advantage in the infrared and
sub-millimeter where new atmospheric windows will open up. We are applying
for funding to build a new AASTINO to take to Dome A; it would act as a
platform for a planned sub-millimeter experiment called HEAT (High
Elevation Antarctic Terahertz telescope) being led by Chris Walker at the
University of Arizona. It would be challenging to install an AASTINO at
such a remote location, without the logistical support of having Concordia
Station (the French/Italian station at Dome C) a few hundred meters away.
The altitude of Dome A (4084 meters, and effectively higher due to the
reduced air-pressure at the poles), would make it difficult to work there.

4. personal astronomy

[fatoudust] Dr. Ashley, while I follow research astronomy avidly, I always wonder what amateur astronomy the pros do for fun. I as an amateur always wonder what I’d do with pro equipment, but what, if anything, do you pursue on an amateur level with retail equipment? What astronomy do you do for fun outside of your research? Thank you! -Mark Ensley

[Ashley] Quite a few professional astronomers started as amateurs, myself included, and there is a real thrill when you get to use professional equipment. I
vividly recall my experience as a graduate student of a night in the prime
focus cage of the Palomar 5 meter telescope, and peering over the edge of
the cage watching the stars in the primary mirror as the telescope slewed
from one object to another. Using historical telescopes such as the Mount
Wilson 100 inch is quite thrilling. On the other hand, I suspect that few
professionals dabble in amateur astronomy in their spare time, and many
would be unable to locate with binoculars the approximate position in the
sky of objects they have spent their careers studying. It would be
interesting to take a bunch of cosmologists out to a dark site at night
and ask them to point in the direction of the Hubble Deep Field – I
wouldn’t be surprised if the result was isotropic.

5. Long exposures?

[apsmith] One of the advantages of operating at the poles is the months-long winter night. Can a polar optical telescope take advantage of this by running very long exposures to detect very faint objects? Could you do almost as well as the Hubble deep field images? Are there any other practical applications for the potential long exposure times?

[Ashley] This is a very good point, and there has been some discussion of building a simple telescope at Dome C that has a fixed mirror looking at the South
Celestial Pole and that integrates for months. It would need an instrument
rotator to take out the earth’s rotation, but the telescope itself could
be essentially stationary. You could do better than Hubble in some
respects, for example, you could have a much wider field-of-view, and you
could choose wavelengths in the infrared where Hubble doesn’t operate.
Having extremely deep images in multiple wavelengths bands would be very
interesting, and would attract as much interest as the Hubble deep and
ultra-deep fields have done.

6. Holy Grail?

[Drog] What do you think is the holy grail of astronomical observation technology? Is an array of telescopes scattered throughout our solar system feasible, for instance? If so, how (more or less) would it work? How many telescopes would we need and where would we put them so as to produce the best combined images? Would they need to be arranged in the same plane as the planets or could they also be arranged along a perpendicular plane so as to look along the plane of our solar system? What sort of capabilities might such an array give us compared to what we have today?

[Ashley] There is really no limit to what you can imagine in terms of bigger and better telescopes. The photons streaming down on us carry an enormous
amount of information, and it is amazing how much we can learn about the
universe from capturing the ones that fall onto, e.g., an 8 meter mirror.
Astronomers are already seriously thinking about what we could do with a
100 meter mirror. Radio astronomers are talking about square kilometers of
collecting area. But there is plenty of room in the solar system to
imagine much larger instruments! If you can’t afford a filled aperture you
can always try an interferometer; and if you can solve the extremely
challenging technical problems with combining the beams, you could
possibly take photographs of the continents and weather systems on
extrasolar planets. There would probably be advantages in observing
perpendicularly to the plane of the solar system, since that reduces the
amount of “dust” you are looking through.

7. After we find another Earth…

[apsmith] One of your goals for the antarctic telescope is to image extrasolar planets. Do you think we’ll be able to image any that resemble Earth? When that first Earth-like planet is discovered, will it be a bit of an anti-climax, or will space suddenly seem that much more exciting again?

[Ashley] It is technically possible to image earthlike planets from Antarctica, although it will require one or two generations of interferometers before
we reach that goal. Grant applications have been submitted for the
initial steps. I suspect that the first earth-like planet will receive a
lot of publicity, but much as we have become rapidly blase about the 100+
extrasolar planets that we now know, the public interest might be
relatively short-lived. If a planet was close enough to send a spacecraft,
it would add a new dimension. The one event that would really put space
back into the public’s consciousness would be the discovery of an extra
terrestrial civilisation. I hope this happens in my lifetime, but the
chances are probably low.

8. Antarctica – The Next Frontier

[rickyjames] If the Moon or Mars had the exact atmospheric and temperature range as the Antarctic location of your Dome C observation post, there would be a major push on to colonize those habitable areas in space. Why do you think there is no similar romantic notion in the public mind to colonize Antarctica as a new, independent nation of volunteers? Do you suport the eventual opening of Antarctica to international colonization in addition to its current research-only status? Why should we bypass an entire continent with miles-deep water ice and breathable air to go to places vastly farther away and vastly more expensive to reach that offer only vacuum or near-vacuum with meager surface frost and tundra?

[Ashley] While it would clearly be much easier to colonise Antarctica than it would the moon or Mars, there really wouldn’t be much point. The advantage of
colonising another planet is that it gives some insurance against global
catastrophes. I wouldn’t advocate an expansion of human occupation in
Antarctica, since I think that humans have a well-established tendency to
mess things up. If anything, I think we should be exploring ways of having
an enduring civilisation on earth with perhaps 1/10 or 1/100th the number
of people that we currently have. Our current reliance on growth will
inevitably fail.

9. What else is interferometry good for?

[Sweetwind] What other kinds of science, besides extra-solar planet search, are the large-scale interferometers (as discussed in your
FAQ) good for? Is planet search your particular interest?

[Ashley] Interferometers are good for observing bright, small, objects at very high-resolution. It would be fascinating to peer into the central engines
of active galaxies and see material being sucked into a black hole; or to
study the detailed evolution of proto-planetary disks around newly formed
stars. While I am involved in a couple of planet-search experiments, I am
always on the look-out for new ideas, particularly those involving
innovative instrumentation.

10. Pre-CV History

[Sweetwind] Dr. Ashley, thanks again for agreeing to this interview! And now for the more personal side of astronomy: are you originally an Australian? If so, whatever prompted you to trek all the way to Caltech for your master’s? If not, how did you end up in Australia?

[Ashley] I’m originally an Australian, and still am! After finishing my
undergraduate degree at the Australian National University I felt that I
needed to see a bit of the world, and my reading showed that Caltech had
an OK reputation! I started a PhD there in 1981, and while I really
enjoyed the science and being able to take courses and attend lectures
from some of the world’s leading researchers, the 90% male population was
a shock after the healthier social environment at ANU. So I decided to
convert to a Masters, and returned to Australia for my PhD. Things worked
out well, and I have had many trips back to the US to collaborate with
various people across the country.

11. Planetary Searches Via Photometry At Dome C

[rickyjames] Another robotic Antarctic telescope effort is
Vulcan South. Have you ever met or been in contact with the crew of the Vulcan telescope? Any idea how their effort is going, or if your results are influincing their efforts? Please comment on whether Dome C would have advantages over other Antarctic locations for attempting to find transiting planets via continuous high-resolution photometry.

[Ashley] In fact, I’m a collaborator on the Vulcan South experiment, and was at the South Pole earlier this year helping the team install the telescope.
Unfortunately, we had an instrumental problem in the CCD camera that
prevented us from getting any data this year. The camera will be shipped
back to the States for repair within a few days of the first flights to
the Pole, expected shortly. The South Pole is better in some respects than
Dome C for this experiment since the stars stay at a constant elevation,
which eliminates many systematic effects. On the other hand Dome C appears
to have less cloud, and certainly has lower winds, which makes it easier
to operate and repair instrumentation during winter.

Thank you for the opportunity to participate in this interview!