Slashdot Mirror

Chrome plating is only about 70% reflective. A bathroom-variety mirror is only about 75% reflective. The remaining 25%-30% of energy from the laser would be absorbed by the drone as heat. Aluminum coatings used on telescope mirrors can get to about 90% reflectivity, about 98% with good coatings. But that's at a specific wavelength (visual spectrum), and they're very delicate (only about 100 nm thick) and degrade as cruft settles on them. That's why electroplated chrome is more popular for decorative reflectivity - it's much more durable. (Silver actually has better reflectivty, but it quickly tarnishes upon contact with the air. Aluminum does too, but the resulting aluminum oxide is transparent in the visible spectrum and forms an airtight barrier protecting the remaining aluminum.)

So all a mirrored drone would do is increase the amount of time it takes for a laser to shoot it down. If drones did start to go that route, the obvious countermeasure would be to make the laser more powerful. It's a lot easier to make the laser bigger than it is to keep the mirrored surface of a drone pristine.

Unrelated trivia: The best reflective surface is actually a prism, which relies on a phenomenon called total internal reflection - the same property which makes optical fibers work. Their biggest losses are actually at the air-prism interface where the light enters and exits the prism - typically 99.7%-99.8% transmission. They're highly directional though, so (unless someone can come up with an extremely clever design) wouldn't work omnidirectionally.

I'm stuck spending the night at an 8.3-meter with a bunch of people who're tinkering with something called "Visible Aperture Masking Polarimetric Interferometer for Resolving Exoplanetary Signatures” - VAMPIRES for short. Unfortunately, we're not lasering the moon, or doing spectroscopy of it during totality like we did last eclipse (you can measure elemental abundances and pollutants in Earth's atmosphere that way, nifty). But at least we're somewhere that it all happens 2 hours earlier in the evening than on the west coast. :)

Our current-generation workhorse instruments here at the telescope spit out tens of gigabytes per night as it is. The new camera we've been commissioning produces something like two gigabytes per exposure. And oh, yes, that data has to be archived, reduced, analyzed, etc., using things like IRAF or IDL. (Not my job.)

19-micron pixels seem big if you're comparing them to DSLRs, where everything has to fit into a nice little portable package. But it's not at all an unusual size in science-grade detectors used for astronomical instrumentation. At work our instruments use detectors with pixel sizes ranging from 13.5 to 50 microns.

I might be a little more impressed that they're doing this at video frame-rates, and without cryogenics...

19-micron pixels seem big if you're comparing them to DSLRs, where everything has to fit into a nice little portable package. But it's not at all an unusual size in science-grade detectors used for astronomical instrumentation. At work our instruments use detectors with pixel sizes ranging from 13.5 to 50 microns.

I might be a little more impressed that they're doing this at video frame-rates, and without cryogenics...

You can use earth-based telescopes with a similar sort of trick to study Earth's atmosphere, of course. At work last December, we had astronomers using an 8-meter telescope to do high-res spectroscopy of the light reflected off the moon during a total lunar eclipse, since during totality that light has all passed through Earth's atmosphere.

Nice sky there! I've been aware of Hanle/Mt. Saraswati for a while, because it's one of the three observatory sites in the world (the 5000m part of the Atacama Desert in Chile and ~4300m Mt. Evans outside Denver are the other two) that are higher than Mauna Kea (where I work and sometimes take pretty pictures), but this is the first picture I've seen of the night sky there. If I ever get back to India, I want to go there, instead of hanging out in Delhi again. :)

In countries were [sic] people earn a few $1,000 a year or even a few hundred, I don't see how Apple could make a product cheap enough to make $$.

I spent 2 weeks in Uganda at the beginning of this year. (There was a nice annular solar eclipse.) Per-capita GDP is about $1,300. Of course, that's an average - some folks make less, some make more - and includes kids and whatever.

Anyway, anyone who makes enough above that average has an iPod. At least a shuffle or a nano. People who can afford one - say, managers - have an iPhone 3G S. There are ads for the iPhone all over Kampala. There's an Apple authorized reseller downtown.

There's also a lot of counterfeit product from China in the market, which is a lot cheaper and typically breaks after a few months. It's interesting to go to a market that doesn't have the level of IP law and trade regulation in place that the US does.

Others have pointed out that the Hubble deep fields don't include galaxy clusters. I'll add that the Subaru/XMM-Newton Deep Survey doesn't go quite as deep as Hubble (Hubble goes to around magnitude 29, SXDS only to magnitude 28)... but it covers an area of sky 1,000 times larger than Hubble's deep field.

can this be right ?
"The size of each knot is about five times as big as Pluto's orbit in the Solar System"

ie, that the size of each of those little knots is 5x the size of our entire solar system ? wow.

from http://www.naoj.org/Pressrelease/2009/07/02/fig2.jpg and http://www.naoj.org/Pressrelease/2009/07/02/fig4.jpg i would estimate the size of the entire nebula to be about 400 to 500 times the size of the solar system.

can this be right ?
"The size of each knot is about five times as big as Pluto's orbit in the Solar System"

ie, that the size of each of those little knots is 5x the size of our entire solar system ? wow.

from http://www.naoj.org/Pressrelease/2009/07/02/fig2.jpg and http://www.naoj.org/Pressrelease/2009/07/02/fig4.jpg i would estimate the size of the entire nebula to be about 400 to 500 times the size of the solar system.

http://www.naoj.org/Pressrelease/2008/12/03/index.html

As the article suggests, the biggest benefit of using light echoes is that the SPECTRUM of the original supernova can be obtained. In other words, while today we mostly see the direct-path light emitted by the supernova's gas remnant, light echoes let us see all the wavelengths of the light emitted at the time of the explosion.

Alejo

Here are the press release links: Nature, Hubble Space Telescope, European Space Agency and Subaru Telescope. The COSMOS project web page can be found there.

The original article is, of course, here.
I'd like to see science news announced here by quoting the original source rather than a news company.

Arecibo Observatory is still the biggest single telescope, though there are even larger arrays.

In particular, there seems to have been an agreement made some years ago between whatever entity handles the summit for astronomy (probably the University of Hawaii Institute for Astronomy) and some native groups (mountaintops are sacred places) under which the astronomy folks got permission to build a certain number (int) of telescopes.

That many have now been built. The astronomy folks would like to build more. And... various folks (natives and others) are noting that um, no, that's not what they agreed to. So there's been a lot of paperwork, environmental impact statements, and so on.

In some cases, things are a little grey-area-ish. They want to build "outriggers" on the sides of the Keck scopes, for example. And the Smithsonian-Sinica.tw-Harvard submillimetre array - does that count as 8 scopes, since there are 8 dishes, or 1, since it's an interferometer?

As it now stands, though, Mauna Kea wins lots of astronomy pissing matches. :) It has the 2 largest optical scopes in the world (Keck and Keck II), plus the 4th largest (Subaru) and another in the top 10 (Gemini North), the largest single submillimeter telescope (James Clerk Maxwell) and I think the largest dedicated infrared telescope (UKIRT).

If someone wanted to build a truly monster scope on Mauna Kea, they could simply remove one of the small ones, it would seem. University of Hawaii has an 0.6-metre one and a 2.2-metre one. (Yes, those are "small," all you backyard astronomers who are now drooling. ;) Take out the 0.6 and replace it with a 30-metre one, and you haven't changed the number of telescopes, right?

Other solution: double up on observations. Different recievers can be attached to a telescope. IR, ultra-violet and visible can be observed at the same time.

Not easily: much of the UV window is very strongly absorbed by the atmosphere, so you can't use it from ground-based telescopes anyway and have to use spacecraft. It's also not so easy to observe two wavelengths at once: you need a lot of complicated optics, and you don't want to waste any of those precious photons. In addition, if the wavelengths are very different, you could have very different design requirements on the rest of the telescope.

So why not double up one projects that are located in the same space in the sky.

They'd have to be really close in the sky. It works for some projects where you're looking at a sample of objects in a patch of sky, like the Hubble Deep Field. However, for many instruments on telescopes like the Keck and Subaru, the field of view is less than 30 arcminutes, which is only the angular diameter of the full moon. Also, the instrument and observing mode you use are strongly dependent on exactly what sort of object you are investigating, and how, and may not be suitable for anything else that happens to be in the field of view.

Also, with image enhancement, you can look at a wider section of sky and view multiple objects, while using computers to examen your specific project.

Image processing and general number-crunching are essential to astronomers already, in order to transform raw data into a final image ("data reduction"). I spent the majority of my Ph.D. working on ways to process a particular type of data, so we're already doing what we can. :-)

Essentially, research-class telescopes are all oversubscribed, and so people tend to make whatever optimisations they can already.

"...basically, if we see something coming in the next century, we're fucked."

Actually, if we had a decade's notice, we could probably alter the trajectory of the object enough so that it would miss earth entirely. The whole blowing up the object theory is total crap. It is true, however, that the timeframes given in movies like Deep Impact and Armageddon are too short for action given our current technological state. It is interesting to note that the Orion system used in Deep Impact has already been invented (in theory), but the use of nukes in space is banned by international treaty.

"...Advances in energy and kinetic weapons that could allow us to pulverize a potential threat while still several AU away. Multiple large Hubble-like detectors scanning the heavens."

I generally agree with your line of reasoning, but I just wanted to point out that an object "several AU away" wouldn't reach us any time soon... at the very least not in the next few centuries. Also, it would be much more feasible to construct more ground-based telescopes like the Subaru, which is more powerful than the Hubble anyway.

The article really plays down the chances of a sizeable celestial object colliding with the Earth. The chance that any specific object will collide with the Earth is astronomically small to say the least. The chance that any object will collide with the Earth, however, is not calculable given the amount of data we possess about intrasolar/near extrasolar objects. I interned at the Subaru telescope, and someone in control of that organization must feel that the threat of an Earth impact is significant because although the telescope can take clear pictures (I have one, but it was given to me on the condition that I not distribute it) of large stellar objects 50 billon lightyears away (while only halfway calibrated!), it is being used primarily for near-solar and intrasolar observation. To put that kind of magnification power into perspective, I was told that the telescope could clearly identify a car, allowing you to determine the model and year if it were floating in the asteroid belt. You could alternatively read the label and judge the depth of the dimples on a golf ball if it were sitting on the summit of Mt. Fuji (the telescope is in Hilo, Hawaii). The only reason you need something that powerful for near-solar and closer distances is if you looking for medium/small (1km diam. objs easily fit into the small category) objects that possess a very low albedo (reflectivity). An asteroid with the right composition, for instance, can reflect so little sunlight that it would be invisible to nearly all means of passive detection except when you have the power of massive magnification of the Subaru telescope type. Such an asteroid would easily be able to approach earth undetected until much too late. If I remember correctly, a fairly large low-albedo asteroid passed near the earth just a few years ago, and remained undetected until it was inside the moon's orbital path.

The Japanese name on the telescope is for the star cluster we call the Pleiades, or the seven sisters.

The funding for Subaru came mostly from the government of Japan through a number of universities, much like how telescopes such as the Gemini telescopes are built. In fact it is run by the National Astronomical Observatory of Japan, the counterpart to the US's National Optical Astronomy Observatories. As the Japanese built it and paid for it, they can call it whatever they want. The only thing they have to do is give 15% of the time to observers at the University of Hawai'i.

Subaru's site is here and it has pictures, though the headquarters is on the big island (aka Hawai'i) and the net connection is slow.