Speaking of Hubble...

Archive: September 2012

Pluto in Hiding

September 28, 2012 by Tracy Vogel
No, Pluto is not ready for its close up, thank you.

No, Pluto is not ready for its close up, thank you.

Oh, Pluto. Beloved Pluto. The endearing, scrappy runt of our solar system litter, demoted but never defeated. We heart you, you crazy little Kuiper Belt Object, with your icy surface and newfound moons and multiple references to Disney films, what with Mickey Mouse’s dog and now the dwarf planet thing. Hi-ho, Pluto. Hi-ho.

So today we’re going to discuss a question I encounter on occasion. “Hey,” it goes, roughly, “How come we can see all this detail in a galaxy 46 million light-years away, but your pictures of Pluto look like someone airbrushed a basketball and photographed it through a Vaseline lens at the bottom of a swimming pool? Pluto’s right next door, while this galaxy is clearly at least as far away as the mall.”

Well, aggrieved person suspiciously intent on invading Pluto’s privacy, first understand that these images are actually really neat. This is the most detailed view ever of the entire surface of Pluto. You’re watching the seasons occur on an object so far away that it takes light from the Sun over five hours to reach it. We’re honestly a little hurt. Do you know how much effort that took? How much manpower? Do you think it’s easy to smear that much Vaseline on a lens in space? It is not.

You are right, though – Hubble’s pictures of Pluto do lack the detail people have come to expect from the telescope. Basically, it’s an issue of size. To understand it, you have to understand something called “angular resolution,” which – where are you going? Get back here right now, Pluto e-mailer, and listen while I explain angular resolution to you in excruciating detail! That’s right. We’re all in this together, now.

So, angular resolution. Draw two lines on a piece of paper and have a friend hold that paper up and start to walk backwards. Eventually, you’ll only see one line. That’s angular resolution in action – the ability of a picture-taking device – in this case, your eye – to distinguish between details. If you use a much bigger piece of paper, and draw the lines farther apart, your friend will get farther before you stop seeing two distinct lines. Both size and distance matter when it comes to angular resolution.

Angular resolution is a set thing – for eyes, for cameras, and for telescopes. The human eye has an angular resolution of about one arcminute. Hubble has an angular resolution of .05 arcseconds. That’s good enough to stand on the East Coast of the US and distinguish between lines spaced about three feet apart on a piece of paper that your friend is holding up on the West Coast. Also, that’s one really good friend you have there. Does he owe you money, or a kidney, or something?

Now, galaxies are huge. When Hubble looks at a galaxy, it’s observing a collection of immense objects at incredible distances from one another. (Even then, you’re usually seeing clusters of stars, not individual stars in these galaxies – Andromeda is about the farthest galaxy in which Hubble can actually resolve individual stars.) The beautiful spiral galaxy NGC 2841 is a bit over two arcminutes in size.

Little Pluto? He’s about .06 to one arcseconds wide in the sky.

The angular resolution of a telescope, just like the angular resolution of your eyes, is fixed. Hubble is resolving both the galaxy and Pluto the exact same way. But one has a lot more space and size to work with than the other.

These images of Pluto are painstakingly compiled from lots of Hubble data with the help of years of computer processing. As one astronomer put it, they’re really maps, not pictures.

But it’s not over, saddened, would-be Pluto observer. You’ve got 2015 to look forward to, when the New Horizons spacecraft will complete its decade-long, 3-billion-mile journey to the smallest sort-of member of the solar system and give us a spectacular, up-close view of this Kuiper Belt object … for six months. And then it’s back to fuzzy basketballs as seen through multiple layers of gauze on a foggy day with debilitating nearsightedness.

So time will be, as they say, of the essence. And that’s when those seemingly dull Hubble maps will prove their worth, helping astronomers decide the most interesting areas on Pluto for the probe to target while it can.

Can We Do Galactic Archeology?

September 21, 2012 by Ray Villard
The Whirlpool Galaxy

The Whirlpool Galaxy

When I was under the velvet-black skies of western Texas a few months ago, I had a magnificent view of the star-studded bulge of our galaxy in the direction of the summer constellation Sagittarius.

How many advanced alien civilizations might be in this crowded hub of the Milky Way, I pondered? The problem is that we are embedded in a thick forest of stars, and identifying the location of an extraterrestrial civilization – one that’s attempting to contact us – is the proverbial needle-in-a-haystack search, as the SETI scientists always say.

So instead of looking for signals, perhaps the way to find evidence of E.T. is to scrutinize the physical evidence in a neighboring “forest,” or rather nearby galaxy.

Because even the nearest galaxies are millions of light-years away, any idea of communicating with these aliens is unfeasible. Our observations would be made for purely identifying archeological evidence of the actions of a civilization.

For this to work you would have to look at the tallest trees in that forest, i.e. engineering activities on such a large scale they give an anomalous appearance to the galaxy that cannot be explained by known astronomical processes. The features would instead be the handiwork of super-duper civilizations that are leaving their ecological imprint on the galaxy at a mega-scale.

In 1964, the Soviet astronomer Nikolai Kardeschev hypothesized such extraterrestrial civilizations as Type II. They would surpass our energy production capabilities by a factor of approximately 10 billion. How? By capturing the total energy output of their parent star.

In the early 1960s, physicist Freeman Dyson proposed that a shell could be built around a star to trap much of its energy. The shell would be fabricated from dismantling a planet about the mass of Jupiter.

This so-called “Dyson sphere” is legendary, and there have even been searches for the signature of such artifacts in astronomical infrared databases. The problem is that a star enshrouded in dust would look pretty much like a Dyson sphere. In a survey of 250,000 infrared sky sources cataloged in the 1970s, 17 “quasi-plausible” Dyson sphere signatures came up, according to Richard Carrigan of Fermilab.

It’s imaginable that a super-civilization would begin a wave of colonization that spread out to neighboring solar type stars from its home base. Each offshoot would “astro-form” the colonized planetary system by constructing a Dyson sphere around the host star.

Carrigan envisions seeing “Dyson bubble” in nearby galaxies. These would be clusters of Dyson spheres that enclosed a grouping of stars colonized by a Type II Kardeschev civilization.  The logic is that after you’ve built a backyard fence, you can start to conceptualize building the Great Wall of China and still hope to gain perspective on the process, Carrigan says.

These Dyson bubbles would be detected as anomalous dark voids in a galaxy’s disk. When these voids were observed in infrared light they would glow brightly with the heat radiation from the surfaces of Dyson spheres. This would show that they are not simply voids where solar-type stars are conspicuously missing.

The Hubble Space Telescope is conducting a multi-year survey across a swath of the neighboring Andromeda galaxy. The images are filled with so many resolved stars that they look like grains of sand on a beach. This could make an excellent citizen science project, to scour the Andromeda fields for anomalous-looking regions.

The magnificent face-on Whirlpool galaxy, M51, is an ideal place to go looking for Dyson bubbles. Hubble has photographed the entire galaxy down to a resolution of roughly 15 light-years across.  Present Hubble and Spitzer Space Telescope infrared photos of the Whirlpool reveal the typical galaxy’s intricate cobweb tracing in dusty filaments.

However, a rough qualitative estimate by Carrigan suggests that there are no unexplained bubbles or voids in M51. This analysis is complicated by the fact that the infrared light skeletal pattern of a spiral galaxy pattern itself is shaped by voids.

Gigantic elliptical galaxies, which are completely devoid of light-blocking dust, would look very odd indeed if dark voids were detected. However, the nearest ellipticals are 60 million light-years away and so would require a space telescope much larger than Hubble to yield enough resolution to detect anomalies.

An apparent lack of any evidence for large-scale artifacts in galaxies as old as ours begins to set an upper limit on just how technologically advanced alien civilizations can evolve.

Kardeschev hypothesized about Type III civilizations that would harness the entire energy of a galaxy. The observational evidence for astro-engineering an entire galaxy is lacking, and so it’s fair to say that Type III civilizations just don’t exist at all – or at least not yet.

The universe has had 12 billion years to evolve a Type II or Type III civilization. If there’s no obvious archeological evidence, than maybe intelligent beings don’t evolve all that far beyond our projected capabilities of perhaps mega-engineering on the scale of a single solar system.

Maybe extraterrestrials simply don’t have the motivation, know-how, or the budget.

Mirror, Mirror in the Sky

September 7, 2012 by Frank Summers
Jupiter could be the next test subject for analyzing light from a Venus transit.

Jupiter could be the next test subject for analyzing light from a Venus transit.

My blog post of May 25, 2012 was titled “Examining Venus in a Lunar Mirror.” In that piece, I described how Hubble would attempt to observe the transit of Venus on June 5, 2012.

The idea is that, since Hubble cannot directly observe the Sun, one could look at the Sun’s light reflected off of the Moon. A detailed analysis might be able to separate out the signature of light that passed through Venus’ atmosphere. The observation would be a proxy for studying the atmospheres of extrasolar planets that happen to transit their star from our point of view. Venus, with a known atmosphere, could serve as calibration for the unknown atmospheres of extrasolar planets.

Sad to say, the Hubble observations were a failure. Not every science experiment goes as planned. Well, actually, this observation went as planned, but the planning was incorrect. A miscalculation in positions meant that the observation did not capture what had been intended.

But science is an enterprise where learning from failure is not just possible, it is one of the main methods of advancing the field. For all the triumphs and breakthroughs that are celebrated, there are a thousand times more investigations that uncovered modest, incomplete, or dead-end results. That work invariably builds the foundation and shapes the blueprints for the eventual discovery.

In this case, the lesson is to think bigger: Don’t just take our Earth-bound perspective, consider things from a solar system perspective. The next transit of Venus as seen from Earth will be in December 2117, but the next Venus transit visible in our solar system will be on September 20, 2012 – seen from Jupiter.

A proposal has been put forward for Hubble to observe Jupiter, both before and during this transit, to perform a study of the Venusian atmosphere in reflected light similar to Hubble’s Venus transit Moon observations.

Perhaps more exciting, Earth itself will transit the Sun as seen from Jupiter on January 5, 2014. What could be a better test of looking for Earth-like planets elsewhere than to study our own planet in an analogous fashion? Mirror, mirror in the sky, Hubble watches Jupiter as Earth passes by.

Opportunity arises from understanding one’s mistakes. It is a great lesson in science and in all of life’s pursuits.