Hubble Trouble: Hubble Space Telescope Misconceptions - Beam Me Up - Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing “Hoax” - Philip Plait

Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing “Hoax” - Philip Plait (2002)

Part V. Beam Me Up

We've traveled a long way in this book, from rooms in which we live to the ends of the universe and finally back again, to plunge into the cobwebbed depths of the human mind. Where, of course, there is still more bad astronomy. Don't think that the next chapters are in this last section because the topics didn't fit anywhere else in the book! Oh no, these chapters are special, so special that I decided that they didn't belong earlier in the book. (That, and they didn't really fit in with anything either.)

In this final section we'll see the best and the worst of ourselves as reflected in our works. We'll start with the Hubble Space Telescope, certainly the most abused $6 billion observatory ever built. There are so many misconceptions about Hubble that a whole book could be written about them. I hope you'll settle for just a single chapter.

Hubble may have cost a lot, but you don't need the gross national product of a country to buy the stars. Some companies will sell stars to you for a substantially reduced, though not inconsiderable price. But this depends on what you mean by "sell." It's not really stars these companies sell so much as a bill of goods. They promise the sky, but all they deliver is a piece of paper of dubious astronomical value. And there are darker implications of this transaction, too.

Our final exploration of bad astronomy takes us back to the silver screen. Epic myths may be Hollywood's biggest staple, but Tinseltown's grasp of science has never been the best. The box office may be the biggest purveyor of bad astronomy that exists. Spaceships don't roar through the skies, asteroids aren't that big of a danger, and aliens aren't likely to take a pit stop at Earth long enough to eat us. At least I hope they don't.

Of course, if they do, my job gets a lot easier. Bad astronomy would be the least of our worries.

Chapter 22. Hubble Trouble: Hubble Space Telescope Misconceptions

n 1946 astronomer Lyman Spitzer had a fairly silly idea: take a big telescope and put it in space. Looking back on his idea more than half a century later, it doesn't seem so crazy. After all, various nations have spent billions of dollars on telescopes in space, so someone must be taking the idea seriously. But in 1946 World War II was barely a year in the history books and the first launch of a satellite into orbit was still more than 10 years away.

Spitzer was a visionary. He knew that a telescope in space would have huge advantages over one on the ground, even before the first suborbital rocket flight gave others the idea that it was even possible. Sitting at the bottom of our soupy atmosphere yields a host of troubles for ground-based telescopes. The atmosphere is murky, dimming faint objects. It's turbulent, shaking the images of stars and galaxies until they all look like one blurry disk. Perhaps worst of all, our air is greedy and devours certain types of light. Some ultraviolet light from celestial objects can penetrate our atmosphere (the ultraviolet from the Sun is what gives us tans, or worse), but most of it gets absorbed on the way in. The same goes for infrared light, gamma rays, and x-rays. Superman may have x-ray vision, but even he couldn't see a bursting neutron star emit x-rays unless he flew up beyond the atmosphere, where there is no air to stop those energetic little photons.

I doubt Spitzer was thinking of Superman when he first proposed a space telescope, but the idea's the same. If you can loft a telescope up, up, and away, out of the atmosphere, all those atmospheric problems disappear. The ultraviolet and other flavors of light that cannot penetrate our atmosphere are easily seen when you're above it. If the air is below instead of above you it won't make stars twinkle, and the faint objects will appear brighter without the air glowing all around them, too.

Spitzer's vision became reality many times over. Dozens of telescopes have been launched into the Earth's orbit and beyond, but by far the most famous is the Hubble Space Telescope (colloquially called HST or just Hubble by astronomers). At an estimated total cost of $6 billion, Hubble has made headlines over and over again. Its images have made millions gasp in awe, and the astronomers who use HST have learned more from it than perhaps any other telescope in history, except, just maybe, Galileo's.

If you ask a random person in the street to name a telescope, Hubble is almost certainly the only one he or she will know. However, sometimes the price of fame is misconception in the public eye. Ask anything more specific, and that person will probably falter. Not many people know how big it is, where it is in space, or even why it's in orbit. Some think it's the biggest telescope in the world (or, more technically, above the world), some think it actually travels to the objects it observes, and others think it is hiding secrets from the public.

At this point in the book you've figured out on your own that none of these statements is true. Let's see why.


Even the most basic aspects of the Hubble telescope are misunderstood. For example, CNN's web site, when describing one particular Hubble observation, had a headline that read, "Stars Burst into Life before Hubble's Lens." Actually, Hubble doesn't have a lens. Like most big telescopes, Hubble has a mirror that gathers and focuses light. No less a luminary than Isaac Newton first figured out that a mirror can be used instead of a lens, and the most basic design for a mirrored telescope is still called a Newtonian. Four hundred years later, it still causes confusion.

Lenses are good for smaller telescopes but become unwieldy when they are bigger than about a half-meter (20 inches) across. They have to be supported from the edges, lest you block their view. Large lenses are extremely heavy, which makes them difficult to use. They also need to be placed at the aperture of the telescope, at one end of a long tube. That placement makes the telescope unwieldy and very temperamental to balance.

Since only the front side of a mirror is needed, it can be supported all along its backside, making mirrors easier to use. A mirror reflects light, but a lens has to have light pass through it, which can dim that light. Even better, when you're making a mirror, you only need to grind and polish one side and not two. That's a pretty good savings over a lens.

The Hubble Space Telescope floats freely over the Earth, prepared to take another observation of an astronomical object. Despite its clear views of the universe, the telescope is never more than a few hundred kilometers above the surface of Earth. (Image courtesy NASA and the Space Telescope Science Institute.)

Incidentally, the CNN web site made the same mistake less than a year later. I don't blame them, though. The Space Telescope Science Institute, which is charged with running the scientific aspects of Hubble, sponsored a PBS program about the telescope. In one episode, I heard an announcer introduce a segment as, "Through Hubble's Lens." If even PBS can get it wrong, what chance does everyone else have?


Many people are surprised at the large size of the Hubble satellite. It's roughly as big as a school bus. However, they are usually further surprised when told that the telescope is rather small as such things go. The primary mirror is 2.4 meters (8 feet) across. That may sound big compared to you or me, but there are many telescopes in the world more than four times that size. Even when Hubble was built it was not the biggest telescope. The legendary Hale Telescope at Pasadena's Palomar Observatory has a 5-meter (nearly 17-foot) mirror, and that one was built in 1936.

Not that Hubble is all that tiny. A full-scale mockup of it stands in a building at NASA's Goddard Space Flight Center in Greenbelt, Maryland. It's about five stories high and looms impressively over people as they walk by. Covered in shiny foil to reflect the Sun's light and keep the observatory cool, it looks like the world's largest TV dinner.

The reason Hubble isn't as big as some ground-based observatories is because it's hard to get something big into space. Hubble was designed to fit inside the Space Shuttle, and that put an upper limit on its size. The Next Generation Space Telescope, designed to observe infrared light and planned for launch in 2009, will be at least six meters (19 feet) across. One design calls for the mirror to be folded, and when it's out in space the mirror will unfold like a flower. Hubble's mirror, on the other hand, is basically one giant piece of glass, making it very heavy. If the mirror were any bigger, the spacecraft itself would have to be substantially larger to support it, making it impossible for the Space Shuttle to lift it.


A related misconception is that a telescope's most important function is to magnify an object, or make it look "closer." That's only partly true. It helps to make a small object look bigger, of course, but the real reason we make telescopes bigger is to collect more light. A telescope is like a rain bucket for light. If you are thirsty and want to collect rainwater, it's best to use a wide bucket. The wider the bucket you use, the more rain you collect. It's the same for telescopes: the bigger the mirror, the more light you collect from an object. The more light you gather, the fainter an object you can see. The unaided eye can pick out perhaps 10,000 stars without help, but with the use of even a modest telescope you can see millions. With a truly big telescope billions of stars become detectable.

The biggest telescopes on Earth have mirrors about 10 meters (33 feet) across, about the width of a small house. There are currently plans to build much larger telescopes. One design calls for a mirror 100 meters (109 yards) across! It's called the OWL, for Overwhelmingly Large Telescope. It'll cost a lot, but probably still less than Hubble did. A lot of that cost will probably go into simply finding a place to put it.

So Hubble may be small, but remember, it's above the atmosphere. The air glows, which washes out faint objects when viewed from the ground (see chapter 11, "Well, Well: The Difficulty of Daylight Star Sighting"). Hubble has darker skies and can see much fainter objects. The atmosphere also moves, so stars seen from the ground wiggle and dance (see chapter 9, "Twinkle, Twinkle, Little Star"). This spreads out the light from stars, making faint ones even more difficult to detect, especially if they are near brighter stars, which overwhelm them. With Hubble above the atmosphere, it avoids this effect and can more easily spot fainter stars. Between the much darker sky and ability to see faint objects, it holds the record for detecting the faintest objects ever seen: in a patch of sky called the Southern Deep Field, one of Hubble's cameras spotted objects ten billion times fainter than you can see with your unaided eye. That's a pretty good reason to loft a telescope a few hundred kilometers off the ground.


Still, it's not easy getting something that size into space. For a long time, Hubble was the largest single package delivered to orbit from the Space Shuttle. The Shuttle can only get a few hundred kilometers above the Earth's surface, and schlepping the 12-ton Hubble up made it even harder to get there. Using the Shuttle's robot arm, in April 1990 astronaut Steve Hawley gently released Hubble into the Earth's orbit, where it still resides, about 600 kilometers (375 miles) above the Earth's surface. It's another common misconception that Hubble is like the starship Enterprise, boldly going across the universe to snap photos of objects no one has snapped before. In reality, the distance from Hubble to the surface of the Earth is about the same as that between Washington, D.C., and New York City. Hubble is only marginally closer to the objects it observes than you are! Sometimes it's actually farther from them; it may be observing an object when it's on the far side of its orbit, adding a few hundred kilometers to the distance the light travels from the object to Hubble's mirror.

FILM AT 1 1:00

Which brings us to yet another common misthought about Hubble. Despite what many newspapers and television programs may say, Hubble has never taken a single photograph of an object. Hubble isn't a giant camera loaded with ISO 1,000,000 film. Hubble uses electronic detectors to take images of objects. These detectors are called charge-coupled devices, or CCDs. You've probably seen or used one of these yourself: handheld video cameras have been using CCDs for years, and digital cameras use them as well. They are much better than film for astronomy because they are far more sensitive to light, making it easier to detect faint objects. They are stable, which means that an image taken with one can be compared to another image taken years later. That comes in handy when astronomers want to look for changes in an object's shape or position over time. CCDs store data electronically, which means the data can be converted to radio signals and beamed back to Earth for processing. That's their single biggest advantage over film for space telescopes. Who wants to go all the way into orbit just to change a roll of film?


When Hubble points at an object, it's pretty likely to show us something we cannot see from the ground. That makes the data highly desirable, and of course that means a lot of competition to get time on the telescope. There aren't all that many astronomers around, but time on Hubble is an even rarer commodity. Once a year or so an announcement is made asking for proposals to use Hubble. Typically, NASA gets six times as many proposals as Hubble can physically observe during the upcoming year. Six-to-one odds are bit longer than most people like, but there is only so much observing time in a year. This creates a funny situation; a public telescope must, for a short time, have its data kept secret.

This time is called the proprietary period, and it is designed to give the astronomer a chance to look at the data. It may sound odd to keep Hubble data secret. After all, everyone's tax dollars paid for it, so shouldn't everyone have the right to see the data right away?

This may sound like a fair question, but really it's flawed reasoning. Your tax dollars pay for the IRS; then why not get access to your neighbors' tax returns? Ask the military for the blueprints for their latest secret fighter jet and see how far that gets you.

Now, to be fair, these really are secrets and there are good arguments for them to be. Hubble data are not really secret. But there is still good reason to let an astronomer have them for a year before they are released.

To see why, imagine for a moment you are an astronomer (if you are an astronomer, imagine for a moment you aren't so that you can then again imagine that you are). You have some nifty idea for an observation, and you decide you want to use Hubble for it. What do you do?

First, you'd better be sure you really need Hubble. Remember, for every astronomer trying to get time on Hubble, there are five others who are also vying for it, which means that right at the start you only have a one-in-six chance of getting your proposal accepted. That, in turn, means that the committee of astronomers that chooses who gets to use Hubble can be very picky. If your project can be done from the ground, you get rejected. If your project takes up too much time with only a marginal return in science learned, you get rejected. If you ask to do something that's already been done, you get rejected. If you ask to do something someone else is asking to do, and the other proposal is better, you get rejected.

Get the picture? It also takes days or weeks to prepare a proposal, time that you could spend working on other projects or trying to get other grants. You might use up a lot of precious time preparing your proposal only to have it roundly rejected.

But suppose you are lucky and your idea is accepted. Congratulations! Now you move to the next step. You have to painstakingly detail every single thing you want Hubble to do, including the initial pointing to your target, every exposure, every filter, every little bump and wiggle needed to get the observations you want. This detailing may also take several days or weeks, using complicated software guaranteed to give you a headache.

But finally you finish and submit the final proposal. Congratulations again!

Now you wait.

It may take up to a year or so to make those observations after the scheduling goes through. When you do, you are faced with many gigabytes of data, and you need a lot of software and experience to analyze them. It may take months or even years to figure everything out. With luck and perseverance, you may actually get a paper in the astronomical journals out of all this.

Now, think for a moment about all that work. All that analysis before and after the observations costs time and money, neither of which an astronomer has in copious amounts. For someone on a research grant time is money, and grants are very difficult to come by. Applying for HST time is a big gamble. You hope to get accepted, and then you hope the data are good enough to further your research, so you can get even more grants. I don't mean to put so much emphasis on money as a means unto itself, but without it, it's pretty hard to do research. In a sense, your future career as a scientist depends on your ability to get good data; you're staking your scientific reputation on your research. That Hubble data, once you've published it in an astronomical journal, is your lifeline.

Now imagine that the instant you get your data, some other astronomer has access to it, too. This other astronomer isn't as scrupulous and nice as you are. He or she also has experience with Hubble, knows just how to analyze your data, and might publish before you do! All that work, all that effort and time, and you get scooped with your own data.

That's why the data are held as proprietary for a year. That year gives the astronomer time to figure out what to do with the data and how best to analyze them. It's only fair to you, who devoted so much of your life to getting the data, to let you have a chance to look at them before anyone else.

So there's no real secret involved. At the end of the proprietary period, ready or not, the data become public. Far from being anything shady on the part of NASA, keeping the data secret for a year is actually the best way astronomers have come up with to further the cause of science in a fair manner. It can be an agonizing wait when you know some good data won't be available for a year, but it's worth it.


Hubble is more than just a telescope with a camera stuck onto it. It's a telescope with several cameras stuck onto it. Each instrument has a specific task. Some take ultraviolet images, others take infrared. Some take spectra by breaking the light from an object into individual colors. Each camera is a delicate, expensive piece of machinery.

Some of these instruments are very sensitive to light. They can actually be damaged if too much light hits them. Anyone who has ever had a roommate turn on a light in the middle of the night can sympathize with that.

This sensitivity has caused yet another myth about Hubble, that it cannot take images of the Moon. As the myth goes, the Moon is far too bright to be observed by Hubble without damaging these delicate instruments.

This turns out not to be the case.

It is true that the operators of Hubble need to be careful with subjecting the instruments to "an overlight condition." For example, there is a very strict "solar avoidance zone," a large area of sky around the Sun where Hubble is forbidden to look. The Sun is too bright, and if Hubble points too closely to it, the Sun would do all sorts of damage. That law is very stringently applied and has only been bent once, to observe the planet Venus.

However, this doesn't really apply to the Moon, which is far less bright than the Sun. While it's true that some of Hubble's cameras are very sensitive to light, they can simply be shut off during a lunar observation, allowing other, less sensitive cameras to be used. Still, many people have this mindset that you cannot look at bright objects, including the Moon. It's funny, because Hubble routinely observes the Earth and, from Hubble's vantage, the Earth is far brighter than the Moon.

The reason Hubble observes the Earth is nothing nefarious. Sometimes the great observatory is turned toward the Earth to take long exposures that help calibrate the cameras onboard. This allows astronomers to understand how the cameras behave. Hubble cannot easily track fast-moving objects, and the ground moves underneath Hubble at a clip of eight kilometers (five miles) per second. It makes a lousy spy satellite. The images are all streaked from the movement of the objects. I've seen some of these images, and you can clearly spot houses and trees that look like long, gray streaks. You don't have to bother shutting your window to protect your privacy. All Hubble sees of you is a long, blurry worm.

So, if Hubble can take images of the Earth, it certainly can take images of the Moon. The belief that the Moon is too bright is unfounded.

That said, why don't we see routine Hubble observations of the Moon?

For one thing, we already have really good images of the Moon from the Apollo missions and the Clementine lunar orbiter, better than Hubble can take. But there's more.

Here's where I sheepishly must admit to propagating my own little piece of bad astronomy. I'm commonly asked this question. I also used to say that Hubble can't take images of the Moon. It's not that the Moon is too bright, it's that it moves too fast. Hubble must be maneuverable enough to track nearby planets as they orbit the Sun, but the Moon moves across the sky much faster than even the fastest planet. There's no way, I would say, that it could track the Moon.

I was partially wrong in saying that. True, Hubble cannot track the Moon. But it doesn't have to track it. The Moon is bright. When you take an image of a bright object, you can take a shorter exposure. In fact, Hubble could take an image of the Moon with such a short exposure time that it would look as if the Moon were not moving at all. It's just like taking a picture out the window of a moving car. If you take a long exposure the trees will look blurred due to your motion. But if you snap a fast one the trees will look sharp and motionless. They don't have time to blur.

In 1999 just such an image of the Moon was taken by Hubble. The astronomers were clever. They put Hubble into "ambush mode," pointing it to a place where they knew the Moon would be and waiting for it to move into view. When it did, they took the image using a fast exposure. The results were pretty neat. They got nice pictures of the Moon, although not really any better than we had from orbiters. The principal goal of the observations was to get spectra of the lunar surface to help astronomers understand the properties of all the planets, and the images were an added bonus. So Hubble can indeed shoot the Moon, and did in the waning years of the twentieth century.

Ironically, while many people think that the Moon is too bright to observe with Hubble, it's the very brightness that allows Hubble to observe it! It's bright enough to let us take short snapshots of it without blurring.


Unfortunately, the Moon issue won't die. Some people really want to see conspiracies and cover-ups everywhere they look, even when there are none to be had. One such person is Richard Hoagland, who maintains a long list of supposed NASA shenanigans, most of which involve space aliens. It would be fair to call Hoagland a kook. He leads the cause for the alien nature of the Face on Mars as well as a host of other fringe claims. On his web site (htty he has an article about the Moon and Hubble with the headline: "NASA Caught in Yet Another Lie."

Hoagland quotes a Hubble astronomer and expert on Hubble imaging. As Hoagland relays on his web page, a UFO researcher asked the astronomer the following question: "Has Hubble taken any photos of the moon?" He responded: "No, the moon is too bright (even the dark side) to observe with HST."

I know this astronomer and called him about this. I swear I could hear his embarrassed smile on the phone. He apologized and said that the quote was sadly accurate, and he could kick himself for making the mistake. He simply wasn't thinking clearly and said the wrong thing. Unfortunately, with the web cranks can use his misstatement for their own ends. Hoagland claims that this is part of the NASA/alien cover-up of bases on the Moon. His headline about "NASA lies" is a bit disingenuous. A lie implies intent to deceive, while in reality an honest error was made. Also, the astronomer is not a NASA employee. Accuracy is perhaps not Hoagland's forte.

Hoagland's thrust is that this is just another NASA lie to cover up the fact that Hubble can indeed observe the Moon. According to his twisted logic, NASA spent years saying the Moon was off limits to Hubble to keep astronomers from finding the aliens. If that's true, why did NASA allow the team of astronomers to observe the Moon at all? In a rather typical example of conspiracytheory logic, Hoagland ignores obvious facts that go against his conclusions.

It would be silly of NASA to maintain a conspiracy by claiming that the Moon is too bright to observe when, in fact, it was public record from the start that it routinely observes the much brighter Earth. Hoagland assumes, from one astronomer's single misstatement, that everyone in the astronomical community is part of a massive conspiracy and would blindly stick to an argument that is clearly contradictory to facts. Having worked with some of the astronomers and engineers who designed and use Hubble, I can assure you that these hardworking, intelligent, and clever people have no interest in covering anything up.

It gets even better. Not only was NASA not covering anything up, it actually initiated a fairly large amount of hoopla over the Hubble Moon images. Like most cranks, Hoagland is capable of weaving entire empires from fantasy, and would rather accuse people of lying than actually try to think logically for a moment.

In the end, the cranks and conspiracy theorists will believe whatever tale they tell themselves, as they always do and always will.


I'll leave Hubble with one more story.

Probably my favorite media misadventure with Hubble involves that bastion of near-reality, the Weekly World News. Everyone knows their articles are jokes ... or do they? It sells pretty well in grocery stores, and I always wonder how many people take it seriously. Headlines often scream, "Angels are Real-and Visiting Your Bathroom!" or "Boy Born Half-Bat Terrorizes Neighborhood!"

On July 19, 1994, the News had a story headlined "First Photos from Hell!" with the subtitle, "Listening device picks up screams coming from Black Hole!" (They use a lot of exclamation points.) According to the article, Hubble was observing a black hole when it detected a clear signal of people screaming. Obviously, these were the tortured souls of the damned in hell.

Ignoring for the moment (or forever) the silliness of Hubble picking up sounds at all, especially from hell, the best part of the article for me was the accompanying picture of a Hubble image of Supernova 1987a, a star that exploded in 1987. I studied this object for four years for my Ph.D., analyzing Hubble images and spectra. I sometimes worked until late at night trying to decipher what I saw, pounding my head on my computer screen in hopes of shaking loose some rusty cog in my brain. I never heard any tortured screams except my own.

So the last thing I need is for the Weekly World News to tell me that Hubble images of Supernova 1987a were hell. I wrote a whole thesis about it!