Category Archives: Hubble Space Telecope

How Time Flies

Hubble Space Telescope’s 22nd Anniversary and Me

This past week marked the 22nd anniversary of the launch of the Hubble Space Telescope.  It really is hard to believe all that time has passed, but the solid record of science achievements from this famous orbiting telescope is proof that even if you start out with a problematic telescope, you can still do good science. Of course, making Hubble DO that good science took squads of astronauts, ground-based technicians and scientists years of problem-solving to do.  But, they did it.

I was not quite in graduate school when Hubble went up on April 24, 1990. I’d been part of a science team at the University of Colorado for just over a year and a half, led by Dr. John C. Brandt, who was (at that time, among his many responsibilities) the co-Principal Investigator for the Goddard High-Resolution Spectrograph instrument onboard HST.  I was working on a project analyzing Comet Halley images; specifically, I was doing astrometry on images of the comet’s tail so that we could analyze how the tail was being affected by the solar wind as the comet rounded the Sun during its last close approach in 1985 and 1986.

Not long after launch, Jack came back from Goddard Space Flight Center and warned us that there could be some problems with the telescope.  I think that only a few people knew how bad the problems were, mostly because they were still analyzing the images and calibrating the telescope. But, in June 1990, the full news broke and people were devastated by the idea that HST was flawed. I know we at the university were.

But, even as early as August of that year, we were seeing images that didn’t look awful, and I knew from talking with Jack that there was good science to be had — even if it took a bit longer to analyze the images. Our instrument, however, was pretty badly affected, as was the Faint Object Spectrograph.  I started to make notes about the problems with the telescope, and paying attention to the images it was producing. I think I had some idea that I’d write a book about the project someday and I knew it would be good practice to keep notes from the early days. In the meantime, I plugged away on the Comet Halley project, which eventually got published in 1992 as the International Halley Watch Atlas of Large-Scale Phenomena (Brandt, Niedner, and Rahe, with mucho work done by me in a small-credit role).

This Hubble image of the Egg Nebula shows one of the best views to date of this brief but dramatic phase in a star’s life. This is the site of a star in its death throes. At the center of this image, and hidden in a thick cloud of dust, is the nebula’s central star. While we can’t see the star directly, four searchlight beams of light coming from it shine out through the nebula. It is thought that ring-shaped holes in the thick cocoon of dust, carved by jets coming from the star, let the beams of light emerge through the otherwise opaque cloud. The precise mechanism by which stellar jets produce these holes is not known for certain, but one possible explanation is that a binary star system, rather than a single star, exists at the center of the nebula. The onion-like layered structure of the more diffuse cloud surrounding the central cocoon is caused by periodic bursts of material being ejected from the dying star. The bursts typically occur every few hundred years.Courtesy NASA/STScI.

Well, after that one thing led to another—I studied MORE comets as part of the Ulysses Comet Watch, and  I entered graduate school and joined Jack’s GHRS team (albeit as a very junior member).  The science flowing from HST was getting better and better, and the first servicing mission proved that the telescope could be brought “up to spec”.  So, I decided to shop around the book idea, and took Jack on as a co-author.  After a false start or two, we ended up signing a contract with Cambridge University Press, and in 1995, we published Hubble Vision, which was updated a few years later. I also did a planetarium show by the same name, which has been a mainstay of my company’s repertoire ever since (read more about that show here).

I feel like I kind of grew up with Hubble, or maybe we grew up together. I feel privileged to have worked on an instrument team for HST, and to have written about it as extensively has I have.  The telescope has for me–and I hope for all people who follow astronomy exploration–expanded the horizons of cosmic understanding. And that’s a great tribute to its 22 years (and counting) legacy!

If you haven’t taken time to browse the images at Hubblesite.org, take some time to do so. The very act of exploring those pages is a voyage of exploration of the universe.

Check it out!

 

 

Hubble’s Star

How A Star Expanded Our Understanding of the Universe

Humans have stared at the stars throughout history and that makes stargazing one of our oldest sciences. Probably THE oldest, along with the accidental chemical experiments that led our earliest ancestors to create things like soap and tea and other necessities.  And, of course, humans have engaged in biological experiments throughout history, and eventually took up engineering and geology and all the other sciences we know of today.

Still, it’s astronomy that piques our interest. I often think about what the first people who stared at the stars thought of what they were seeing.

I’ll give our species the benefit of the doubt and assume that there was intent curiosity about it all, a sense of wondering what they are and if they could be touched or visited. It probably didn’t take long for humans to start woolgathering all kinds of stories about them, and eventually their awe at these sparkly things turned into some kind of reverence.  Heck, a sunrise inspires me greatly, and I’m sure it did for those early folks, as well.

I also like to think of those early astronomers getting together and discussing what they saw, debating what the motions meant, how they were made, and what relationship those things had to Earth. The history of astronomy is written by those people who did MORE than just look at the sky.  They made careful notes about what they saw, and those observations led to speculation and eventually the application of scientific principles to explain the structure and motions of things in the sky. And, in due time, they shared their knowledge and our societies are richer for it today.

Speaking of meetings, the summer meeting of the American Astronomical Society is taking place this week in Boston. I can’t be at this one, but I’m hearing and seeing lots of fascinating news from the assembled astronomers.  They’re sharing what they’ve found — from planetary systems to peeks at the most distant stars and galaxies.

The star that changed our perceptions of distance in the universe. Courtesy STScI.

One story that caught my attention is focused on a star in a distant galaxy. It first caught the attention of an astronomer early in the 20th century. The star is a Cepheid variable star — that is, one that pulsates in brightness in a regular and predictable rhythm. It caught the attention of astronomer Edwin Hubble (for whom the Hubble Space Telescope is named).

He knew that the light pulsations could be used to help measure distances in the universe. So, he did what any self-respecting astronomer would do, he measured the pulsations precisely, kept good records, and when he had enough good data, he calculated the distance to the star.

That calculation (which any student in astronomy can do these days), showed that the galaxy in which the star existed — the Andromeda Galaxy — was not part of the Milky Way Galaxy that we live in.  It wasn’t even close. Instead, it and Andromeda were at least 2 million light-years away.

This finding probably excited Hubble very much; enough that he sent a letter to his colleague, Harlow Shapley, describing his finding. Shapley recognized the significance of Hubble’s finding — that is, that the universe was larger than we thought — and commented to another colleague, “Here’s the letter that destroyed my universe.”

It was an important step in understanding how large the universe is, one that astronomers still rely on today to figure out distances to some of the farthest objects in the cosmos. In commemoration of Hubble’s  landmark observation, astronomers with the Space Telescope Science Institute’s Hubble Heritage Project partnered with the American Association of Variable Star Observers (AAVSO) to study the star.  AAVSO is a group of dedicated observers (both amateur and professional) who focus on the glimmerings of variable stars. Their work has contributed greatly to our understanding of these stars — and hence, to distances in the cosmos.

AAVSO observers followed brightness pulsations of the star in Andromeda — called V1 — for six months. Their observations were combined into what astronomers call a data “plot” (that is, put into an X/Y axis, just like you might remember doing in geometry or calculus). That plot is called a “light curve” and it shows  the rhythmic rise and fall of the star’s light. (If you want to see what a light curve looks like, click on the AAVSO link above; they have some on their front page, and explain them in more detail).

Based on this data, the Hubble Heritage team scheduled Hubble telescope time to capture Wide Field Camera 3 images of the star at its dimmest and brightest light levels.

As a reminder of how important these observations are, the combined data and images were presented at the AAS meeting on Monday (you can read the whole story here). Astronomer Max Mutchler commented, “This observation is a reminder that Cepheid variables are still relevant today. Astronomers are using them to measure distances to galaxies much farther away than Andromeda. They are the first rung on what astronomers call the cosmic distance ladder.”

That ladder stretches out to the earliest stars and galaxies, more than 13 billion light-years away. It’s an awesome achievement for a species that only began looking at the stars with the intent to understand them perhaps a few hundred thousand years ago.