Speaking of Hubble...

Hubble's sharp vision uncovered white dwarf stars in the ancient globular cluster NGC 6397.

As you stargaze over the next few weeks, keep in mind that most of those tiny points of light scattered across the sky are burning infernos of gas. These stars are very much like the Sun. Some are bigger and more powerful, and some smaller. But they are not constant. Stars change over time, and evolve into different states. Understanding this process of “stellar evolution” is my primary passion in astronomy, and was the focus of a meeting we just held at the Space Telescope Science Institute, “The Mass Loss Return from Stars to Galaxies.”

Stars are sort of like humans … They are energetic when young, “cool” when old, and kind of boring in the middle years. The most important property of a star that defines how it will evolve over time is its mass. A low-mass star, like our Sun, will slowly burn its hydrogen into helium, and remain in a state of equilibrium for billions of years. This is great for us on Earth, since it provides us with a stable environment. But in about 4 billion years, the Sun will expand and begin to lose its outer layers. During this stage, called the red giant phase, the Sun will be so large that it will encompass the Earth’s orbit around it, crisping our planet!

Unlike our Sun, more massive stars – about 10 times the Sun’s mass – will suffer a very different fate. These stars burn through their gas very quickly, like sports cars, and then blow up as supernova explosions. In doing so, the star experiences a very energetic death and sprays 90% of its material into its surroundings. Why does this matter to us if our Sun will never meet this fate? Because this spewed-out material from exploding stars is very important in the cosmic cycle of star and planet formation. All the elements heavier than hydrogen and helium are produced in the cores of these massive exploding stars. That includes everything you see around you, from the computer you’re reading this on to the skin on your body. Yes, you are made of “star stuff.” Our Sun and its planets formed in a region of space that had already been polluted by previous supernovae, and so these heavy elements exist here.

So what about the death of our own star? During one of the breaks at the meeting, I spoke with a colleague of mine about the end fate of the Sun. When we look at the nearby galaxy, we see beautiful stars in the “planetary nebula” phase of their life cycle. This phase only lasts for a short amount of time, during which the outer layers shed by the star – the “mass loss” of the meeting’s title – are illuminated by the hot and exposed core of the dying star, the white dwarf. The resulting pictures of these objects are among the most beautiful sights in the universe. My colleague and I asked ourselves whether the Sun would end its life in one of these states, but we concluded that it would be unlikely.

The Sun has a couple things working against it. First, it doesn’t have as much mass as some of the other stars that become planetary nebulae, so the stellar ejecta will be less dense. Second, because it has less mass, it will evolve more slowly than larger stars. By the time the core of the dying Sun is ready to light up the material around it, that material will be more dispersed. Both of these effects lead to an unlikely case for a bright illumination of the gas.

Eventually, after the outer layers have been shed, the remnant star of the Sun – the stellar cinder – will cool and dim as time passes. This type of white dwarf star is the final resting state of 98% of all stars. These dead stars are littered all across our galaxy, and they have incredible properties. First, having no nuclear fuel, they are extremely faint and hard to detect. Powerful telescopes like Hubble have, however, revealed large populations of these stars in the nearby galaxy. Second, these stars are very dense. Although the progenitor lost half (or more) of its mass, the core is very small – about the size of the Earth. The density of the star is therefore about a million times higher than the density of ordinary matter on Earth. A tablespoon of material from a white dwarf would “weigh” as much as a school bus. Finally, the composition of that core is largely carbon, an end product of helium burning in the progenitor star. So, a white dwarf is essentially highly compressed carbon. In other words, our Sun will end its life as a giant natural diamond!

I’ve attended the American Astronomical Society (AAS) general winter meeting since I started graduate school in 2001. At these meetings, upwards of 3,000 astronomers gather to present and hear new science results, form collaborations, organize smaller meetings with existing collaborators, and generally interact with one another. (For more information on what happens at an AAS meeting, see my blog entry from February 2011.) This year I went to the meeting with a new tool, Twitter.

Scientific discoveries are announced at the AAS meeting at a ferocious rate. Many news organizations are on hand, and they quickly write stories and issue press releases that describe our new understandings of the universe. Still, with a half-dozen parallel science sessions going on at once in different conference rooms, I always feel that I’m missing a lot of the action at the meeting.

A few months ago, I signed up for a Twitter account under the name @JasonKalirai. I’ve been using the social media service a few times every week to send out interesting tweets on astronomy pictures (e.g., Astronomy Picture of the Day) as well as other tidbits of information related to the Hubble and James Webb Space Telescopes. Occasionally, I share something personal, but usually it’s focused on astronomy. I keep up with what is being said in the “Twitterverse” much more than I tweet, and have found that I can stay on top of interesting developments in the scientific world as they happen.

At this year’s AAS meeting in Austin, Texas, I was happy to see astronomers and bloggers consistently use the #AAS219 hash tag on Twitter when discussing science results and events at the meeting. By simply following the hash tag, I could guarantee that I wouldn’t miss any of the big news. For example, I was in the poster room when I saw Twitter light up with an announcement of the discovery of the most distant cluster of galaxies by Hubble, and also of Kepler’s new discovery of the smallest exoplanets.

I found myself using the #AAS219 hash tag frequently in my own tweets during the meeting. I used this to announce several Webb initiatives and events that my group organized in Austin. For example, we put together a short community survey where astronomers could tell us which user tools they would find most beneficial. We also tweeted about our new Webb science brochures, the Hubble imagery being shown on the 3D TV at our booth, and various events.

When the power cut out during Nobel Laureate John Mather’s presentation on the Webb Space Telescope, I was able to tweet the link to slides I’d put together for him to use in his talk, allowing the audience to follow the images as he went into “freestyle mode.”

All together, over 4,000 tweets were sent using the #AAS219 hash tag. I found Twitter to be an extremely useful tool to share astronomy highlights, and will continue using it in the near future. I hope more astronomers will also jump on board, and begin using Twitter to exchange results from all meetings, domestic or international. At the same time, Twitter provides us with a powerful “public outreach” arena to inform the general population on the fascinating research that we do.

Now, time to tweet this article out.

NASA's Great Observatories, four space-based missions designed to conduct astronomical studies over many wavelengths

As an astronomer, I have many tools at my disposal to study the universe and tackle tough questions. There are hundreds of ground and space-based telescopes that we point to the cosmos, powerful computers that analyze the images, and a wealth of knowledge on the internet and in libraries that both describe our current understanding and provide the mathematical framework to solve problems.

While the current suite of tools will continue to enable new research on a wide range of astronomical questions, history teaches us that major discoveries and breakthroughs come about when we apply new technologies to create unprecedented resources. For these reasons, I can hardly wait to see the first images from the James Webb Space Telescope.

Almost 100 years ago, astronomers built the first large, modern telescopes on the ground. Telescopes like the Hale and Hooker telescopes at Mt. Wilson Observatory, with their 60” and 100” mirrors to capture faint light, provided a new level of clarity in characterizing nearby stars in our galaxy, and led to the breakthrough discovery that our Sun is not located near the center of the Milky Way galaxy. These technologically advanced telescopes also enabled Edwin Hubble to prove that our galaxy itself was not alone in the universe, and that others like it were also wandering in space.

As astronomers produced larger and stronger telescopes, our ability to push beyond the Milky Way  increased greatly, and we began to understand the vast nature of our universe and the diversity of galaxies within it.

NASA enabled a new leap forward in our understanding of the universe by developing the first big telescopes in space, such as Hubble and Spitzer. This Great Observatories program represented a bold new vision to expand our astronomical discoveries.

Hubble, launched over 20 years ago, has revolutionized almost every field of astronomy and planetary science, reshaped our knowledge of the universe and our role within it, and brought enthusiasm about space science to the general public, students, and educators. I personally owe a big thanks to Hubble. When I started my postdoctoral researchship in Santa Cruz, CA, in 2004, I was awarded a “Hubble Fellowship.” This research grant allowed me extreme flexibility and resources to pursue the research that I wanted, and was a great springboard for launching me to my career path.

Nowadays, I use Hubble both for my own research and to educate the public about the amazing discoveries that it has brought forth. Just a few weeks ago, I was showing pictures from Hubble to 500 kids in Long Beach, CA. It is one of the reasons that I love astronomy so much.

In the next few years, all of the Great Observatories may reach their limits. Astronomy is a science that is limited by the quality of the observations, and those observations are limited by how much light our telescope’s mirrors can collect. Hubble and Spitzer have demonstrated that many of the most important questions that we face in astronomy today can be answered by designing a powerful new telescope that combines Hubble’s razor-sharp vision with Spitzer’s infrared sensitivity.

To enable this next leap forward in telescopes, NASA has teamed up with the European Space Agency (ESA) and the Canadian Space Agency (CSA) to build the successor to the Great Observatories, the James Webb Space Telescope (JWST). As both an astronomer and as the Deputy Project Scientist for this mission, I feel very fortunate to be a part of this important scientific and technological achievement.

JWST, or “Webb” as we call it, will significantly overlap with Hubble and Spitzer in the range of wavelengths it sees, (red optical, near infrared, and mid infrared), and, most importantly, be more than 100 times as powerful as these Great Observatories. JWST includes many different types of cameras, spectrographs, and coronographs, to enable a diverse range of scientific investigations for astronomers. It is exactly what we have been waiting for!

Astronomers like myself have been excited about JWST for over a decade, and the project has now completed several important milestones. All 18 of the primary mirror segments of JWST (which span 21 feet when put together) are completed. All of the science instruments on the telescope are also making excellent progress. The telescope will soon enter a phase of assembly and testing, where all of the various completed parts are put together and tested as a whole. This ensures that everything works correctly in space, since astronauts will not be able to “service” JWST as they did for Hubble.

Once JWST launches in 2018, astronomers will embark on several new scientific projects that have not been previously possible. In my opinion, some of primary science goals of JWST for astronomers are intimately tied to fundamental questions that humankind has asked itself for centuries.

I grew up in a small town called Quesnel in central British Columbia, Canada, about 8 hours north of Vancouver. We had a beautiful view of the night sky. When I would stare up at the cosmos, I would ask myself how the universe began, how it came to be littered with all of these stars and galaxies, and whether there is life elsewhere on another planet.

JWST will reveal the first stars and galaxies in the infant universe, will teach us how these galaxies evolved to form beautiful systems like the Milky Way, will uncover newborn stars and planets in our own galaxy, and will examine the atmospheres of planets outside our solar system for the signatures of water vapor. Where there is water, there may be life!

And yet even with those goals, if Hubble is any example, JWST’s most amazing discoveries will actually be things that we cannot even imagine today.

Read all about the history of ground and space-based telescopes at our Amazing Space site “Telescopes from the Ground Up.”

As an astronomer, one of the truly rewarding parts of my job is to share new scientific discoveries with other astronomers. We typically do this at meetings where we give short, 15-20 minute presentations on our recent research. I usually find these meetings to be very valuable, since I can form new collaborations and get involved in cutting-edge research projects.

Recently, I found myself in a different role, as the chief scientific and local organizer for one such meeting, a major international conference. The meeting brought together almost 200 astronomers from across the world to share in “Frontier Science Opportunities with the James Webb Space Telescope.”

The process of organizing a big meeting such as this begins more than nine months before the actual meeting. Late last year, we formed a “Scientific Organizing Committee” (SOC) consisting of a dozen members of the astronomical community, including myself.

We decided that we would like to jump-start a discussion of high impact science programs that the James Webb Space Telescope (JWST) could perform when it launches later this decade. The goal is to get astronomers actively thinking about the telescope, so we can jump into the science quickly when it’s ready.

Next, the SOC selected about a dozen speakers and invited them to the meeting to share the diverse research topics that Webb could address. With this list of experts posted, we opened up registration in January 2011. The community responded with a flood of interest. We received dozens of requests for contributed talks and presentations. Over the past few months, I have been involved in scheduling the meeting, organizing the discussion sessions, and planning a dinner for our guests at the Maryland Science Center with a screening of the “Hubble 3D” IMAX movie.

The payoff for all of the work came when the first science talk began. The topic was how Webb could improve our understanding of the atmospheric structure of nearby planets, such as Uranus and Neptune. The next talk told us how Webb could enable discovery of the first stars that exploded in the universe, through imaging of “Pair Instability Supernovae.” We were off to a good start! With the first two talks, we had covered a range extending from the nearest objects in the universe to some of the farthest away.

The conference continued for three full days and paved the way for a very exciting Webb science case that touches on many different topics: studying extrasolar planets and their atmospheres; learning how galaxies come together by mapping the ages, motions, and chemical nature of their stars; and discovering the first galaxies that emerged when the universe was in its infancy. Although some of these science goals are similar to those defined for Webb years ago, the presentations at the meeting provided a rejuvenated interest in these endeavors. In fact, many of the science cases have become stronger in light of recent research in these fields.

We discussed the criteria astronomers would use for future discoveries with Webb. If we find a planet with water vapor in its atmosphere, what kind of other criteria would be needed to declare that planet potentially life-bearing? When we’re looking at the most distant stars in space, what litmus tests must they pass before we can determine that we’re looking at the universe’s very first stars?

“Frontier Science Opportunities with JWST” also revealed that astronomers have a lot of homework to do before the telescope launches into space. Participants emphasized the fact that we have precious resources in astronomy right now that could be used to observe the types of exotic objects Webb will study. We could make those observations now and have a wealth of additional data for astronomers to study in conjunction with the eventual Webb observations – just as space telescopes like Chandra and Spitzer have been used to provide complementary observations for Hubble. One of my goals for the next few years will be to investigate this further and come up with a plan to ensure that we fully capitalize on our existing missions to make Webb that much more successful.

Want to know more? All of the talks and Powerpoint slides for “Frontier Science Opportunities with JWST” are posted at http://webcast.stsci.edu/webcast/.

1995 Hubble observation of globular star cluster 47 Tucanae.

Last month, almost 3,000 astronomers came together in Seattle as a part of the 2011 American Astronomical Society (AAS) winter meeting. The AAS meetings are a great venue for astronomers to share their recent research findings and form new collaborations to tackle unsolved problems in astrophysics.

The meetings are packed with a range of activities, including sessions in the morning and end of each day that everyone attends, and multiple sessions throughout the day touching on every theme in astrophysics research. I always find that one of the keys to surviving an AAS meeting is to plan which sessions I attend well in advance, so I know exactly where to be at what time.

One of the reasons that I attended this year’s AAS meeting was to present the first results from an exciting new study that our team just undertook with Hubble. Most of the presentations at the AAS are in the form of Powerpoint talks and are restricted to just five minutes. The idea is to give a “punch line” of your research, and excite folks in the audience so they come and chat with you afterward to get more details.

I normally give a talk at these meetings in one of these sessions, but I decided to present a poster this year instead.

The poster presentations take a completely different format than the oral talks. On each day of the meeting, hundreds of astronomers enter the convention center hall first thing in the morning and tack their posters up on boards. Then, throughout the day, other astronomers visit and ask questions, and we discuss the scientific results together. I ended up chatting with dozens of astronomers about my poster throughout the day. At the end of the day, all of the posters are taken down and a new set starts the next day.

I made my poster a few weeks before the meeting. It included pictures, plots, and text that described our new study. The research project described on the poster represents one of my favorite topics, ultra-deep imaging of faint stars in nearby star clusters. The particular cluster that we studied, called 47 Tucanae (47 Tuc), contains over 100,000 stars packed into a tiny region of space. If our planet was in 47 Tuc, we would never see night. Various stars would rise and set throughout the day, every day.

Our study of 47 Tuc is unique. We used three different cameras on two Hubble instruments and obtained the deepest ultraviolet, optical, and infrared images of the star cluster to date. Our images have revealed the faintest hydrogen-burning stars in the cluster, stars that have 10 times less mass than the Sun. Our study is also the first to find all of the “dead” stars in the cluster, faint stellar cinders of once brilliant massive stars that now have no nuclear fuel. Finally, our imaging was so deep that it actually uncovered very low mass stars in a galaxy that is orbiting the Milky Way. The galaxy, called the Small Magellanic Cloud, can be seen with the naked eye in the southern skies and sits behind 47 Tuc, almost at the edge of our galaxy.

Since coming back from the AAS meeting, I’ve received several e-mails from astronomers expressing interest in our 47 Tuc results. We are now writing scientific papers so these scientists can read all of the details of our investigation in astronomical journals. At next year’s AAS meeting, I plan to present something new to the community. And even though it’s a year away, I’m already excited.

White dwarf star, Sirius B (circled), with its bright companion, Sirius A.

My name is Jason Kalirai and I am a 32-year-old assistant astronomer at the Space Telescope Science Institute (STScI).  I joined the team at STScI about two years ago, after spending four years at the University of California in sunny Santa Cruz as a Hubble Fellow postdoctoral researcher. Prior to that, I was a graduate student at the University of British Columbia in Vancouver. Yeah, I am a Canadian … eh!

As a professional astronomer, I split my time between researching various interesting problems in astrophysics and doing my part to help ensure that current and future telescopes are built and operate correctly. On the research side, I enjoy tackling problems related to how stars like the Sun evolve over time and give back to their surroundings. It turns out that 98% of all stars are actually similar to the Sun — some a few times bigger and some a few times smaller — and will end their lives by slowly shedding their outer layers. When this process is completed, the only thing remaining of the stellar cinder is its core, a small object about the size of the Earth, which is very dense and has no more nuclear fuel.

We call this core a white dwarf star, and studying the properties of these objects is kind of like archaeology. We can use the stars to date the first objects that formed in our galaxy, figure out how much mass our galaxy has, and test models that predict how matter should behave under extreme conditions.

Oh yeah, and those other 2% of stars that don’t make white dwarfs — well, they blow up as violent supernova explosions, and are also exciting to learn about!

One of the reasons I really wanted to come to STScI was to work on the James Webb Space Telescope.  JWST, or Webb as it’s commonly referred to, is the next big telescope that NASA will launch. It’s much bigger than Hubble and will see infrared light that Hubble cannot.

But when I arrived at STScI in late 2008, they asked me to work on one of the brand-new instruments that was about to be installed in Hubble during Servicing Mission 4: the Wide Field Camera 3 (WFC3).  I was very excited about this opportunity and have been leading the WFC3 photometry group for the past two years.  Still, I always saw myself moving over to Webb in the near future.

My move from Hubble to Webb happened sooner than I thought.  A few months ago, I was selected as the new STScI Deputy Project Scientist for Webb and am now coming up to speed with the status of the project. There are many ways that I can get involved and help the project out. One of the best parts of my new job will be sharing information about the project with both astronomers and the public, and educating teachers on the exciting capabilities that Webb has for advancing our knowledge of the universe. I am looking forward to this as I enjoy public outreach very much, and have been actively involved in it for several years.

Outside of astronomy, life is very busy these days.  Almost all of my time is focused on entertaining my two energetic twin daughters, Mira and Suriya. The girls just turned two a few months ago and are always the center of action at our home. I’ve already started putting really cool astronomy images in their room, and I think they really like them — especially the pictures of planets in our solar system. This summer, I plan to buy them their first telescope (a fancy one) and show them the same planets, stars, and galaxies that we will study in exquisite detail with Hubble and Webb.