Speaking of Hubble...

Archive: February 2011

The 3,000

February 22, 2011 by Jason Kalirai
Globular Cluster 47 Tucanae

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.

Seeing Stars

February 16, 2011 by Jason Kalirai
White dwarf star, Sirius B (circled), alongside its bright companion, Sirius A.

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.