GLPA Newsletter 2009 4 issues — 116 pages Volume XLIV, Number 1 Vernal Equinox, 2009 Cover: Infant Stars in the Small Magellanic Cloud
Hubble astronomers have uncovered, for the first time, a population of infant stars in the Milky Way satellite galaxy, the Small Magellanic Cloud (SMC, visible to the naked eye in the southern constellation Tucana), located 210,000 light-years away.
Hubble’s exquisite sharpness plucked out an underlying population of infant stars embedded in the nebula NGC 346 that are still forming from gravitationally collapsing gas clouds. They have not yet ignited their hydrogen fuel to sustain nuclear fusion. The smallest of these infant stars is only half the mass of our Sun.
Although star birth is common within the disk of our galaxy, this smaller companion galaxy is more primeval in that it lacks a large percentage of the heavier elements that are forged in suc- cessive generations of stars through nuclear fusion.
Fragmentary galaxies like the SMC are considered primitive building blocks of larger galaxies. Most of these types of galaxies existed far away, when the universe was much younger. The SMC offers a unique nearby laboratory for understanding how stars arose in the early universe. Nestled among other starburst regions with the small galaxy, the nebula NGC 346 alone contains more than 2,500 infant stars.
The Hubble images, taken with the Advanced Camera for Surveys, identify three stellar popula- tions in the SMC and in the region of the NGC 346 nebula — a total of 70,000 stars. The oldest population is 4.5 billion years, roughly the age of our Sun. The younger population arose only 5 million years ago (about the time Earth’s first hominids began to walk on two feet). Lower-mass stars take longer to ignite and become full-fledged stars, so the protostellar population is 5 mil- lion years old. Curiously, the infant stars are strung along two intersecting lanes in the nebula, resembling a “T” pattern in the Hubble plot.
The observations, by Antonella Nota of the European Space Agency (ESA) and the Space Tele- scope Science Institute (STScI), Baltimore, Maryland, were recently presented at the meeting of the American Astronomical Society in San Diego, California.
The other science team members are: M. Sirianni (STScI/ESA), E. Sabbi (Univ. of Bologna), M. Tosi (INAF - Bologna Observ.), J.S. Gallagher (Univ. of Wisconsin), M. Meixner (STScI), M. Clampin (GSFC), S. Oey (Univ. of Michigan), A. Pasquali (ETH Zurich), L. Smith (Univ. Col- lege London), and R. Walterbos (New Mexico State Univ.).
Antonella Nota, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD. 21218, (phone) 410-338-4520, (fax) 410-338-4579, (e-mail) [email protected] or Marco Sirianni, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, (phone) 410- 338-4810, (fax) 410-338-4579, (e-mail) [email protected].
Credit: NASA, ESA and A. Nota (STScI/ESA)
Greetings for the Vernal Equinox and the International Year of Astronomy 2009! I hope that you have wintered the previous PRESIDENT’S season well and that your plans for IYA 2009 are flowing smoothly. I personally enjoy the variety of planetarium shows MESSAGE and astronomical topics we share with our visitors but one of my favorites has always been the major discoveries of Galileo. Cheri Adams I love having the opportunity of IYA 2009 to celebrate the 400th anniversary of Galileo’s use of a telescope to observe. At our museum, we invite the public to attend astron- omy programs on the third Friday of each month in the plane- tarium in addition to the observing we do every clear Friday evening in our observatory. The themes for our events this year center on the discoveries of Galileo, telescopes, and observing our night sky. Our March presentation, which occurs on the Vernal Equinox, will focus on our local skies, demonstrating how to make good lighting choices, promoting our participation in the weekend for 100 hours of astronomy, and demonstrating how our visitors can participate in the GLOBE at Night campaign and Earth Hour. It is very helpful to have the range of nights March 16-28 to check the magni- tude of Orion’s stars for the GLOBE at Night project as our spring ushers in many hazy night skies. IYA 2009 commemorates more than Galileo’s observations. We are also celebrating the 400th anniversary of Ke- pler’s publication of Astronomia Nova. How timely that as IYA progresses, we will observe Mars increase in its bright- ness and then be able to discuss the great observations of Brahe and how Kepler used those to then scientifically explain planetary motion. Another timely celebration for IYA is the 350th anniversary of Huygen’s publication of Systema Saturnium. Even with a small telescope today, Saturn’s ring system can be observed so it may seem very strange that the majority of the reactions to this book at the time of its release was negative. The wealth of information released from the Cassini- Huygens Mission is nearly overwhelming and breathtakingly beautiful. Our planetarium visitors never seem to tire of learning more and neither do we. How fortunate I feel to live in a time where such tremendous advances have been made
(continued on page 16)