2005 Feature of the Month Archive

DEM L316: Celestial Odd Couple

This is a composite X-ray (red and green)/optical (blue) image of two hot gas shells produced by supernova explosions. Although the shells appear to be colliding, Illinois astronomers Rosa Williams and You-Hua Chu have discovered that it may be an illusion. X-ray spectra obtained with NASA's Chandra X-ray Observatory show that the shell of hot gas on the upper left contains considerably more iron than the one on the lower right. This implies that stars with very different ages exploded to produce these objects. The remnant on the upper left is from an old white dwarf star in a binary system, and the one on the lower right is from a much younger massive star, so the apparent proximity of the remnants is probably the result of a chance alignment.

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Caption Credit: Harvard/SAO
Image Credit: NASA/CXC/U.Illinois/R.Williams & Y.-H.Chu (X-ray),
NOAO/CTIO/U.Illinois/R.Williams & MCELS coll. (Optical)

Supernova Remnant N63A Menagerie

A violent and chaotic-looking mass of gas and dust is seen in this Hubble Space Telescope image of a nearby supernova remnant. The object is a member of N63, a star-forming region in the Large Magellanic Cloud, an irregular galaxy lying 160,000 light-years from our own Milky Way galaxy. Denoted N63A, the supernova remnant is the remains of a massive star that exploded, spewing its gaseous layers out into an already turbulent region.

Supernova remnants have long been thought to set off episodes of star formation when their expanding shock encounters nearby gas. Data obtained at infrared, visible, and X-ray wavelengths by Illinois astronomers You-Hua Chu and Rosa Williams and their collaborators reveal on-going formation of stars at 10-15 light-years from N63A. In a few million years, the supernova ejecta from N63A would reach this star formation site and may be incorporated into the formation of planets around solar-type stars there, much like the early history of the solar system.

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Caption Credit: The Hubble Heritage Team (STScI/AURA)
Photo Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)
Acknowledgment: Y.-H. Chu and R. M. Williams (UIUC)

Congrats to our Recent PhDs!

The Astronomy Department would like to offer its congratulations to our recent PhD graduates. Earning their PhDs this past summer were:

Ian O'Dwyer (Advisor: Ben Wandelt)

Statistical Analysis of the Cosmic Microwave Background: Power Spectra and Foregrounds

Vasiliki Pavlidou (Advisor: Brian Fields)

An analytic model for environmental effects on cosmic structure formation and an application to cosmic accretion shocks

Konstantinos Tassis (Advisor: Telemachos Mouschovias)

Protostar formation in magnetic clouds: the phase beyond ion detachment

Yen-Ting Lin (Advisor: Joe Mohr)

Fundamental Properties of Galaxy Clusters: A Prelude to Large Scale S-Z Effect/Near-IR Surveys

Congrats to our Recent Graduates!

The Astronomy Department would like to offer its congratulations to our Class of 2005: Jonathan Seale, Emily Byrne, Holly Shupp, Emily Beal, Conley Ditsworth, Chris Hall, and Sean Wilson. All the best in your future endeavors! You make us proud!

Are Super-star Clusters Born Small?

A trio of massive, young star clusters found embedded in a star cloud suggests that super-star clusters (with a total mass of up to 1 million times that of the sun) may be formed by the coalescence of smaller clusters. This discovery was presented by Professor You-Hua Chu and Ms. Rosie Chen of Illinois and Professor Kelsey Johnson of the University of Virginia at the January 2005 American Astronomical Society meeting in San Diego.

Hubble Space Telescope images of the core of NGC 5461 revealed a tight group of three massive clusters surrounded by a cloud of stars within a region about 100 light-years in diameter. The tightly packed group of clusters was found within an arm of the giant spiral galaxy M101, located about 23 million light-years away in the constellation Ursa Major (the Big Dipper).

The large amount of mass at the core of NGC 5461 produces a strong gravitational field, causing the clusters and stars to move and interact dynamically. Eventually, the clusters and surrounding star cloud will merge into one single star cluster. Simulations of the evolution of the clusters at the core of NGC 5461 by Illinois professor Paul Ricker show that these clusters may merge within a few million years.

Credit: University of Illinois News Bureau; Photo Credit: NASA, Y.-H. Chu and R. Chen (UIUC), and K. Johnson (UVA)