STS-67 Day 3 Highlights

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On Saturday, March 4, 1995 at 6 a.m. CST, STS-67 Payload Status Report # 05 reports: (2/5:22 MET) The Hopkins Ultraviolet Telescope (HUT) led the observations of several celestial objects, starting with AX Persei, a double star system consisting of a red star paired off with a blue star in what is known as a symbiotic binary. This means that the two stars differ greatly in their temperature ranges. They are believed to be a pair in which gas from a large, cool star falls onto a smaller, but more massive companion. Not much is known about how these stars interact, and data from these observations will help improve current measurements of the hot star component's temperature and gas emissions.

The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) also obtained "great observations" of the AX Persei star system, according to WUPPE guest investigator Dr. Regina Schulte-Ladbeck. In a live interview with TV station WPXI in Pittsburgh, Pennsylvania, Dr. Schulte-Ladbeck described the instrument's view of the stellar pair as "picture perfect from an operational point of view."

Dr. Schulte-Ladbeck also used HUT and WUPPE to obtain spectral measurements of a Wolf-Rayet star known as EZ Canis Majoris. Wolf-Rayet stars are thought to represent one of the final phases of evolution in massive stars that are between 100,000 and 1,000,000 times as bright as the Sun. Wolf-Rayet stars have powerful stellar winds, or emissions of ionized gas, that quicken the stars' aging process. The composition of these stellar winds is also important because the elements they contain play a significant role in forming the basic chemistry of life. According to Dr. Schulte-Ladbeck, last night's measurements alone, of the strength and composition of this stellar wind, have already yielded "more information about EZ Canis Majoris than we ever got on Astro-1."

The Astro-2 scientists also turned their attention to one of their prime targets of investigation, the brightest known Seyfert galaxy, NGC 4151. Seyfert galaxies are known for their extremely bright and compact centers and radiate energy most strongly in the ultraviolet and X-ray wavelengths.

Ultraviolet Imaging Telescope (UIT) observations included images of a globular cluster, NGC6752, and a spiral galaxy, M101. Globular clusters are collections of relatively old stars, and they are particularly suitable for observations by UIT due to the presence of hot stars which emit most of their radiation in the ultraviolet range. This enables UIT astronomers to locate hot white dwarf stars, hot binary systems and objects associated with sources of X-rays.

Spiral galaxies, like our Milky Way, are flattened discs with central bulges or nuclei from which the galaxies' arms extend. M101 is a big spiral galaxy with spiral arms that are not tightly wound. UIT's ultraviolet imaging offers a powerful new tool for the study of this spiral structure, since it emphasizes hot stars, hydrogen and dust.

Early in the morning, the Astro-2 instruments made observations of the Cygnus Loop, a middle-aged supernova remnant. A supernova is one of the most powerful explosions in the universe, and it occurs at the end of a very massive star's life after the star's fusion reaction stops. The Cygnus Loop is of particular interest because it reveals details about the structure and speed of shock waves from the explosion as they travel through the interstellar medium.

Jupiter had became a focus of investigation earlier in the evening, especially for the HUT science team who obtained very good spectral data on the planet's equator. The planet is believed to have a reservoir of heat energy left over from its creation, since Jupiter radiates twice as much energy as it receives from the Sun. HUT scientists are particularly interested in the planet's immense magnetosphere, a region of charged particles controlled by Jupiter's magnetic field.

On Saturday, March 4, 1995 at 1 p.m. CST, STS-67 MCC Status Report # 06 reports: During the past shift, the crew received word from scientists who designed the Australian ultraviolet experiment that is flying in two Getaway Special canisters in the cargo bay. The experimenters reported they have achieved 100 percent of desired observations and expressed a sincere thanks and appreciation for the support they received during this mission. In addition, Jernigan and Lawrence participated in an interview with National Public Radio as Durrance supported the Astro-2 observations.

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