Thursday, March 26, 2009

CHIPS and Interstellar Bubble

A thin, over 40 meters high Boeing Delta II stood on its launching station in Florida in the evening of January 12. 2003. The heavy load on the rocket included also a little only 60 kg weighing CHIPS satellite (Cosmic Hot Interstellar Plasma Spectrometer).
Exactly at 19:45 EST the Rocketdyne RS- 27A main engine was started. It was assisted by four Alliant Techsystem GEM graphite-epoxy supporting engines pressing more power to the fiery flames. Delta II runs mostly on liquid oxygen. The noisy lift is at first slow but it catches up speed quickly. 83 minutes from the launch the rocket had reached the elevation of 560 km and the small CHIPS was relaesed to its own orbit. People felt great relief in the honorable Berkeley Space Research Center (est. 1956) in the University of California when the radiosingal of the satellite was heard 13 minutes after it was released.

CHIPS was about the size of a large suitcase and gets the energy it needs from sun panels. It had nine very accurate spectrometers that measured space radiation from carefully selected frequencies. Thin aluminium and polymer filters protect the instruments measuring the radiation sot that there would not be overload that could choke them. During the 12 months mission the satellite collected information for about one GB. This hits a single Exatype tape using the FITS data format.

CHIPS spectrometers are extremely sensitive. The engineers working with it in Kennedy space center did not allow a single speck of dust penetrate the radiation measuring instruments. The satellite is LEO (low-earth-orbiting) and it is not possible to fix any faults in the system after it has been launched to its orbit. There is only a single chance to succeed. Carelessness may be very expensive since, in addition to the cost of CHIPS itself there is the list price of the lifting rocket payload. In 2003 a two-stage Delta II with four additional GEMs was 42 million dollars. The institutes and organizations joining in the same launch divide the expenses between themselves. CHIPS project was financed by NASA itself.

Dr. Mark Hurwitz directs the CHIPS project in Berkeley. He explains the mission:

”CHIPS does spectroscopy on the diffuse background radiation on the entire sky in the 90 - 260 Å wavelength l/150 (about 0.5 eV) top resolution. The information gathered by CHIPS helps scientists to define the temperature of the electrons in the plasma of the local interstellar bubble which is assumed to be about million degrees Kelvin, as well as the state of ionization and cooling mechanisms. Majority of the light from the diffuse million degrees hot plasma is expected to come from the little known wavelengths that CHIPS is measuring, so the data is significant to the study of many internal and external galactic astrophysical environment.”

The simplified drawing published by the CHIPS project shows the interesting target of the mission. We can see a peanut shaped "Local Bubble" that surrounds us in the space. It is about 300 light years in diameter and there are two stars inside it. One is our Sun and the second one is the beta Canis Maior.

Notice how our bubble touches the bottle shaped bubble which contains the Antares of Scorpio, a red star that competes at night sky with planet Mars. Antares is a red giant or M-star that is quickly approaching its explosion point.

Further back in the picture we can see the bright Betelgeuse in Orion. This is also red giant, largest M-star known to astronomy. The diameter of Betelgeuse is not less than 800 times that of our Sun - most of the M stars are ten or maximum 500 times the size of Sun. The mass of Betelgeuse is 20 times that of Sun. Once the enormous nuclear reactor inside the star runs out of hydrogen it means the death of this star Betelgeuse. The explosion creates a brilliant supernova that can emit more light for a moment than an entire galaxy.

The study of the interstellar bubble yielded results but Dr Horowitz and his colleagues do not seem to be overly enthusiastic. There are so many sources of radiation in space that even in narrow-slid mode the detection of distant bubble plasma is very difficult. An abstract and the full text in pdf-format of the highly technical report is in here.

The concept of interstellar bubbles is probably unfamiliar to many. However, it gives a wonderfully 3-dimensional view of the sky which we naturally tend to see two dimensionally as a surface with bright dots in constellations. It is not easy to conceptualize the third dimension that is emphasized by these amazing bubbles created by our God.

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