The Hubble Space Telescope

The development of the spectroscope in the mid-19th century allowed chemists to explore emissions of visible light by extraterrestrial objects such as stars as well as absorption (Fraunhofer lines) by the Earth s atmosphere and that of the Sun. Helium was discovered during the total solar eclipse of 1868 by its emission. Other elements were discovered in the solar atmosphere by matching of their Fraunhofer lines. Between 1937 and 1941 visible emissions were assigned for three interstellar molecules CH (430.0 nm), CH (423.2 nm), and CN (a series of lines). There were very limited opportunities to observe ultraviolet spectra ( 400 nm) from space because stratospheric ozone absorbs most of the UVB fight (320- 

290 nm) and all UV light of wavelength shorter than 290 nm. The birth of radioastronomy in 1951 provided a means for monitoring microwave emissions from interstellar molecules and vastly increased the knowledge of space chemistry. The absence of UV spectra still left a large gap that could be explored briefly by small sensors on rockets or space satellites. Although H2 is the most abundant molecule in space, it eluded observation until its detection in March 1970, in a dark space cloud by a far ultraviolet (FUV, 100-140 nm) spectrometer aboard a rocket. This observation was confirmed in 1973 by the Copernicus satellite. 

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Some graphite-epoxy structures can be tailored to have a zero coefficient of thermal expansion, a big advantage for large antennas that must pass in and out of the sun, yet maintain dimensional stability for accuracy of pointing the signal. For example, a graphite-epoxy truss is used to stabilize and support the Hubble Space Telescope. 

Figure 3.12 Line of sight through three Giant Molecular Clouds to the Hubble Space Telescope. (Reproduced by courtesy of StscI and NASA)...

The spectral features observed by astronomers have led to the classification of stars into seven broad classes outlined in Table 4.1, together with their surface temperatures. The highest-temperature class, class O, contains may ionised atoms in the spectrum whereas the older stars in class M have a much lower temperature and many more elements present in the spectrum of the star. Observation of a large number of the stars has lead to extensive stellar catalogues, recently extended by the increased sensitivity of the Hubble Space Telescope. Making sense of this vast quantity of information is difficult but in the early 19th century two astronomers... 

Fig. 3.8. Profiles of interstellar absorption lines observed in the line of sight to the star HD 93521 with the Goddard high resolution spectrograph at the Hubble Space Telescope. Solid lines are theoretical profiles based on cloud velocities indicated by the tick marks at the top dots indicate the data points. After Spitzer and Fitzpatrick (1993). Courtesy Ed Fitzpatrick.

How can absorption and emission spectra be used by the Hubble space telescope to study the structures of stars or other objects found in deep space ... 

This investigation, involving the most up-to-date instruments such as the Hubble Space Telescope, led to the following conclusion the data disagree strongly with the hypothesis that the Universe is flat and contains no quintessence, thus ruling out one of the most favoured cosmological models. 

Images of a bipolar jet from a protostar taken by the Hubble space telescope. Evolution of the jet with time is visible between the three images. 

Studies of old stars, such as HD140283, have been made quite recently. This star is considered to be so old that it has only about % of the oxygen and other heavier elements that the sun has. About 1000 times more beryllium has been found than possibly could be attributed to cosmic radiation, These observations were essentially confirmed by one of the early experiments using the Hubble Space Telescope. These observations will contribute to further unraveling the remaining problems pertaining to the origin of the universe. 

This image of the Crab Nebula taken by the Hubble Space Telescope shows enormous interstellar gas clouds, in which spallation reactions may be taking place. 

Let us only remark that excellent progress has been recently made toward the measurement of Hq through the Hubble Space Telescope. Consistently with current estimates, the result favors the following value 72 2 7 km/s/Mpc (Freedman Turner, 2003). 

Kant was essentially correct, Bob says. In the last years of the twentieth century, the Hubble Space Telescope (HST) revealed several dozen disks at visible wavelengths in the Orion Nebula, a giant stellar nursery about 1,600 light years away. We call them proplyds, a contraction of the term protoplanetary disks. The Orion proplyds are larger than the Sun s solar system and contain enough gas and dust to provide the raw material for future planetary systems (figure 6.1). 

Assessment of Options for Extending the Life of the Hubble Space Telescope Final Report (SSB with ASEB, 2004) Exploration of the Outer Heliosphere and the Local Interstellar Medium A Workshop Report (2004)... 

Isotopes in interstellar gas With the aid of the Hubble Space Telescope it has been possible for the first time to measure the boron isotopic ratio within diffuse clouds of the Milky Way. The interstellar ultraviolet radiation renders B ionized (B+) in the diffuse clouds therefore its spectrum is similar to that of the element Be, but at shorter wavelengths. The strongest resonance line lies in the ultraviolet, visible to Hubble spectrometers. The smaller mass of the 10B isotope shifts its line by 0.013 A (about 0.001%) toward longer wavelengths. Very detailed analysis of the line pair has shown in several clouds that today s interstellar abundance ratio is UB/ 10B = 3.4 0.7, which is consistent with the solar ratio 4.05. For the first time one can conclude that the solar ratio is not an abnormal one, but is shared by interstellar gas at a value larger than the ratio 2.5 that is produced by cosmic-ray collisions in the interstellar gas. Another source of11B is needed. 

Figure 1.1 A cosmic cloud of hydrogen, where stars are bom, in the form of a pillar, as seen by the Hubble Space Telescope. The globules are forming stars. This picture of this cloud, in Ml 6, was taken by John Hester and P. Scowen in 1995.

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