Images of Galaxies and Stars outside the Visible Light Range Part-4 - Remote Sensing Application - Completely Remote Sensing, GPS, and GPS Tutorial
Images of Galaxies and Stars outside the Visible Light Range Part-4

Some of the radio telescope images look remarkably like those made from telescopes imaging at much shorter wavelengths. A case in point is this image of a supernova, SN2009bb, with a ring of ejected material, as image by a VLA telescope bank:

SN2009bb.

A longer wavelength radio image acquired by the MERLIN VLBI system shows the binary star pair SS433. Contour lines show the extent of radio wave activity outside the central region occupied by the star pair.

The binary star pair SS433 as imaged by the Jodrell Bank Radio Telescope.

Radio telescopy can identify various organic compounds in space. A spectacular result, using MERLIN, was found in observing a star in the Milky Way from which a gas plume 463 billion kilometers (288 billion miles) long emanates. A large part of that plume is composed of methanol (methyl alcohol; not "ethyl", the drinkable kind - Distillers of the World, Sorry!):

A plume (blue) of methanol extending from a star, as seen by the MERLIN radio telescope.

The Red Giant Star Betelguese (see page 20-2) has been imaged within the microwave region (outside the main radio interval) at 7 mm. Under these conditions it was possible to measure a temperature profile (right) in the expanded gas envelope (photosphere) around the star.

Radio Image of the Red Giant Beteleuse, made at 7 mm, with a plot of the temperature gradient in its outer shells.

Supernovae (see page 20-6) are strong sources of radio waves. They expand so rapidly that time lapse images taken months apart can monitor their spread and the changes in shape of the radio wave field. Here is such a sequence for Supernova SN1993J in the galaxy M81. The images on the left were taken at 3.6 cm; those on the right at 6.0 cm.

Sequence of Radio Telescope images of Supernova SN1993J taken over a two year interval.

As more radio telescope images of galaxies have accumulated, a distinct pattern has been found with galaxies having a powerful central Black Hole (see page 20-6). One or more powerful jets (material being expelled at speeds approaching that of light) are the hallmark of this type. Below is a series of panels picturing different radio galaxies that show these lobes of ejected materials.

Images made from radio telescope signals of galaxies that are emitting hypervelocity material as distinct jets and lobes.

The reader might have had a thought during this review of radio astronomy: Why not put a radio telescope in space? But, wouldn't the antenna have to be much larger than is commonly on satellites? The answer is "No" if the VLBI concept (above) is employed. The Japanese Space Program has developed and launched HALCA (Highly Advanced Laboratory for Communications and Astronomy) in February 1997 as the kingpin in their VSOP (VLBI Space Observatory Project) program. The radio satellite has a 25 m antenna and looks like this:

Artist's Rendition of the HALCA Spacecraft in orbit.

HALCA's orbit is elliptical, with its perigee (closest approach) at 1000 km and apogee (farthest) at 20000 km. When coupled electronically with one or more radio telescopes on the ground, the effective diameter of the joint system is greater than that of the Earth itself (12755 km). This creates a very high resolution radio wave detector (in some applications, 1000x better than the HST) when used in the Interferometer mode. Although HALCA experienced some trouble in 1999, it did send back considerable data and proved the concept of using multiple integrated radio receivers to achieve exceptional resolution. Here are three images of quasars (see page 20-6) at considerable distances from Earth that illustrate one of the ways in which HALCA data can be displayed:

Distribution of radio signals around three quasars; data obtained using HALCA as part of the VSOP system.

Plans to put other radio telescopes in space are now active. JPL has a brief synopsis of the forthcoming Space Interferometry Mission (SIM) on its SIM web site.

Since we have introduced the specialized technique of interferometry on this page, it is now appropriate to revert back to imaging in the visible spectrum to mention the CHARA (Center for High Resolution Astronomy; operated by Georgia State Univ. astronomers) project which is now commencing operation at the famed Mt. Wilson Observatory (in the mountains north of Los Angeles), shown here:

The Mount Wilson Observatory near Pasadena, CA, with the dome of the 100-inch telescope, and several of the CHARA telescopes.

The large central observatory dome houses the famed 100 inch Hooker telescope that Edwin Hubble used to track down galaxies outside the Milky Way and to measure redshifts, laying the foundation for the Big Bang model. In the above picture are several of the 6 auxiliary optical telescopes tied to the main telescopes. Working in pairs, and later in larger combinations, light from separate components of the array must be combined and synchronized to produce interferometric images in which the waves reenforce rather than cancel. This multiple system produces a baseline (at optimum, 1080 feet) that greatly increases the angular resolution of the central telescope, thus providing images that are expected to exceed the Hubble Space Telescope in sharpness. To get the signals from two or more telescopes into coincidence (the light arrives at any two pairs at slightly different times), one beam is sent through an optical pipe that contain movable mirrors mounted on rails (the "delay line"). The mirror(s) are moved until the extra distance traveled by light to the second telescope (relative to the first) is just compensated enough (equalized) to bring the two signals into phase. This delicate adjustment is made through a computer program that controls pathway adjustments.

One of the most unusual observatory systems now operating productively is AMANDA-II (Antarctic Muon and Neutrino Detector Array), designed to not only detect neutrons but to locate them in the celestial sphere and possibly associate any concentrations of neutrons with discreet sources. The AMANDA is a series of more than 600 glass optical detectors buried in the solid ice 1.5 km below the surface. Here is the first preliminary map of results:

First results of neutrino sources detected by AMANDA-II in the southern celestial sphere.

So far, some of these blue dot point sources have been matched with galaxies; others have yet to be correlated with known sources. The neutrinos seem to be generating in the interiors of large galaxies, particularly those with suspected supermassive Black Holes. However, the thick blue band near the equator relates to the Milky Way, which demonstrates other possible stellar sources.

Astronomy and Cosmology are live and well! Space Observatories are being planned for the next decade or so. Here is a partial list - Click on each to go to its Web Home Page: Herschel; James Webb Space Telescope; Kepler; Laser Interferometer Space Antenna; Nuclear Spectroscopic Telescope Array; Planck Surveyor; Single Aperture Far Infrared Observatory; Space Interferometry Mission; Supernova Acceleration Probe; Wide-Field Infrared Survey Explorer

Ground telescopes are being improved, as new ones are built. Here are several:Atacama Large Millimeter Array; Large Binocular Telescope Interferometer; Large Synoptic Survey Telescope; Pan-STARRS; Square Kilometer Array (radio telescope)

With this examination of observatories that collect data over different parts of the spectrum, we now return to the exposition of aspects of Cosmology by looking next at the some special topics relating to galaxies.

Source: http://rst.gsfc.nasa.gov/