Where Do the Images Come From?


Visible (DSS)

Visible-light images from the Digitized Sky Survey (DSS), a project at the Space Telescope Science Institute to scan and digitize photographic plates taken over the entire sky. The source plates were obtained with two 1.2 m telescopes: the Oschin telescope at the Palomar Observatory in Southern California (north), and the UK Schmidt telescope in Australia (south). The original plates were taken in either red light (645 nm) (Palomar) or in blue (405 nm) (UK Schmidt), and the resulting images have pixel sizes of 1.7 arcseconds square. Exposure times vary between 40 and 120 minutes.


Visible (TIE)

Visible-light images taken by students worldwide through the Telescopes in Education (TIE) program, a collaboration between the Mount Wilson Institute and the Jet Propulsion Laboratory. The images were obtained with a remotely-controlled 24-inch reflector at the Mount Wilson Observatory (Southern California), and were taken through a 550 nm (green light) filter. The pixel size is about 0.25 arcseconds, and typical exposure times are less than a minute.


Near-Infrared - 2MASS

The near-infrared (NIR) images were obtained by the Two-Micron All-Sky Survey (2MASS), an ongoing effort to map the entire sky at J-band (1.25 microns), H-band (1.65 microns) and K-band (2.17 microns) wavelengths. The 2MASS survey is led by the University of Massachusetts, with all data and images processed at Caltech's Infrared Processing and Analysis Center (IPAC). The survey utilizes two nearly identical 1.3-meter telescopes located on Mount Hopkins (Arizona) and on Cerro Tololo (Chile). While the pixel size is 2.0 arcseconds, the survey strategy of over-sampling yields an effective resolution of about 1 arcsecond. Exposure times are 7.8 seconds.


Mid-Infrared - IRAS

The mid-infrared data were obtained with the InfraRed Astronomical Satellite (IRAS) in 1983. This was the first space-borne infrared astronomy satellite, and was an international collaboration between the US, the Netherlands and the UK. IRAS mapped nearly the entire sky at four wavelengths, including 12 microns (millionths of a meter) and 25 microns in the mid-infrared. Since infrared detector technology was still relatively immature at the time of this path-breaking mission, the spatial resolution for the mid-IR images is rather modest. The IRAS detectors were rectangular in shape, and had relatively large fields of view (about 0.75 arcmin wide and 4.5 arcmin long). The mid-IR images depicted in the Museum resulted from high-resolution processing, in which sky coverage and sophisticated mathematical algorithms combine to yield effective resolutions of about 0.5 arcmin. The odd elliptical shape of many mid-infrared emission peaks is a consequence of the underlying rectangular detectors used by IRAS.


Far-Infrared - IRAS

The far-infrared (FIR) data were obtained with the InfraRed Astronomical Satellite (IRAS) in 1983. This was the first space-borne infrared astronomy satellite, and was an international collaboration between the US, the Netherlands and the UK. IRAS mapped nearly the entire sky at four wavelengths, including 60 microns (millionths of a meter) and 100 microns in the far-infrared. Since infrared detector technology was still relatively immature at the time of this path-breaking mission, the spatial resolution for the mid-IR images is rather modest. The IRAS detectors were rectangular in shape, and had relatively large fields of view (about 1.5 arcmin wide and 4.7 arcmin long at 60 microns, and 3 arcmin by 5 arcmin at 100 microns). The far-IR images depicted in the Museum resulted from high-resolution processing, in which sky coverage and sophisticated mathematical algorithms combine to yield effective resolutions of better than 1 arcmin. The odd elliptical shape of many mid-infrared emission peaks is a consequence of the underlying rectangular detectors used by IRAS.


Radio

The radio images are, for the most part, from the National Radio Astronomy Observatory's Very Large Array (VLA) in New Mexico. The VLA is an interferometer, consisting of 27 identical 25-meter radio telescopes, separated by kilometers. Most of the images are taken from the NRAO VLA Sky Survey (NVSS), a survey of the entire sky that is accessible with the VLA. The survey was made at a frequency of 1.4 GHz (giga-Hertz, or billions of cycles per second), corresponding to a wavelength of about 21 centimeters. The effective resolution is about 45 arcseconds. A handful of the images were taken as part of other research investigations at the VLA.


X-Ray

The X-ray data were taken by the Position Sensitive Proportional Counter (PSPC) instrument aboard the orbiting ROentgen SATellite (ROSAT). The ROSAT observatory was an international collaboration between Germany, the US and UK, and operated from 1990-1999. Most of the images in the Museum were taken in an energy bandpass of 0.1-2.4 keV, corresponding to a wavelength of about 10 nm. The images have an effective resolution of 25 arcseconds.


Ultraviolet - Astro 1

The ultraviolet (UV) data were obtained by the 38-centimeter Ultraviolet Imaging Telescope (UIT) , part of the ASTRO-1 Observatory flown by the Space Shuttle over an 8-day period in late 1990. The UIT telescope obtained images in two broad bandpasses: the far-UV (130-180 nm) and the near-UV (180-300 nm). The effective resolution of the Gallery images is 3 arcseconds. Note that UV data are available for only some of the objects in the Museum.