Pale Blue Dot Revisited
For the 30th anniversary of one of the most iconic images taken by NASA's Voyager mission, a new version of the image known as "the Pale Blue Dot." Planet Earth is visible as a bright speck within the sunbeam just right of center and appears softly blue, as in the original version published in 1990 (see PIA00452). This updated version uses modern image-processing software and techniques to revisit the well-known Voyager view while attempting to respect the original data and intent of those who planned the images. In 1990, the Voyager project planned to shut off the Voyager 1 spacecraft's imaging cameras to conserve power and because the probe, along with its sibling Voyager 2, would not fly close enough to any other objects to take pictures. Before the shutdown, the mission commanded the probe to take a series of 60 images designed to produce what they termed the "Family Portrait of the Solar System." Executed on Valentine's Day 1990, this sequence returned images for making color views of six of the solar system's planets and also imaged the Sun in monochrome. The popular name of this view is traced to the title of the 1994 book by Voyager imaging scientist Carl Sagan, who originated the idea of using Voyager's cameras to image the distant Earth and played a critical role in enabling the family portrait images to be taken. The image of Earth was originally published by NASA in 1990. It is republished here to commemorate the 30th anniversary of the Family Portrait of the Solar System (see PIA00451) and the Pale Blue Dot image in particular. The planet occupies less than a single pixel in the image and thus is not fully resolved. (The actual width of the planet on the sky was less than one pixel in Voyager's camera.) By contrast, Jupiter and Saturn were large enough to fill a full pixel in their family portrait images. The direction of the Sun is toward the bottom of the view (where the image is brightest). Rays of sunlight scattered within the camera optics stretch across the scene. One of those light rays happens to have intersected dramatically with Earth. From Voyager 1's vantage point — a distance of approximately 3.8 billion miles (6 billion kilometers) — Earth was separated from the Sun by only a few degrees. The close proximity of the inner planets to the Sun was a key factor preventing these images from being taken earlier in the mission, as our star was still close and bright enough to damage the cameras with its blinding glare. The view is a color composite created by combining images taken using green, blue and violet spectral filters by the Voyager 1 Narrow-Angle Camera. They were taken at 4:48 GMT on Feb. 14, 1990, just 34 minutes before Voyager 1 powered off its cameras forever. Like the original version, this is technically a "false-color" view, as the color-filter images used were mapped to red, green and blue, respectively. The brightness of each color channel was balanced relative to the others, which is likely why the scene appears brighter but less grainy than the original. In addition, the color was balanced so that the main sunbeam (which overlays Earth) appears white, like the white light of the Sun. At its original resolution, the newly processed color image is 666 by 659 pixels in size; this is Figure A. The main image is an enlarged version. The image was processed by JPL engineer and image processing enthusiast Kevin M. Gill with input from two of the image's original planners, Candy Hansen and William Kosmann. https://photojournal.jpl.nasa.gov/catalog/PIA23645
Supernova SN1987A in the Large Magellanic Cloud
Glittering stars and wisps of gas create a breathtaking backdrop for the self-destruction of a massive star, called supernova 1987A, in the Large Magellanic Cloud, a nearby galaxy. Astronomers in the Southern hemisphere witnessed the brilliant explosion of this star on Feb. 23, 1987. Shown in this NASA Hubble Space Telescope image, the supernova remnant, surrounded by inner and outer rings of material, is set in a forest of ethereal, diffuse clouds of gas. This three-color image is composed of several pictures of the supernova and its neighboring region taken with the Wide Field and Planetary Camera 2 in Sept. 1994, Feb. 1996 and July 1997. The many bright blue stars nearby the supernova are massive stars, each more than six times heftier than our Sun. They are members of the same generation of stars as the star that went supernova about 12 million years ago. The presence of bright gas clouds is another sign of the youth of this region, which still appears to be a fertile breeding ground for new stars. In a few years the supernova's fast moving material will sweep the inner ring with full force, heating and exciting its gas, and will produce a new series of cosmic fireworks that will offer a striking view for more than a decade.
A Grazing Encounter Between Two Spiral Galaxies
The larger and more massive galaxy is cataloged as NGC 2207 (on the left in the Hubble Heritage image), and the smaller one on the right is IC 2163. Strong tidal forces from NGC 2207 have distorted the shape of IC 2163, flinging out stars and gas into long streamers stretching out a hundred thousand light-years toward the right-hand edge of the image. Computer simulations, carried out by a team led by Bruce and Debra Elmegreen, demonstrate the leisurely timescale over which galactic collisions occur. In addition to the Hubble images, measurements made with the National Science Foundation's Very Large Array Radio Telescope in New Mexico reveal the motions of the galaxies and aid the reconstruction of the collision. The calculations indicate that IC 2163 is swinging past NGC 2207 in a counterclockwise direction, having made its closest approach 40 million years ago. However, IC 2163 does not have sufficient energy to escape from the gravitational pull of NGC 2207, and is destined to be pulled back and swing past the larger galaxy again in the future. The high resolution of the Hubble telescope image reveals dust lanes in the spiral arms of NGC 2207, clearly silhouetted against IC 2163, which is in the background. Hubble also reveals a series of parallel dust filaments extending like fine brush strokes along the tidally stretched material on the right-hand side. The large concentrations of gas and dust in both galaxies may well erupt into regions of active star formation in the near future. Trapped in their mutual orbit around each other, these two galaxies will continue to distort and disrupt each other. Eventually, billions of years from now, they will merge into a single, more massive galaxy. It is believed that many present-day galaxies, including the Milky Way, were assembled from a similar process of coalescence of smaller galaxies occurring over billions of years. This image was created from 3 separate pointings of Hubble. The Wide Field Planetary Camera 2 data sets were obtained by Debra Meloy Elmegreen (Vassar College), Bruce G. Elmegreen (IBM Research Division), Michele Kaufman (Ohio State U.), Elias Brinks (Universidad de Guanajuato, Mexico), Curt Struck (Iowa State University), Magnus Thomasson (Onsala Space Obs., Sweden), Maria Sundin (Goteborg University, Sweden), and Mario Klaric (Columbia, South Carolina).