SOHO Scoops a Picture of Planets on Parade
5 May 2000
(Source: NASA Headquarters)
Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
Exclusive images from the Solar and Heliospheric Observatory (SOHO) spacecraft will show four planets marching together on the side of the sun opposite from Earth, near the climax of a line-up of planets that is fascinating amateur astronomers around the world this month. On May 15, Mercury, Venus, Jupiter and Saturn will all be in the field of view of the Large Angle and Spectrometric Coronagraph (LASCO) instrument on SOHO.
Skywatchers can view the show on the Internet at the sites referenced at the end of this release; presently, Saturn, Jupiter, and Mercury can be seen with SOHO. NASA TV will broadcast video of the planetary parade Friday, May 5, and updated versions will be broadcast Friday, May 12, and Monday, May 15.
Because the planets travel around the sun at different speeds, their position in the sky as seen from Earth changes. Rarely, some or all of the planets appear together in the same area of sky, a circumstance called planetary conjunction. In the past, people attributed special significance to celestial events, so such alignments have altered the course of history. The current conjunction presents a striking but benign spectacle, with Mercury, Venus, Mars, Jupiter and Saturn grouped most tightly on May 17.
As the planets neared the sun's direction in recent weeks, observers on the ground were frustrated by the glare of sunlight preventing them from seeing the planets. But what was hard for other skywatchers was ideal for SOHO. Using masks to blot out direct rays from the solar surface, the LASCO coronagraph watches for gaseous outbursts from the sun's atmosphere. It also sees stars beyond the sun and has discovered many unknown comets.
The widest field of view spans 15 degrees across the sky, which is just enough to accommodate the four planets on May 15. Venus will be heading into the picture while Mercury will be on its way out. Mars will be out of view on the left, being almost twice as far across the sky as Mercury. Jupiter and Saturn will be closer to the solar direction but the sun will already be leaving them behind.
The sun's direction in the sky, relative to the stars, keeps shifting to the left as the Earth and SOHO orbit around it. The appearance of the planets and the sun in roughly the same direction means that the Earth too is temporarily in line with the other planets, although on the opposite side of the sun.
The planets keep altering their relative positions because they orbit around the sun at different rates. Changes in their locations, especially of the massive Jupiter and Saturn, alter the position of the center of mass of the Solar System, so that sun itself wobbles. Such wobbles seen in other stars have enabled astronomers to detect alien planets.
SOHO is a project of international cooperation between the European Space Agency and NASA. The LASCO coronagraph was built and is operated by a multinational team led by the US Naval Research Laboratory.
Images are available on the Internet at:
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