The Celestial Sphere

by Matthew Johnson

The James Webb Space Telescope, weighing more than seven tons, is scheduled to be launched in late September or October by a European Ariane 5 rocket from the European spaceport located near Kourou, French Guiana, very close to the earth’s equator.

The most important aspect in the telescope’s name is the word “space.” Like the Hubble Space Telescope, the James Webb Space Telescope will reside in space. Where the Hubble maintained an orbit 340 miles above the earth where it could be serviced by shuttles, the Webb will be lifted some 10,000 kilometers (6,200 miles) above the earth— in just 30 minutes—by the Ariane 5 rocket. Then, once released from the rocket, it will spend another month traveling on its own to its final orbit 1.5 million kilometers (930,000 miles) from Earth. As the Webb travels to its final orbit, it will unfurl five sheets of Kapton foil, each the size of a tennis court but thinner than a sheet of paper. These silvery winglike sheets will function as umbrellas, protecting the telescope by shielding it from the reflective heat of the earth, moon and sun. The telescope’s systems work best in the coolest temperatures possible and, with these shields and the orbital distance from Earth and its moon, the telescope will be nearly as dark and cold as space itself. This harsh environment ensures that faint and distant signals from the ancient universe, unavailable to conventional Earth-based scopes, will be picked up by the James Webb Space telescope.

The project is a collaboration between NASA, the European Space Agency and the Canadian Space Agency. Thousands of scientists, engineers and technicians contributed to Webb’s completion. More than 250 companies, agencies and universities participated, including 142 from the United States and more than 100 from Europe and Canada. The Space Telescope Science Institute in Baltimore, Maryland will be operating the Webb telescope, as it did for the Hubble.

The Webb’s most important attribute is its 21-foot-wide (6.5-meter-wide) primary mirror. A reflecting telescope’s primary mirror determines how much light it can collect, and thus how deeply it can see into the universe. Webb’s mirror is nearly three times wider than Hubble’s primary mirror. Webb’s mirror is actually composed of 18 separate hexagonal-shaped segments made of beryllium, which will unfold after launch. Each of the telescope’s mirror segments is covered in a thin layer of gold. This gold covering optimizes the mirror segments for reflecting infrared light, which is the primary wavelength of light this telescope will observe.

The Webb will be the largest, most powerful telescope ever built. Thousands of astronomers worldwide will use it for a wide range of research projects, complementing and extending the discoveries of the Hubble Space Telescope.

Once above Earth’s obscuring atmosphere, the Webb Space Telescope is expected to provide unobstructed views of the near and distant cosmos. Since light has a finite speed (186,000 miles per second, or 300,000 kilometers per second), the new space telescope will also provide insights into our universe’s past: from the first light given off after the Big Bang, to the formation and evolution of galaxies, to our own and other planetary systems. The Webb Space Telescope will be used for the study of every phase in the history of our universe.

Planets:

The September, or autumnal, equinox will arrive on September 22nd at exactly 3:21 p.m. The autumnal equinox marks the end of summer and the beginning of fall. The term equinox is derived from the Latin aequinoctium—from aequi, equal, and nocti, night. On both the spring (vernal) equinox and the fall (autumnal) equinox, the earth experiences twelve hours of daylight and twelve house of night. On both equinoxes the sun at noon is directly over the equator at 0 degrees latitude, which is between the Tropic of Cancer at 23.44 degrees north and the Tropic of Capricorn at 23.44 degrees to the south. 

At dusk on the evening of September 1st, look for brilliant Venus to the upper left of planet Mercury, which will be very low on the horizon. One will need an unobstructed southwestern vantage point in which to view the elusive Mercury. On September 8th, Mercury can be located along the southwestern horizon just underneath the thin crescent moon. The evenings of September 9th and 10th will offer the most interesting vistas of the month. The moon will stand to the right of Venus on the 9th; then these two will form part of a lineup the next night. On September 10th, observe the horizon for the following apparition: looking from the lowest right to the highest left, one will first view Mercury, then the brilliant blue star of Spica in constellation Virgo, then Venus and finally the crescent moon. On the 16th, the moon will be below Saturn and on the 17th it will be below Jupiter, the largest planet in the solar system. As mentioned in last month’s Celestial Sphere, the planets Saturn and Jupiter are visible all month long in September.

Moon phases:

Sept. 6: New moon (no visible Moon). The best time of the month to observe faint objects such as distant galaxies and star clusters, as there is no moonlight to interfere.  

Sept. 13: First quarter (right half of the moon illuminated).

Sept. 20: Full moon (Harvest Moon).

Sept. 28: Last quarter (left half of the moon illuminated).

Native American tribes gave names to each of the full moons to keep track of the passing year. The names are associated with the entire month until the next full moon occurs. To the Abenaki of Maine, the September full moon is the Corn Maker Moon. To the Algonquin northeast of the Great Lakes, it is “the middle between harvest and eating Moon” and to the Hopi of Arizona it is the Moon of the Full Harvest.