Jul 01

July 2007

What’s Up in the Sky July, 2007
By Peter Burkey

According to Prof. Gareth Wynn-Williams of the University of Hawaii, the history of astronomy can be viewed as having four ages, the first being Naked Eye which went from zero to Galileo. From 1600 to 1880 was the age of the Simple Telescope, the kind you had to look through and then sketch what you saw. The age of Spectroscopy and Photography came next, lasting until 1940 after which technological breakthroughs and new telescopes, including many in orbit, ushered in the age of the entire electromagnetic spectrum. Astronomers may no longer look through their telescopes, but the telescopes are capable of seeing much more than just visible light.

Electromagnetic radiation includes such things as infrared (heat) radiation, X-rays, gamma rays and radio waves, the distinguishing characteristic being the wavelength. So the difference between visible light and X-rays is the same as the difference between middle C and high C on a piano. Up until the 1940’s astronomers were like concertgoers who could only hear the notes E and F. Now we can hear the whole symphony and radio waves are the bass notes. Their wavelengths are very long so the telescopes have to be very large.

I recently had the privilege of taking a short course through the Chautauqua Institute taught by Dr. Wynn-Williams and held at the National Radio Astronomy Observatory in Green Bank WV. The course was interesting and very informative, but the highlight was that we were able to tour the world’s largest movable radio telescope – simply named the Green Bank Telescope or GBT. Because the telescope was down for repairs, we were able to go all the way to the top, visiting the receiver room and control room on the way.

The following day some of us used a 40 foot dish to observe the galaxy M87, a strong source of radio emissions due to a black hole at its core whose mass appears to be 3 billion suns.

Looking through your telescope is still fun, but by combining observations in many wavelengths we are able to see even more of what’s up in the sky.

This month in history:
July 1: Mt Wilson observatory receives 100 in. mirror – 1917
July 4: Supernova, whose remnant is known as the Crab Nebula, is witnessed – 1054 Mars Pathfinder lands on Mars – 1997
Deep impact collides with comet – 2005
July 6: Newton’s book, Principia is published – 1687
July 20: Humans walk on Moon for the first time – 1969 Viking 1 lands on Mars – 1976
July 30: Apollo 15 fourth mission to land on Moon – 1971

Here are this month’s viewing highlights:
Planets this month: Venus now getting lower in the west at dusk. Use binoculars or a telescope to view crescent. Look at 10:00 p.m. each night to see separation between Saturn and Venus increase. Jupiter shines brightly in the southern sky.

July 1-2: Venus – Saturn form close pair.
July 7: Last-quarter Moon
July 14: New Moon.
July 16: Spectacular gathering of Moon, Venus, Saturn, Regulus.
July 22: First quarter Moon.
July 29: Full Moon.

Peter at NRAO

Green Bank Telescope