# Today In Science History – September 2 – Franz Xaver von Zach

September 2 marks the passing of Franz Xaver von Zach. Franz Xaver was a Hungarian astronomer who was the director of the Gotha Observatory when it first began operations. Xaver’s primary contribution to astronomy was organizing the search for the missing planet between Mars and Jupiter.

Astronomers as early as 1596 noticed a large gap between the Mars and Jupiter. Kepler assigned an undiscovered planet within that gap primarily because he felt God would not leave such a large gap in His Solar System. By the end of the 18th Century, there was an empirical mathematical relationship between the increasing radii of the planet’s orbits around the Sun known as the Titius-Bode law. This relationship started with a series of numbers generated by the planet’s number. Mercury was 1, Venus 2, Earth 3, etc. Mercury’s number started at zero and Venus was three. Each number after that was twice the previous number. This gives the series as:

0, 3, 6, 12, 24, 48, 96

The next step added 4 to each number in the series.

4, 7, 10, 16, 28, 52, 100

Then each number is divided by 10.

0.4, 0.7, 1.0, 1.6, 2.8, 5.2, 9.6

If you look at these numbers as Astronomical Units (AU) where 1 AU = orbit radius of Earth, you see the relationship.

Mercury’s orbit is very close to 0.4 AU from the Sun. Venus is very close to 0.7 AU. Earth is 1 AU by definition. Mars is 1.6 AU, but Jupiter is 5.2 AU and Saturn is 9.6. Astronomers felt the pattern worked so well, there really should be something floating around the Sun at 2.8 AU. For the most part, they thought the pattern was an interesting coincidence, but not many of them dedicated their research time to the search. In 1781, William Herschel discovered the planet Uranus outside the orbit of Saturn. If you doubled 96 and got 192. Add 4 to get 196 and divide by 10 to get 19.6. Turns out Uranus’ orbit is right near 19.6 AU. Suddenly the Titius-Bode law was attractive again.

Franz Xaver decided to invite European astronomers to the Gotha Observatory to scour the skies for the missing planet at 2.8 AU. 24 astronomers answered the call and were known collectively as the “Celestial Police”. Xaver centered their search along the ecliptic plane since all the other planets were also along this plane and reasoned the missing planet would follow the same rules. Each astronomer was assigned a 15° by 15° patch of the sky to chart all objects and note any changes from night to night that would suggest a planet. 24 astronomers, each searching 15° of the sky would cover all 360° of the sky. If there is a planet, it would be quickly found.

Unfortunately for the Celestial Police, Giuseppe Piazzi beat them to the discovery. Piazzi discovered Ceres which orbited the Sun near 2.8 AU. For a while, Ceres was labeled the missing planet, but its size was inconsistent with the mass needed to sit at that orbit. Soon, members of the Celestial Police began identifying other objects in that orbit. They discovered Pallas next, then Vesta and Juno. Perhaps the missing planet collided with some object from Jupiter’s orbit and shattered it.

Xaver’s Celestial Police never found a planet, but they did establish a new class of objects known today as asteroids.

Side note: The discovery of Neptune in 1846 would show the Titius-Bode law was just a mathematical curiosity. Neptune’s orbit is nearly 30% closer than the 38.8 AU prediction of Titius-Bode. It is curious to note, that if Neptune wasn’t there, Pluto’s orbit is very close to 38.8 AU.

### Notable Science Events for September 2

#### 2001 – Christiaan Barnard died.

Barnard was a South African cardiac surgeon who performed the first successful human to human heart transplant.

His patient, Louis Washkansky was suffering from diabetes and incurable heart disease. He received a heart from Denise Darvall, who had died the day before. Washkansky lived for another 18 days before succumbing to pneumonia.

#### 1992 – Barbara McClintock died.

McClintock was an American geneticist who discovered genes could move into different locations of the genome. She studied maize and tracked the genetic differences of maize kernel colors during controlled crossings.

She was awarded the 1983 Nobel Prize in Medicine for the discovery of these transposons.

#### 1877 – Frederick Soddy was born.

Soddy was an English chemist who was awarded the 1921 Nobel Prize in Chemistry for his work concerning the origin and nature of isotopes. He discovered isotopes are created by the transmutation of elements through radioactive decay. He showed that elements move two atomic numbers lower by alpha decay and one atomic number by beta decay.

#### 1854 – Paul Vieille was born.

Vieille was a French chemist who successfully created the first smokeless gunpowder. Nitrocellulose was an effective alternative to gunpowder in the form of gun cotton. The problem was gun cotton was a highly unstable material and a danger to everyone involved in its manufacture and use. Vieille discovered a method to suspend nitrocellulose as a colloid into a variety of solvents that could be pressed into a useful and stable form.

#### 1853 – Friedrich Wilhelm Ostwald was born.

Ostwald was a German chemist who was awarded the 1909 Nobel Prize for his work on chemical catalysts, chemical equilibria, and reaction rates. He is considered one of the pioneers of modern physical chemistry.

He is also known for the Ostwald process to mass produce nitric acid from ammonia.

#### 1836 – William Henry died.

Henry was an English chemist who formulated what would become known as Henry’s law. Henry’s law states that at a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. This law also applies to several dilute solutions in addition to gases.