1. Astronomy Picture of the Day (2007 Oct. 29)
A Tale of Comet Holmes
Explanation: What's happened to Comet Holmes? A normally docile comet discovered over 100 years ago, Comet 17P/Holmes suddenly became nearly one million times brighter last week, possibly over just a few hours. In astronomical terms, the comet brightened from magnitude 17, only visible through a good telescope, to magnitude 3, becoming visible with the unaided eye. Comet Holmes had already passed its closest to the Sun in 2007 May outside the orbit of Mars and was heading back out near Jupiter's orbit when the outburst occurred. The comet's sudden brightening is likely due to some sort of sunlight-reflecting outgassing event, possibly related to ice melting over a gas-filled cavern, or possibly even a partial breakup of the comet's nucleus. Pictured above through a small telescope last Thursday, Comet Holmes appeared as a fuzzy yellow spot, significantly larger in angular size than Earth-atmosphere blurred distant stars. Although Comet Holmes' orbit will place it in northern hemisphere skies for the next two years, whether it will best be viewed through a telescope or sunglasses remains unknown.
Astronomy Picture of the Day (2007 Oct. 29)
Erupting Comet Holmes

2. Astronomy Picture of the Day (2007 Nov. 21)
Explanation: The spherical coma of Comet Holmes has swollen to a diameter of over 1.4 million kilometers, making the tenuous, dusty cloud even bigger than the Sun. Scattering sunlight, all that dust and gas came from the comet's remarkably active nucleus, whose diameter before the late October outburst was estimated to be a mere 3.4 kilometers. In this sharp image, recorded on November 14 with the Canada-France-Hawaii Telescope, stars are easily visible right through the outer coma, while the nucleus is buried inside the condensed, bright region. The bright region of the coma seems offset from the center, consistent with the idea that a large fragment drifted away from the nucleus and disintegrated, producing the comet's spectacular outburst. Of course, more recent images of Holmes also show the bright star Mirfak (Alpha Persei) shining through as the comet sweeps slowly through the constellation Perseus.
Expansive Comet Holmes (breakup?)

3. Credit: Ishak Benbabaste
Explanation: The spherical coma of Comet Holmes has swollen to a diameter of over 1.4 million kilometers, making the tenuous, dusty cloud even bigger than the Sun. Scattering sunlight, all that dust and gas came from the comet's remarkably active nucleus, whose diameter before the late October outburst was estimated to be a mere 3.4 kilometers. In this sharp image, recorded on November 14 with the Canada-France-Hawaii Telescope, stars are easily visible right through the outer coma, while the nucleus is buried inside the condensed, bright region. The bright region of the coma seems offset from the center, consistent with the idea that a large fragment drifted away from the nucleus and disintegrated, producing the comet's spectacular outburst. Of course, more recent images of Holmes also show the bright star Mirfak (Alpha Persei) shining through as the comet sweeps slowly through the constellation Perseus.
Credit: Ishak Benbabaste

4. Advanced Question Chap. 14, Q7 in P372
Explain the statement “Methane” is to Uranus’s atmosphere as water is to Earth’s atmosphere?

5. Advanced Question Chap. 14, Q7 in P372
Answer:
Methane makes up cloud in Uranus’s atmosphere, and water makes up cloud in Earth’s atmosphere
In the atmsophere, water could be gas and solid at the temperature of the Earth, while methane could be gas and solid at the temperature of the Uranus.

6. Advanced Question Chap. 14, Q43 in P373
The New Horizons spacecraft will swing by Jupiter to get a boost from that planet’s gravity, enabling it to reach Pluto relatively quickly. To see what would happen if this technique were not used, consider a spacecraft trajectory that is an elliptical orbit around the Sun. The perihelion of this orbit is at 1 AU from the Sun (at the Earth) and the aphelian is at 30 AU (at Pluto’s position). Calculate how long it would take a spacecraft in this orbit to make the one-way trip from Earth to Pluto. Based on the information in section 14-10, how much time is saved by making a swling by Jupiter instead?

7. Advanced Question Chap. 14, Q43 in P373
Answer:
If in the elliptical orbit with perihelion of 1 AU and aphelion of 30 AU,
semimajor axis a = (30+1)/2=15.5 AU
Using Kepler’s law P2=a3
P=(a)3/2=(15.5)3/2= 61 years.
The travel time is half of this, ir 30.5 years.
Using Jovian planet’s grvity assit, New Horizon travel time is about 9 years.
More than 21 years will be saved !!!