A quick update on things going on in space. In this e-mail:
- Thoughts on Pluto
- Dark Matter Still Dark
- Lunar Impact
- Max books donation update
1. Thoughts on Pluto.
Many of you have been asking me what I think of the new definitions that demote Pluto and create a new category of “dwarf planets” that includes Pluto, the object still nicknamed Xena, the asteroid Ceres, and perhaps dozens of other objects to be named later. My short answer: Scientifically, it’s long been clear that Pluto is in a different category than the other 8 planets. Semantically, whether that means it’s a regular planet, one of a whole new group of regular planets, a dwarf planet that is not a regular planet, a “large Kuiper belt comet” (my personal favorite for Pluto), or anything else is just, well, semantics. For my longer answer, please see my article posted at http://www.space.com/searchforlife/seti_pluto_060831.html.
Questions for class:
- How is Pluto different from the 8 now-official planets? (Answer: It differs in orbit (more elongated ellipse and more tilted to ecliptic), it is much lower in mass, and it differs in composition (ice/rock, unlike either the rocky terrestrial planets or gaseous jovian planets).)
- What is “Xena,” and in what way did it spur the current debate? (Answer: See my posting at http://www.space.com/searchforlife/seti_pluto_060831.html.)
- What do YOU think of the new definitions? Defend your opinions.
2. Dark Matter Still Dark.
Most of the matter in the universe seems to be “dark” — by which astronomers mean that we can detect its gravitational influence but cannot see any light coming from the matter. The leading hypothesis holds that most of this dark matter is made of subatomic particles that do not emit or absorb light. However, some physicists have proposed that dark matter doesn’t really exist, and instead the observed effects tell us that our current theory of gravity (Einstein’s general theory of relativity) is not quite correct. A very cool new set of results from Hubble — posted at http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/39/ — greatly strengthens the case for the existence of dark matter, and appears to rule out the alternate theories of gravity that have been proposed. A triumph for Einstein, but the dark matter is still quite dark both in visibility and in the fact that we still have little idea of exactly what it is.
For more discussion, please see Mystery #2 in my book On the Cosmic Horizon or Chapter 22 in The Cosmic Perspective.
Questions for class:
- Read the news release on the Hubble web site. How were the data collected? What does the image show? (Answer: data were based on measurements of gravitational lensing caused by the galaxy cluster. Note that the image shows the inferred dark matter distribution based on these measurements; it does NOT show any type of light emission.)
3. Lunar Impact
The European SMART-1 spacecraft will execute a planned crash into the Moon tomorrow. Read about it and find out how to observe it at http://science.nasa.gov/headlines/y2006/30aug_smart1.htm.
4. Max books donation update.
This fall, I am donating another 5,000 copies of Max Goes to Mars. About 3,200 copies have been claimed so far, and will be going to, among others, the entire states of Mississippi, Michigan, and Rhode Island, a large part of Kentucky, the Atlanta metro area, and Indian reservations in New Mexico and Arizona. I’m still looking for districts to receive the remaining 1,800 copies. So if you know some that might be interested, FIRST read my program guidelines at http://www.jeffreybennett.com/donation.html, and then contact me. Thanks.