Astronomy Question: Why isn’t Pluto a Planet Anymore?
Published October 20, 2011
Solar System Diagram. Image Credit: Wikimedia
Michelle asks,
Dear Astronomer, Why isn’t Pluto a planet anymore?
Great question Michelle, one that still sparks debate over five years after the controversial decision by the International Astronomical Union (IAU). For the benefit of those who don’t know the full backstory, this will be a pretty in-depth explanation.
Discovered by Clyde Tombaugh in 1930, Pluto is certainly an interesting case. During the early 1900′s there was speculation of another planet lurking past Neptune. After many years of studying Pluto, the determination was made that Pluto was not massive enough to be the cause of perturbations in the orbits of Neptune and Uranus. The determination was also supported by revised estimates of Neptune’s mass.
Pluto, Charon, Nix, Hydra and newly discovered "P4".
Image Credit: NASA/HST
As astronomers discovered more about Pluto, the less of a “fit” with the rest of the solar system became clear. Even when I was in grade school (in the late 70′s/early 80′s), textbooks and even some planetarium presenters described Pluto as more of a “giant comet”, than a planet.
Further adding to the confusion is Pluto’s moon ( for lack of a better term ) Charon. Technically speaking, Pluto and Charon are a “binary” system – the only one known to exist in our solar system. Additionally, three more objects orbiting Pluto have been discovered. Nix, Hydra and an unnamed object now designated “P4″. Given these objects, one could describe the Pluto system as a loosely bound “cloud” of icy objects.
So how does all this fit in with “planetary status” ?
Consider that most people like to organize things in similar groups. We don’t put plates in the silverware drawer, nor do we put shoes in our refrigerator. A quick glance at our solar system shows three readily apparent classes of planets; Terrestrial planets ( Mercury, Venus, Earth, Mars), Gas giants (Jupiter, Saturn), and “Ice” giants ( Uranus and Neptune ). Out past Neptune (out to a distance of almost a light year from our Sun!) there are many icy/rocky objects, few of which have been studied in great detail.
Eris and Dysnomia.
Image Credit: NASA/HST
While studying the region past Neptune, astronomer Mike Brown and his team discovered an object that at its furthest point orbits at nearly twice the distance from our Sun as Pluto. The object, first dubbed 2003UB313 (now known as Eris) was estimated to be nearly the same diameter as Pluto and additional studies of this object and its moon revealed a mass roughly 25% more than Pluto’s.
Brown’s discovery raised some interesting questions. If Eris, being much further from the sun was the same diameter and had more mass than Pluto, had a new planet been discovered? If more objects like Eris were to be discovered past Pluto’s orbit, would they also be planets?
A controversial decision by the International Astronomical Union in 1996 set out to provide an “official” set of criteria for planetary status. The IAU states an object is a planet if it:
In order to classify objects like Pluto and Eris (as well as Makemake, Ceres, and Haumea) which meet the first two criteria, the IAU adopted the term “dwarf planet”. Based on studies of the outer solar system, estimates of how many dwarf planets exist range between a few dozen and a few hundred.
On August 24th 2006, the IAU’s proposal passed a vote, and thus, Pluto no longer was considered a full-fledged planet, but instead the first of the dwarf planets. Many people to this day criticize the vote and the decision, however science is not dictated by popular opinion. With the discovery of many additional objects past Neptune’s orbit that share similar characteristics with Pluto, the IAU’s decision appears to make sense, for the time being.
Chinese Researchers Unveil Plan to Divert Asteroid Apophis
Published September 28, 2011
Diagram displaying orbital parameters
Asteroid Apophis (Formal designation 99942 Apophis) will be making an extremely close pass to Earth in 2029. The trajectory of Apophis is such that the asteroid will pass through a “keyhole” area of space near Earth, which will cause the asteroid to make a second pass near Earth in 2036.
While the orbital trajectories of the 2029 Apophis encounter with Earth are well known, the details of the 2036 pass are a bit uncertain. Given a window of only seven years between the 2029 and 2036 passes, scientists and engineers will have to work quickly if the chance of a collision between Apophis and Earth is relatively high in 2036.
A recent scientific paper authored by Shengping Gong (Tsinghua University, Beijing) outlines a possible plan of action to divert Apophis.
Given that orbital keyholes are only a few hundred meters wide, the team believes a very small deflection relatively soon would cause Apophis to avoid the keyhole and a second close encounter with Earth.
Aside from sending Bruce Willis and Ben Affleck on a Space Shuttle to blow up Apophis, there are numerous methods that could be used to deflect an incoming asteroid. Some methods border on science-fiction and others are quite ingenious.
Scientists and engineers have suggested placing probes in orbit around Apophis to “steal” its momentum, others have suggested “painting” part of an incoming asteroid a different color to take advantage of solar radiation, and some have suggested the equivalent of a tugboat in space to tow the asteroid. One other method, which is the method suggested by Gong and team, is to use a solar sail to place a small spacecraft on a collision course with Apophis. If the impact velocity is around 90km/s there should be enough energy to move Apophis enough to alter its trajectory.
The close approach of 99942 Apophis to the Earth and Moon on Friday, April 13, 2029.
Image Credit: Wikimedia
No single method to divert an asteroid is perfect, as each of the methods have differing advantages and drawbacks. Based on the calculations presented in Gong’s paper, the main advantage of their proposed plan is that a 10 kg sail colliding with Apophis in 2028 ( a year before the 2029 encounter), would deflect it enough to prevent a second encounter between Apophis and Earth in 2036.
One of the major drawbacks to Gong’s plan is that much like a hot-air balloon or a sailing ship, using a solar sail to place a spacecraft on a collision course with Apophis is fairly risky. The solar wind has variations that could send a craft off-course. One other issue is that a very large sail would be require, which could be easily damaged, or could malfunction.
Another possible issue with Gong’s plan is that the physical properties of Apophis are relatively unknown. Sending an object on a collision course with the asteroid could have consequences if the asteroid breaks apart instead of having its trajectory slightly adjusted. There are also questions of whether or not tweaking the trajectory of Apophis could still end up causing a collision with Earth.
In short, there are many techniques that could be used, if the need arises to alter the trajectory of an incoming asteroid. Each technique has benefits and drawbacks which need to be weighed against what, if any, benefits there would be to altering the trajectory of an incoming asteroid.
If you’d like to learn more about Apophis, visit NASA’s Near Earth Object Program at: http://neo.jpl.nasa.gov/apophis/
You can read the full paper at: http://arxiv.org/ftp/arxiv/papers/1108/1108.3183.pdf
Source:Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection
Apollo 18 Movie: September 2nd 2011
Published August 15, 2011
Dimension Films is releasing a new horror/thriller movie next month based on a fictional “Secret” Apollo mission. The trailer for the film attempts to re-create the look and feel of Apollo-era grainy footage. I won’t give away too many details, so as not to spoil anything in the trailer. In actuality, the last Apollo mission was Apollo 17 (December 1972). The movie is based on the premise that Apollo 18 was a secret mission, funded by the U.S Department of Defense.
The film has been in development hell for some time, but Dimension Films is releasing Apollo 18 on September 2nd 2011. Recently a number of promotional videos for the film have popped up all over the Internet, which claim to include actual footage from the Apollo 18 mission, stating that although NASA denies the authenticity, said footage is the real reason we’ve never gone back to the Moon.
While a lot of people tend to shun “indie” Films, I will say, as a side note that some “indie” sci-fi films that I’ve watched were quite enjoyable despite less than favorable initial buzz. “Moon” starring Sam Rockwell and Kevin Spacey, along with District 9 are a couple of movies that come to mind.
In short, Apollo 18 seems like a good movie to catch on a Friday night. Just make sure to unplug your brain and engage your “suspension of disbelief” for a few hours. You can look forward to a full movie review from me in a couple of weeks.
If you want to learn more about the film, visit: http://www.apollo18movie.net, or http://www.facebook.com/apollo18movie
Below is one of several trailers for Apollo 18 (Warning: Trailer includes some intense scenes, but no gore or foul language (PG):
Comet Elenin: Facts and Fiction
Published August 8, 2011Despite what you may see in movies and television, comets usually pose little to no threat to Earth. Recently, Comet Elenin has made the rounds on some “news” sites. In many cases, the sites claim that Elenin will be making a dangerously close pass to Earth, when in fact Elenin will be about 22 million miles from Earth.
Trajectory of comet Elenin.
Image credit: NASA/JPL-Caltech
At it’s closest, Elenin will be slightly closer to us then Venus, comparatively speaking (22 million miles for Elenin and roughly 25 million miles for Venus). Current predictions predict that comet Elenin will be at it’s closest to Earth around Oct. 16, 2011.
Discovered in December of 2010 by Leonid Elenin, the comet is also known by it’s “proper” name of C/2010 X1. Elenin (the astronomer) hails from Lyubertsy, Russia, and made his discovery using equipment at an observatory in New Mexico.
Coment Elenin was about 400 million miles away from Earth at the time of its discovery. Much like any other comet, Elenin has been steadily moving closer to Earth as its trajectory takes it closer to our sun.
Below are a few questions and answers about Comet Elenin. The answers have been collected from a list of responses from NASA scientists who are a part of NASA’s Near-Earth Object Program Office at JPL.
NASA Statement regarding “Alien” Fossils
Published March 7, 2011NASA has released a statement regarding the paper submitted to the Journal of Cosmology by Richard Hoover, Astrobiologist at Marshall Space Flight Center:
“NASA is a scientific and technical agency committed to a culture of openness with the media and public. While we value the free exchange of ideas, data, and information as part of scientific and technical inquiry, NASA cannot stand behind or support a scientific claim unless it has been peer-reviewed or thoroughly examined by other qualified experts. This paper was submitted in 2007 to the International Journal of Astrobiology. However, the peer review process was not completed for that submission. NASA also was unaware of the recent submission of the paper to the Journal of Cosmology or of the paper’s subsequent publication. Additional questions should be directed to the author of the paper.” – Dr. Paul Hertz, chief scientist of NASA’s Science Mission Directorate in Washington
The paper has received a fair amount of attention the past few days, and rightly so. As Marcello Truzzi and Carl Sagan have said: “Extraordinary claims require extraordinary proof”. Hoover may be correct in his theories about what has been found in the meteorites he has analyzed, but as true scientists and skeptics, we must insist that Hoover’s claims be reviewed by others in the scientific community. There are also some questions as to whether or not Hoover actually has a Ph.D.
Many Astrobiologists have since spoken out regarding Hoover’s announcement and given the methodology used, and the choice of journal to publish to (Journal of Cosmology) has had its integrity questions on occasion. Given the controversy and scientific backlash against NASA surrounding the last “Alien” life announcement , it is understandable that NASA has been quick to make a statement regarding this latest announcement.
The paper submitted can be read at: http://journalofcosmology.com/Life100.html – however, I’ll warn that it is by no means a “light” read.
Source(s):NASA , spaceref.com , Journal Of Cosmology
Can WISE Find the Hypothetical ‘Tyche’?
Published February 18, 2011In November 2010, the scientific journal Icarus published a paper by astrophysicists John Matese and Daniel Whitmire, who proposed the existence of a binary companion to our sun, larger than Jupiter, in the long-hypothesized “Oort cloud” — a faraway repository of small icy bodies at the edge of our solar system. The researchers use the name “Tyche” for the hypothetical planet. Their paper argues that evidence for the planet would have been recorded by the Wide-field Infrared Survey Explorer (WISE).
This colorful picture is a mosaic of the Lagoon nebula taken by NASA’s Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/UCLA
WISE is a NASA mission, launched in December 2009, which scanned the entire celestial sky at four infrared wavelengths about 1.5 times. It captured more than 2.7 million images of objects in space, ranging from faraway galaxies to asteroids and comets relatively close to Earth. Recently, WISE completed an extended mission, allowing it to finish a complete scan of the asteroid belt, and two complete scans of the more distant universe, in two infrared bands. So far, the mission’s discoveries of previously unknown objects include an ultra-cold star or brown dwarf, 20 comets, 134 near-Earth objects (NEOs), and more than 33,000 asteroids in the main belt between Mars and Jupiter.
Following its successful survey, WISE was put into hibernation in February 2011. Analysis of WISE data continues. A preliminary public release of the first 14 weeks of data is planned for April 2011, and the final release of the full survey is planned for March 2012.
Frequently Asked Questions
Q: When could data from WISE confirm or rule out the existence of the hypothesized planet Tyche?
A: It is too early to know whether WISE data confirms or rules out a large object in the Oort cloud. Analysis over the next couple of years will be needed to determine if WISE has actually detected such a world or not. The first 14 weeks of data, being released in April 2011, are unlikely to be sufficient. The full survey, scheduled for release in March 2012, should provide greater insight. Once the WISE data are fully processed, released and analyzed, the Tyche hypothesis that Matese and Whitmire propose will be tested.
