Every once in a while, things align just right in the cosmos and makes it rather easy to write these articles. Last month Mars was in the headlines because of its closest approach to Earth in its orbit as well
Every once in a while, things align just right in the cosmos and makes it rather easy to write these articles. Last month Mars was in the headlines because of its closest approach to Earth in its orbit as well as being in opposition, making the planet the biggest and brightest in the night sky in the last two years. This month, Mars is again in our sights because of a possible encounter with an asteroid, prompting speculation that the near pass may have a chance of even hitting the Red Planet. The asteroid, called 2007 WD5, passes within 30,000 miles of Mars on Jan. 29 at 11:55 p.m. Hawai‘i Standard Time. Scientists put the odds at one in 75 that the 160-foot diameter rock will smash into the planet; however, in astronomical terms this is considered a near encounter due to uncertainties and unknown factors in the asteroid’s orbit.
If such an event were to occur, the blast is estimated to release around 3 megatons of energy as it plows into the Martian ground at 3.4 miles per second. This would be similar to the Tunguska event in 1908 where an object exploded above Earth in Siberia and demolished a forest area of 830 square miles. Earth avoided a huge impact crater from the Tunguska explosion because our thicker atmosphere caused the meteor to disintegrate before it actually reached the surface; however, Mars has a much thinner atmosphere and if 2007 WD5 enters its atmosphere, it will impact the ground and create a half-mile-wide crater and a huge plume of dust in the sky.
It would be incredibly interesting for scientists who have not seen another planetary impact since the 1994 Shoemaker-Levy comet collision with Jupiter. But the interest would be not just academic. There is a growing awareness from scientists to administrators of the possibility and implications of an Earth impact at some point in the future.
There are thousands of Near Earth Objects orbiting our sun-comets and asteroids left over from the formation of the solar system 4.6 billion years ago. To date more than 5,000 objects have been identified as Near Earth Objects, defined by how close they get to Earth at perihelion, the closest approach to the sun. A sub-group of Near Earth Objects are the Potentially Hazardous Asteroids, rocks greater than 500 feet in diameter approaching Earth at a distance of 4.6 million miles or less. To date there are 912 Potentially Hazardous Asteroids identified so far.
While 4.6 million miles between civilization and the fate of the dinosaurs seems like a comfortable distance, it really isn’t for astronomers. Earth doesn’t orbit the sun alone, and there are many factors that could influence and change the orbits of these objects. There are a few groups monitoring and searching the skies for Near Earth Objects, including one here in Hawai‘i. Pan-STARRS, the Panoramic Survey Telescope & Rapid Response System, is being developed at the University of Hawai‘i Institute for Astronomy and is already in prototype operation on Haleakala. When completed, four cameras, each with 1.4 billion pixels, will eventually scan the skies to track and detect potentially hazardous objects.
Because no one really knows how many objects out there have not yet been discovered, calculating the odds of the next major strike can only be done on a statistical basis. The estimated size for an object threatening life on a global scale is around 2 kilometers (1.2 miles) in diameter or larger. The object that ended the reign of the dinosaurs is thought to have been 15 kilometers. Obviously, asteroids or comets of that scale impact our planet in terms of millions of years, but there are many smaller but no less significant bodies that fall within the “major disaster” range.
Tracking and detecting these objects is a good idea, but what happens once we discover one that is barreling toward us? Currently, there is no officially sanctioned plan by the U.S. or the world to react to such a threat; however, there are a couple of private foundations starting grassroots efforts. Former Hawai‘i astronaut Ed Lu is part of one of those organizations, called the B612 Foundation, looking for support to develop a system to alter the path of the body. Other organizations, including NASA, are supporting more studies of Near Earth Objects, not just for defensive purposes but also for the vast resources that these rocks contain. In addition, the asteroid field could be used as “stepping stones” to human exploration to Mars and beyond.
First meteor
shower of year
The Quadrantid meteor shower peaked on Jan. 3. The Quadrantids is one of the two really “good” meteor showers this year, the next one with the best conditions comes in April. New information for 2008 will be posted online at www.bishopmuseum.org
The planets
Earth reaches perihelion on Jan. 2, its closest point to the sun in its orbit, at 1:50 p.m.
Mercury starts to become visible by the middle of January in the west shortly after sunset but never reaches much height above the horizon. You will have to have a clear view of the west to see this little planet at all during the second half of the month. The inner planet will have a visitor shortly — the Messenger spacecraft sent from NASA will approach its destination on Jan. 14 to execute the first of three fly-bys of Mercury before finally settling down in orbit (in 2011) to complete its mission of mapping the planet.
Venus is rising a bit later now, rising at 4:30 a.m. at the beginning of January. By the second week of the month, the brightest planet is joined by the largest planet, as Venus and Jupiter prepares for a rendezvous in February. Look for the pair in the east in the dawn sky throughout the month.
Mars spends the month high in the sky as darkness falls, between the horns of Taurus and the feet of Gemini. By the end of the month it won’t be as bright as it is at the start because Earth is quickly speeding away from the Red Planet in its orbit. Look for a waxing moon close to Mars on Jan. 19.
Jupiter, the giant planet, has now moved into the morning sky and may be spotted just before sunrise in the east by the second half of January. Because the inner planet Venus moves faster, it appears to move closer to Jupiter as the month closes, and by the last few days of the month the two brightest planets are a beautiful pair at dawn.
Saturn rises in the east a little after 10 p.m. in early January, then two hours earlier by the end of the month. The ringed planet is joined by a waning gibbous moon on Jan. 23 and 24 in the constellation Leo.
Moon phases
New moon: Jan. 8
First quarter: Jan. 15
Full moon: Jan. 22
Third quarter: Jan. 29
All dates are Hawai’i Standard time.
• Questions? Contact Carolyn Kaichi @ hokupaa@bishopmuseum.org or 847-8203.
