(1) NEAR-EARTH ASTEROID (NEA) 2002 NT7 A small NEA called 2002 NT7 currently under observation has a remote possibility of hitting the Earth in 2019. The possibility will most likely be resolved within the next few days as new observations come in. It is reported here as an example of the sort of detective work associated with some of the newly discovered NEAs. (Assuming that you see nothing more posted here, you can assume that subsequent observations showed this object not to be a problem). Asteroid 2002 NT7, a relatively large (H=16) Apollo asteroid with a still rather poorly determined orbit, has been on the Risk Pages of both NEODyS and JPL since July 18. The asteroid is easily observable; in fact it is observed practically every night, and its visibility will remain very good for the coming two months. As new observations come in, the situation will evolve in the next days and, as usual, either the probability associated with this object will go up somewhat, or, more probably, it will disappear. The probability of impact is so small that this asteroid remains at a risk level on the Torino scale of 0 meaning that the chances of impact from another unknown NEA of the same size or larger is greater than the chances of being hit by 2002 NT7. However, the impact probablity is not zero, and additional observations are needed to ensure that this object will not hit the Earth in 17 years.
(2) SKY & TELESCOPE: NEXT MONTH'S FLYBY OF 2002 NY40 Roger W. Sinnott Senior Editor, Sky & Telescope In mid-August, a newly discovered asteroid will pass close enough to Earth that it should be easy to spot in small telescopes and even binoculars. This object was first detected on July 14th by astronomers using the LINEAR 1-meter survey telescope in New Mexico, and it has now been designated 2002 NY40 by the Minor Planet Center in Cambridge, Massachusetts. According to calculations by the center's associate director, Gareth V. Williams, it is traveling in a low-inclination, Apollo-type orbit with a period of 3.03 years. Its August 18th flyby should bring it to within 530,000 kilometers (330,000 miles) of Earth, which is just outside the Moon's distance. There are several key differences between this encounter and that of 2002 MN, which made news a few weeks ago. That object came well inside our own Moon's orbit and was not detected until several days after the fact. The new asteroid was found on its way in toward the Sun, a full month before its own flyby. But 2002 NY40 is about 10 times larger than 2002 MN; the best current estimates make it about half a kilometer (a third of a mile) across. Still quite faint at magnitude 18 in the constellation Aquarius, 2002 NY40 is making a very tight loop around the star Beta Aquarii. During the next few weeks it will brighten tremendously and yet remain almost motionless in the sky -- the eerie signature of an asteroid hurtling right toward the Earth! Then it veers off to the northwest as it goes by, racing past the double star Albireo in Cygnus for observers in the Western Hemisphere on the night of August 17-18. On that Saturday evening, 2002 NY40 should become as bright as magnitude 9.3 during the period when it is well placed for viewing from North America. Its angular velocity will exceed 4 arcminutes per minute, a motion easily perceptible in small telescopes. Sky & Telescope plans to issue detailed observing instructions, through AstroAlerts and SkyandTelescope.com, in the days leading up to this rare event. A mere 24 hours after it goes by, 2002 NY40 plunges hopelessly beyond reach of Earth-based telescopes as it heads in toward the Sun. (We are then viewing its unilluminated backside, which explains why it becomes so faint, so fast.) Meanwhile, professional astronomers are gearing up to make the most of this encounter. "2002 NY40 is a potentially very good radar target for mid-August," notes Mike Nolan of Arecibo Observatory and Cornell University. In a message posted on the Minor Planet Mailing List ( http://www.bitnik.com/mp ), Nolan urges advanced amateurs to obtain detailed photometry of the asteroid on the nights leading up to the flyby. A good light curve, revealing the object's rotation rate, would help in selecting the instrumentation to be used with the Arecibo 1,000-foot radio dish. While there is no danger of 2002 NY40 striking the Earth during this flyby, a future impact has not been ruled out. Both NEODyS, operated by the University of Pisa, and NASA's Near-Earth Object Program Office at JPL have identified a number of very close encounters in the years to come. These occur either around August 18th as the asteroid heads in toward the Sun, or else near February 14th when it is on the way out. Both agencies are focusing a flyby just 20 years from now (on August 18, 2022), when there appears to be a 1-in-500,000 chance of an impact -- extremely unlikely, but worrisome just the same.
(3) MORE SUPPORT FOR LARGE SURVEY TELESCOPE (LSST) David Morrison On July 11 the United States National Research Council released its recommendations for an Integrated NASA Solar System Exploration Strategy for the next decade. Among its Crosscutting Themes and Key Questions is: 10. What hazards do solar system objects present to Earth's biosphere? To deal with this issue, the NRC recommends that NASA partner equally with the National Science Foundation (NSF) to build and operate a survey facility, such as the Large-Aperture Synoptic Survey Telescope (LSST) previously described in the NRC's recommendations for astronomy and astrophysics. Thus the LSST with its objective of extending the Spaceguard Survey down to 300 m objects has now been recommended by two separate NRC panels for high priority at both NASA and the NSF. Following are some quotes on LSST from the earlier NRC Astronomy & Astrophysics Survey Committee (2001): The Large-aperture Synoptic Survey Telescope (LSST) is a 6.5-meter-class optical telescope designed to survey the visible sky every week down to a much fainter level than that reached by existing surveys. It will catalog 90 percent of the Near-Earth Objects larger than 300 meters and assess the threat they pose to life on Earth. It will find some 10,000 primitive objects in the Kuiper Belt, which contains a fossil record of the formation of the solar system. It will also contribute to the study of the structure of the universe by observing thousands of supernovae, both nearby and at large redshift, and by measuring the distribution of dark matter through gravitational lensing. All the data will be available through the [proposed] National Virtual Observatory, providing access for astronomers and the public to very deep images of the changing night sky. [The estimated cost] of the LSST is $170 million. (p 10-11) By surveying the visible sky every week to a much fainter level than can be achieved with existing optical surveys, LSST will open a new frontier in addressing time-variable phenomena in astronomy. This 6.5-m-class optical telescope will detect 90 percent of the Near-Earth Objects larger than 300 meters within a decade, and will enable assessment of the potential hazard each poses to Earth. . . (p 38-39) With its huge array of detectors, LSST will collect more than a trillion bits of data per day, and the rapid data reduction, classification, archiving, and distribution of these data will require considerable effort. The resulting database and data-mining tools will likely form the largest non-proprietary data set in the world and could provide a cornerstone for the National Virtual Observatory. (p 108) Study of the history of collisions of asteroids and comets with Earth provide the framework for understanding cataclysmic climate changes over geological time scales. While far rarer now than during the first billion years of the solar system's history, collisions of comets and asteroids with planets still take place. On Earth, such collisions can produce dramatic environmental events, from giant tidal waves to Earth-girdling dust clouds that can alter climate for centuries and in some cases lead to mass extinctions of species. Astronomers now have the tools to detect comets and Earth-crossing asteroids of size sufficient to threaten human civilization and to assess the threat of such a collision. (p 154) |
