Orbit for Hermes Dynamically Linked from 1937 to 2003

IRON AND ICE

Orbit for Hermes Dynamically Linked from 1937 to 2003
by Steven R. Chesley and Paul W. Chodas

illustration only

Pasadena (JPL) Oct 16, 2003
Using sophisticated orbit determination tools, the difficult problem of finding a precise orbit for the long-lost and recently rediscovered asteroid Hermes has been solved.

The recovery of Hermes was announced on October 15, 2003 by the Minor Planet Center (MPC) in Cambridge Massachusetts. The object was initially noted by Brian Skiff of the LONEOS asteroid search program at the Lowell Observatory in Arizona, and key follow-up measurements were provided by James Young of JPL's Table Mountain Observatory in California.

Tim Spahr of the MPC located prediscovery observations from the last 7 weeks and computed the new object's orbit. Noticing that the orbit was very similar to that of Hermes, last seen during its close approach in 1937, Spahr concluded that the new object was almost certainly Hermes. Definitive proof of the object's identity was still lacking, however, because an orbit linking the known positions in 1937 to those in 2003 could not be found.

Finding the precise orbit of Hermes is difficult because its trajectory is very chaotic. In the 66 years since it was last seen, the asteroid has made numerous close approaches to both the Earth and Venus. Since the orbital changes at each approach depend highly on the circumstances of the encounter, finding an orbit with the precise sequence of encounter conditions that links positions in 2003 to those in 1937 is a challenging problem in orbit determination.

We have now solved this problem by using the JPL Sentry impact monitoring software in a novel way. Starting from the 2003 positions, Sentry found twelve distinct dynamical pathways that produced encounters in 1937, each with a different sequence of intervening close approach circumstances.

Comparing these predicted 1937 encounters with the one determined directly from the 1937 observations, we were able to identify the most consistent candidate, and then zero in on the precise orbit that best matches the positions in both 1937 and 2003.

We now know that since it was last seen, Hermes has made eight close approaches to the Earth and Venus to within 0.06 AU, including an Earth approach to within about 1.6 lunar distances in 1942. The new orbit solution allows us to predict future close approaches with great accuracy; we can now predict that Hermes will not approach the Earth any closer than about 0.02 AU (8 lunar distances) within the next hundred years.

IRON AND ICE

Sunlight Makes Asteroids Spin In Strange Ways

Boulder - Sep 10, 2003
A new study by researchers at Southwest Research Institute (SwRI) and Charles University (Prague) has found that sunlight can have surprisingly important effects on the spins of small asteroids. The study indicates that sunlight may play a more important role in determining asteroid spin rates than collisions, which were previously thought to control asteroid spin rates. Results will be published in the Sept. 11 issue of Nature.

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.