Asteroids Swinburne Astronomy Online 3D PDF c SAO 2012

Transcription

1 Asteroids Swinburne Astronomy Online 3D PDF c SAO 2012

2 1 Description 1.1 Asteroids Asteroids, or minor planets, are small, often irregularly-shaped rocky bodies that are left over from the planet formation process. They orbit the Sun in relatively well defined groups, the most common and heavily populated group being the main belt asteroids between the orbits of Mars and Jupiter. Here we model the three-dimensional shapes of four Apollo type Near Earth Asteroids: 1620 Geographos, 4179 Toutatis, 4769 Castalia and 6489 Golevka. The data for these 3D visualisations come from the Small Body Radar Shape Models V2.0 of the NASA Planetary Data System archive. The shapes of the asteroids were mapped using the 70-m Goldstone Solar System Radar (GSSR), which is part of the NASA Deep Space Network, and the 305-m Arecibo Telescope, which is part of the National Astronomy and Ionosphere Center. The orbit of each asteroid in the Solar System is shown on the page following their 3D model. Asteroid 1620 Geographos was discovered in Its semi-major axis is 1.25 AU and it has an orbital eccentricity of Its orbit crosses both Mars and Earth. Radar observations show it to be very elongated, with dimensions 5.1 km x 2.2 km x 2.0 km. Follow this link to watch a movie of 1620 Geographos rotating. Asteroid 4179 Toutatis was first sighted in 1934 but not observed again until It has a semi-major axis of 2.5 AU and eccentricity It is in near orbital resonance with both Jupiter and the Earth, and its eccentric orbit crosses the orbits of both Mars and Earth. Its dimension are 4.8 km x 2.4 km x 2.0 km. Asteroid 4769 Castalia was discovered in Its semi-major axis is 1.06 AU and its eccentricity is Its orbit crosses Venus, Earth and Mars. Radar measurements show its dimensions are 1.8 km x 1.1 km x 0.9 km. Asteroid 6489 Golevka was discovered in Its semi-major axis is 2.50 AU and its eccentricity is Its orbit also crosses both Mars and Earth. It has dimensions 0.70 km x 0.59 km x 0.50 km. 2

3 1.2 How to use this 3D PDF The interactive 3D content appears on the next page of this document. You can interact with the 3D content in a variety of ways. Most of these can be found in the 3D toolbar (see below) that appears when you move the mouse cursor over the 3D figure. To start, click and hold the left mouse button anywhere within the 3D figure. Then move the mouse around and see how the orientation changes. You can use the right mouse button in the same way to zoom in and out. Other interaction modes are also available. You can explore these by clicking on the drop-down menu of the left-most icon on the 3D toolbar. Every 3D figure has a default view, which can be returned to by selecting View 1 from the toolbar Views menu. Some figures may also have other interesting views available for you to try. There are some additional keyboard shortcuts for you to use. (Note that you must first left mouse click on the 3D figure to utilise these shortcuts.) arrow keys (up, down, left, right) rotate the object +, - zoom in or out a autospin *, / increase, decrease the autospin speed [, ] roll the object clockwise, anti-clockwise h return to the default view Some 3D figures may also allow you to show or hide certain types of objects from view. If available, this option will appear as a text link below the 3D figure, e.g. Click here to... Note: The free Adobe Reader (Version 8 or higher) is required for these 3D PDFs. 3

4 2 The asteroids 2.1 Geographos 4

5 2.1.1 The orbit of Geographos 5

6 2.2 Toutatis 6

7 2.2.1 The orbit of Toutatis 7

8 2.3 Castalia 8

9 2.4 The orbit of Castalia 9

10 2.5 Golevka 10

11 2.6 The orbit of Golevka 11

12 3 Credits The data used for this PDF was sourced from the NASA Planetary Data System (Neese, C., Ed. Small Body Radar Shape Models V2.0. EAR-A-5-DDR- RADARSHAPE-MODELS-V2.0, NASA Planetary Data System, 2004). Data for the asteroid orbits was sourced from JPL s HORIZONS ephemerides system. The 3D content in this PDF document was prepared with S2PLOT (Barnes et al., 2006, PASA, 23, 82; Barnes & Fluke, 2008, New Astronomy, 13, 599). Funding for this project was partially supported by Open Universities Australia. Swinburne Astronomy Online would like to thank Chris Fluke, Sarah Maddison and Artem Bourov for their work on this project. 12