|
Asteroidal Objects: 456 km (Ceres) down to micron sized grains Grain Temperature: 180 K (-135 F) Grain Distance: 2.1 - 3.3 AU |
Objects: 1.6 micron dust grains up to ? Grain Temperature: 340 K (150 F) Grain Distance: 2.5 - 6.0 AU |
zeta Leporis is distinctive since the dust grains around it are warm and close to the star, at the distance of the terrestrial planets. Dust in other systems is cold and far from the star, at distances similar to or beyond the Kuiper Belt in our solar system.
Star |
Fnu(60 micron)/Fnu(25 micron) |
Radius (AU) |
zeta Leporis |
0.28 |
< 6 |
HR 4796A |
2.2 |
70 |
beta Pictoris |
2.2 |
up to 500 |
Vega |
0.86 |
110 |
Fomalhaut |
1.8 |
140 |
We hope to study the zone of terrestrial planet formation around zeta Leporis.
The solid line is the point spread function for the standard star Capella, normalized to the observations of zeta Lep, while the diamonds show the azimuthally averaged data for zeta Lep. The colored lines are models for the spatial extent of the dust convolved with the point spread function of Capella. The red, green and blue models assume a central point source with an angular radius of 0.2", 0.3" and 0.4" (4 AU, 6 AU and 8 AU) respectively. In each model, the power is divided equally between the pont source and the ring, consistent with the SED.
|
at 11.7 micron: FWHM(Capella) = 0.47" FWHM(zetaLep) = 0.46" |
at 17.9 micron: FWHM(Capella) = 0.49" FWHM(zetaLep) = 0.57" |
Dust grains orbiting zeta Lep will slowly spiral into the star on a timescale of 20,000 years (depending on particle size and distance) because of Poynting-Robertson Drag.
The age of zeta Lep is estimated to be between 50 - 500 million years, much older than the lifetime of the grains.
The grains must be replenished from a reservoir such as collisions between parent bodies!
Violent collisions in our solar system occurred during the period of Late Heavy Bombardment. Craters formed at this time are visible on the surfaces of the moon and terrestrial planets.
We can estimate the mass in parent bodies assuming that the grains are in steady state.
For comparison,