22: The Origin of Earth and the Solar System (Exercises)
- Page ID
- 2062
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Q22.1 How do we know what other planets are like inside?
Earth | Mars | Venus | Mercury | |
---|---|---|---|---|
Planet density (uncompressed) in g/cm3 | 4.05 | 3.74 | 4.00 | 5.30 |
Percent core | 16.8% | 10.3% | 15.8% | 43.2% |
Earth | Mars | Venus | Mercury | |
---|---|---|---|---|
Unsqueezed planet volume – km3 | 1.47 x 1012 | 1.72 x 1011 | 1.22 x 1012 | 6.23 x 1010 |
Core volume – km3 | 2.48 x 1011 | 1.77 x 1010 | 1.92 x 1011 | 2.69 x 1010 |
Earth | Mars | Venus | Mercury | |
---|---|---|---|---|
Unsqueezed core radius in km | 3900 | 1617 | 3581 | 1858 |
Unsqueezed planet radius in km | 7059 | 3447 | 6623 | 2458 |
Percent of radius that is core (see diagram below) | 55% | 47% | 54% | 76% |
[KP]
Q22.2 How do we know the sizes of exoplanets?
Plot showing how the star Kepler-452 dims as the planet Kepler-452b moves in front of it.
[KP, after Jenkins, J. et al, 2015, Discovery and validation of Kepler-452b: a 1.6REarth super Earth exoplanet in the habitable zone of a G2 star, Astronomical Journal, V 150, DOI 10.1088/0004-6256/150/2/56.]
Sun | Kepler-452 | Ratio | |
---|---|---|---|
Temperature (degrees Kelvin) | 5778 | 5757 | 1.0036 |
Luminosity (x 1026 Watts) | 3.846 | 4.615 | 1.20 |
Radius (km) | 696,300 | 768,317 |
* The temperatures of the sun and Kepler-452 are very similar, but the small difference is important. Keep 4 decimal places.
Decrease in brightness* | Earth radius (km) | Kepler-452b radius rplanet (km) | Kepler-452b radius/ Earth radius |
---|---|---|---|
197x 10-6 | 6378 | 10,784 | 1.7 |
* Because we know this is a decrease, you don’t need to keep the negative sign.
**Answers provided by Karla Panchuk