Planets and exoplanets

Rosa M. Ros, Hans Deeg, Ricardo Moreno

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International Astronomical Union

Technical University of Catalonia, Spain

Canarian Astrophysical Institute, Spain

Colegio Retamar de Madrid, Spain

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Goals

• Understand the meaning of the numerical values found in the data tables of the Solar System planets
• Understand the main characteristics of�extra-solar planetary systems

Solar system

We look for models that provide information,

not only arts and crafts.

According to the content

We want models with scientific content and those that display some concrete points

Activity 1: Distances from the Sun

Activity 2: Model of Diameters

Activity 2: Model of Diameters�

T-shirt with the diameters of the planets to scale

Activity 3: Diameters and distances from the Sun

Usually a school yard only reaches out to Mars

Activity 3: Model of diameters and distances in the playground ...

Activity 4: Model in the city (Barcelona) �

Model in the city of Metz (France)

Activity 5: Model of times

• c = 300 000 km/s

The time it takes light to go from Earth to Moon is:

t = distance EM / c = 384 000 km / 300 000 = 1.3 s

How would a conversation

between planets

by “video” be?

Sunlight takes to get to ...

Activity 6: The Sun as seen from the planets

• α = tan α = radius Sun / distance to Sun�= 700 000/150 000 000 = 0.0045 radian = 0.255°
• From the Earth, the Sun measures 2 α = 0.51 °

Activity 6: The Sun as seen from planets

Activity 7: Model of densities

Activity 8: Flattening Model

• Cut cardboard strips of 35 x 1 cm.
• Attach them to a cylindrical stick 50 cm long and 1 cm in diameter. Leave the lower end loose so that it can move along the stick.
• Rotate the stick in between your hands with quick rotations in one direction and the other. The centrifugal force deforms the cardboard bands as planets are deformed.

Activity 8: Flattening

Activity 9: Orbital Periods model

• Attach a nut to one end of a rope and hold the rope opposite to it. Turn the rope over your head.
• As you release more rope, it takes longer to complete an orbital period
• If you remove some of the rope, it takes less time

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Activity 9: Earth orbital data

The average orbital velocity v = 2π R / T

For the Earth

v = 2π x 150 x 10⁶/365

v = 2 582 100 km/day = 107 590 km/h = 29.9 km/s

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(The average orbital speed of Sun around the galactic centre�is 220 km/s or 800 000 km/h.)

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Activity 9: Orbital data

Activity 10: Model of surface gravitational accelerations

• Surface gravity, F = G M m/d², with m = 1, d = R. Thus g = G M / R², where M = 4/3 π R³ ρ
• Replacing: g = 4/3 π G R ρ

Activity 10: Surface gravitational accelerations

Activity 11: Model of "impact craters”

• Cover the floor with newspapers to prevent a mess
• In a shallow box, set a layer of 1 or 2 cm of flour with a strainer to make the surface very smooth
• Sprinkle a layer of a few millimetres of cocoa powder over the flour with the strainer
• From about 2 m high, drop a tablespoon of cocoa powder to create marks like impact craters
• The used flour can be recycled for a new experiment

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Activity 12: Escape velocity

• E_kin = ½ mv²
• E_pot = -GM_planetm/R_planet
• E_mec= E_kin +E_pot = 0
• g_planet = GM_planet/R²_planet

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Then: -GM_planetm/R_Planet + ½ mv² = 0

½ mv² = g_planetmR_planet

the scape velocity results:

v = (2gR)^1/2

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Activity 12: Escape velocity

Activity 12: Rocket launch

• Cardboard
• Film container
• ¼ Effervescent tablets

Extrasolar planetary systems

In 1995 Michael Mayor and Didier Queloz announced the detection of an exoplanet orbiting 51 Pegasi

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2M1207b directly imaged (ESO)

The first image of an exoplanet

2003 March 16th

We depend on the technology

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Galilei observed Saturn with his telescope in 1610 for the first time. He did not see a fine ring but interpreted it as a star with three bodies.

You had to wait for Huygens (1659) with a better telescope to solve the ring. For this reason the painting of Rubens (1636-1638) symbolizes Saturn with three objects according to the discovery of Galilei.

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Names for exoplanets

A letter is placed after the name of the central star starting with "b" for the first planet found in the system

(e.g. 51 Pegasi b).

The next planet is named with the next letter of the alphabet c, d, e, f, etc.

(51 Pegasi c, 51 Pegasi d, 51 Pegasi e or 51 Pegasi f).

Exoplanet detection methods

Many methods are used:

• Radial Velocity and Doppler Effect
• Transit Method
• Microlensing
• Others

Detection Method: Radial Velocity

The variation of the radial velocity of the star when orbiting the barycenter of the planet and star system is measured using the Doppler Effect.

It was with this method that the first exoplanet 51 Pegasus b was detected.

Activity 13: Doppler Effect

The Doppler effect is the change of the wavelength of the light when the source is in motion.

When the source approaches the wavelength is shortened and the observed light shifting to the blue part of the visible spectrum.

When it moves away, the wavelength lengthens and the observed light shifting to the red part of the visible spectrum.

Activity 13: Doppler Effect

It has been reproduced by reproduced with a bucket of water, a cap with chain and the mobile flash.

Detection Method: Transits

During the transit of an exoplanet, the brightness of the star undergoes a small decrease.

For solar-type stars and Jupiter-sized planets, the brightness decrease is approximately 1%, in the case of Earth-sized planets the decrease is around 0.03%.

Activity 14: Transit simulation

Using two balls: one large for the star and one small for the exoplanet orbiting the star.

With the observer in the same plane of the orbit and observing from that place, you will see the exoplanet passing in front of the star and the brightness of the star decreasing.

But if the observer is not in the same plane of orbit, no change in the brightness curve will be observed.

Observer in the plane of the orbit

Observer out of the plane of orbit

Detection Method: Micro Lensing

There is an enlargement or distortion that highlights the star-exoplanet system, due to the alignment of the system with a star or object that makes the gravitational lens.

There must be complete visual alignment between the three bodies (earth, object-lens and star-exoplanet).

Activity 15: Simulation of microlenses

With only one wine glass foot, nothing is seen.

With a pair of wine glass feet

Then we pass one over the other and a point emerges and then even two.

Detection Method: Direct

The image of the star is studied to determine the exoplanets around it.

Due to the amount of light emitted by the star, it is not easy to carry out.

2013 known exoplanets according to the different detection methods

There are more than 2000 exoplanet systems confirmed and several thousand candidate exoplanets

Jet Propulsion Laboratory (NASA; http://planetquest.jpl.nasa.gov/)

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The masses are compared with Jupiter (1.9 x 10²⁷ kg) or the Earth (5.97 × 10²⁴ kg).

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Technological limits are the cause.

Models of exoplanet systems

Activity 16: Scale models of exoplanetary systems

Distance 1 AU = 1 m

Diameter 10000 km = 0.5 cm

Kepler 62

Ups And

Gl 581

Trappist-1

Activity 16: Build Solar System:

Host Star Sun G2V, Diameter of the Sun in the model is 35 cm

Distance 1 AU = 1 m

Diameter 10000 km = 0.5 cm

Activity 16: Build 1st exoplanetary system:

Distance 1 AU = 1 m

Diameter 10000 km = 0.5 cm

Host Star Ups Andromedae F8V is at 44 l.y. in And., Diameter 1.28 of the Sun in the model is 45 cm

Activity 16: Build “terrestrial” planets

Host star Gliese 581 M2,5V is 20,5 l.y. in Libra, Diameter 0.29 of the Sun in the model is 10 cm

Distance 1 AU = 1 m

Diameter 10000 km = 0.5 cm

Host star Kepler 62 K2V is at 1200 l.y. in Lyr,. Diameter 0.64 of the Sun in the model is 22 cm

Activity 16: Build "habitable terrestrial"planets

Distance 1 AU = 1 m

Diameter 10000 km = 0.5 cm

Possible habitability of exoplanets

• In the habitable zone of Kepler-62: the two exoplanets could have liquid water on their surfaces. For Kepler-62e, which is near the interior of the habitable zone, this would require coverage of reflective clouds that reduces the radiation that heats the surface. Kepler-62f, on the other hand, is in the outer zone of the habitable zone

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Host star Trappist 1 M8V is at 40 l.y. in Acuarius,

Diameter 0.1 of the Sun in the model is 4 cm

Activity 16: Build “habitable terrestrial”planets

Distance 1 AU = 1 m

Diameter 10000 km = 0.5 cm

Possible habitability of exoplanets

• In the Trappist-1 system are rocky and could have large amounts of water on their surface, either liquid, in the form of steam, or as an ice crust. In the habitable zone of Trappist 1 is Trappist-1e which appears to have a dense nucleus, comparable to Earth which seems to indicate that of all the planets in this system, this is the most Earth-like and is likely to have a protective magnetosphere.

Conclusions

• Knowledge is more "concrete" of planets
• Relationships establish "parameters" that allow a better understanding of dimensions
• The solar system "is empty"
• Introduction of exoplanets. Recognize the methods for detection.

Thank you for your attention!