Comparison of TRAPPIST-1 to the Solar System

Spitzer_ssc2021-02b_1024

spitzer_ssc2021-02b January 28th, 2021

Credit: NASA/JPL-Caltech

This graph presents measured properties of the seven TRAPPIST-1 exoplanets (labeled b through h), showing how they stack up with one another as well as with Earth and the other inner rocky worlds in our own solar system. The relative sizes of the planets are indicated by the circles. All of the known TRAPPIST-1 planets are larger than Mars, with five of them within 15% of the diameter of Earth.

The vertical axis shows the uncompressed densities of the planets. Density, calculated from a planets mass and volume, is the first important step in understanding its composition. Uncompressed density takes into account that the larger a planet is, the more its own gravity will pack the planets material together and increase its density. Uncompressed density, therefore, usually provides a better means of comparing the composition of planets.

The plot shows that the uncompressed densities of the TRAPPIST-1 planets are similar to one another, suggesting they may have all have a similar composition. The four rocky planets in our own solar system show more variation in density compared to the seven TRAPPIST-1 planets. Mercury, for example, contains a much higher percentage of iron than the other three rocky planets and thus has a much higher uncompressed density.

The horizontal axis shows the level of illumination that each planet receives from its host star. The TRAPPIST-1 star is a mere 9% the mass of our Sun, and its temperature is much cooler. But because the TRAPPIST-1 planets orbit so closely to their star, they receive comparable levels of light and heat to Earth and its neighboring planets.

The corresponding habitable zones regions where an Earth-like planet could potentially support liquid water on its surface of the two planetary systems are indicated near the top of the plot. The the two zones do not line up exactly because the cooler TRAPPIST-1 star emitting more of its light in the form of infrared radiation that is more efficiently absorbed by an Earth-like atmosphere. Since it takes less illumination to reach the same temperatures, the habitable zone shifts farther away from the star.

The masses and densities of the TRAPPIST-1 planets were determined by measurements of slight variations in the timings of their orbits using extensive observations made by NASAs Spitzer and Kepler space telescopes, in combination with data from Hubble and a number of ground-based telescopes. The latest analysis, which includes Spitzers complete record of over 1,000 hours of TRAPPIST-1 observations, has reduced the uncertainties of the mass measurements to a mere 3-6%. These are among the most accurate measurements of planetary masses anywhere outside of our solar system.

Provider: Spitzer Space Telescope

Image Source: http://www.spitzer.caltech.edu/images/6856-ssc2021-02b-Comparison-of-TRAPPIST-1-to-the-Solar-System

Curator: Spitzer Space Telescope, Pasadena, CA, USA

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Image Details

Image Type
Artwork
Object Name
TRAPPIST-1
Subject - Milky Way
Planet > Type > Terrestrial
Star > Spectral Type > M

Distance

Universescale1
40 light years
Spitzer_ssc2021-02b_1280
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ID
ssc2021-02b
Subject Category
B.1.1.1   B.3.3.7  
Subject Name
TRAPPIST-1
Credits
NASA/JPL-Caltech
Release Date
2021-01-28
Lightyears
40
Redshift
40
Reference Url
http://www.spitzer.caltech.edu/images/6856-ssc2021-02b-Comparison-of-TRAPPIST-1-to-the-Solar-System
Type
Artwork
Image Quality
Good
Distance Notes
Facility
Instrument
Color Assignment
Band
Bandpass
Central Wavelength
Start Time
Integration Time
Dataset ID
Notes
Coordinate Frame
Equinox
Reference Value
Reference Dimension
Reference Pixel
Scale
Rotation
Coordinate System Projection:
Quality
FITS Header
Notes
Creator (Curator)
Spitzer Space Telescope
URL
http://www.spitzer.caltech.edu
Name
Email
Telephone
Address
1200 E. California Blvd.
City
Pasadena
State/Province
CA
Postal Code
91125
Country
USA
Rights
Publisher
Spitzer Science Center
Publisher ID
spitzer
Resource ID
ssc2021-02b.tif
Metadata Date
2021-01-27
Metadata Version
1.2
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Detailed color mapping information coming soon...

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Universescalefull
40 light years