Exoplanets!

 I did a lot of citizen science observations during my sabbatical last fall. I was especially interested in trying to use my time to make observations of exoplanets.

My exoplanet observations were all made using the transit method. These planets are impossible to see directly but they can still be detected. As an orbiting exoplanet passes directly in front of (transits) across the face of its star it makes a mini-eclipse and blocks a small percentage of the star’s light. This can be measured even with small telescopes, making this technique the most successful method for studying exoplanets. A typical exoplanet observation lasts from four to five hours, though some are shorter, and others are longer.

Over the course of the semester, I attempted to observe sixteen exoplanet transits. Due a variety of factors (weather, equipment failure, etc.), not all of them were successful. All of my observations were made with a Unistellar eVscope2. A summary of my exoplanet observations is included below along with other findings about these exoplanets.

A note about exoplanet names. Most of them are terrible acronyms of the survey the first discovered the exoplanet, followed by a letter, which indicates the order of discovery within that particular system (starting with the letter b). As an example WASP stands for Wide Angle Search for Planets. WASP-33b refers to the first planet (b) within the 33^rd system discovered by that survey. Some exoplanet names are acronyms within acronyms. TOI is TESS Object of Interest. TESS is the Transiting Exoplanet Survey Satellite.

XO-7b               Observed August 23/24, 2024 & October 5-6, 2024

A graph of the science results is generated for each exoplanet observation. The graph for one of my two observations of XO-7b is above. Note that the dates are given in Universal Time (essentially, the time in Greenwich, England) which is why these graphs don’t always agree with the local date.

XO-7b is a gas giant planet that orbits a spectral type F star that is larger and hotter than the Sun. It is located 764 light-years from Earth in the constellation of Draco, the Dragon. It is an example of a “hot Jupiter” type planet, as are the majority of exoplanets that can be observed with a small telescope. It is located very close to its parent star, at a distance that is just 4.421% of the distance Earth is from the Sun. It orbits its parent star every 2.9 Earth days! The planet is smaller than in mass (0.709 times Jupiter’s mass or 225 times Earth’s mass), but larger than Jupiter in size. Its larger size is because the tremendous heat that it receives from its star essentially inflates the planet giving it a radius that is almost 1.4 times that of Jupiter’s. The calculated temperature for the planet is 2,678^oF. 

TOI-1518b                     Observed August 27/28, 2024

Note: there were clouds at the end of the observation.

TOI-1518b is a gas giant planet that orbits a rapidly rotating F-type star, which is larger than the Sun (1.95 times the Sun’s radius) and 2,750^oF hotter than the Sun’s surface temperature. It is located 737 light-years from Earth in the constellation of Cepheus, the King. The planet has a mass 2.3 times that of Jupiter and a radius that is 1.9 times that of Jupiter. More massive gas planets tend to be smaller as the extra mass causes more compression from gravity. The fact that TOI-1518b is so large indicates that it is inflated due to the temperature caused by how close it is to its star. It orbits its star every 1.9 days in an orbit that is just 3.89% the size of the Earth-Sun distance. The planet is considered to be an ‘ultra-hot’ Jupiter. Its dayside temperature has been measured to be 5,367 ^oF! It is believed to have ionized iron vapor in its atmosphere.

TOI-1259 Ab                 Observed September 24/25, 2024

The TOI-1259 is a binary star system. The system is located 385 light years from Earth in the direction of the constellation of Draco, the Dragon. TOI-1259 A is a spectral type K star that has a radius 71% of the Sun’s and is about 2,000^oF cooler than the Sun. The other star, TOI-1259 B, is a white dwarf. The white dwarf is a distant companion, being 1648 times farther from A than the distance between Earth and the Sun. White dwarfs are essentially dead stars. In this case TOI-1259 B would have begun as a star that was more massive than A (1.59 times the mass of the Sun) and burned through its hydrogen fuel at a faster rate. It now has a mass of 0.56 times the mass of the Sun. Astronomers have determined the age of the white dwarf, and thus the age of the system, which is thought to be 4.8 billion years (Our solar system is 4.6 billion years old.).

The exoplanet is named TOI-1259 Ab. It is a gas giant planet with a mass is 0.44 of Jupiter’s but it is slightly larger than Jupiter in size (1.02x Jupiter’s radius). It orbits star A every 3.5 days at a distance of 4.07% of the Earth-Sun distance.

Observations at Palomar and Keck suggest that the planet receives extreme heating on its dayside which is both causing some of its atmosphere to escape to space and also driving extreme winds that blow from the dayside to the night side of the planet. The equilibrium temperature of the planet is estimated to be 1,190 ^oF. 

WASP-33b                    Observed September 25/26, 2024

WASP-33b is a gas giant exoplanet 398 light years in the direction of the constellation of Andromeda. It orbits a variable star which is larger (1.5 times the Sun’s radius) and nearly 3,000^oF hotter than the Sun. It orbits the star every 1.2 Earth days (!) at a distance that is just 2.39% of the distance between the Earth and Sun. Unlike most planets, WASP-33b has a retrograde orbit, meaning that it does not revolve in the same direction that its star rotates. It has a mass that twice that of Jupiter and is about 1.9 Jupiters in radius. The temperature of the exoplanet is 5,790^oF. Researchers using the Hubble Space Telescope have detected titanium oxide, a major component of sunscreen, in the atmosphere of this planet. Iron and silicon have also been detected in its atmosphere.

WASP-2b                      Observed September 27, 2024

WASP-2b is a hot Jupiter-type gas giant planet that orbits a K-type star located 500 light years from Earth in the direction of the constellation of Delphinus, the Dolphin. The planet’s host star has a mass that is 85% of the Sun’s, it is 82% of the Sun’s radius. It is 1,154^oF cooler than the Sun. The planet has an orbital period of 2.2 Earth days at a distance that is just 3.1% of the distance between the Earth and Sun. Its mass is 93.1% of Jupiter’s and it is slightly larger than Jupiter in size. The planet has a density similar to that of water. The temperature of the exoplanet is 1,855^oF. Spectroscopic observations suggest that it has a cloudy atmosphere. 

WASP-93b                    Observed September 28/29, 2024

WASP-93b is a hot Jupiter-type gas giant planet that orbits an F-type star located 1,208 light years from Earth in the direction of the constellation of Cassiopeia, the Queen. This star is both larger and hotter than the Sun.

The planet has an orbital period of 2.7 Earth days and orbits at a distance that is just 4.2% of the Earth-Sun distance. It has 1.47 times Jupiter’s mass and is 1.7 times Jupiter’s radius.  The planet’s equilibrium temperature is estimated to be 3,000^oF.

HAT-P-32b                    Observed October 4/5, 2024

HAT-P-32b is a gas giant planet that orbits a type F star located 943 lights from Earth in the direction of the constellation of Andromeda, the Princess. The planet has a mass that is just 68% that of Jupiter. It orbits its star at a distance that is just 3.3% of Earth’s distance from the Sun. Its close distance to its star has inflated the size of the planet making it nearly twice Jupiter’s radius. This in turn means that the planet has a low density. All of the “hot Jupiters” observed so far have densities lower than water’s 1 g/cm³, meaning that they are made of light materials (in our Solar System only Saturn, which has a density of 0.69 g/cm³ has density lower than water). HAT-P-32b has a density of just 0.1085 g/cm³  this is low enough to almost put it into the category of “super-puff” (yes, that’s a real thing) exoplanets, which have densities less than 0.1 g/cm³.

TIC 362220946.01     Observed October 10/11, 2024

TIC 362220946.01 is a possible exoplanet that was first observed by NASA’s TESS satellite. It was thought that this planet has an orbital period of 8 days and a mass that is 23 times that of Jupiter. I was one of nine observers from the U.S. and Mexico who looked this system in an attempt to confirm its existence and the possible orbital period of the planet. The results were inconclusive but there are suggestions that this could perhaps be a binary star system instead of a planetary system. Further observations may help to solve this puzzle.

WASP-77 Ab                Observed October 24/25, 2024

WASP-77 Ab is another “hot Jupiter” type gas giant planet. It is located 343 light years from Earth and orbits a Sun-like star in the constellation of Cetus, the Whale. The star is part of a wide binary system, where the other star is a spectral type K star that is smaller and cooler than the Sun.  has a mass 1.67 times that of Jupiter and is 1.23 times Jupiter’s radius. It orbits its star every 1.4 Earth days at a distance of 2.3% that of the Earth-Sun distance. The planet has a calculated temperature of just over 2,600^oF.

TOI 6881.01                 Observed October 31, 2024

The exoplanet known as TOI 6881.01 orbits a star that is 2,559 light years from Earth in the direction of the constellation of Perseus, the Hero. Its star is larger, hotter and more massive than the Sun. The planet orbits its star every 1.9769 days. The planet has a calculated equilibrium temperature of almost 3,100^oF. The planet has a mass that is essentially the same a Jupiter’s and a radius 1.44 times that of Jupiter, making it another “hot Jupiter” gas planet that has expanded from the extreme heat from being right next to its star.

TOI-5571.01                 Observed December 4, 2024 & December 18, 2024

TOI-5571.01 was initially detected by NASA’s TESS satellite, but its observations were widely spaced in time and so the orbital elements of this exoplanet were highly uncertain. Early observations suggested that the exoplanet could have an orbital period of 731 days (2 years) but was more likely to be something shorter. My observation was part of a campaign by Unistellar to help pin down the exact orbital period of the planet. My observations the night of December 4 (my birthday!) did seem to catch the exoplanet transiting in front of its star (though it was low in the sky), which may indicate that the planet’s orbital period is potentially 66 days, but further observations are needed.