This blog, first published July 4, was updated on July 25 and August 24 to reflect the findings from Citizen Astronomers’ observations of exoplanet candidate TOI 1812.01 on July 17 and August 2. Read more about their results below – we still need more observations of this elusive planet on August 27!

This August, Unistellar observers around the world have the chance to help discover not one, but two important pieces of information about a distant exoplanet candidate. The exoplanet in question, which was found in 2020 by NASA’s planet-hunting TESS mission, is named TOI 1812.01. It’s thought to be a cool Jupiter, a rare class of exoplanet that could have moons with the conditions right for life.

On August 27, the distant world may transit, or pass in front of, its star, giving astronomers an opportunity to study it. TOI 1812.01 is still an exoplanet candidate, meaning astronomers need more information to confirm its existence — so the first piece of information they’re looking for is simply whether it exists or not!

As an exoplanet passes in front of its star, it blocks out a portion of the star’s light.

But there’s another big mystery surrounding this exoplanet. With just two observations from TESS, astronomers can’t yet determine TOI 1812.01’s orbital period, which is how long it takes the planet to orbit its star — current estimates range from 71 to 157 days. If observers see a transit on August 27, it would indicate a 112-day period.

The transit would be visible across a large swath of the Earth, but it would last 16 hours. So, to fight the rising sun, observers spread out across the world are needed — exactly like the Unistellar Network. In fact, 21 Citizen Astronomers from North America, Europe, and Japan observed TOI 1812.01’s star on July 17 and August 2 in search of a transit. They did not observe a transit on July 17, but Unistellar astronomers think there is tentative evidence for a transit on August 2! However, scientists had previously deemed the most likely period for this exoplanet to be 112 days. This 112-day period means a transit would take place on August 27, so for scientists to be sure they caught the transit on August 2, they need your help in ruling out a transit on August 27.

If Citizen Astronomers do catch a transit on August 27, it will mean that the most likely period determined by computer models is indeed correct, confirming an 112-day long year for this world. If they don’t, then our Unistellar Network members will have discovered that the most likely period for this planet does not reflect reality. In this case, Unistellar scientists will be able to confirm that a transit occurred on August 2 and that this exoplanet has a period of just 87 days. Either way, the results will be exciting!

Credit: NASA

An August 27 transit would first be visible in Japan, continue across China, and finish in Europe. Observations from Citizen Astronomers in Japan and Europe will be particularly important for piecing together the beginning and end of the potential transit. If that’s you, Unistellar could use your help to finish placing the final pieces of this puzzle!

Observing TOI 1812.01

If this is your first time observing an exoplanet transit, first check out our  Exoplanet Tutorial page for an overview of the techniques involved. Then, head to Unistellar’s Exoplanet Predictions page, select your location and click on the row for TOI 1812.01 – 27 August to find the observation settings and visibility map.

Our goal is to observe TOI 1812.01’s star during the times when the exoplanet is most likely to transit, based on astronomers’ calculations of its possible orbital periods. With your observations, we’ll be one step closer to knowing how long a year is on this faraway world!

If you have any questions, please reach out to us at [email protected].

The visibility map of TOI 1812.01’s transit. The orange diamonds denote partial visibility of the event, where an observer at that location will see a portion of the transit. Yellow diamonds denote full visibility, although tracking issues may occur due to the target’s high altitude. Your local time may vary from what is shown.

Further readings