Astronomers tried to understand what TESS would find before it launched. TESS would find between 4430 and 4660 new exoplanets during its two-year mission, according to one study.
TESS is in an extended mission now that the primary mission is over. The TESS mission has been going for 1.5 years. The data from the primary mission may be hiding more exoplanets. TESS isn't finished yet.
TESS becomes an object of interest when it finds a new exoplanet candidate. The TOI count has been boosted by another set of exoplanet candidates. The new batches have doubled the number of TOIs. The majority of this batches is from the Minnesota Institute of Technology. The MIT post-doc leads the search.
TESS found over 2,400 TOIs last year. Kunimoto said in a press release that TESS has reached more than twice that number.
Confirmation is required when TESS identifies a TOI and feeds it into the TESS Follow-up observing program. The TFOP has over 40 groups of astronomy at facilities around the world. Their observations confirm the candidates as actual exoplanets and also refine them. The planet can be called a confirmed exoplanet once the TFOP does its work.
TESS is a mission that has a lot of data. Much of the data requires manual inspection, as exoplanet candidates hide in that data. It's a time-Consuming task. The Faint Star Search uses a modified method to find exoplanet candidates.
The PM is different from the Faint Star Search FSS. TESS focuses on bright stars, but the FSS focuses on exoplanets around faint stars. The Faint Star Search uses an independent vetting process to identify promising planet candidates around these fainter stars.
The two-year primary mission covered 85% of the sky. The southern hemisphere sky was observed by the satellite in the first year. The first year of TESS's extended mission is where this new group of exoplanets candidates came from. The Southern Hemisphere sky was studied in the first year of the mission. Dozens of new TOIs were created by the re-observation.
The image is from NASA/MIT/TESS.
The team that vets and releases TOIs at MIT has found dozens of additional candidates.
TESS's extended mission is different from the primary mission. It went from 30 minutes in the PM to 10 minutes in the EM. TESS will observe a star three times longer than the PM.
The EM has a lower false-positive rate than the PM. More data means more transits and better constraints on planet parameters, because most targets in the PM were re-observed.
The PM observations were slower than the EM full-frame image observations, but they were observed at an improved 10-minute cadence. A star observed in the EM will have three times as many data points as one observed in the PM over the same time period. This helps to distinguish transit shapes and helps TOI vetters spot tell-tale signs of astrophysical false positives in the lightcurves before they alert them as TOIs.
TESS's data is affected by false positives. They occur at different rates in the PM, the EM, and the Faint Star Search. The data gathered in the PM, EM, and FSS is different from the TESS data.
Kunimoto provided an explanation for how false positives fit together.
There are some Prime Mission TOIs in the official Prime Mission Catalog.
The high number of FPs in the primary mission is an expected part of the process. The PM has the highest number of confirmed planets. Why?
These are the oldest TOIs, which means they have had the community's attention for the longest, and will have received the most follow-up work. Most TOIs in the Prime Mission have not been dispositioned as false positives or confirmed as planets yet.
The Prime Mission TOIs look like 27% are false positives, 20.6% are legitimate planets, and the remaining 52.4% do not have final dispositions.
The data from the Extended Mission looks different. The data has not been scrutinized as much as the PM.
The number of ToIs was identified by the EM. The Faint Star Search is not included.
The leftover 77.5% of planets are still candidates, according to Kunimoto. The data hasn't been around long, so more TOIs are still candidates compared to the PM.
The Faint Star Search is next. The FSS is a different way of combing through the data. There isn't as much light since the target stars are fainter. The data isn't as strong and there will be more False Positives. It means the vetting process is more difficult.
The first 1617 TOIs were found using data from the Prime Mission, and the latest batches of 416 pushed TESS over 5000.
The current results from the FSS can be found here.
The FSS data contains more false positives than the other missions. That is not unexpected.
Kunimoto explains why.
Kunimoto said that he expected the Faint Star TOIs to have a higher false-positive rate. The light curves of fainter stars make it more difficult to find planets.
The faint stars lead to false positives. Most of them are Jupiters. Why? A stronger signal is created by blocking more light.
Kunimoto said that most Faint Star TOIs should be giants, which have deep transit depths that can still stand out.
Giants are more easily confused with false positives. Kunimoto said that fainter stars have less stellar information available, so in some cases we don't know the mass or temperature of the host star.
Astronomers are in a tough spot because of less light. Light from the star is needed to measure the star's properties. They don't know much about the potential planet that is based on the star itself.
We have to assume certain stellar parameters in order to estimate, for example, how large the planet is, so it may be the case that some Faint Star TOIs would be too large to be planetary.
There is nothing wrong with false positives. They are an expected part of the process and don't represent a failure. They are easier to identify than actual planets.
It is much easier to identify a false positive than it is to confirm a planet.
The data from TESS is a snapshot in time. It is possible that TOIs listed as planet candidates have already been received.
It is not possible to know what TESS's final numbers will be. Two exoplanets were discovered around a pulsar in 1992. We know of 4903 confirmed exoplanets as of January 10th, 2022. T.
TESS is still working and there is a lot of data. There are 5164 TESS candidates and 176 confirmed planets.
TESS is a triumph so far.
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