Among thousands of known exoplanets, astronomers flag three that are actually stars

Thirty years ago, the first worlds beyond our solar system were discovered. Thousands of exoplanets have been confirmed in our universe. There are more than 5,000 planetary candidates that have yet to be confirmed. The list of planets has shrunk.

According to a study appearing in the Astronomical Journal, three and possibly four planets that were originally discovered by NASA are in fact misclassified. These planets are likely small stars.

Three planets that are too big to be planets were identified by the team using updated measurements of planet-hosting stars. The three objects are now estimated to be between two and four times the size of Jupiter, thanks to new and better estimates of stellar properties.

Most exoplanets are Jupiter-sized or smaller. Jupiter is already suspicious. The study's first author, a graduate student in MIT's Department of Earth, Atmospheric, and Planetary Sciences, says that a planet larger than that cannot be a planet.

A fourth planet, called Kepler-747b, is about the same size as Jupiter and comparable to the very largest confirmed planets. The amount of light it receives is too small to sustain a planet of its size. The team concludes that the planetary status of Kepler-747b is suspect but not implausible.

The current list of planets is more complete thanks to this study, says study author Avi Shporer, a research scientist at MIT's Kavli Institute for Astrophysics and Space Research. If you use a sample with a few other people, your results may be incorrect. It is important that the list of planets is not contaminated.

Ian Wong is a NASA Postdoctoral Program Fellow at NASA Goddard Space Flight Center.

The updates are good.

The initial goal was not to root out planetary imposters. Niraula wanted to look for systems with signs of tidal distortion.

If you have two objects close to each other, the pull of one will cause the other to be egg-shaped, which gives you an idea of how massive the companion is.

He came across a signal that was too large to be true when he looked through the catalog.

Shporer says, "We knew this could not be from a planet after we saw this ellipsoidal signal which was huge."

The team looked at both the star and the planetary candidate again. A periodic dip in starlight that signals a possible planet passing in front of its star is what led to the discovery of the planet. The dip shows the ratio between the size of the planet and the star. The size of the planet can be calculated by what the astronomer knows about the star. When it was discovered in 2016 it was based on less precise estimates than today.

The European Space Agency has a space-based observatory that is designed to precisely measure and map the properties and paths of stars. In the year of 2016 there was no available measurement of Kepler- . The object seemed to be a plausible-sized planet based on the stellar information that was available. With improved estimates, it was found to be three times the size of Jupiter.

Shporer says that the universe cannot make a planet of that size.

Tiny changes.

The team confirmed that a small star is in contact with a larger star, not a planet. They wondered if there was more.

This time, Niraula searched through the more than 2,000 planets in the catalog for updates to the size of stars. He discovered three stars whose sizes changed due to improved measurements. The team calculated the size of the planets around each star and found them to be about two to four times Jupiter's size.

There are now three objects that are not planets, and the fourth is likely not a planet.

The team expects that there won't be many more such changes to existing exoplanet catalogs going forward.

Shporer says that it comes from the better understanding of stars. The chances of a star being incorrect are much smaller. These misclassifications are not going to happen a lot more.

More information: Prajwal Niraula et al, Revisiting Kepler Transiting Systems: Unvetting Planets and Constraining Relationships among Harmonics in Phase Curves, The Astronomical Journal (2022). DOI: 10.3847/1538-3881/ac4f64 Journal information: Astronomical Journal Citation: Among thousands of known exoplanets, astronomers flag three that are actually stars (2022, March 15) retrieved 17 March 2022 from https://phys.org/news/2022-03-thousands-exoplanets-astronomers-flag-stars.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.