After observing hundreds of comets as a bonus to its primary mission, the twin STEREO telescopes have now also detected their first extrasolar planet. Experts at NASA are thrilled with the capabilities this mission displays nearly without interruption.
The purpose of the Solar Terrestrial Relations Observatory is to keep two eyes on the Sun. The mission is made up of two identical satellites that travel in the same orbit around the Sun.
One of the probes travels in front of our planet, while the other trails behind. Using this setup, experts can get 3D views of the Sun, and also of events taking place in the star's atmosphere.
STEREO is very good at keeping track, and exploring the physics, of coronal mass ejections (CME). The Heliospheric Imager (HI) is the primary instrument used for this. The device works by looking at a wide field around the Sun.
This enables it to see the CME unfold, but it also carries an added advantage. When no solar activity merits its attention, the instrument is trained to make other observations. Recently, one of these extracurricular activities involved the discovery of STEREO's first exoplanet.
According to mission controllers, this is possible because the observatory can take images every 40 minutes for as much as 20 days in a row. Experts tend to use these datasets for detailed survey studies.
It is also possible to conduct research on variable stars using the same approach, and the conclusions of the latest such study revealed the existence of 263 eclipsing variable stars, of which 122 were previously unknown, Universe Today
During the study, STEREO also looked at the star HD 213597, which was determined to be a strong candidate for hosting an exoplanet. Based on analysis of its light curve, experts determined that an object passes regularly in front of the star, and found that it's too small to be classified as a star.
Follow-up studies are however required to demonstrate that the object is an exoplanet. The STEREO team is convinced that observations carried with larger, validating telescopes will support the findings.
When space observatories discover exoplanet candidates, the datasets are sent to large, ground-based instruments, which then spend a lot of time verifying the proposals. This is a difficult task, but it enables the space instruments to direct their attention elsewhere.
Even the observations made by the NASA Kepler planet-hunting telescope go through this review process, even if the orbital instrument was developed specifically for finding exoplanets.