Astronomers have identified thousands of exoplanets with the aid of instruments like the Kepler Space Telescope, but we don’t know much about most of those worlds. From a great distance, Earth and Venus would appear to be very similar, but of course, we know that Earth is quite habitable and Venus has clouds of sulfuric acid. Scientists have taken a step toward better understanding the environment of exoplanets by studying a gas giant called KELT-9b. For the first time, scientists have detected iron and titanium on an exoplanet.
While Earth and Venus may look similar, there’s no mistaking KELT-9b for an Earth-like planet. It’s 2.88 times the mass of Jupiter and orbits the blue giant star KELT-9 every 1.5 Earth days. It also has a surface temperature of 6,740 degrees Fahrenheit (3,626 degrees Celsius). That means it’s probably hot enough to tear water molecules apart.
Astronomers turned the Telescopio Nazionale Galileo in the Canary Islands toward KELT-9b last summer, observing as the planet transited in front of KELT-9. They collected the spectra of light shining through KELT-9b’s atmosphere and then subtracted the signature of light collected just from the star. That left spectral lines of titanium and iron. The team even simulated the atmosphere of KELT-9b without using this data to confirm that it should have visible iron.
This marks the first time either element has been detected on an exoplanet. To make sure the readings were not from the star itself, the team identified a Doppler shift in the signal, indicating it came from the planet as it moved through space.
It’s impossible with current technology to detect iron or titanium on Earth-like exoplanets because it’s not a component of the atmosphere. A gas giant like KELT-9b is a very different story. This research gets us closer to proper characterization of exoplanets, which is essential to understanding whether they could support life. A gas giant couldn’t support life as we know it, but understanding the atmosphere of Jupiter-like planets can help us make educated guesses about the composition of other planets in the same solar system.
Future projects like the James Webb Telescope will allow scientists to observe exoplanets in more detail than ever before. Meanwhile, NASA’s TESS mission is scouring the sky in search of new exoplanets to analyze. This study provides a roadmap to survey the atmospheres of such planets, which could help unlock new areas of research.