An Exoplanet So Hot It Rains Iron May Be Even Hotter Than We Thought

Astronomers continue to be amazed by the fascinating glimpses provided by exoplanets planets beyond our Solar System. This includes WASP-76b. This planet is almost as large as Jupiter and the daytime temperatures on its surface are high enough to vaporize iron. Rain could also fall on the cooler night side.
Researchers have now given WASP76b another chance and found that it may be even hotter than originally thought. The key to this conclusion is the discovery that ionized calcium would require "significantly warmer" conditions for formation than previously thought.

We know that temperatures at WASP-76b can reach 4,400 F (or 2,246 C) during the day. However, this might be an underestimate if the temperature profile is more accurate.

Astrophysicist Emily Deibert, from the University of Toronto in Canada, says that "we're seeing so many calcium; it's really strong feature." This spectral signature of ionized Calcium could indicate that the exoplanet's upper atmosphere winds are very strong or that the atmospheric temperature is much higher than we thought.

WASP-76b was discovered in 2016. It is also known as a hot Jupiter' exoplanet. Because it orbits its star so closely, the orbit takes only 1.8 Earth days. It is approximately 640 light years from our position in Universe. It is also tidally locked which means that the same side faces its star. This makes it slightly warmer than our Sun.

The researchers used data from Hawaii's Gemini North Telescope to examine the moderate temperature zone, which is the boundary between day and night. Transit spectroscopy is where the star of an exoplanet shines through the atmosphere and back to Earth.

We can make calculations about the atmosphere at different depths based on the quality and composition of this light. The team was able identify rare trio of spectral line readings, which indicate the presence ionized calcium.

Ray Jayawardhana, an astronomer at Cornell University in New York, says, "It's amazing that with today's telescopes, instruments, we can already learn so many about the atmospheres their constituents. Physical properties. And even large-scale wind patterns for planets that orbit stars hundreds of light years away."

Astronomers can discover all sorts of secrets about exoplanets hundreds (or more) of light-years away using spectroscopy techniques like the one used here. This includes everything from details of the planet’s rotation to wind patterns on its surface.

Researchers can now group these exoplanets for easy reference as they are being discovered and catalogued more often. We learn more about the Universe and other forms of life.

This is part of a multiyear project that examines at least 30 exoplanets. It's called Exoplanets with Gemini Spectroscopy. Experts should be able to better understand the variety of atmospheres on these exotic and distant worlds once the project is over.

Jayawardhana says, "As we perform remote sensing on dozens of exoplanets that span a range in masses and temperatures we will get a better picture of the true variety of alien worlds, from those hot enough for iron rain to those with more moderate climates, to those heavier than Jupiter to those not much larger than the Earth."

The Astrophysical Journal Letters published the research.