JAKARTA – So far, astronomers have known that the brightest object in the night sky is the planet Venus, but this fact has been refuted by the discovery of a new exoplanet.
Venus itself has a thick layer of clouds that reflect about 75 percent of the sun’s light. In comparison, Earth only reflects about 30 percent of incoming sunlight.
Now for the first time, astronomers have discovered an exoplanet that can match Venus’ luminosity, namely Planet LTT9779 b.
New detailed measurements made thanks to the European Space Agency’s (ESA) Cheops mission, revealed the planet is capable of reflecting 80 percent of the light shining on its parent star.
The fraction of light that is reflected by an object is called its albedo. Most planets have low albedo, either because they have atmospheres that absorb a lot of light, or because their surfaces are dark or rough.
The high albedo of LTT9779 b is surprising, because the side of the planet facing its star is estimated to be around 2000 degrees Celsius.
Any temperature above 100 degrees Celsius is too hot to form water clouds, but the temperature of the planet’s atmosphere should be too hot for clouds made of metal or glass.
Being shiny isn’t the only surprising thing about the LTT9779 b. Its size and temperature have earned it the nickname ‘very hot Neptune’, but no other planet of this size and mass has been found orbiting so close to its star.
This means that the planet lives in what is known as the hot desert of Neptune. The planet has a radius 4.7 times that of Earth, and a year on LTT9779 b takes only 19 hours.
To determine the properties of LTT9779 b, the ESA’s exoplanet characterization Cheops mission observed it as it moved behind its parent star. This research has been published in the journal Astronomy & Astrophysics.
Because planets reflect light, the star and planet combined send more light to Cheops just before the planet becomes invisible than after.
The difference in visible light received just before and after a planet is hidden tells astronomers how much light the planet reflects.
“LTT9779 b is an ideal target for follow-up to the extraordinary capabilities of the Hubble and James Webb space telescopes,” said ESA operations science scientist Emily Rickman in a statement quoted Wednesday, July 12.
“They will allow us to explore this exoplanet with a wider range of wavelengths including infrared and UV light to better understand the composition of its atmosphere.”
Tags: outer space planets solar system
2023-07-12 16:30:00
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