NASA discovers KELT-9b, a large, boiling and strange planet with four seasons and a 36-hour year

Astronomers have modeled one of the hottest and strangest planets known using measurements from NASA’s planet-hunting Exoplanet Reconnaissance (TESS) mission.

The previously discovered planet, known as KELT-9 by HD 195689 b, is approximately twice the size of Jupiter and has a daytime temperature reaching around 7,800º Fahrenheit / 4,300º Celsius, which is hotter than the surfaces of some stars. .

It is so large that it is believed to be on the cusp between being a planet and a star.

It is so hot that its atmosphere certainly evaporates into space.

“The rarity factor is high with KELT-9b,” said John Ahlers, an astronomer at the Universities Space Research Association in Columbia, Maryland, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It is a giant planet in a very close, almost polar, orbit around a rapidly rotating star, and these characteristics complicate our ability to understand the star and its effects on the planet.”

Scientists’ findings on KELT-9b are published this week in The astronomical diary.

What and where is KELT-9 b?

It is a giant (very) “hot Jupiter” planet that orbits a star about 670 light years away.

If you’re like me, you’ll want to know where it is before learning a lot about it. Although it is just out of sight with the naked eye, it is very close to the bright star Sadr in the center of the Northern Cross in the constellation Cygnus, the swan. That is easily seen in the summer night skies of the northern hemisphere: high in the eastern sky comes darkness.

What’s strange about KELT-9 b?

It is not just ultra hot. This is what is happening in KELT-9 b:

• It is a giant gas world approximately 1.8 times larger than Jupiter, with 2.9 times its mass.
• It always shows the same side of its star, just as the Moon does to Earth.
• It orbits its star in just 36 hours and travels directly over the star’s two poles.
• It receives 44,000 times more energy from its star than Earth from the Sun.
• Every 36 hours, KELT-9 b experiences two summers and two winters, with each season approximately nine hours.

Why is KELT-9 b so hot?

The star has hot poles and a cold equator, which means that during a single 36-hour orbit, one year, the planet KELT-9 b undergoes two cycles of heating and cooling. That means a summer when the planet faces the star’s pole and a winter when it faces the star’s equator. The result is that KELT-9 b experiences two summers and two winters every 36 hours.

What do we know about the host star?

It is a rather strange star:

• It is about twice the size of the Sun.
• It is 56 percent hotter than the sun.
• It spins 38 times faster than the Sun, spinning once every 16 hours.
• That very high speed makes it fat around the equator, giving it an oblate spheroid shape, which means hot poles and a cold medium, hence the strange seasons of the planet.

That oblate spheroid shape is something that has also been observed in the star Achernar in the constellation Eridanus:

What is ‘gravity darkening’?

It is what is happening in this star system, and what creates the stations in KELT-9 b. The rapid spin of the star distorts the shape of the star, flattening it at the poles and widening its equator. This causes the star’s poles to heat up and light up as its equatorial region cools and dims. This darkening of gravity or the brightness of gravity is what is really interesting for scientists.

“Of the planetary systems we have studied using gravity darkening, the effects on KELT-9b are by far the most spectacular,” said Jason Barnes, professor of physics at the University of Idaho and co-author of the article. . “This work goes a long way in unifying the darkening of gravity with other techniques that measure planetary alignment, which in the end we hope to uncover secrets about the formation and evolutionary history of planets around high-mass stars.”

How do we know about KELT-9 b?

TESS finds planets by studying the brightness of the stars using the transit method. Every time a planet passes in front of its parent star, the brightness of that star decreases slightly. By taking measurements, the presence of a star can be inferred. Transits from the planet KELT-9 b were first observed by the KELT traffic survey, which collected observations from two robotic telescopes located in Arizona and South Africa.

However, TESS studied KELP-9b between July and September last year and saw 27 transits of KELT-9b, which allowed scientists to model the star and its strange impact on the planet.

It is further proof that the search for exoplanets was not alone it has to be about searching for “another Earth” or an “Earth 2.0”.

Wishing you clear skies and wide eyes.