Starship Asterisk*

Temperatures on Exoplanet WASP-43b

Explanation: A mere 280 light-years from Earth, tidally locked, Jupiter-sized exoplanet WASP-43b orbits its parent star once every 0.8 Earth days. That puts it about 2 million kilometers (less than 1/25th the orbital distance of Mercury) from a small, cool sun. Still, on a dayside always facing its parent star, temperatures approach a torrid 2,500 degrees F as measured at infrared wavelengths by the MIRI instrument on board the James Webb Space Telescope. In this illustration of the hot exoplanet's orbit, Webb measurements also show nightside temperatures remain above 1,000 degrees F. That suggests that strong equatorial winds circulate the dayside atmospheric gases to the nightside before they can completely cool off. Exoplanet WASP-43b is now formally known as Astrolábos, and its K-type parent star has been christened Gnomon. Webb's infrared spectra indicate water vapor is present on the nightside as well as the dayside of the planet, providing information about cloud cover on Astrolábos.

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You'd think at that orbital distance, the parent star would either wick matter from WASP-43b, or cause the orbit to decay until the planet broke apart, or given time, both. I'm no astrophysicist, though..... :' )

Waiting for May the fourth APOD

I assume we have some justification for naming everything in our own solar system. And won’t we quickly run out of Earthly nomenclature to name objects elsewhere? There is also some hubris in our assuming it falls to us to name everything. I doubt the Wasp-43 system has its own intelligent life with naming rights, but maybe there is elsewhere. Some day these aliens may pop up and say ”You named our planets what?!”

I appreciate NASA is an American agency which is beholden to increasing interest in space for Americans but I would appreciate having the courtesy of having conversions to metric units in brackets after the imperial ones, for the benefit of us international readers.

Disgruntled wrote: ↑Fri May 03, 2024 12:14 pm I appreciate NASA is an American agency which is beholden to increasing interest in space for Americans but I would appreciate having the courtesy of having conversions to metric units in brackets after the imperial ones, for the benefit of us international readers.

I agree, especially since the distance is given as "2 million kilometers"!
Luckily, temperatures in Kelvin are shown within the illustration.

Bluemold wrote: ↑Fri May 03, 2024 11:48 am Some day these aliens may pop up and say ”You named our planets what?!”

Or, maybe, they may be amused, or even honoured that we are so interested in their planets!

Bluemold wrote: ↑Fri May 03, 2024 11:48 am I assume we have some justification for naming everything in our own solar system. And won’t we quickly run out of Earthly nomenclature to name objects elsewhere? There is also some hubris in our assuming it falls to us to name everything. I doubt the Wasp-43 system has its own intelligent life with naming rights, but maybe there is elsewhere. Some day these aliens may pop up and say ”You named our planets what?!”

You mean when the aliens arrive here at Glyrkvis 87, which they first observed 13 million years ago?

ylrjr wrote: ↑Fri May 03, 2024 4:58 am You'd think at that orbital distance, the parent star would either wick matter from WASP-43b, or cause the orbit to decay until the planet broke apart, or given time, both. I'm no astrophysicist, though..... :' )

These are small, fairly dense bodies separated by many times their diameters. There are no forces here that would result in mass transfer, or result in orbital decay.

If Astrolabos, aka WASP-42b, is tidally locked then does that mean it possesses no magnetic field?

abaca wrote: ↑Fri May 03, 2024 1:28 pm If Astrolabos, aka WASP-42b, is tidally locked then does that mean it possesses no magnetic field?

With a 19-hour rotation period, I'd think it likely to have a magnetic field.

At that distance the planet must be made of dense rock or be a failed star

The temperatures are 1,250ºC and 600ºC

Temperatures are in F and not K

ylrjr wrote: ↑Fri May 03, 2024 4:58 am You'd think at that orbital distance, the parent star would either wick matter from WASP-43b, or cause the orbit to decay until the planet broke apart, or given time, both. I'm no astrophysicist, though..... :' )

The sizes in the diagram are not to scale. 2 million km is large compared to the sizes of the star (~470,000 km) and planet (~74,000 km).

Disgruntled wrote: ↑Fri May 03, 2024 12:14 pm I appreciate NASA is an American agency which is beholden to increasing interest in space for Americans but I would appreciate having the courtesy of having conversions to metric units in brackets after the imperial ones, for the benefit of us international readers.

I agree. But I also think in this particular context, kelvins would be most useful for getting a feel for these temperatures.

2,500°F ≅ 1,400°C ≅ 1,600 K (red hot)
1,000°F ≅ 540°C ≅ 810 K (just barely glowing in visible light)

Figures are rounded to 2 significant places.

I find it interesting that the trailing side is slightly hotter than the leading side.

Cousin Ricky wrote: ↑Fri May 03, 2024 5:10 pm I find it interesting that the trailing side is slightly hotter than the leading side.

That's what I was wondering. If the planet was rocky, I suppose the temp would be similar to it's present state, except that it would take longer to go from sun-side to dark-side? But that is I guess a moot point since both bodies have been there a long time? The other thought tho is perhaps cold space on the dark-side has less effect on a gaseous body constantly getting quick heat osmosis than a rocky body does? Mercury's rotation is so slow, and it's colder side is very cold, possibly having permanent ice at the poles (or one of them).

Cousin Ricky wrote: ↑Fri May 03, 2024 5:10 pm I find it interesting that the trailing side is slightly hotter than the leading side.

I guess it would require an understanding of how the wind system works. It seems equally likely to me that either edge could be warmer, or that the entire face could be uniform.

Seems like the winds must be unreal on such a system, and judging from the heat retention, the atmosphere pretty darn thick. It would be interesting for someone to make a stab at modeling such extreme conditions!

wilddouglascounty wrote: ↑Fri May 03, 2024 8:03 pm Seems like the winds must be unreal on such a system, and judging from the heat retention, the atmosphere pretty darn thick. It would be interesting for someone to make a stab at modeling such extreme conditions!

The last link says the winds are 5,000 mph!

zendae wrote: ↑Fri May 03, 2024 5:21 pm

Cousin Ricky wrote: ↑Fri May 03, 2024 5:10 pm I find it interesting that the trailing side is slightly hotter than the leading side.

That's what I was wondering. If the planet was rocky, I suppose the temp would be similar to it's present state, except that it would take longer to go from sun-side to dark-side? But that is I guess a moot point since both bodies have been there a long time? The other thought tho is perhaps cold space on the dark-side has less effect on a gaseous body constantly getting quick heat osmosis than a rocky body does? Mercury's rotation is so slow, and it's colder side is very cold, possibly having permanent ice at the poles (or one of them).

The planet's mass is 1.8 Jupiters, so it has to be a gas giant, and in this case it is deemed a "hot Jupiter".

Disgruntled wrote: ↑Fri May 03, 2024 12:14 pm I appreciate NASA is an American agency which is beholden to increasing interest in space for Americans but I would appreciate having the courtesy of having conversions to metric units in brackets after the imperial ones, for the benefit of us international readers.

Ja natuerlich. 280 light years ist 9.4608 x 10^12 kilometer. Bitteschoen. (Can’t do umlauts on the laptop.)

Roy wrote: ↑Fri May 03, 2024 11:30 pm

Disgruntled wrote: ↑Fri May 03, 2024 12:14 pm I appreciate NASA is an American agency which is beholden to increasing interest in space for Americans but I would appreciate having the courtesy of having conversions to metric units in brackets after the imperial ones, for the benefit of us international readers.

Ja natuerlich. 280 light years ist 9.4608 x 10^12 kilometer. Bitteschoen. (Can’t do umlauts on the laptop.)

The light-year is not an imperial unit. They were talking about Fahrenheit. "Today, the United States, the Bahamas, the Cayman Islands, Palau, the Federated States of Micronesia and the Marshall Islands are the only countries that exclusively use Fahrenheit temperatures. Some other nations use both systems, including Belize, the British Virgin Islands, and Bermuda." Everyone else uses °Celsius. NASA actually uses the metric system for decades now. Including °Celcius. But they have to convert everything in Fahrenheit, Inch and Miles for the American public.

Well, OK, temperature is based on molecular motion. The scale we use is based on some earthbound feature at sea level & 1 atmosphere plus desire for decimalization.

What is really fascinating is : how do we know what is going on so far away, and what does that imply about how the system formed? There are so many double star systems. A K star is not as bright as the sun, but would it have permitted a dust cloud big enough to condense a super sized Jupiter so close as to orbit in 18 hours?