In today’s episode we take a look a the hot planet Kelt-9b that is getting super-heated by its super-hot star, and examine how a white dwarf – brown dwarf binary periodically goes boom. We also note that the US House is proposing a bill to change all NASA’s human exploration plans to repoint them at Mars.
Today’s news starts with an update on Pamela’s favorite exoplanet: Kelt-9b. This hottest of hot Jupiters orbits a blue star – roughly an A0 or B9.5 star, that may be the largest and hottest star found to have a planet. Because Kelt-9 is so big and bright, we only have the ability to spot very large planets on very small orbits. The planet Kelt-9b is 2.9 times the mass of Jupiter, and has an orbit 10% the size of Mercury’s orbit, and circles in under 1.5 days. It should also be tidally locked, such that the same face of the planet is always looking toward its star.
This super-hot star is able to heat the day-side surface of this super close planet to 7800 degrees Fahrenheit (4300 degrees Celsius). This temperature is cooler than the surface of our Sun, but is still hotter than the surface of many different stars. The everyday material that planets are made of aren’t entirely solid at this kind of a temperature, and this has significant effects on Kelt-9b’s possible geology.
In a new paper in the Astrophysical Journal, a multi-institutional research team has looked at how these kinds of temperatures can break molecular bonds and how this heat drives atmospheric circulation. This paper, with first author Megan Mansfield, uses Spitzer Space Telescope data to look at how the world’s temperature varies around the world.
According to the paper, the hotter the planet, the faster the heat redistribution. Put a different way, there are massive winds and other processes that drive heat away from the noon position on the Kelt-9b.
If there were no other effects at play, Kelt-9b’s massive winds could reach speeds of 37 miles or 60 km per second. Luckily there are other factors at play. Some of that energy goes into breaking up molecules instead of generating winds. On the planet’s day side, molecules with two Hydrogen atoms – H2 – are disassociated, and those individual atoms can only come back together if they make it to the world’s other side – the nightside. Since these atoms are the lightest of all atoms, collisions with more massive atoms can send them flying at escape velocities. Were we close enough to study it better, we might see material streaming out behind this planet as gas is driven from its atmosphere. Also driven into excited states are neutral and ionized iron and ionized titanium in this planet’s atmosphere.
Kelt-9b is a little less than 3 Jupiter Masses in size, and is puffed out to roughly 2 Jupiter diameters. This massive size means this world isn’t going to get blown apart anytime soon, but it is going to slowly shrink slowly. It’s host star, which is several solar masses in size, will eventually bloat up into a red giant and consume whatever is left of this world. In what is one of our favorite statements to appear in a press release, this broiled planet “will stay firmly categorized among the uninhabitable worlds.”
In case you hadn’t already figured it out, our universe is a violent place, where we see star-eat-planet and even star-eat-star scenarios all across the sky.
In new results from the Kepler data that are published in the Monthly Notices of the Royal Astronomical Society, astronomers, working with lead author R Ridden-Harper, find that a hungry white dwarf star may be chowing down on a nearby brown dwarf.
Brown dwarfs are odd objects that aren’t quite planets, and aren’t really stars. With masses between 10 and 80 times the mass of Jupiter, some brown dwarfs will undergo short lived nuclear burning of tritium – heavy hydrogen atoms with a surplus of neutrons. This particular brown dwarf orbits a white dwarf star so closely that the white dwarf star’s extreme gravity can tear material off the brown dwarfs surface. When the region around the white dwarf gets too bloated with material, that material can explode, creating a brilliant outburst we call a cataclysmic variable outburst. Only 100 systems of this particular combination – a white dwarf and brown dwarf – are known.
These outburst events are brief, and by luck Kepler just happened to be looking at this system in the lead up to and during a 2016 event that is being classified as a super-outburst. According to the press release, “Kepler captured the entire event, observing a slow rise in brightness followed by a rapid intensification. While the sudden brightening is predicted by theories, the cause of the slow start remains a mystery. Standard theories of accretion disk physics don’t predict this phenomenon, which has subsequently been observed in two other dwarf nova super-outbursts.”
These two papers both use the data from retired spacecraft, and show us that even when a mission is retired, their freely available data are able to keep generating new science. The trick is, you have to have the mission to get the data to make the science.
The funding for Spitzer and Kepler, and all other US missions, is determined by NASA, and as happens every year, mission teams are eagerly waiting to see what kind of a spending bill and policy directive comes out of the US Congress. Funding bills are proposed by the president, rewritten by the house, and further edited by the senate before they ever get passed. On Friday, the US House of Representatives released HR 5666, a bill that takes everything the president and VP planned and throws it out an airlock. If passed, this plan will kill off the Artemis Program’s fast pass to the moon, as dictated by VP Pence, and mandate NASA plans for Mars instead of the Moon. It also relies on Boeing and the Space Launch System.
The Commercial Spaceflight Federation issued a Sunday night statement: “As written, the NASA Authorization bill would not create a sustainable space exploration architecture and would instead set NASA up for failure by eliminating commercial participation and competition in key programs. As NASA and the White House have repeatedly stated, any sustainable space exploration effort must bring together the best of government and commercial industry to achieve a safe and affordable 21st century space enterprise.”
So far this is just a proposed bill. It still needs to be voted on.
This is your friendly reminder that we have the ability to sway the opinions of our congress critters, and if you want to see a different future from NASA, it’s time to pick up your phone and make some calls. Dream big, and dream sustainable.
And that rounds out our show for today.
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