It’s Getting Hot on Jupiter

Observations with the Subaru Telescope, a Japanese 8-m telescope on Mauna Kea, Hawaii, show that the aurorae at Jupiter’s poles are heating the atmosphere of the gas giant, and that it is a rapid response to the solar wind.

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Aurorae at Earth’s poles occur when the energetic particles blown out from the Sun, the solar wind, interact with and heat up the gases in the upper atmosphere.

The same thing happens at Jupiter, but the new observations show the heating goes 2-3 times deeper down into its atmosphere than on Earth, into the lower level of Jupiter’s stratosphere (upper atmosphere).

Understanding how the Sun’s outpouring of solar wind interacts with planetary environments is key to better understanding the nature of how planets and their atmospheres evolve.

What is startling about the results is that scientists were able to associate the variations in the solar wind and the response in Jupiter’s stratosphere, and that the response to these variations is so quick for such a large area.

Within a day of the solar wind hitting Jupiter, the chemistry in its atmosphere changed and its temperature rose, the astronomers found.

Such heating and chemical reactions may tell us something about other planets with harsh environments, and even early Earth.

The results appear in the journal Nature Astronomy.

The First Pic of a Black Hole

Scientists from a global collaboration of telescopes announced Wednesday that they have captured the first-ever photo of a black hole.

The collaboration, called the Event Horizon Telescope, is a global network of eight telescopes that has been working for two years to capture the first image of a black hole, by combining data from the eight telescopes and “creating a virtual Earth-sized telescope.”

“We have seen what we thought was unseeable,” Shep Doeleman, the director of the EHT, said during a news conference Wednesday.

In 2017, the group embarked on a week long observation spanning telescopes in four continents, capturing data from two black holes: one in Sagittarius A*, located at the center of the Milky Way galaxy, and the other in the Messier 87 galaxy, in the constellation Virgo.

MIT’s Katie Bouman with the hard drives used to store the black hole image data. 

The Fate of the Earth

If it weren’t for the sun constantly showering us with energy, there would be no life on Earth. But eventually the sun will run out of fuel, expand into a red giant and finally collapse into faint, white dwarf. What will happen to us and the other planets in the solar system when the sun dies? It’s not entirely clear.

Scientists think that they have spotted the possible core remnant of a planet orbiting the white dwarf SDSSJ122859.93+104032.9, residing some 410 light years away. The results, published in Science, offer important clues about the fate of the planets in our solar system.

The planetary fragment produced a stream of gas that could be detected by spectrometers. Researchers spotted it orbiting the star by looking at how its spectrum shifted in color as the body moved towards and away from Earth. This change in color is called a doppler shift, which is essentially a stretching or squashing of waves because of motion. It is similar to the pitch of the sound of an ambulance being higher when it is heading towards you, and lower when it is moving away.

The object completed one passage around its host star in just over two hours, orbiting at a distance that is smaller than the radius of the sun in a disc of gas and dust.

The discovery is surprising, since scientists didn’t think anything could survive so close to a white dwarf. A white dwarf is only about the size of the Earth but it contains around 60-70% of the sun’s mass, making it extremely dense. If a body orbits too close to a white dwarf, its immense gravity will rip it apart. This was likely the fate of the material that formed the disc around it.

So how did this object survive without getting ripped apart? It would have to either be very dense itself or have some amount of internal strength holding it together. Scientists calculated that it has a maximum diameter of 720km, which is the size of a small minor planet. The dwarf planet Ceres in our solar system has a diameter of 946km by comparison.

The origin of this object remains a mystery. One possibility is that this is the core of a minor planet that was pushed close to the white dwarf by a larger planet further out in the remnant planetary system, like a Jupiter. As the minor planet passed close to the white dwarf, its crust and mantle layers would have been ripped away.

All that would be left of the planet would be its dense, iron-dominated core. This kind of object is quite common, with one famous resident in our own solar system: the asteroid 16-Psyche.

Systems such as the one just discovered can help us understand the future of our own planetary system. In about five billion years, the sun will start to expand into a red giant. At this point, it will engulf Mercury, Venus and most likely Earth, unless we manage to move our planet into a wider orbit, which should be possible in theory. However, Mars, the asteroid belt and the rest of the solar system will survive engulfment and continue orbiting the sun as it then collapses into a white dwarf.

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During this process, planets like Jupiter could also scatter asteroids, comets or even minor planets towards the white dwarf. There they would undergo partial or complete disruption, forming a disc like the one just discovered. It is unlikely that any living organisms on planetary or moon fragments could survive this process. Even if they did, they would struggle to live on in the faint light of a white dwarf.

This is not only the solar system’s fate, but that of practically all known exoplanet systems. In the much much closer future, scientists hope to find more planetary bodies around other white dwarfs. There are six candidate white dwarfs that are orbited by discs made of dust and gas, and researches want to test whether these discs are the “smoking gun” for the presence of minor planets. The more such planets are found, the more that can be learned about what happens to a planetary system as its star dies.

Curiosity Catches Two Eclipses

The cameras on NASA’s Curiosity rover usually look down at the rocks on Mars, divining clues in the minerals of what the planet was like billions of years ago.

Sometimes though, the rover also looks up, and in March it spotted two eclipses (eclipsi?).

Eclipses on Mars are not as total as those on Earth where the moon completely blots out the sun. The two moons of Mars are tiny. Phobos is 7 miles wide while Deimos is even tinier, just 1.5 miles in diameter. They only partially block the sun when they pass in front of it.

The camera on Curiosity’s mast is equipped with solar filters that allow it to look directly at the sun and photograph eclipses. On March 17, Curiosity observed Demios eclipsing the sun. Nine days later, it also spotted Phobos passing in front.

The observations by Curiosity, and by earlier NASA Mars rovers, Spirit and Opportunity, enable more precise pinpointing of the moons’ orbits, which are jostled around by the gravity of Mars, Jupiter, and even each other.

Although Phobos and Deimos are small, the details of their formation are of considerable scientific interest. Japan’s space agency plans to send a spacecraft to the two moons within the next decade. The Mars Moon Exploration probe, or MMX, will collect samples and return them to Earth for study. A panel of scientific experts recently approved the sample-return phase of the mission.

Tremors on Mars

Since NASA’s InSight lander, um landed on Mars at the end of last year, the plucky surface probe has spent months getting carefully situated so that its special seismometer could listen for “marsquakes” a neologism for earthquakes that occur on Mars, rather than Earth, as you probably guessed.

Observations of marsquakes will help determine just what’s going on inside of Mars, and to what extent it is still a geologically active world. We know Mars was very geologically active in the past; it has the tallest mountain of any planet in the solar system.

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While InSight hasn’t heard mars-shaking marsquakes yet, Scientists have revealed that the lander’s instrument has detected a different kind of rumbling known as microseisms. They are the first of their kind to be detected on another planet.

The new noises are caused by low-frequency pressure waves from atmospheric winds. On Earth, microseisms are caused by the ocean, storms and tides. Researchers working on InSight hope to hear a real marsquake within one month.

InSight’s other instruments have been providing scientists with troves of data. Indeed, since mid-February, InSight has issuing weather reports from Mars.

Ultimately, InSight’s science will help contribute to an overall picture of the history of the solar system, and how Mars, Earth and the other planets formed and evolved. The Auxiliary Payload Subsystem (APSS) lets InSight provide more frequent weather information than any previous mission to Mars.

InSight’s science will help contribute to an overall picture of the history of the solar system, and how Mars, Earth, and the other planets formed and evolved.