The Hubble telescope has just passed its 30th anniversary. In the past 30 years, it has been keeping an eye on the deep universe and taking images of galaxies and nebulae light years away. But even if it wasn’t designed for another mission, did you know that Hubble is actually looking at objects closer to home – just inside the solar system? And precisely because it does, it allows us to observe these planets and the surrounding space in a timely and efficient manner, otherwise we may miss some phenomena when preparing for special missions. I’m Alex Colgan, and you’re watching Astrum, and in this issue of the Hubble Space Imaging exhibition, we’re going to explore once again some of the spectacular things that happen in the solar system as observed by the Hubble telescope.
item 55, “hippocampus”. Neptune and Uranus, the two distant planets covered with ice, seem to have been forgotten by space agencies around the world. Only in 1989 did Voyager 2 make a close flyby. This means that we still know very little about these two giant planets. If it wasn’t for the occasional observation of Hubble, we would have been even stranger to them. With regard to Neptune, one of Hubble’s major discoveries was the discovery of a new satellite, named “hippocampus,” in 2013. Hubble has discovered many moons, especially those of Jupiter and Saturn, but Triton is special in that it may be a fragment of the larger moon Titan.
indeed, the 400 km diameter Triton experienced a period of turbulence, with some impact craters with a diameter of 50-100 km. It is likely that one of these impacts caused a part of Triton to break apart, leaving debris in orbit around Neptune. Because Triton’s irregular shape, about 35 kilometers in diameter, and its orbit is also close to the larger Enceladus, it is speculated that Triton is probably the largest fragment among them.
so let’s take a look at item 56, because it’s about Neptune itself. As I mentioned earlier, Hubble was not designed to observe the solar system, but in 2015, experts decided to let Hubble spend more time observing distant planets, about once a year. This means that we can better observe the annual changes in the atmospheres of these planets. One significant change is the giant storms that span thousands of kilometers. In 1989, Voyager 2 observed a storm similar to Jupiter’s “great red spot,” so we later called it the “great dark spot.”. Unlike the big red spot, however, Neptune’s big dark spot has disappeared since then. Then other storms came up and disappeared.
the one observed took place in 2015, which lasted for several years, but then disappeared. Although there is not enough data to infer how these vortices are formed, one assumption is that Neptune’s atmosphere is composed of zonal regions like Jupiter’s. although it may be different from that on Jupiter and the number is not as large as that on Jupiter, the banded clouds still have different velocities, which may lead to vortices at the junction. Once the storm forms and begins to move, it can flow along the planet’s surface, even between the zonal regions. But once it leaves the energy source, it starts to die out, and that’s what we see. Interestingly, the Hubble telescope is the only one that can observe these changes, because it is difficult to observe these changes for most of the observed wavelengths, while Hubble can observe Uranus and Neptune in the ultraviolet band.
Figure: VLT images have higher resolution, but Hubble images retain more details
item 57, 2007 or10. If you haven’t heard of it before, it’s the third largest dwarf planet in the solar system, just like Pluto and Eris. And like them, the dwarf planet was found billions of kilometers away in the Kuiper belt. Although it was not discovered by Hubble, Hubble first discovered that it had a satellite. The observers who initially discovered Gonggong star did not find the satellite because it was too dark in the picture. However, a research team later suspected that it had a satellite because the Gonggong star rotates slowly, with a cycle of about 45 hours. Most objects in the Kuiper belt have rotation periods of less than 24 hours.
so scientists assume that the gravity of the satellite may slow down its rotation period. After searching Hubble’s database, this assumption proved to be true. The discovery means that all Kuiper belt dwarf planets have their own moons. This may be because the motion of celestial bodies in the Kuiper belt is very slow. If there is a collision between celestial bodies, the debris generated will enter the orbit around the celestial body itself, rather than escape from the gravitational field of the celestial body. That’s why asteroids in general don’t have high energy in the space. Finding the satellite of the Gonggong satellite means that we can establish better constraints in the existing models describing the formation process of the solar system. This is really valuable information!
item 58, Jupiter’s aurora. It’s not just the earth that has aurora. Although you can occasionally see the aurora with the naked eye on earth, the aurora is actually the strongest in the ultraviolet band! As I mentioned earlier, Hubble’s ability to detect electromagnetic waves in the ultraviolet region means that we can also observe aurora on other planets. Jupiter’s aurora is the easiest to find. Jupiter is the largest and closest gas giant planet. Its strong magnetic field and intense radiation produce very strong aurora. In 2016, Juno, on its way to Jupiter, gave scientists an excellent opportunity to measure the intensity of the solar wind, and Hubble to observe the changes in the aurora. As a result, Hubble observed Jupiter almost every day for several months.
Hubble found that Jupiter’s aurora is hundreds of times stronger than those on earth, with a radiation power of 100 terawatts, and surprisingly, Jupiter’s aurora never stops. On earth, the aurora lights up the earth’s poles only when the solar storm comes. This suggests that Jupiter’s aurora does not just come from the solar wind. After Juno arrived at Jupiter, the data it collected showed that Jupiter’s aurora mainly came from charged particles in Jupiter’s strong radiation belt, which flowed into Jupiter’s atmosphere along magnetic induction lines. At the same time, we also found that Jupiter’s magnetic field will produce AC current instead of DC current, which also explains the radiation energy of Aurora, because it is impossible to generate such strong energy by exchanging energy through DC current.
item 59, Europa. If you didn’t know about this star before, you need to know that Europa is one of Jupiter’s larger moons and one of the most likely objects in the solar system to give birth to life. We don’t want to find anything on the surface of its ice, but underneath it is a vast ocean of liquid water. Europa is a cold world, and very close to Jupiter, leading to strong tidal activity. The theory is that this tidal activity produces enough energy to keep the ice ocean liquid. So experts have set up a number of research projects to confirm the existence of this kind of subglacial ocean. And happily, the Hubble telescope has been very helpful in this work.
the Galileo and Voyager probes provide higher resolution images of Europa because their flight path is closer to Europa, but they cannot be observed in the ultraviolet band. And Hubble could, and Hubble found a possible sea vent on Europa’s ice surface. This volcanic movement shows that the inner layer of Europa is liquid, and must be liquid water, which also proves the correctness of the theory. Since the first discovery, more jets have been detected. Hubble’s imaging technology could also be used for inorganic salts on Europa’s surface. Most projects use infrared to observe the surface of the planet, because most of the electromagnetic emission bands of matter of interest are concentrated in the infrared band.
However, for sodium chloride or other salts similar to those found in our oceans, it is mainly in the visible light band. This means that the salts on Europa’s surface were not discovered by Galileo. Hubble’s visible light observations confirmed that sodium chloride was found everywhere on Europa’s surface, probably from the ocean below the surface, which was then carried to the surface by upwelling and deposited there. The exciting thing about a salt rich ocean is that it suggests that there may be active thermal activity at the bottom of the ocean. On earth, the hot gas vents of undersea volcanoes are a hotbed of life, so scientists are very excited to explore further, even if it is possible to explore the seabed for decades to see what’s going on.
item 60, Uranus. Much like Jupiter and Neptune, Hubble also found storms on Uranus’s surface and Aurora around Uranus’s magnetic poles. Uranus’s aurora does not occur on its axis. Uranus’s axis of rotation is very strange. Compared with other planets in the solar system, its axis is on its side. This means that Uranus sometimes rolls in its orbit during the year. It also means that eclipses are hard to see on Uranus.
it was only in 2006 that we had the first chance to see such a scene, and the last time Uranus, the moon and the sun were aligned in 1965, when telescope technology could not see satellites passing over such distant objects. Hubble not only saw the projection of Enceladus across the surface of Uranus, but also completely observed the zonal region on the surface of Uranus. Neptune has an 84 year orbit, and Hubble can see the seasonal changes of its atmosphere by observing a part of the equinox. As one of its poles gradually faces the sun, the color of the atmosphere seems to get brighter. The explanation for this phenomenon is that when the hemisphere enters the summer, it will form a huge cloud layer, and it will dissipate near the autumnal equinox. Because Hubble has been in service for only 30 years, so we haven’t even been able to observe half of Uranus in a year, so we still have a lot to learn about the four seasons of Uranus!
picture: Neptune and its satellite arrangement, it is very difficult to have an eclipse
just in this period, you can see how important Hubble is for human beings to understand the solar system and the universe. And in the last 30 years, it has done much more than this. Hubble is probably the most important space exploration project to date. It has broadened our horizons and provided us with data for many years to come. And the good news is that Hubble is likely to work for another 10 to 20 years. I’m looking forward to the great results of the James Webb Space Telescope, but I’m absolutely grateful for Hubble’s achievements, and I’m looking forward to Hubble’s future discoveries!