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For the first time, astronomers witnessed the birth of a giant planet while it still exists! We saw young planets, and stars before their planets were born, and even while planets were forming, but never before there were clear observations of the planet itself . 19659002] To see why it's so cool, you need a bit of a background.
The star is called PDS 70, and is located about 370 light-years away. This is part of a group of very young stars called the Scorpius-Centaurus Association, many of which are still forming, and is the group closest to us in the galaxy.
The star itself is about 5.4 million so it is very young (the Sun is 4.6 years old billion ). Because he's young, his physical characteristics are a little odd. In general, stars of the same age but less massive than the Sun are also smaller; however, while the PDS 70 has only 0.76 times the mass of the Sun, it is 1.25 times wider. It is however much less bright, shines only about 1/3 of the energy emitted by the Sun.
The observations of 2002 show that it is surrounded by a disc of matter, sign of youth. Stars form from clouds of gas and dust that collapse due to an outside influence (maybe two clouds collide, or the wind blows). a nearby massive star exerts pressure on it). As a cloud collapses, random swirls are amplified and the cloud flattens into a disk. Eventually, when the star in formation (called a protostar) "lights up" – the nuclear fusion is triggered in that nucleus – it becomes a correct star, and its light and wind sweep away the remnants of the disc she is formed.
But this skips an important step: planetary formation. While the details of the process are still being processed (give astronomers a break here: we've only had good data on this topic for a few years!), Basically small grains of material from the disc, which are developing and stick with others. They grow, become larger grains, then pebbles, then rocks, then rocks, then … well, you see the picture. When they reach a few hundred kilometers, we call them protoplanets, and gravity takes over, actively attracting the material. Finally, a planet is born.
Or so we suppose. We have seen indirect evidence of this, many times, on records. For example, some disks have gaps, which makes sense if there is a planet that is formed there. He sculpts the gap as he eats material in the disc. We have also seen other indications of planets, but never the planet in formation itself (at least until the training process is completed).
Until now. The new planet * called PDS 70b, can be seen directly in the images taken using SPHERE, a powerful camera on the Very Large Telescope in Chile. It can measure polarized light, which is the light where the wavelengths are all aligned in one way. The light of a star is not usually polarized, but it is when it is reflected by a dusty disc. By adjusting their observations, astronomers can accentuate the material in the weak disc while suppressing much brighter starlight. They also observed PDS 70 in infrared light, which helps too. A hot disc emits more IR light, while a star generally emits less. This increases the contrast.
In these images, a point source appears immediately. The analysis of the source indicates that it is probably not a random cluster or disk element (it is not polarized as the disk would be), but rather of a massive substellar object: a planet. Given the age of the star (and the assumption that the planet is younger than the star), this planet is still forming!
There is more evidence of this. For example, the planet is very red, which makes sense only if there is still a lot of hot material around. This material would be the substance of the record that he always draws actively.
The planet is about 3.3 billion kilometers from the star, about 22 times farther than the Earth from the Sun, roughly at the distance of Uranus from the Sun. One would think that it would be cold, but in fact it is very hot! Remember, it is still forming, pulling huge amounts of disc material. This trick hits the planet and warms it up (think of it as billions of meteorite impacts), so it is somewhere between around 750 and 1350 ° C. That 's why it' s seen in the world. infrared; Objects at this temperature shine strongly in IR
The size of the planet is between 1.4 and 3.4 times that of Jupiter (a size towards the lower end is more likely), and has a mass between five and twelve times that of Jupiter. The range is large because it is difficult to determine these characteristics. Astronomers measure the colors of the planet using different filters, then compare the colors you expect using physical models of what the planets should look like based on different parameters (mass, temperature, etc.). Age, etc.). Only a few colors were measured for PDS 70b, not enough to properly separate model predictions.
However, one thing that they have found is that a purely thermal model of the planet does not fit the data. In other words, a hot piece of stuff sitting there would not produce the colors they see; you must add clouds of materials in the atmosphere of the planet to match the observations! It is unclear what these clouds would be made of – there is an intriguing feature that implies the presence of water, but it's pretty shady – but they seem to exist.
Unbelievable. This planet is located at 3.7 quadrillion kilometers and it is very hot, but it can be said that it has a partly cloudy day.
I love astronomy.
point that I found fascinating. The disk around the star extends over a distance of more than 15 billion kilometers (this is far from the distance of Neptune from the Sun). According to some data, there would be an internal disk extending from the star to about 2.5 billion kilometers, but there would be a large gap of more than eight billion kilometers, ostensibly carved by the planet . But the planet is on the inner edge of this disc, not in the middle as you might expect. I guess it's because the planet is migrating inward, toward the star. As it shoots material from the disc, the overall effect is that the planet loses orbital energy by drag, so that it falls to the star.
It was a process we did not really know until recently. The first planets discovered were large gaseous giants the size of Jupiter very close to their stars (called "hot Jupiter" for this reason). It is pretty clear that they can not train so close, so they must be trained further and move inward. We think the gaseous giants of our solar system have also migrated in the early days. And here we see PDS 70b on the inner edge of his disk, too. Hmmmm
All this is incredible. We had no knowledge of any planet apart from ours until 1992, and we have now confirmed the existence of nearly 4,000 exoplanets. The first discs around other stars were detected in the 1980s, and we did not start to get clear pictures until the 1990s. We started to see structures involving planets there. .. and now we are here. An image of a newborn baby planet! Hot and gassy and still growing, and we do not know what his future holds, but then, it's a baby .
Did I mention that I love astronomy? The fact that we can do these things, that we can even think about doing these things, will never stop stunting me. And all because scientists want to know things.
* Heh. In general, when I write on a new planet, I mean new to us. In this case, it's really new.
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