Podcaster: Richard Drumm
Title: Space Scoop: Footprints of Baby Planets Spotted Around A Young Star
Organization: 365 Days Of Astronomy
Link : astrosphere.org ; http://unawe.org/kids/unawe1610/
Description: Space scoop, news for children
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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Transcript:
This is 365 Days of Astronomy. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Today’s story is: Footprints of Baby Planets Spotted Around A Young Star
It takes nine months for a human baby to grow, 22-months for a much larger baby elephant to grow… but how long does it take to grow a planet? It turns out, it takes much less time than we thought.
Previously, it was believed to take tens of millions of years for a planet to form. But baby planets have just been discovered growing around a young star that is estimated to be only one million years old!
The picture in today’s album artwork shows the young star HL Tauri, 450 light years away in, as you might guess, the northern constellation Taurus. There are 2 images here of HL Tauri, one from 2014 which shows dust, and one from 2016 that shows gas.
What we’re calling dust here is bits of carbon, iron, silicates and the like, things that don’t evaporate like frozen carbon monoxide, while gas is, in this particular case, HCO+. More on that ion in a bit.
The star is surrounded by a ring of cosmic gas and dust called a ‘proto-planetary disc’. These discs are common around young stars and contain all the ingredients for making the planets and moons in a solar system.
In November 2014, scientists discovered two large gaps in the disc around this young star. The image created quite a stir in the astronomical community when it was released, I don’t mind telling you!
The images here were both created using the ALMA, Atacama Large Millimeter/Submillimeter Array of radio telescopes in the very high and very dry Atacama desert of Chile.
In 2014 no one knew for certain what was creating these gaps. Some people (myself included) believed the most likely culprits were baby planets. As young planets grow, they gather up the cosmic gas and dust in their path and create gaps in the disc surrounding them.
However, many other people believed the star was too young to already have planets. More data was needed to solve the mystery once and for all.
We know that the disks around young stars contain gas in addition to the dust. In fact, in general the amount of gas is 100 times larger than that of dust. The astronomers focused on the distribution of gas in the disk to better understand the true nature of the disk since there is more gas than dust there.
If the dust gaps are caused by some variance of the dust’s properties, that wouldn’t directly affect the gas, so no gaps would be seen in the gas distribution.
If on the other hand, the gaps in the dust are caused by the gravity of forming planets, the gravity would be expected to created gaps in the gas as well as the dust. So any gaps that exist in both images are caused by planets sucking up stuff like cosmic vacuum cleaners.
So for the last two years, scientists have been taking detailed pictures of the star and disc. The gas they have been studying is HCO+, the formyl cation, a positively charged gaseous ionic molecule. The central carbon atom in the molecule has a single bond to the hydrogen on one side and a triple bond to the oxygen on the other side.
To many people’s surprise, they’ve found that two of the gaps, at 28 and 69 AU, astronomical units, are indeed the footprints left by baby planets! The gas and dust are both showing gaps at that distance from the star.
But this exciting answer has led to another question – how did these planets form so quickly? Watch this space as we search for the answer. It may, of course, be that the system is older than one million years, that the estimated age is inaccurate, but that’s unlikely.
Hey, Here’s A Cool Fact:
The first gap is about the same distance from its star as Pluto is from our Sun. The second lies almost twice as far away! So we’re seeing the equivalent of the Kuiper Belt in formation at HL Tauri. The gas we see here is almost certainly frozen into ice as well.
The astronomers also detected what they call a “central cavity” inside the inner gap, but they think this is caused by an artifact of the radio emission and not the depletion of the HCO+ gas.
The team also found that the gas density is high enough to harbor an infant planet around the inner 28AU gap. Comparing the structure of the inner gap to theoretical models, the team estimates the planet has a mass 80% times that of Jupiter.
On the other hand, the origin of the outer gap is still unclear. The astronomers suggested the possible existence of a planet 2.1 times more massive than Jupiter, but the present research cannot eliminate the possibility that the gap is made by the drag between the dust particles and the gas.
To solve this question, more data are needed.
Thank you for listening to 365 Days of Astronomy!
End of podcast:
365 Days of Astronomy
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