ASTRONOMY IS FUN
Blanet, the Possibility to Find a Planet around the Black Hole
The scientific explanation of Miller’s Planet and Black Hole in the Interstellar film
In the last decade, the black hole became a hot topic to be discussed. After astronomers worldwide announced their first-ever picture of a black hole in 2019, The Royal Swedish Academy of Sciences awarded astronomers for their discovery about the black hole a year later. Roger Penrose builds the theory, while Reinhard Genzel and Andrea Ghez work in the observational.
People can understand a black hole in a simple by watching a science fiction film, Interstellar. Christopher Nolan produces it. He collaborates with a senior cosmologist, Kip Thorne as a scientific consultant. Interstellar was awarded as the Best Visual Effects at the 87th Academy Awards in 2014.
Interstellar says that the Earth will be inhabitable because of the lack of oxygen and food shortages. Most of the people are farmers. But, it will not be last long as devastating sandstorms ravage the crops. One of the best solutions to survive is finding a new habitable planet outside the Solar System.
Astronomers from NASA had researched three candidates exoplanet, Miller’s planet, Edmunds’s planet, and Mann’s planet. We will focus on Miller’s planet, a planet that orbits a Gargantua. We define Gargantua as a spinning, supermassive black hole (SMBH).
It is a tough case where a planet can orbit a Gargantua. A Gargantua has a powerful gravitational force so that planets or stars will be captured if they are close enough and has a small velocity to balance the gravity from Gargantua. But, it will be a different case if the planet is formed in the dynamics of Gargantua, as shown in Miller’s planet. It is not science fiction without a strong fundamental.
Theoretically, the formation of a blanet (black hole planet) is explained by Wada et al., 2019 (hereafter: Wada19). A Gargantua with active nuclei is called Active Galactic Nuclei (AGN), which can have a circumnuclear disk composed of gas and dust, as shown in Figure 1. The dusty gas around Gargantua can extend beyond the sublimation (T~1500 K) and snow radius (T ≤100K). In circumnuclear disks around SMBHs, the dust and grains are qualitatively similar to those of protoplanetary disks.
One of the most common theories about planetary formation stated that a planet is formed from the protoplanetary disk within the parental star’s nebula. The disk is composed of dust and grains, called planetesimal. A small planetesimal grows in the beginning process, becoming a larger one from the gravitational force. After that, the primary factor that drives larger planetesimal becomes protoplanet is a collision. Wada19 simulate the circumnuclear disk of Gargantua with the same dynamics of the protoplanetary disk.
After deriving some equations, Wada19 found Earth-sized bodies can be formed outside the snow radius (Rsnow), about several parsecs from the Gargantua in low-luminosity AGN. The growth timescale of a blanet depends on the turbulent strength of the Gargantua, about 100 million years (comparable with AGN’s lifetime) for low mass SMBH (1 million of Sun’s mass).
A blanet will not grow if the collision’s critical velocity is larger than a limit to form a larger planetesimal. If the velocity is larger than the limit, the collision between two planetesimal will destroy them.
If we elaborate on the result, we could find a blanet in the center of the Milky Way. As you know, the Milky Way has an SMBH, named SgrA*, with a mass of about 4 million of Sun’s mass. Furthermore, it is a dormant SMBH, not an AGN. So, the possibility of finding a blanet is stronger, theoretically. But, observing planets around SMBH should need a big effort. To observe an S-star that orbit SgrA*, astronomers need a piece of special equipment such as adaptive optics.
If you are interested in observing the stars in the winter, you need to read the introduction about winter’s stars.
To visualize the Earth’s rotation, you can try this time lapse methods
That’s all. Thank you and have a good day.
References
- National Geographic, 2019. First Picture of a Black Hole. https://www.nationalgeographic.com/science/2019/04/first-picture-black-hole-revealed-m87-event-horizon-telescope-astrophysics/
- Gillessen, S., et al. 2009. Monitoring Stellar Orbits around the Massive Black Hole in the Galactic Center. https://iopscience.iop.org/article/10.1088/0004-637X/692/2/1075/pdf
- Ghez, A. M., et al. 2008. Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits. https://iopscience.iop.org/article/10.1086/592738/pdf
- Wikipedia. Interstellar (film). https://en.wikipedia.org/wiki/Interstellar_%28film%29
- Wada, K., et al. 2019. Planet Formation around Supermassive Black Holes in the Active Galactic Nuclei. https://iopscience.iop.org/article/10.3847/1538-4357/ab4cf0/pdf
- Wikipedia. Protoplanetary disk. https://en.wikipedia.org/wiki/Protoplanetary_disk
