Hello Powehi

Sleep At Last (from: Youtube)

In the center of the galaxy M87, stars seem to orbit an invisible object. By observing the path of the stars, scientists concluded that there is a supermassive black hole that is dense enough to cause these motions. Although the black hole itself is invisible, we can still observe the ring of light bended by the gravitational lensing. A telescope of the size of the Earth is needed in order to take a picture of the light 55 million light years away, but scientists managed to combine images taken from eight observatories around the globe.

Eight radio observatories teamed up in 2017 to work together as a global telescope, called the Event Horizon Telescope network. (from: Science News)

As the Earth rotates, telescopes in these locations are able to observe different part of the image. The researchers then developed imaging algorithms that can fill in the missing gaps in the measurements, “just as a forensic sketch artist uses limited descriptions to piece together a picture using their knowledge of face structure. (How to take a picture of a black hole-Katie Bouman)”

On April 10th, the first picture of a black hole was finally released by the Event Horizon Telescope team. This supermassive black hole 6.5 billion times more massive than the Sun was named Powehi (Po-veh-hee), which refers to “the adorned fathomless dark creation” or “embellished dark source of unending creation.” This image provides the strongest evidence of existence of black holes for the first time. It also confirms the prediction of the shape and glow of a black hole based on Einstein’s general relativity—Einstein is proved right again.

What Is Life?

While talking about the search for extraterrestrial life, you may notice the difficulty in drawing a line between the living and nonliving. Bacteria are considered life forms, but viruses are not. Artificial Intelligence is able to do a lot of things that human beings can do, but it is not viewed as life by the general public…so what is life after all?

Bacteria VS Virus (from: Act For Libraries)

According to our textbook, there are six key properties for life: order, reproduction, energy utilization, response to the environment, and evolutionary adaptation. Examining those properties, we can easily rule out some suspicious candidates: viruses don’t have orderly arranged molecules; Artificial Intelligence also do not have cell structures.

However, as biologists regard evolutionary adaptation as the most fundamental property, the definition of life can be simplified as “something that can reproduce and evolve through natural selection.” Under this definition, all physical entities that have self-sustaining processes can be called life. For example, Artificial Intelligence, which has been a popular topic in recent years, might be considered as “artificial life” that can reproduce and evolve in the form of codes.

Artificial Intelligence (from: Center for Generational Kinetics)

Now that the definition of life has become more generalized, can we view AI as an advanced life form that has never appeared on Earth before? If we take this different point of view, is cell-based life only a part of the spectrum of life? Maybe we are just in a phase of Earth’s history that life with cell structures are dominant. Then, in the search for extraterrestrial life, what are we really looking for?

Why is Titan Special?

Gattaca (from: Youtube)

If you are a Sci-fi fan like me, you might be able to recall Vincent hiding his identity for the trip to Saturn’s moon Titan in Gattaca.

Star Trek 2009 (from: Youtube)

In Star Trek 2009, Kirk and Spock beam abroad the Romulan ship attacking Earth, while Enterprise hid itself in Titan’s clouds.

Avengers Infinity War (from: Youtube)

Or at least you should remember the battle on Titan (which is an exoplanet based on Saturn’s real-life moon Titan) in Avengers: Infinity War

In fact, Titan has shown up more than once in the Star Trek series as well as in other famous films, novels, and comics. Why always Titan?

What makes Titan exceptional among more than 150 known moons in the Solar System?

  • Titan is the largest moon of Saturn and the second largest moon in the solar system—larger than the planet Mercury.

Titan has a radius of about 1600 miles, which only is 2.5 times smaller than the Earth. The largest moon in the Solar System, Jupiter’s moon Ganymede, is only larger by 2 percent.

  • Titan is the ONLY known moon with a substantial atmosphere in the Solar System.

According to observations from the Voyager space probes, the atmosphere of Titan is thicker and denser than the Earth’s! Its atmosphere is also the only nitrogen-rich dense atmosphere in the Solar System aside from the Earth’s. On Titan, the air is dense enough that you can walk on its surface without a spacesuit. However, you do need an oxygen mask and special suit to protect you from its temperature of -290 °F. Atmospheric methane creates a greenhouse effect, which keeps Titan’s surface from becoming even colder.

  • Other than the Earth, Titan is the ONLY object in the Solar System known to have liquids on its surface.
Near-infrared radiation from the Sun reflecting off Titan’s hydrocarbon seas (from: Wikipedia)

There are rivers, lakes, and seas of liquid methane and ethane on Titan’s surface. Although the surface of this icy world is covered by a “golden hazy atmosphere,” the Cassini-Huygens mission discovered liquid hydrocarbon lakes in Titan’s polar regions. Titan has an Earth-like liquid cycle, which includes raining, filling of the water body, and evaporation. Scientists also suspect that its volcanoes release water instead of molten rock lava. There is also speculation that Titan has a subsurface ocean of water according to the gravity measurements.

  • Titan is considered one of the most habitable place in the Solar System.

The information above reveals Titan’s potential for harboring life forms that can survive in the surface hydrocarbon liquids or the subsurface ocean. Although there’s no evidence of life on Titan so far, it is definitely worth further exploration due to its unique features.

How to Find Orion in the Night Sky

Orion-Yonezu Kenshi (Youtube)
Orion (by me)

One of the most famous and recognizable constellations, Orion is most visible in the evening sky, winter in the Northern Hemisphere. It was named after a hunter in Greek Mythology, Orion. Rigel, a blue-white supergiant, and Betelgeuse, a red supergiant, are the brightest stars in Orion. Thousands of newly formed stars can be found in the direction of the Orion Constellation.

Orion (SPACE.com)

The easiest part t recognize is the Belt of Orion, which consists of Alnitak, Alnilam and Mintaka. In the Northern Hemisphere, it is most visible during January around 9 pm, when it is approximately around the local meridian. If you want to find Orion in the night sky, the first step is to look for three stars located in a straight line.

Depiction of Orion (Wikipedia)

Above the Belt, the shoulder of Orion is marked by two bright stars, Betelgeuse and Bellatrix. The apex of the head, Meissa, forms a triangle with the shoulder. Looking down from the belt, you can find Saiph and Rigel, which represent the knees of Orion. The famous Orion Nebula is in Orion’s Sword, hanging from the Belt.

What’s the weather like on the Sun?

NASA-Fiery Looping Rain on the Sun (from: Youtube)

Just like the Earth, the Sun has weather. The most important features of the Solar Activity includes Sunspots, Solar flares, Coronal mass ejections. and solar winds.

Sunspots (from: wikipedia)

 • Sunspots are spots darker than the surrounding area on the Sun’s photosphere caused by concentration of magnetic flux field. Their number varies in an approximately 11-year cycle.

• Solar flares are sudden flashes of light on the Sun, usually observed on the surface and close to a sunspot group. They are caused by the interaction between accelerated charges particles and the plasma medium.

• Coronal mass ejections (CMEs) are significant releases of plasma caused by magnetic reconnection. They often accompany powerful solar flares. On July 19, 2012, an eruption occurred on the Sun produced a solar flare, followed with a CME, then a coronal rain. In the video at the beginning of the article, each second corresponds to 6 minutes of real time.

• Solar Winds are streams of charged particles released from the corona.

Effects on Earth

How Solar Winds Impact the Earth’s Magnetosphere (from: NASA)

• Earth’s weather and global climate change can be affected by solar activities. Auroras are indicators of the connection between the Sun and the Earth.

• Solar activities also affect GPS, satellites and other high-tech systems. For example, a solar radiation storm can cause noise in imaging systems and permanent damage to exposed detectors on satellites.

The Qiantang River Tidal Bore

Qiantang Tidal Bore in China (from: Youtube)

The Qiantang River runs for 459 km through Zhejiang, China, and flowing into the East China Sea via Hangzhou Bay. From Aug 15th to 21st in the Chinese Lunar Calendar, travelers come to Hangzhou Bay to see the largest tidal bore in the world, which can reach up to 9 meters in height and travel at up to 40 km/h.

The Cause of Tides (from: Wikipedia)

There are several reasons contributing to the spectacular tidal bore. First of all, from Aug 16th to 18th in the Chinese Lunar Calendar, the Sun, the Earth and the Moon are approximately in the same line. The gravitational forces of both the Sun and the Moon work together to create the greatest difference between high tide and low tide, which is called the spring tide.

In addition, the Qiantang River has a horn-shaped estuary, so the river surface suddenly becomes narrow when the water reaches the Hangzhou Bay. The abundance of sediment on the river bed slow down tides that come first, forcing waves behind to drive on those ahead. The prevailing southwest wind in coastal areas in China also helps speed up the tidal bores.

Copernicus in Context

Nicolaus Copernicus (from Wikipedia)

Nicolaus Copernicus (19 February 1473 – 24 May 1543) was one of the most important figures in astronomy history. In order to find a better model to predict planet motions, Copernicus developed the heliocentric theory based on Aristarchus’s work. He calculated both the orbital period and distance to the Sun, providing geometric relationships and therefore strengthening the sun-centered idea. His book, De Revolutionibus Orbium Coelestium(“On the Revolution of the Heavenly Spheres”), triggers a shift from the Ptolemaic model to the sun-centered system, which greatly improves the understanding of the universe.

Contemporary Historical Events

Christopher Columbus discovered the Americas in 1492.

In 1517, Martin Luther argued for spiritual repentance and opposed Roman Catholic Church’s practice of selling plenary indulgences in the Ninety-five Thesis, which starts the Reformation in Europe.

Contemporary Historical Figure

Leonardo di ser Piero da Vinci (15 April 1452 – 2 May 1519) was one of the most famous figures during the Renaissance. Known for his paintings Mona Lisa and The Last Supper, Leonardo da Vinci is also a great sculptor, architect, and scientist.


It is so interesting to put concurrent historical events in loosely related fields together. While someone was looking at the night sky and trying to prove that the Earth is not the center of the Earth, another person was crossing the ocean under sail, leading people to the discovery of a new continent. I start to realize that people never rest on their journey of exploration. In the 15thand 16thcenturies, pioneers challenged the widely-help “truths” or made new discoveries, which eventually brought huge changes in every aspect of the society. Histories in every field are indeed similar: in order to explore the unknown, people experience numerous failures and never stop in quest of truth in their mind, which continuously pushing the wheel of the history forward.

Stellarium: a Great Planetarium Program

Wanna know what the sky looks like today? Here’s an amazing computer program where you can know everything about the sky without walking out of the door!

It is simple to download Stellarium at stellarium.org and follow the instructions. After you install the program and open it, you can input any time and location you want by clicking on the icons on the left side of the screen as shown below.

Screenshot by me

One of the most exciting things about this program is that it provides you with a much clearer view of the universe than what you can observe with the naked eye. Stellarium can line up the constellations and label all the planets, stars, constellations in the sky. In fact, you can even see the sky on the other side of the Earth by turning off the “ground” on the bottom menu, which would make you feel like the ground just turned into glass and you can see through it! Below is a screenshot of today’s sky in Nashville at 17:33 (I dragged on the picture to adjust the view so that it shows the view from lying on the ground and looking up at the sky!)

Today’s sky in Nashville (screenshot by me)

There’s a lot more to explore. I was wondering what the sky is like in my hometown, so I just set the location to Nanjing, China. Then there comes a totally different image because Nanjing is nearly at the opposite side of the Earth. You may notice that is it day time in China, but with the assistance of Stellarium, you can easily figure out which constellations are high in the sky by turning off the “atmosphere” on the bottom menu.

Today’s sky in Nanjing, China (screenshot by me)

Then more and more questions come to mind. What constellation is closest to the Sun right now? How does stars’ relative position to the Sun change during the course of a year? Download Stellarium for free and figure those questions by yourself!