Category Archives: Mac’s Notebook

The Search for Extraterrestrial Life



The planet KELT-16b has been spiraling around its star for over 2 billion years. In a few hundred thousand more, it will finishing circling the stellar drain, and be consumed by its star. In the meantime, astronomers are getting all the information from it they can, in the hopes of discovering more about extra terrestrial life from its atmosphere.

Atmospheric analysis is generally considered to be our best hopes of discovering planets hosting life forms, especially those that haven’t reached a human level of intelligence. Life, at least the type we’re familiar with, tends to produce certain telltale traces of gas, when then affect the light and other radiation being emitted by the planet. Oxygen is one of the signs of life like we have on our planet, since animals need it to live, and plants produce it. However, for the time being scientists can only closely monitor our neighbors in the Solar system, which limits our data to planets experiencing the conditions present in the Solar System. A situation like that of KELT-16b gives us a lot of information, since the situation changes incredibly rapidly. It makes a full rotation of the sun in under a day, meaning that both the seasons and the temperature are in constant flux.

Some of the Satelite Dishes SETI Uses to Search for Radio Signals.

Of course, KELT-16b isn’t the only way scientists are trying to get a better grip on whether or not extraterrestrial life exists. As mentioned earlier, analysis of the physical attributes of planets is one major approach. Beyond that, the SETI, or Search for Extraterrestrial Intelligence, Institute tries to determine if there are any civilizations out there by looking at radio signals. While radio emissions are present throughout the universe, they tend to be very spread out naturally. Because of this, if SETI found a strong signal coming from a very specific region of space, that would be strong evidence in favor of it coming from an alien civilization.

Of course, the question of whether or not extraterrestrial life exists at all is still up in the air. We’ve yet to find any solid proof that it does, but with such a gigantic universe, it’s almost impossible to rule it out. Additionally, our current methods almost exclusively focus on finding similar life to that on Earth, since that’s what we know the most about, and thus can find the most easily. As our knowledge of exoplanets and the strength of our telescopes increase, hopefully we’ll eventually find an answer

Black Holes and Stars


An artist’s representation of this star system.

Astronomers have just found a star that’s orbiting a black hole once every 28 minutes. The binary star system X9 is now suspected to consist of a white dwarf star orbiting a massive black hole. While this isn’t particularly unusual, what is notable is exactly how close the two objects are to each other — separated by only two and a half times the distance between the Earth and its moon. This radius of orbit combined with the period of rotation is incredibly fast, as it requires the star to be whipping around the black hole at 8 million miles per hour, or about 1/100th of the speed of light. Of course, this doesn’t bode well for the star: the black hole is constantly ripping matter away from the white dwarf, which means there’s a good chance it’ll end up losing so much mass it completely evaporates.

Black holes, one of the more interesting objects in the universe, are born when stars collapse into themselves, having so much mass that the internal gravity pulls the matter into a single point, creating a singularity that can pull light into it, permanently. This usually happens while a star is dying. Many larger stars have enough mass that, if it were condensed into a point, a black hole could be created, but the forces caused by the fusion at the center of a star counteract the pull of internal gravity. When a star reaches the end of its life however, this fusion ends, and there’s no longer anything pushing the star outwards. If the star is smaller, or up to around 3 times the mass of our sun, it becomes a neutron star, but if it has any more mass than that, a black hole is created.

A black hole passing in front of a galaxy.

Once a star turns into a black hole, not much changes in the surrounding area. While black holes do exert a tremendous gravitational force at the singularity, once you get far enough away, they exert the exact same gravitational force as the star they were born from, since after all, it’s the exact same amount of mass, in roughly the same location as the star. For example, if our sun were to be replaced with a black hole of the same mass, the planets would continue to orbit in exactly the same pattern as before. Of course, the lack of light and heat would change the planets indelibly, but their paths would stay the same.

Sagittarius A*, with the black hole and reflected light from it.

One of the interesting effects of the relative benignity of black holes, is that scientists currently believe that all galaxies have a supermassive black hole at their center, which the star systems all orbit around. Again, this in no way means that the systems are going to end up being sucked into the black hole, the physics is the same as if there were a colossal star, or even just a really big planet at the center. The one at the center of the Milky Way is known as Sagittarius A*, pronounced “Sagittarius A-star.”

Find out more about this black hole!

Neanderthals, Our Species’ Closest Cousins.

An Artist’s Reconstruction of a Neanderthal

Humans may not have lived with dinosaurs, but they did once share the Earth with creatures very similar to us. Neanderthals, or homo neanderthalensis, shared the planet with us until about 40,000 years ago. Despite them having died out millennia ago, archaeologists are still finding evidence of their existence, and learning more about what their lives were like, and how they related to us. Some things that we do know are that they were very similar to us intellectually, with practices such as wearing clothes and having burial rites, and that they coexisted with us for some time.

One of the biggest questions about Neanderthals is whether or not they were a distinct species, or if they were just a subspecies of humanity. The current view of the scientific community is that they are a distinct species, and that they and humans both evolved from homo erectus, an ancestor that existed in Africa hundreds of thousands of years ago. This conclusion was largely reached by analyzing Neanderthal DNA and comparing it to Human DNA.

Fragments of Neanderthal 1, the First Neanderthal Fossil

Of course, that raises the question of how exactly we have intact DNA from a species that went extinct 40,000 years before we even knew DNA was a thing. The answer is that tiny amounts of DNA can persist in the core of fossilized bone, and thankfully we’ve found a substantial number of fossils from Neanderthals. The first to be discovered wasn’t immediately recognized as being from a distinct species — after all, it was the first evidence we had of there being another hominid species in our planet’s history — but analysis of the structure of its skull found it to be so distinct from modern humans that it had to be a different species.

A Neanderthal’s Upper Jaw

Since then, we’ve found out more and more about Neanderthals. Discoveries such as the Altamura Skeleton, an almost complete ancient human skeleton found in Italy, have increased our understanding of exactly what they looked like. The upper jaw of a Neanderthal recently discovered in Spain revealed that Neanderthals used the gum of a poplar tree as sort of an ancient Aspirin when their stomachs hurt, and may have known about penicillin.

Find out more about Neanderthals’ dietary habits!

TRAPPIST-1, an Earth-like Solar System

An Artist’s Interpretation of the TRAPPIST-1 sytem

Astronomers recently made a discovery of colossal importance – the existence of a star system, named TRAPPIST-1, with the conditions to potentially support human life. The system has seven planets, all orbiting a red dwarf star. While the planets are about the same size as Earth, the star itself is tiny, as the term dwarf star might suggest. It’s about 1/12 the size of our sun, according to Dr. Gillion, a NASA scientist, if our sun were a basketball, this star would be a golf ball.

A Poster Made by NASA to Publicize the Discovery.

The significance of this discovery comes from the distance of the planets and the heat of the star. Astronomers currently believe that some of the planets might be in what is known as the “Goldilocks zone,” the band around a star where the temperature of a planet is low enough for water to not evaporate, but warm enough that it doesn’t free, allowing for the possibility of liquid water, which means that it could likely support life, either extraterrestrial, or that of human colonists.

The big issue however, is that the system is 39 light years away, or 235,000,000,000,000 miles away. With our current technology, this makes travel to TRAPPIST-1 completely infeasible. However, on a galactic scale, the solar system is incredibly close to Earth, only about ten times the distance of the closest star, Alpha Centauri. This gives us a huge step towards finding out more about life on other worlds, since we can observe the planets of TRAPPIST-1 much more easily than we can further worlds.

An image captured by a NASA telescope of star Trappist-1

Despite its relative proximity, we still can’t directly observe the exoplanets of TRAPPIST-1. Instead, we rely on observing the star at the center of the system, and looking for fluctuations in the light it puts out to detect planets. Likewise, to make observations about the atmosphere and conditions of the planets, we have to use indirect methods. For example, to determine the status of the atmosphere on a planet, scientists look at the infrared radiation being emitted, since it’s possible to derive a lot of information about the temperature of a planet from the heat it admits into space.

The Mantle of the Earth Now Believed to be Hotter Than Before.

A visualization of the layers of the Earth

The mantle of the Earth. The 1800 mile thick section of the Earth’s interior between the crust, which we live on, and the core, the ball of molten metal at the center of the planet. Compared to the other two sections, its makeup is more variable, with sections closer to the core being made up of solid rock, and upper sections reaching their melting temperatures and becoming molten. The mantle is responsible for much of the interesting geological occurrences on the planet, the most impressive of which is likely volcanic eruptions, which occur when molten mantle rock is shoved upwards and reaches the crust.

Molten rock from the mantle causes volcanic eruptions

Of course, volcanoes are only possible if the rock of the mantle is molten, which requires very high temperatures. This makes the question of the temperature of the Earth’s mantle one that scientists are very interested in solving. Scientists already know certain things about the Earth’s mantle, most importantly that there’s a boundary a couple dozen miles below the surface of the Earth that marks the point above which the rock begins to melt. To find the temperature of mantle rock, scientists should just have to find what temperature its components melt at, and derive it from that.

A sample of peridotite

The main obstacle to this has been that the material most of the upper mantle is made of, peridotite, tends to have water within it, and it’s very difficult to control the amount of water to get it to match the Earth’s core. Previous attempts to account for this have found that the temperature of this boundary point is likely 1350° Celsius, or 2462° Fahrenheit. However, a new method to test the amount of moisture in a sample of peridotite found that previous samples weren’t dry at all, despite previous assumptions! As a result, they found that the temperature of the mantle is likely 60° above what had previously been estimated, or 1410° Celsius. While this number may seem relatively insignificant, previous changes to the temperature of the mantle had been around 10° or less, so this represents a substantial change to our understanding of what lies beneath our feet.