The Handy Chemistry Answer Book (2014)

What is astrochemistry?

Astrochemistry is chemistry in space! Astrochemists try to do what all chemists do— study molecules and the reactions of those molecules—except that these chemists are looking in outer space, where temperatures are extremely cold and concentrations are exceptionally dilute. These two properties of outer space combined mean that lots of very strange molecules can exist for a relatively long time.

How do chemists study molecules so far away?

Special kinds of telescopes allow astrochemists to perform spectroscopy on the light (or any type of electromagnetic radiation, not just visible light) coming from a star or other celestial body. Certain features of this radiation allow chemists to measure the quantities of different elements and the surface temperatures of objects like stars and comets.

What was the first molecule detected in space?

Hydrogen was probably the first molecule ever detected in outer space, but you’re probably thinking of something larger than that. If you exclude diatomic molecules (like H₂, N₂, O₂, etc.), formaldehyde (H₂CO) was the first molecule detected in space.

Can radio telescopes detect any kind of molecule?

Radio astronomy can only detect molecules with dipole moments, and the stronger the dipole the easier it is to detect. As a result, carbon monoxide (CO) is very easy to detect in space because of both its strong dipole moment and its relative abundance.

So how then do astrochemists detect H₂ in space?

By looking at other parts of the electromagnetic spectrum, chemists can detect molecules with no net dipole like H₂ (detected by UV radiation) or CH₄ (detected by IR).

What is atomic emission spectroscopy (AES)?

AES measures the wavelengths of light that are emitted (or absorbed) when a sample is burned. The wavelengths of the spectral lines are unique to each element because the energy of the photon released from the atom depends on the electronic structure of the particular atom.

What molecules have chemists detected in interstellar space?

A recent count puts the number of distinct molecules detected in interstellar space at around 150. The list includes small diatomic molecules that are common on Earth (e.g., CO, N₂, O₂), high-energy diatomic radicals that have exceedingly short lifetimes on Earth (e.g., HO·, HC·), and all the way up to organic compounds like acetone, ethylene glycol, and benzene.

Do nuclear reactions take place in outer space?

Yes—inside stars! Nuclear reactions occur frequently in stars as hydrogen atoms undergo fusion to produce helium and eventually other heavier elements. Some additional, higher-energy nuclear reactions also take place when two neutron stars merge.

What are meteorites?

Meteorites are chunks of material (such as giant rocks) from the solar system that manage to make it to the ground as a larger meteor passes through the atmosphere. Meteors entering from outer space pass through the atmosphere at extremely high rates of speed (from 15 to 70 kilometers per second) and tend to mostly burn up in the process. As they pass through the atmosphere, they may be visible from the ground as a streak of light, and this is what is commonly known as a “shooting star.”

What are comets made of?

Comets are space snowballs with some dirt sprinkled in. No, really. Comets are typically balls of rock, frozen water, and gases. Sometimes other chemicals are present in much smaller amounts; these include methanol and ethanol, hydrocarbons, and in 2009 NASA’s Stardust mission confirmed that glycine (an amino acid) was present in the comet called Wild 2.

Do other Earthlike planets exist?

At least one other Earthlike planet has been discovered, and it is possible that many more may exist. In 2011, NASA’s Kepler space telescope discovered a planet (named Kepler-22b for now) orbiting a star about 600 light years from Earth (recall that a light year is the distance light travels in one year, so that’s extremely far away). This planet is estimated to be about 2.4 times the size of Earth and exists in an area known as a “habitable zone,” which means that it is in an area that could potentially serve as a host to life as we know it. Little is known at this time about the atmosphere or composition of this planet, but it is nonetheless interesting that it exists. How many more Earthlike planets might be out there? It’s hard to say, but considering the tremendous number of stars out there (see below), it’s possible that there are a lot!

How does the density of matter in outer space compare with that in Earth’s atmosphere?

To give a quantitative idea of just how dilute the matter in outer space is, consider that roughly 2.5 × 10¹⁹ particles, typically atoms, occupy 1 cm³ (1 mL) of volume in the Earth’s atmosphere. In outer space there is, on average, only one single particle in this same volume. Outer space is a much better vacuum than even the best vacuums ever created on Earth!

How do space probes (like the Curiosity rover) look for molecules on the Moon or Mars?

The Curiosity rover has a whole suite of chemistry tools on board. The laser-induced breakdown spectroscopy (LIBS) tool is probably the coolest. This instrument breaks down rocks and bits of soil by firing a (freaking) laser at the target. The elements that made up that rock are then detected by atomic emission spectroscopy. Curiosity also contains an alpha particle (He²⁺ ion) X-ray spectrometer (APXS), which is also used to measure what elements make up a sample. If the NASA scientists want to know more than just what elements make up a sample, they can use the quadruple mass spectrometer, which can measure the mass of ions of gases and organic compounds.

The Hoba meteorite, located in Namibia, Africa, weighs over sixty tons and is the largest piece of naturally occurring iron known. It is so large and heavy that it has never been moved from the spot where it was discovered.

Could comets have been a “seed” for life on Earth?

Interestingly, some scientists are starting to think so. Fairly recently, amino acids (see the “Biochemistry” chapter) were observed in comets, prompting the idea that these molecules, which play a key role in life on Earth, may actually be extraterrestrial in origin. Subsequent research on how these amino acids might have gotten into comets in the first place uncovered that interstellar model ices were able to serve as a breeding ground for dipeptides (a chain of two amino acids). This result further supports the notion that comets from deep space may plausibly have delivered the building blocks for life on Earth today. This contrasts with a longstanding hypothesis that the Earth’s early oceans may have served as the source from which the building blocks for life first formed.

What is the Sun made of?

The Sun is made up of extremely hot gaseous elements, primarily hydrogen and helium. There are also small amounts of oxygen, nitrogen, carbon, neon, iron, silicon, and magnesium. Because it is so heavy, the Sun produces an extremely strong gravitational pull which leads to very high pressures and temperatures, especially near the Sun’s core (roughly 27 million degrees Fahrenheit, or 15 million degrees Celsius). These extreme conditions can cause two hydrogen atoms to undergo fusion (see “Nuclear Chemistry”) to create a helium atom. The other two parts of the Sun are the radiative layer (the middle layer) and the convective layer (the outermost layer).

Below is a table listing the relative abundance of elements in the Sun. In total there are at least sixty-seven elements that have been identified as being present in the Sun— this table lists the ten most abundant ones.

Most Abundant Elements in the Sun

Why does the sun glow?

The fusion processes happening near the core of the sun cause energy to be given off in the form of photons (see “Physical and Theoretical Chemistry”). The photons given off in the core of the sun collide with other atoms, which absorb photons and, in turn, give off additional photons. This process repeats, potentially millions of times, before photons at the surface of the sun are emitted off into space.

As a side note, everything tends to emit radiation in this way, at least to an extent—it’s just that most things on Earth are not nearly as hot as the sun. Even your own body releases electromagnetic radiation, but the photons coming from your body are in the infrared region of the spectrum, so we cannot see them with our eyes. However, infrared cameras can use the photons given off by a person’s body to locate people (or animals) in this way.

What elements are stars other than the Sun made of?

The Sun is just one of many, many stars that exist. Despite the fact that different stars span a wide range of temperatures and sizes, they are all essentially made up of the same elements as the Sun. Of course, there will be some variations in the relative quantities of the elements present, but, just like the Sun, the main two elements believed to be present in every star are hydrogen and helium.

What happens chemically as stars age?

As stars age, they continually produce helium from hydrogen by fusion. So as time goes by, the amount of helium in a star increases and the amount of hydrogen decreases. In order to keep the fusion reaction going, stars heat up and get brighter as they age. Stars also continually give off a small portion of their mass, which generates solar (or stellar) wind. For our sun this is an exceedingly tiny amount of material, so don’t worry about it vanishing anytime soon. Finally, stars slowly make elements heavier than helium as they age. This is typically quantified by reporting the ratio of iron to hydrogen in a star. Iron is not the most abundant of the heavier elements present in stars, but it is among the easiest of the heavier elements to detect.

Is our Sun unique?

Aside from the fact that we’re spinning around it, not really. It’s a yellow dwarf star of average size (6.960 × 10⁸ m radius, 1.989 × 10³⁰ kg) and surface temperature (5500–6000 K).

Is there water on other planets?

There is, though in most cases where water exists on other planets it does not exist predominantly in the liquid form (like here on Earth). On some planets there may be trace amounts of water vapor in the atmosphere, beds of ice on a planet’s surface, or superheated, ionized water near a planet’s core. There may well be other planets out there with liquid water, but humans have not found many with large amounts of liquid water.

What is a galaxy?

A galaxy is a huge system consisting of stars, planets, gas, dust, and lots of other interstellar media. The galaxy we live in is called the Milky Way. Galaxies have a lot of stars—the smallest have roughly ten million, while the largest have a hundred trillion! All of the “stuff” in a galaxy orbits around the center of mass of that galaxy.

How many stars are in our galaxy?

Astronomers currently believe that our galaxy, the Milky Way, contains between two hundred billion and four hundred billion stars.

What is the hottest planet in our solar system, and why is it so hot?

Venus is the hottest planet, with an average surface temperature of 900 degrees Fahrenheit or 481 degrees Celsius. It’s the second closest to the Sun, with only Mercury orbiting closer. Interestingly enough, the high temperatures on Venus are largely due to a greenhouse effect due to the very high levels of carbon dioxide (CO₂) in its atmosphere.

What is the Big Bang theory?

The Big Bang theory is a model that attempts to explain how the universe was formed. This theory suggests that the universe as we know it came into existence a little less than fourteen billion years ago and that everything started from a very dense, hot, state from which the universe as we know it began to expand. This theory is based on, and is consistent with, all of the current observations we have surrounding the known universe, such as the fact that it is expanding or that there exists a large abundance of light elements in the universe. The one thing left unexplained by this theory, though, which you may likely be wondering about, is how that initial state came to be in the first place. How did the first matter originate, and why was it all packed together in a very dense state? Unfortunately we cannot answer that one, and neither does the Big Bang theory. Rather, the Big Bang theory is only focused on explaining the evolution of the universe from that initial state to what it is today and to what it will become in the future.

Are there alternate theories to the Big Bang theory out there?

There sure are. While the Big Bang theory is probably the most widely known and accepted theory surrounding the origins of the current universe, there are still other theories being explored and proposed. Some of these are much more scientifically feasible than others; take a look around the Web and you can find lots of different ideas out there. One alternative that has received notable attention describes the universe as a continuous cycle of expansion and rebirth; the expansion period, similar to that described in the Big Bang, is followed by a period in which the universe once again becomes a dense mass of condensed matter, and then the expansion begins again.

The Big Bang theory postulates that the universe began as a singularity about four billion years ago, expanding rapidly and eventually forming the stars, galaxies, planets and everything else we see.

What is a black hole?

A black hole is a region of space where the gravitational pull is so strong that nothing, including light, can escape! The size of the black hole is sometimes described by an imaginary surface called the “event horizon,” beyond which nothing will be able to escape the gravitational pull.

What kind of fuel is used to power a spacecraft?

The space shuttle Endeavor, which made its final space voyage in September of 2012, used primarily hydrogen, oxygen, hydrazine (N₂H₄), monomethylhydrazine (CN₂H₆), and nitrogen tetroxide (N₂O₄) as fuels. As it took off for a space voyage, the spacecraft would carry 835,958 gallons of these fuels with a total weight of roughly 1.6 million pounds!

What are the rings around Saturn?

You have probably heard about, and looked at pictures of, the rings around the planet Saturn. On average, these rings are about twenty meters thick and they are made up of 93% ice and about 7% carbon. There is actually a pretty large distribution of particle sizes in these rings, ranging from specks the size of dust to chunks of material ten meters in length. Actually, the origin of the rings is not completely understood, and they may be due to either a destroyed moon or to leftover material from when Saturn was formed.

Does metal rust in outer space?

Sort of. Rusting in outer space doesn’t happen in quite the same way it does on Earth due to differences in the amount of available water. On Earth, iron rusts when it interacts with water molecules causing oxidation of some of the metal atoms to metal oxides. Recalling this information, it is clear that some source of oxygen atoms must be present for metal to rust! There is very little oxygen or water floating around in outer space, so the reaction doesn’t proceed as quickly or via the same mechanism. Actually, in outer space, the very small amounts of oxygen (O₂) or water (H₂O) that are around are believed to undergo photochemical reactions with metals to produce metal oxides, like rust (Fe₂O₃). Scientists can get a sense of how rapidly metals rust in outer space by looking at iron-containing meteorites that reach the Earth.

What is the temperature in outer space?

There is not actually a single uniform temperature for all of outer space; it tends to be warmer (at least in a relative sense) in areas that are closer to stars or planets. On average, though, the temperature is only about 3 Kelvin, which is about -270 degrees Celsius. It is extremely cold in outer space, so we humans would not last long floating around in the far reaches of space (even if we could breathe there, which we can’t).

How do scientists determine how far away a star is?

The answer to this question lies in the application of trigonometry. An astronomer can look at a star at a given point in time and then look at it several months later, after the Earth has moved a substantial distance in its orbit around the Sun. This allows the astronomer to view the star from two different angles. By comparing the images from the two different angles, it is possible to figure out how far away it is.

If a star happens to be too far away the first method described will not be accurate, but fortunately there is an alternative. If an astronomer measures the visible light spectrum of the star, it turns out that one can get a good idea of its actual brightness (by actual, we mean how bright the star is if you are right up close to it). This relationship isn’t entirely straightforward and has only been established after looking at data from thousands of stars. Once the astronomer knows the actual brightness, its brightness can be compared by its apparent brightness as viewed from Earth to determine how far away it is.

How long ago was the light we see from stars emitted?

To figure out how long ago the light we see from stars was emitted, we have to know roughly how far away the star is and use the known speed of light (approximately 3 × 10⁸ meters per second). The Sun is roughly 150 million kilometers from the Earth, from which we can calculate that sunlight reaching the Earth left the Sun roughly eight minutes ago. The distance to the next nearest star is much farther, roughly 410 × 10¹¹ kilometers from Earth. This translates into a time of over four years between when light leaves this star and when it reaches telescopes on Earth. Keep in mind that this is the next nearest star, so all others are even farther away. This also means that, if we see a star explode, it really happened many years ago.

Why is Pluto no longer a planet?

Since Pluto was first discovered in 1930, there has always been some uncertainty about its properties and how they compare to those of the other celestial bodies defined as planets in our solar system. In large part, it is Pluto’s small size that led to it being removed from the list of bodies classified as planets.

According to the International Astronomical Union (IAU), a planet is defined in the following way:

A planet is a celestial body that (a) is in orbit around the sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.

Pluto meets criteria (a) and (b) mentioned above, but it regularly encounters the orbit of the larger planet, Neptune, which is the technical reason used to remove Pluto’s status as one of the planets of our solar system. It is probably worth noting that this resolution was met with some criticism, as even our own planet Earth encounters asteroids in its own orbit on a fairly regular basis.

How many stars exist in total?

This is a difficult question to answer, but we can provide a very rough estimate. In our galaxy alone, there are roughly 10¹¹ to 10¹² stars. Then consider that there are roughly 10¹¹ to 10¹² galaxies in total, and, if we assume the other galaxies are similar to ours, this would put the total number of stars in existence somewhere between 10²² to 10²⁴ stars. Clearly there are too many to count!

What are sunspots?

A sunspot is a temporary spot on the Sun that appears relatively dark. These spots are caused by magnetic “storms” that prevent convection from distributing heat evenly over the surface of the Sun. This results in relatively cold areas of the Sun. These spots may be as large as fifty thousand miles in diameter, such that they can be visible from Earth even without a telescope (but that doesn’t mean you should look at the Sun).

Why do footprints last extra long on the surface of the Moon?

On the Moon, there is no (or extremely little) wind, so the dust will not tend to blow over and fill in your footprints like it does at the beach on Earth. So the footprints left by the earliest humans to visit the Moon should still be there today.

How fast is Earth moving through space?

When taking into account the motion of the Milky Way galaxy, the fact that our solar system rotates within this galaxy, and the motion of the Earth within our solar system, it is estimated that the Earth is moving at about 500 kilometers per second. Of course, since everything around us is moving at the same rate, we don’t tend to notice this.

What is astrobiology?

Astrobiology is a branch of science concerned with looking for signs of life, basically, anywhere other than on planet Earth. This isn’t really the search for space aliens hanging out in close vicinity to our own planet, but rather astrobiology is focused on looking for any evidence for the current or prior existence of even the smallest (microbial) life forms elsewhere in space.

What is a biosignature?

A biosignature is a chemical signature that can be observed from a distance that signals the presence of living organisms. These could include complex chemical structures associated with life forms or accumulated quantities of biomass or waste.

What is a superbubble?

A superbubble is a cloud of superheated gas that can be formed when multiple stars that are relatively near each other die out at similar times. This situation can lead to an explosion that spans hundreds of light years in distance. Recall that a light year is the distance that light travels through space in a year, so we are talking about an absolutely huge explosion! The light generated from this explosion is often not in the visible range of the spectrum, so they can’t always be seen by the naked eye (not to mention the fact that they are also very, very far away).

What is radio astronomy?

Radio astronomers study what’s going on in outer space by using radio waves (as opposed to telescopes, which use light in the visible region of the spectrum). This approach has some distinct advantages, perhaps the most obvious being that radio astronomers can work at any time of the day while astronomers who rely on light telescopes can only work at night. Radio astronomy relies on monitoring weak radio wave signals coming in from outer space, and knowing how to interpret these signals, to draw conclusions about the locations of celestial bodies and events that have taken place far, far away.