Author: Fraser Cain

The first rocket ever sent to space probably carried bacteria or some other accidental passenger. But the first animals ever intentionally sent into space were fruit flies launched aboard a V2 rocket in 1947. US scientists were studying the effects of radiation at high altitude.

A rhesus monkey called Albert 1 became the first monkey launched into space on June 11, 1948; also on board a US-launched V2 rocket.

These were just suborbital flights, though. The first animal to actually go into orbit was the dog Laika, launched on board the Soviet Sputnik 2 spacecraft on November 3, 1957. Unfortunately, Laika died during the flight.

At least 10 more dogs were launched into space and on sub-orbital flights by the Soviets until April 12, 1961, when Yuri Gagarin became the first human in space.

Since those first historic launches, many monkeys, chimpanzees, rats, mice, frogs, spiders, cats and even a tortoise were launched into space.

Read more about Laika’s mission in this article.

Want more resources on space? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Space Place.

We have also recorded many episode of Astronomy Cast about space. Episode 100 is all about rockets, and Episode 84 is about getting around the Solar System.

Our Earth keeps us very safe from a dangerous Universe that’s always trying to kill us in new and interesting ways.

Risk: Cosmic rays are high energy particles fired at nearly the speed of light by the Sun, supermassive black holes and supernovae. They have the ability to blast right through your body, damaging DNA as they go. Long term exposure to cosmic rays increases your chances of getting cancer. Fortunately, we have our atmosphere to protect us. As cosmic rays crash into the atmosphere, they collide with the oxygen and nitrogen molecules in the air.

Risk: Gamma rays and X-rays. As you know, radiation can damage the body. Just a single high-energy photon of gamma rays can cause significant damage to a living cell. Once again, though, the Earth’s atmosphere is there to protect us. The molecules in the atmosphere absorb the high-energy photons preventing any from reaching us on the ground. In fact, X-ray and gamma ray observatories need to be built in space because there’s no way we can see them from the ground.

Risk: Ultraviolet radiation. The Sun is bathing the Earth in ultraviolet radiation; that’s why you get a sunburn. But the ozone layer is a special region of the atmosphere that absorbs much of this radiation. Without the ozone layer we would be much more exposed here on the surface of the Earth to UV rays, leading to eye damage and greater incidence of skin cancer.

Risk: Solar flares. Violent explosions on the surface of the Sun release a huge amount of energy as flares. In addition to a blast of radiation, it often sends out a burst of plasma traveling at nearly the speed of light. The Earth’s magnetosphere protects us here on Earth from the effects of the plasma, keeping it safely away from the surface of the planet. And our atmosphere keeps the X-ray/gamma ray radiation out.

Risk: Cold temperatures. Space itself is just a few degrees above absolute zero, but our atmosphere acts like a blanket, keeping warm temperatures in. Without the atmosphere, we’d freeze almost instantly.

Risk: Vacuum. Space is airless. Without the Earth, there’d be no air to breath, and the lack of pressure damages cells and lets water evaporate out into space. Vacuum would be very, very bad.

If you’d like to hear more about cosmic rays, listen to this episode of Astronomy Cast.

References:
NASA: Danger of Solar and Cosmic Radiation in Space
NASA: Ultraviolet Waves

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The biggest stars in the Universe are the monster red hypergiants, measuring up to 1,500 times the size of the Sun. But what are the smallest stars in the Universe?

The smallest stars around are the tiny red dwarfs. These are stars with 50% the mass of the Sun and smaller. In fact, the least massive red dwarf has 7.5% the mass of the Sun. Even at this smallest size, a star has the temperature and pressures in its core so that nuclear fusion reactions can take place.

One example of red dwarf star is the closest star to Earth, Proxima Centauri, located just 4.2 light-years away. Proxima Centauri has 12% the mass of the Sun, and it’s estimated to be just 14.5% the size of the Sun. The diameter of Proxima Centauri is about 200,000 km. Just for comparison, the diameter of Jupiter is 143,000 km, so Proxima Centauri is only a little larger than Jupiter.

But that’s not the smallest star ever discovered.

The smallest known star right now is OGLE-TR-122b, a red dwarf star that’s part of a binary stellar system. This red dwarf the smallest star to ever have its radius accurately measured; 0.12 solar radii. This works out to be 167,000 km. That’s only 20% larger than Jupiter. You might be surprised to know that OGLE-TR-122b has 100 times the mass of Jupiter, but it’s only a little larger.

And that is the smallest known star. But there are certainly smaller stars out there. The smallest theoretical mass for a star to support nuclear fusion is 0.07 or 0.08 solar masses, so smaller stars are out there.

We have written many articles about stars here on Universe Today. Here’s an article about the biggest star in the Universe.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Stars are mostly balls of hydrogen gas that came together from a nebula of gas and dust. They generate their energy through the process of fusion. This is where atoms of hydrogen are combined together to form helium atoms. And in the process, the star generates a tremendous amount of energy in the form of radiation. So, why do stars die?

This radiation starts up being trapped inside the star, and it can take more than 100,000 years to work its way out. You might not realize it, but light can emit a force when it bumps up against something. So all the light inside the star emits a pressure that opposes the force of gravity pulling all the material inward.

A star can exist in relative stability in this way for billions of years. Eventually, though, the star runs out of hydrogen fuel. At this point, a new reaction takes over, as helium atoms are fused together into heavier and heavier elements, like carbon and oxygen.

Once the helium is used up, a medium-mass star like our Sun just runs out of fuel. It can no longer sustain a fusion reaction. And without the pressure of the light ballooning it out, the star contracts down into a white dwarf – made mostly out of carbon.

A white dwarf star shines because it’s still very hot, but it slowly cools down over time. Eventually it will become cool enough that it’s invisible. And if we could wait long enough, the star would become a black dwarf star. The Universe hasn’t existed long enough for us to have any black dwarfs, but there are plenty of white dwarfs.

We have written many articles about stars here on Universe Today. Here’s an article about a hypergiant star that’s about to die.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

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Head outside on a dark night and look up into the night sky. If you’re away from the bright city lights and it’s a clear night, you should see beautiful stars shining in the night. Just think, the light from those stars has traveled light-years through space to reach your eyes. But why do stars shine at all? Where is the light coming from?

All stars, and our own Sun is just an example, are hot balls of glowing plasma held together by their own gravity. And the gravity of a star is very intense. Stars are continuously crushing themselves inward, and the gravitational friction of this causes their interiors to heat up. A star like the Sun is a mere 5,800 Kelvin at its surface, but at its core, it can be 15 million Kelvin – now that’s hot!

The intense pressure and temperature at the core of a star allow nuclear fusion reactions to take place. This is where atoms of hydrogen are fused into atoms of helium (through several stages). This reaction releases an enormous amount of energy in the form of gamma rays. These gamma rays are trapped inside the star, and they push outward against the gravitational contraction of the star. That’s why stars hold to a certain size, and don’t continue contracting. The gamma rays jump around in the star, trying to get out. They’re absorbed by one atom, and then emitted again. This can happen many times a second, and a single photon can take 100,000 years to get from the core of the star to its surface.

When the photons have reached the surface, they’ve lost some of their energy, becoming visible light photons, and not the gamma rays they started out as. These photons leap off the surface of the Sun and head out in a straight line into space. They can travel forever if they don’t run into anything.

When you look at a star like Sirius, located about 8 light-years away, you’re seeing photons that left the surface of the star 8 years ago and traveled through space, without running into anything. Your eyeballs are the first thing those photons have encountered.

So why do stars shine? Because they have huge fusion reactors in their cores releasing a tremendous amount of energy.

We have written many articles about stars here on Universe Today. Here’s an article about an artificial star that astronomers create, and here’s an article about a star that recently shut down nuclear fusion in its core.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

References:
University of Illinois
NASA

As you probably can guess, our Sun is an average star. Stars can be bigger than the Sun, and stars can be smaller. Let’s take a look at the size of stars.

The smallest stars out there are the tiny red dwarfs. These are stars with no more than 50% the mass of the Sun, and they can have as little as 7.5% the mass of the Sun. This is the minimum mass you need for a star to be able to support nuclear fusion in its core. Below this mass and you get the failed star brown dwarfs. One fairly well known example of a red dwarf star is Proxima Centauri; the closest star to Earth. This star has about 12% the mass of the Sun, and about 14% the size of the Sun – about 200,000 km across, which is only a little larger than Jupiter.

Our own Sun is an example of an average star. It has a diameter of 1.4 million kilometers… today. But when our Sun nears the end of its life, it will bloat up as a red giant, and grow to 300 times its original size. This will consume the orbits of the inner planets: Mercury, Venus, and yes, even Earth.

An example of a larger star than our Sun is the blue supergiant Rigel in the constellation Orion. This is a star with 17 times the mass of the Sun, which puts out 66,000 times as much energy. Rigel is estimated to be 62 times as big as the Sun.

Bigger? No problem. Let’s take a look at the red supergiant Betelgeuse, also in the constellation Orion. Betelgeuse has 20 times the mass of the Sun, and it’s nearing the end of its life; astronomers think Betelgeuse might explode as a supernova within the next 1,000 years. Betelgeuse has bloated out to more than 1,000 times the size of the Sun. This would consume the orbit of Mars and almost reach Jupiter.

But the biggest star in the Universe is thought to be the monster VY Canis Majoris. This red hypergiant star is thought to be 1,800 times the size of the Sun. This star would almost touch the orbit of Saturn if it were in our Solar System.

We have written many articles about stars here on Universe Today. Here’s an article about the biggest star in the Universe, and here’s a more detailed article about red dwarfs.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

References:
http://www.telescope.org/pparc/res8.html
http://en.wikipedia.org/wiki/Proxima_Centauri
http://www.windows2universe.org/sun/statistics.html
http://earthsky.org/brightest-stars/blue-white-rigel-is-orions-brightest-star