Astronomical Fun facts

The Universe Is really old.

It is generally accepted that the universe began with the Big Bang and is estimated to be approximately 13.7 billion years old. Astronomers calculated this figure by measuring the composition of matter and energy density in the universe, which enabled them to determine how fast the universe expanded in the past. As a result, researchers could turn back the hands of time and pinpoint when the Big Bang occurred. The time in between that explosion and now makes up the age of the universe.

The Universe Is getting bigger

In the 1920s, astronomer Edwin Hubble made the revolutionary discovery that the universe is not static, but rather is expanding. But, it was long thought that the gravity of matter in the universe would slow this expansion or even cause it to contract.

In 1998, the Hubble Space Telescope studied very distant supernovas and found that, a long time ago, the universe was expanding more slowly than it is today. This puzzling discovery suggested that an inexplicable force, called dark energy, is driving the accelerating expansion of the universe. This dark energy is not only thought to be driving the expansion of the universe, it appears to be pulling the cosmos apart at ever-increasing speeds. In 1998, two teams of astronomers announced that not only is the universe expanding, but it is accelerating as well. According to the researchers, the farther a galaxy is from Earth, the faster it is moving away.

The very furthest galaxies are spreading away from us at more than 90% of the speed of light.

The Universe could be flat!

The shape of the universe is influenced by the struggle between the pull of gravity (based on the density of the matter in the universe) and the rate of expansion. If the density of the universe exceeds a certain critical value, then the universe is “closed,” like the surface of a sphere. This implies that the universe is not infinite but has no end. In this case, the universe will eventually stop expanding and start collapsing in on itself, in an event known as the “Big Crunch.”

If the density of the universe is less than the critical density value, then the shape of the universe is “open,” like the surface of a saddle. In this case, the universe has no bounds and will continue to expand forever. Yet, if the density of the universe is exactly equal to the critical density, then the geometry of the universe is “flat,” like a sheet of paper. Here, the universe has no bounds and will expand forever, but the rate of expansion will gradually approach zero after an infinite amount of time. Recent measurements suggest that the universe is flat with roughly a 2 percent margin of error.

Dark matter

We can only detect about 5% of the matter in the Universe. The rest is made up of invisible matter (called dark matter) and a mysterious form of energy known as dark energy.

Light from distant stars and galaxies takes so long to reach us that we are actually seeing these objects as they appeared in the past. As we look up at the sky, we are really looking back in time. For example, the Sun’s light takes almost 8.5 minutes to travel to Earth, so we see the Sun as it looked 8.5 minutes ago.

The nearest star to us, Proxima Centauri, is 4.2 light-years away, so it appears as it was 4.2 years ago. The nearest galaxy is 2.5 million light-years away, and it looks as it did when our Australopithecus hominid ancestors walked the planet. The farther away something is, the further back in time it appears.

Since the star Deneb is 1800 light years away, we see it as it was when the emperor Septimus Severius was ruling the Rome (AD 200).

With powerful telescopes, astronomers can see galaxies two billion light years away. This means we see them as they were when the only life forms in Earth were bacteria.

Traveling at the speed of light it would still take you over 4 years to reach the Sun’s nearest neighbour star.

Shooting stars really aren’t stars.

They are usually just tiny dust particles falling through our atmosphere and they vaporize due to the heat of friction with the atmospheric gases. Earth sometimes passes through cometary orbits. As comets travel around the Sun, they leave behind dust trails. When Earth encounters that dust, we see an increase in meteors as the particles travel through our atmosphere and are burned up.

The sun…our source of energy!

The Sun’s core releases the equivalent of 100 billion nuclear bombs every second. All that energy works its way out through the various layers of the Sun, taking thousands of years to make the trip. The Sun’s energy is emitted as heat and light and it powers the solar system.

Solar flares reach temperatures of 10 million °C and have the energy of a million atom bombs.

If you would place a pinhead sized piece of the Sun on the Earth you would die from standing within 145 km (90 miles) from it.

Only half a billionth of the energy released by the Sun reaches Earth, which probably is a very good thing!

The light we see emitting from the Sun is actually 30 000 years old.

It is estimated that only about 55% of all Americans knows that the Sun is a star. The percentage of South Africans is even less. Did you know this?

The Sun is just one of over 100 billion stars in our galaxy, the Milky Way, and the Milky Way is just one of over 100 billion galaxies in the universe.

What is the coldest place in the Universe?

The Boomerang Nebula is a young planetary nebula and the coldest object found in the Universe so far.  The NASA/ESA Hubble Space Telescope image shows a young planetary nebula known (rather curiously) as the Boomerang Nebula. It is in the constellation of Centaurus, 5000 light-years from Earth. Planetary nebulae form around a bright, central star when it expels gas in the last stages of its life.

The Boomerang Nebula is one of the Universe’s peculiar places. In 1995, using the 15-metre Swedish ESO Sub-millimetre Telescope in Chile, astronomers Sahai and Nyman revealed that it is the coldest place in the Universe found so far. With a temperature of -272C, it is only 1 degree warmer than absolute zero (the lowest limit for all temperatures). Even the -270C background glow from the Big Bang is warmer than this nebula. It is the only object found so far that has a temperature lower than the background radiation. Scientists at MIT were able to get temperatures down below 1 Nano-Kelvin, which is one billionth of a degree Kelvin.

Betelgeuse is sooooo big!

Betelgeuse, the bright star on Orion’s top-left shoulder, is so big that if it was placed where the sun is, it would swallow up Earth, Mars and Jupiter!

How many stars in the Universe?

Its estimated that the number of stars in the universe is greater than the number of grains of sand on all the beaches in the world! On a clear night, we can see the equivalent of a handful of sand, that is about 3,000 stars. There are an estimated 100,000,000,000 in our galaxy alone!

Black holes

Black holes are so dense, and produce such intense gravity, that nothing, not even light, can escape their gravitational clutches. However, there are some unusual situations where a form of radiation called Hawking radiation, can slip away. If you somehow got too close to a black hole and were sucked in by its gravitational pull, it would pull harder on your feet than on your head. You would get stretched out, or spaghettified by the intense pull. You would NOT survive the experience!

Black holes are the only objects in the Universe that can trap light by sheer gravitational force. Scientists believe they are formed when the corpse of a massive star collapses in on itself, becoming so dense that it warps the fabric of space and time.

And any matter that crosses their event horizons, also known as the point of no return, spirals helplessly toward an unknown fate. Despite decades of research, these monstrous cosmological phenomena remain shrouded in mystery.

Matter spiraling into a black hole is torn apart and glows so brightly that it creates the brightest objects in the Universe – quasars.

The swirling gases around a black hole turn it into an electrical generator, making it spout jets of electricity billions of kilometers out into space.

Scientists believe there is be a supermassive black hole at the centre of nearly every galaxy, including our own. These black holes actually anchor galaxies, holding them together in the space.

The black hole at the centre of the Milky Way, Sagittarius A, is more than four million times more massive then our sun. Although the black hole, which is almost 30,000 light years away, is pretty dormant at the moment, scientists believe that 2 million years ago it erupted in an explosion that may have even been visible from Earth.

The opposite of black holes are estimated to be white holes which spray out matter and light like fountains.