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Skywatching

Planets putting on show as they line up in night sky

The planets are lining up

It is not often that all the planets in the Solar System other than ours are lined up across the night sky for us to see.

The show is in progress now and will climax at the end of February, when Mercury sneaks up through the sunset glow to complete the cast of the show.

Moving outward from the sun, the Solar System's known planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury, Venus, Mars, Jupiter and Saturn are easily visible to the naked eye. Uranus and Neptune need binoculars or a telescope and knowing exactly where to look.

Today’s column focuses on the five that can be found without any optical assistance.

Having all the planets other than ours lined up across the sky is quite rare, but not really scientifically special. Imagine seeing the Solar System from above, with the sun in the middle and all the planets moving around it in concentric circles (or near-circles), in the same direction.

The speed with which they move around their orbits decreases with increasing distance from the sun. All the planets are moving in the same plane, like marbles rolling around on a plate. We live on the third marble out from the centre. In such an arrangement, there will be times that from our position on planet 3, we will see the other bright planets strung out to the left or the right of the sun.

Having the sun on the end of the line means we can have the sun below the horizon, giving us a dark enough sky to see the planets. That happens after sunset, when the planets are to the left of the sun and before sunrise, when the planets are to the right of the sun.

Because Mercury and Venus—being the two planets closest to the sun—can never be far from it as viewed from Earth, start observing soon after sunset, as soon as the stars become visible.

At first sight the planets look like stars, bright point-like objects in the sky. But if you look at them carefully, you will see they shine steadily, whereas the stars twinkle. This is because the stars truly are points of light, whereas the planets are actually tiny discs, as binoculars or a telescope will show.

At the moment, starting in the southwest after sunset, there is Saturn, moderately bright and golden coloured. Next, to the left, is Venus, brilliant white, like an escaped aircraft landing light. Further to the left and higher in the sky is Jupiter, almost as bright and a little bit yellowish. Then there is Mars, less bright than Jupiter and obviously reddish in colour.

All these planets justify getting out the binoculars or better yet, a small telescope. Saturn is surrounded by a system of rings, normally making it the most spectacular planet in the Solar System for anyone with a small telescope. At the moment, we are seeing the rings almost edge-on. Venus appears as a glaringly bright crescent. Jupiter is always worth a look. Binoculars will reveal a tan-coloured disc, with its four largest moons in line with the planet, like beads on a wire.

Mars, the “red planet,” requires a bigger telescope to reveal any of its surface features. However, even with binoculars or a small telescope, it is intriguing to look at that red disc and think about what our spacecraft are telling us about that world, which long ago was so much like ours, and still resembles ours enough to attract intense interest.

In late February, Mercury—the closest planet to the sun—will be far enough to the left of the sun to be above the horizon to be seen against the post-sunset glow. It the sky is clear the planet should be visible as a starlike dot. Binoculars or a small telescope may help, however, only if the sun swell below the horizon.

The only effect this lineup of the planets will have on us is to give us a fantastic opportunity for planet watching. The next lineup will be at the end of February 2048. Then the planets will be lined up to the right of the sun and much lower in the sky so don't waste this opportunity.

•••

• The moon will reached its first quarter on Feb 5.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.





Al Jabbar and the two giants

Huge doomed stars

Al Jabbar is one of the Arabic names for Orion, the “Hunter", one of winter's most conspicuous constellations.

At this time of the year, on a clear night you should be able to see in the southern sky three stars in a row. They mark the hunter's “belt.” From there it is easy to see the four stars forming his body, and the silvery streak extending down from his belt, marking his sword.

That silvery streak contains the Great Orion Nebula, one of the most conspicuous gas clouds and stellar nurseries in the sky. Orion is having a face-off with Taurus, the “Bull,” whose head is marked by a V-shaped group of stars to Orion's right, with the red star Aldebaran marking the bull's angry, red eye.

Orion is being assisted by two dogs, Canis Major, the principal dog, lower and behind Orion, marked by its brightest star, Sirius. This is the brightest star visible in our night skies. Higher up is a less bright star, Procyon, which is the main star in Canis Minor, the not-so-senior dog. Note that both dogs are making sure they have Orion between them and the bull. Running under his feet is Lepus, the “Hare,” which is probably not a participant.

The two giants riding along with Orion are Rigel, a blue-white supergiant star marking his right knee and Betelgeuse, a red supergiant marking his left shoulder. The colours are clearly visible. To see them even more clearly, use a pair of binoculars that are thrown out of focus. This spreads the intense dots of light into dimmer, coloured discs.

Rigel lies some 860 light years away. It has about 20 times the mass of the sun and is some 120,000 times brighter. It is far bigger than the sun. If it were put at the centre of the Solar System, Mercury and Venus would lie inside. However, for us on Earth it would make little difference, because we would be instantly fried anyway.

With a mass 21 times that of the sun but shining 120,000 times brighter means it is burning its fuel at a ferocious rate. This star is going from birth to death in a supernova explosion in maybe 10 million years. The lifetime of the sun is expected to be around eight billion years.

Rigel's large size means its gravitational hold over its outer layers is comparatively weak, making it easy for its ferocious energy output to blast the star's material off into space. Over its lifetime, it has blown off around three solar masses of material.

Betelgeuse is spectacularly different from Rigel. It is conspicuously red, with a surface temperature of around 3,000 C rather than Rigel's 12,000 C. Our sun has a surface temperature of around 6,000 C.

This star's name is often pronounced as "beetle juice", but Beteljurze (betel as in petal) is probably closer to the original Arabic (bat al-jauza).

Betelgeuse has a mass of 16.5 times that of the sun, shines with the brightness of 14,000 suns, and lies very roughly 500 light years away. As in the case of Rigel, Betelgeuse is gulping through its fuel supply at a huge rate, so it too measures its life in millions of years rather than billions.

Although only around 10 million years old, Betelgeuse is now running out of fuel and is in an even more precarious energy situation than Rigel. Observations made thousands of years ago describe this star as being yellow. If that is the case, the onset of old age has been very rapid.

Ageing stars swell up. Betelgeuse is now so large that if it replaced the sun at the centre of the Solar System, Mercury, Venus, Earth and Mars would all be inside it. However, being so swollen, the density of the star's outer layers is very low, so its gravitational hold on them is even precarious than Rigel's, and its radiation is blasting material off into space. That ejected material has blown a hole in the interstellar clouds some four light years across.

Both Rigel and Betelgeuse will end their lives in supernova explosions, and end up as either neutron stars or black holes. Betelgeuse can go any time—tomorrow or in the next million years.

•••

• Saturn lies low in southwest, low in the after-sunset glow.

• Scanning left from Saturn we find Venus, then Jupiter and finally, Mars. This is the build up to late February's lineup of the planets.

• The Moon will be new on Jan. 29.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.



Are we living in a black hole?

Galaxy in a black hole?

There is an interesting idea circulating through the astronomical community at the moment.

This is not to say everyone believes it, but there is some evidence supporting it, so it is getting a fair amount of attention. The idea is that we might be living in a black hole.

There are many black holes in our universe. There are those formed in the death throes of giant stars. Massive ones, with masses millions or billions times that of the Sun, sit in the middle of most galaxies, including ours. There are suggestions there could be lots of tiny ones we have not yet detected.

A black hole is the result of the extreme compression of matter. The usual way we see this happening is in the explosion of giant stars at the ends of their lives. The collapse and subsequent explosion compresses the core of the star to the point where it collapses into a black hole.

Any body, whether an asteroid, a moon, a planet or a star, can become a black hole if compressed enough. There will be a point where its gravitational attraction becomes too large to resist. The body will then collapse indefinitely into something extremely small and unbelievably dense.

During that collapse its gravitational attraction grows rapidly, increasingly distorting the fabric of space-time until it forms a bubble shutting off the shrinking body from the rest of the universe. That bubble is known as an “event horizon.”

Things can find their way in, but nothing, not even light, can get out. The body has become a black hole.

The strength of gravity we experience on the surface of the Earth is determined by two things, the diameter of our world and its mass. If our planet was suddenly compressed to half its current diameter, the pull of gravity would be four times larger and we would weigh four times as much.

It is possible, in theory at least, to compress the Earth down to a diameter of a centimetre. At that point the pull of gravity would be ten billion times stronger who than we currently experience. That would be enough to form an event horizon, turning our planet into a black hole.

If we could compress the Sun, it would become a black hole as soon as its diameter fell to three kilometres. Such compression sounds utterly impossible, but we need to remember that matter, as we understand it, is almost totally empty space. There is plenty of emptiness to squeeze out. We can now calculate how much any mass of material has to shrink to become a black hole.

When we look into deep space, we see distant galaxies are receding from us and the farther out we look, the faster they are going. There is theoretically a point where those galaxies would recede at the speed of light and become unobservable. We call what we can see the “Observable” Universe.

Although Einstein's Theory of Relativity states material objects cannot move through space faster than light, a result that has been confirmed in a number of experiments, space-time itself can expand at any speed, carrying the galaxies with it. Imagine a swimmer who can only swim slowly being carried away by fast-moving river.

The current diameter of the Observable Universe is about 93 billion light years, and is estimated to have a total mass of about 6e51 kg (that is six followed by 51 zeroes).

This is where things become really weird. According to the relationship between the masses and sizes of black holes, our universe qualifies as a particularly big black hole.

This idea may or may not be true, but it is a testament to the instruments available to us today that we can even consider such questions.

For years scientists have wondered what the inside of a black hole may be like. Maybe we already know.

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•.After sunset, Venus shines low in the southwest with Saturn close by.

• Jupiter lies high in the southeast and Mars is rising in the northeast.

• The Moon will reach its last quarter Jan. 21 and will be new on Jan. 29.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.





Will we recognize alien life if we find it?

Searching for life out there

In searching for life on other planets, including on planets orbiting other stars (exoplanets), we are faced with some serious problems.

In the case of exoplanets, we are forced to observe from a great distance. Even at the speed of the Parker Solar Probe, the fastest moving spacecraft we have ever made, it would take us around 6,500 years to reach the nearest star. Looking at exoplanets for signs of life is being done using our telescopes, on the ground and in space. For the planets and moons in our Solar System, we can land spacecraft on them or orbit around them.

In many cases, it isn't out of the question that at some point in the next few years, space-suited feet will be walking on them. The exceptions will be where the conditions are just too extreme, such as on Venus or in orbit around Jupiter. This brings us to the biggest question. What are we looking for?

If we receive signals from distant worlds that are obviously produced by intelligent beings, or when we land on a planet and we see things crawling around, or fossils of possible extinct things that once crawled around, we have an answer. However, the search for alien life is likely to be more complicated than that.

Using what we see around us on our own world will be a help, but we have to be very careful not to adhere too closely to what we see here as an indicator of what extraterrestrial life, or evidence of it, will be like.

Since life appeared here on Earth around four billion years ago, it has gone through a long series of extinctions, where large numbers of species vanished. Those events were caused by environmental disruptions due to tectonic and volcanic activity, and the odd asteroid impact, After things recovered following the extinction, the survivors expanded and diversified to fill the ecological void, only to encounter the next extinction.

An example is some 250 million years ago, at the end of the Permian Period, more than 90% of animal species were wiped out, making room for the age of the dinosaurs to begin. That age ended around 65 million years ago, at the end of the Cretaceous Period, in an extinction where around 75% of species were wiped out.

The survivors of extinctions were not always the smartest. They were often just lucky. That led to humans, and all other living things, sharing this planet, the result of many throws of the genetic dice.

Other worlds will have their own throws of the dice, so there is little chance beings on those worlds will be like those living here, or that any intelligent creatures will look anything like us, or share our ideas and attitudes. Beings living in water would know little about fire and would have real problems with electricity and related technologies.

How then are we to search for extraterrestrial life?

One idea being followed is to look for things that living things introduce into their environments. In the case of our world, the answer is oxygen. This highly reactive gas does not occur naturally, and moreover, will react with minerals, and vanish quickly if not kept topped up.

The oxygen we breathe is a by-product of photosynthesis in plants. Finding oxygen, or other highly reactive gases such as chlorine in the atmosphere of a planet, would be a strong indicator of life being present.

Life as we know it is made up of complicated molecules. As far as we know, only living things make such molecules and as we live and die, those molecules find their way into the environment.

We know, for example, soil samples from the Moon contain no large molecules, whereas a sample of soil from our world would be loaded with them. We are searching for such molecules in the atmospheres of exoplanets, the soils of Mars and hopefully soon, in the under-ice oceans of Europa and Enceladus.

Of course, knowing life exists might not mean we will recognize that life when we see it. Have you ever seen a sea cucumber?

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• After sunset, Venus shines low in the southwest with Saturn close by. Jupiter lies high in the southeast and Mars rises in the northeast.

• The Moon will reach last quarter on Jan 21.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.



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About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



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The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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