Creation for Kids
Planets around other stars: Is there life on them?
Published in Creation 44(4):32–35, 2022
Our star, the sun, has eight planets and many other smaller objects. All of these make up the solar system. But what about all the other stars—200 billion in our galaxy alone? Could they have planets—called extrasolar, i.e., outside our solar system? In other words, could stars have their own stellar systems like our solar system?
But they are so far away. How could we detect planets around them? After all, they would be much smaller than the stars they orbit. And they would not produce their own light; instead, they would reflect light from their star.
Detecting extrasolar planets
The first confirmed extrasolar planet was discovered as recently as 1992. Now there are over 5,000 confirmed extrasolar planets (‘exoplanets’). How do we know?
Some planets have indeed been seen directly from their reflected light. But this is rare because the glare of the star usually overwhelms the faint reflected light.
The most common detection is when the planet moves in front of its star, or ‘transits’. The planet is much smaller than the star, but it will still block some of its light. So astronomers who measure a star’s brightness can detect that it drops very slightly at regular intervals. This method is called the transit or photometric method—from Greek words meaning ‘light measuring’.
They can determine how long the planet takes to orbit its star—its ‘year’—from the interval. Since the astronomers know the mass of the star (and thus its gravity), they can work out the distance of the planet from its star.
Also, the more the brightness dims, the bigger the planet must be. And sometimes astronomers can work out what’s in the planet’s atmosphere.
One problem with this method is that it only works if the planet blocks our line of sight. But there is another method, which was the commonest until 2012. This measures the small movements of the star. The star’s gravity pulls on the planet as it orbits, but the planet’s gravity also pulls equally on the star. But since the star is so much heavier, it moves much less, but we can still detect this movement. How?
Think of an emergency vehicle overtaking your car with its siren blaring. When it is behind you and catching up, the siren seems high-pitched. After it overtakes and moves away, the pitch drops noticeably. This change is called the Doppler effect. A moving star also has a Doppler effect with light. As the star moves towards you, it looks slightly bluer, and it looks a bit redder as it moves away. These colour changes are called blueshift and redshift.
This method is thus called the Doppler or radial velocity method. ‘Radial velocity’ means how fast the star is moving towards or away from us. The period of the ‘wobble’ equals the planet’s year. Also, the stronger the star’s wobble, the more massive the planet must be.
Problems for evolution
Evolutionists believe that our solar system condensed out of a cloud of dust and gas called a nebula. In a previous issue (Creation 42(4):32–35, 2020), we explained the vast problems with this idea, the nebular hypothesis. There are even more problems to explain stellar system origins. Some planets have retrograde orbits, i.e., they orbit in the reverse direction to the star’s spin. Other planets have very slanted orbits, unlike ours that are all almost in the same plane.
Also, some planets are very close to their star, far closer than Mercury is to the sun. The problem is even worse with very large planets close to their star, called ‘hot Jupiters’. Evolutionists used to believe that giant planets could form only in cool areas far from their star, so evolutionists say that these planets migrated into their current positions from further away. But such migrating planets would likely go into a ‘death spiral’—spiralling further and further inwards until the star swallowed them.
Could life exist on other planets?
First things first: even on Earth, life exists only because God created it during Creation Week. It could not have evolved from non-living chemicals.
Second, Earth is ideal for life (see Creation 43(1):32–35, 2021). One reason is that it is the proper distance from our sun for water to be liquid—neither too hot nor too cold. But most stars in the universe are small red stars, too faint to see without a telescope. So a planet would need to orbit very close to be the right temperature, but this causes a problem called tidal locking. That is, the star’s gravity keeps one side always facing the star, and the other side always away from it, so one side will be very hot all the time, and the other side always very cold and dark.
Also, the sun emits a lot of visible light. Green plants use this for photosynthesis—making their food using sunlight. Red stars emit mostly infrared, useless for photosynthesis. And the sun is a very stable star. Red stars emit intense flares that would fry any life on the very close planets. They are also prone to substantial star spots, making the star much dimmer.
The Bible and aliens
Read Genesis 1:16–19, Romans 8:19–22, and Hebrews 2:14.
The Bible doesn’t mention God creating aliens. This by itself doesn’t necessarily prove anything, but other teachings suggest that God didn’t create them, so they don’t exist.
The Bible teaches that God created the earth on Day 1, but the stars on Day 4—plus their planets. Also, when Adam sinned on Earth, God cursed the whole creation. This would mean that any alien homeworlds would have been cursed because of Adam’s sin.
Also, to rescue us, God Himself took on human nature, in Jesus Christ. That way, He could die for human sin and pay the penalty we deserve. But God did not take on the nature of angels to die for their sin, and He didn’t take on alien nature to die for aliens’ sin.
The Bible affirms that Earth is unique—and the best science supports this!
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