Category: Space Published: April 2, 2017
Public Domain Image, source: NASA.
We don't know that it is still there. For all we know, the North Star or any other star could have been ingested by a passing black hole years ago. (Although this is highly unlikely, it is possible.) When you look at a star, you are looking at the light that came from the star. Because stars are so far away, it takes years for their light to reach us. Therefore, when you look at a star, you are actually seeing what it looked like years ago. It is entirely possible that some of the stars you see tonight do not actually exist anymore.
Keep in mind that nothing in the universe can travel faster than light. This means that there is no way for us to know about the present state of stars. The most recent information we can ever have about a star is the information in the light that it emitted years ago. For close stars, the information we are now receiving is only a few years old. For the most distant stars in our observable universe, the information we are now receiving is billions of years old. For these distant stars, it is quite likely that they look very different from what we see in the light that we are now receiving. However, there is no way for us to know the present state of a star or for the present state of a star to affect us in any way. Therefore, even if a star that we see in the sky does not really exist anymore, this fact means nothing to us at the current moment. Therefore, it is more of a philosophical question whether a certain star really exists anymore or not. Scientifically, its light is still reaching us and therefore the star still exists from our viewpoint.
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Topics: light, star, time
FAQs
Keep in mind that nothing in the universe can travel faster than light. This means that there is no way for us to know about the present state of stars. The most recent information we can ever have about a star is the information in the light that it emitted years ago.
How do we know stars are light-years away? ›
By looking at a star one day and then looking at it again 6 months later, an astronomer can see a difference in the viewing angle for the star. With a little trigonometry, the different angles yield a distance. This technique works for stars within about 400 light years of earth.
Do stars we see still exist? ›
For the most part, the stars you see with the naked eye (that is, without a telescope) are still alive. These stars are usually no more than about 10,000 light years away, so the light we see left them about 10,000 years ago.
How can we see the stars if they are so far away? ›
Answer: Even though the stars that we see in the night sky are all very far away, we can see them not by actually being able to resolve their sizes, but by measuring the light that they produce.
How long does the light of a star take to reach us? ›
Other Galaxies
| Object | Time for the Light to Reach Us |
|---|
| Alpha Centauri (nearest star system) | 4.3 years |
| Sirius (brightest star in our sky) | 9 years |
| Betelgeuse (bright star) | 430 years |
| Orion Nebula | 1500 years |
5 more rowsMass is the key factor in determining the lifespan of a main sequence star, its size and its luminosity. Stars on the main sequence also appear to be unchanging for long periods of time.
Are stars 4 light years away? ›
The closest star, Proxima Centauri, is 4.24 light-years away. A light-year is 9.44 trillion km, or 5.88 trillion miles. That is an incredibly large distance.
Are we looking back in time at stars? ›
Stars are like your very own sparkly, astronomical time machine, taking you back thousands of years. All of the stars you can see with the unaided eye lie within about 4,000 light-years of us. So, at most, you are seeing stars as they appeared 4,000 years ago.
Why can't we see stars in space anymore? ›
The answer: The stars are there, they're just too faint to show up.
Do the stars we see have planets? ›
Astronomers think that nearly every star in the universe could have at least one planet. That's trillions of planets, waiting to be found. If you go outside on a clear night and look up at the stars, virtually every star you can see has at least one planet in orbit around it, and most likely, several.
Indeed, they are visible, and there are plenty of pictures to prove it. The only problem is that most photos of space show the surface of the Earth, an orbital station, or other space objects. And in the absence of sunlight, they cannot be seen at all or are seen very poorly.
How long do stars live? ›
Every star has its own life cycle, ranging from a few million to trillions of years, and its properties change as it ages.
How long will it take to reach the stars? ›
In short, at a maximum velocity of 56,000 km/h, Deep Space 1 would take over 81,000 years to traverse the 4.24 light-years between Earth and Proxima Centauri. To put that time-scale into perspective, that would be over 2,700 human generations.
How long has it taken light to reach us from these galaxies? ›
The extreme distance of these newly discovered galaxies means their light has been traveling to us for more than 13 billion years, from a time when the Universe was less than 4% of its current age.
How many years is 400 light-years? ›
Convert your speed to the speed of light (for example: 0.001 times the speed of light), and then divide the 400 light-years by that number. In this example, 400,000 years … but currently, no spacecraft can get to such speeds - since that would be about 300 kilometers per second.
How do scientists know what other stars are made of if they are light years away? ›
The most common method astronomers use to determine the composition of stars, planets, and other objects is spectroscopy. Today, this process uses instruments with a grating that spreads out the light from an object by wavelength.
Why do we see the past when we look into space? ›
Because light takes time to travel from one place to another, we see objects not as they are now but as they were at the time when they released the light that has traveled across the universe to us. Astronomers can therefore look farther back through time by studying progressively more-distant objects.
Why do we see stars years later? ›
Light from nearby stars take less time to travel to Earth than light from distant stars. After the Sun, the next closest star, Proxima Centauri, is 25 trillion miles from Earth. Light from that star takes 4.3 years to reach us. Thus, when we observe this star we are seeing it as it was 4.3 years ago.
