We’ve heard of new celestial bodies every day, right? However, the actions behind the scenes are vital to open up the secrets of those objects. So, let’s find out the ways to find celestial objects in this article.
Stars
The easiest objects to find are stars simply because they emit light. When we look up at the night sky, we see a lot of stars, right? Astronomers are continuously doing the same thing, too, but on a much larger scale. That’s because all stars that can be seen with the naked eye have been discovered unless it’s a supernova.
Space telescopes use advanced technology to find even the faintest signs of a star. Why do they need that equipment? Well, as more and more stars get discovered, the limit of how far telescopes can see gets further and further. Moreover, we need more advanced technology to observe distant stars since they’re often dimmer than closer stars as seen from Earth. Of course, that depends on the size and color of the star, too. Still, diminishing magnitudes over distance is a general situation.
However, as the distance of the star gets further, the difficulties of pinpointing it rise dramatically. For instance, there can be fake signs like radio emissions. So, they may have to use different wavelengths to confirm that it’s a proper star.
Star Systems
Moreover, what used to be a “star” may actually be a star system comprising two or more stars. That is very hard to detect as they’re too close together, but we have some workarounds.
For example, we can take advantage of eclipsing binaries, where the stars in the star system at just the right angle that some stars block the others in the same system. To find them, we have to find periodic dips of light. If the dips take turns reasonably and do not look like it’s from a planet, we can conclude that the “star” consists of two or more stars close together.
Exoplanets
So, after discovering some stars, finding out about any exoplanet surrounding them is also essential. The bad news: Exoplanets are very dim, and most of their light is from their host stars. However, there is the good news: There are still 5 primary ways (according to this article by NASA) to look for planets beyond our Solar System:
- Transit
- Radial Velocity
- Astrometry
- Direct Imaging
- Gravitational Microlensing
Let’s talk about them one by one.
Transit
Have you ever seen a solar eclipse, Mercury transit, or Venus transit? If you have, you probably know how transit helps us discover exoplanets.
When a planet passes right between the star and us, the light from the star will fade away a little bit from our point of view. Although this is insignificant because of how small the planet is, that’s what astronomers want to find. If periodic dips are observed, and it’s confirmed not to be interference or any fake signs, it’s most likely an exoplanet.
Image Credit: Canva, NASA’s Eyes
However, if multiple planets are in the same planetary system, messy signals will be observed as those planets have different orbital speeds and distances. Despite the mess, the astronomers can still filter the dips and distinguish that from fake signals.
Although the transit method can only find exoplanets from a very certain angle, it occupies more than 76% of all exoplanet discoveries to date.
Radial Velocity
First, you’ll need to understand one thing — the center of a planetary system is not the center of the star. Don’t ignore the planets — they have gravitational effects, hence their mass. The planet and the star orbit their center of mass, so the star wobbles in the planetary system.
At this point, you may think that the effects are meager, so it won’t be detected. But the opposite is true with the help of the Doppler Effect.
As the distance between the object and the observer increases, the light from it shifts toward the red end of the spectrum. This is a redshift. Oppositely, if the object gets closer to the observer, a blueshift will occur because the light from it moves toward the blue end of the spectrum.
Image Credit: Canva
When the star wobbles, the wavelength from it changes. Although this is a very weak signal, it can be detected by sensitive spectroscopes. It is also the second-most successful way in finding an exoplanet, occupying 19% of all planets beyond the Solar System to date.
Astrometry
The astrometry method works the same way as the radial velocity method just above. However, its detection is in a different approach. Instead of looking for minuscule wavelength change, the astronomers search for the change in position compared to other stars.
Although it’s not successful with only one exoplanet found from this method, it is relatively easy to understand if you understand the Doppler Effect.
Direct Imaging
Exoplanets are faint, but do you know that astronomers can directly take photos of them? Well, they use some light-blockers to filter out the glare of the host star.
That light-filtering can help us see the faraway planet better and possibly, assist in taking photos.
Gravitational Microlensing
There is still one way to detect exoplanets from light-years away by observing the planet’s gravitational effects by lensing.
Anything with mass bends light and spacetime due to gravity. That’s how gravitational lensing works. Therefore, when a planet is in front of a distant star, it bends the light like a magnifier. That will be observed as a sign of a potential planet.
Black Holes
Another type of hard-to-find celestial objects are black holes. They absorb everything on their way, and even light cannot escape once past the event horizon. Therefore, direct observations can’t be made, and we must rely on indirect signs. But, they can be quite significant.
If a star gets too close to a black hole, it will suffer from enormous tidal forces and turn into a teardrop-shaped star. There may also be some unusual fluctuations that the direct observations cannot explain. These are telltale signs that a black hole exists on the star system, especially if both criteria are met.
Moreover, NASA published an image from a black hole back in April 2019. But, it is actually not the singularity at the center of the black hole — it’s the accretion disk that surrounds the event horizon.
Other Objects
Well, there are other celestial objects that astronomers can find. For instance, we can discover pulsars by observing their poles, which emits a lot of radiation. Moreover, we can see nebulas and galaxies either through direct observation of their stars or supernovas that flare them into sight.
Conclusion
So, we’ve talked about how to find celestial objects in this article. The ways to find stars, exoplanets, and black holes are very bizarre, and you can check out the references for more resources.
References and Credits
- CrashCourse. (2015, October 1). Binary and Multiple Stars: Crash Course Astronomy #34 – YouTube. Retrieved February 24, 2021, from https://www.youtube.com/watch?v=pIFiCLhJmig
- (n.d.). 5 Ways to Find a Planet | Explore – Exoplanet Exploration: Planets Beyond our Solar System. Retrieved February 24, 2021, from https://exoplanets.nasa.gov/alien-worlds/ways-to-find-a-planet/
- (n.d.). Exoplanet Exploration: Planets Beyond our Solar System. Retrieved February 24, 2021, from https://exoplanets.nasa.gov/
- National Geographic. (2019, March 7). Exoplanets 101 | National Geographic – YouTube. Retrieved February 24, 2021, from https://www.youtube.com/watch?v=EUU0-ZpFoK4
- (2016, January 25). How to find and study a black hole — ScienceDaily. Retrieved February 24, 2021, from https://www.sciencedaily.com/releases/2016/01/160125115236.htm