# The current planet count stands at 490

• amalmirando
In summary, scientists are not 100% sure that all 490 planets that they have identified are actually planets. They use methods such as radial velocity and light curves to determine if an object is a planet. However, they know that there are many planets that they are missing due to their angle of observation. They estimate that there are hundreds more planets right in our own neighbourhood.
amalmirando
The current planet count stands at 490 but can scientists gurantee 100% that they are planets. For instance, isn't it possible to identify a star passing in front of another star (binary) when looking at the light curve?

A few of the large jupiter-like planets are big enough that they might be brown-dwarfs, but most of them are planets. From the light curves (or radial velocities) you can deduce some of the properties of the object and figure out what it is. Also, generally, there would be lots of particular characteristics that its just a binary star system.

amalmirando said:
but can scientists gurantee 100%?

Scientists can't guarantee anything 100%.

amalmirando said:
The current planet count stands at 490 but can scientists gurantee 100% that they are planets. For instance, isn't it possible to identify a star passing in front of another star (binary) when looking at the light curve?
For a binary star system, there would be two minima in the light (magnitude) of the star - corresponding to passage of one star in front, and then again when the star passes behind the other. This assumes that the stars revolve such that the line of observation passes through them.

A planet-star system would have one minimum, assuming that the rotational plane is parallel (or nearly so) with the line of observation, i.e. that the planet passes between the star and observer.

One has to wonder how many planets are missed because we're looking perpendicular (or nearly so) to the plane of revolution.

binary star systems havnt definative charectaristics. You could also look at if the star wobbles , then you could arguye that a gravitational force from a planet could be their.

*have

Astronuc said:
One has to wonder how many planets are missed because we're looking perpendicular (or nearly so) to the plane of revolution.

Assuming angle between axes of rotation for planetary systems and galactic plane is completely random, it should be relatively easy to estimate number of those not seen just considering geometry of the systems involved. No idea if the assumption holds.

thanks a lot guys...

Borek said:
Assuming angle between axes of rotation for planetary systems and galactic plane is completely random, it should be relatively easy to estimate number of those not seen just considering geometry of the systems involved. No idea if the assumption holds.

And it would be huge. The angle between our line of sight and the system's plane must be within a tiny fraction of a minute of a degree. Which means the transiting method is missing 99.99%+ of the planets. That's why we use many other methods.

Transiting misses a lot. But what it does catch is great, because it works on much smaller bodies than wobble and other methods.

It means there could be millions of planets still hiding from us ...

Of course there are. There are hundreds of billions of stars in the Milky Way Galaxy. Most of these stars have never even been catalog and many of them surely have planets.

Of course there are. There are hundreds of billions of stars in the Milky Way Galaxy. Most of these stars have never even been catalog and many of them surely have planets.
That's not the point; the point is this:

We've spotted several hundred stars with planets locally.
And our techniques miss 90% of the stars with planets.
Which implies that there are hundreds more stars with planets right in our own neighbourhood.

## 1. How do scientists determine the current planet count?

Scientists determine the current planet count by using telescopes and other instruments to observe and study celestial bodies in our solar system and beyond. They look for specific characteristics, such as orbiting around a star and having enough mass to be round, to determine if a celestial body can be classified as a planet.

## 2. Is the current planet count expected to change in the future?

Yes, the current planet count is expected to change in the future as new discoveries are made and our understanding of the universe evolves. For example, in 2006, the International Astronomical Union reclassified Pluto as a "dwarf planet," reducing the planet count from 9 to 8. As technology advances and we continue to explore the universe, the planet count may continue to fluctuate.

## 3. How does the current planet count compare to previous counts?

The current planet count of 490 is significantly higher than previous counts, which were typically around 8 or 9 planets. This is due to advancements in technology and techniques for detecting and classifying celestial bodies, as well as a broadening of the definition of a planet.

## 4. Are there any new planets that have recently been discovered?

Yes, scientists are constantly discovering new planets. In fact, in February 2021, NASA's TESS mission announced the discovery of 2,200 new potential planets outside of our solar system. Additionally, the Kepler mission has confirmed over 2,800 exoplanets (planets outside of our solar system) since its launch in 2009.

## 5. How many of the 490 planets are potentially habitable?

It is difficult to determine exactly how many of the 490 planets are potentially habitable, as this depends on many factors such as the planet's distance from its star, atmosphere, and composition. However, estimates suggest that there could be hundreds of potentially habitable planets in our galaxy alone.

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