# Plenty of wet, rocky planets

• marcus
In summary, the author argues that, due to the inclination of the planet's orbit, indirect evidence suggests that wet, rocky planets are common. Furthermore, he states that if one knows the radius of the star and the period of the planet, they can use those values to determine the mass of the planet. However, he notes that there are a few cases where the planet's inclination is zero and thus one cannot determine its mass using these methods.

#### marcus

Gold Member
Dearly Missed
http://arxiv.org/abs/astro-ph/0209383

"Much indirect evidence suggests that wet, rocky planets are common."

fairly recent article by Lineweaver (September 2002)

Hmm, interesting. Just two questions for now. What does he mean by the i in M*sin(i)? And what's the signifigance of M*sin(i). Afraid I've not come across this before.

Originally posted by Lonewolf
Hmm, interesting. Just two questions for now. What does he mean by the i in M*sin(i)? And what's the signifigance of M*sin(i). Afraid I've not come across this before.

this is a standard term in the exoplanet search (exosolar planet search) where i is the inclination of the orbit relative to the observer

in most cases the planet is detected by wobble, changes in the radial speed of the star, by doppler effect

If the observer is in the plane of the star and planet two-body motion (inclination = 0) then one measures the whole wobble

if the inclination is 90 degrees one wouild not see any wobble

in general the inclination is unknown and one sees a fraction of the wobble which is sine(inclination).

therefore one systematically underestimates the mass of the planet, in fact ones estimate of the mass is only sin(i) times the mass, where the inclination is an unknown number between zero and one

and so the tables show sin(i)M because one cannot actually say anything about M itself

as parttime astronomer you will see that the mass of the star itself is told by the color etc. -----so knowing the period will tell the distance from the star and knowing the wobblespeed and the distance will tell the mass of the planet----but one only knows sine(inclination) X wobblespeed

EXCEPT in a few cases where the planet actually passes in front of the disk of the star and notches the lightcurve----there are a few of these inclination=0 cases where one has two handles on the problem

## 1. What is meant by "Plenty of wet, rocky planets"?

"Plenty of wet, rocky planets" refers to the large number of planets that have been discovered and are suspected to have similar characteristics to Earth, including a rocky surface and the presence of water.

## 2. How do scientists determine if a planet is wet and rocky?

Scientists use a variety of methods to determine a planet's composition, including measurements of its mass, size, and distance from its star. They also use spectroscopy, which analyzes the light reflected off a planet's surface to identify the presence of certain molecules, such as water.

## 3. Why is the presence of water important for a planet to potentially support life?

Water is essential for life as we know it. It is a universal solvent, meaning it can dissolve and transport important nutrients and molecules necessary for living organisms. It also helps regulate temperature and provides a habitat for many organisms.

## 4. Are all wet, rocky planets capable of supporting life?

While the presence of water is a crucial factor for life, it is not the only requirement. A planet must also have a suitable atmosphere, a stable climate, and other necessary conditions in order to support life. Additionally, scientists are still studying and discovering the potential for life in extreme environments, such as on planets with vastly different compositions than Earth.

## 5. How does the discovery of wet, rocky planets impact our understanding of the universe?

The discovery of wet, rocky planets helps us expand our understanding of the diversity of planets and their potential to support life in the universe. It also raises questions about the origins of life and the likelihood of finding other habitable worlds beyond our own solar system.

• Astronomy and Astrophysics
Replies
5
Views
1K
• Astronomy and Astrophysics
Replies
16
Views
3K
• Sci-Fi Writing and World Building
Replies
3
Views
915
• Astronomy and Astrophysics
Replies
31
Views
5K
• Astronomy and Astrophysics
Replies
1
Views
3K
• Astronomy and Astrophysics
Replies
3
Views
1K
• Astronomy and Astrophysics
Replies
14
Views
9K
• Sci-Fi Writing and World Building
Replies
21
Views
734
• Astronomy and Astrophysics
Replies
2
Views
2K
• Earth Sciences
Replies
6
Views
3K