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37 votes
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Kepler space telescope undetected planets

That's right. The inclination of the orbital plane around stars is considered to be random throughout the galaxy, thus the planets we can detect by the transit method is just a tiny fraction of the ...
Swike's user avatar
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17 votes

How does NASA figure out orbital period and mass data for planets and other celestial bodies?

I'll take a small exception to @JamesK's answer about what NASA does and doesn't do. The Jet Propulsion Laboratory is part of NASA and one of the many invaluable contributions they've made to ...
uhoh's user avatar
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16 votes
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"Periapsis" or "Periastron"?

No. These words are English, not Greek. "Periapsis" means the point on the orbit when the two bodies are at their closest. It doesn't matter if this good Greek or bad Greek, it is correct ...
James K's user avatar
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11 votes
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Why does Kepler's "Big Picture" of comet 67P look so strange? And what is the significance?

One thing to keep in mind is that the Kepler instrument is not a telescope like Hubble. It is a photometer and though it uses CCDs to look at the sky, it doesn't return a picture in the usual sense. ...
Dave's user avatar
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10 votes

According to my calculations Jupiter's moons do not follow Kepler's 3rd law - Why is that?

Kepler's third law is that $R^3/P^2$ is a constant. However it is not a universal constant; it depends on the mass of the body that is being orbited. $$\frac{R^3}{P^2} \simeq \frac{GM}{4\pi^2},$$ ...
ProfRob's user avatar
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8 votes

Kepler space telescope undetected planets

Yes. The probability of a transit taking place is something like $r/a$, where $r$ is the stellar radius and $a$ is the radius of the planetary orbit. If you assume that planet orbits are randomly ...
ProfRob's user avatar
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8 votes
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Where can I find online-available datasets for the KIC 8462852?

I would suggest to follow the instructions given here: NASA how to get Kepler lightcurves There you find the links to two archives, where you can enter the name of the source "KIC 8462852" ...
SpaceCore's user avatar
  • 3,441
7 votes

How does NASA figure out orbital period and mass data for planets and other celestial bodies?

Yes, NASA uses indeed Kepler's 3rd law to calculate the orbital periods of planets and other objects in the solar system. If you go to NASA's Horizons Website and generate orbital data for a planet ...
Thomas's user avatar
  • 3,504
6 votes

What caused instant jumps and exactly flat periods in Kepler's light curves?

There are two separate points of interest you're looking at so I'll separate this into sections. Sudden Drop at Day 1559 As near as I can tell, this is the result of a quarterly roll of the ...
zephyr's user avatar
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6 votes

Are gas giants actually rare?

There is an observational bias and it is taken into account when you see inferences about planet frequency. The methods to find planets are inherently biased towards finding large, close-in planets. ...
ProfRob's user avatar
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6 votes
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How did Kepler come to the potencies in his Third Law?

If you plot the log of the period against the log of the semi-major axis then it is obvious that $P^2 \propto a^3$. Any other power law relationship simply wouldn't fit. The following passage (from ...
ProfRob's user avatar
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6 votes

"Periapsis" or "Periastron"?

A disclaimer first - I am not an astronomer, but I am a Greek with some ancient Greek language knowledge. "Periapsis" is definitely ancient Greek and it derives from peri+apsi (περί+αψη). ...
Panos's user avatar
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6 votes
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Calculate eccentric anomaly using Kepler's equation

The difference in values seems to be only $2\pi$, or one complete turn. So your value seems to be correct. Here is my calculation: Jupiter was at perihelion on March 17th 2011, which is 2672 days ...
James K's user avatar
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5 votes
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Unbelievably high masses/ densities in NASA website data

Starting from the index you mentioned, I clicked through the links for some individual planets, which in turn link to discovery papers or other relevant observations. For planets around Kepler-23, -24,...
HDE 226868's user avatar
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5 votes

Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

The maths says that the semi-major axis is not a good measure of average distance for high eccentricity (elliptical) orbits. There are basically two ways to measure this : (1) an average over the ...
StephenG - Help Ukraine's user avatar
5 votes
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Keplerian Elements for Approximate Positions of the Major Planets

I believe you are right, this is extracted from the "Explantory supplement to the Astronomical Almanac (2006?)" (although it might date back to the 1960s...) For example a similar PDF ...
James K's user avatar
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5 votes

Whether the comet is moving in an elliptical or hyperbolic orbit around the sun?

This might not be so hard after all. Below I show the math for the analytical solution for a Kelperian orbit; the catch is that it's only analytical for $t(\theta)$ and not $\theta(t)$ but that ...
uhoh's user avatar
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4 votes

Just how "locked" are resonant-chains of exoplanets thought to be? (e.g. K2-138 and TOI-178)

Short Answer: MMR (Mean Motion Resonance) chains seem to be mostly unstable over the lifetime of a planetary system, since we suspect most planetary systems begin in some resonance lock, but we ...
Connor Garcia's user avatar
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4 votes

Can one approximate the semi-major axis of an orbit as the average orbital distance for eccentric orbits?

Just to provide an analytical formula for @uhoh's correct time-averaged distance, here the derivation of $\langle r\rangle_t=1+\epsilon^2/2$: $$a=1 \qquad c=e\qquad b=\sqrt{1-e^2}\\ \vec{r}=(\cos \...
Markus Schmassmann's user avatar
4 votes

Kepler's second law of motion

That is not correct. The area is the total area between the two radius lines, so there is a curved side. Imagine you have two points almost 180 degrees from each other. Using just a triangle, the ...
SE - stop firing the good guys's user avatar
4 votes
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What does "forward facing" mean for space telescopes?

This can best be described by two slides from this presentation. "Forward-facing" implies looking towards Earth in the spacecraft's orbit, in the direction of the spacecraft's velocity vector: "...
HDE 226868's user avatar
  • 36.6k
4 votes

Has star KIC 8462852's 3 year long Kepler-fading continued after the primary Kepler mission ended?

Well "if no known astrophysical model can explain it" then nobody told Wright & Sigurdsson (2016) who, cognisant of Montet & Simon's results, explore a number of astrophysical models. They ...
ProfRob's user avatar
  • 155k
4 votes

Getting light curves from Kepler/K2

Go to the Kepler/K2 MAST database https://archive.stsci.edu/kepler/data_search/search.php or https://archive.stsci.edu/k2/epic/search.php Search on a temperature ($T_{\rm eff}$) range: e.g. for K-...
ProfRob's user avatar
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4 votes
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Data to "check" Kepler’s first law

Great project! and welcome to Stack Exchange. I'll post a short answer but I think someone can add a more detailed, thorough and insightful answer. I think that website is not well suited, so I'll ...
uhoh's user avatar
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3 votes
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Hot and "warm" Jupiters expelling terrestrial planets?

It's not proof that they've ejected other inner planets, because there are plenty of other explanations for why we haven't observed companions. Steffen et al. (2012) analyzed Kepler data - likely some ...
HDE 226868's user avatar
  • 36.6k
3 votes
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What telescopes have observed anomalies in the light curve of Tabby's star, KIC 8462852?

I do not know whether complimentary observations of the light curve are being done, but I will try to answer the rest of the question. Is it easy to observe the light curve with ground-based ...
Alex's user avatar
  • 2,285
3 votes

Where can I download processed data of the Kepler telescope?

What you are looking for is here. http://archive.stsci.edu/kepler/search_retrieve.html This one is good for exoplanet light-curves https://exo.mast.stsci.edu/
Dean Pitts's user avatar
3 votes

How to find the mass of a planet not knowing the gravitational constant?

How can I do this by not knowing the gravitational constant? Sarcasm: You could do what Henry Cavendish did, which was to measure how the horizontal deflection rather heavy balls separated ...
David Hammen's user avatar
  • 34.1k
3 votes

Data to "check" Kepler’s first law

Kepler's first law is that a planet moves in an ellipse with the sun at one focus. Your equation is that of an ellipse about the focus, so, you have proven Kepler's first law. The $\varphi$ is what ...
W H G's user avatar
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