55
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Where did TRAPPIST-1a go?
To add to Rob's answer, I wanted to expand on where this naming convention comes from.
The International Astronomical Union (IAU) is the organization which generally sets conventions and definitions. ...
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54
votes
Is there any planet bigger than a star?
The answer depends on whether you mean is any planet bigger than any star (Case 1), or whether the planet and star have to be in the same system and have been discovered/measured (Case 2), rather than ...
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50
votes
Is it possible for planetary rings to be perpendicular (or near perpendicular) to the planet's orbit around the host star?
Yes, the plane of the rings of Uranus are at about 98 degrees to the plane of its orbit around the Sun.
This means that the ring system looks as in your picture twice per orbit. As the planet orbits ...
- 163k
42
votes
Accepted
Where did TRAPPIST-1a go?
The convention for planetary naming is that the closest planet to the star (if multiple planets are found at the same time) is named "star"b, then "star"c and so on. As correctly pointed out by Zephyr,...
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42
votes
Accepted
Why are most discovered exoplanets heavier than Earth?
There are a number of methods of detecting exoplanets, but all of them favour detection of larger planets over smaller ones, albeit for slightly different definitions of large:
Radial velocity ...
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38
votes
Do celestial objects need to be big to have liquid water on their surfaces?
Liquid water can't exist in a vacuum. If there is no pressure, then the boiling point will drop to the freezing point and so there will either be ice or water vapour.
And if the world is "small&...
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36
votes
Accepted
Why did we discover so many exoplanets in this specific part of the sky?
Yes, that's been the observation spot of the Kepler telescope. It observed the spot for 9 years with detailed photometry in order to capture all the transits it could find in that region. A prolonged ...
- 21.4k
31
votes
Is Jupiter still an anomaly?
A recent study indicates that Cold Jupiters similar to Saturn and Jupiter greatly outnumber Hot Jupiters. The authors studied 18 years worth of data to find long-period exoplanets, that is planets far ...
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31
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Is it possible for planetary rings to be perpendicular (or near perpendicular) to the planet's orbit around the host star?
I posted a few animations, just to make sure :) The image is hopefully obviously not to scale.
This is possible:
and is, in fact, not far from what Uranus is doing.
The animation above was produced ...
- 411
30
votes
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Exoplanet dip in transit light curve when the planet passes behind the star
Just before the planet goes behind the star, we see the light directly from the star as well as the light reflected from the planet's surface. When the planet is behind the star, we no longer see the ...
- 16.7k
29
votes
Accepted
How was Trappist-1 discovered?
The star at the center of TRAPPIST-1 is called 2MASS J23062928-0502285. It was discovered by the Two Micron All-Sky Survey (2MASS), which imaged the whole sky in the infrared between 1997 and 2001. ...
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28
votes
Why there are no terrestrial planets with a subsurface ocean?
Some hypothesize that the Earth did have a subsurface ocean during the Cryogenian period, which lasted from 720 to 635 million years ago. The Cryogenian saw the two greatest known ice ages in the ...
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28
votes
Why can't we build a huge stationary optical telescope inside a depression similar to the FAST radio telescope?
The surfaces of telescopes need to be configured to a fraction of a wavelength. If one is working in the FAST wavelength range of 10 cm to metres, then that is a relatively straightforward engineering ...
- 163k
26
votes
Accepted
Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?
No, not with the current or any projected "next-generation" of telescopes.
The problem isn't dust, it is distance. To put it in context, you can consider a scale model of the universe. ...
- 129k
25
votes
Accepted
What's the difference between an exoplanetary transit and eclipse?
A star usually is larger than its planet, and that's what they refer to in this instance. Further in the text they explain that they mean the star eclipsing the planet:
An eclipse occurs when an ...
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23
votes
Are there any planets or moons denser than Earth?
I feel it's a cheap answer but heavy Jupiters can get much denser than Earth because planets with Jupiter's mass stop adding size as they add more mass. A planet with Jupiter's size and 10-12 times ...
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23
votes
Which of the planets would be detected if they were exoplanets?
The distance moduli at 5, 500, 50,000 and 5,000,000 are -4.1, 5.9, 15.9 and 25.9 respectively. We add that to the absolute visual magnitude of the Sun, 4.8, to get apparent magnitudes of 0.7, 10.7, 20....
- 163k
23
votes
Do these results mean that I have found this exoplanet?
It could be an exoplanet transit (but that doesn't mean it is).
The star in question, TIC92352620, is an F8 main sequence star, which would be much larger than any plausible planet. If a planet ...
- 163k
23
votes
Accepted
Could it be possible to detect planets from stars that went supernova through the resulting nebula shape?
The escape speed of a big planet like Jupiter is about 60 km/s.
The speed of the ejecta from a supernova explosion is something like $10^4$ km/s.
i.e. Jupiter would have little discernable ...
- 163k
21
votes
Accepted
Is the measurement of distance and position of remote celestial bodies accurate?
Large masses can bend light, but space is largely empty. The light from distant stars and galaxies rarely passes close enough to another star or galaxy to have deviated. On the few occasions when it ...
- 129k
21
votes
Could rogue planets harbor life?
There's also the possibility that a rogue giant planet may have a moon with a subsurface ocean of liquid water due to tidal heating in an orbit close enough to its parent planet. E.g. if Jupiter was a ...
- 1,548
21
votes
Accepted
Why use a large separate starshade instead of an occulting disk?
TL;DR: The Sun is well-resolved in small telescopes so a focal plane occulter works well. Other stars are not resolved (except in a few exciting cases using interferometry) so an internal blocking ...
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20
votes
Accepted
What is sin i in this graph and why is it there?
If you discover an exoplanet via the Doppler (radial velocity) method, then the amplitude of the radial velocity variations depends on the inclination, $i,$ of the exoplanet's orbital axis with ...
- 163k
19
votes
Accepted
Is there a gas giant orbiting TRAPPIST-1?
No such planet has been announced as having been discovered. The paper only shows evidence for the 7 (really 6 because the 7th can't be officially confirmed with only 1 observation) terrestrial ...
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19
votes
Accepted
Can exoplanets be found using neutrino detectors?
The answer is presumably no.
Let's assume that the nearest possible exoplanet is in the Proxima Centauri system, and it presents an electron antineutrino luminosity identical to that of Earth. The ...
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19
votes
Accepted
Are stars near the ecliptic the only stars from which Earth would appear to transit the Sun?
Yes. Heller and Pudritz 2016 define an Earth transit zone (ETZ) within 0.26° of the ecliptic and a restricted ETZ (rETZ) half as wide.
They also list 82 Sun-like stars in the rETZ and within 1 ...
- 18.8k
19
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Is there enough data in light coming from distant exoplanets for Earth-orbiting telescopes to take a high-resolution photo of it?
There is a fundamental limit to resolution called the "diffraction limit" that depends on three things:
The angular size of the feature you're trying to resolve,
The wavelength of light you'...
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18
votes
How was Trappist-1 discovered?
Trappist-1 was first catalogued by the 2MASS survey about 17 years ago and has the catalogue number 2MASS J23062928-0502285.
It was identified as an ultra- low-mass star with a spectral type of M7.5 ...
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