Planet 9 and beyond Flashcards
In what year was planet nine first proposed
By whom
By did they infer it?
In 2014 in a letter to the journal Nature
Chad Trujillo and Scott Sheppard
Inferred it from similarities in the orbits of Sedna and 2012 VP113
Trujillo and Sheppard analyzed the orbits of twelve trans-Neptunian objects (TNOs) with perihelia greater than 30 AU and semi-major axes greater than 150 AU, and found they had a clustering of orbital characteristics, particularly their arguments of perihelion (which indicates the orientation of elliptical orbits within their orbital planes).
Who were the second group of astronomers to support the Planet Nine hypothesis
In what year.
What have they nicknamed it
why?
What specifically made it an attractive proposition
(name three)
Konstantin Batygin and Michael Brown (Caltech) in 2016
‘Perturber’ or ‘Phattie’ (when they’re talking to each other)
They explained how a massive planet would be the best explanation for the similarities in orbits of six distant objects.
- The clustering of perihalia and orbital poles of the objects, but also
- the high perihelion of Sedna and 2012 VP113
- and tilt of the Sun’s rotation axis
What is Planet Nine hypothesised as being?
Why is it where it is (give three explanations)
A super Earth, 10 x the mass of earth and twice the diameter
- B&B proposed it was a primordial giant planet core that was ejected from its initial orbit by an encounter with Jupiter during the nebular epoch of the Solar System and was later perturbed into a stable orbit by a distant encounter with a passing star or by the gas nebula.
2 Alternatively it was captured from another star during a close encounter
3 Or it formed on a very distant circular orbit, which became eccentric when perturbed by an encounter with another star
Why is Planet Nine not considered to have the same diameter as Neptune despite its hypothesised size
Specifically….
Its been excluded by previous surveys
The Wide Field Infrared Survey (WISE) in 2009 allowed for Neptune sized objects beyond 700 AU
and a 2014 study has ruled out Jupiter Mass objects out to 26,000 AU
What first got people thinking about the potential for another planet
The discovery of Sedna in 2004, which was found to have a very eccentric orbit, and suggested that something had perturbed it away from the Kuiper belt… this could have been an unknown planet or a random star passing near the solar system
Which survey in 2017 questioned the likelihood of Planet Nine
What did they cite?
What later paper suggested the issues above were not correct
Outer Solar System Survey (OSSOS)
suggest the clustering is a mix of observation bias and small number statistics
However, a paper by Carlos and Raul de la Fuente Marcos show that the distribution of nodal distances (where the ETNOs orbits cross the plain of the solar system) are correlated, which is unlikely to be due to observational bias. Instead it is consistent with a large planet with a semi-major axis of 300-400 AU
Which spin-orbit misalignment has been a long standing puzzle.
The Sun’s axis of rotation is about 6 degrees from the orbital plan of the giant planets
Computer simulations suggest it can be explained by gravitational torque exerted by Planet Nine - although other explanations have been proposed.
Why might Planet Nine not be very easy to see with a telescope
Which telescope has the best chance?
How bright would it be compared to Pluto
It would have an apparent magniture of greater than 22 - at least 600 x fainter than Pluto
But if it is perihelion then it can be found with existing images
Else, it would require the largest possible telescopes, though some could.
Statistically it is more likely to be closer to Apehelion as planets move slower as they get further out
As it is predicted to be visible in the Northern Hemisphere, the Subaru Telescope is being used, as it has a big enough apeture to see faint objects, but also a wide field of view to look quickly.
Why has a Planet Ten been hypothesised?
By whom, when?
It comes down to the orbital inclination of Kuiper Belt objects
most KBO’s inclinations average out to the ‘invariable plane of the solar system’
But the orbits of the most distant KBOs tilt away from this plan by an average of 8 degree, suggesting they are being perturbed
It was proposed by Kat Volk and Renu Malhotra from the University of Arizona in 2017
How far away is Planet Ten hypothesised to be?
How big is it?
about 60 AU
Mars sized
Why might Planet Ten not have been found (assuming it exists)
If it does, would telescope offers the best chance (and when)
How many KBOs is that expected to find compared to now
It could be in the galactic plane, or very dim (less likely), or it might have been bad luck its not been found (again unlikely)
But it should be found by the Large Synoptic Survey Telescope (LSST) under construction in Chile and ready by 2023
The LSST is expected to bring the number of observed KBOs from currently about 2,000 to 40,000
When was the first confirmed detection of an exoplanet
What was it orbiting?
Called?
For mega kudos, what is the name of all three planets in this system
How far away is this system?
1992
a Pulsar called PSR B1257 (PSR stands for Pulsating Source of Radio) the other bits of the name come from its right ascension and degrees of declination
Draugr, Poltergeist and Phobetor
about 2300 lyr
Which star was the first main sequence star known to have been found with a planet
When?
What type of planet is it?
51 Pegasi
discovered in 1995
The planet is called 51 Pegasi b (and unofficially called Dimidium)
It is a hot jupiter
Which system described in a study released in May 2017 is famous for its many exoplanets tightly packed into stable orbits?
How many planets? (and how many within the habitable zone)
However, what will make life difficult?
What type of star?
How far away?
TRAPPIST-1
7 planets (3 in the HZ) - all close to earth size
But they are all titally locked to the star - and also lets not forget the radiation and solar flares that post more of a risk being so close to the star
Ultra-cool dwarf star
39.5 lyrs away
What is the argument of perihelion, that is important in evidence for Planet 9
It is the angle above the plane of the solar system that the object is at when it reaches perihelion
