by Brigit » Sun Dec 01, 2024 1:09 am
Brigit says »
Feb 03, 2023
"The first question is "What type of star is HR 8799?"
Well let me help you Paulina. "The star's spectral type is...written as kA5 hF0 mA5 V; λ Boo."
"And what instruments and what wavelengths were used to observe it?"
After it was discovered using the Keck and Gemini in 2008, some of Hubble's old images from 1998 were re-examined and earlier positions of the planets were affirmed.
In 2009 the Spitzer space telescope looked at it in IR and reported debris disks inside and outside the orbits of the planets.
In 2010 the Hale Telescope was used to show that the system could be observed using a much smaller visible light telescope.
The Palomar Observatory looked at it in 2012 and determined that the planets, all four, were of quite different compositions.
Chandra X-ray observations showed "weak magnetic activity" and also higher X-ray readings than an A-type star.
ALMA looked at HR 8799 in 2016 and 2018 and gave a much more detailed description of the inner dust belt and the outer debris belt.
And the JWST observed it as well.
"What is that global stellar emission, and what is triggering it?"
That variability of the star and the brightening of the surrounding materials is a mystery.
"Are these orbiting companions, or are they gas giants "
The objects orbiting this very young star are uncooperative in their enormous sizes, varied compositions, and seemingly stable orbits. JWST claimed to have ruled out that they are brown dwarfs but there is some question.
"or have there been corrections to the images, to obtain a modelled result of circular movement around the central star ? Or any other modifications that have been incorporated into the images ?"
These are directly observed in the visible frequencies. Sound as a pound!
"Are there faint indications of nested shells in the image ?"
SAFIRE might like to know that too.
"Do the planetary orbits have resonances ?"
That can be found on Wikipedia. It is not my thing, but some of the resonances are looking slightly questionable.
"All sincere questions, btw. I miss Stephen Smith."
I miss Wal Thornhill so much, who went to the next life right after this post, and I miss Stephen Smith. It's been a real journey and privilege learning from Dave and Stuart Talbott, R V D Sluijs, Mel Acheson, Don Scott, Cj Ransom, Michael Armstrong, and David Drew, along with so many others.
Brigit says »
Feb 03, 2023
[i]"The first question is "What type of star is HR 8799?"[/i]
Well let me help you Paulina. "The star's spectral type is...written as [b]kA5 hF0 mA5 V; λ Boo[/b]."
[i]"And what instruments and what wavelengths were used to observe it?"[/i]
After it was discovered using the Keck and Gemini in 2008, some of Hubble's old images from 1998 were re-examined and earlier positions of the planets were affirmed.
In 2009 the Spitzer space telescope looked at it in IR and reported debris disks inside and outside the orbits of the planets.
In 2010 the Hale Telescope was used to show that the system could be observed using a much smaller visible light telescope.
The Palomar Observatory looked at it in 2012 and determined that the planets, all four, were of quite different compositions.
Chandra X-ray observations showed "weak magnetic activity" and also higher X-ray readings than an A-type star.
ALMA looked at HR 8799 in 2016 and 2018 and gave a much more detailed description of the inner dust belt and the outer debris belt.
And the JWST observed it as well.
[i]"What is that global stellar emission, and what is triggering it?"[/i]
That variability of the star and the brightening of the surrounding materials is a mystery.
[i]"Are these orbiting companions, or are they gas giants "[/i]
The objects orbiting [i]this very young star [/i]are uncooperative in their enormous sizes, varied compositions, and seemingly stable orbits. JWST [i]claimed[/i] to have ruled out that they are brown dwarfs but there is some question.
[i]"or have there been corrections to the images, to obtain a modelled result of circular movement around the central star ? Or any other modifications that have been incorporated into the images ?"[/i]
These are directly observed in the visible frequencies. Sound as a pound!
[i]"Are there faint indications of nested shells in the image ?"[/i]
SAFIRE might like to know that too.
[i]"Do the planetary orbits have resonances ?"[/i]
That can be found on Wikipedia. It is not my thing, but some of the resonances are looking slightly questionable.
[i]"All sincere questions, btw. I miss Stephen Smith."[/i]
I miss Wal Thornhill so much, who went to the next life right after this post, and I miss Stephen Smith. It's been a real journey and privilege learning from Dave and Stuart Talbott, R V D Sluijs, Mel Acheson, Don Scott, Cj Ransom, Michael Armstrong, and David Drew, along with so many others.