Talk:Hubble discovers 16 new planets
- Who I am: freelance science writer mputney.
- Reasons for information: I had the opportunity to hear about Dr. Sahu's discovery a week before NASA's press conference on Wednesday Oct. 4.
- Contact/Verification: Just drop a note on my talk page.
Mputney 20:38, 4 October 2006 (UTC)
The following are the notes on the reporting done for this story:
Notes from presentation given by Dr. Sahu September 21, 5pmEdit
Project: SWEEP – Sagittarius Eclipsing Extra solar Planet Search
Sag – Crowded field, in galactic center, northern sky
Searching for planets coming in front of star
The entire time, for seven days
Doubles the amount of known transiting planets (previously 10, 200 by rad. Vel., 2 by microlensing)
Ultra short period planets as well (periods around half a day) 5 less than any other period
Many large gassy ones found close to star with short periods
All found in galactic disk 2 kpc away, relatively massive stars
First attempt, none found, expected 17 – Ron Gilliland, globular cluster, very little heavy elements
Monitored star’s light curve – must be consistent with that of a planet 1/10000 would be candidates
looked at 180,000 stars, so expect to find 18
other phenomena can mimic, but can be accurately predicted. At least 50% must be planets (conservative estimate)
two of the stars bright enough for rad. Vel, in order to verify (Chili scope)
most of the candidates are like our sun (high element abundance), proving what kind of stars planets form around
on average, higher mass star means more heavy elements
Hubble instrument just recently installed (2002)
Before couldn’t see to galactic bulge
Farther and fainter than ever before
Planets equally abundant in area
Expect Jupiter sized planets, a couple smaller than Saturn
Took full year to process data
Most amount of data HST has collected in a single week
Can use data for other searches
100 billion stars out there, 6% have planets, with confidence can say 6 billion jovian planets
“The biggest surprise would be if there are no more surprises.” – Sahu
“We could answer the questions we started out with.” – Sahu
The planets are too big to form with star
Has to get trapped in the orbit
“The most complex project I have worked on.” – Sahu
Phone interview with Dr. Sahu – September 27Edit
ME: How do you know it’s not a dwarf?
SAHU: cannot rule out everything. But at least 50% have to be planets. We know how many eclipsing stars there are, estimate how many dwarfs, extrapolate from that. A majority must be planets. Found way more eclipsing objects than number of red dwarfs that were expected.
ME: What is the shortest distance of planet from the star?
SAHU: Shortest distance from star: 4.1 stellar radii, same as the ones with even larger periods, but in absolute units, .008 AU is the shortest. 740,000 miles
ME: Can you expect to confirm the rest?
SAHU: James web space telescope 2013 best chance of confirming the rest
ME: how can you be sure they are all planets?
SAHU: lots of statistical analysis. “It gives us confidence that at least a majority of them have to be planets,” would be surprised of all of them turned out to be.
Notes from Phone interview with Sara Seager September 28Edit
Radial velocity only tells us the minimum mass
Transit tells us the size and the mass, and from that we can determine the density, which is an important tool in discovering what kind of planet it is. Three of the new planets are unusual, and we can’t fit them into the standard model.
One is like Saturn. “We know it’s a planet, but it’s a crazy planet” 2/3 of it is rock. More rock and ice than our whole solar system.
Some are so big, that we can’t explain them. There has to be some sort of extra energy in its core.
It’s also easier to detect a small planet by transit than by radial velocity There are two paths you can take to learn about a planet. You can image, but the star is so bright, you can’t usually see anything. Then there is transiting. Using this, you can learn all about the planet. "This is tremendously exciting. It doubles the amount of transiting planets found." "There are lots of nasty tricks nature can pull on us." and because we can't be 100% sure of all of them "I think people will take issue with that."
The above notes were compiled and originally posted by Mputney.
Good work...Sorry I could not reply earlier. Jason Safoutin 20:53, 5 October 2006 (UTC)
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