Radial Velocity Detections

As important as their discovery was, “zombie” planets orbiting neutron stars did not address the important issue of planets

formed around stable main sequence stars - places where life might exist today

Doppler Technique Proposed in 1952 (O. Struve)

Success in 1995

THE TIME: June 1995 THE SCENE: Gordon Conference on Origins of Solar Systems

THE PLACE: Me. standing in front of a poster by Geoff Marcy dealing with Doppler measurements of stars

THE THOUGHTS: “Wow! 13 m/s precision. At this rate we’ll have detected massive planets orbiting other stars within 10 years!”

THE REALITY: Nov. 1995 Nature, Mayor & Queloz report detection of Jupiter-like planet orbiting 51 Peg (…..so what do I know!…..). 2019 they get a Nobel Prize in Physics for their discovery

!!

Velocity Curve Phased Velocity Curve

Many people, like Marcy & Co. were looking for Jovian-mass planets at Jupiter-like Distances.

51 Peg was orbiting its star in a small orbit - it was a “hot Jupiter”. Many more soon followed.

!!

Multi-planet Systems were found

! !

Planets in Disk Systems were found

!

The list of RV Planets as of 2007. A table like this would be too big today to display on a single slide.

For all the details, go to http://exoplanets.org/ and the table:

http://exoplanets.org/table/

RV studies are biased in favor of “hot Jupiters”. But why should they exist at all?

They are not beyond the “snow/frost” line!

m23

m1 + m2

<<m1

!

⎛

⎝⎜⎜

⎞

⎠⎟⎟

2 sin3 i = P2πG

v1r3

m2 sin i = m1

23 P

2πG⎛⎝⎜

⎞⎠⎟

13

v1r

A few months in the life of RV planet discoveries

there are now 5 known

there are now 3 known

there are now 4 known

there are now 2 known

as of March 5, 2019:

6-8 Earth-mass planet a "super-Earth" orbiting GJ 876 (along with 2 Jupiters) - precision by

2005 ~3.5 m/s - slower than a jogging human!

As of 2014, the velocity precisions are not all that much better, but should improve with the introduction of laser

combs as a velocity reference. The near-term goal is 1 m/s, although some people are looking for ~20 cm/s.

Fast-Foreward to 2016:Proxima Centauri b

"A terrestrial planet candidate in a temperate orbitaround Proxima Centauri" Anglada-Escude et al. 2016, Nature, 536, 437.

Okay, where did all the “Hot Jupiters” come from?

Cannot form inside the snow/frost line

Formed further out & migrated inward A nice “little” (8 MB) of one example, by Phil Armitage, U Colorado

NOTE:

If terrestrial planets all form closer to the star than jovian ones, by the time the jovian one reaches 0.2 AU, all the terrestrial ones will have been swallowed by the star.

In this case - Perhaps No TPs as we understand them

start

Also, planetary migration

“Nice Model”

“Grand Tack”

Fischer & Valenti 2005 (ApJ, 622, 1102)

- 836 citations as of April 1, 2017, 2011

a 2008 version....

We will return to this soon....

Example of precision of one of the RV searches:HIRES on Keck

1 m/s