Main Mission Status Planets Searches Links Meetings Interferometers People Outreach Usage

Planets
Pulsar Planets
Planets found by micro-lensing
Rumours of and gossip about planets
Stars currently being searched for planets
Masses, distances, periods, sizes of the Solar System planets
Comments

Planets

Planets round nearby stars

Star	Sp. Type	Period (days)	delta RV (m/s)	Mass (Mj.sin i)	Sepn (AU)	Eccn	Update
Tau Boo	F7V	3.3128	468.44	3.87	0.0462	0.015±0.01	961224
51 Peg	G2.5V	4.229 ? > 800 ?	57 ? > 30 ?	0.45 - 0.7 -	0.05 -	0.015±0.01 -	980105
Upsilon And	F8V	4.6	74	0.6	0.054	0.015±0.01	961207
Rho^1 Cnc	G8V	14.64 15-20 yr	77 -	0.8 5	0.11 -	0.05±0.01 -	961207
Rho Cor Bor	G2V	39.645±0.09	67.4±2.2	1.13	0.246±0.006	0.028±0.04	970425
16 Cyg B	G2.5V	829.4±12	44±8	1.52	1.7	0.57±0.09	961207
47 UMa	G1V	1107.6±15	48±3	2.39	2.10	0.01±0.1	961207
Lalande 21185	M2V	5.8 yr ?? ~30yr ?? > 30yr ??	- - -	0.9 ?? * 1.1 ?? * -	2.2 ?? ~11 ?? -	~0 ?? ~0 -	971205

(* = Astrometric orbit => Mass is actual mass, not (1/ sin i) )

Borderline Planets (large mass, high eccentricity)

Possible Detections

Planet or Brown Dwarf?

(* = Astrometric orbit => Mass is actual mass, not (1/ sin i) )

Pulsar planets

Planets found by micro-lensing

• 94-BLG-4 and 95-BLG-3

  The MACHO team gave a paper at the STScI Oct 96 meeting, reporting on analyses of two already reported Galactic Bulge micro-lensing events, one in 1994 (94-BLG-3), and one in 1995 (95-BLG-3).

  These were asymmetric brightenings, which can be best interpreted as due to a 5 Jupiter-mass planet 1AU from an M-dwarf for 94-BLG-4, and a 2 Jupiter-mass planet at least 5 AU from its parent star (if it was actually attached) for 95-BLG-3.

  The team say that the data is ``not sufficient to definitively establish the identification of planetary mass lenses'', and, of course, the events will not be repeated.

  But it increases the hopes for results from the improved MACHO and other programs, together with the follow-up teams such as GMAN and PLANET.

• Q0957+561 A,B

  R.E.Schild, `Microlensing Variability of the Gravitationally Lensed Quasar Q0957+561 A,B', ApJ, 464, 125, 1996

  The lightcurve of the component A presents a bump which can be interpreted as the amplification of the QSO by an object with 10^-5 M Sol located in the foreground anonymous lens galaxy (z=0.39). If it exists, it may or may not have a parent star - no evidence is available.

  Kundic et al, ApJ Letters, 455,, L5, 1996, discuss a drop in the flux from Q0957+561, and tend to discount micro-lensing for that event.

  [J. Schneider comments: the light curve due to the lensing by a parent star may be too slow (several months or a few years) to be easily seen].

  An article in the 6 July New Scientist (151, No. 2037, p15, 1996) quotes Schild as pointing out that this interpretation implies 1 million loose planets per star, a ratio which Waetherill is quoted as saying is outside current understanding of planet formation.

Rumours of and gossip about planets

Proxima Cen ? 98 Jan 05		Schultz et al have a paper in the Jan 98 Astronomical Journal, claiming HST FOS imaging of an object 0.5 arcsec (0.6 AU) from Proxima Cen which moved in 105 days. It may be a giant planet or a brown dwarf. This seems to clash with the lack of astrometry movement as seen by the HST FGS.
BD +31 643? 97 Nov 05		Kalas and Jewitt (Nature, 386, 52, 1997) report the detection of a dust disc around BD +31 643. It is strikingly like the Beta Pic disk. They comment that the lifetime of such a disc is much shorter than the age of the star, and that a possible way for it to be replenished is by planets.
Geminga planet? 97 Jun 6		Mattox et al report that Gamma-ray timing indicates a possible planetary companion, but that it might be explained by timing noise. Further observations are needed.
Not planets? 97 Dec 11		More evidence that the planet is real. ``One team, led by Timothy Brown of the High Altitude Observatory in Boulder, Colorado, used the 60-inch telescope at Mount Hopkins in Arizona to obtain high-quality spectra of 51 Pegasi. If the star were pulsating, the shapes of its spectral lines should vary. But they remained constant. The results, which several other teams have confirmed, will appear in Astrophysical Journal Letters.'' New Scientist 97 Dec 11
97 Nov 05		At present the majority view is that the 51 Peg planet is real. Spectroscopic observations of Tau Boo in Jan 97 showed no line shape variations of the size needed to generate the radial velocity changes. Mayor, Queloz, Marcy and Butler have put up a good summary of the `planets are real' case
97 Jun 05		Gray and Hatzes have a paper accepted by Ap.J. analysing the line shape variations of 51 Peg. They say that low order and low degree (l=-m=4) non-radial oscillations explain both the line shape variations and radial velocity changes. They put in a caveat that their data were taken in 1989-1996 and so were not best suited to studying a 4.2 day period.
97 Apr 14		Marcy and Butler have added an item to their planet search Web page concerning the 51 Peg controversy. It discusses the possibility that the system is being seen almost face on, and the companion is an M dwarf. They point out that the weak chromospheric and coronal emission of 51 Peg rule out a stellar companion.
97 Mar 10		David Gray replies to his critics. He states, inter alia, that: a number of models are available to explain the photometric constancy; the McDonald Observatory data only cover a limited phase, and are not inconsistent with variations; the fact that only a few of these solar-type stars show these variations is not strange, as other classes of star, for example Ap stars, show such a pattern. ``The 4th order (and degree), with the motion of one wavelength along the equator corresponding to the 4.23 days, gives a perfect match to the radial velocity data and to the variation in line bisectors. The data for bisector curvature and other parameters, and the modeling, along with further discussion, has been submitted to the Astrophysical Journal.'' ``no legitimate objection against the non-radial-oscillation model for 51 Peg has been put forward that cannot be countered.''
97 Feb 22		An interesting paper by noted stellar spectroscopist David Gray in Nature 97 Feb 27 suggests that the spectral lines in 51 Peg change shape in phase with the 4.2 day period, and that the changes are large enough to produce the observed radial velocity changes, eliminating the need for a planet. There is a discussion - which to my mind seems pretty convincing - of this by Mayor, Queloz, Marcy, and Butler saying that they have doubts about both the data and conclusions. [see also the Geneva paper and the ps version.] The Gray paper itself contains the minimum of information. A preprint by Hatzes, Cochran amd Johns-Krull (in press Ap.J. Feb 97) gives an upper limit to line profile changes below that of Gray. An additional point that occurs to me is that 16 Cyg B, with a period of 829 days, has an eccentricity of 0.57±0.09. Could pulsations mimic such a peculiarly orbit-like radial velocity pattern?
VLBI planets 97 Jan 1		At a number of meetings in the summer of 1996, groups have announced that, using the phase-referencing VLBI technique developed by Jean-Francois Lestrade at the Observatoire de Meudon, radio astrometry has been done with sub milli-arcsecond accuracy on a number (12?) of stars. Astrometric orbits have been shown for two of them. At meetings at the Royal Society and at STScI in October 96, two of the three have been identified as AB Dor and Rositter 137B, with some details given. One report quoted for Rositter 137B suggested a period of 1970 days and an Mj of 15 - but more authoritative reports say it is too early to be certain of this and analysis of additional epochs is needed. We are also told that the rumours floating round about a possible third candidate are premature. The groups are working on their data and acquiring more, but it may be a long time before definitive results can be published. Further information can be read in the Science article (274, 495, 1996) and in the DSN web page.

Stars currently being searched for planets

Observing lists

Master list of the major searches. This is an HTML version of the wonderful list compiled by Astronomy Program and McDonald Observatory. This list does not 96) include the Butler & Marcy Keck list.

Marcy and Butler list of stars the SFSU/Berkeley team are RV searching at Lick. This team has also started (Aug 96) a search using the Keck telescope, with a list of 400 stars.

Alleghany observing list. This is their photographic and MAP astrometry work. Not all of these are being searched for planets.

Individual stars

Proxima Centauri is on the Hatzes, Kuerster, and Cochran high precision (±100 m/s) radial velocity search at ESO. It is also on the program of the HST FGS team.

A preliminary report (Jan 96) of a positive indication from the HST FGS team gave an 0.8Mj at 0.17 AU with an 80 day period. This was followed by a report (Mar 97) of a negative result.

``companion limits below Saturn mass for periods P > 400 days. Detection limits for shorter period companions are higher, approaching one Jupiter mass at P= 40 days.'' Benedict etal 191st AAS [980101]

Barnard's star has in the past had astrometric reports of having a planet companion, but this seems to have gone away. It is on the Marcy RV search list, on the program of the HST FGS team, and on Gatewood's MAP program (Ap&SS, 223, 91, 1995). So far (June 1996) none has reported finding any planet, with limits at about 0.4 Jupiter mass. See the HST FGS report (Mar 97).

``For Barnard's Star we reach a detection limit of about 0.4 Jupiter for P = 400 days, confirming and somewhat extending the limits obtained by Gatewood (1995, A&SS, 223, 91)'' Benedict etal 191st AAS [980101]

CM Dra is an eclipsing binary, so the hope is that any planet will also be in the eclipse plane, and can be detected by photometric transits. These are being looked for by the TEP network and by a team from Villanova University at Mt. Hopkins, who have made a claim to have seen a dip in the flux. This team is also searching for the effect such a planet would have on the binary eclipse timings. The TEP network urge caution in saying this is due to a planet.

Information on the Solar System planets

	Mercury	Venus	Earth	Mars	Jupiter	Saturn	Uranus	Neptune	Pluto
Mass (Earth)	0.055	0.814	1.000	0.108	317.8	95.2	14.5	17.2	0.0025
Mass (Jupiter)	0.000176	0.00256	0.00318	0.329 x10^-3	1.000	0.299	0.0457	0.0549	7.8 x10^-6
Mass (0.001xSun)	0.000168	0.00245	0.00304	0.324 x10^-3	0.955	0.286	0.0436	0.0524	8.2 x10^-9
Orbit (AU)	0.387	0.728	1.000	1.523	5.202	9.540	19.18	30.07	39.44
Orbit (10^6km)	57.91	108.2	149.6	227.9	778.3	1427	2869	4498	5900
Period (days)	87.97	224.7	365.26	686.98	4,332.58	10,759	30,685	60,188	90,700
Radius (km)	2440	6052	6378 - 6356	3394 - 3372	71,492 - 66,854	60,268- 54,364	25,559- 24,973	24,766 - 24,342	1137

The main asteroid belt lies between 2.6 AU and 2.9 AU, and those asteroids have a orbital periods of around 4 to 5 years.

[Radius for the gas giants is for the point where the atmospheric pressure is 1 bar.]

[Mass of Sun = 1.989x10^30 kg     Radius = 695,980 km]

Further information on the planets is available on the NSSDC Planetary Science pages.

Comments

Jean Schneider has a particularly good planet web site at Meudon.

Many of the details of these tables came from information posted by others, including:
Robert Casey (wa2ise@netcom.com);
Jean Schneider (Jean.Schneider@obspm.fr);
John Whatmough (whatmough@mv.mv.com).
For further information on these, look at the various links in the Darwin links page.

Last modified - 1998 January 5th