The First Exoplanet

[George]

HD 114762b is listed as the first exoplanet. It was discovered in 1989 but was determined to be a brown dwarf. A paper in 1995 suggested it might be a low mass M-class star companion, rather than the original idea that it might be a brown dwarf.

When did this exoplanet become a planet? Why is it not considered the first planet discovered?

[I could not find this discussion in BAUT.]

[StupendousMan]

HD 114762b is listed as the first exoplanet. It was discovered in 1989 but was determined to be a brown dwarf. A paper in 1995 suggested it might be a low mass M-class star companion, rather than the original idea that it might be a brown dwarf.

When did this exoplanet become a planet? Why is it not considered the first planet discovered?

[I could not find this discussion in BAUT.]

I suggest you ask the keeper of the Extrasolar Planets Encyclopedia website. After all, it is his list that you are using as a source.

[George]

Good point.

It appears the verdict is still out on this one as this object is at the borderline of exoplanet and brown dwarf.

It is estimated to have a mass of 10.06 to 11.98 M_J. If the minimum mass of a brown dwarf is indeed 13 M_J, then there is no reason, I guess, not to consider it an exoplanet. This is probably their logic for listing it as an exoplanet.

Assuming this as their reasoning, would they not be justified?

[Kullat Nunu]

It was originally thought (and is still suspected) to be a brown dwarf. 51 Pegasi b was far more convincing candidate.

BTW, HD 114762 b was not the first pre-51 Peg candidate. Some stars like Gamma Cephei (Errai) and Pollux were suspected having planets (in 1989 and 1993, respectively), but both cases were deemed not to be convincing enough (in fact, the original discoverers of Gamma Cephei b retracted their discovery claim after they thought it was spurious).

And, of course we all know that 51 Pegasi b was not the first confirmed extrasolar planet. That honor belongs to the pulsar planets PSR 1257+12 B and C, both only a few Earth masses. The third planet (A) remains the least massive known extrasolar planet with a mass less than that of the Moon. It was found in 1994. The only other known pulsar planet, PSR B1620-26C, was also found before 51 Pegasi, in 1994. So no new pulsar planets in 13 years despite the fact they're very easy to find which means they must be very rare.

[George]

If HD114762 is verified to have a mass withing the range stated in the OP paper, will it qualify as a planet, and would it be the first?

Is the minimal mass for a brown dwarf 13.65 Jupiters?

[TheOncomingStorm]

Is the minimal mass for a brown dwarf 13.65 Jupiters?

The limit I think is 13 Jupiter masses.

[TheOncomingStorm]

oh george if you are interested here is a good book to find.
http://www.amazon.com/Looking-Earths...e=UTF8&s=books

[Eckelston]

Good point.

It appears the verdict is still out on this one as this object is at the borderline of exoplanet and brown dwarf.

It is estimated to have a mass of 10.06 to 11.98 M_J. If the minimum mass of a brown dwarf is indeed 13 M_J, then there is no reason, I guess, not to consider it an exoplanet. This is probably their logic for listing it as an exoplanet.

Assuming this as their reasoning, would they not be justified?

Unless it's a transiting planet the quoted mass is the real mass times sine i, where i is the inclination of the orbit as seen from the earth, so it would be quite likely to be more massive than 13 Jupiters.

[George]

The limit I think is 13 Jupiter masses.

Yes, I suppose so. I thought I heard Pamela Gay say 13.65 in a recent Astronomy Cast podcast, but it was faint; she may have said "13 is fine" and I misheard it.

Unless it's a transiting planet the quoted mass is the real mass times sine i, where i is the inclination of the orbit as seen from the earth, so it would be quite likely to be more massive than 13 Jupiters.

This seems to be the case. Here are some papers referenced from the Exoplanet site"

"This leads to the suggestion that the companion is probably a brown dwarf, and may even be a giant planet. However, because the inclination of the orbit to the line of sight is unknown, the mass of the companion may be considerably larger than this lower limit."
David Latham, et al, 1989.


"The result show that the companion is not a planet, but instead is a brown dwarf or a low mass star in a system viewed nearly pole-on."
William Cochran, 1991.


"Although the formal uncertainties in this process preclude an accurate estimate of the companion's inclination, the results suggest that the inclination is low, possibly low enough to force the companion's mass above the limit for hydrogen fusion. It is thus possible the companion may be nothing more exotic than a low-mass M star, as opposed to a brown dwarf."
Alan Hale, 1995

There seems to be no justification for listing it as a planet, supporting Stupendous Man's question.

[Added: I wonder if somehow it got accidentally carried over from the < 18 Jupiter mass objects from the Geneva Observatory? Just speculating wildly, admittedly.]

[mfumbesi]

So no new pulsar planets in 13 years despite the fact they're very easy to find which means they must be very rare.

For a moment there I thought you wrote So no new planets in 13 years .
I giggled a bit and I was ready to tear at you, until I read your post again.