Starship Asterisk*

by **Chris Peterson** » Wed Jan 23, 2013 9:25 pm

MargaritaMc wrote:I do realise that this thread is a little old... But has anyone got more information about this Apod? Robert Nemiroff mentioned it in the Astronomy course on YouTube that I'm working my way through, saying that he was then (2008) unsure about it being a planet. Four or so years on, what is the verdict? And didn't I read not long ago that just recently there has been the first visual image of an extra-solar planet? Or am I very muddled?

By 2010 enough movement had been detected between the two objects to confirm that it's definitely an image of a planet orbiting a star. However, it was not the first such image made- only the first planet observed around a Sun-like star using a ground-based telescope.

by **MargaritaMc** » Wed Jan 23, 2013 8:48 pm

bystander wrote:http://apod.nasa.gov/apod/ap080919.html

Nice catch, Harry! Should be in Discuss an APOD.

I do realise that this thread is a little old... But has anyone got more information about this Apod? Robert Nemiroff mentioned it in the Astronomy course on YouTube that I'm working my way through, saying that he was then (2008) unsure about it being a planet. Four or so years on, what is the verdict? And didn't I read not long ago that just recently there has been the first visual image of an extra-solar planet? Or am I very muddled?

Margarita

by **harry** » Sat Sep 20, 2008 1:14 am

G'day bystander, lucky you were standing by.

by **iamlucky13** » Fri Sep 19, 2008 7:42 pm

bystander wrote:
TimeTravel123456789 wrote:There are definitions of stars that say they are objects with reactions in the core that radiate light. Jupiter, Neptune, Saturn, and even Earth meet that definition.

It is just as likely to end up that the object is a double star. There are cool stars. That near infrared spectra is probably also seen in cool stars. I would bet the same spectra is found in cool stars that are thought of as stars.
I also thought it may be a failed binary, but the planetary mass is too small and too cool to be considered a star or even a brown dwarf by most definitions.

So then presumably its hot primarily due to gravitational collapse?

Time Travel, reactions in the core that radiate energy in the context of a definition of a star generally implies fusion. The earth generates heat from radioactive decay, as well as residual heat from gravitational collapse during its formation.

by **apodman** » Fri Sep 19, 2008 5:50 pm

apodman wrote:Also, they say "Jupiter-sized body" here and "8 Jupiter masses" elsewhere. I can't tell if the size is a mistake or if they really mean it's 8 times as dense as Jupiter.

http://en.wikipedia.org/wiki/Brown_dwar ... ss_planets

A remarkable property of brown dwarfs is that they are all roughly the same radius, more or less the radius of Jupiter. At the high end of their mass range (60-90 Jupiter masses), the volume of a brown dwarf is governed primarily by electron degeneracy pressure[2], as it is in white dwarfs; at the low end of the range (1-10 Jupiter masses), their volume is governed primarily by Coulomb pressure, as it is in planets. The net result is that the radii of brown dwarfs vary by only 10-15% over the range of possible masses. This can make distinguishing them from planets difficult.

by **bystander** » Fri Sep 19, 2008 4:25 pm

TimeTravel123456789 wrote:There are definitions of stars that say they are objects with reactions in the core that radiate light. Jupiter, Neptune, Saturn, and even Earth meet that definition.

It is just as likely to end up that the object is a double star. There are cool stars. That near infrared spectra is probably also seen in cool stars. I would bet the same spectra is found in cool stars that are thought of as stars.

I also thought it may be a failed binary, but the planetary mass is too small and too cool to be considered a star or even a brown dwarf by most definitions.

by **TimeTravel123456789** » Fri Sep 19, 2008 3:44 pm

There are definitions of stars that say they are objects with reactions in the core that radiate light. Jupiter, Neptune, Saturn, and even Earth meet that definition.

It is just as likely to end up that the object is a double star. There are cool stars. That near infrared spectra is probably also seen in cool stars. I would bet the same spectra is found in cool stars that are thought of as stars.

by **bystander** » Fri Sep 19, 2008 3:28 pm

apodman wrote:How long does a new planet this size stay this hot?

If there are new star systems nearby and a planet this size stays this hot for a long time, the odds that this is a capture go up.

If there are not new star systems nearby and a planet this size stays this hot for a short time, the odds that this is a capture go down.

Of course we need real numbers instead of "nearby" and "short/long time", but that looks like more research and calculation than I want to bite off right now.

I concur. If there are no new star systems nearby, planetary capture becomes a very remote possibility. Free-floating planets are not likely to be this hot, even if from a nearby nebula.

I do expect we'll find that the orbit is highly eccentric, but that will take some time to resolve.

http://www.astronomy.com/asy/default.aspx?c=a&id=7387

The near-infrared images and spectra of the suspected planetary object indicate that it is too cool to be a star or even a more massive brown dwarf, and that it is young. Taken together, such findings confirm that it is a very young, very low-mass object at roughly the same distance from Earth as the star.

Even though the likelihood of a chance alignment between such an object and a similarly young star is rather small, it will take up to 2 years to verify that the star and its likely planet are moving through space together. "Of course, it would be premature to say that the object is definitely orbiting this star, but the evidence is extremely compelling. This will be a very intensely studied object for the next few years!

by **apodman** » Fri Sep 19, 2008 2:59 pm

bystander wrote:Planetary capture may be a possibility, if there are other stars or dark nebula in the general area.

How long does a new planet this size stay this hot?

If there are new star systems nearby and a planet this size stays this hot for a long time, the odds that this is a capture go up.

If there are not new star systems nearby and a planet this size stays this hot for a short time, the odds that this is a capture go down.

Of course we need real numbers instead of "nearby" and "short/long time", but that looks like more research and calculation than I want to bite off right now.

http://www.astronomy.com/asy/default.aspx?c=a&id=7387

The Jupiter-sized body has an estimated temperature of about 1800 Kelvin (about 1500° C), much hotter than Jupiter, which has a temperature of about 160 Kelvin (-110° C).

When I was young I was taught that Jupiter is so "hot" and massive that it barely missed being a star. So if this thing is 8x the mass of Jupiter and half as hot as the sun, it must have come really close to stardom. (Are you kidding? 1500° C is really hot! Bring your Teflon rocket-ship.)

"Hot" Jupiter, on the other hand, is as cold as Earth's South Pole in winter. Hot compared to Absolute Zero, but a little chilly for my bones.

Also, they say "Jupiter-sized body" here and "8 Jupiter masses" elsewhere. I can't tell if the size is a mistake or if they really mean it's 8 times as dense as Jupiter. Some increased density might make sense with the increased temperature (my thermodynamics knowledge is too faded to use), but 8-to-1 seems like a lot.

by **bystander** » Fri Sep 19, 2008 2:55 pm

harry wrote:Gemini North telescope captures first picture of likely planet

http://www.astronomy.com/asy/default.aspx?c=a&id=7387

Gemini North telescope captures first picture of likely planet
Astronomers have unveiled what is likely the first picture of a planet around a normal star similar to the Sun.
Provided by Gemini Observatory, Hilo, Hawaii
September 15, 2008

by **bystander** » Fri Sep 19, 2008 2:47 pm

Newtonian Physics says that all orbits are elliptical. Some are more eccentric than others. Sedna, a dwarf planet candidate, has a highly eccentric orbit, ranging from 76 to 976 AU. However, a planet this large and massive that far from its parent star is quite unusual. I expect the orbit is very eccentric, and may grow less so as the system matures. Keep in mind this is a very young star and planetary system. Planetary capture may be a possibility, if there are other stars or dark nebula in the general area.

by **JohnD** » Fri Sep 19, 2008 2:27 pm

Quote from abstract of paper announcing this (sse APOD):
"its existence at such a large separation would pose a serious challenge to theories of star and planet formation. "

Capture?
Chaotic inner system, throwing it into an elliptical orbit?

John

by **apodman** » Fri Sep 19, 2008 2:13 pm

http://apod.nasa.gov/apod/ap080919.html

The likely young planet is 330 AU from its star.

Distances for comparison:

1 AU - Sol to Earth
30 AU - Sol to Neptune
330 AU - Young star to likely young planet
63000 AU - Sol to alpha Centauri

The likely new planet's distance to its star is more than 1/200 of the distance from Sol to the nearest star. You can even draw this to scale and see it, unlike many other astronomical proportions.

What does Sol look like from 330 AU? Well, it's about 30 arc minutes at 1 AU, so it would be less than 0.1 arc minute at 330 AU. Venus at its closest approach to Earth transects about 1 arc minute. The resolution of the naked human eye is about 1 arc minute. So from 330 AU Sol looks like a point of light. You would need a small amount of magnification to resolve a disk.

by **bystander** » Fri Sep 19, 2008 12:35 pm

http://apod.nasa.gov/apod/ap080919.html

Nice catch, Harry! Should be in Discuss an APOD.

by **harry** » Fri Sep 19, 2008 8:41 am

Young Star With Hot Planet, Gemini N gets pic (19Sep08)

G'day from the land of ozzzzzz

Gemini North telescope captures first picture of likely planet

http://www.astronomy.com/asy/default.aspx?c=a&id=7387

Starship Asterisk*

APOD: Companion of a Young, Sun-like Star (2008 Sep 19)

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Young Star With Hot Planet - APOD 2008 September 19

APOD: Companion of a Young, Sun-like Star (2008 Sep 19)