London - Astronomers have discovered the first known planet to survive its "red-giant" phase, a period when an aging star expands and engulfs bodies orbiting it.

The discovery of the gas-giant planet three times the size of Jupiter offers a look at the future of our own solar system and what will happen to the Earth when the sun grows old and collapses.

Scientists found the planet some 4,500 light-years from Earth. It once orbited its star at the same distance as the Earth is now from the sun -- about eight light-minutes -- but then drifted away.

The team found this planet by chance while studying its parent star V 391 Pegasi.

During its time as a middle-aged star, V 391 Pegasi had a mass similar to the sun before it expanded its radius by more than 100 times when it entered its red-giant phase -- something the sun is expected to do in 5 billion years.

The planet stayed intact because the parent star lost mass, reducing its gravitational pull just enough to let the planet drift away a bit.

When the Sun -- which scientists think is 30 percent bigger than when it came into being -- exhausts all its hydrogen and swells up during its red-giant phase, the Earth will also likely avoid complete destruction for the same reason.
go

yes, the planet could drift away but the temperature would be too high and the water would evaporate, atmosphere gone and etc. the planet would not be suitable for life.

I used to think Earth might drift, but it also might cross orbits and interact with the large outer planets. Interestingly, I have read that the earth might well dive into the sun.

If those icy moons of the gas giants have any potential for prebiotic activity, they will certainly have their "day in the Sun", a few billion years from now.

There are several recent discoveries about late stage or post main sequence stars, especially white dwarfs and binaries, that are really interesting- like dusty disks around WDs.

Thank you for the article, "owlscrying", and commentary from Lightyagami.

This article is worth another post. Here is the abstract from Nature-

After the initial discoveries fifteen years ago, over 200 extrasolar planets have now been detected. Most of them orbit main-sequence stars similar to our Sun, although a few planets orbiting red giant stars have been recently found.When the hydrogen in their cores runs out, main-sequence stars undergo an expansion into red-giant stars. This expansion can modify the orbits of planets and can easily reach and engulf the inner planets. The same will happen to the planets of our Solar System in about five billion years and the fate of the Earth is matter of debate.

Here we report the discovery of a planetary-mass body (Msini = 3.2MJupiter) orbiting the star V 391 Pegasi at a distance of about 1.7 astronomical units (au), with a period of 3.2 years. This star is on the extreme horizontal branch of the Hertzsprung–Russell diagram, burning helium in its core and pulsating. The maximum radius of the red-giant precursor of V 391 Pegasi may have reached 0.7 au, while the orbital distance of the planet during the stellar main-sequence phase is estimated to be about 1 au. This detection of a planet orbiting a post-red-giant star demonstrates that planets with orbital distances of less than 2 au can survive the red-giant expansion of their parent stars.


Here are two sites for information on these stars-

Hot subdwarf stars - Horizontal Branch stars

and

Simon Jeffery at Armagh Observatory


(Wiki)

The planet is named V 391 Peg b, because it is a hot B-type subdwarf. Located on the extreme horizontal branch of the Hertzsprung–Russell diagram, "burning helium in its core and pulsating on the extreme", the star's history may be traced out on the H-R diagram. Provided there are no encounters with other stars, etc.

(Wiki)




Hertzsprung-Russell diagram 22,000 stars are plotted from the Hipparcos catalog and 1000 from the Gliese catalog of nearby stars. An examination of the diagram shows that stars tend to fall only into certain regions on the diagram. The most predominant is the diagonal, going from the upper-left (hot and bright) to the
lower-right (cooler and less bright), called the main sequence.

There are several forms of the Hertzsprung-Russell diagram, and the nomenclature is not very well defined. The original diagram displayed the spectral type of stars on the horizontal axis and the absolute magnitude on the vertical axis. The first quantity (i.e. spectral type) is difficult to determine unambiguously and is therefore often replaced by the colour index of the stars. This type of diagram is called a Hertzsprung-Russell diagram, or colour-magnitude diagram, and it is often used by observers. However, colour-magnitude diagram is also used in some cases to describe a plot with the vertical axis depicting the apparent, rather than the absolute, magnitude.

Another form of the diagram plots the effective temperature of the star on one axis and the luminosity of the star on the other. This is what theoreticians calculate using computer models that describe the evolution of stars. This type of diagram should probably be called temperature-luminosity diagram, but this term is hardly ever used, the term Hertzsprung-Russell diagram being preferred instead. Despite some confusion regarding the nomenclature, astrophysicists make a strict distinction between these types of diagrams.

The reason for this distinction is that the exact transformation from one to the other is not trivial, and depends on the stellar-atmosphere model being used and its parameters (like composition and pressure, apart from temperature and luminosity). Also, one needs to know the distance to the observed objects and the interstellar. Empirical transformation between various colour indices and effective temperature are available in literature.

(Wiki)

Wow, Earth MAY survive the red giant. All life may have well been wiped out by then on Earth anyway due to human stupidity. Very interesting, I will look that up as well to see some other sites. Thanks Owlscrying.

Astronomers have spotted a planet that has survived the massive ballooning of its parent star, providing the first optimistic evidence for the long-term survival of Earth.

The discovery, detailed in the Sept. 13 issue of the journal Nature, could motivate other scientists to look for similar red giant survivors. That in turn could eventually lead to an answer to one of astronomers' favorite questions: Will Earth survive the sun's swelling when it goes through its own red giant phase in a few billion years?

"The fact that we have found this planet proves that a planet with a small orbital distance can survive" a star's red giant phase, said study team member Roberto Silvotti of the National Institute of Astrophysics in Naples, Italy.

http://www.livescience.com/space/scienceas...ant_planet.html

Roj47, as there has already been postings on this story in the Exoplanets thread (starting with this post) in the Space News forum plus a thread in the Space and Astronomy section I am going to merge threads.

From a point of view of keeping the threads in a logical order it is easier to merge this thread with the one in the Space and Astronomy forum, so that is what I will do.

Explain me how life on Earth could survive to the sun explosion if life depends of it to live?
And even we can survive we will disappear because the high temperatures that we will have.

Firstly, not one single post in this thread contains a claim that life will survive, only that the Earth might, so who exactly are you asking to explain this?

Secondly which "explosion" are you talking about? The sun is far to small to undergo a supernova explosion. This thread is about planets surviving the red giant phase of existence. Towards the end of the life of a Sun like star it will have exhausted all the helium in it's core. Nuclear fusion ceases and gravity begins to cause the star to contract. This in turn causes the temperatures and pressures at the core of the star to rise. When the temperature rises sufficiently a new phase of nuclear fusion starts, this time helium is the fuel. The internal pressure caused by this new phase of fuel burning causes the star to swell to far beyond it's original size, this is a red giant.

It is this process I have described above that the Earth may survive, not an explosion.

If earth might survive to a Red Giant I dont see wheres the big thing if all life will disappear in a way or other.

I was refering the expand of the sun as a "explosion", as I saw in documentaries the Sun before collapses it will expand "eating" the closers planets,expand and fade.

It is a matter of knowledge and understanding. This research has expanded the wealth of human knowledge. If it is of no interest to you fair enough, but I find it strange that people take the time and effort to make post about something they think is no "no big thing".


So when you said "explosion" you didn't actually mean that? As you are Portuguese I expect I misunderstood you as a result of the language difference (your English is much better than my Portuguese by the way).

Is no big thing -- each opinion counts for the subject,so if the topic is interesting for me,I gave my opinion about the conclusion.

I said "explosion" in a literally way.