If the distance were wrong, that would indicate the size is wrong too. Indeed, Joyce says, the ambiguity surrounding traditional parallax measurements is likely to remain in the near-future. Nevertheless, Harper urges caution with the new results. All the assumptions and uncertainties known and unknown can add up. But it is an interesting result. If the result pans out, it has some implications: A smaller Betelgeuse is likely at a slightly earlier stage of its lifetime, putting off any potential supernova.
There is an important point missing here. Radii for Betelgeuse is actually variable, something like a jellyfish swimming in the sea.
Hence, Dolan, et al. ApJ, , 7 radii being solar radii. The cause of the brightness changes is as a consequence of energy production in the core, assumed to fluctuate output because the nuclear fuel is running out, technically causing differences in opacity.
These are s-called pressure modes or p-modes as mentioned in their paper , that they assume is day period. As the star ages, the pulsation cycles change into non-linear pulsations. Alternatively, the brightness changes could be due to slow rotation of the star, where the star 'surface' is more bloated or uneven in different places that show differences in temperature. This is clearly seen on the IR images. Again it points towards the star is not exactly spherical.
Log in to Reply. We adopt this as the best means to deduce a radius to compare with stellar models. Radii for Betelgeuse may also be diffuse. A ball of gas has no definite edge. The Sun's size is generally given as the diameter of its photo-sphere, as light-emission ceases somewhat abruptly, below some threshold density.
Nicely put. What you refer to is limb darkening, whose degree is quantifiable. Figures quoted take that into account. If this is based on an agreed definition, at least we can compare results. Pardon my naivete but I do have a doubt. Is a time period of 10 million years adequate for planets to form or semi form AND get ripped apart?
Also, the mass has to be large enough for the debris to obscure the parent star's radiation by such a substantial quantity as to be measurable a few hundred light years away? Keeping in mind that a behemoth the parent star is forming just a few blocks away and is gobbling up matter at an alarming rate, the wannabe planet may not have much chance in its endeavour!
I could be totally wrong though. Very interesting report. I checked some figures using my MS Excel astronomy spreadsheet I developed. Using a distance of pc and angular size 42 mas, the diameter of Betelgeuse is This report shows how difficult it can be to determine an accurate distance to the star and an accurate stellar diameter. Excellent article Monica. On the subject of the recent dimming one interesting speculation might be that dust from an orbiting, vaporized Betelgeusian planet, maybe at 9 to 12 AU, produced the light reduction.
It could be that the planet remains are in a very eccentric orbit and the recent event was a return to closest approach apsis peribetelgeuse?
If so, it may have been some time, depending on the orbital eccentricity, since any previous dimming event. Or, alternatively, the vaporized planet's remains could presently be at a significantly greater distance, having been pushed back by the radiation pressure since the time of vaporization and subsequent dust formation. Hence in a much longer but less eccentric orbit. However this is all rather speculative without any historical light dimming event observational backup.
I am wondering if only one observation was made at the VLT December ? A few further observations may have shown a drifting of the obscuring cloud across the face of the star.
At 9 to 12 AU, such planets couldn't survive inside a star. Tidal forces would disintegrate them and the stars atmospheric resistance viscosity would quickly strip it apart. A little snack for Betelgeuse. By area, Betelgeuse is 9. Compared to red giants, planets are just pipsqueaks.
Sorry, but my hypothesis is that the remnants of a vaporized planet, not a standard planet produced the dimming dust. The mass of Betelegeuse or sun can be placed at a point at the star's center as per Newton.
So Betelgeuse is, despite its mass, not a tidally disruptive object, in this picture. Of course, the tidal force on a vaporized planet would be very large, even at 10AU so it would be disrupted.
There is no evidence for this. If anything, such an event would likely make the star become slightly brighter not dimmer. Apparently Gaia should be able to measure the parallax for Betelgeuse using a 'special mode'. I am not sure if the special observations and analysis required has restarted or not. GAIA will not improve the problem of radius nor distance, as the parallax of c. And the other one, it seems, shows just how healthy our old Aunt Betelgeuse is.
Pulsations like those observed in Betelgeuse are typically the result of pressure waves coursing through the burning innards of a star. Our own Sun has waves rippling throughout its body, which tells a lot about its makeup deep inside. Using information collected with the space-based Solar Mass Ejection Imager prior to Betelgeuse's recent drop in luminosity, the research team developed models of the star's activity to come up with a better sense of just how close to retirement it really was.
The results also allowed the researchers to deduce the giant's radius, shaving a third off its previous girth. Based on this new figure, Betelgeuse can't be more than light years away, either.
Look, we're all a little disappointed. It's been four centuries since a supernova has been observable to the naked eye, and we feel we're owed a decent star funeral.
Now that we know Betelgeuse is even closer to us than we thought, it's sure to be one heck of a display when it does eventually collapse.
If you're at all concerned about the new seating arrangements, at light years we still won't be close enough to feel the heat of its radiation either. For whatever passes for a scientist in , CE, these front row seats will certainly be an opportunity. And this is our closest candidate.
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