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posted by chromas on Friday July 24 2020, @02:14PM   Printer-friendly
from the brown-giants dept.

Science Magazine:

Astronomers know of thousands of planets around other stars, yet only a handful have been imaged directly. The existence of the rest is inferred by how they affect their stars.

Now the world's largest optical telescope has directly spied a new planetary system—the first time more than one planet has been imaged around a star like our Sun. Astronomers used the European Southern Observatory's Very Large Telescope (VLT) to observe the Sun-like star TYC 8998-760-1, 300 light-years from Earth. Using the VLT's Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument, which is equipped with an optical mask called a coronagraph to block out a star's light, they were able to see two planets orbiting it [pictured here], as reported today in The Astrophysical Journal Letters. Some light from the star can be seen in the image above (center left) as well as the two giant planets (right) and a scattering of background stars.

The star system is very young at 17 million years old.

Also at AstronomyNow.

Journal Reference:
Alexander J. Bohn, Matthew A. Kenworthy, Christian Ginski, et al. Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1 - IOPscience, The Astrophysical Journal Letters (DOI: https://iopscience.iop.org/article/10.3847/2041-8213/aba27e)


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  • (Score: 2) by bzipitidoo on Friday July 24 2020, @03:42PM (2 children)

    by bzipitidoo (4388) on Friday July 24 2020, @03:42PM (#1025813) Journal

    I was wondering if at 300 light years distance, the telescope would see only pinpoints, but it seems it's able to make out discs.

    Just going from basic geometry, to double the diameter of a planet takes 8 times the mass. That's not accounting for the greater pressure all that mass would create. Can only guess about the temperature and how much thermal expansion as a consequence. These 2 exoplanets are much further away from their host star, with the outer one being very roughly as far as the hypothetical Planet 9 is from our sun, so should be a bit cooler for that reason. But they're so big that they will retain much more heat from formation, and they are very young. All in all, I guess the diameters to be roughly twice that of Jupiter.

    Very impressive. The dream of sending probes a la the Voyagers but ramped up to handle interstellar travel, I suppose is going to stay a dream for a while yet. And that's not least because home based optics can be pushed a lot further. What kind of resolution can we ultimately expect to obtain from something like a Very Large Array of telescopes in solar orbit perhaps at a distance between Jupiter and Saturn, for a little more resolution, less interference from the inner solar system, like so that the observatories can easily avoid looking through the asteroid belt? Would want some in polar orbit about the sun, of course. Or would it be more convenient to have such an array in solar orbit between Earth and Mars, to cut down on the communication delays, though that does reduce the resolution?

    Even if we could send probes to the nearest stars, by greatly increasing the velocity we are able to impart to them so that they can travel at 0.1c, their reach is still extremely limited. That may do to probe Alpha Centauri. Just a little further, such as distances of a mere 100 ly, an Alpha Centauri class probe probably won't cut it. 1000 years of travel time just to reach the destination is an awful, awful long time an energy source and devices have to last. On a galactic scale, 100 ly is real small. So, yeah, it'll have to be telescopes.

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  • (Score: 2) by HiThere on Friday July 24 2020, @08:09PM

    by HiThere (866) Subscriber Badge on Friday July 24 2020, @08:09PM (#1025910) Journal

    Well, the Fenachrone were reported to use space based telescopes with a five mile diameter, and see any planet in the galaxy. This was fiction, and is clearly wrong if only because of dust clouds, but...

    Optical interferometry is now a real thing. With a bit of improvement you could use pulsars to synchronize the timing. Put a large telescope (for quantity of light collected) at opposite poles of Neptune's orbit. That would give you a bit of parallax. Ideally you'd want one more equally far from the sun, but above or below the plane of the ecliptic. You could probably make a 3-D movie of anything facing you, though there'd be a lot of post-processing needed.

    So. How much can we see without leaving the home system...well, quite a lot, actually, if we really put our effort behind it. The images within the galaxy would probably be limited by quantity of light collected rather than the ability to focus closely. Five mile telescopes kept accurate to 1/4 wavelength are really beyond the state of the art once you get much shorter than radio wave lengths. You'd need excruciatingly good temperature control on that mirror AT ALL TIMES. But with good enough interferometry you could combine several smaller telescopes to achieve the same light collecting power. More telescopes, though, over a larger distance, makes focus trickier.

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  • (Score: 0) by Anonymous Coward on Friday July 24 2020, @09:15PM

    by Anonymous Coward on Friday July 24 2020, @09:15PM (#1025952)

    Gas planets don't normally get much bigger than Jupiter. Additional mass mostly increases the density, not the volume. A 40 Jupiter mass brown dwarf might be 10% larger in radius than Jupiter. The biggest factor in the size of a gas giant is its temperature. These planets are probably a little warmer than Jupiter because they are so young, but not by the thousands of degrees that can make a "hot Jupiter" get all puffy.