Author Topic: Astronomy Thread  (Read 100137 times)

Offline Star One

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« Last Edit: 10/01/2018 08:47 PM by Star One »

Offline Star One

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Astronomy Thread
« Reply #561 on: 10/02/2018 08:51 PM »
Black holes ruled out as universe's missing dark matter

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For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe's mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe.

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Based on a statistical analysis of 740 of the brightest supernovas discovered as of 2014, and the fact that none of them appear to be magnified or brightened by hidden black hole "gravitational lenses," the researchers concluded that primordial black holes can make up no more than about 40 percent of the dark matter in the universe. Primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times that of the sun collapsed into objects a hundred kilometers across.

The results suggest that none of the universe's dark matter consists of heavy black holes, or any similar object, including massive compact halo objects, so-called MACHOs.
« Last Edit: 10/02/2018 08:54 PM by Star One »

Offline Star One

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Astronomy Thread
« Reply #562 on: 10/03/2018 07:07 PM »
Couple of new videos from Cool Worlds about their Exomoon candidate.





And here’s an accompanying article on the latest updates.

https://www.centauri-dreams.org/2018/10/03/kepler-1625b-orbited-by-an-exomoon/
« Last Edit: 10/03/2018 07:41 PM by Star One »

Online jebbo

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Re: Astronomy Thread
« Reply #563 on: 10/04/2018 06:46 AM »
Kepler-1625b i is tantalising, but I have to say I'm still somewhat sceptical.

The original exomoon signatures in the Kepler transit data don't look anywhere near as compelling, thanks to better removal of systematics in the latest DR. The TTVs are pretty compelling, and the other new HST stuff is interesting though I don't think it has high significance (I don't really know how to assign a proper significance number to this! For exoplanets it's easy(-ish) ;) ).

The data is consistent with it being an exomoon, but as the article says, eliminating a 2nd planet would be a big step towards proving it.  On the plus side, it transits so all we need to do is get more observations

--- Tony

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Re: Astronomy Thread
« Reply #564 on: 10/04/2018 07:08 AM »
@jebbo: Regarding significance of the HST result, what do you think of the aproach the authors actually take? Their M model seems to be strongly favored over the P (planet only), T (TTVs) and Z (Moon but only TTV aspect) models.
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Offline Star One

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Astronomy Thread
« Reply #565 on: 10/04/2018 08:21 PM »
Kepler-1625b i is tantalising, but I have to say I'm still somewhat sceptical.

The original exomoon signatures in the Kepler transit data don't look anywhere near as compelling, thanks to better removal of systematics in the latest DR. The TTVs are pretty compelling, and the other new HST stuff is interesting though I don't think it has high significance (I don't really know how to assign a proper significance number to this! For exoplanets it's easy(-ish) ).

The data is consistent with it being an exomoon, but as the article says, eliminating a 2nd planet would be a big step towards proving it.  On the plus side, it transits so all we need to do is get more observations

--- Tony

I hope you’re not basing your scepticism on the fact that the HST observations ran out of time and therefore missed the exit point of the moon’s transit.

And yes they are almost stretching Wide Field camera 3 to breaking point with what they were asking it to observe as a general point, but again I am not sure that’s worthy of blanket scepticism.
« Last Edit: 10/04/2018 08:24 PM by Star One »

Offline Star One

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Astronomy Thread
« Reply #566 on: 10/04/2018 08:46 PM »
Cool worlds are doing a Q & A at the moment.



Or NASA finds evidence of exomoon, join NASA scientists on the 5th October at 1pm ET.

« Last Edit: 10/07/2018 11:42 AM by Star One »

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Re: Astronomy Thread
« Reply #567 on: 10/05/2018 07:26 AM »
@jebbo: Regarding significance of the HST result, what do you think of the approach the authors actually take? Their M model seems to be strongly favored over the P (planet only), T (TTVs) and Z (Moon but only TTV aspect) models.

The approach is good ... but the significance of the Kepler moon signatures in the 3 transits has dropped markedly, and the result depends strongly on the one from Hubble (I think this means M will be more favoured just because of the number of free parameters). 

So if all we had was the latest Kepler data, I doubt it would have been flagged as a candidate at all.

On the Hubble moon transit, as noted by Star One, it has no data post egress. Not fatal, but it would have been VERY nice to have data after the candidate transit as this would help enormously with the trend model.

It is still by far the best exomoon candidate we have, and I hope more data confirms it.

--- Tony

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Re: Astronomy Thread
« Reply #568 on: 10/05/2018 11:52 AM »
I think this moon if it exists is more likely a planetary capture as though they state it is allowable for it to have formed with its parent it is on the very upper limits. If it is a planetary capture could the moon have moons in turn?

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Re: Astronomy Thread
« Reply #569 on: 10/05/2018 12:03 PM »
If it is a planetary capture could the moon have moons in turn?

Phil Plait discussed this on Twitter [ tl;dr yes ]

https://twitter.com/BadAstronomer/status/1047564407952293888

--- Tony

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Re: Astronomy Thread
« Reply #570 on: 10/09/2018 08:36 AM »
Further to the "moons of moons" thing, here is a new analysis:

Can Moons Have Moons?
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Each of the giant planets within the Solar System has large moons but none of these moons have their own moons (which we call submoons). By analogy with studies of moons around short-period exoplanets, we investigate the dynamical stability of submoons. We find that 10 km-scale submoons can only survive around large (1000 km-scale) moons on wide-separation orbits. Tidal dissipation destabilizes the orbits of submoons around moons that are small or too close to their host planet; this is the case for most of the Solar System's moons. A handful of known moons are, however, capable of hosting long-lived submoons: Saturn's moons Titan and Iapetus, Jupiter's moon Callisto, and Earth's Moon. Based on its inferred mass and orbital separation, the newly-discovered exomoon candidate Kepler-1625b-I can, in principle, host submoons, although its large orbital inclination may pose a difficulty for dynamical stability. The existence, or lack thereof, of submoons, may yield important constraints on satellite formation and evolution in planetary systems.

Arxiv link

--- Tony

Offline Star One

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Astronomy Thread
« Reply #571 on: 10/09/2018 08:08 PM »
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The
@NASA
 #technosigs18 workshop talks are now up!

(link: https://www.hou.usra.edu/meetings/technosignatures2018/agenda/) hou.usra.edu/meetings/techn…
@jilltarter

https://twitter.com/Astro_Wright/status/1049686230475128832

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Michael New discusses why the workshop was about "technosignatures" and not #SETI at 13:00 ish:
(link: https://www.hou.usra.edu/meetings/technosignatures2018/presentation/new.mp4) hou.usra.edu/meetings/techn…
Somewhat archly admits that the term "SETI" tends to provoke "antibodies" at
@NASA

https://twitter.com/Astro_Wright/status/1049688300066414593

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Also, Martin Still is mistaken in that video about XRP being open to #SETI proposals—as recently as last year such proposals were explicitly out of scope of that program.

https://twitter.com/Astro_Wright/status/1049689753812180993
« Last Edit: 10/09/2018 08:09 PM by Star One »

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Re: Astronomy Thread
« Reply #572 on: 10/10/2018 06:48 PM »

https://www.cta-observatory.org/lst-1_inauguration/


LST(Large-Sized Telescope)-1 for the Cherenkov Telescope Array (CTA) Northern-hemisphere complex in Spain's La Palma island (Canaries) off the coast of Morocco/Western Sahara has been inaugurated today. It was under construction for exactly 3 years. It is the prototype for 8 more LSTs (3 more in Spain and 4 more in Chile). It can reposition to any point in the sky within 20s of the command.


It will be complemented by 40 MSTs and 70 SSTs (Medium- and Small-Sized Telescopes) as well as SCTs (Schwarzschild-Couder Telescopes) to form the CTA Observatory, a collaboration of 31 different countries in two sites: the Canarian one at El Roque de los Muchachos and a Chilean Southern-hemisphere complex in Paranal. In its full configuration (~100 telescopes) it will be 10x more sensitive than current telescopes to the highest-energy photons ever recorded (20-300 GeV).

https://twitter.com/astro_duque/status/1050058265105760257
-DaviD-

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Astronomy Thread
« Reply #573 on: 10/13/2018 09:18 AM »
Dying Star Emits a Whisper

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A Caltech-led team of researchers has observed the peculiar death of a massive star that exploded in a surprisingly faint and rapidly fading supernova. These observations suggest that the star has an unseen companion, gravitationally siphoning away the star's mass to leave behind a stripped star that exploded in a quick supernova. The explosion is believed to have resulted in a dead neutron star orbiting around its dense and compact companion, suggesting that, for the first time, scientists have witnessed the birth of a compact neutron star binary system.

AUSSIE TELESCOPE ALMOST DOUBLES KNOWN NUMBER OF MYSTERIOUS ‘FAST RADIO BURSTS’

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Australian researchers using a CSIRO radio telescope in Western Australia have nearly doubled the known number of ‘fast radio bursts’— powerful flashes of radio waves from deep space.

The team’s discoveries include the closest and brightest fast radio bursts ever detected.
« Last Edit: 10/13/2018 09:51 AM by Star One »

Offline Star One

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Re: Astronomy Thread
« Reply #574 on: 10/16/2018 09:06 PM »
Massive planets spotted near young star leave astronomers scratching their heads

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The star known as Cl Tau lies roughly 500 light years away, which is a stone’s throw in astronomical terms, and scientists now believe it’s being orbited by some truly massive planets. That wouldn’t necessarily be odd, as exoplanets are spotted on a regular basis with modern telescope technology, but what makes this system so unique is that the star itself is only thought to be around two million years old.

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Re: Astronomy Thread
« Reply #575 on: 10/16/2018 10:18 PM »
"spotted" - note that the planets themselves have not been seen (except for the hot jupiter, which is visible in the RV data), only inferred. There have been suggestions that the gaps in these disks might actually represent condensation fronts of different chemical species. Proceed with caution on top of some grains of salt.
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Re: Astronomy Thread
« Reply #577 on: 10/18/2018 06:39 AM »
Largest Galaxy Proto-Supercluster Found

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An international team of astronomers using the VIMOS instrument of ESO’s Very Large Telescope have uncovered a titanic structure in the early Universe. This galaxy proto-supercluster — which they nickname Hyperion — was unveiled by new measurements and a complex examination of archive data. This is the largest and most massive structure yet found at such a remote time and distance — merely 2 billion years after the Big Bang.

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Re: Astronomy Thread
« Reply #578 on: 10/26/2018 05:53 AM »
A first 'snapshot' of the complete spectrum of neutrinos emitted by the sun

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About 99 percent of the Sun's energy emitted as neutrinos is produced through nuclear reaction sequences initiated by proton-proton (pp) fusion in which hydrogen is converted into helium, say scientists including physicist Andrea Pocar at the University of Massachusetts Amherst. Today they report new results from Borexino, one of the most sensitive neutrino detectors on the planet, located deep beneath Italy's Apennine Mountains.

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Re: Astronomy Thread (full solar neutrino spectroscopy)
« Reply #579 on: 10/26/2018 11:06 AM »
A first 'snapshot' of the complete spectrum of neutrinos emitted by the sun

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About 99 percent of the Sun's energy emitted as neutrinos is produced through nuclear reaction sequences initiated by proton-proton (pp) fusion in which hydrogen is converted into helium, say scientists including physicist Andrea Pocar at the University of Massachusetts Amherst. Today they report new results from Borexino, one of the most sensitive neutrino detectors on the planet, located deep beneath Italy's Apennine Mountains.

Thanks for linking this, Borexino is one of the neutrino experiments I work on :) If anyone would like to know more about the physics or the detector technical details, feel free to contact me!
« Last Edit: 10/26/2018 11:14 AM by eeergo »
-DaviD-