Profile cover photo
Profile photo
Robert Minchin
Group Lead for Radio Astronomy at Arecibo Observatory
Group Lead for Radio Astronomy at Arecibo Observatory

Robert's posts

Post has shared content
My draft letter to the NSF. Much less polite than the other one, because they've gone loopy.

Regarding the recent draft Environmental Impact Statement on the future of Arecibo Observatory, while the stated NSF support for the continuing operations at AO is commendable, the details of the DEIS are, to put it mildly, completely mad. The proposed demolition of 26 buildings will not make any financial savings; on the contrary, it would cause irrevocable damage to the Observatory. Removing the buildings necessary for the planetary radar would eliminate the possibility of the Observatory continuing to secure the millions of dollars of NASA funding it currently receives as one of only two facilities in the world capable of Solar System radar studies. Removal of the scientific offices and Visting Scientists Quarters would effectively kill Arecibo as a scientific facility - it will not merely cease to support scientifc staff for their own operations, but fail to provide observing support for external scientists. This is madness. The buildings are not obsolete, they are essential. Consequently any institute wishing to invest in Arecibo would inevitably face the added cost of having to rebuild the lost facilities. This is unnecessary and stupid.

Arecibo is both an iconic, inspirational facility and uniquely scientifically capable. Since starting my PhD 10 years ago, Arecibo data has been integral to my research. I have used data to teach students from high school to graduate level, many of whom have been inspired to pursue careers in science and technology, as well as to produce outreach materials that inform the general public about basic research. No planned or existing facility, including FAST or the SKA, offers Arecibo's unique capabilities, let alone at such a modest level of investment. Furthermore it is by far the most prominent scientific facility in Puerto Rico and local residents are justifiably proud of their historic instrument. For a paltry level of funding it continues to contribute not only to local culture but to global teaching and scientific activities not merely at a world-class level, but with capabilities which are simply impossible at other instruments. There is no prospect of a replacement, let alone superior, instrument in the next few decades, and the current prospect of rendering this magnificent telescope impotent is an absolute absurdity.

Post has shared content
Resharing in the light of the NSF's draft "Environmental Impact Statement", a.k.a., "what shall we do with Arecibo Observatory ?"

+Robert Minchin writes :

Help save Arecibo Observatory!

As you might have heard, Arecibo is currently under threat from the NSF. If you feel that your education has benefited from Arecibo and/or if you feel that you have been inspired by the Observatory (scientifically or culturally), please write to the NSF to let them know, and send a copy to the Advisory Council on Historic Preservation. Letters/emails need to arrive by 12 December 2016.

Addresses are:
Ms. Elizabeth Pentecost
RE: Arecibo Observatory
4201 Wilson Blvd, Ste 1045S
Arlington, VA 22230

Advisory Council:
John Fowler
Executive Director
Advisory Council on Historic Preservation
401 F Street NW, Suite 308
Washington, DC 20001-2637


The NSF's proposal is nothing short of bonkers :
(Full report > 200 pages :

TLDR : They want to keep Arecibo running but with reduced funding from the NSF and more from partner institutions. That's fine, and quite understandable given a funding shortfall. However, for some reason known only to themselves, they also propose demolishing so many buildings that Arecibo would be dealt a very efficient death blow. It would completely stop Arecibo's planetary radar capabilities (Goldstone is the only Solar System radar transmitter in the world) which provides about $5 million of Arecibo's ~$12 million budget. It would demolish the buildings where the permanent scientist's work and the visiting observers are housed, thus killing it completely as a scientific facility. It would, in short, be completely mad, and I for one shall be telling them this using those exact words.

There is no good replacement for Arecibo planned. Not "planned in the near future", but at all. There is nothing remotely comparable to Arecibo - yes, China's FAST is bigger, but its frequency range is much smaller and it won't do planetary radar. It has yet to be demonstrated if it even works at all. Arecibo does unique science, and if we lose it there's little hope we'll ever be able to replace it. We're still making discoveries with Arecibo even in the very nearby Universe for goodness bloody sake; yes, eventually it will become obsolete, but with proper (though modest) investment and development it could remain competitive for decades to come.

Post has attachment
New blog: The American Astronomical Society reaffirms its commitment to discrimination
Today I (along with everyone else feeling threatened by Trump's election) was victim-blamed and gaslighted by the president of the AAS, who also took the opportunity to encourage everyone to tolerate bigots. This is my response.

Post has attachment
New blog post!

Post has shared content
Attack of the Flying Snakes

So here it is, my sixth paper as full author, 27 pages of text, under construction for ~18 months, more than 200 simulations and with movies of all them. Detailed blog posts (it deserves two) will follow shortly, but here's the super-short version for lazy / marginally interested people.

There are some hydrogen clouds in the Virgo cluster without any stars. The nearest galaxies look undisturbed and show no signs of any extended hydrogen streams, and they're pretty far away from the clouds. Yet the most popular explanation is that the clouds are some form of "tidal debris", meaning that they were ripped out of galaxies as they passed close to each other. Generally speaking this is quite a sensible explanation : after all, the gas has got to come from somewhere.

The problem is that thanks to one or two previous simulations - which until now no-one had really bothered to check - this explanation has been used for almost all clouds, regardless of their properties. These particular clouds have high velocity widths, meaning they look like they're rotating. The tidal debris hypothesis is supposed to be able to explain this. Actually, our new set of simulations show that this is due to people over-interpreting the results. Our simulations are consistent with the previous ones, but show unequivocally that clouds with high velocity widths cannot possibly be explained as tidal debris.

We also tested the alternative hypothesis that the clouds could themselves be "dark galaxies" - rotating hydrogen discs embedded in dark matter halos. That scenario turns out to do a far, far better job of explaining the observations, and seems to tie in quite nicely with the newly-discovered "ultra diffuse galaxies" (which are very faint galaxies discovered in the Virgo cluster which do at least have some stars, just not very many).

Why do these stupid poxy gaseous anomalies matter ? Because "dark galaxies" were proposed to explain the missing satellite problem, the observation that there are far fewer small galaxies than predicted by simulations. This has been a major thorn in the side of cosmological models for the last 20 years or so.

Not that we should get carried away. We've shown that tidal debris definitely doesn't work, and dark galaxies do work. But a model which works is not the same as a model which is correct. Other explanations are possible and our simulations (like the previous ones) are missing a lot of important physics. The take-home message of the paper is that if you find a mysterious hydrogen cloud, hand-waving explanations about "tidal debris" are just not good enough.

More research is needed.

Post has shared content

Post has shared content

Post has attachment
New blog post: Rhodes Should Fall 

Post has shared content

Post has shared content
Rejected titles include  "Arecibo Scientists Baffled By Giant Hydrogen Cloud", "Find Out Why Astronomers Can't Explain This Huge Celestial Ring", and "One Young Scientist Went Looking For Galaxies And You Won't Believe What Happened Next"
"Keenan's Ring" is the name we're giving to a giant starless cloud of hydrogen discovered near M33. This is the largest, most massive hydrogen cloud discovered in the region since Wright's Cloud in 1979. In angular size it's about as large as M33 and it's just been sitting there all this time, but it's so faint no-one had noticed it before. Well, not quite, but no-one realised just how large it was or that it was a ring.

We don't have a good explanation for this object. The nearby Wright's Cloud is thought to be part of the much larger Magellanic Stream, but there's no obvious reason why there should be two large clouds at the end but offset at right-angles to the stream. Nor is it obvious why this one should be a ring - there's no particular reason to expect the gas to be missing in the centre of the structure. It's not likely to be a dark galaxy either, because the velocity width is much smaller than would be expected. On the other hand, it does have a small velocity gradient, suggesting that it is a single coherent structure and not a chance alignment of lots of smaller clouds.

The figure shows the 3D data cube obtained with five years of Arecibo observations. The third axis is velocity, not distance (see link for details). Colours are chosen just to highlight different structures : blue for the Milky Way, red for everything else. The data looks noisy at one end but this is just because of how the data was processed. Keenan's Ring can be seen in this noisy red part of the data, but there are better images in the linked post.
Wait while more posts are being loaded