Seeing a Black Hole

Almost exactly one year ago, the Event Horizon Telescope project released the first image of a black hole, thereby making headlines all over the world, including at Ratburger. The director of the project, Sheperd Doeleman, gave the public lecture at the virtual April meeting of the American Physical Society earlier today. Most of the talks at the meeting require registration but this link should be accessible to unregistered viewers. If that doesn’t work, the talk was also posted on Facebook (FB account is not required). The public lecture is designed to be accessible to non-specialists. I thought he did a decent job.

EHT image of the black hole in M87 (Wikipedia)

M87 is an elliptical galaxy in the Virgo constellation. It’s about 53 million light years from Earth. That’s some social distancing!

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Look, up in the sky! Moon Occults Mars, 2020-02-18

Occultation of Mars by the Moon, 2003-07-17.
Original photo © 2003 Andrew Chaikin.

On the morning of February 18th, 2020, observers in most of North America will be able to see the waning crescent Moon pass in front of (occult) the planet Mars.  The photo at the right, taken by Andrew Chaikin during the 2003 lunar occultation of Mars, is more dramatic than this event will appear through a telescope.  In the 2003 occultation, Mars was just 0.48 astronomical units (AU) from the Earth, while this time Mars will be at distance of 1.81 AU, 3.8 times farther away and correspondingly smaller and dimmer.  Still, Mars will shine at magnitude 1.2, one of the brightest “stars” in the sky, and its reddish hue will stand out against the colourless Moon.

Lunar occultation of Mars, 2020-02-18This map shows the visibility of the occultation.  The occultation will be visible in the area delimited by the cyan shape at the top and the multicoloured curve at the bottom.  The event will thus be visible in most of North America (except for Alaska and the far north of Canada), Central America, and the Caribbean.  In the area of the loop at the top left, covering part of the American northwest and western Canada, the Moon will rise with the occultation already in progress, but observers will be able to see Mars emerge from behind the Moon’s dark limb at its conclusion.... [Read More]

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Sic Transit Glorious Monday

Transit of Mercury weather, 2019-11-11Today, Monday, November 11th, 2019, is the long-awaited transit of the planet Mercury across the disc of the Sun, the last such event before November 2032.  Now, before the transit of Venus in June 2004, I vowed that if I got good weather for that spectacle I wouldn’t complain about the weather ever again.  The weather, and the transit, were glorious, so I’m not complaining.  But I can grumble, can’t I?  Here is the weather looking out my window.  This was taken around an hour ago, and since then the ground fog has only gotten thicker.

So, it’s off to the Webcasts.  The NASA Solar Dynamics Observatory (SDO) is watching the transit from space, where the event starts about half an hour before it becomes visible from Earth.  Their Web site was down, presumably crushed by the dozens of people hoping to see the transit there, but it has recently come up and is showing Mercury crossing the inner solar corona (which is only visible from space), approaching the solar disc.... [Read More]

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Reminder: Transit of Mercury, November 11, 2019

Transit of Mercury, 2003-05-07Next Monday, November 11th, you can watch Mercury, the innermost planet, cross the disc of the Sun.  This was the subject of Saturday Night Science for September 2019, and that article gives complete details of the event, a global map of visibility (the transit is visible, in whole or in part, from almost all of North and South America, Africa, and Europe), and recommendations for visual observation and photography of the transit.

You’ll need optical assistance (binoculars, a modest telescope, or a telephoto camera lens) equipped with a safe, full-aperture solar filter, in order to see the tiny disc of Mercury (just ten arc-seconds) crossing the Sun.  If you’re interested in observing and haven’t yet secured and checked out the required gear, now’s the time to opt for overnight shipping—there’s just a few days left.... [Read More]

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Another Interstellar Visitor?

C/2019 Q4 Borisov, candidate interstellar cometOn August 30th, 2019, Gennady Borisov, an optician and astronomer at the Crimean Astrophysical Observatory, using equipment he built himself, discovered a dim (18th magnitude) object moving with respect to the distant stars.  Further observations indicated it was cometary in appearance, with a coma around its brightest spot and apparent short tail.  Orbital computations from the limited number of observations indicate that it was discovered at a distance of around 3 astronomical units (AU) (the mean radius of the Earth’s orbit) from the Sun, inbound toward a perihelion on December 10th near 2 AU.

As with ’Oumuamua (1I/2017 U1) in 2017, attempts to fit a typical elliptical or parabolic orbit to the observations failed, and the best fit was found to be a hyperbolic orbit with an eccentricity in excess of 3.  Such an object is not gravitationally bound to the solar system and must be of interstellar origin; after rounding the Sun, it will depart into interstellar space never to be seen again.  This is only the second such object to be observed.  From observations so far (and with less than two weeks of data, these figures will be revised as further observations are made), its inbound velocity to the solar system before it began to be accelerated by the Sun’s gravity was around 30 km/sec, which rules out a hyperbolic orbit due to interactions with solar system objects, as such perturbations cannot create a velocity greater than 3 km/sec.  Here is the Minor Planet Center Circular, MPEC 2019-R106, announcing the discovery, its apparent interstellar nature, and preliminary orbital elements based on the news that’s come to Harvard.... [Read More]

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Saturday Night Science: Transit of Mercury, November 11, 2019

Transit of Mercury, 2003-05-07On November 11th, 2019, between 12:35 and 18:04 universal time (UTC), Mercury, the innermost planet, will pass in front of the Sun as seen from Earth: an astronomical spectacle called a “planetary transit”.  Planetary transits visible from Earth are relatively rare events: only the inner planets Mercury and Venus can ever pass between the Sun and Earth, and they are only seen to cross its disc when the plane of the planet’s orbit intersects the plane of the Earth’s orbit (the ecliptic) close to the time when the planet is at inferior conjunction with the Sun.  On most inferior conjunctions, the orbital planes do not align (or, in other words, are not close to a node crossing) and the planet “misses” the Sun, passing above or below it as seen from Earth.

Mercury’s orbit crosses the ecliptic around May 8 and November 11 at the present epoch, and so transits always occur within a few days of those dates.  The most recent transit of Mercury was on May 9th, 2016 (when, despite being clouded out for most of the event, I managed to briefly observe and photograph it through thin clouds), and the next transit will not occur until November 13th, 2032, so if you miss this one, you’ll have a thirteen year wait until the next opportunity.... [Read More]

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Total Solar Eclipse: 2019-07-02

Total solar eclipseA total solar eclipse will take place today, 2019-07-02.  Totality will be visible only in the southern hemisphere, on a path seemingly crafted to avoid land as much as possible.  Totality will touch down in the southwest Pacific Ocean, pass over Pitcairn Island, then finally touch land, crossing Chile and Argentina.  Totality will begin at 18:03 UTC and end at 20:42 UTC.

The Exploratorium is planning a live Webcast of the eclipse from Chile, originating from the Cerro Tololo Observatory, which totality happens to cross.  The Webcast will last for one hour, beginning at 20:00 UTC.  Occurring in early July, near the time of Earth’s aphelion, with the Moon around two days from perigee, this will be a fairly long eclipse, with four minutes and 32.8 seconds of totality at maximum eclipse in the mid-Pacific.... [Read More]

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Solar Corona Visualization, 2017 Eclipse

A total eclipse of the Sun occurred in August,2017.  Observers gathered images and manipulated them digitally.  In consequence we see the solar corona like never before. There, that is everything I know about astronomy with respect to this image, said image being presented today as NASA’s “Astronomy Picture of the Day.”  I just did want you all not to miss it.  Maybe somebody will comment!

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Now, that’s Funny

The Kepler spacecraft was launched into heliocentric orbit in 2009.  Its primary mission was to stare at a small area of the sky and monitor around 150,000 stars in its field of view (around twice the size of the bowl of the Big Dipper), watching for the subtle dimming of stars when planets orbiting them passed in front of their parent stars (a transit).  Before its retirement in October, 2018, it had discovered 2,662 exoplanets (planets orbiting stars other than the Sun).  It also saw some other, very curious things.

You may have heard about Tabby’s Star (KIC 8462852), a main sequence star which exhibits irregular deep dimmings which have, so far defied all attempts to explain them.... [Read More]

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Long-Lost First Movie of a Solar Eclipse Found, Restored

In May, 1900, British magician Nevil Maskelyne, Jr., travelled to North Carolina in the United States to observe and attempt to photograph the total eclipse of the Sun on May 28th of that year.  Maskelyne was the son of John Nevil Maskelyne, a celebrated magician who was also the inventor of the pay toilet.  (Neither should be confused with the unrelated Rev. Dr Nevil Maskelyne, the fifth British Astronomer Royal from 1765 to 1811.)  Solar eclipses had been photographed before, with the first completely successful photograph taken of the eclipse of 1851-07-28, but Maskelyne wanted to take the next step and make a motion picture of the eclipse.  He used a camera with a telescopic adapter developed by his father, which he had previously attempted to use to photograph the eclipse of 1898-01-22, but his film was stolen during the return to Britain so we’ll never know what it contained.

The film from the 1900 eclipse was stunning.  I have photographed four total solar eclipses (1999, 2001, 2008, and 2010), and even with modern equipment, dealing with the rapid and dramatic changes in light level in the seconds before and after totality is very challenging.  However Maskelyne managed to do it (nothing is known about his equipment or technique), the result was a total success, which was shown in British theatres.  The film disappeared shortly after its theatrical presentation and was believed to have been lost for over a century.  In 2018, a copy (it is unknown whether this was the original or a print) was found in the archives of the Royal Astronomical Society, whose curator did not know what it was, and upon consultation with the British Film Institute’s (BFI) curator of silent films, it was identified as the Maskelyne eclipse film.  The BFI’s conservators re-photographed the original celluloid film onto 35 millimetre film, which was then digitally scanned and restored as a 4K video.  Here is the restored film.  It is embedded here as a smaller video: click on “Watch on YouTube” to watch in full resolution.... [Read More]

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A Meteor Hits the Moon During the Eclipse

Meteor impact on the Moon, 2019-01-21During the recent lunar eclipse (the date on which it occurred depends upon your time zone: mid-eclipse was at 05:12 UTC on 2019-01-21, while the eclipse occurred on the evening of January 20th in western hemisphere time zones) several amateur astronomers capturing the eclipse on video observed a flash of light, just a single video frame, near the limb of the eclipsed Moon just at the beginning of the umbral phase.

The fact that three observers in different locations have so far reported the same flash excludes other explanations such as a reflection off an Earth satellite or a “point meteor” burning up in the Earth’s atmosphere on a trajectory pointed directly at the observer.... [Read More]

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Perseid Meteor Shower 2018

Perseid meteor, 2015-08-13

Tonight (August 12–13, 2018 UTC) the Perseid meteor shower will peak.  This meteor shower occurs every year around August 12th as the Earth passes through the orbit of debris from comet Swift-Tuttle.  This is one of the most reliable and intense meteor showers and, in ideal conditions (clear, dark sky and dark-adapted eyes) you may see a meteor a minute.  (As with everything, Pareto is on the job—there are many more dim meteors than bright ones.)... [Read More]

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