Penumbral Lunar Eclipse: July 4 – 5

NASA Solar and Earth images, illustration by James Guilford.
A penumbral lunar eclipse occurs when the Moon passes through the thin outer portion of the shadow Earth casts out into space.

We’re fortunate that the night of July 4 is expected to be clear, and not just for the traditional booms and flashes of celebratory fireworks. Our Moon is getting in on the act, albeit with a much more subtle display in the form of a penumbral eclipse. The eclipse will take place from 11:07 PM to 1:52 AM EDT with maximum eclipse at 12:31 AM July 5.

We say subtle because, unlike a total lunar eclipse, Earth’s Moon will not change to reddish/coppery colors. The Moon will instead become oddly shadowed for a Full Moon, as it enters the outer fringes of Earth’s shadow in space — the penumbra. Only the “top” portion of Luna will pass through the penumbra making this eclipse especially slight. Still, it’s worth a look and it won’t be at a particularly late hour. A deeper penumbral lunar eclipse will take place the night of November 30, 2020.

Moon is eclipsed when it passes through Earth's shadow. Credit: SkySafari / J. Guilford
Earth’s shadow runs away from the Sun into space and has two parts: the deep inner shadow or umbra, and the thin outer portion called the penumbra. The Moon is eclipsed when it passes through Earth’s shadow. Credit: SkySafari / J. Guilford

While it’s possible to view this eclipse with the unaided eye, binoculars will provide an enhanced view as would a small telescope.

Penumbral Lunar Eclipse of July 4 – 5, 2020 at Maximum Eclipse: 12:31 AM EDT. Simulation via SkySafari

And just in case there’s any confusion, lunar eclipses are perfectly safe to view and photograph — it’s moonlight — so nothing to worry about there.

If you shoot any photos or have impressions to share with us, you can do so via our Twitter — @Cuyastro

Penumbral Lunar Eclipse of July 4 – 5, 2020. Credit: NASA

NASA Eclipse Page available here: Penumbral Lunar Eclipse of July 4 – 5, 2020.


June 8 Membership Meeting Zoomed!

Members of the Cuyahoga Astronomical Association (CAA) have been unable to meet in person. To move forward and present the year’s lineup of excellent program speakers, the June 8 meeting was conducted via Zoom, the popular video conferencing service.

Since this was the CAA’s first effort at a video conference meeting, the event was advertised to members only. At peak 27 members attended and were treated to a Powerpoint-illustrated talk by Benjamin Monreal, Professor of Physics and Astronomy at Case Western Reserve University. The subject was “Engineering and Imaging in the Largest Telescopes” Besides explaining how the world’s largest telescopes sharply focus light from distant stars, Dr. Monreal described his own unique concept for a ground-based instrument.

One advantage of video conferencing, besides seeing into member’s homes and watching cats “play dead,” is that the meetings are recorded. If you were unable to participate or simply want to see the proceedings, play the video we have embedded above.


Nearest black hole to Earth found 1,000 light-years distant

This artist’s impression shows the orbits of the objects in the HR 6819 triple system. Image Credit: ESO/L. Calçada

May 6 — A team of astronomers from the European Southern Observatory (ESO) and other institutes has discovered a black hole lying just 1,000 light-years from Earth. The black hole is closer to our Solar System than any other found to date and forms part of a triple system that can be seen with the naked eye. The team found evidence for the invisible object by tracking its two companion stars using the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile. They say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.

“We were totally surprised when we realized that this is the first stellar system with a black hole that can be seen with the unaided eye,” says Petr Hadrava, Emeritus Scientist at the Academy of Sciences of the Czech Republic in Prague and co-author of the research. Located in the constellation of Telescopium, the system is so close to us that its stars can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope. “This system contains the nearest black hole to Earth that we know of,” says ESO scientist Thomas Rivinius, who led the study published today in Astronomy & Astrophysics.

The team originally observed the system, called HR 6819, as part of a study of double-star systems. However, as they analyzed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole. The observations with the FEROS spectrograph on the MPG/ESO 2.2-meter telescope at La Silla showed that one of the two visible stars orbits an unseen object every 40 days, while the second star is at a large distance from this inner pair.

Dietrich Baade, Emeritus Astronomer at ESO in Garching and co-author of the study, says: “The observations needed to determine the period of 40 days had to be spread over several months. This was only possible thanks to ESO’s pioneering service-observing scheme under which observations are made by ESO staff on behalf of the scientists needing them.”

The hidden black hole in HR 6819 is one of the very first stellar-mass black holes found that do not interact violently with their environment and, therefore, appear truly black. But the team could spot its presence and calculate its mass by studying the orbit of the star in the inner pair. “An invisible object with a mass at least four times that of the Sun can only be a black hole,” concludes Rivinius, who is based in Chile.

This chart shows the location of the HR 6819 triple system, which includes the closest black hole to Earth, in the constellation of Telescopium. This map shows most of the stars visible to the unaided eye under good conditions and the system itself is marked with a red circle. While the black hole is invisible, the two stars in HR 6819 can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope. Credit: ESO, IAU and Sky & Telescope

Astronomers have spotted only a couple of dozen black holes in our galaxy to date, nearly all of which strongly interact with their environment and make their presence known by releasing powerful X-rays in this interaction. But scientists estimate that, over the Milky Way’s lifetime, many more stars collapsed into black holes as they ended their lives. The discovery of a silent, invisible black hole in HR 6819 provides clues about where the many hidden black holes in the Milky Way might be. “There must be hundreds of millions of black holes out there, but we know about only very few. Knowing what to look for should put us in a better position to find them,” says Rivinius. Baade adds that finding a black hole in a triple system so close by indicates that we are seeing just “the tip of an exciting iceberg.”

Already, astronomers believe their discovery could shine some light on a second system. “We realized that another system, called LB-1, may also be such a triple, though we’d need more observations to say for sure,” says Marianne Heida, a postdoctoral fellow at ESO and co-author of the paper. “LB-1 is a bit further away from Earth but still pretty close in astronomical terms, so that means that probably many more of these systems exist. By finding and studying them we can learn a lot about the formation and evolution of those rare stars that begin their lives with more than about 8 times the mass of the Sun and end them in a supernova explosion that leaves behind a black hole.”

The discoveries of these triple systems with an inner pair and a distant star could also provide clues about the violent cosmic mergers that release gravitational waves powerful enough to be detected on Earth. Some astronomers believe that the mergers can happen in systems with a similar configuration to HR 6819 or LB-1, but where the inner pair is made up of two black holes or of a black hole and a neutron star. The distant outer object can gravitationally impact the inner pair in such a way that it triggers a merger and the release of gravitational waves. Although HR 6819 and LB-1 have only one black hole and no neutron stars, these systems could help scientists understand how stellar collisions can happen in triple star systems.

Hubble Space Telescope at 30

Deep space image from Hubble Space Telescope
This image is one of the most photogenic examples of the many turbulent stellar nurseries the NASA/ESA Hubble Space Telescope has observed during its 30-year lifetime. The portrait features the giant nebula NGC 2014 and its neighbor NGC 2020 which together form part of a vast star-forming region in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, approximately 163,000 light-years away. Credit: NASA, ESA, and STScI