When Moon, Venus, and a Beehive got together

Conjunction of Earth’s Moon and planet Venus with M44 as a bonus! September 14, 2020. Photo by Frank Shoemaker.

CAA member Frank Shoemaker, despite challenging seeing conditions and the early hour, captured a fine image of the September 14 conjunction of Earth’s Moon and planet Venus. As luck would have it, the conjunction occurred in constellation Cancer home of the lovely open cluster M44, the “Beehive”. The technical info.: Canon EOS 6D Mark 2, 100mm, f/4.5, 19 seconds, 5:29 a.m. Eastern Daylight Time.

Possible sign of life detected in the atmosphere of Venus

This artistic illustration depicts the Venusian surface and atmosphere. Credit: ESO/M. Kornmesser

An international team of astronomers today announced the discovery of a rare molecule — phosphine — in the clouds of Venus. On Earth, this gas is only made industrially or by microbes that thrive in oxygen-free environments. Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes — floating free of the scorching surface but needing to tolerate very high acidity. The detection of phosphine could point to such extra-terrestrial “aerial” life. Confirming the presence of life, however, will require much more work.

“When we got the first hints of phosphine in Venus’s spectrum, it was a shock!”, says team leader Jane Greaves of Cardiff University in the UK, who first spotted signs of phosphine in observations from the James Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory, in Hawaiʻi. Confirming their discovery required using 45 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, a more sensitive telescope in which the European Southern Observatory (ESO) is a partner. Both facilities observed Venus at a wavelength of about 1 millimeter, much longer than the human eye can see — only telescopes at high altitude can detect it effectively.

The international team, which includes researchers from the UK, US and Japan, estimates that phosphine exists in Venus’s clouds at a small concentration, only about twenty molecules in every billion. Following their observations, they ran calculations to see whether these amounts could come from natural non-biological processes on the planet. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. These non-biological sources were found to make at most one ten thousandth of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine (which consists of hydrogen and phosphorus) on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to the team. Earth bacteria are known to make phosphine: they take up phosphate from minerals or biological material, add hydrogen, and ultimately expel phosphine. Any organisms on Venus will probably be very different to their Earth cousins, but they too could be the source of phosphine in the atmosphere.

While the discovery of phosphine in Venus’s clouds came as a surprise, the researchers are confident in their detection. “To our great relief, the conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was tricky, though, as ALMA isn’t usually looking for very subtle effects in very bright objects like Venus,” says team member Anita Richards of the UK ALMA Regional Centre and the University of Manchester. “In the end, we found that both observatories had seen the same thing — faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below,” adds Greaves, who led the study published today in Nature Astronomy.

Another team member, Clara Sousa Silva of the Massachusetts Institute of Technology in the US, has investigated phosphine as a “biosignature” gas of non-oxygen-using life on planets around other stars, because normal chemistry makes so little of it. She comments: “Finding phosphine on Venus was an unexpected bonus! The discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% of acid in their environment — but the clouds of Venus are almost entirely made of acid.”

The team believes their discovery is significant because they can rule out many alternative ways to make phosphine, but they acknowledge that confirming the presence of “life” needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly acidic — around 90% sulfuric acid — posing major issues for any microbes trying to survive there.

ESO astronomer and ALMA European Operations Manager Leonardo Testi, who did not participate in the new study, says: “The non-biological production of phosphine on Venus is excluded by our current understanding of phosphine chemistry in rocky planets’ atmospheres. Confirming the existence of life on Venus’s atmosphere would be a major breakthrough for astrobiology; thus, it is essential to follow-up on this exciting result with theoretical and observational studies to exclude the possibility that phosphine on rocky planets may also have a chemical origin different than on Earth.”

More observations of Venus and of rocky planets outside our Solar System, including with ESO’s forthcoming Extremely Large Telescope, may help gather clues on how phosphine can originate on them and contribute to the search for signs of life beyond Earth.

The mystery of dimming Betelgeuse solved?

New observations by the NASA/ESA Hubble Space Telescope suggest that the unexpected dimming of the supergiant star Betelgeuse was most likely caused by a dust cloud that blocked starlight coming from the star’s surface. This artist’s impression was generated using an image of Betelgeuse from late 2019 taken with the SPHERE instrument on the European Southern Observatory’s Very Large Telescope. Credit: ESO, ESA/Hubble, M. Kornmesser

New observations by the NASA/ESA Hubble Space Telescope suggest that the unexpected dimming of the supergiant star Betelgeuse was most likely caused by an immense amount of hot material ejected into space, forming a dust cloud that blocked starlight coming from Betelgeuse’s surface.

Betelgeuse is an aging, red supergiant star that has swelled in size as a result of complex, evolving changes in the nuclear fusion processes in its core. The star is so large that if it replaced the Sun at the center of our Solar System, its outer surface would extend past the orbit of Jupiter. The unprecedented phenomenon of Betelgeuse’s great dimming, eventually noticeable to even the naked eye, began in October 2019. By mid-February 2020, the brightness of this monster star had dropped by more than a factor of three.

This sudden dimming has mystified astronomers, who sought to develop theories to account for the abrupt change. Thanks to new Hubble observations, a team of researchers now suggest that a dust cloud formed when superhot plasma was unleashed from an upwelling of a large convection cell on the star’s surface and passed through the hot atmosphere to the colder outer layers, where it cooled and formed dust. The resulting cloud blocked light from about a quarter of the star’s surface, beginning in late 2019. By April 2020, the star had returned to its normal brightness.

Several months of Hubble’s ultraviolet-light spectroscopic observations of Betelgeuse, beginning in January 2019, produced an insightful timeline leading up to the star’s dimming. These observations provided important new clues to the mechanism behind the dimming. Hubble saw dense, heated material moving through the star’s atmosphere in September, October, and November 2019. Then, in December, several ground-based telescopes observed the star decreasing in brightness in its southern hemisphere.

“With Hubble, we see the material as it left the star’s visible surface and moved out through the atmosphere, before the dust formed that caused the star appear to dim,” said lead researcher Andrea Dupree, associate director of The Center for Astrophysics | Harvard & Smithsonian. “We could see the effect of a dense, hot region in the southeast part of the star moving outward.”

“This material was two to four times more luminous than the star’s normal brightness,” she continued. “And then, about a month later, the southern hemisphere of Betelgeuse dimmed conspicuously as the star grew fainter. We think it is possible that a dark cloud resulted from the outflow that Hubble detected. Only Hubble gives us this evidence of what led up to the dimming.”

The team began using Hubble early last year to analyze the massive star. Their observations are part of a three-year Hubble study to monitor variations in the star’s outer atmosphere. The telescope’s sensitivity to ultraviolet light  allowed researchers to probe the layers above the star’s surface, which are so hot that they emit mostly in the ultraviolet region of the spectrum and are not seen in visible light. These layers are heated partly by the star’s turbulent convection cells bubbling up to the surface.

“Spatially resolving a stellar surface is only possible in favorable cases and only with the best available equipment,” said Klaus Strassmeier of the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany. “In that respect, Betelgeuse and Hubble are made for each other.”

This is the first direct image of a star other than the Sun, made with the Hubble Space Telescope. Called Alpha Orionis, or Betelgeuse, it is a red supergiant star marking the shoulder of the winter constellation Orion the Hunter. The Hubble image reveals a huge ultraviolet atmosphere with a mysterious hot spot on the stellar behemoth’s surface. The enormous bright spot, which is many hundreds times the diameter of Sun, is at least 2,000 Kelvin degrees hotter than the surface of the star. Credit: Andrea Dupree (Harvard-Smithsonian CfA), Ronald Gilliland (STScI), NASA and ESA

Hubble spectra, taken in early and late 2019 and in 2020, probed the star’s outer atmosphere by measuring spectral lines of ionized magnesium. From September to November 2019, the researchers measured material passing from the star’s surface into its outer atmosphere. This hot, dense material continued to travel beyond Betelgeuse’s visible surface, reaching millions of kilometers from the star. At that distance, the material cooled down enough to form dust, the researchers said.

This interpretation is consistent with Hubble ultraviolet-light observations in February 2020, which showed that the behavior of the star’s outer atmosphere returned to normal, even though in visible light it was still dimming.

Although Dupree does not know the cause of the outburst, she thinks it was aided by the star’s pulsation cycle, which continued normally though the event, as recorded by visible-light observations. Strassmeier used an automated telescope of the Leibniz Institute for Astrophysics called STELLar Activity (STELLA)  to measure changes in the velocity of the gas on the star’s surface as it rose and fell during the pulsation cycle. The star was expanding in its cycle at the same time as the  convective cell was upwelling. The pulsation rippling outward from Betelgeuse may have helped propel the outflowing plasma through the atmosphere.

The red supergiant is destined to end its life in a supernova blast and some astronomers think the sudden dimming may be a pre-supernova event. The star is relatively nearby, about 725 light-years away, so the dimming event would have happened around the year 1300, as its light is just reaching Earth now.

Dupree and her collaborators will get another chance to observe the star with Hubble in late August or early September. Right now, Betelgeuse is in the daytime sky, too close to the Sun for Hubble observations.

Dick Goddard: A brief remembrance

Dick Goddard: 1931 – 2020

Broadcast meteorology icon Dick Goddard passed away August 4, 2020 at age 89 after battling illness. In addition to being a legendary weather forecaster in Cleveland, and a noted advocate for animal welfare, many remember him as inspiring them to look up. CAA member Jay Reynolds shared some thoughts on Goddard and astronomy.

Sure, Dick had the longest TV meteorologist career in history.*

His accomplishments are many.

{In} his first weather segments, in the early 1960s, he knew there may be not enough to talk about. His director suggested that talk about something, trivia or whatever.  He started looking up trivia, which also included astronomy.

Dick Goddard at the 2012 Transit of Venus event.

For decades, if time permitted, he would always throw out something interesting for viewers to see.

Always hungry for a chance to interact with people, just ask him, he’d come to events or included others in them.

He attended the CAA’s “2012 Transit of Venus Event” at Edgewater Park (7,500 people). Also spoke at Cleveland Astronomical Society.

He always pushed astronomy, science to anyone who would listen.

He loved to make those connections.

Jay Reynolds is Research Astronomer at Cleveland State University, director of the CAA’s Observatory, and a member of the CAA Board of Trustees.

*Dick Goddard holds the Guinness World Record for longest career as a weather forecaster after passing Canadian meteorologist Peter Coade. https://en.wikipedia.org/wiki/Dick_Goddard