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- El Gordo
El Gordo – the fat one – might not be the most flattering name for a galaxy cluster. But it’s certainly accurate. El Gordo is the most massive cluster yet seen that’s so far away – more than seven billion light-years.
The cluster is actually two clusters that are ramming together. They contain hundreds of individual galaxies. They total about 2300 times the mass of our own galaxy, the Milky Way. Most of that mass consists of dark matter. It produces no detectable energy, but it reveals its presence through its gravitational pull on the visible matter around it.
Astronomers measure the amount of dark matter by seeing how the cluster distorts the light of background galaxies. They know the mass of the visible parts of the galaxies. They subtract that from the cluster’s gravitational mass to calculate the amount of dark matter.
El Gordo is so far away that we see it as it looked when the universe was a bit less than half its current age – about six-and-a-half billion years after the Big Bang. No other cluster at that distance or beyond is that heavy. So the cluster provides an excellent laboratory for studying galaxies and dark matter in the early universe.
El Gordo is in Phoenix, the firebird. The constellation is so far south that it’s not visible from most of the United States – only Hawaii and southern Texas and Florida. From those locations, the firebird is low in the southern sky at nightfall.
Script by Damond Benningfield
Support McDonald Observatory
3 min - El GordoEl Gordo – the fat one – might not be the most flattering name for a galaxy cluster. But it’s certainly accurate. El Gordo is the most massive cluster yet seen that’s so far away – more than seven billion light-years.The cluster is actually two clusters that are ramming together. They contain hundreds of individual galaxies. They total about 2300 times the mass of our own galaxy, the Milky Way. Most of that mass consists of dark matter. It produces no detectable energy, but it reveals its presence through its gravitational pull on the visible matter around it.Astronomers measure the amount of dark matter by seeing how the cluster distorts the light of background galaxies. They know the mass of the visible parts of the galaxies. They subtract that from the cluster’s gravitational mass to calculate the amount of dark matter.El Gordo is so far away that we see it as it looked when the universe was a bit less than half its current age – about six-and-a-half billion years after the Big Bang. No other cluster at that distance or beyond is that heavy. So the cluster provides an excellent laboratory for studying galaxies and dark matter in the early universe.El Gordo is in Phoenix, the firebird. The constellation is so far south that it’s not visible from most of the United States – only Hawaii and southern Texas and Florida. From those locations, the firebird is low in the southern sky at nightfall. Script by Damond Benningfield3 min
- Shorter Cycles
During the Little Ice Age, much of the northern hemisphere was plunged into a deep freeze. Winters were so cold that the Thames River in England froze over, and the Vikings had to abandon their settlements in Greenland. Summers were chilly, rainy, and gloomy – perhaps helping inspire Mary Shelley to write “Frankenstein.”
That era incorporates a time when the Sun was especially quiet. Known as the Maunder Minimum, it lasted from about 1645 to 1715. Astronomers recorded few sunspots then — they sometimes went months or years without seeing a single one. With less activity, the Sun emits less energy. That suggests the Sun could be at least partially responsible for the Little Ice Age.
A recent study found that not only was the Sun especially quiet during that era, but its cycle of magnetic activity was especially short.
At the peak of a solar cycle, the Sun is covered with many sunspots, and it produces big explosions of gas and energy. The cycle lasts an average of about 11 years, although it can vary by a couple of years either way. The study found that the cycles during the Maunder Minimum lasted only about eight years.
Researchers looked at records of auroras kept by Korean astronomers. Auroras are created by particles from the Sun, so their intensity and location can reveal the Sun’s activity level. The study found a clear eight-year cycle in the records – a short cycle during an era that was short on warmth.
Script by Damond Benningfield
Support McDonald Observatory
3 min - Shorter CyclesDuring the Little Ice Age, much of the northern hemisphere was plunged into a deep freeze. Winters were so cold that the Thames River in England froze over, and the Vikings had to abandon their settlements in Greenland. Summers were chilly, rainy, and gloomy – perhaps helping inspire Mary Shelley to write “Frankenstein.”That era incorporates a time when the Sun was especially quiet. Known as the Maunder Minimum, it lasted from about 1645 to 1715. Astronomers recorded few sunspots then — they sometimes went months or years without seeing a single one. With less activity, the Sun emits less energy. That suggests the Sun could be at least partially responsible for the Little Ice Age.A recent study found that not only was the Sun especially quiet during that era, but its cycle of magnetic activity was especially short.At the peak of a solar cycle, the Sun is covered with many sunspots, and it produces big explosions of gas and energy. The cycle lasts an average of about 11 years, although it can vary by a couple of years either way. The study found that the cycles during the Maunder Minimum lasted only about eight years.Researchers looked at records of auroras kept by Korean astronomers. Auroras are created by particles from the Sun, so their intensity and location can reveal the Sun’s activity level. The study found a clear eight-year cycle in the records – a short cycle during an era that was short on warmth. Script by Damond Benningfield3 min
- Moon and Jupiter
Jupiter has been described as the vacuum cleaner of the solar system. The planet’s powerful gravity sucks in comets and asteroids. They’re destroyed as they slam into Jupiter’s atmosphere. That keeps those objects from possibly threatening Earth and the other inner planets.
Scientists have seen several of these impacts. They’ve seen some of them directly, as bright flashes of light. For others, they’ve seen the aftermath — big, dark scars in Jupiter’s atmosphere.
One of the most recent impacts came last summer. Amateur astronomers in Asia saw a bright flash of light on August 28th. One of them even recorded the flash on video. It lasted several seconds.
An early analysis said the flash was similar to another one a couple of years earlier. It probably was the equivalent of a blast on Earth in 1908. Known as the Tunguska event, it occurred when an asteroid or comet exploded in the upper atmosphere. It leveled hundreds of square miles of Siberian forest.
The biggest impact yet seen on Jupiter took place in 1994. Jupiter’s gravity pulled apart a large comet. It then pulled in the remains, which created about a dozen big blasts. The scars from those impacts were visible for months.
Jupiter keeps company with the Moon the next couple of nights. It looks like a brilliant star. It’s to the left or upper left of the Moon tonight, and closer below the Moon tomorrow night.
Script by Damond Benningfield
Support McDonald Observatory
3 min - Moon and JupiterJupiter has been described as the vacuum cleaner of the solar system. The planet’s powerful gravity sucks in comets and asteroids. They’re destroyed as they slam into Jupiter’s atmosphere. That keeps those objects from possibly threatening Earth and the other inner planets.Scientists have seen several of these impacts. They’ve seen some of them directly, as bright flashes of light. For others, they’ve seen the aftermath — big, dark scars in Jupiter’s atmosphere.One of the most recent impacts came last summer. Amateur astronomers in Asia saw a bright flash of light on August 28th. One of them even recorded the flash on video. It lasted several seconds.An early analysis said the flash was similar to another one a couple of years earlier. It probably was the equivalent of a blast on Earth in 1908. Known as the Tunguska event, it occurred when an asteroid or comet exploded in the upper atmosphere. It leveled hundreds of square miles of Siberian forest.The biggest impact yet seen on Jupiter took place in 1994. Jupiter’s gravity pulled apart a large comet. It then pulled in the remains, which created about a dozen big blasts. The scars from those impacts were visible for months.Jupiter keeps company with the Moon the next couple of nights. It looks like a brilliant star. It’s to the left or upper left of the Moon tonight, and closer below the Moon tomorrow night. Script by Damond Benningfield3 min
- Superflare!The star V1355 Orionis is a hothead. It pops off all the time — giant eruptions of energy and particles. All of them are superflares — many times more powerful than any eruption ever seen from the Sun. And a few years ago, the star produced one of the most powerful superflares ever seen from any star.V1355 is a binary — two stars locked in orbit around each other. One of the stars is similar to the Sun. But the other is bigger, heavier, brighter, and much more active.That star spins quickly. The rapid rotation generates a powerful magnetic field. The lines of magnetic force tangle, then snap. When the lines reconnect, the star produces giant outbursts.In December of 2020, it produced its biggest yet seen. The superflare blasted trillions of tons of material into space. And the cloud was moving at a couple of million miles per hour or faster — fast enough to escape the star and zip into interstellar space.Such a flare would be bad news for any planets in orbit around the star. It could erode some of a planet’s atmosphere like a rock wall hit with a sandblaster. It could also zap the surface with X-rays and other high-energy radiation. So any planets in the system are likely to be lifeless — blasted by V1355 Orionis.The system is about 400 light-years away, in Orion. The constellation is in the east and southeast at nightfall. Script by Damond Benningfield3 min
- BetelgeuseBetelgeuse will blast itself to bits as a supernova. Many astronomers agree that that’s likely to happen within the next hundred thousand years. But estimates of the exact timing range from the full hundred thousand years to as little as a few decades.Betelgeuse marks the shoulder of Orion the hunter. The bright orange star is in the east at nightfall, to the left of Orion’s three-star belt.In late 2019, the supergiant star blew out a huge blob of gas. The gas cooled and condensed, forming a dark cloud that made the star fade to a third of its normal brightness. Betelgeuse rebounded, then grew almost 50 percent brighter than normal last year.The timing of the supernova depends on what’s happening in the star’s core, which we can’t see. It may be “fusing” helium to make carbon. But it could be fusing carbon to make heavier elements. If so, then the star’s demise could come fairly soon.A study last year suggested that Betelgeuse is late in the carbon-fusion process. After that stage, it’ll “burn” through a series of elements, ending with iron. At that point, the core will collapse, and the star’s outer layers will blast into space. The study said that, if Betelgeuse is deep into the carbon-burning process, it could explode in a few centuries — or perhaps even a few decades. For now, all we know for sure is that Betelgeuse faces a spectacular demise — sometime in the next hundred thousand years. Script by Damond Benningfield3 min
- Guiding LightsSeveral especially bright stars highlight the eastern sky on January evenings. The list includes Betelgeuse and Rigel in Orion, Pollux and Castor in Gemini, and the brightest star of all, Sirius, in the big dog.For millennia, these and other stars were guiding lights, helping people find their way around the world — and beyond.Celestial navigation combines observations of the positions of two or more stars or other celestial bodies, precise timing, and some calculations. A skilled navigator can use the technique to reach a destination with a high degree of accuracy — to within a few hundred yards and a couple of minutes.Centuries ago, Polynesian sailors used the technique to island-hop across the Pacific Ocean. European explores used it to find their way to the Americas and the Far East. American sailors used it as well, plying the world’s oceans in times of war and peace. And Apollo astronauts used it to help them get to the Moon.With the advent of GPS in the 1980s and ’90s, though, celestial navigation began to die off. GPS is easier to use and more accurate. The United States Naval Academy even dropped celestial navigation from its classes.But a few years ago, the academy restored its training — in part because technology can fail or be blocked. All midshipmen receive a basic introduction, while navigators get more advanced training – in finding their way with the help of the stars. Script by Damond Benningfield3 min
- Moon and SaturnWhen big storms on Earth are done, they leave little trace in the atmosphere that they ever existed. On Saturn, though, big storms appear to leave traces even centuries after they faded from sight.Saturn is the second-largest planet in the solar system — a ball of gas more than nine times the diameter of Earth. Its atmosphere is generally pretty bland — a few ribbons of clouds in shades of white, yellow, and tan. Every couple of decades, though, a giant storm breaks out. It can wrap all the way around the planet, and remain visible for months or years.But a recent study found that the storms leave a long-lasting imprint.Scientists used an array of radio telescopes in New Mexico to look for ammonia in Saturnian skies. They found regions where there was little ammonia high in the sky, but a lot at lower altitudes. All of those regions seemed to match the locations of the giant storms recorded since 1876 — with the possible imprint of one from centuries earlier.The big storms might have caused ammonia high in the atmosphere to cool and condense, forming big “mushballs” of ice. The mushballs fell dozens of miles into the atmosphere. They vaporized, adding their ammonia to the lower altitudes — leaving traces of long-gone storms.Saturn looks like a bright star, and is especially easy to find right now. It’s above the Moon as darkness falls tonight, and to the lower right of the Moon tomorrow night. Script by Damond Benningfield3 min
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StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.
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