The Hubble recovery team thinks it’s finally tracked down a problem that’s kept the space telescope out of commission for over a month.
The problem started on June 13, when an onboard computer suddenly ground to a halt. All science instruments on Hubble went into safe mode as a result, and it’s been that way ever since. The telescope is otherwise fine, but normal operations have been suspended.
The problem is with the payload computer, which controls and monitors Hubble’s science instruments. It’s the most serious glitch to afflict Hubble in years, raising concerns that the aging telescope might finally be finished. Launched in 1990, Hubble has conducted over 1.5 million observations and contributed significantly to our understanding of the solar system, galaxies, and the universe in general.
The Hubble recovery team has tried all sorts of tests over the past few weeks (a running list of measures taken can be seen here), along with attempts to restart and reconfigure the payload computer, but nothing has worked. Data collected during these attempts has now led the team to determine that the “possible cause” of the glitch has something to do with the Power Control Unit (PCU) located on the telescope’s Science Instrument Command and Data Handling unit, according to NASA.
The PCU supplies electricity to the payload computer. Equipped with a power regulator, the PCU provides a steady 5 volts of electricity to both the payload computer and its memory modules. As NASA explains:
A secondary protection circuit senses the voltage levels leaving the power regulator. If the voltage falls below or exceeds allowable levels, this secondary circuit tells the payload computer that it should cease operations. The team’s analysis suggests that either the voltage level from the regulator is outside of acceptable levels (thereby tripping the secondary protection circuit), or the secondary protection circuit has degraded over time and is stuck in this inhibit state.
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Commands to reset the PCU haven’t worked, so it’s probably borked. In response, NASA management has approved a plan to switch over to backup hardware. This rescue operation is scheduled to start today, and it could take a few days to complete.
Hubble has experienced a slew of problems over the years, but NASA always seems to find a way to bring the telescope back. Hubble may be old, but it’s expected to remain in operation until the 2030s. Should all go well, and should Hubble return to service, it could serve alongside the upcoming James Webb Space Telescope, which is scheduled to launch later this year.
For the first time, astronomers have obtained large-scale images of the cosmic web — the incredibly ancient scaffolding of dark matter and hydrogen gas out of which galaxies in the Universe were formed.
This material is so far away and so incredibly faint that it took one of the largest telescopes in the world coupled with one of the most powerful cameras to see it at all. But what they found in their images was the very framework of the Universe.
The Universe formed about 13.8 billion years in a sudden and colossal burst of expanding space and energy. In many ways it was like an explosion, though an explosion of space, not in space: It was the creation of space itself. It was crammed full of energy and matter, and the distribution wasn’t smooth. Some places had a teeny bit more matter in them than others. These over- and under-dense regions were incredibly small; a typical denser spot might be 1 part in 100,000 more dense than its neighbor. But that was enough to create all the structure we see in the Universe today.
These overdense regions had enough gravity to overcome the expansion of the Universe, and began to collapse. Dark matter — a still mysterious substance that doesn’t react with or emit light, but has mass and gravity — attracted material around it, and started forming long, thin, interconnecting filaments of material, like a web. “Normal” matter, the stuff we’re made of, was pulled toward these filaments, and collected on them. Matter flowed along the filaments due to gravity, piling up and forming galaxies, clusters of galaxies, and even immense superclusters, clusters of galaxy clusters, the largest scale structures in the known Universe.
All these from tiny fluctuations in the fabric of space!
Video of A Brief History of the Universe: Crash Course Astronomy #44
The problem is seeing this original structure, the original filaments that formed the cosmic web. They’d be loaded with hydrogen gas and glowing, but this all happened so long ago that it has taken over 13 billion years for the light from them to reach us. They’re faint. There’s been some success in detecting them, though.
Quasars, intensely bright galaxies blasting out radiation as their central supermassive black holes gobble down matter, can be used to find them, for example. As the quasar light passes through that primordial hydrogen gas, some of the light is absorbed in characteristics ways, and we can see that absorption in the quasar light. But that only shows you where that gas is in an extremely narrow spot on the sky, and even if you do this with hundreds of quasars the map you get is literally spotty.
Some of that gas has also been seen glowing (what we say is in emission), but only near where bright galaxies are lighting it up. Again, it’s a very localized detection in a special location. What astronomers needed was a map of this material in typical spots in the Universe, representative of the cosmos as a whole.
And that’s what they now have. A few years ago astronomers used the massive 8.2-meter Very Large Telescope (VLT) with the MUSE camera to look at the same spot in the sky Hubble observed to create the the Ultra-Deep Field, an area of the sky about the same size as a grain of sand held at arm’s length… but in which Hubble saw over 10,000 galaxies.
When they observed this field with VLT/MUSE they saw lots of hydrogen gas, so they were encouraged to take deeper observations. Much deeper: Over the course of 8 months they took a staggering 140 hours of usable images on that single spot on the sky. And these weren’t just images, either. They took spectra, breaking the light up into individual colors. Hot hydrogen gas in the early Universe glows at a characteristic color in the ultraviolet called Lyman-α (Lyman-alpha, or LyA for short). By the time this light reaches us billion of years later it’s redshifted to the near-infrared. By looking at the exact wavelength observed, the redshift and therefore the distance to that LyA gas can be determined.
And what they found were long filaments of glowing hydrogen gas, some of it over 13 billion light years away, structures forming when the cosmos was less than a billion years old!
They actually found clumps and filaments from 11.5 to 13+ billion light years away from Earth, some of them well over 10 million light years long and only a few hundred thousand light years wide. They found over 1,250 individual spots where LyA was emitted, some of which were grouped into 22 large overdense regions of LyA emission which had between 10 and 26 distinct clumps in them. Those clumps represent galaxies and clusters in the very earliest stages of forming, not long after the formation of the Universe itself.
It gets better. They also found lots of fuzzy LyA emission well outside those clumps, what’s called extended emission. Simulations of the way matter clumped together in the very early days of the Universe indicate this extended emission is caused by the birth of billions of dwarf galaxies, ones much smaller than our own Milky Way. These are called ultra-low luminosity emitters because they’re extremely faint, some only a few thousand times the brightness of our Sun. Given that the Milky Way is many billions of times more luminous than the Sun you can appreciate how faint these dwarf galaxies are, and how many of them there must be to light up that diffuse gas.
These galaxies are extremely young; we see the light from them when they were less than 300 million years old. Again, for comparison, the Milky Way is over 12 billion years old, so we are seeing a slice of the Universe when it was practically an infant.
On top of all this they found that of all their sources in the VLT/MUSE data, 30% were not seen in the Hubble Ultra Deep Field, meaning these are even fainter objects than Hubble could spot. That’s not hugely surprising, since VLT is far larger than Hubble and can collect more light. But it’s still quite the achievement.
As an astronomer I’m amazed that all of this was even possible to do, let alone find that it matches simulations of the way we think the early Universe would behave. That’s a critical point: Using just math, physics, and observations of the sky, we’ve been able to predict what the Universe was like when it was very young… and find that we’re right!
I hear people denigrating science all the time, poo-pooing results as mere guesses. But it is in fact and in truth the best method we have to understand objective reality, that which exists outside of us. It is a phenomenally successful method, and these new observations are more evidence of that
You may deny science if you like, but you’re going up against the Universe itself. You might want to think carefully on that position.
In June 2019, the automated survey ATLAS (Asteroid Terrestrial-impact Last Alert System) found a new object moving against the background stars. Initially called 2019 LD2, it was thought to be an asteroid orbiting the Sun out near Jupiter. However, an amateur astronomer noticed it appeared to be fuzzy, not point-like, which means it was more like a comet: Icy material on the surface turning into a gas as it’s warmed by the Sun.
Checking archived images, astronomers determined it had been “active” for several months at least. The name of the object was then changed to P/2019 LD2, indicating its status as a periodic comet.
Images by other observatories confirmed this, including Hubble. When they looked at the comet in April 2020 they saw it sporting quite a grand tail, extending for about 600,000 kilometers, nearly twice the distance of the Moon from the Earth! Mind you, the nucleus — the solid part of the comet — is probably only about 4 kilometers across.
Calculations show that around that time it was losing about 80 kilograms of water ice per second. It was also shedding gases like carbon monoxide (about 50 kilos/second), carbon dioxide (7 kilos/second) and diatomic carbon (two carbon atoms bound together; at a rate of 40 grams per second).
That may sound like a lot, but it turns out it just started outgassing like this… and it won’t for very long. It’s status as a periodic comet is only temporary. Extremely temporary: Follow-up measurements to determine its orbit found it’s actually in a similar orbit as Jupiter, and there’s an excellent chance that, in the distant future, the mighty gravity of the giant planet will fling the comet out of the solar system entirely.
When that happens it will become an interstellar comet like 2I/Borisov or ‘Oumuamua, interstellar objects that both recently passed through our solar system (and which, I’ll note, are not alien spaceships).
That’s fitting, since it probably began life in the outer reaches of the solar system, too.
It’s likely that P/2019 LD2 started out as what’s called a Trans-Neptunian Object, an icy body orbiting the Sun in the Kuiper Belt out past Neptune. Over time, very gentle nudges by Neptune’s gravity urged it into a smaller orbit, closer to the Sun. Eventually it got close enough that Neptune could yank on it much harder, changing its orbit substantially, putting it in an orbit between that of Jupiter and Neptune (from about 800 million to 3 billion kilometers from the Sun). Objects on orbits like that are called Centaurs.
Centaurs are interesting. Over time, the gas giants tend to change their orbits still more. Generally, after a few million years in this part of the solar system, they get too close to one of the planets. Either they get dropped down into the inner solar system (and become what we call Jupiter Family Comets) or get thrown out of the solar system entirely. Because of that we call them transitional objects*.
What will be the fate of P/2019 LD2? And where did it originally come from?
Observations over time of an object can be used to determine its orbit, which can then be projected into the past and future. The problem is we can’t measure the orbit exactly; there’s always some uncertainty in it. The farther you try to predict its position in the future (or antedict its position in the past) the fuzzier it gets, the bigger the volume of space it might occupy. That makes this sort of prognostication dicey.
To get around this, astronomers did something clever: They simulated its orbit using what’s called a Monte Carlo technique. They take the physical characteristics of the orbit (the shape, the distance from the Sun, the tilt, and so on) and then change each one very slightly, creating a slightly different orbit. They then run that into the past and future and see what it does. They do this again and again, creating a virtual cohort of objects each with marginally different paths. This way, you get a more statistical idea of what the history and future of the object was and will be.
What they found for P/2019 LD2 is that it probably only entered Jupiter’s space about 2.5 years ago! Before that it was a standard-issue Centaur, but got nudged into its current orbit very recently.
And its future? They found it likely that it will only stay in its current orbit for 8 or 9 more years. After that it will likely drop down into the inner solar system, becoming a Jupiter Family Comet. This means is that it’s only making a pit stop near Jupiter.
Even that’s temporary. It has a 50% of being ejected from the solar system in 340,000 years, which rises to 95% in 4 million years.
It’s likely that, over the age of the solar system, billions of objects like this have been ejected. And there are billions of stars like the Sun… which is why astronomers think the galaxy is loaded with rogue interstellar iceballs like P/2019 LD2, and why it’s not so surprising that we see them passing through our solar system, too.
Will some alien scientists in the distant future see LD2 passing through their own system? What would they make of it? It’s fun, and oddly reassuring, to know that pieces of our neighborhood will be scattered among the stars, going from citizens of our solar system to citizens of the galaxy.
*Which is pretty cool it worked out that way, given that they’re named after mythical half-human/half-horse creatures.
Floating in a stream of young stars, astronomers have spotted a trio of neighboring planets similar to Earth, orbiting a much younger version of our own sun.
The team found the young, hot worlds using observations from NASA’s Transiting Exoplanet Survey Satellite (TESS), according to a new study in The Astronomical Journal. The planets are orbiting a star called TOI 451.
The system is located in a newly-discovered Pisces-Eridanus stellar stream, which is less than 3% the age of our solar system, stretching across one-third of the sky. These so-called rivers of stars form when the gravity of our galaxy, the Milky Way, rips apart clusters of stars and dwarf galaxies, forming an elongated grouping that continues to disperse into a stream over time.
“This system checks a lot of boxes for astronomers,” said lead researcher Elisabeth Newton in a statement Friday. “It’s only 120 million years old and just 400 light-years away, allowing detailed observations of this young planetary system. And because there are three planets between two and four times Earth’s size, they make especially promising targets for testing theories about how planetary atmospheres evolve.”
This illustration sketches out the main features of TOI 451, a triple-planet system located 400 light-years away in the constellation Eridanus.
NASA’s Goddard Space Flight Center
The Pisces-Eridanus, named for the constellations with the highest number of stars, stretches across 14 constellations total — measuring about 1,300 light-years long.
Astronomers have determined it’s only 120 million years old — eight times younger than previous estimates. Its young age makes it particularly exciting for studying planet and star formation and evolution.
The system’s star, TOI 451, also known as CD-38 1467, is located in the constellation Eridanus, about 400 light-years away. It has 95% of our sun’s mass, but it is 12% smaller, slightly colder and emits 35% less energy.
TOI 451 rotates every 5.1 days — five times faster than the sun.
“The sun of the newly discovered planets is like a teenager compared to our own sun. That means its planets are still changing and evolving,” said Newton.
The Pisces-Eridanus stream spans 1,300 light-years, sprawling across 14 constellations and one-third of the sky. Yellow dots show the locations of known or suspected members, with TOI 451 circled. TESS observations show that the stream is about 120 million years old, comparable to the famous Pleiades cluster in Taurus (upper left).
NASA’s Goddard Space Flight Center
All three planets are very hot and inhospitable to life as we know it, orbiting their star three times closer than Mercury ever gets to our sun. Temperature estimates range from about 2,200 degrees Fahrenheit for the innermost planet to about 840 F for the outermost one.
The closest planet orbits the star roughly every 2 days, while the farthest one circles about every 16 days. They range in size between that of Earth and Neptune.
While there are over 4,000 known planets outside of our solar system, most of them are older and much farther away from Earth than the newly-discovered system. According to the research team, only seven other young systems with multiple transiting planets have ever been found.
The trio gives astronomers the rare opportunity to study a group of growing planets. Researchers plan to continue studying the planets using NASA’s Hubble Space Telescope and its planned successor, the James Webb Space Telescope, to examine how systems like our own solar system evolve.
“By studying these planets in the context of others, we can piece together the picture of how planets form and develop,” Newton said.
