Astronomy

China has selected 10 new astronauts for training as part of its goal to put a crew on the moon by 2030, the country's human spaceflight agency announced last week.

A nuclear explosion in space would cause stunning auroras—and wreak havoc on satellites and space stations.

SpaceX launched 20 of its Starlink satellites from California on Tuesday night (June 18), ending a 10-day spaceflight drought for the company.

The Hubble Space Telescope has experienced ongoing problems with one of its three remaining gyroscopes, so NASA has decided to shift the telescope into single gyro mode. While the venerable space telescope has now returned to daily science operations, single gyro mode means Hubble will only use one gyro to maintain a lock on its target. This will slow its slew time and decrease some of its scientific output. But this plan increases the overall lifetime of the 34-year-old telescope, keeping one gyro in reserve. NASA is also troubleshooting the malfunctioning gyro, hoping to return it online.

Last week, NASA said that the telescope and its instruments are stable and functioning normally.

Gyroscopes help the telescope orient itself in space, keeping it stable to precisely point at astronomical targets in the distant Universe. Hubble went into safe mode back in November 2023, and then again in April and May 2024 due to the ongoing issue, where the one gyro had been increasingly returning faulty readings.

The end of a Hubble gyro reveals the hair-thin wires known as flex leads. They carry data and electricity inside the gyro. Credit: NASA

Going in to safe mode suspends science operations, and in the meantime, engineers tried to troubleshoot to figure out why the gyro experiencing the fault-producing issues and doing work-arounds to get the telescope up and running again. The most recent last safe-mode event in May led the Hubble team to transition from a three-gyro operating mode to observing with only one gyro. This enables more consistent science observations while keeping the other operational gyro available for future use.

Launched in 1990, Hubble has more than doubled its expected design lifetime, providing stunning images and scientific discoveries that have changed our understanding of the Universe and re-written astronomy textbooks.  

During its 34-year history, Hubble has had eight out of 22 gyros fail due to a corroded flex lead, which are thin (less than the width of a human hair) metal wires, that carry power in, and data out, of the gyro.  The flex leads pass through a thick fluid inside the gyro and over time, the flex leads begin to corrode and can physically bend or break.

With his feet firmly anchored on the shuttle’s robotic arm, astronaut Mike Good maneuvers to retrieve the tool caddy required to repair the Space Telescope Imaging Spectrograph during the final Hubble servicing mission in May 2009. Periodic upgrades have kept the telescope equipped with state-of-the-art instruments, which have given astronomers increasingly better views of the cosmos. Credits: NASA

Thankfully, for the first 18 years of Hubble’s life in space, the telescope had the advantage of being able to be serviced and upgraded by space shuttle astronauts. For example, in 1999, four out of six gyros had failed, with the last one failing about a month before a servicing mission was scheduled to replace them (and do other upgrades to the telescope). This meant Hubble sat in safe mode waiting for the space shuttle and astronauts to arrive.

When the final planned Hubble servicing mission was (temporarily) canceled following the space shuttle Columbia disaster, engineers developed and inaugurated a two-gyro mode to prolong Hubble’s life. The mission was reinstated after outcry from scientists and the public, and so NASA figured out a way to mitigate the risks of flying the space shuttle. Servicing Mission 4 replaced all six gyros one last time in 2009, but it has been running on three since 2018. The three gyros all quit working due to flex lead failures. The retirement of the space shuttle means Hubble has now been operating for 15 years without servicing.

The Hubble Rate Gyro Assembly contains a gyroscope and all of its associated electronics. The gyroscopes are part of Hubble’s pointing system. They provide a frame of reference for Hubble to determine where it is pointing and how that pointing changes as the telescope moves across the sky. They report any small movements of the spacecraft to Hubble’s pointing and Control System. The computer then commands the spinning reaction wheels to keep the spacecraft stable or moving at the desired rate. Credit: NASA

However, during the time it was thought no future servicing mission would happen, the team also devised a one-gyro mode, which will further extend Hubble’s life.

“We knew gyros would be a limiting factor so we started to working on a reduced gyro mode to extend their life,” the director of the Space Telescope Science Institute Ken Sembach told me back in 2015 for my book, “Incredible Stories From Space.” “As it turned out, we did need that reduced gyro mode, and now they aren’t [as big of a] limiting factor for Hubble because we now know how to use the gyro resources in a new way. That added a longer life to the mission we didn’t think we would have.”

While engineers say the difference between two-gyro mode and one gyro-mode is negligible, one-gyro mode provides the option to have one of the remaining gyros placed in reserve.

NASA says that although one-gyro mode is an excellent way to keep Hubble science operations going, it does have limitations, which include a small decrease in efficiency (roughly 12 percent) due to the added time required to slew and lock the telescope onto a science target. One gyro mode also means it takes additional time for the telescope’s fine guidance sensors to search for the guide stars. Additionally, in one-gyro mode Hubble has some restrictions on the science it can do. For example, Hubble cannot track moving objects that are closer to Earth than the orbit of Mars. Without the full complement of gyros, the motion of these objects are too fast for the telescope to track. Additionally, the reduced area of sky that Hubble can point to at any given time also reduces its flexibility to see transient events or targets of opportunity like an exploding star or an impact on Jupiter. NASA says that when combined, “these factors may yield a decrease in productivity of roughly 20 to 25 percent from the typical observing program conducted in the past using all three gyros.”

Read more about the “new normal” for Hubble’s one-gyro mode at this NASA webpage.

The post Hubble's Back, but Only Using One Gyro appeared first on Universe Today.

Slovenia signed the Accession Agreement to the ESA Convention on 18 June 2024. Upon ratification, Slovenia will become the 23rd ESA Member State.

The appearance this week of the three bright Summer Triangle stars — Vega, Deneb and Altair — marks the beginning of summer in the Northern Hemisphere. Here's how to spot them.

Humans may have shaped the development of aromatic herbs like lavender and mint, but did herbs also shape our own evolution?

Humans may have shaped the development of aromatic herbs like lavender and mint, but did herbs also shape our own evolution?

When June 2024's Strawberry Moon is almost full, it will occult the bright star Antares.

Earth’s protective atmosphere has sheltered life for billions of years, creating a haven where evolution produced complex lifeforms like us. The ozone layer plays a critical role in shielding the biosphere from deadly UV radiation. It blocks 99% of the Sun’s powerful UV output. Earth’s magnetosphere also shelters us.

But the Sun is relatively tame. How effective are the ozone and the magnetosphere at protecting us from powerful supernova explosions?

Every million years—a small fraction of Earth’s 4.5 billion-year lifetime—a massive star explodes within 100 parsecs (326 light-years) of Earth. We know this because our Solar System sits inside a massive bubble in space called the Local Bubble. It’s a cavernous region of space where hydrogen density is much lower than outside the bubble. A series of supernovae explosions in the previous 10 to 20 million years carved out the bubble.

Supernovae are dangerous, and the closer a planet is to one, the more deadly its effects. Scientists have speculated on the effects that supernova explosions have had on Earth, wondering if it triggered mass extinctions or at least partial extinctions. A supernova’s gamma-ray burst and cosmic rays can deplete Earth’s ozone and allow ionizing UV radiation to reach the planet’s surface. The effects can also create more aerosol particles in the atmosphere, increasing cloud coverage and causing global cooling.

A new research article in Nature Communications Earth and Environment examines supernova explosions and their effect on Earth. It is titled “Earth’s Atmosphere Protects the Biosphere from Nearby Supernovae.” The lead author is Theodoros Christoudias from the Climate and Atmosphere Research Center, Cyprus Institute, Nicosia, Cyprus.

The Local Bubble isn’t the only evidence of nearby core-collapse supernovae (SNe) in the last few million years. Ocean sediments also contain 60Fe, a radioactive isotope of iron with a half-life of 2.6 million years. SNe expel 60Fe into space when they explode, indicating that a nearby supernova exploded about 2 million years ago. There’s also 60Fe in sediments that indicate another SN explosion about 8 million years ago.

This graphic from the research article shows the potential atmospheric and climate impacts of a nearby supernova. Gamma rays can deplete the ozone, allowing more UV radiation to reach Earth’s surface. Some UV radiation is ionizing, meaning it can damage DNA. Cosmic rays can also create more condensation nuclei, meaning more clouds and potential global cooling, Image Credit: Christoudias et al. 2024

Researchers have correlated an SN explosion with the Late Devonian extinction about 370 million years ago. In one paper, researchers found plant spores burned by UV light, an indication that something powerful depleted Earth’s ozone layer. In fact, Earth’s biodiversity declined for about 300,000 years prior to the Late Devonian extinction, suggesting that multiple SNe could’ve played a role.

Earth’s ozone layer is in constant flux. As UV energy reaches it, it breaks ozone molecules (O3) apart. That dissipates the UV energy, and the oxygen atoms combine into O3 again. The cycle repeats. That’s a simplified version of the atmospheric chemistry involved, but it serves to illustrate the cycle. A nearby supernova could overwhelm the cycle, depleting the ozone column density and allowing more deadly UV to reach Earth’s surface.

But in the new paper, Christoudias and his fellow authors suggest that Earth’s ozone layer is much more resilient than thought and provides ample protection against SNe within 100 parsecs. While previous researchers have modelled Earth’s atmosphere and its response to a nearby SN, the authors say that they’ve improved on that work.

They modelled Earth’s atmosphere with an Earth Systems Model with Atmospheric Chemistry (EMAC) model to study the impact of nearby SNe explosions on Earth’s atmosphere. Using EMAC, the authors say they’ve modelled “the complex atmospheric circulation dynamics, chemistry, and process feedbacks” of Earth’s atmosphere. These are needed to “simulate stratospheric ozone loss in response to elevated ionization, leading to ion-induced nucleation and particle growth to CCN” (cloud condensation nuclei.)

“We assume a representative nearby SN with GCR (galactic cosmic ray) ionization rates in the atmosphere that are 100 times present levels,” they write. That correlates with a supernova explosion about 100 parsecs or 326 light-years away.

These panels from the research letter show the ozone column percentage decrease from a 100-fold increase in GCR intensity over nominal. The left vertical axis represents Earth’s latitude, and the x-axis shows the time of year. Ozone loss is more pronounced over the poles due to the effect of Earth’s magnetosphere, where it’s weaker. a is present-day Earth, while b represents an ancient Earth with only 2% oxygen during the pre-Cambrian. Image Credit: Christoudias et al. 2024

“The maximum ozone depletion over the poles is less than the present-day anthropogenic ozone hole over Antarctica, which amounts to an ozone column loss of 60–70%,” the authors explain. “On the other hand, there is an increase of ozone in the troposphere, but it is well within the levels resulting from recent anthropogenic pollution.”

But let’s cut to the chase. We want to know if Earth’s biosphere is safe or not.

The maximum mean stratospheric ozone depletion from 100 times more ionizing radiation than normal, representative of a nearby SN, is about 10% globally. That’s about the same decrease as our anthropogenic pollution causes. It wouldn’t affect the biosphere very much.

“Although significant, it is unlikely that such ozone changes would have a major impact on the biosphere, especially because most of the ozone loss is found to occur at high latitudes,” the authors explain.

But that’s for modern Earth. During the pre-Cambrian, before life exploded in a multiplication of forms, the atmosphere had only about 2% oxygen. How would an SN affect that? “We simulated a 2% oxygen atmosphere since this would likely represent conditions where the emerging biosphere on land would still be particularly sensitive to ozone depletion,” the authors write.

“Ozone loss is about 10–25% at mid-latitudes and an order of magnitude lower in the tropics,” the authors write. At minimum ozone levels at the poles, ionizing radiation from an SN could actually end up increasing the ozone column. “We conclude that these changes of atmospheric ozone are unlikely to have had a major impact on the emerging biosphere on land during the Cambrian,” they conclude.

What about global cooling?

Global cooling would increase, but not to a dangerous extent. Over the Pacific and Southern oceans, CCN could increase by up to 100%, which sounds like a lot. “These changes, while climatically relevant, are comparable to the contrast between the pristine pre-industrial atmosphere and the polluted present-day atmosphere.” They’re saying that it would cool the atmosphere by about the same amount as we’re heating it now.

These two panels from the research help illustrate the global cooling effect from a nearby SN exposing Earth to 100 times more ionizing radiation. b shows the fractional change in CCN relative to the present day. d shows the fractional change in outgoing solar radiation relative to the present day due to increased cloud albedo. Image Credit: Christoudias et al. 2024

The researchers point out that their study concerns the entire biosphere, not individuals. “Our study does not consider the direct health risks to humans and animals resulting from exposure to elevated ionizing radiation,” they write. Depending on individual circumstances, individuals could be exposed to dangerous levels of radiation over time. But overall, the biosphere would hum along despite a 100-fold increase in UV radiation. Our atmosphere and magnetosphere can handle it.

“Overall, we find that nearby SNe are unlikely to have caused mass extinctions on Earth,” the authors write. “We conclude that our planet’s atmosphere and geomagnetic field effectively shield the biosphere from the effects of nearby SNe, which has allowed life to evolve on land over the last hundreds of million years.”

This study shows that Earth’s biosphere will not suffer greatly as long as supernova explosions keep their distance.

The post Earth’s Atmosphere is Our Best Defence Against Nearby Supernovae appeared first on Universe Today.

NOAA's GOES-R series constellation will be complete in space with the launch of its GOES-U satellite at the end of June. This will mark the first time a NOAA satellite will be transported to space using a SpaceX Falcon Heavy rocket.

NASA has rescheduled last week's EVA, which was called off only an hour before the astronauts were set to exit the station.

Boeing's Starliner will come back to Earth with its two astronauts no earlier than June 26. The four-day extension will allow for more thruster testing at the ISS.

SpaceX is poised to launch the SES Astra 1P telecom satellite after standing down due to elevated winds at the launch site.

This image of Galveston was taken on Nov. 23, 2022, from the International Space Station as it orbited 224 miles above Earth. While President Abraham Lincoln issued the Emancipation Proclamation in 1863, word that enslaved people were free did not reach Galveston until well into 1865. When Union troops arrived that year to share the news, spontaneous celebrations broke out in African American churches, homes, and other gathering places. As years passed, the picnics, barbecues, parades, and other celebrations that sprang up to commemorate June 19th became more formalized as freed men and women purchased land, or “emancipation grounds,” to hold annual Juneteenth celebrations.

The chemical composition of Pluto and Triton suggests they originated in the same region of the outer solar system before the latter was pulled into Neptune’s orbit

The chemical composition of Pluto and Triton suggests they originated in the same region of the outer solar system before the latter was pulled into Neptune’s orbit

Image: Metallic Mars

According to Lego, the Milky Way Galaxy is made up of love hearts, frogs, flowers and coffee mugs — and it's absolutely fabulous.

Why does this mysterious woman keep popping up in the Doctor's timeline? And what's her connection to the season's Big Bad?