October 17, 2018

Good Morning,

I find outer space as interesting as I find it unsettlingly scary. It must be amazing to look through some of the most powerful telescopes and witness indescribable beauty, but there must be times when it's not quite as spectacular as you were expecting. Which brings me to what astronomers at California Institute of Technology happened to witness...

Learn about this and more interesting stories from the scientific community in today's issue.

Until Next Time,
Erin

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*-- Stellar death reveals compact neutron star binary --*

Astronomers were surprised when the collapse of a massive star yielded a rather puny supernova.

An investigation of the phenomena suggests a companion star robbed the collapsing star of much of its stellar material, limiting the magnitude of the explosion.

"We saw this massive star's core collapse, but we saw remarkably little mass ejected," Kishalay De, grad student at the California Institute of Technology, said in a news release. "We call this an ultra-stripped envelope supernova and it has long been predicted that they exist. This is the first time we have convincingly seen core collapse of a massive star that is so devoid of matter."

When massive stars run out of fuel and collapse in on themselves, the material rebounds outward in dramatic fashion. The violent explosion sends the outer stellar layers into interstellar space, leaving behind a small but extremely dense core, a neutron star.

Because the star exploded, scientists determined the stellar core must have been large enough to collapse. But the diminutive explosion suggested the star was missing a significant amount of matter.

An intimate companion, close enough to siphon gas from its neighbor, was the best explanation. Not only had scientists witnessed a unusual stellar death, they had also observed the birth of a compact neutron star binary system -- a first.

The observations -- detailed this week in the journal Science -- were made possible by a unique astronomical survey, the intermediate Palomar Transient Factory, a nightly scan conducted at the Palomar Observatory. The survey is designed to identify short-lived cosmic phenomena.

"You need fast transient surveys and a well-coordinated network of astronomers worldwide to really capture the early phase of a supernova," said De. "Without data in its infancy, we could not have concluded that the explosion must have originated in the collapsing core of a massive star with an envelope about 500 times the radius of the sun."

Scientists continue to monitor the compact neutron star binary system using a collection of observatories called the GROWTH network. The companions are so close that they will eventually merge. Neutron star mergers can produce gravitational waves -- as was observed in 2017.

Astronomers can learn about the nature of extreme cosmic events by studying the patterns of gravitational waves.

*-- Chandra X-ray Observatory goes into safe mode --*

It's been a bad couple weeks in space.

A week ago, technical difficulties forced engineers to put the Hubble Space Telescope's science mission on hold. Now, the Chandra X-ray Observatory is in safe mode, too.

In a statement released on Friday, NASA confirmed Chandra, one of the most powerful telescopes in space, transitioned to safe mode earlier this week.

During safe mode, the observatory's mirrors are pointed away from the sun and its solar panels are turned directly toward the sun. The satellite's most critical hardware is transferred to backup drives.

"Analysis of available data indicates the transition to safe mode was normal behavior for such an event," according to NASA. "All systems functioned as expected and the scientific instruments are safe."

Engineers are still working to determine why Chandra went into safe mode.

As Chandra's Twitter account reminded readers, the powerful X-ray telescope is getting up its in age: "Chandra is 19 years old, which is well beyond the original design lifetime of 5 years."

In a separate release, NASA confirmed Hubble is still in safe mode. Last week, NASA and European Space Agency engineers suspended the telescopes' scientific activities after one of its gyroscopes failed.

Scientists turned on a replacement gyro, but the backup didn't perform as hoped.

"This past week, tests were conducted to assess the condition of that backup gyro. The tests showed that the gyro is properly tracking Hubble's movement, but the rates reported are consistently higher than the true rates," according to NASA.

Because the gyro is reading rates of changes at a greater magnitude, it can't be used to monitor smaller changes. Normally, when fixed on an observation target, Hubble's gyros operate on low-mode.

"The extremely high rates currently being reported exceed the upper limit of the gyro in this low mode, preventing the gyro from reporting the spacecraft's small movements," NASA reported.

If followup troubleshooting efforts fail, Hubble will be forced to shut down all but a single gyroscope. Previous tests showed Hubble can conduct observation using a single gyro.

Hubble and Chandra aren't the only spacecraft in trouble. Earlier this week, NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin were forced to abort their mission to the space station just moments after launch, ejecting their Soyuz capsule from the rocket and executing an emergency "ballistic descent."

And as NASA reported this week, the Mars rover Curiosity is still silent. Engineers haven't communicated with the rover for four months.


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