All posts by Tom

Testing the RS-25 Engine

An impressive amount of power developed as the RS-25 engine is hot-fired on 19 October. This engine has a great history of reliability in the NASA shuttle program and will power the new Space Launch System.

In October of 2018 four of these engines will power the first flight test of SLS with Orion which will carry an uncrewed Orion spacecraft beyond the moon, deeper than any human-rated spacecraft has gone, to test the performance of the integrated system.

This test took place at NASA’s Stennis Space Center in Mississippi

Galaxy ESO 553-46 – A Busy Place

As far as galaxies are concerned, size can be deceptive. Some of the largest galaxies in the Universe are dormant, while some dwarf galaxies, such as ESO 553-46 imaged here by the NASA/ESA Hubble Space Telescope, can produce stars at a hair-raising rate. In fact, ESO 553-46 has one of the highest rates of star formation of the 1,000 or so galaxies nearest to the Milky Way. No mean feat for such a diminutive galaxy!
Clusters of young, hot stars are speckling the galaxy, burning with a fierce blue glow. The intense radiation they produce also causes surrounding gas to light up, which is bright red in this image. The small mass and distinctive coloring of galaxies of this type prompted astronomers to classify them, appropriately, as blue compact dwarfs (BCD).
Lacking the clear core and structure that many larger galaxies — such as the Milky Way — have, BCDs such as ESO 553-46 are composed of many large clusters of stars bound together by gravity. Their chemical makeup is interesting to astronomers, since they contain relatively little dust and few elements heavier than helium, which are produced in stars and distributed via supernova explosions. Such conditions are strikingly similar to those that existed in the early Universe, when the first galaxies were beginning to form.

Credit: ESA/Hubble & NASA
Text credit: European Space Agency

Is There a Planet-9?

Despite what you might see on a few internet sites, YouTube in particular, NASA nor anybody else has discovered what they call ‘Planet X’ at least as far as I know.

Could there be another planet out there? Some actual scientists think there just might be.

University of Michigan (Ann Arbor) — A University of Michigan doctoral student has logged two pieces of evidence that may support the existence of a planet that could be part of our solar system, beyond Neptune.

Some astronomers think this alleged planet, called Planet Nine, exists because of the way some objects in space, called “Trans-Neptunian Objects,” or TNOs, behave. These TNOs are rocky objects smaller than Pluto that orbit the sun at a greater average distance than Neptune. But the orbits of the most distant of these TNOs—those whose average distance from the sun is more than 250 times as far as Earth’s distance—seem to point in the same direction. This observation first led astronomers to predict the existence of Planet Nine.

For these TNOs to be aligned in the orbits they currently occupy because of Planet Nine’s influence, astronomers say, they would have been in the solar system for longer than a billion years. However, some astronomers think in that amount of time, some of these objects should have either smashed into another planet, been thrown into the sun, or ricocheted off into space by other planets’ gravitational force.

The U-M research, led by Juliette Becker, a graduate student in the Department of Astronomy, consisted of a large set of computer simulations, which uncovered two findings about these TNOs. First, the researchers established a version of Planet Nine that would most likely cause our solar system to look the way it currently does, by preventing the TNOs from being destroyed or thrown out of the solar system. Second, the simulations predict that there is a process that they call “resonance hopping” by which a TNO jumps between stable orbits. This process can prevent the TNOs from being ejected from the solar system.

In each individual simulation, the researchers tested different versions of Planet Nine to see whether that version of the planet, with its gravitational forces, resulted in the same version of the solar system we see today.

“From that set of simulations, we found out that there are preferred versions of Planet Nine that make the TNO stay stable for longer, so it basically increases the probability that our solar system exists the way it does,” Becker said. “Through these computer simulations, we were able to determine which realization of Planet Nine creates our solar system—the whole caveat here being, if Planet Nine is real.”

The group, which includes U-M physics professors David Gerdes and Fred Adams as well as graduate student Stephanie Hamilton and undergraduate Tali Khain, also examined the resonance of these TNOs with Planet Nine. An orbital resonance occurs when objects in a system periodically exert gravitational forces upon each other that cause the objects to line up in a pattern.

In this case, the researchers found that occasionally, Neptune will bump a TNO out of its orbital resonance, but instead of sending that TNO skittering into the sun, out of the solar system or into another planet, something catches that TNO and confines it into a different resonance.

“The ultimate goal would be to directly see Planet Nine—to take a telescope, point it at the sky, and see reflected light from the sun bouncing off of Planet Nine,” Becker said. “Since we haven’t yet been able to find it, despite many people looking, we’re stuck with these kinds of indirect methods.”

Astronomers also have another newly discovered TNO to include in their indirect methods of detecting Planet Nine. The Dark Energy Survey collaboration, a large group of scientists including several U-M scientists, has discovered another TNO that has a high orbital inclination compared to the plane of the solar system: it is tilted about 54 degrees relative to the solar system’s plane.

In an analysis of this new object, Becker and her team have found that this object experiences resonance hopping as well in the presence of Planet Nine, showing that this phenomenon extends to even more unusual orbits.

This work was supported by National Science Foundation. Becker and Hamilton are also supported by the NSF Graduate Research Fellowship Grant.

Saturn Moon Dione

One of the last images of the Saturn moon Dione from the Cassini spacecraft shows nice detail on the moon surface. Scientists say that the subtle variations in brightness hint at differences in composition, as well as the size and shape of grains in Dione’s surface material, or regolith.

The view was obtained at a distance of approximately 224,000 miles (360,000 kilometers) from Dione which isn’t too much different than our Earth-moon distance. Image scale is 1.4 mile (2.2 kilometers) per pixel

The Cassini spacecraft entered the Saturn atmosphere right on schedule on 15 September 2017.

Image: NASA/JPL-Caltech/Space Science Institute

ESO Kilonovae

What? Wow, this is GREAT! Not just the initial discovery, but what actually happened, two neutron stars colliding and by the way that was “only” 130 million light-years away. Close enough.

Congratulations ESO!!!

ESO — For the first time ever, astronomers have observed both gravitational waves and light (electromagnetic radiation) from the same event, thanks to a global collaborative effort and the quick reactions of both ESO’s facilities and others around the world.

ESO’s fleet of telescopes in Chile have detected the first visible counterpart to a gravitational wave source. These historic observations suggest that this unique object is the result of the merger of two neutron stars. The cataclysmic aftermaths of this kind of merger — long-predicted events called kilonovae — disperse heavy elements such as gold and platinum throughout the Universe. This discovery, published in several papers in the journal Nature and elsewhere, also provides the strongest evidence yet that short-duration gamma-ray bursts are caused by mergers of neutron stars.

Read the whole story – except what they were actually doing at the time – be fun to hear about the first few moments of realization of what was going on.

Planetary Formation Studied

Very interesting take on how dust can turn into a planet from the University of Exeter.

The University press release:

A new study by an international team of scientists, led by Stefan Kraus from the University of Exeter, has given a fascinating new insight into one of the most respected theories of how planets are formed.

Young stars start out with a massive disk of gas and dust that over time, astronomers think, either diffuses away or coalesces into planets and asteroids.

However, scientists are still searching for a complete understanding of how these early formations come together to form asteroid-sized objects. One reason has been that drag in the disk produced by surrounding gas makes the grains move inward toward the star – which can in turn deplete the disk rapidly in a process known as “radial drift.”
In the new research, the team use high powered telescopes to target the star V1247 Orionis -, a young, hot star surrounded by a dynamic ring of gas and dust.

The team produced a detailed image of the star and its surrounding dust disc, shown in two parts: a clearly defined central ring of matter and a more delicate crescent structure located further out.
The region between the ring and crescent, visible as a dark strip, is thought to be caused by a young planet carving its way through the disc. As the planet moves around in its orbit, its motion creates areas of high pressure on either side of its path, similar to how a ship creates bow waves as it cuts through water.

These areas of high pressure could become protective barriers around sites of planet formation; dust particles are trapped within them for millions of years, allowing them the time and space to clump together and grow.
Professor Kraus said: “The exquisite resolution of ALMA allowed us to study the intricate structure of such a dust-trapping vortex for the first time. The crescent in the image constitutes a dust trap that formed at the outer edge of the dark strip.

“It also reveals regions of excess dust within the ring, possibly indicating a second dust trap that formed inside of the putative planet’s orbit. This confirms earlier computer simulations that predicted that dust traps should form both at the outer edge and inner edge of disc gaps.

“Dust trapping is one potential solution to a major stumbling block in our theories of how planets form, which predicts that particles should drift into the central star and be destroyed before they have time to grow to planetesimal sizes.”

Dust-trapping vortices and a potentially planet-triggered spiral wake in the pre-transitional disk of V1247 Orionis is published in Astrophysical Journal Letters.

Credit: University of Exeter

The Last Moments of Cassini

The Cassini team released a description of Cassini’s last moments. The spacecraft was a fighter to the very end especially when one considers that it was traveling around 4.5 times faster than the ISS is around Earth.

Here’s a excerpt from the NASA description:

Data show that as Cassini began its final approach, in the hour before atmospheric entry it was subtly rocking back and forth by fractions of a degree, gently pulsing its thrusters every few minutes to keep its antenna pointed at Earth. The only perturbing force at that time was a slight tug from Saturn’s gravity that tried to rotate the spacecraft.

“To keep the antenna pointed at Earth, we used what’s called ‘bang-bang control,'” said Julie Webster, Cassini’s spacecraft operations chief at NASA’s Jet Propulsion Laboratory, Pasadena, California. “We give the spacecraft a narrow range over which it can rotate, and when it bangs up against that limit in one direction, it fires a thruster to tip back the other way.” (This range was indeed small: just two milliradians, which equals 0.1 degree. The reconstructed data show Cassini was subtly correcting its orientation in this way until about three minutes before loss of signal.)

At this point, about 1,200 miles (1,900 kilometers) above the cloud tops, the spacecraft began to encounter Saturn’s atmosphere. Cassini approached Saturn with its 36-foot-long (11-meter) magnetometer boom pointing out from the spacecraft’s side. The tenuous gas began to push against the boom like a lever, forcing it to rotate slightly toward the aft (or backward) direction. In response, the thrusters fired corrective gas jets to stop the boom from rotating any farther. Over the next couple of minutes, as engineers had predicted, the thrusters began firing longer, more frequent pulses. The battle with Saturn had begun.

With its thrusters firing almost continuously, the spacecraft held its own for 91 seconds against Saturn’s atmosphere — the thrusters reaching 100 percent of their capacity during the last 20 seconds or so before the signal was lost. The final eight seconds of data show that Cassini started to slowly tip over backward. As this happened, the antenna’s narrowly focused radio signal began to point away from Earth, and 83 minutes later (the travel time for a signal from Saturn), Cassini’s voice disappeared from monitors in JPL mission control. First, the actual telemetry data disappeared, leaving only a radio carrier signal. Then, 24 seconds after the loss of telemetry, silence.

These data explain why those watching the signal — appearing as a tall green spike on a squiggly plot of Cassini’s radio frequency — in mission control and live on NASA TV — saw what appeared to be a short reprieve, almost as though the spacecraft was making a brief comeback. The spike of the signal first began to diminish over a few seconds, but then rose briefly again before disappearing with finality.

Credit: NASA/JPL-Caltech

Progress 68 Launch – Replay

The Progress 68 launch from the Baikonur Cosmodrome tried another launch this morning and it went beautifully.

I really like the launch set-up at Baikonur.

Here we go! Great launch, replay to come.

Update: All is well and the Progress is ready to meet up with the ISS in two days.

ESA Sentinel 5p Satellite Launch- REPLAY

From the Plesetsk Cosmodrome in Russia, This is a northern Cosmodrome so it is only used for certain types of orbits due to the high latitude. For those in North America, this would be about the latitude of Bethel Alaska.

NOTE: Here’s the replay. Beautiful foliage, reminds me of here, and a very “different” kind of a feel to the launch, perhaps it was the fog or seeing the “rokot” lift off in the midst of the trees.

So far so good with the flight and deployment.