Scott Alan Johnston, Author at Universe Today

June 17, 2023June 17, 2023 by Scott Alan Johnston

We Could See the Glint off Giant Cities on Alien Worlds

How large would an extraterrestrial city have to be for current telescopes to see it? Would it need to be a planet-sized metropolis like Star Wars’ Coruscant? Or could we see an alien equivalent of Earth’s own largest urban areas, like New York City or Tokyo?

A recent preprint by Bhavesh Jaiswal of the Indian Institute of Science suggests that, in fact, we could see cities a mere fraction of that size, using a feature of light known as specular reflection.

June 12, 2023June 12, 2023 by Scott Alan Johnston

These are the Fastest Stars in the Galaxy

Artist concept showing a hypervelocity star escaping our galaxy. Credit: NASA, ESA, and G. Bacon (STScI)

Until recently, there were only ten known stars on trajectories that will allow them to escape the Milky Way Galaxy, thrown astray by powerful supernova explosions. A new study using data from ESA’s Gaia survey this June has revealed an additional six runaways, two of which break the record for the fastest radial velocity of any runaway star ever seen: 1694 km/s and 2285 km/s.

May 20, 2023May 20, 2023 by Scott Alan Johnston

Artemis V is Going to the Moon With Blue Origin

NASA has announced a second lunar lander provider for its Artemis program, choosing Blue Origin’s National Team to deliver astronauts to the Moon’s south pole as early as 2029. Blue Origin’s lander will be part of the Artemis V mission. They join SpaceX, whose Starship is already slated to ferry astronauts to the lunar surface for Artemis III and IV.

May 13, 2023May 13, 2023 by Scott Alan Johnston

Perseverance Finds an Ancient, Fast Flowing River

In a first for Martian water science, NASA’s Perseverance rover has discovered geological evidence of a large, fast-moving river in Mars’ ancient past. The high-energy river once emptied into Jezero crater, which the rover has been exploring since early 2021, and is a totally different water system than anything seen previously on the red planet.

May 1, 2023May 1, 2023 by Scott Alan Johnston

China Finally Tells us What's Going on With its Mars Rover

A wireless camera took this 'group photo' of China's Tianwen-1 lander and rover on Mars' surface. Credit: Chinese Space Agency

The Zhurong Rover has sat unmoving and unresponsive on Mars since May 20^th, 2022, when one of the planet’s infamous dust storms forced the science team to switch the rover to hibernation mode. It was expected to wake in late December, but has yet to show any signs of activity. Last week, the Rover’s chief designer, Zhang Rongqiao, offered an update on the rover’s status.

April 23, 2023April 23, 2023 by Scott Alan Johnston

The Milky Way has Trapped the Large Magellanic Cloud With its Gravity. What Comes Next?

Our galaxy’s largest nearby companion is the Large Magellanic Cloud (LMC), a dwarf galaxy visible to the naked eye in the Southern Hemisphere. In recent years, new theoretical research and better observational capabilities have taught astronomers a great deal about our (not-so-little) neighbour. It’s becoming increasingly clear that the LMC is helping shape the Milky Way’s evolution.

April 7, 2023April 7, 2023 by Scott Alan Johnston

Hubble Sees Two Quasars Side by Side in the Early Universe

When it comes to the brightest, most powerful objects in the Universe, not much can beat a Quasar. A Gamma Ray Burst from a supernova might be more energetic, but doesn’t last very long. Quasars, by comparison, can churn out 1000 times the radiation of the Milky Way, and keep doing it for hundreds of millions of years.

They get all this energy from the supermassive black holes that live at the center of galaxies. As material falls towards the black hole, an accretion disk forms around it: a swirling cloud of energetic material which heats up through friction and releases electromagnetic radiation. The resulting Quasar can be so bright it drowns out the light from the rest of its galaxy from our perspective.

On April 5^th, researchers announced the discovery of a rare double quasar in the early Universe. The two quasars are gravitationally bound, spiraling in towards each other. Their host galaxies are in the process of merging, and the supermassive black holes generating the quasars will also eventually collide and merge.

April 4, 2023April 4, 2023 by Scott Alan Johnston

A Stellar Explosion Mimicked the End of the Death Star

In 1997, George Lucas released the special edition remaster of his Star Wars trilogy, making changes to the special effects that both delighted and divided fans worldwide (did Han shoot first?). Among the myriad additions was a visually spectacular ring-shaped shockwave emanating from the exploding Death Star, and Alderaan too. Star Trek fans will delightedly point out that this particular special effect had previously been used in the 1991 film Star Trek VI: The Undiscovered Country, in which the Klingon moon Praxis explodes, giving the effect its name: the Praxis ring. Hollywood lore suggests Lucas was so impressed with the effect in that film that he added it to Star Wars too.

Praxis rings look cool on the silver screen, but we all know explosions in space are supposed to be spherical. With no preference for up, down, left, or right, the material blown off an exploding star should push outward in all directions.

Except when it doesn’t. A paper published at the end of March described the flattest explosion ever observed, with a disc of material ejecting out from the core along one plane, just like the Praxis effect.

March 26, 2023March 26, 2023 by Scott Alan Johnston

Asteroid Ryugu Contains Niacin (aka Vitamin B3)

In December 2020, JAXA’s Hayabusa2 spacecraft delivered a pristine sample of otherworldly dust and rock from asteroid Ryugu to Earth. Scientists have since had the opportunity to study the sample, and announced last week that the asteroid contains organic molecules important for life. In particular, they discovered Niacin, otherwise known as vitamin B3, and Uracil, one of the four core components of ribonucleic acid (RNA).

March 15, 2023March 15, 2023 by Scott Alan Johnston

Didymos is Spinning So Quickly That Rocks are Detaching at its Equator and Going Into Orbit

Asteroid Didymos is spitting rocks out into space.

Last fall, when NASA’s DART mission impacted Didymos’ moon Dimorphos in a dramatic (and successful) attempt to change the object’s orbit, DART got a quick look at the Didymos system before the probe was purposefully smashed to pieces.

Alongside demonstrating the capability to prevent future asteroid strikes on Earth, DART also gathered new information about the dynamics of the pair of asteroids. The data collected suggests that Didymos is actively throwing material out into space, and there are likely millions of other small asteroids doing the same across the Solar System, all the time.