The vast majority of mass in our universe is invisible. And for quite some time, physicists have been trying to understand what this elusive mass is. If it is made up of particles, the hope is that the Large Hadron Collider can produce a dark matter particle, or the space telescope will see an eloquent gamma ray signature of a dark matter collision. 

So far, there is nothing and this problem makes theoretical physicists ponder new ideas.

In 2017, renowned theoretical physicist Lisa Randall took a peek into one of the most incredible possibilities of dark matter. Hypothetical, of course. Rather than treating dark matter as a particular type of particle, she assumed that dark matter could be made up of a whole family of particles that make up dark stars, dark galaxies, dark planets, and possibly dark life. The chemistry of the dark universe could be as rich and varied as our own “regular chemistry.” But it’s not that simple.

Dark matter problem

Our Universe is an amazing, albeit incomprehensible place.

Over the past few decades, we have come to realize that 84.5% of the matter in the Universe cannot be seen. Given its rather awkward nickname “dark matter”, this substance is in a state in which it does not interact with “normal” matter. Like dark energy, these things are “dark” because we don’t understand them.

If there is a piece of dark matter on my desk now, I will never know about it. A piece of dark matter in general, as such, cannot lie on my desk. It will fall through the table, and the floor, and the earth’s crust, rush into the gravity well at the core of our planet. Or it will disappear into space in an incomprehensible way. Dark matter interacts so weakly with anything that this piece will simply fall through ordinary matter, as if it does not exist.

On a small scale, the gravitational manifestation of dark matter is negligible, but at cosmological distances, the presence of dark matter is definitely felt – it can be observed indirectly by its gravitational effect on galaxy clusters and its effect on the rotation of galaxies. We know that it exists, we just don’t see it.

We don’t know what it is, we can only guess

Ordinary matter – aka baryonic matter – interacts through electromagnetic, gravitational, strong and weak forces. These forces transfer energy and give structure to all matter. Dark matter, on the other hand, is usually viewed as an amorphous cloud of “matter” that cannot interact through electromagnetic, weak or strong forces. Therefore, dark matter is assumed to be “non-baryonic”. Non-baryonic matter can reveal its presence only gravitationally.

The leading candidate in the search for dark matter is WIMP, a weakly interacting massive particle. As the WIMP name suggests, this hypothetical particle does not interact with normal matter – so it is not baryonic.

Established cosmological models predict that dark matter – be it in the form of WIMPs or “axions”, say – endows our Universe with structure and is usually simplistically called the “glue” that holds our Universe as a whole.

Observing the rotation of galaxies, astronomer Vera Rubin noticed that most of the matter in galaxies is not observable. Only a small percentage are visible – stars, gas and dust; the rest hides in a huge but invisible halo of dark matter. It’s like our visible galaxy of ordinary matter is just a hood on a huge wheel of dark matter that extends far beyond what we can see.

In a recently published paper (2013), Randall and her colleagues presented a more complex form of dark matter. According to them, the dark matter halo of our galaxy does not consist of only one type of amorphous mass of non-baryonic matter.

“It seems very strange to assume that all dark matter is composed of just one type of particle,” writes Randall. “The unbiased scientist should not allow dark matter to be as diverse as our normal matter.”

A rich “shadow universe”?

Just as our visible universe is governed by the Standard Model of physics – a well-proven family of particles (including the infamous Higgs boson) and forces, could a rich and varied model of dark matter particles and forces function in a dark galactic halo?

This research follows the logic of assuming a rich variety of unknown physics in the dark sector of the universe – let’s call it the “shadow universe” – that runs parallel to our own and has all the complexities that our visible universe has to offer.

Astrophysicists previously suggested that “dark stars” – stars composed of dark matter – may exist in our ancient universe to this day. If so, Randall argues, perhaps “dark planets” could form. And if there is a family of dark matter particles controlled by forces deployed in the dark sector, could this lead to complex chemistry? And to life?

However, if there is “dark” or “shadow” life parallel to our universe, you can forget that we will be able to detect it.

Shadow life will remain in the shadows

It seems tempting to use this hypothesis to explain all the day-to-day mysteries, or even paranormal claims, that science cannot dispute or support. What if “ghosts” or inexplicable “lights in the sky” are the antics of dark creatures living in the back of everything?

While this logic would be fine for a TV show or movie, these dark creatures would live in a shadowy universe that is completely incompatible with ordinary matter. Their particles and forces would have no effect in our universe. You could read these lines sitting on a tree stump in a dark forest, and you would never know about it.

But since we coexist with this shadow universe in the same space-time – without unnecessary dimensions or multiverse – only one signal can be transmitted.

Gravitational waves were only discovered in 2016, and the first detection of these ripples in space-time was caused by the collision of black holes. It seems quite possible that gravitational waves can be detected in the dark sector, but only the most powerful cosmic events in the dark sector can be detected at our end of the wire.

All in all, we’ll almost certainly never prove the existence of cute dark matter creatures, but Randall makes a point. When we contemplate the source of dark matter, we must look beyond our prejudices; the dark sector can be a complex family of dark matter particles and forces that are beyond what we can imagine.

The TESS Space Telescope has discovered a planet on which oceans may exist. In addition, the exoplanet revolves around a quiet star, and this compares favorably with other candidates for the title of the cradle of extraterrestrial life. This is the first, but certainly not the last potentially inhabited world discovered by the TESS Observatory.

The space telescope was launched in 2018. Its task is to search for exoplanets, including those similar to Earth.

TESS has discovered 17 Earth-like planets orbiting 11 stars so far, according to a press release for the new study. All these luminaries are red dwarfs, which are smaller and colder than the Sun.

The TESS team divided almost the entire sky into sectors, each of which is observed for 27 days. However, these areas partially overlap, so some luminaries remain in the field of view of the device for much longer.

The TOI-700 star (aka TIC 150428135) is one of those “lucky ones”. Thanks to this, astronomers have discovered as many as three exoplanets about the size of the Earth.

The first of them (TOI-700b) has a radius almost equal to that of the Earth and revolves around its sun in 10 Earth days. The next planet, TOI-700c, is much larger than its neighbor (2.7 times the Earth’s radius). It makes a complete revolution in 16 days.

However, the most interesting of all is the third exoplanet from the planet TOI-700d. Its radius is 1.1 terrestrial, and its orbital period is 37 terrestrial days. It is this orbit around the cool local sun that makes the TOI-700d “right to life.” 

According to scientists, the planet receives 86% of the heat that goes to the Earth. This means that the temperature on this celestial body allows for the existence of liquid water and, therefore, the biosphere. According to experts, the exoplanet is in the habitable zone.

Three scientific articles published in the Astronomical Journal are devoted to the newly discovered world.

The first describes the discovery of this planet using the TESS telescope.

The second publication is devoted to the observation of an exoplanet using the Spitzer space infrared observatory. The telescope received this data in October 2019 and January 2020, shortly before the termination of its mission.

Finally, the authors of the third research paper simulated the possible climate of TOI-700d.

The researchers examined two dozen scenarios that differ from each other in the composition of the planet’s atmosphere, the amount of water on it, and other characteristics. Their conclusion is optimistic: a climate suitable for life is obtained in a fairly wide range of conditions.

It is important that TOI-700, unlike most other red dwarfs, is a calm star, not prone to catastrophic flares. That is, TOI-700d has every chance of preserving the atmosphere and hydrosphere for billions of years.

Of course, not without a fly in the ointment. TOI-700 is more than a hundred light years from Earth. It’s too far away to directly study the atmosphere of a small planet like TOI-700d, even with the future James Webb telescope .

However, the capabilities of astronomical instruments are growing rapidly. Perhaps in a few decades, scientists will carefully study the mysterious exoplanet and (who knows?) will find signs of the existence of life on it.

The asteroid Apophis, potentially dangerous for the Earth, experiences the Yarkovsky effect, as a result of which it gains acceleration and shifts to more and more threatening orbits with a collision with the Earth.

The asteroid Apophis, 325 meters in size, was discovered in 2004. The discovery caused a stir – calculations showed that there is a 2.7 percent probability that Apophis, named after the ancient Egyptian god of evil and destruction, will collide with the Earth in 2029. Then scientists ruled out this threat, calculating that on April 13, 2029, the asteroid will fly at a distance of 37.6 thousand kilometers from the center of the Earth.

The report on the detected displacement was presented at the Planetological Section of the Virtual Meeting of the American Astronomical Society in 2020 by a specialist from the Institute of Astronomy, University of Hawaii, Dave Tholen. According to the speaker and his colleagues, the asteroid Apophis is strongly susceptible to the Yarkovsky effect, which consists in a weak force effect on an object moving in space due to the inhomogeneity of thermal radiation.

All asteroids emit in the form of heat the energy of the sunlight they absorb in order to remain in a state of thermal equilibrium – and as a result of this process, the asteroid’s orbit changes weakly. Until now, it was believed that collisions of the asteroid Apophis during its approach to Earth in 2029 and 2068 are impossible. Taking into account the Yarkovsky effect with respect to a 325-meter potentially dangerous asteroid means that the scenario of its collision with the Earth in 2068 is updated again.

Apophis is the most likely candidate for a collision from the aton asteroids passing near the Earth, was discovered in 2004 and received its own name on July 19, 2005 in honor of the ancient Egyptian god Apop (Apophis) – a huge destroyer snake living in the darkness of the underworld and trying to destroy Sun (Ra).

During its approach to Earth on Friday, April 13, 2029, this asteroid will be visible to the naked eye as it passes within the orbits of Earth’s communications satellites.

One of the discoverers of Apophis, David Jay Tolen, in particular, said:

“We already know that the collision of this cosmic stone with our planet is impossible during the approach of 2029. However, the quality of our new observations with the Subaru telescope was high enough to reveal the acceleration resulting from the Yarkovsky effect on this asteroid.

Calculations have shown that the asteroid is annually displaced from a “purely gravitational” orbit by about 170 meters, and this displacement is enough to return the scenario of a collision with the Earth in 2068 among the probable outcomes .”

There are a number of services on Earth that track the potentially dangerous approaches of our planet with asteroids, but significant in body size, such as Apophis, attract the attention of scientists.